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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.

Mini RTD Pt100 Three Wire Transmitter

These are the circuits and boards of a Mini Temperature Transmitter for a Platinum hundred ohms temperature Sensor.

Transmitter RTD

The customer wanted a two wire system, this needs low power opamps which were ten times the price. If this transmitter works at 3mA it could have been two wire. Those parts were in short supply and the budget of customer was low. So i made it with regular opamps but three wire. The customer was satisfied as he got a cost effective solution. But now the situation of markets and products are different.

RTD  Three Wire Transmitter

If you need to transmit the temperature from a high voltage area or toxic environment. You will need to hermetically seal the transmitters, convert the Voltage to frequency, frequency to IR LED flashes or RF. This can be then remotely monitored. Then the transmitter has to be battery-solar operated, low power too. ICL7135 is a simple solution. It has a serial output that can be used to Drive IR Leds. Remotely sense these flashes in a Micro-controller and you have a reading. You may be able to use optic-fibers too. Where volatile liquids are present so that the risks of sparks can be eliminated.

3 Wire Transmitter RTD

More at Process Control Circuits

This is the same Mini RTD Pt-100 Transmitter but in its case. Encapsulated in epoxy, hermetically sealed against harsh industrial environment. This will work well even near fumes of Ammonia with no corrosion. But not near vapors which can be ignited by sparking as terminals are still open. The side view shows zero and full scale ten turn bourns trimpots heads, for calibration. After cal it can be sealed with RTV compound.

Hendon Semiconductors – Microelectronics Design

Products include integrated circuits (silicon chips) in Bipolar, Bi-CMOS and CMOS technologies, thick film hybrids (ceramic substrate) and surface mounted printed circuit board assemblies and modules.

Hendon Semiconductors – Microelectronics Design

History -“The Hendon business site in Adelaide, South Australia has been a long established integrated circuit design and wafer fabrication facility in Australia, from its Philips semiconductor background up to 1997…”

Hendon Semiconductors

Thick Film Hybrid Technology

The advantage of ceramic hybrids over fiberglass printed circuit is their high reliability due to their inherent rugged construction with the following advantages:

Hendon Semiconductors Pty. Ltd
ABN: 17 080 879 616, 1 Butler Drive, Hendon, South Australia 5014, Australia.

3-1/2 Digit ICL7107 DPM Digital Panel Meter

This is a Digital Panel Meter based on ICL7107. This was the workhorse Digital Readout chip before Low power uC designs were developed. Even now it is the easiest way an analog parameter can be displayed in an instrument.

Instrumentation and Measurement Circuits

3-1/2 Display is just enough resolution for recording process data or troubleshooting equipment. With 4-1/2 you notice the problems of thermoelectric EMF of probes and connectors. That is one reason gold plating is used another being low contact resistance. In 4 1/2 the reading can change due to contact resistance too, if the input impedance of the analog signal conditioning is low or the protection diodes, RC filter caps are leaky.

ICL7107 DPM Digital Panel Meter

When you measure an analog parameter from a sensor; you attenuate or amplify it, to scale to the A/D converter range. You also need to protect or isolate the analog front end from high energy mis-connections, which will happen during field use. The operator should not get injured from any high energy leakage while measuring.

Resolution is the finest detail you can enumerate in a parameter or object. You can say the crowd was 3000 or 4000 people. Here 1000 is the resolution, finer data does not matter here. You would also hear things like, there were 80 to 90 boys in that classroom. 10 is the resolution there.

Accuracy is how precise a statement or number is. If there was 85 boys in that class, the above statement is accurate. If there was 65 boys, the measuring method or process needs calibration or examination.

In this circuit, the plastic caps should be of very low leakage. Multilayer plastic caps are good for instrumentation.

The MOSFET in Power Electronics

delabs Notes – In a Circuit Module, if all Power and Signal Polarities are reversed. All NPN to PNP, All N-Channel to P-Channel and Vice Versa. All Diodes and Caps too turned around. This Topsy Turvy or Mirror Design ought to work in Theory. It has worked for some circuits in practice too in my experience. ?

Some believe that N-Channel is more Robust than the P Type. In Bipolar Transistor NPN is more trusted for the final output stages. The NPN Transistor and N-Channel turn-on by a Positive control bias. It may be inappropriate to say this mosfet is NPN or PNP.

The MOSFET in Power Electronics

The traditional metal–oxide–semiconductor (MOS) structure is obtained by growing a layer of silicon dioxide (SiO2) on top of a silicon substrate and depositing a layer of metal or polycrystalline silicon (the latter is commonly used). As the silicon dioxide is a dielectric material, its structure is equivalent to a planar capacitor, with one of the electrodes replaced by a semiconductor.

If the MOSFET is an n-channel or nMOS FET, then the source and drain are “n+” regions and the body is a “p” region. If the MOSFET is a p-channel or pMOS FET, then the source and drain are “p+” regions and the body is a “n” region. The source is so named because it is the source of the charge carriers (electrons for n-channel, holes for p-channel) that flow through the channel; similarly, the drain is where the charge carriers leave the channel. MOSFET – Wikipedia

This application note discusses the breakdown voltage, on-resistance, transconductance, threshold voltage, diode forward voltage, power dissipation, dynamic characteristics, gate charge and dV/dt capability of the power MOSFET.
Application Note AN-1084 Power MOSFET Basics – IRF

A MOSFET is a transistor. It is a Metal Oxide Field Effect Transistor. Here are the symbols for FETs and MOSFETs: The MOSFET How the MOSFET works

The conductivity of the path from Source to drain is controlled by applying a voltage between the gate and the body of the semiconductor. N-channel enhancement MOSFET

See this simple circuit that explains everything
n-channel MOSFET switch – George Watson, Univ. of Delaware, 1996.

Clean Rooms and Electronics

Clean rooms and Dust free environment is a must for Precision Mechanical Engineering. It is not MEMS or nano sizes, even micron sizes accuracy in parts can be affected by Dust and Humidity.

In Electronics, Timepiece Manufacturing, Medical Equipment and Scientific Apparatus companies. Clan Rooms ensure long term reliability and safety of the products not to forget Precision.

EE Design Library – Electronic Product Design Resource.

Even if a Place is partially Dust free, it is better to have all objects with the least surface area. The way Motors are designed, Interiors of houses even a Machine

Clan Rooms and Electronics

You can enclose objects with many contours and unclean-able surfaces within a Spherical or Cubical Transparent Cover, this is easy for inspection and cleaning.

Dust, Oil, Sand and Humidity makes Grime. Never allow Rodents and Roaches in the Workplace they are larger than 100 microns.

Resources – Electronic Firms and Electronic Projects.

Tools and Equipment must be maintained free of rust/corrosion and exposure to brine or chemical fumes. Metal tools must be cleaned, oiled and stored in dry places when not in use.