Bench Power Supply

Mini Bench Power Supply Circuit

Electricity is a key component of any electronics project. To power all your electronic projects, you can use a power supply in a compact and simple. But for the beginner, much fun electronic projects that wish to build does not want to drain the pocket to buy a bench power supply commercial model. The important thing is the power supply circuit capable of supplying a variable output voltage from 1.5V up to 15V.

Bench Power supply described here is a simple unit that easily built with simple components. He is only suitable for small to load that is between 18V and 24V applied to the input, for example, a laptop power supply.

Mini Bench Power Supply Circuit Diagram

This is done to avoid the need for an expensive transformer and accompanying smoothing. Fixed output voltage adjustable down to 0V with no need to use a negative supply.

A difficulty in the design of power supplies with current limiting is the shunt resistor needed to measure the output current, normally connected to a differential amplifier. Frequently in simple designs the amplifier is not powered from a regulated supply, which can lead to an unstable current regulation loop.

This bench power supply circuit avoids the difficulty by using a low-cost fixed voltage regulator to supply the feedback circuit with a stable voltage. This arrangement greatly simplifies current measurement and regulation. (see: Power Supply Circuit at Mini Bench Power Supply Circuit)

A type LM324 operational amplifier is suggested as, in contrast to many other similar devices, it operates reliably with input voltages down to 0 V. Other rail-to-rail opamps could equally well be used. The particular n-channel MOSFET devices used are not critical: a BUZ21, IRF540, IRF542 or 2SK1428 could be used for T1, for example, and a BS170 could be used in place of the 2N7002.

The capacitors should all be rated for a voltage of 35 V or higher, and R15 and R17 must be at least 0.5 W types. The fixed voltage regulator and T1 must both be equipped with an adequate heatsink. If they are mounted on the same heatsink, they must be isolated from it as the tabs of the two devices are at different potentials. Here’s the schematic of Bench Power Supply.

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