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Switching Supplies and SMPS

Circuits of SMPS, Power Supply, Switch Mode Power Supply are here. High Voltage Power Supply concept. DC Regulated 3 Pin Power Supplies like 7812 and 7805. Workbench Supplies. 

Here is a Powerful SMPS i built STMicro Power Chip - 100kHz Half Bridge Convertor - SG3525

The documentation may not be perfect. Use it for study and design your own.  These were made for custom solutions and even as products.

Some Simple Switchers 5V -1A Power Supply using LM2575 and Digital 5V Power Supply using L296

Typical AC-AC Step Down Switcher

Here is an European SMPS, probably is for a Lamp. That means its is a Consumer Electronic Product. You can notice on the case, the Approval Seals on safety and standards.

Coils and Transformers for SMPS - here you will find more about the High Frequency Magnetics.

It takes in 230V AC mains voltage and gives out a 11.5V at 6.5A - 70 Watts AC. They are know also as "Electronic Transformer" used to drive Halogen Lamps. First notice the EMI Filter with One Coil and two small blue x-caps on the left. There are no Thermistors/Varistors or y-caps as it builds cost. The Switcher is made of Two HV NPN TO220 Transistors, the two blue rectangular caps and the HF Torroid Transformer. This circuit is wired up similarly to the Flip-Flop Multivibrator with LEDs which you call Dancing Lights.

Going off topic, the LED dancing lights were a craze when the LEDs came to market. with transistors like 2N2222 small Gizmos were made and powered by 9V batteries. The adorned bicycles, cars and even coat pockets of the part going folk to make an impression with the people of the opposite polarity.

This circuit with some modification was also used by many firms in the manufacture of "Electronic Chokes" it was used with the Large 40W Tubelights. The main failures that occur in this topology are the two HV NPN Devices.


Typical AC-DC Step
                                      Down Switcher







DC Regulated Power Supply

This is a Regulated 0-30 V DC Power Supply manufactured by me in small numbers, 0-30V 5A and 5V -5A. It had a Switching Preregulator. This keeps the Vce across Transistor Bank at the Back of Instrument, at the lowest possible level, in order to keep them Cool. When Vce and Ic both are more in a Power transistor it will get heated more, then the efficiency of power supply is low.
Variable Regulated
                                      Power Supply

The Output had both Constant Current Control and Constant Voltage Control. The CC control is also a Short circuit protection.  The Output was protected from outside voltages damaging output circuits even when equipment is switched off. The back panel is a finned anodized black aluminum heat sink with many transistors.

Lean about Mains 50/60 Hz Transformers Mains Transformers Types and Transformer Connections.

I looked for the circuits to scan them, i could not find it. I made-n-sold quite a few of them years ago. All of them work well even today as i over-rated most components. The cabinet was Steel for EMI-RFI Immunity, it was painted with Stipple Matt Powder Coating, the Cabinet maker had just learnt to give such a finish to his boxes.

Anantha Narayan


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