SG2525 – SG3525 – PWM SMPS Regulator Chip

SG2525 – SG3525 – PWM SMPS Regulator Chip. A second generation ic switch mode controller optimized for high frequency.

100kHz Half Bridge Convertor – SG3525

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.

SG3525 usage in SMPS 500W – It was used in Parallel for Electroplating with a central Load sharing control between modules.

SG2525 - SG3525 - PWM SMPS Regulator Chip


  • 8.0 V to 35 V Operation
  • 5.1 V +/- 1.0% Trimmed Reference
  • 100 Hz to 400 kHz Oscillator Range
  • Separate Oscillator Sync Pin
  • Adjustable Deadtime Control
  • Input Undervoltage Lockout
  • Latching PWM to Prevent Multiple Pulses
  • Pulse-by-Pulse Shutdown
  • Dual Source/Sink Outputs: +/- 400 mA Peak

Circuits –

Power Electronics Section

Here are power supply, inverter, drives, chargers and high current equipment diagrams and links. There are Mosfet and Thyristor circuits too.

Power Electronics Section

Power Supplies, Inverters, UPS, Chargers, Electro Plating, Precision Welding-erosion, Coating Metals and many other Processes are made of high current circuits. Even in measurement of parameters like Micro-Ohm high currents are involved. Electronic Circuits are required in such products to give control to time, current, frequency and voltage in order to accomplish with the required precision a process or job.

Power Electronics Section - delabs
In any power equipment, efficiency and reduction of bulk is crucial so SMPS and high frequency control is an important part of this domain. These products also generate EMI-RFI. Product Safety Study is also vital.

The Power Circuits Section has been updated.

Power Electronics Design Methods

I first saw this practically in the Orthodox Cherokee SMPS. This is where we differentiate from Engineered Products and just Mass Production without following standards. The Cherokee SMPS was a work of art, perfect in all respects.

The Copper Desert or Isolation Land

There is a No Man’s Land in PCB. Any good power electronics designer should/will know. Product Safety and HV Isolation, Quality and Reliability all depend on this.

High Energy Circuits

Power Electronics Design Methods

These things don’t come overnight, it is a culture, learning, experience and integrity of some of these American Firms. Reliability and Product safety are important. Every human values his life very much. A manufacturer too should appreciate this.

Coming back to isolation, Keep in mind creepage distance, High energy circuits and Low voltage circuits should have clear isolation, use the best insulation. Fire and shock hazard. Mains HV transitions, spikes.

Regulated High Voltage Power Supply

Power supply faces all these, even other areas where a Human Life or Property can be endangered.

HV High Voltage Reliability and Safety

Use a Servo Stabilizer or CVT Constant Voltage Transformer or at least an Isolation Transformer. The First Defense form HV Surges, Spikes.

High Voltage Polyester & Polypropylene Metallized Capacitors in Stepdown Supplies should be Fire Retardant & Self Healing with a MOV too.

TDK Lambda – SMPS UPS Power Supply Specialist

Switching power supplies are power supplies switched by high-speed semiconductor switches. They are the most common type of compact, lightweight, high-efficiency power supply.

TDK Lambda – SMPS UPS Power Supply Specialist

Uninterruptible power systems (UPS) are backup power supplies that use a built-in battery to stably supply continuous clean power to connected devices when the regular supply power shuts down due to a power failure or other power problem. TDK-Lambda offers both these types of power supplies”.

CME150-24 TDK Lambda

CME150-24 – Single output AC-DC converter 150 – TDK Lambda

Output voltage of 24V at Max output current of 6.3A and Efficiency of 82%

Features Include

  • Leakage current 0.3mA or less (at 265VAC)
  • Medical safety standard (IEC60601-1) approved.
  • Max output power 151.2W
  • Input voltage range AC 85 – 265 V
  • Input voltage range DC 120 – 370 V
  • Input frequency 47 – 63 Hz

Murata Power Solutions – DC-DC Converters

Murata Power Solutions – DC-DC Converters Murata Power Solutions - DC-DC Converters

“On September 4, 2007 Murata completed its acquisition of the Power Electronics Division of C&D Technologies, making us the world’s number one supplier of DC/DC Converters and the fifth largest supplier of power overall. Going forward, the Power Electronics Division will be known as Murata Power Solutions.”

“ manufacturer of dc-dc converters, ac-dc power, military power supplies, digital panel meters, magnetics, data acquisition devices and contract electronics manufacturing (CEM) services…”

( C&D Technologies was Datel GE )

  • Process Monitors
  • Daylight Readable and Auto-Dimming
  • Digital-to-Analog Converters
  • 200-2000 Watt Front-End Power Supplies

delabs Notes

How i remember Datel was from the A/D Converters and Analog Mux they made of very low on resistance and crosstalk. It was part of GE at that time, like Intersil. I was an R&D Engineer for an Industrial Instrumentation Company. It must have been the time when 8031/51 was getting very popular.

100kHz Half Bridge Convertor – SG3525

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 SG2525 – SG3525 – PWM SMPS Regulator Chip.

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!!

100kHz Half Bridge Convertor - SG3525

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 AntiphaseTRX2 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 PhillipsTRX3 Current Feedback Trx
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 FilterPCB Layout

The PCB of module will be added later, if i locate it. It is small and be designed easily.

Simple WorkBench Dual Power Supply

I will just explain part of this circuit. D9 and D10 provide a low cost -1.4 from -5 V. This is needed to reach near 0.00 for LM317 Min. setting. An LED also can be used with proper bias. Note that there is a Temperature Coefficient in ppm, see The Unusual Diode FAQ. but it may not matter upto 8 bits accuracy.

TIP2955 PDF, TIP3055 (NPN), TIP2955 (PNP) Complementary Silicon Power Transistors. It is a Darlington, that means good current gain. See Darlington transistor – Wikipedia. When current in R1 10E goes more than 50mA a voltage of 50mA X 10E = 500mV is applied across Emmiter-Base junction. So lower than 500mV no bias the tap is turned off, 500mV-700mV the tap starts turning on depending on type of transistor. The transistor is like a water Tap. So TIP2955 carries the major current burden thru the load allowing LM317 to do the decision making when to turn-on or off. It is analog control, it is not On-Off but linear-proportional. The LM317 is very cool as the burden is passed off to TIP2955 who will need a heatsink to keep going and deliver the power you want.

WorkBench Dual Power Supply

Put the filter caps appropriately. The Hum-Noise will be filtered. The cap after the regulator should be a small guy. The main filter cap after the Bridge can be as big as your cabinet or budget.

If you build it and wire it without designing a PCB, then make all wiring and connection very sound. The test of this ability you can know easily, If your project stops working after the last screw of the cabinet is tightened, Then we need to improve.