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Power Supply Design Seminar

Topic Categories:

Design Reviews Full Power Supply

Power System Considerations

Reproduced from

2010 Texas Instruments Power Supply Design Seminar

SEM1900, Topic 7

TI Literature Number: SLUP267

2010, 2011 Texas Instruments Incorporated

Power Seminar topics and online power-

training modules are available at:

power.ti.com/seminars

Designing a Solar-Cell-Driven LED

Outdoor Lighting System


2/25Texas Instruments 1 SLUP267

Designing a Solar-Cell-Driven LED Outdoor

Lighting SystemRobert Kollman and John Betten

AbstrAct

A solar-powered LED light is an obvious application given the growing interest in green systems. This

topic will use a medium-power solution to illustrate the many considerations of designing a complete

system, including the unique demands of both the solar array and the LED lamps, and integrating these

with a storage battery, charger, and control circuitry. Both analog and digital power-control solutions will

be proposed and compared on the basis of functionality, complexity, and cost.

I. IntroductIon

With the growing interest in green systems,

the solar-powered light is gaining popularity.

Although many solar-powered lights are gridconnected, a number of applications such as venue

lighting, parks, and areas without grids use batteries

for energy storage during the day. As shown in

Fig. 1, a typical solar-powered system provides

three functions:

During the day, solar power is converted to

electricity with photovoltaic (PV) cells.

A battery charger replenishes a lead-acid battery

for energy use during the night.

LEDs are used to provide light during the

evening.

A small bias supply, which can run either from

the solar panel or the battery, is used to power the

control electronics.

Interestingly, a number of control loops exists

within this system. The most challenging is the

battery charger; it must determine the maximum

power point available from the solar panel. This is

a function of solar irradiance (incident solar energy)as well as temperature. The most cost-effective

way to achieve this is to use a microcontroller or

DSP. Once the choice to implement digital control

is made, it is possible to implement the entire

design with a single DSP.

II. specIfIcAtIonsAndrequIrements

The LED panels shown in Fig. 1 have two

identical drive circuits, each providing 12 W of

power to the LEDs. Two drive circuits were chosen

to reduce component size and minimize thermal

considerations. Two circuits also allow for the

possibility of lighting just a single string to

conserve power, or to lengthen run time without

Fig. 1. Solar-powered light block diagram.

PVSolarPanel

BatteryCharger

Lead-Acid

Battery

LEDDriver

LEDDriver

LEDPanel

LEDPanel

BiasPowerSupply

Control



circuit redesign. Additionally, software control

could program one string to logically shut down

based on battery life. Because the LEDs wereintended to illuminate a walkway or path, the

choice of 24 W was considered a good balance

between overall brightness and battery life.

Based on the 24-W LED driver load, battery

capacity can be determined. To draw 2 A (24 W/

12 V) from the battery for eight hours over three

days (with additional capacity due to poor weather),

then a battery with a minimum capacity of 48 Ah

is required. The MK 8A22NF Absorption Glass

Mat (AGM) battery with 63-Ah capacity (at a 100-

hour discharge rate) was chosen. AGM is a sealed,

lightweight, high-charge-efficiency battery with

performance characteristics similar to lead-acid

gel batteries. Lead-acid batteries were chosen

because of their low cost per Ah compared to other

chemistries.

Fig. 2 shows a graph of the recommended

bulk-charging voltage and float-voltage level, as

well as its high dependency on cell temperature.

Battery temperature monitoring is necessary to

assure proper charging levels. At 25C, a bulk-

charge voltage of 14.4 V and a float voltage of

13.4 V are recommended.

Table 1 shows how the battery state of charge

is nearly proportional to its open-circuit voltage.

This can be used to determine when the battery is

discharged and the LEDs should be turned off.

This cutoff level is somewhat flexible in that the

lower it is set, the longer the run time, but the

shorter the battery life.

A 50-W solar panel in full sunlight for five

hours a day can charge a 12-V battery with ahypothetical maximum of 250 Wh. The LEDs are

expected to consume 192 Wh per day, so a 50-W

solar panel can provide about 25% peak excess

capacity daily; not necessarily a lot of margin, but

still adequate for operation.

A Kyocera KC50 solar panel with the current/

voltage (I/V) characteristics shown in Fig. 3 was

selected. This panel is capable of sourcing just

slightly more than 3 A in full sunlight, but like the

batteries charging voltage, its voltage is also

highly temperature dependent. This will necessitatethe use of a pulse-width modulation (PWM) buck

converter that can operate near 100% efficiency to

fully utilize available power.

III. mAxImum-power-poInt

trAckIng

A simple power system that relies on the short-

circuit current limit of the solar module and does

not utilize an maximum-power-point tracking

(MPPT) algorithm, simply connects the modules

directly to the battery, forcing them to operate atbattery voltage. Almost invariably, battery voltage

is not the ideal value for harvesting the maximum

solar energy available.

Charge State

(%)

AGM/Gel Open-

Circuit Voltage

(V)

Flooded Open-

Circuit Voltage

(V)

100 12.8 12.6

75 12.6 12.4

50 12.3 12.225 12.0 12.0

0 11.8 11.8

tAble1. bAtterychArgestAte

VersustemperAture

3 0 2 0 01 0 10 20 30 40 50

Battery Cell Temperature(C)

BatteryVoltage

( V)

16.8

16.2

15.6

15.0

14.4

13.8

13.2

12.6

MaximumVoltage

Minimum

Voltage

Float Voltage

Fig. 2. AGM/gel charging voltage versus

temperature.



Fig. 4 shows the I/V characteristic for a typical

50-W solar panel and 25C cell temperature. The

dashed line is a plot of PV power against PV

voltage. The solid line plots PV current against PV

voltage. As shown in the graph, at 12 V, the output

power is about 36 W. In other words, by forcing

the PV-solar modules to operate at 12 V, power is

limited to about 36 W at peak irradiance.

With an MPPT algorithm implemented, the

situation changes dramatically. In this example,

the voltage at which the solar panel achieves

maximum power is 17 V. So the role of the MPPT

algorithm is to operate the solar panel at 17 V,thereby extracting the full 50 W, regardless of

battery voltage.

A high-efficiency DC-to-DC power converter

converts the 17-V PV voltage at the controller

input to battery voltage at the output. Because the

DC/DC converter steps the 17 V down to 13.8 V,

the battery charge current for the MPPT-enabled

system in this example would be:

PVPV

BAT

V 17I 4.1 A

V 12 = 2.9 = (1)

Assuming 100% conversion efficiency in the DC/

DC converter, the increase in available charge

current is 1.2 A; a 42% increase.

Although this example presumes that the

power system is handling the energy from a single

solar panel, conventional systems typically have

an array of panels connected to a single power

supply. This topology has both advantages and

disadvantages depending on the application.

There are three main types of MPPT algo-

rithms: perturb and observe (P&O), incremental

conductance (INC), and constant voltage. The

first two methods are often referred to as hill-

climbing methods because they depend on

the fact that when observing the power/voltage

characteristics of the solar-array, the curve to the

left of the maximum power point (MPP) is rising

(dP/dV > 0), and to the right side of the MPP, the

curve is falling (dP/dV < 0).

The P&O method is the most common. Thealgorithm perturbs the operating voltage in a given

Fig. 4. MPPT algorithms improve solar-system

power efficiency.

0 5 10 15 20 25

PV Voltage (V)

P

V

Current( A)

P

VPower(W)

3.5

3

2.5

2

1.5

1

0.5

0

70

60

50

40

30

20

10

0

PV Current

PV Power

Conventional ControllerExtracts 36 W at 12 V

MPPT OperationExtracts the

Full 50 W

0 10 20 30

PV Voltage (V)

PV

Current( A)

4

3

2

1

0

75C

50C

Irradiance = 1.51 kW/m2

25C

Fig. 3. Kyocera KC50 solar panel I/V characteristics.

1000 W/m2Irradiance =

800 /m2W

400 /m2W

200 /m2W

0 10 20 30

PV Voltage (V)

PV

Current( A)

4

3

2

1

0

600 /m2

W

Solar-Array Temperature = 25C



direction and samples dP/dV. If dP/dV is positive,

the algorithm knows to adjust the voltage in the

direction toward the MPP. It keeps adjusting the

voltage in that direction until dP/dV is negative.

P&O algorithms are easy to implement but

sometimes result in oscillations around the MPP in

steady-state operation. They also have slow response

times and can even track in the wrong directionunder rapidly changing atmospheric conditions.

The INC method uses the solar arrays incre-

mental conductance, dI/dV, to compute the sign of

dP/dV. INC circuitry tracks rapidly changing

irradiance conditions more accurately than P&O,

but like P&O it can produce oscillations and be

confused by rapidly changing atmospheric condi-

tions. Another disadvantage is that its increased

complexity increases computation time and slows

down the sampling frequency.

The third method, the constant-voltage method,makes use of the fact that, generally speaking, the

ratio of the PV voltage at MPP to the PV open-

circuit voltage is about 0.76. The problem with

this method is that it requires momentarily setting

the PV current to zero to measure the arrays open-

circuit voltage. The arrays operating voltage is

then set to 76% of this measured value. During the

time the array is disconnected, however, the

available energy is wasted. It has also been found

that although 76% of the open-circuit voltage is a

very good approximation, it does not alwaysrepresent the actual MPP voltage.

Because there is not a single MPPT algorithm

that successfully addresses all common-use

scenarios, many designers go the extra step of

having the system assess environmental conditions

and select the algorithm with the best fit. In fact,

many MPPT algorithms are available and it is not

uncommon for solar-panel manufacturers to

provide their own. See Reference [1] for further

discussion.

IV. bIAssupply

The requirements for the bias supply are shown

in Table 2. The specifications driving the topology

require an input that can be higher or lower than

the 12-V output but isolation is not needed. Two

topologies come to the forefront of the decision:

the single-ended primary-inductor converter

(SEPIC) and the flyback. The SEPIC has several

features that make it more attractive than a flyback.

It controls the ringing on the MOSFET switch and

output diodes to reduce electromagnetic

interference (EMI) and voltage stress. In manycases, this allows the use of lower-voltage parts,

which can cost less and may be more efficient.

Also, the SEPIC provides better cross regulation

in multiple-output converters, which may eliminate

the need for linear regulators.

On the downside, the SEPIC control character-

istics are not as well understood as the flyback but

choosing a reasonable frequency with a good

phase margin minimizes design problems.

Fig. 5 shows a SEPIC converter; it, like a

flyback, has a minimal parts count. Actually, thiscircuit would be a flyback if C1 were removed.

This capacitor is quite advantageous in that it

provides voltage clamping for the MOSFET switch

(Q1) and D1. When Q1 is turned on, the reverse

voltage on D1 is clamped by the capacitor through

Q1. When Q1 is turned off, the Q1-drain and

D1-anode voltage rises until D1 conducts. During

Q1 off time, the drain voltage is clamped by C1

through D1 and C2. As shown in Fig. 5, this

example has multiple outputs.

There is a constraint on the T1 winding ratios.The secondary winding connected to C1 must

have a 1:1 turns ratio to the primary. Any secondary

winding can be used providing it has a 1:1 ratio.

The circuit in Fig. 5 has been built and tested.

It was operated as a SEPIC with C1 in place and as

a flyback with C1 removed. Fig. 6 shows the Q1

voltage stresses in both operating modes.

Parameter Specifcation

Input Voltage 6 to 24 VDC

Output Voltage #1 12 V

Output Current #1 0.02 A

Output #1 Regulation 10%

Output Voltage #2* 5 V

Output Current #2* 0.2 A

Output #2 Regulation* 3%

Ripple 1%

Isolation Required? No

*A 5-V logic supply is not needed for an analog approach.

tAble2. bIAssupplyspecIfIcAtIons



In the flyback mode, the Q1 drain voltage went

to 40 V, while in the SEPIC mode, the drain

voltage was only 25 V. So the flyback design

would have to use a 40-V MOSFET, while the

SEPIC design could use 30-V parts. In addition,

the flyback high-frequency (>5-MHz) ringing

would be problematic for EMI filtering.

Cross regulation of the two circuits was

measured; the SEPIC had substantially better cross

regulation. In both, the 5-V output held at 5.05 V,

by the action of the feedback loop, while the loads

were varied from no load to full load and the input

voltage was set to 12 or 24 V. With no load on the

12-V output and full load on the 5-V output, the

12-V output of the SEPIC remained in a 10%

regulation band, whereas the flyback 12-V output

went to 30 V at high line input. Efficiency between

the two configurations was the same but wouldhave favored the SEPIC if power parts selection

had been consistent with voltage stresses.

To summarize, SEPICs are a valuable topology

for nonisolated power supplies. They clamp the

MOSFET voltage stress to a value equal to the

sum of the input and output voltages and eliminate

EMI seen in a flyback topology. The reduced volt-

age stress may allow the use of lower voltage parts,

Fig. 6. A SEPIC topology dramatically reduces EMI and voltage stress.

Time (1 s/div)

1

Q1 = 40 V (max)(10 V/div)

drain

Time (1 s/div)

1

Q1 = 25 V (max)(10 V/div)

drain

a. Flyback operation. b. SEPIC operation.

Fig. 5. A SEPIC converter makes an efficient bias supply.

C11 F 50 V

C9470 pF

C81 F

C31 F50 V

C101 F

C410 F

C210 F

C51 F

C11150 pF

C70.1 F

C6100 pF

11f = 200 kHzsw

+3.3 V

R7

0.1

R1

17.4 k

R4

15 k

R6

2.80 k

R51 k

R3

10

R2

191 k

TP1

D1ES1A

D2B140

T125 H

RC

SSDIS/ENCOMPFB

VDD

VBPGDRVISNSGND

12

345

109

876

U12TPS40210DGQ

PwPd

2 156

Q1Si3430DV

3

3

2

7

8

9

4

12 V at30 mA

3.3 V at36 mA

6 to 24 Vfrom Battery

or Solar Array



resulting in a more efficient and less costly supply.

And the reduced EMI will simplify the compliance

testing of the final product. Finally, using a SEPIC

topology in multiple-output supplies improves

cross regulation when compared to a flyback.

V. led drIVerpowerstAge

Table 3 lists the electrical requirements for theLED driver. Driving a string of LEDs for a constant

brightness requires a regulated current. For exam-

ple, a boost converter can be used to drive ten

LEDs in series with a regulated current of 350 mA.

Typically, the current in the string is regulated by

adding a sense resistor in series with the LEDs and

using the voltage across it as the feedback to a

PWM controller.

The controller shown in Fig. 7 is specifically

designed for LED applications by implementing a

reduced feedback voltage of 0.26 V. The reducedfeedback voltage reduces power loss in the LED

sense resistor and improves efficiency. A resistor

in series with the MOSFET switch (Q13) allows

current sensing for current-mode control, which

eases the task of stabilizing the closed-loop gain.

This circuit is designed to operate in continuous

conduction mode (CCM), meaning that Q13 drain

current never drops to zero before Q13 switches

on again. Since the LED load current is constant

and the batteries voltage range is rather limited,

the inductors minimum-to-maximum current

range will also be restricted. The inductors peak-

to-peak ripple current can be allowed a larger

swing and yet still maintain CCM operation. This

is beneficial in reducing the inductors value and

size. An efficiency of greater than 93% wasmeasured with a 12-V input.

The 47-V zener diode (D15) and 49.9-

resistor (R81) on the output forms an open-LED

protection circuit. This is a useful feature to add,

since the output voltage is regulated to a fixed

voltage in the event of an open LED. If an open-

LED fault occurs with any of the series LEDs or

Fig. 7. A boost converter regulates current in LEDs.

+C43330 F25 V

C463.3 F

50 V

C47DNP

C4410 F25 V

C520.1 F

C56100 pF

C530.1 F

C541 F

C55150 pF

C503300 pF

C49330 pF

11

f = 400 kHzsw

C4510 F25 V

9 to 17 VFrom Battery

or Solar Array

R83DNP

R91

0.0330.5 W

R86

10 k

R88

4.99 k

R82

0.75 R89

1 k

R85

402 k

R81

49.9

R803.0

TP14 TP15 TP16

TP20

TP17

D14

B2100

D1547 V

TP18

TP19

L247 H

RDSSDIS/ENCOMPFB

VDDVBP

GDRVISNSGND

123

45

1098

76

U12TPS40211DGQ

PwPd

LEDA

LEDC

10x LEDs35 V at 0.35 A

J61

2

321

Q13Si7850DP

4

5

Parameter Specifcation

Input Voltage 9 to 17 VDC

Maximum LED Current 0.35 A

Output Voltage 28 to 35 V

(10 LEDs in series)

Current Regulation 5%

LED Ripple Current 0.36 AP-P

Efciency 93%

tAble3. led drIVerspecIfIcAtIons.



their wiring, the voltage across R82 drops to zero.

The control circuit responds by increasing the

PWM ON time and boosts the output voltage

higher in an attempt to increase the LED current,

which it cannot. This can overstress or destroy the

output capacitors, diode D14, and/or MOSFET

Q13. In operation, as the output voltage rises, the

zener diode (D15) eventually conducts current to

ground, but through a much larger 49.9-current-

sense resistor (R81). This provides an alternate

feedback voltage that is no longer provided by the

LED current-sense resistor (R82). The converter

safely sources an output current of 5 mA and

clamps the output voltage to a predetermined safe

level.

The power stages for both the analog and

digital implementation of the boost converters are

nearly identical. But several modifications are

necessary for DSP control of the LED driver. TheTPS40211 controller is eliminated and replaced

with a simple MOSFET driver controlled directly

by the DSP. An external amplifier is necessary to

increase the small voltage available from the LED

current-sense resistor to approximately 3 V so that

the analog-to-digital converter (ADC) can provide

adequate resolution for feedback control. Voltage-

mode (VM) control is implemented because

monitoring the MOSFET current on a cycle-by-

cycle basis requires extremely high clock speeds

and ADC resolutions. Although operating in VMslightly increases control-loop complexity, it

eliminates a loss element and increases efficiency.

Compensation of the control loop is handled

digitally by software using Z-domain transfer

functions to maintain stability.

VI. bAtterychArgerAndcontrol

The LED load, including the LED driver

circuit(s), is switched on by applying a control

signal to a MOSFET in series with the battery.

When switched off, the load is isolated from the

battery and eliminates any leakage current that

may discharge the battery. The decision to apply

the control signal to turn on the LEDs is based ondiscrete inputs such as battery and solar-panel

voltage, as shown in Table 4 for Load Connect. To

connect the load, the battery must be in a charged

state with sufficient voltage and the solar-panel

output must be low, which mimics a nighttime

condition. There should be no overlap between

when the load is connected (LEDs on) and when

the battery is being charged by the solar panel.

With the LEDs on, the battery will begin to

discharge. The discharging battery voltage

provides a useful indication of the batteries stateof charge (Table 1). When the battery discharges

to a predetermined level, the logic turns off the

load with the assumption that the battery is drained

and should not be discharged further. The deeper

the battery is discharged, the shorter its life will

be. The designer must make a trade-off between

the total number of charge cycles and the depth of

discharge. In essence, a longer run time equals a

short battery life.

Charging a battery from the solar panel can

easily be accomplished with a simple diode. Butdoing so sacrifices power by lowering the panels

voltage to that of the battery, throwing away a

large percentage of the available power. This is not

desirable considering that solar-panel power is

Function Active Condition Inactive Condition Comment

Load Connect (LEDs On) VBAT> 12.5 V and

VPV

< 5 V

VBAT< 11.9 V or VPV> 10 V Switcher disabled when load

applied

Solar Panel Connect and Bulk-

Battery Charge

(VPV VBAT) > 3.4 V and

VBAT< 14.4 V

(VPV VBAT) < 0.7 V or

VBAT> 14.4 V

Panel power available,

battery OK to charge

Battery Trickle Charge VBAT> 14.4 V VBAT< 13.4 V Switcher disabled, trickle

charger on

Battery Low-Voltage Protection VBAT< 5 V VBAT> 5 V Switcher disabled

Battery Temperature Sensor Thermistor is open Thermistor < 500 k Switcher disabled, prevents

excessive bulk charge level

Battery Overvoltage Protection VCharge> 17 V VCharge< 15.4 V Disables trickle charger

tAble4. controllogIc



typically $5/W. It is highly beneficial to extractevery watt possible, which suggests that an MPPT

approach is desirable.The analog approach for MPPT uses a constant

voltage-tracking method with temperaturecompensation. The panel temperature is monitoredand the MPP voltage adjusts as the temperature

changes. Solar panels are highly temperaturedependent, so as the solar panel heats up, themaximum power point shifts to a much lowervoltage. To compensate for the lower temperatureand operate the solar panel at the MPP for optimum

efficiency, the switching regulator increases its

PWM duty cycle to draw more current from thesolar panel, thereby lowering the voltage.Conversely, lowering the current raises the solarpanel voltage. For example, if the solar-panel

output is currently 20 V and the target MPP at25C is 17 V, the current is increased until thesolar-panel voltage decreases. Because this is a

dynamic processakin to hitting a movingtargetthe control loop is constantly compensating

to maintain regulation at the MPP. A temperaturecompensation of 94 mV/C is necessary to

operate at the predicted MPP.Fig. 8 shows the power stage for the battery

charger. Current into the battery is measured bythe shunt-current monitor, R11 and U1. The U1output is used along with the solar-panel voltage

(or solar-panel error voltage in the analog design)to determine how to adjust the PWM duty cycle.

Voltage thresholds for connecting the solarpanel and bulk charging the battery are shown in

Table 4. Once the battery is sufficiently charged,bulk charging is terminated and trickle charging isinitiated. Several fault conditions are monitoredand protection circuits implemented, with levelsshown in Table 4. Battery temperature is measuredand the maximum charge voltage is adjusted by

4.7 mV/C/cell to help prevent overcharging.

OUTGNDV+IN

123

V+

VIN

5

4

C13.3 F50 V

C1310 F25 V

C12150 F50 V

C14

10 F25 V C1510 F25 V

R12100 k

R17

10 k

C80.01 F

R9

49.9

R8

49.9

R11

0.010

VControl

VBIAS

R3

2 k

R2

10 k

R4DNP

C60.1 F

D315 V

D515 V

U1INA194

3

3

2

2

1

1

L133 H

Q4Si7116DN

PWMControl

ChargerCurrent-Sense

Output

Lead-AcidBatteryV = 12 VBAT

J2

+

1

2

Reverse BatteryProtection

Q5SUD50P04-13L

Panel Disconnect

Q6Si7116DN

4

4

5

5

R1

100 kD1

15 V

SolarPanelV =12 to 30 V

PV

J11

2

Q2SUD50P04-13L

Q3BSS138

Q1SUD50P04-13L

Fig. 8. Battery charger power stage.



VII. dIgItAlcontroldescrIptIon

A controller for a regulated power supply can

be analog or digital. Traditionally, analog control-

lers have offered higher bandwidth and higher

resolution compared to digital controllers. With

digital controllers, on the other hand, designershave the flexibility to implement different control

algorithms and easily change output voltages and

supply behavior by changing software.

Digital MPPT uses actual voltage and current

readings and calculated power to set the operating

point. Eliminating the need for temperature com-

pensation for the solar panel, this approach is more

accurate than that used for the analog approach.

When designing a power supply with a digital

controller, one dilemma is to choose the right

digital controller. The choice is often between aMCU or a DSP. Each has its own benefits. MCUs

have fast interrupt response times and better

interrupt-handling capability, but lack the raw

computing power needed to execute complex

control algorithms. For example, a multiply

instruction commonly takes several cycles to

execute by a MCU, whereas with a DSP it takes

only a single cycle. Some DSPs however do not

have the interrupt-management infrastructure to

guarantee real-time responsiveness.

TIs new Piccolo microcontrollers have been

designed to combine the real-time capabilities and

power efficiency of traditional MCUs with the

high performance and math capability of a DSP.

Piccolo MCUs have the right mix of peripherals,and with a high-resolution PWM peripheral, can

be used in power supplies requiring higher

bandwidths and higher resolutions. The Piccolo

MCU has been designed to bring increased

capabilities in a small package to power-efficient

and cost-sensitive control applications. These

MCUs are based on TIs TMS320C2000 DSP

platform, specifically the TMS320F28x 32-bit

series (see Fig. 9).

Referring to Fig. 1, the power system employs

three control loops, system-level control, as wellas MPPT calculations. This places quite a burden

on the DSP, which is mitigated by a control law

accelerator. This 32-bit floating-point math

accelerator operates independently of the main

CPU (after initial configuration). It is designed to

run complex, high-speed control algorithms and

free the main CPU to handle I/O and feedback-

Serial Interfaces12-Bit, 13-/16-Ch,Up to 4.6-MSPS

ADC

ePWM x7(5 HR PWM+ 9 PWM)

Comparators(Up to 3x)

Analog ModulesTimer Modules

SPI x2

CAN

LIN

*Available on Piccolo F2803x Series

SCI

eQEP x1

eCAP x1

I C2

Peripherals

64- to128-KB

Flash

Dual Osc(10 MHz)

Power-On

Reset Brown-Out

Reset

3.3-VSupply

(On-Chip1.9 V)

20-KB RAM

Boot ROM

Real-Time JTAG

High-PerformanceC28x CPU

Control LawAccelerator

32-bit floating pointmath accelerator

Operates independentof C28x CPU

Up to 5x performanceboost

EnhancedArchitecture

IntelligentPeripherals

C28x 32-BitCPU

60-MHz32x32-Bit MultiplierRMW Atomic ALU

Control LawAccelerator*

Up to 60-MHzPerformance

Single-cycle 32-bit MAC

Fast interrupt responseand minimal latency

High-accuracyon-chip oscillators(10 MHz)

150-ps resolution onPWM frequency andduty cycle

12-bit ratio-metricADC with individualchannel triggers

Up to 3x analogcomparators with10-bit reference

Single 3.3-V supplywith BOR/PORsupervison

Memory

Debug

Power and Clocking

Peripheral Bus

Fig. 9. Piccolo MCUs offer a unique combination of performance and integration for real-time control.



loop metrics, resulting in as much as a 5x increase

in performance for common control-loop

applications.

PWM topology is an essential element in

controlling a switched-mode power supply. In

addition to frequency and duty-cycle control, other

control elements are dead band, rising- and falling-

edge control, and synchronization. In an analogPWM generator, changing these control elements

would mean redesigning the PWM generator. A

digital design, however, can take all these elements

into account because it is programmable. This

means power designers can tweak control require-

ments with software and not worry about changes

to the board.

Piccolo MCUs can have up to seven enhanced-

PWM (ePWM) modules. Each ePWM module can

have two outputs, with a dedicated 16-bit time-

base counter that offers frequency control. Themodules are programmable to provide phase-lead

or phase-lag with respect to each other. A dedicated

deadband generator is available with independent

falling- or rising-edge delay control. In high-

resolution PWM (HRPWM) mode, it is possible to

achieve resolutions of up to 150 ps, thus enabling

the usage of Piccolo MCUs in high-bandwidth

power supplies.

Monitoring power-supply parameters such as

voltage and current is required to regulate the

supply outputs. These parameters need to beconverted to digital domain using ADCs. The

Piccolo ADC module consists of 16 input channels

(0 to 3.3 V) with dual sample and hold, which

enables monitoring parameters for multiple power

stages. The converters 12-bit resolution is more

than sufficient for this application. The Piccolo

ADC peripheral is very flexible and is a complete

system in itself. Conversion can be started from

multiple triggers such as PWM signals, CPU

timers, or GPIO signals, and each channels sample

window can be programmed independently. Thisflexibility and configurability enables the

implementation of increasingly involved control

algorithms with Piccolo MCUs.

TIs Code Composer Studio software tool is

used to develop software for Piccolo MCUs. This

tool provides all of the necessary features of an

integrated development platform and can be used

for debugging and monitoring using real-time

watch windows and graphs. Writing software still

can be challenging, especially for power designers

that do not have firmware development back-grounds. To make this transition easier, a software

framework and power library for Piccolo MCUs is

available. The software framework is a simplified

way of implementing system software for any

type of control application. As shown in Fig. 10, it

divides system tasks into slow-running background

operations and fast-running interrupt service

routines (ISRs). A task state machine has already

been implemented as part of the background code

and tasks are arranged in groups (A1, A2, A3, ...,

B1, B2, B3, ..., C1, C2, C3, ...). These tasks can beused for slow background operations and even

communications. The fast ISR can be used to

execute tight control loops to guarantee real-time

responsiveness to the system.

The software framework takes care of all basic

device initialization operations and has the

necessary elements to provide for instrumentation

(like graphing data) and GUI control, which are

useful for debugging and demonstration purposes.

Thus the programmer does not need to worry

about execution-time guarantees for the ISRs.Implementing a state machine for slow background

tasks and device initialization is also taken care of

by the framework; this saves a lot of software-

development overhead. The programmer only needs

to decide what tasks need to be run and which

control algorithms to implement.

The power library provides the necessary

peripheral drivers (PWMs and ADCs) to drive

different power stages (buck drive, phase-shifted

full bridge, etc.) and math blocks (2P2Z, IIR filter,

etc.) to implement control loops. The librarymodules are available as macros that can be used

to implement a system by simply connecting them

through nets. This alleviates the burden of



configuring the peripherals and writing the basic

blocks for the control algorithm. Moreover, the

macros are written in a C-callable assembly fashion

that guarantees execution time and enables tight

control loops and real-time responsiveness.

As shown in Fig. 8, three power stages exist on

the battery-charger board. The buck power stage

controls the battery-charging operation, and twoboost stages control driving the LEDs. Thus, the

DSP needs to support three control loops. To

guarantee fast response times, the control loop for

the power stages needs to be run very fast.

Other operations include enabling/disabling

different power stages, system state determination,

MPPT generator (an MPPT algorithm is needed to

track the MPP from the solar array), a soft-start

mechanism is needed to ensure closed-loop

operation, GUI variable scaling for instrumenta-

tion purposes, and tuning the control loop (PID

coefficient tuning).The three major components of the system are:

1. Closed-loop buck.

2. Closed-loop boost.

3. Background operation (MPPT generator, soft

start, GUI scaling, state decision).

Initialization Execute Every IRS Call(Fast V or I )Loop Loop

Background Loop

Main ISR

TS1

Loop 1

TS2

Loop 2

TS2

Filtering

TS2

OVP Mgr

400 kHz

Return

Time-SliceManager

(100 kHz)

Device Level (CPU, PLL,...)

Peripheral Level (ADC, PWM...)

System Level (GPIO, Comms)

Framework (BG/ISR)

Interrupts

Startup/Shutdown/Sequencing

Margining

Diagnostics/Reporting/Comms

Fault Management

Slow Control Loops

Fig. 10. A slow background loop handles system functions.



Fig. 11 illustrates how these components can

be incorporated into the system framework

infrastructure. The fast control loops for the buck

and the boost stages are executed in the ISR,

which can be triggered by a PWM or other

peripherals. Other operations form the background

and can be divided as tasks in the task state

machine, which already exists in the system

framework.

To implement a closed-loop buck converter,

only three modules are required from the power

library: ADC_NchDRV, ControlLaw_2P2Z, and

BuckSingle_DRV. These modules execute as

in-line code (no decision making) within the ISR_

Run routine, which is triggered at the PWM rate.

The ADC_NchDRV macro reads the current ADC

results; the ControlLaw_2P2Z block then

calculates the error between system state (what is

observed by the ADC to what it should be[reference point]) and computes the new duty

cycle accordingly. The BuckSingle_DRV macro

updates the duty cycle of the PWM. This is

repeated for every ISR thus ensuring real-time

responsiveness of the power supply.

It is important for a power supply to have

proper start-up and shut-down routines. This is

managed by the soft-start and sequencing code,

which executes in the main background C code.

Also, to ensure closed-loop operation, the Vref is

kept at zero until a request is received to enable

the output voltages. This is also managed in the

background operations. Fig. 12 shows how the

macro blocks are used to make a closed voltage-

loop buck stage.

The voltage controller used in the system is

based on the ideal proportional-integral-derivative

(PID) controller, written in Laplace form as:

ip d

KG(s) K sK .

s= + + (2)

To implement this in the digital domain, a

discrete approximation by numerical integration is

used for integral and derivative terms. Using theEuler and trapezoidal approximation methods for

the derivative and the integral terms, the equation

in the z-domain can be written as:

p i d

T z 1 z 1G(z) K K K .

2 z 1 Tz

+ = + +

(3)

Soft Start

GUI VariableUpdate

Context

Save

ContextRestore

ISR Body

Background Loop(BG)

Interrupt ServiceRequest (ISR)

(100 kHz)

CNTL_2P2Z(3)

CNTL_2P2Z(1)

CNTL_2P2Z(2)

BUCK_DRV(3)

BUCK_DRV(1)

BUCK_DRV(2)

DriveChargingBuck Stage

DriveLoad 1Boost Stage

DriveLoad 2Boost StageMPPT

Generator

Get ADCResults

Charging

On/OffLED On/Off

ADC_DRV(N)

Fig. 11. System software tasks split into a slow background loop and the fast ISR.



Rearranging to express each term in the power

of z:

2 2 2p i d

2p i d

d

(2Tz 2Tz)G(z) z (2TK T K 2K )

z( 2TK T K 4K )

2K .

= + +

+ +

+

(4)

Redefining the controller gains as:

p p i i d d

T 1K K , K K , K K ,

2 T = = = (5)

the equation can be written as:

2 2p i d

p i d

d

(2Tz 2Tz)G(z) z (2TK 2TK 2TK )

z( 2TK 2TK 4TK )

2TK .

= + +

+ +

+

(6)

A common factor of 2T can be removed and the

equation rearranged to find the transfer function:

20 1 0

2

b z b z bG(z) ,

z z

+ +=

(7)

where

0 p i d

1 p i d

2 d

b K K K ,

b K K 2K , and

b K .

= + +

= +

=

The system uses the compensator block (macro),

ControlLaw_2P2Z to implement the PID voltage

controller. This block has two poles and two zeros

and is based on the general infinite-impulse-

response (IIR) filter structure. The transfer function

is then:

1 20 1 2

1 21 2

b b z b zU(z).

E(z) 1 a z a z

+ +=

+ + (8)

Comparing the IIR filter structure with the discrete

PID equation derived earlier, we can see that PID

is nothing but a special case of a 2-pole/2-zero

controller where a1= 1 and a

2= 0. Thus, even

though a 2-pole/2-zero controller is used, the more

intuitive coefficient gains of P, I, and D are used

for loop tuning, thus reducing the selection from

five degrees of freedom to just three. The P, I, and

D coefficients can be adjusted independently and

gradually through the Code Composer Studio

IDEs variable-watch window, with system

behavior tuned to get the desired results.

Fig. 12. Macros are configured to close the voltage-control loop.

TPS28225DVoltageController

VChrg

VChrg

VSolar

EPWM3A

Duty 1Vref

ChargerOutput

BuckDRV

Synchronous-BuckPower Stage

Current-Sense

Hardware

IChrg

PgainV

WatchWindow

Gui_VCharg

Gui_ICharg

Gui_VSolar

WatchWindow

IgainV

DgainV

WatchWindow

B2

B1

B0

A2

A1

Coefficient

Coefficient Tuning

ADC-B2

ADC-B1ADC-B2

VSolarFeedback

VSolar

ADC Hardware

BuckDriver

IN

ADCDriver

rslt1rslt0

PIDMapping(3 5)

CNTL_2P2Z

GUIScaling

(BG Task)

Vout

Soft Start

OutDelaySlopeTarget

Vsoft

SlewStep

OnDelay

OffDelay

RefFB

ePWM

Hardware



The LED drive circuit typically operates in

closed-loop current mode. Fig. 13 illustrates the

closed-current-loop boost stage, and how the nets

were connected to implement it. It is interesting to

note that this diagram is not much different from

the earlier closed-loop buck stage. Fig. 13 also

illustrates the reuse of the library macro blocks for

implementing different systems without muchchange to the software. Both average-mode and

peak-current-mode control can be implemented by

using the flexible ePWM and ADC peripherals in

Piccolo MCUs.

The background loop is used to carry out a

number of tasks that do not need to run as fast as

the control loop. A task state machine has already

been implemented as part of the background code;

tasks are arranged in groups (A1, A2, A3, , B1,

B2, B3, , C1, C2, C3, ). Each group is exe-

cuted according to three CPU timers, configuredwith periods of 1 ms, 5 ms, etc., depending on

requirements. Within each group (e.g., B), each

task is run in a round-robin manner. For exam-

ple, group B executes every 5 ms and there are

three tasks in group B. Therefore, each B task will

execute once every 15 ms. The different tasks for

the solar board have been split into various subtasks.

Determine the System State (ChargingOn/Off; LEDs On/Off)

Fig. 14 presents a high-level flow chart of the

overall power system. There are four basic system

states. One is lamp on/charger off. The other three

are combinations of lamp off with the charger on/

off, or with the charger in trickle-current mode.

All of these states correspond to switches on the

digital solar-power board, which can be controlled

through GPIOs. The lamp is on when there is very

little voltage from the solar panel but there is

sufficient voltage on the battery. This state could

include provisions to manipulate the discharge

characteristics to lengthen battery time. For

instance, the MCU could vary the PWM drive to

dim the LEDs as a function of battery voltage to

extend the battery run time. Dimming could also

be a function of time so that the light is brightest in

the early evening and dimmed later to provide just

a nightlight, or even vary dimming respective to

ambient light.

CurrentController

IBoost1

IBoost1

EPWM1A

Duty 1Iref

ChargerOutput

VLoad1

VLoad1

PgainI

WatchWindow

Gui_VL1

Gui_IBoost1

Gui_VLoad1

WatchWindow

IgainI

DgainI

WatchWindow

B2

B1

B0A2

A1

Coefficient

Coefficient Tuning

ADC-A0

ADC-A2ADC-A3

VL1Feedback

VLoad1Feedback

VL1

ADC Hardware

BuckDriver

IN

ADCDriver

rslt0

rslt1

PIDMapping(3 5)

CNTL_2P2Z

GUIScaling

(BG Task)

Iout

Soft Start

OutDelaySlopeTarget

IsoftSlewStep

OnDelay

OffDelay

RefFB

ePWMHardware

UCC27424D

Boost

DRV

Voltage-BoostPower Stage

Current-Sense

Hardware

Fig. 13. The boost implementation is similar to the closed-loop buck stage.



The LEDs will be turned off if the battery isdepleted to a 12.5-V lower limit, which can bemodified by the MCU. Hysteresis in the voltagetransition settings can be added, as well astemperature compensation. Once the solar-panel

voltage reaches an open-circuit voltage of 5 V, thesystem switches the light off. Charger operation

may begin when the solar-panel voltage hasexceeded the battery voltage. As the voltages fromthe panel and battery will change slowly over

time, this state determination can be kept in thebackground loop.

To make the system efficient, the battery currentmust be controlled so that the power extractedfrom the solar panel is maximized until the battery

is fully charged. The flow chart in Fig. 14 showstwo states: the first one regulates the battery currentto hold the power extracted from the solar panel at

maximum, and the second state occurs once thebattery has been charged. The flow chart shows

only a single voltage to declare a fully chargedbattery, but the MCU can compensate for temper-ature as well as provide hysteresis. Other featuresthat could be added with software include batterypreconditioning, data logging, and data transfer.

VIII. dIgItAlVersusAnAlog

compArIsons

In the digital implementation, much of thecontrol circuit was moved into the Piccolo MCU:the battery-charger PWM control, the MPPT gen-erator, the LED-driver PWM control, and overall

system management. Even with three control loopsin the system, the MCU was not significantlychallenged. Much more complicated systems arepossible.

There was one control loop that was not

brought into the MCUthe bias supply. It mayhave been possible, but it was felt that systemstart-up and fault conditions would be betterhandled with a separate bias supply.

A typical analog circuit board can have nearly

twice as many components as the digital approach,

mostly small resistors and capacitors around thecomparators and signal-conditioning circuits.These components take up considerable area, asan analog board can be more than twice the size of

a digital board. Although not factored into the bill-of-materials (BOM) cost, mounting these partscan add as much as $0.02 per component, furtherfavoring the digital design. Table 5 presents acomparison of analog and digital approaches.

Fig. 14. High-level flow chart.

Start

IsV > 5 V?Solar

IsV > 14.4 V?BAT

IsV >

V + 1?Solar

BAT

IsV > 12.5 V?BAT

Lamp Off,Charger Off

Lamp On,Charger Off

Lamp Off,Trickle On

Lamp Off,Charger On

No

No No

No

Yes

Yes

Yes

Yes

Return



Fig. 15 shows an older-generation analog boardthat is functionally similar to the optimized digitalboard on the right. The MCU represents almost20% of the cost of the digital board but simplifiesthe circuit implementation. Thus its BOM cost is

20% less than a comparable analog board. Thedigital approach is also much more flexible when

implementing changes to the operation of thesystem. Typically, a system change can involvesoftware changes only with no changes to the

physical hardware. Digital also offers the ability toincorporate many more features into the product.For instance, the MCU opens up the possibilityfor adjusting light levels in changing ambient andbattery conditions, as well as data logging, failure

prediction, and diagnostics. However, with theMCU comes the need to develop software. SeeAppendix A for schematic comparisons of analog

and digital lighting systems and Appendix B forthe bill of materials.

Software development can be perceived as aserious cost and risk addition to any developmenteffort and may be so for the near future with digitalpower control. However, controller developers arecontinuing to develop new tools with enhanced

GUIs and software modules that are easily adapt-able to reduce software-development risks.

Todays digital power-control projects mayrequire two types of designers: one that under-

stands the power-supply specifications, compo-nent selection, and testing requirements, and a

second one familiar with digital signal processing

and firmware development. This project was agood example: the power experts developed therequirements, power stages, and signal-conditioning circuits, while the digital signal-processing experts (David Figoli and Manish

Bhardwaj) developed the code and eventuallymade the whole project work.Many graduate programs for power design areincluding microcontroller, digital signal processing,and FPGA development in their labs and classes.

Ix. reference

[1] Roberto Faranda and Sonia Leva, Energy

Comparison of MPPT Techniques for PVSystems, WSEAS Transactions on PowerSystems, Vol. 3, No. 6, p. 446, June 2008.

Parameter Analog Digital

Component Count 312 148

Board Area 18.2 in2 8.8 in2

BOM Cost $14 $12

MPPT Method Voltage regulation Multiple

Flexibility Poor Good

Data Logging None Yes

Software Development None Yes

tAble5. dIgItAlpreVAIlsInAll

butsoftwAredeVelopment

Fig. 15. The digital board on the right is more compact than the analog board.



AppendIxA. compArIsonofsolAr-poweredlIghtIngsystems

+

+

++ +

+

Analog-Control Power Switching and Battery Charger

Digital-Control Power Switching and Battery Charger




Analog Control

Digital Control DSP




Analog-Control LED Drivers

Digital-Control LED Drivers

+

+




Analog-Control Bias Supply

Digital-Control Bias Supply



AppendIxb. solAr-poweredlIghtIngsystembIllofmAterIAls

Analog Lighting System

Count RefDes Value Description Size Part Number MFR

3 C1, C46, C61 3.3uF Capacitor, Ceramic, 50V, X7R, 15% 1210 C3225X7R1H335K TKD

4 C10, C56, C69, C76 100pF Capacitor, Ceramic, 50V, COG, 5% 0603 Std TDK

1 C11 0.22uF Capacitor, Ceramic, 16V, X7R, 15% 0603 Std TDK

7 C13, C14, C15, C44, C45, C59, C60 10uF Capacitor, Ceramic, 25V, X7R, 15% 1210 C3225X7R1E106K TKD

17C16, C18, C19, C26, C27, C28,

C30, C33, C35, C39, C40, C51,1uF Capacitor, Ceramic, 16V, X7R, 15% 0603 Std TDK

2 C17, C79 470pF Capacitor, Ceramic, 50V, X7R, 15% 0603 Std TDK

5 C2, C3, C4, C5, C12 150uF Capacitor, Alum, 0.979Arms, 0.061 Ohms 0.492 inch 50VZL150uF20%10X12.5 Rubycon

3 C20, C22, C29 DNP Capacitor, Ceramic, 50V, X7R, 10% 0603 Std Std

1 C21 33pF Capacitor, Ceramic, 50V, X7R, 15% 0603 Std Std3 C24, C50, C64 3300pF Capacitor, Ceramic, 50V, X7R, 10% 0603 Std TDK

1 C34 DNP Capacitor, Ceramic, 16V, X7R, 15% 1206 TDK

2 C43, C58 330uF Capacitor, Aluminum, 25V, 90-milliohms, 20% 0.200 inch Dia. EEU-FC1E331 Panasonic

2 C47, C62 DNP Capacitor, Ceramic, 50V, X7R, 10% 1210 TDK

2 C49, C63 330pF Capacitor, Ceramic, 50V, X7R, 10% 0603 Std TDK

3 C55, C68, C81 150pF Capacitor, Ceramic, 50V, X7R, 15% 0603 Std TDK

15C6, C23, C31, C32, C36, C37, C38,

C41, C42, C48, C52, C53, C65,0.1uF Capacitor, Ceramic, 25V, X7R, 10% 0603 Std Std

3 C7, C71, C73 1uF Capacitor, Ceramic, 50V, X7R, 15% 1206 C3216X7R1H105KT TDK

2 C72, C74 10uF Capacitor, Ceramic, 16V, X7R, 15% 1206 C3216X7R1C106KT TDK

4 C8, C9, C57, C70 0.01uF Capacitor, Ceramic, 50V, X7R, 10% 0603 Std TDK

4 D1, D3, D5, D7 15V Diode, Zener, 15V, 0.5W SOD-323 MMSZ5245BT1 On Semi

2 D11, D22 6.8V Diode, Zener, 6.8V, 0.5W SOD-323 MMSZ5235BT1 On Semi

2 D14, D17 B2100 Diode, Schottky, 2A, 100V SMB B2100 OnSemi

2 D15, D18 47V Diode, Zener, 47V, 0.5W SOD-323 MMSZ5261BT1 On Semi

2 D16, D19 MMBD7000 Diode, Dual Switching, Series, 200mA, 100V, 225mW SOT23 MMBD7000 Diodes

2 D2, D24 BAV70 Diode, Switching, Dual, 70V, 300mA SOT23 BAV70 Diodes Inc.

1 D20 ES1A Diode, Super Fast Rectifier, 100V, 1A SMA ES1A Diodes Inc.

1 D21 B140 Diode, Schottky, 1A, 40V SMA B140 Diodes Inc.

1 D23 12V Diode, Zener, 12V, 0.5W SOD-323 MMSZ5242BT1 On Semi

6 D4, D8, D9, D10, D12, D13 BAS16 Diode, Switching, 200mA, 75V, 350mW SOT23 BAS16 Diodes Inc.

1 D6 DNP Diode, Schottky, 3A, 40V SMC MBRS340 Fairchild

7 J1, J2, J3, J4, J5, J6, J8 ED555/2DS Terminal Block, 2-pin, 6-A, 3.5mm 0.27 x 0.25 inch ED555/2DS OST

2 J7, J9 PTC36SAAN Header, Male 2-pin, 100mil spacing, (36-pin strip) 0.100 inch x 2 PTC36SAAN Sullins

4 JP1, JP2, JP3, JP4 923345-02-C Jumper, 0.2 length AWG 22 " 0.035 inch Dia.

1 L1 33uH Inductor, SMT, 4.8A, 48.8 milliohms 0.543 x 0.516 inch HC9-330-R Cooper

2 L2, L3 10uH Inductor, SMT Dual Winding, 7.1A, 12.94-milliohm 0.492 sq" 7447709100 Wurth

4 Q1, Q2, Q5, Q7 SUD50P04-13L MOSFET, P-ch, 40V, 13 milliohms DPAK SUD50P04-13L Vishay

2 Q13, Q15 Si7850DP MOSFET, N-Chl, 60V, 10.3 A, 22 millohm PWRPAK S0-8 Si7850DP Vishay

1 Q19 Si3430DV MOSFET, N-ch, 100V, 2.4A, 170 milliOhms TSOP-6 Si3430DV Vishay

9 Q3, Q8, Q10, Q11, Q12, Q14, Q16, 2N7002 MOSFET, N-ch, 60-V, 115-mA, 1.2-Ohms SOT23 2N7002W Diodes Inc.

2 Q4, Q6 Si7116DN MOSFET, N-Ch, 40V, 16.4A, 7.8millohm PWRPAK 1212 Si7116DN Vishay

1 Q9 MMBT3906 Bipolar, PNP, 40V, 200mA, 225mW SOT23 MMBT3906LT1 On Semi

3 R1, R12, R25 100K Resistor, Chip, 1/16-W, 1% 0603 Std Std

3 R10, R65, R120 15K Resistor, Chip, 1/16W, 1% 0603 Std Std

1 R11 0.025 Resistor, Metal Strip, 1 W, 1% 2512 Std Std

1 R110 249K Resistor, Chip, 1/16W, 1% 0603 Std Std



1 R122 4.64K Resistor, Chip, 1/16W, 1% 0603 Std Std

1 R123 1 Resistor, Chip, 1/16W, 1% 0805 Std Std

5 R15, R111, R112, R114, R117 DNP Resistor, Chip, 1/16W, 1% 0603 Std Std

10R17, R28, R40, R42, R44, R87,

R94, R102, R109, R11310K Resistor, Chip, 1/16-W, 1% 0603 Std Std

3 R2, R86, R101 10K Resistor, Chip, 1/16W, 1% 0805 Std Std

18R20, R27, R29, R32, R35, R43,

R46, R49, R55, R60, R67, R71,49.9K Resistor, Chip, 1/16-W, 1% 0603 Std Std

1 R24 274 Resistor, Chip, 1/16-W, 1% 0603 Std Std

1 R26 4.02K Resistor, Chip, 1/16-W, 1% 0603 Std Std

1 R3 2K Resistor, 2K Ohm, 1/4 watt, 5% 1206 Std Std

2 R30, R36 2.61K Resistor, Chip, 1/16-W, 1% 0603 Std Std




6 R4, R22, R31, R33, R38, R53 DNP Resistor, Chip, 1/16-W, 1% 0603 Std Std1 R41 100 Resistor, Metal Strip, 1 W, 1% 2512 Std Std

8 R45, R47, R48, R59, R62, R66, 24.9K Resistor, Chip, 1/16-W, 1% 0603 Std Std

2 R5, R119 10 Resistor, Chip, 1/16W, 1% 0603 Std Std

3 R50, R69, R74 1M Resistor, Chip, 1/16-W, 1% 0603 Std Std


1 R52 357K Resistor, Chip, 1/16-W, 1% 0603 Std Std

3 R54, R88, R103 4.99K Resistor, Chip, 1/16-W, 1% 0603 Std Std



1 R58 100 Resistor, Chip, 1/16-W, 1% 0603 Std Std




1 R64 432K Resistor, Chip, 1/16-W, 1% 0603 Std Std


5 R7, R13, R16, R18, R19 0 Resistor, Chip, 1%, 0603 0603 Std Std


5 R77, R84, R92, R99, R107 45.3K Resistor, Chip, 1/16-W, 1% 0603 Std Std

7 R8, R9, R21, R23, R81, R96, R115 49.9 Resistor, Chip, 1/16-W, 1% 0603 Std Std

2 R80, R95 3 Resistor, Chip, 1/16W, 1% 0603 STD STD

2 R82, R97 0.75 Resistor, 0.25W, 1% 1206 Std Std

2 R83, R98 DNP Resistor, 0.25W, 1% 1206 Std Std

2 R85, R100 402K Resistor, Chip, 1/16W, 1% 0603 STD STD

3 R89, R104, R121 1K Resistor, Chip, 1/16W, 1% 0603 STD STD

2 R90, R105 16.2K Resistor, Chip, 1/16W, 1% 0603 STD STD

2 R91, R106 0.015 Resistor, Chip, 1W, 1% 2512 STD STD

2 RT1, RT2 10K Thermistor, 0.236 X 0.512 inch B57153-S479-M Thermometrics1 T1 1.5mH Transformer, SEPIC, 1.5mH 13.50 X 17.50 mm G095013LF GCI

26

TP1, TP3, TP4, TP5, TP8, TP9,

TP10, TP11, TP12, TP14, TP15,

TP16, TP17, TP18, TP19, TP21,5000 Test Point, Red, Thru Hole Color Keyed 0.1 x 0.1"" 5000 Keystone

8 TP2, TP6, TP7, TP13, TP20, TP27, 5001 Test Point, Black, Thru Hole Color Keyed 0.1 x 0.1"" 5001 Keystone

3 TP28, TP29, TP30 5000 Test Point, Red, Thru Hole Color Keyed 0.100 x 0.100 inch 5000 Keystone

1 U1 INA194 IC, High-Side Current Shunt Monitor, G=50 SOT23-5 INA194AIDBV Texas Instruments

2 U12, U14 TPS40211DGQ IC, 4.5V-52V I/P, Current Mode Boost Controller DGQ10 TPS40211DGQ TI

2 U2, U15 TPS40210DGQ IC, 4.5V-52V I/P, Current Mode Boost Controller DGQ10 TPS40210DGQ TI

1 U3 TPS28225D IC, High Freq 4-Amp Sink Sync Buck MOSFET Driver SO8 TPS28225D TI

2 U4, U13 LM258AD IC, Dual Operational Amplifiers SO-8 LM258AD TI

2 U5, U9 TL431DBZ IC, Precision Adjustable Shunt Regulator SOT23-3 TL431AIDBZ TI

4 U7, U8, U10, U11 LM293AD IC, Dual Differential Comparators, 2-36 Vin SO-8 LM293AD TI

Notes: 1. These assemblies are ESD sensitive, ESD precautions shall be observed.

2. These assemblies must be clean and free from flux and all contaminants.

Use of no clean flux is not acceptable.

3. These assemblies must comply with workmanship standards IPC-A-610 Class 2.

4. Ref designators marked with an asterisk ('**') cannot be substituted.

All other components can be substituted with equivalent MFG's components.



AppendIxb. solAr-poweredlIghtIngsystembIllofmAterIAls

Digital Lighting System

Count RefDes Value Description Size Part Number MFR

3 C1, C46, C61 3.3uF Capacitor, Ceramic, 50V, X7R, 15% 1210 C3225X7R1H335K TKD


1 C12 150uF Capacitor, Alum, 0.979Arms, 0.061 Ohms 0.492 inch 50VZL150uF20%10X12.5 Rubycon

7C13, C14, C15, C44, C45,

C59, C6010uF Capacitor, Ceramic, 25V, X7R, 15% 1210 C3225X7R1E106K TKD

9C19, C20, C75, C78, C80,

C83, C84, C87, C881uF Capacitor, Ceramic, 16V, X7R, 15% 0603 Std TDK

1 C51 1u Capacitor, Ceramic, 50V 1206 C3216JB1H474KB TDK

3 C6, C32, C77 0.1uF Capacitor, Ceramic, 25V, X7R, 10% 0603 Std Std

2 C71, C73 1uF Capacitor, Ceramic, 50V, X7R, 15% 1206 C3216X7R1H105KT TDK

2 C72, C74 10uF Capacitor, Ceramic, 16V, X7R, 15% 1206 C3216X7R1C106KT TDK

1 C76 100pF Capacitor, Ceramic, 50V, COG, 5% 0603 Std TDK

1 C79 470pF Capacitor, Ceramic, 50V, X7R, 15% 0603 Std TDK


1 C81 150pF Capacitor, Ceramic, 50V, X7R, 15% 0603 Std TDK

4 D1, D3, D5, D7 15V Diode, Zener, 15V, 0.5W SOD-323 MMSZ5245BT1 On Semi

2 D14, D17 B2100 Diode, Schottky, 2A, 100V SMB B2100 OnSemi

2 D15, D18 47V Diode, Zener, 47V, 0.5W SOD-323 MMSZ5261BT1 On Semi

2 D2, D24 BAV70 Diode, Switching, Dual, 70V, 300mA SOT23 BAV70 Diodes Inc.

1 D20 ES1A Diode, Super Fast Rectifier, 100V, 1A SMA ES1A Diodes Inc.

1 D21 B140 Diode, Schottky, 1A, 40V SMA B140 Diodes Inc.

1 D22 6.8V Diode, Zener, 6.8V, 0.5W SOD-323 MMSZ5235BT1 On Semi

1 D23 12V Diode, Zener, 12V, 0.5W SOD-323 MMSZ5242BT1 On Semi

1 D4 4.7V Diode, Zener, 15V, 0.5W SOD-323 MMSZ5245BT1 On Semi

1 D6 DNP Diode, Schottky, 3A, 40V SMC MBRS340 Fairchild

3 D8, D9, D10 BAS16 Diode, Switching, 200mA, 75V, 350mW SOT23 BAS16 Diodes Inc.

5 J1, J2, J3, J6, J8 ED555/2DS Terminal Block, 2-pin, 6-A, 3.5mm 0.27 x 0.25 inch ED555/2DS OST

2 JP1, JP2 923345-02-C Jumper, 0.2 length AWG 22 " 0.035 inch Dia.

1 L1 33uH Inductor, SMT, 4.8A, 48.8 milliohms 0.543 x 0.516 inch HC9-330-R Cooper

2 L2, L3 47uH Inductor, SMT, 2-A, 100-milliohm 0.484 x 0.484 inch MSS1278-473X_ Coilcraft

4 Q1, Q2, Q5, Q7 SUD50P04-13L MOSFET, P-ch, 40V, 13 milliohms DPAK SUD50P04-13L Vishay

2 Q13, Q15 Si7850DP MOSFET, N-Chl, 60V, 10.3 A, 22 millohm PWRPAK S0-8 Si7850DP Vishay

2 Q17, Q18 2N7002 MOSFET, N-ch, 60-V, 115-mA, 1.2-Ohms SOT23 2N7002W Diodes Inc.1 Q19 Si3430DV MOSFET, N-ch, 100V, 2.4A, 170 milliOhms TSOP-6 Si3430DV Vishay

3 Q3, Q8, Q10 BSS138 MOSFET, N-ch, 50-V, 22-mA, 3.5-Ohms SOT23 2N7002W Diodes Inc.

2 Q4, Q6 Si7116DN MOSFET, N-Ch, 40V, 16.4A, 7.8millohm PWRPAK 1212 Si7116DN Vishay

1 Q9 MMBT3906 Bipolar, PNP, 40V, 200mA, 225mW SOT23 MMBT3906LT1 On Semi

8R1, R4, R5, R12, R14, R15,

R19, R25100K Resistor, Chip, 1/16-W, 1% 0603 Std Std

3 R10, R16, R20 11.0K Resistor, Chip, 1/16-W, 1% 0603 Std Std

1 R11 0.01 Resistor, Metal Strip, 1 W, 1% 2512 Std Std




1 R119 10 Resistor, Chip, 1/16W, 1% 0603 Std Std




1 R123 0.1 Resistor, Chip, 1/16W, 1% 0805 Std Std

2 R128, R130 100K Resistor, Chip, 1/16W, x% 0805 Std Std

2 R129, R131 5.23K Resistor, Chip, 1/16W, 1% 0603 Std Std

8R17, R28, R40, R42, R44,

R45, R46, R11310K Resistor, Chip, 1/16-W, 1% 0603 Std Std


2 R21, R22 DNP Resistor, Chip, 1/16-W, 1% 0603 Std Std

2 R26, R27 3.32K Resistor, Chip, 1/16-W, 1% 0603 Std Std

1 R3 2K Resistor, 2K Ohm, 1/4 watt, 5% 1206 Std Std

1 R39 49.9K Resistor, Chip, 1/16-W, 1% 0603 Std Std1 R41 100 Resistor, Metal Strip, 1 W, 1% 2512 Std Std

1 R43 100 Resistor, Chip, 1/16W, x% 0603 Std Std


2 R61, R62 100K Resistor, Metal Film, 1/4 watt, 5% 1206 Std Std

2 R63, R64 10.0K Resistor, Chip, 1/16W, x% 0603 Std Std

2 R66, R67 30.1K Resistor, Chip, 1/16W, x% 0603 Std Std

3 R7, R13, R18 0 Resistor, Chip, 1%, 0603 0603 Std Std

4 R8, R9, R81, R96 49.9 Resistor, Chip, 1/16-W, 1% 0603 Std Std

2 R80, R95 3 Resistor, Chip, 1/16W, 1% 0603 STD STD

2 R82, R97 0.75 Resistor, 0.25W, 1% 1206 Std Std

1 T1 1.5mH Transformer, SEPIC, 1.5mH 13.50 X 17.50 mm G095013LF GCI

6TP3, TP20, TP21, TP27,

TP38, TP395000 Test Point, Red, Thru Hole Color Keyed 0.1 x 0.1"" 5000 Keystone

1 TP37 5001 Test Point, Black, Thru Hole Color Keyed 0.1 x 0.1"" 5001 Keystone

1 U1 INA194 IC, High-Side Current Shunt Monitor, G=50 SOT23-5 INA194AIDBV Texas Instruments

1 U15 TPS40210DGQ IC, 4.5V-52V I/P, Current Mode Boost Controller DGQ10 TPS40210DGQ TI

1 U2 TMS320F2802xPTA IC, 32-Bit Piccolo Microcontrollers, xx MHz LQFP TMS320F2802xPTA TI

1 U3 TPS28225D IC, High Frequency 4-Amp Sink Sync Buck MOSFET Driver SO8 TPS28225D TI

1 U7 UCC27424DIC, Dual Non-Inverting 4A High Speed Low-Side MOSFET

Driver w/ EnableSO8 UCC27424D TI

1 U8 LM258AD IC, Dual Operational Amplifiers SO-8 LM258AD TI

Notes: 1. These assemblies are ESD sensitive, ESD precautions shall be observed.

2. These assemblies must be clean and free from flux and all contaminants.

Use of no clean flux is not acceptable.3. These assemblies must comply with workmanship standards IPC-A-610 Class 2.

4. Ref designators marked with an asterisk ('**') cannot be substituted.

All other components can be substituted with equivalent MFG's components.


24/25

TI Worldwide Technical Support

Internet

TI Semiconductor Product Information CenterHome Pagesupport.ti.com

TI E2E Community Home Pagee2e.ti.com

Product Information CentersAmericas Phone +1(972) 644-5580

Brazil Phone 0800-891-2616

Mexico Phone 0800-670-7544

Fax +1(972) 927-6377

Internet/Email support.ti.com/sc/pic/americas.htm

Europe, Middle East, and Africa

Phone

European Free Call 00800-ASK-TEXAS(00800 275 83927)

International +49 (0) 8161 80 2121

Russian Support +7 (4) 95 98 10 701

Note:The European Free Call (Toll Free) number is not activein all countries. If you have technical difficulty calling the freecall number, please use the international number above.

Fax +(49) (0) 8161 80 2045

Internet support.ti.com/sc/pic/euro.htm

Direct Email [email protected]

Japan

Phone Domestic 0120-92-3326

Fax International +81-3-3344-5317

Domestic 0120-81-0036Internet/Email International support.ti.com/sc/pic/japan.htm

Domestic www.tij.co.jp/pic

Asia

Phone

International +91-80-41381665

Domestic Toll-Free Number Note:Toll-free numbers do not support

mobile and IP phones.

Australia 1-800-999-084

China 800-820-8682

Hong Kong 800-96-5941

India 1-800-425-7888

Indonesia 001-803-8861-1006

Korea 080-551-2804

Malaysia 1-800-80-3973

New Zealand 0800-446-934

Philippines 1-800-765-7404 Singapore 800-886-1028

Taiwan 0800-006800

Thailand 001-800-886-0010

Fax +8621-23073686

Email [email protected] or [email protected]

Internet support.ti.com/sc/pic/asia.htm

A122010

Important Notice:The products and ser vices of Texas InstrumentsIncorporated and its subsidiaries described herein are sold subject to TIsstandard terms and conditions of sale. Customers are advised to obtain themost current and complete information about TI products and services beforeplacing orders. TI assumes no liability for applications assistance, customersapplications or product designs, software performance, or infringement of

patents. The publication of information regarding any other companys productsor services does not constitute TIs approval, warranty or endorsement thereof.

The platform bar, C28x, Code Composer Studio, ControlSuite, E2E, Piccolo and

TMS320C2000 are trademarks of Texas Instruments. All other trademarks are the

property of their respective owners.

SLUP267


25/25

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,and other changes to its products and services at any time and to discontinue any product or service without notice. Customers shouldobtain the latest relevant information before placing orders and should verify that such information is current and complete. All products aresold subject to TIs terms and conditions of sale supplied at the time of order acknowledgment.

TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI s standardwarranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where

mandated by government requirements, testing of all parameters of each product is not necessarily performed.

TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products andapplications using TI components. To minimize the risks associated with customer products and applications, customers should provideadequate design and operating safeguards.

TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Informationpublished by TI regarding third-party products or services does not constitute a license from TI to use such products or services or awarranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectualproperty of the third party, or a license from TI under the patents or other intellectual property of TI.

Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompaniedby all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptivebusiness practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additionalrestrictions.

Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids allexpress and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not

responsible or liable for any such statements.TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonablybe expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governingsuch use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, andacknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their productsand any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may beprovided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products insuch safety-critical applications.

TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products arespecifically designated by TI as military-grade or "enhanced plastic."Only products designated by TI as military-grade meet militaryspecifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely atthe Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.

TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products aredesignated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designatedproducts in automotive applications, TI will not be responsible for any failure to meet such requirements.

Following are URLs where you can obtain information on other Texas Instruments products and application solutions:

Products Applications

Audio www.ti.com/audio Communications and Telecom www.ti.com/communications

Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers

Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps

DLPProducts www.dlp.com Energy and Lighting www.ti.com/energy

DSP dsp.ti.com Industrial www.ti.com/industrial

Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical

Interface interface.ti.com Security www.ti.com/security

Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense

Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive

Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video

RFID www.ti-rfid.comOMAP Mobile Processors www.ti.com/omap

Wireless Connectivity www.ti.com/wirelessconnectivity

TI E2E Community Home Page e2e.ti.com

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265Copyright 2011, Texas Instruments Incorporated
http://www.ti.com/audiohttp://www.ti.com/communicationshttp://amplifier.ti.com/http://www.ti.com/computershttp://dataconverter.ti.com/http://www.ti.com/consumer-appshttp://www.dlp.com/http://www.ti.com/energyhttp://dsp.ti.com/http://www.ti.com/industrialhttp://www.ti.com/clockshttp://www.ti.com/medicalhttp://interface.ti.com/http://www.ti.com/securityhttp://logic.ti.com/http://www.ti.com/space-avionics-defensehttp://power.ti.com/http://www.ti.com/automotivehttp://microcontroller.ti.com/http://www.ti.com/videohttp://www.ti-rfid.com/http://www.ti.com/omaphttp://www.ti.com/wirelessconnectivityhttp://e2e.ti.com/http://e2e.ti.com/http://www.ti.com/wirelessconnectivityhttp://www.ti.com/omaphttp://www.ti-rfid.com/http://www.ti.com/videohttp://microcontroller.ti.com/http://www.ti.com/automotivehttp://power.ti.com/http://www.ti.com/space-avionics-defensehttp://logic.ti.com/http://www.ti.com/securityhttp://interface.ti.com/http://www.ti.com/medicalhttp://www.ti.com/clockshttp://www.ti.com/industrialhttp://dsp.ti.com/http://www.ti.com/energyhttp://www.dlp.com/http://www.ti.com/consumer-appshttp://dataconverter.ti.com/http://www.ti.com/computershttp://amplifier.ti.com/http://www.ti.com/communicationshttp://www.ti.com/audio

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