This document describes a power supply/battery charger with a full bridge resonant converter. The charger has an output of 26.4VDC at 33A maximum. It operates in constant current and constant voltage modes with protections against overvoltage, overtemperature, and undervoltage. The charger uses a pulse width modulated full bridge converter with a power factor correction boost converter on the input side and a full bridge ZVS resonant converter on the output side. Key components and operations of the power factor correction, DC-DC conversion, output rectification, and control sections are explained.
1. Power Supply/Battery Charger with Full
Bridge Resonant Converter
CWID – A20259141
Deshpande Prathamesh Arun
Professor
Alireza Khaligh
2. 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.
3. Specifications of Battery Charger
Voltage = 26.4VDC
Boost = 27.2 VDC
Current = 33A max
Output Characteristics – CC,CV
Ripple = 1% peak to peak of output max
Protections – Electronic Turn OFF in case of Over Voltage or
Over temperature. Alarm for Under Voltage through relay.
Input Voltage = 176-264 VAC
Power Factor = 0.98 at full load and nominal input
Switching Frequency = 100KHz
Isolations – Input to Ground as well as output to ground.
4. Overview Of the Charger
There are following sections in this supply /Charger-
Input Filters and Bridge
Power Factor Corrector Section
DC to DC Converter Section
Output Rectifier Section
Other Supporting Circuits
6. 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.
9. Waveforms in PFC
Primary MosFET Switching Waveform
Input Voltage and Current Waveform
Ch 1 = Voltage
Ch 2 = Current
10. Equations for Boost Converter
Boost Converter has 2 modes for continuous
conduction mode - when switching Device is ON and
device is OFF
11. Current shaping in CCM with reference
CCM Power Shaping I/P Current Shaping in PFC
12. 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.
13. 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.
19. Output Rectifier and Control Section
This 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.
20. 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.
21. Safety Mechanisms in Charger
To 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.
22. 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.
23. 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.
24. 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.
