Electronic circuit schematic: power-circuits

Electronic circuit : Automotive 12V to +-20V converter (for audio amplifier)

The limitation of car supply voltage (12V) forces to convert the voltages to higher in order to power audio amplifiers.

Electronic circuit : Square Wave Oscillator

A very basic square wave generator using a CMOS 4011 NAND gate.

Electronic circuit : Voltage Comparator

This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2. The limits are adjustable and the circuit made to trigger from the adjustable "window".

Electronic Circuit : 1.5 to 37 Volt 30 Amp Power Supply

A modification to the 12V 30 Amp power supply. This version uses an LM317 to provide a variable 1.5 to 37 Volt regulated output with currents up to 30 Amps. Max has built his power supply into an old computer case and can be seen on YouTube under Project Icarus.

Electronic Circuit : Power Zener Circuit

In this circuit a zener diode is "amplified" by a set of power transistors. The transistors substantially increase the current and power to the load.

Electronic Circuit : Power Fail Alert

In this circuit an electricity supply (domestic or industrial) is continually monitored. Should the supply be interrupted then an alarm will sound for the duration of the interruption. It has battery backup and overcharge protection.

Electronic Circuit : 12 Volt 20 Amp Power Supply

A 12 Volt high current 20 Amp power supply. The output voltage is variable from 12.2 Volt to 14.4V so can be set for any device requiring voltage and current in that range. This PSU uses an LM723 as the regulator, 4 parallel connected outboard pass transistors and has current limiting above 25 amps.

Electronic Circuit : Multiple Output DC Converter

A DC converter circuit taking one single DC input and converting to parallel multiple DC outputs.

Electronic Circuit : Adjustable Power Supply with Charger Output

Electronic Circuit :Fast Electronic Fuse

A fast electronic fuse designed to operate on 230V AC with an adjustable trip current.

Electronic Circuit : Variable Power Supply Using Fixed Regulator

This is a similar power supply that I used to power my FM Transmitter. After suffering long problems with mains hum, this design using a pi filtered C-L-C approach. This circuit offers excellent ripple rejection.

Electronic Circuit : 1.3 Volt Power Source

This is a replacement power source for 1.3V mercury cells or other small batteries. It has many uses and I use this circuit in my computer to power a front panel multi adapter which has a digital thermometer.

Electronic Circuit : Add-On Current Limiter for Power Supplies

This circuit allows you to set a limit on the maximum output current available from your PSU. It's very useful when you power-up a project for the first time - or carry out a soak-test. By setting an upper limit on the current available from your PSU - you can protect both your power supply - and any device connected to it.

Notes
The basic circuit is shown in the first schematic. The two diodes fix the voltage on the base of the Power Transistor at about 1v4. This means that the voltage across R2 is fixed at about 0v7. If R2 is 10 ohms, then the maximum emitter current is (0v7 ï¿½10) about 70mA.

Since the collector current is always more or less equal to the emitter current - you cannot draw more than 70mA from the output terminals. If you try to do so - the output voltage will fall.

I used a BD131 because that was what I had available. However, any NPN Power Transistor with a similar - or better - spec should work fine. I had no special reason for chosing a 70mA maximum. If you want to set a different current limit - change the value of R2. The formula is in the diagram. Always remember that if you increase the current - you'll also increase the watts.

The second schematic has a couple of added features. If you don't want to use a voltmeter on the output - use an LED instead. If the output voltage falls - the LED will dim or extinguish completely. This is enough to let you know that the load on the output is excessive.

Where the Current Limiter is to be left unattended for any length of time - say during a soak-test - the Buzzer is useful. Should a problem develope - and the output voltage fall by 2-volts or more - the circuit will sound the alarm.

Veroboard Layout
The layout provided is for the second schematic - but it's flexible. If you don't want the LED feature - just leave out the LED and R3. If you don't want the alarm feature - leave out D3, D4, D5, R4, R5 & Q2.

The heatsink is a folded strip of aluminium about 2mm thick, 6cm long and 3cm tall. If you increase significantly the maximum current available from the limiter circuit - you'll probably need to increase the size of the heatsink as well.

Electronic Circuit : Soft Start power Supply

Two soft start power supplies. The output voltage slowly increases to the desired output.

Electronic Circuit : Small Variable power Supply

Features: 1.3-12.2 V, 1 A, over-current protection. This is a simple but reliable device based one of the oldest integrated voltage regulators of them all - the LM723.

Electronic Circuit :Supply Voltage Indicator

A novel supply voltage monitor which uses a LED to show the status of a power supply.

Electronic Circuit : Current Limiting Power Supply

This is a 1-amp variable-voltage PSU. It adjusts from about 3v to 24v: and has the added feature that you can limit the maximum output current. This is invaluable when (for example) you power-up a project for the first time or soak-test a piece of equipment.