Post on 02-Dec-2015
transcript
Power Supply Topologies
Switching Waveforms
Ajit & Arash
POWER SUPPLY TOPOLOGIES
There are several power supply topologies including Buck, Boost, Buck Boost(inverting), Sepic , Flyback , Forward, Active Clamp Forward, and half bridge to name a few.
In the next few slides few of the most popular topologies are reviewed and examples from WEBENCH are provided
Buck
Circuit Configurationtest
DT
t
Vin
Vout
p
ON
Drain Current
Ideal Transfer Function)1(1 DII outD
outQ II (max)1
VinVDS
Drain Voltage
Ave. Diode Current
Diode Reverse Voltage
VinVD 1
Buck
• Voltage and Current Waveforms
Buck Topology ExampleVin = 12.5 V, Vout = 5V, Iout = 0.5A , IC = LM2842Y
Output voltage
Buck TopologyVin = 12.5 V, Vout = 5V, Iout = 0.5A , IC = LM2842Y
Switch current
Inductor current and Diode current
Switch node voltage
Boost
Circuit Configurationtest
DtT
T
Vin
Vout
ONp
p
1
1
Drain Current
Ideal Transfer Function
outD II 1
DII outQ
1
1(max)1
outDS VV
Drain Voltage
Ave. Diode Current
Diode Reverse Voltage
outD VV 1
Boost
• Voltage and Current Waveforms
Boost Topology Example
Vout = 30V in steady state
Vin = 12.5 V, Vout = 30V, Iout = 3A , IC = LM3478
Boost Topology - waveforms
Inductor current
Diode current
Switch node voltage
Switch current
Buck Boost
Circuit Configurationtest
D
D
tT
t
Vin
Vout
ONp
ON
1
Drain Current
Ideal Transfer Function
outD II 1
DII outQ
1
1(max)1
outinDS VVV
Drain Voltage
Ave. Diode Current
Diode Reverse Voltage
outinD VVV 1
Buck Boost
• Voltage and Current Waveforms
Buck-Boost example Vin = 16, Vout = 12V, Iout = 3A , IC = LM5118-Q1
Output voltage
Buck-Boost Topology Vin = 16 V, Vout = 12V, Iout = 3A , IC = LM5118-Q1
Inductor current Switch node voltage
SEPIC
Circuit Configurationtest
D
D
Vin
Vout
1
Drain Current
Ideal Transfer Function
outD II 1
D
DII outQ
1
(max)1
outinDS VVV
Drain Voltage
Ave. Diode Current
Diode Reverse Voltage
outinD VVV 1
SEPIC
• Voltage and Current Waveforms
SEPIC Example Vin = 17.5 V, Vout = 12V, Iout = 0.5A , IC = LM3478
Output voltage (Vout)
SEPIC Topology Vin = 17.5 V, Vout = 12V, Iout = 0.5A , IC = LM3478
Inductor current and Switch current Switch node voltage (Vsw)
FLYBACK
Circuit Configurationtest
pout
p
LI
VoutTD
Vin
Vout
2
Drain Current
Ideal Transfer Function
outD II 1
p
ONQ L
tVinI
(max)1
s
poutinDS N
NVVV
Drain Voltage
Ave. Diode Current
Diode Reverse Voltage
s
pINoutD N
NVVV 1
FLYBACK
• Voltage and Current Waveforms
Flyback exampleVin = 5 V, Vout = 12V, Iout = 0.5A , IC = LM2587
Output voltage (Vout)
Flyback exampleVin = 5 V, Vout = 12V, Iout = 0.5A , IC = LM2587
MOSFET current (ISwitch )( same as Transformer primary current, Ipri)Secondary Diode current (ID1)Load current (Iout)
MOS Drain voltage (Vswitch)