Power-Electronics (Page 3)

This is dual 555 multivibrator like power oscillator. This is my contraption and conception but couple of decades old. It appears to have errors. It worked but the document fixing after design worked, not done. This can be used to make a small inverter, for powering 230V gadgets of low power. The transformer is used in step-up mode. It may make a sound if the laminations are not of good quality.

This circuit can be modified using 7555 and switching transistors like BD139 driving a Ferrite 100 kHz transformer to build a Fluorescent Lamp of 10W to 20W.

From Schematics of delabs

Fluorescent lamps can be fired and lit at high frequency at relatively lower voltages. Experiment both with frequency and pulse width to get nominal lighting at good efficiency. One of the reasons CFL lamps -230V and emergency lamps 12V fail, is failure of the switching devices. These have to be overrated thrice or more, the switching heat dissipation should not be underestimated, during low/high voltage and keep a aging allowance.

Designing a working circuit is no big deal. But making a batch of reliable and robust power electronics products, which are idiot proof and abuse resistant is a challenge for engineering. Then they will need it at an affordable price too… Checkmate !

This is a SMPS Circuit application very close to the Application Note in the book SGS Motion Control Application Manual. This worked well. 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
Zoom Image

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 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 Filter

The Reference Application on ST Half Bridge Convertor – SG3525

PCB Layout

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

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.

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.

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Study these applications at IRF Applications and ST Application Segments.