Power Supply Unit

A standard Power Supply is usually fitted with a Transformer to step down the voltage from the mains and provide galvanic Isolation between the high voltage and low voltage section.

In this Power Supply transformer is not been used for step down the voltage. Thus it saves a lot of space and weight of the Power Supply Unit.

To construct this Power Supply following steps have been taken into account. Firstly a rough 40 volts power supply has been made using some passive and active components. And subsequently use this rough 40 volts supply to the Step down Converter IC (LM 2595 -*). This converter IC will be able to operate maximum at 40V.  On proper using this converter IC a stable low voltage @1 Amp can be achieve.

CIRCUIT DESCRIPTION: The 230V AC mains supply voltage is fed to the Fuse (F) and then converted to DC voltage using a bridge rectifier stage. One MOSFET (TR2) has been used as a switch and that can be turned off when the supply voltage may be greater than 40 volts. Thus the Gate of TR2 is driven via R4 & R5. Suppose when the voltage exceeds 40V transistor TR1 conduct and resulting the Gate-Drain voltage of TR2 arrest the supply voltage at TR2 limits to 40V This 40V supply has been fed to the IC LM2595-* and related components to achieve the desired * voltage. [NOTE: The * voltage is either 3.3 or 5 or 12; i.e. the nomenclature of the IC is LM2595 – 3.3 or LM 2595 – 5 or LM 2595 – 12]

CAUTION: As the above mentioned Power supply Unit is working directly on 230V AC Power Supply, it is highly essential to be very much causes not to touch any part or component/s when the circuit is in operating condition.

Bill of material and Circuit Schematic

Electronic Circuits – Simplified