Power Supply/Battery Charger with Full Bridge Resonant Converter

CWID – A20259141Deshpande Prathamesh Arun

ProfessorAlireza Khaligh

Some Characteristics of Power Supply/ Battery Charger

Pulse Width Modulated Full Bridge DC Power Supply Variable Input Voltage Possible with range of 176 VAC- 264 VAC

and 47Hz-63HZ. Output Voltage 26.4VDC float and 27.2VDC boost (fixed), with

maximum 33A Current. Operates in CC and CV Mode. Various Protections and Alarms against abnormal conditions. Possibility to monitor current and voltage on front panel, as well

as status of battery charging.

Specifications of Battery ChargerVoltage = 26.4VDCBoost = 27.2 VDCCurrent = 33A maxOutput Characteristics – CC,CVRipple = 1% peak to peak of output maxProtections – Electronic Turn OFF in case of Over

Voltage or Over temperature. Alarm for Under Voltage through relay.

Input Voltage = 176-264 VACPower Factor = 0.98 at full load and nominal inputSwitching Frequency = 100KHzIsolations – Input to Ground as well as output to

ground.

Overview Of the ChargerThere are following sections in this supply

/Charger-

Input Filters and BridgePower Factor Corrector SectionDC to DC Converter SectionOutput Rectifier SectionOther Supporting Circuits

Block Diagram of the Power Supply/Charger

Power Factor Corrector Section

Basic functions of this section are

Using Boost Converter Topology, create a fixed voltage DC Bus for DC-DC Converter Section.

Using the controller IC, correct the shape of input current waveform, and thus retain the Power Factor near unity at any condition.

*We are going to use IR1150IS PFC Controller for current waveform correction as well as generation of gate drive pulse for PFC Switching Device.

Circuit Diagram of Boost Converter

Circuit Diagram of PFC Controller

Waveforms in PFC

Primary MosFET Switching Waveform

Input Voltage and Current Waveform

Ch 1 = VoltageCh 2 = Current

Equations for Boost ConverterBoost Converter has 2 modes for continuous

conduction mode - when switching Device is ON and device is OFF

Current shaping in CCM with reference

CCM Power Shaping I/P Current Shaping in PFC

DC-DC Converter Section

Topology Selector

Why Full Bridge ZVS Resonant Converter Circuit? It is Recommended to follow the algorithm to design the topology for power supply.

As our charger has output voltage of 26.4V and max current of 33A, the total power of the charger goes around 900W approx, which recommends us to select the topology stated above.

DC-DC Converter Section

Functions of this section are as follows

Generation of the takeover control supply.Generation of the control signal for the main

bridge converter.Correct the phase of the drive signal with the

feedback from the output.Using the full bridge topology, pass the input

voltage to the transformer for step down.Protect the power circuitry from abnormal

conditions.

Algorithm for Topology Selector

Actual Circuit Diagram of DC-DC Converter.

Simplified Circuit Diagram of DC-DC Converter.

Equations for the topologyWhen Either of the switch pair is ON then

Therefore Inductor Voltage

Thus

Equation for Output Current

WaveformsOutput Voltage seen across switch pairs

Output Rectifier and Control SectionThis Section has following functions - Rectification of Output of DC-DC Converter,

and fix the output voltage using feedback loop.

Using Shunt amplifier, control the CV and CC mode for the Charger.

Shift the charger from float to boost mode using current sensing.

Electronic Shutdown and alarm indication in case of abnormal conditions, e.g. Over-Voltage, Under-Voltage, Over-Temperature.

Other Supporting Circuits

There are other circuits which will help the user to know the condition of battery charger. These include –

Battery Status Monitoring Section – this section when activated, shuts down the charger, draw current from the battery connected and display the status of the charging (Low, Mid, Full)

Digital Panel Meter Section – this section takes references from output voltage and current and display the magnitude on the front panel using 7 segment display and ADC Controller.

Safety Mechanisms in ChargerTo Protect the Charger as well as connected Load, we

have introduced few safety circuits in the charger, these include

1.Output Overvoltage Shutdown – in case the feedback loop gets open, and output goes above fixed value, then charger shuts down automatically.

2.Output Under-voltage Alarm – In any condition, when Output of charger goes below 85% of the fixed value, then a relay will operate, to which any kind of warning system can be connected.

3.Over-temperature trip – If charger temperature goes above 95C, then electronic shutdown will take place.

Safety Mechanisms in Charger

for battery Status Monitoring Section, we have introduced a fuse in positive path of the input sense connectors.

Digital Panel Meter Section is given regulated Power Supply from voltage regulators.

To protect overall charger from Dust and Water, IP65 construction is recommended.

Economic Aspect

Cost of the Charger is approx 12000 INR (US$240)

The cost depends upon type of construction, for civil application with IP5x its lower.

However with IP6x it is going to get higher, up to 2 times than in IP5x.

Applications

This charger is used basically to Charge Lead Acid Batteries. Particularly with voltage 24V and current 330Ah.

Such Batteries are used in Lifting Systems such as Forks and Cranes where this charger can be installed on the same vehicle.

Changing the Construction Types, we can use it in Marine and Defense Applications too.

End of Presentation

Thank You !!!

Questions ?