100kHz Half Bridge Convertor SG3525 - del50032
This is a SMPS Circuit improved over the Application Note in the
book SGS Motion Control Application Manual. This worked well. It
helps you learn more about High Frequency Power Supply Design.
Read about
SG3525
SMPS Regulator IC.
Some Notes Related to the Project
- In main circuit do not link different grounds.
- Main circuit can be used both for 110 AC and 230 AC
- Ferrites are partial conductors use proper insulation
before winding.
- For main transformer TRX2 use split bobbin for good/safe
isolation.
- Epoxy coated toroids have to be further insulated before
winding.
- Line of isolation between primary and secondary circuits
should be explicit.
- Primary components like Q1, Q2 tabs R5, R6 etc can give
shock take caution.
- Each main module is 500W and can be used in parallel for
more current.
- Q1 and Q2 should have appropriate isolated heatsinks TO220
type 50sq cm
- Schottky diodes D5, D6 should have heatsinks TO220 type
100sq cm.
- Diodes D5, D6 eg D83004 are TOP3 packages are used 2 in
parallel.
- For 200W and above R2=0.1e 5W in the main circuit fusible
ceramic.
- C10, C11... Add 4.7uF 100v more in parallel to reduce
ripple.
- C13, C14 can be 250V for better safety margin.
- TRX1 SEC1 and SEC2 dot polarity is anti-phase if same
phase danger!!
See a professional product here - High
Efficiency Step Down Isolated Supply
Schematic of Main Card
The SG3525A pulse width modulator control circuit offers
improved performance and lower external parts count when
implemented for controlling all types of switching power
supplies. The on-chip +5.1 V reference is trimmed to +/-1% and
the error amplifier has an input common-mode voltage range that
includes the reference voltage, thus eliminating the need for
external divider resistors. Half Bridge, Push-Pull.
This was the Module that contained the smps chip. It was done to
prevent easy replication by other firms. Alos to Keep the
Signals isolated from the Main board board currents and
Corrosion Prevention by impregnating Module in Epoxy. Yet the
main board suffered some corrosion even with some coating
protection.
Industrial Systems that involve processes like Etching, Coating
and Electroplating have to be well ventilated so that
electronics around them have some life. Else find ways to
package Electronics in Sealed Enclosures with a new plan for
Heat Dissipation.
Power
Supply Regulators and MOSFET Transistor
Schematic of Module

Magnetics Design
All Transformers Isolation 1kV PRI To SEC / SEC To SEC / PRI,SEC
To Core. Use Yellow Mylar Tape Insulation or better for all.
Vacuum Impregnate all Magnetics in Epoxy or Varnish. All Power
Tracks on PCB reinforce with Copper Braid.
TRX1 Mosfet Drive Transformer
T25.0 MGQ-5L Hitachi - Type Torroid - 100khz Signal
- PRI1 20 Turns #22 Awg
- SEC1 9 Turns #22 Awg
- SEC2 9 Turns #22 Awg
486T250-3C8 Ferroxcube - SEC1 And SEC2 Antiphase
TRX2 Stepdown Invertor
Transformer
EC52 Siemens/Hitachi - Can Be ETD/EER Cosmo Ferrites
- PRI1 22 Turns 2 Layers (44 Turns) - 2* #16 Awg(18 Swg) In
Parallel.
- SEC1 4 Turns Ct Copper Strap 0.01" * 0.8" Copper Strap
Coper Strap/Ribbon used, cause Hi-Freq Skin Effects, PRI 2 Wires
paralleled for same reason. EC52-3C8 Ferroxcube Phillips
TRX3 Current Feedback
Transformer
T25.0 MGQ-5L Hitachi - Type Torroid - 100khz Signal
- PRI1 1 Turn 4 Amps Max
- SEC1 20 Turns #22 Awg CT.
- Ceter Tap 10T-CT-10T
486T250-3C8 Ferroxcube
L1 Series 60A-80A Inductor
Type EC/ETD/EER EC42 Hitachi - Air Gap In Inductor Core Both
Sides 100khz Power IF30-3C8 Ferroxcube - 6 Turns 4*#12 AWG In
Parallel 4 Wires Of 12 AWG Twisted & Wound For 6 Turns (Use
Less AWG For Less I)
TRX5 50hz Transformer Small
- PRI1 & PRI2 115v
- SEC1 24V 0.2A
- JP2 2-3 Short 230V
- PRI1 & PRI2 In Parallel For 110V
- JP1 1-2 Short 230V 2-3 Short 110V
TRX4 - This is
A 10mH Common Mode Filter
Main PCB Layout
The PCB of module will be added later, if i locate it. It is
small and be designed easily.
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