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.

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.

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.

PC User Interface and Wireless Power

Wireless Charging is a Reality today, it was first conceived by me in the 90s. The first page published related to that in my netscape site.

This was conceived to get rid of cables for data and power on my desktop. I felt if we use Optics for Data and Wireless Ferrite Contact Plates to transfer power, there would be no wires at all on the desk. I even experimented with RS232 Serial Port and Ferrite Slices below thin Acrylic Plastic Sheet, it worked.

I did not patent any of my concepts, but it is offered to all humanity as an Open Design, like all my other work.

Here is a planar transformer which has PCB tracks for winding. This show that there is more scope of innovation in such ferrite transformers for short range wireless power.

PC User Interface and Wireless Power

Objects kept on a electromagnetic table must be able to draw energy from that. A Notebook or tablet can be just placed on this table to get charged.

The optic ball-less mouse is a great step in mice-tech user-interface. This mouse consumes more power, for a wireless mouse a capacitive sensor matrix based sensing may be better.

Touch Screen on PC is not common place. A combination of Touch screen and Mouse is excellent for all age-groups. Large monitors can have at least two inches of touch screen area at bottom.

Laptops, LCD Monitors make UPS (Uninterrupted Power Supply) last longer and it reduces electricity costs.

Wireless Power for Wireless Peripherals

Wireless Mouse with capacitive sensors may consume less power, no batteries works on a Supercap, Connector-less ferrite dock for recharging

Wireless mouse rechargeable battery can recharge while moving on the Mouse Pad made of Ferrite/Ceramic 1? Sq with Power Hot Spots every 3?

Flexible Ferrite, Silicone & Ferrite based Solid emulsion. Can be made as computer table mats to charge the supercaps of peripherals.

The Energy Efficient Wireless Peripherals can just be placed on this mat to draw the power without wires. Wireless power and Wireless Data.

Usability and Ergonomics Review
Aggregated Notes from 2008-12

Usability and Ergonomics of Electronic Consumer Equipment, product risks and safety are best studied with very old and very young people.

Optical Rotary Encoders, Magnetic/Eddy/Capacitive/Hall Effect based Non-Contact Joysticks, Makes Human An analog Interface with Digital Output.

For the people who type with two fingers; A Circular Keyboard is right. A Capacitive Touch Gesture Pad can replace the Mouse. Health & Ergo.

Personal Computers, Netbooks, Portable Communicating Devices, Remote Controls are where Usability Issues abound, and can be studied/remedied

delabs – 2009

Desktop Power Supply Immunity

Make the desktop architecture like laptop with regards to Power Electronics. I think now RAM’s consume lower power. So every Desktop can come with a Li-ion Backpack based on some standard. 10Ahr 12V Rechargeable Battery. The entire Motherboard works on the 12V DC supply that uses Float Charging from mains.

Power Electronics & Solar Energy

The supply to computer is always derived from battery, the battery being constantly replenished. The charger also supplies power to computer board over the battery itself. Many lighting/inverter systems use this. The SMPS now is only a intelligent charger. Other voltage levels with DC/DC converters from that 12V.

Desktop Power Supply Immunity

Advantage –

1 – A user can easily upgrade the 12 V bus, another 12 V battery with smart charger; gives a boost of backup time. Probably intelligent batteries can come with built in float chargers, so that they can they can be bussed to form a 12v Tiny power grid for home which includes solar cells.

2 – When just the backpack is used, power fails. Harddisk, Monitor etc. sent to standby, low power mode. CPU then goes to quiescent state. The RAM keeps all data intact but goes to a low power mode. Alternatively quickly write a RAM image on a Flash Layer Built over RAM.

This makes the PC Impervious to Power Supply or UPS or other problems. Moves the desktop system to a 12 V standard. Drives desktop PC development to more Power Efficient designs.

Switching Supplies and SMPS

Easy integration into automobiles, bus, etc which have DC grid. Remote areas where no power is there. This will ensure desktops have a role in the future.

The charger SMPS has 1A charging current for Battery and 3A max for Computer. Total 4A max. A SuperCap can be added parallel to the Battery for Extra Inertia.

When power fails, in few seconds the system goes to standby. No program need to be closed. When power is restored they system comes up with windows and programs in the same positions of the last frozen state.

When a UPS is used, the system does not go down at all. The UPS just consists of a 10A Charger and a 12V 20AHr Battery. If the house has a 24V DC bus which is battery supported too. Then this can be used. As 24V is being developed as a new standard for internal power distribution. EMerge Alliance. The PCs also can move to this manageable and safe standard for homes.

delabs – 2010

Constant LED Brightness and LDS8711

The LDS8711 is a fixed frequency current mode boost converter with internal rectifier and cycle-by- cycle switch current limit specifically designed to drive a string of up to 10 White LEDs.

Constant LED Brightness and LDS8711

Aa Switching Converter Chip with hardly any external components driving a HB LED chain. HB – High Brightness LED. This IC is from IXYS Power Devices.

High efficiency boost converter with the input voltage range from 2.7 to 5.5 V . Drives one LED string with 10 LEDs in series up to 32 mA.

  • 250 mV current sense voltage
  • No external Schottky Required
  • 0.7 MHz Switching Frequency
  • Efficiency greater than 83%
  • PWM LED Brightness Control
  • Low Shutdown Current (<1µA)

LED Current Setting – The maximum current value in the LED string may be factory preset in the range from 10 to 30mAin 0.125mA steps, or set by Smart OneWire interface in the range from 0.125to 32 mA.The average LED string current that determines LED brightness may be controlled applying PWM signal to the EN/PWM pin.