delabs Circuits

Showing posts with label Switching-Regulators. Show all posts
Showing posts with label Switching-Regulators. Show all posts

Saturday, August 13, 2016

5V -1A Power Supply using LM2575

A Power Transistor which is having a drop of 4 Volts across it and passing 3 amps thru it, may dissipate around 12 Watts of Heat, This is the problem in Series Regulators. While a Saturated Transistor or Mosfet with 1 Volts across and 3 Amps Thru will be just 3 Watts. But then a fully on transistor or mosfet cannot be controlled or regulated, for that we turn it ON and OFF very fast so that the right amount of current or voltage is delivered.

Power Electronic Circuits  

5V -1A Power Supply using LM2575

The way this is done is PWM - Pulse Width Modulation. In this the mosfet or transistor is switched ON-OFF at say 100 kHz, but the ON duration is varied to control the output. The longer the duration of ON time more energy or punch is transferred. Switching losses will be present depending on how fast the rise and fall times of the pulses are.

The Pulsed AC or Chopped DC can be smoothed to the Average with Inductors and Capacitors. The reactive pulses of the Inductor has to be absorbed by a Schottky Rectifier 1N5817 -- 20V-1A fast switching diode with low switching losses.

This circuit is derived from an application note of LM2575, It is a Power Switching Regulator from National Semiconductor The details are here LM2575

Tuesday, May 10, 2016

Digital 5V Power Supply using L296

This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST. The advantage of using a switching regulator is that there is not much Heat Dissipation in this circuit.

Switching Battery Charger with L296 - del20031

Digital 5V Power Supply using L296

If you had to build the same with a series regulator, it would be very big due to external transistor and a huge heat sink. This circuit takes a small place on PCB, efficiency is high so power is saved and reliability of product improves, lastly the thermal gradients within the cabinet is avoided so that any form of drift or component specs variation can be avoided.

L296 and L296P are stepdown power switching regulators 4 A at a voltage variable from 5.1 V to 40 V.  External programmable limiting current. Soft start, remote inhibit, thermal protection, a reset output for microprocessors.

The Schottky rectifier BYW80 is used as it switches very fast 200V-20A-35nS. The Inductor and Capacitor is for the filter to get a ripple free DC from the Chopped DC output. There may be a small high frequency ripple riding on the DC signal of 5V in most SMPS circuits. So for very sensitive circuits use extra filters and shields.

The Current output is limited, and can be reduced further with a resistor from Pin 4 to ground. Also if the feedback to Pin 10 is thru a Voltage Divider then more voltage can be set at the output. See the datasheet and application notes for other design details and circuits.

Tuesday, February 09, 2016

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.  More details and PCB's Here SG3525 SMPS Project.

100kHz Half Bridge Convertor - SG3525

This was the Module that contained the smps chip. It was done to prevent easy replication by other firms. Alos to Keep the Signals isolated from the Main board board currents and Corrosion Prevention by impregnating Module in Epoxy. Yet the main board suffered some corrosion even with some coating protection.

SG3525 STMicro IC in Module

Industrial Systems that involve processes like Etching, Coating and Electroplating have to be well ventilated so that electronics around them have some life. Else find ways to package Electronics in Sealed Enclosures with a new plan for Heat Dissipation.

Wednesday, August 13, 2014

Switching Battery Charger with L296

This is a a circuit from my  Power Supplies Section.  There may be some documentation errors in my circuits. If you are used to building and troubleshooting circuits then it is ok.

This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST Micro. U1A is wired as a differential amplifier and U1B a High Gain Comparator. C4 and C5 are parallel for lower ESR. Equivalent series resistanc Fast switching diode used is BYW80.

Switching Battery Charger with L296

L296 is a switch mode power controller here. In this NTE327 or 2N5038 is used to boost the current output. This transistor is both high current and fast switching. U1A, LM358 measures the load current by reading the voltage across shunt R6 and compared to a current limit setting at R14 using U1B to give a load current control. R7-R8 give a voltage feedback for voltage limit.

Use MFR 1% for all Resistors, 33E means 33 ohms, 22K means 22 kilo ohms, 1M is 1 megohm. 10T tp means ten turn trimpot. "Analog Ground" and "Digital Ground" must be linked at power supply only, avoid loops, let grounds radiate from a ground plane. Unused inputs of logic and opamps pull up or down to avoid oscillations and noise

Circuits by Application

Analog Circuits

  1. Battery Level Indicator
  2. Simple Sample and Hold
  3. Sample and Hold Standby
  4. Voltmeter Attenuator
  5. Precision Current Source
  6. Opamp Supply Virtual Ground

SCR and Triac

  1. Solid State Relay
  2. Normally Closed AC SSR
  3. AC-AC-SSR
  4. DC-DC SSR
  5. 2N2646 based Pulser
  6. Drive SCR thyristor

Mains Power

  1. Flashing Neon Lamp
  2. Dimmer power control
  3. Edison Bulb Life Extend
  4. Mains Current LED
  5. Mains Voltage LED

Digital Circuits

  1. Simple Digital Counter
  2. Running Lights
  3. Frequency Divider
  4. Crystal Oscillator
  5. Simple High speed switch
  6. Differential TTL converter

Measureall DMM

  1. Ohmmeter Measure Resistance
  2. Precision Digital Attenuator
  3. Precision Amplifier

Mixed Circuits

  1. Monostable Multivibrator
  2. Digital to Analog
  3. LM311 Oscillator
  4. PLL using 4046
  5. VCO with LM331
  6. BCD Thumbwheel to Analog
  7. V to F Converter ICL8038
555 Circuits
  1. OR gate with two 555
  2. fixed frequency duty cycle
  3. Pulse width modulation
  4. Astable Multivibrator
  5. uC Reset Generator
  6. LM555 Voltage Doubler
  7. 555 Power Oscillator
Discrete Circuits
  1. Isolated dual supply
  2. Sound to light converter
  3. Water operated relay
  4. Telephone Indicator
  5. Passive volume control
  6. RS232 Opto-Isolation
  7. Voltage Level Indicator
  8. Relay Driver
  9. Constant Current LED
  10. Voltage Doubler
  11. FET Current Source
Opamp Circuits
  1. Three Opamp Differential
  2. Two Opamp Differential
  3. Buffer Opamps
  4. Differential Op-Amp
  5. Inverting Opamp
  6. Non Inverting Opamp
  7. Digital gain control
  8. Square Triangle Oscillator
  9. Dual Polarity Output Amps
  10. Ammeter Precision Rectifier
  11. Voltage / Current 4-20 mA
  12. Current Source for RTD
Power Electronics
  1. Dual Power Supply
  2. Single Power Supply
  3. Battery Backup Supply
  4. 5V 1A Supply LM2575
  5. 5V Power Supply L296
  6. Dual Power Supply
  7. Tubelight Electronic Choke
  8. Voltage Doublers Multipliers
  9. White LED Lamp on Ni-Cd

uC and uP

  1. PC RS232 with MAX232A
  2. Battery Backup SRAM
  3. watchdog uC uP systems
Instrumentation Circuits
  1. Mains monitor LM3914
  2. Simple Mains monitor
  3. single digit voltmeter
  4. High Resistance Meter
  5. Diode Thermometer
  6. Function Generator
  7. Diode Leakage Tester
  8. Analog LED Ohm Meter
  9. Millivolt Source Current Loop
Process Control
  1. AD590 - temperature
  2. Thermocouple Amplifier
  3. Linearizing Thermocouple
  4. Thermocouple Amplifier
  5. 0-1V to 4-20 mA
  6. 1-5V to 4-20 mA
  7. InfraRed - Optical Switch
  8. InfraRed Detector