Sunday, August 21, 2016

12 Volt Ultra Low Drop Power Supply with MOSFET Based Linear Voltage Regulator Circuit

Electronic Kit School. - If you want to find electronic circuit for building power supply with ultra low drop voltage in output, we suggest you to use MOSFET component like IRF540 to do this work. MOSFET can produce linear voltage regulator with with a voltage drop of as low as 60 mV at 1 A. 

This component we think very suitable for this low drop power supply when example you want to design 12 volt output voltage power supply for your electronic devices needed. With combine other component like shunt regulator and opto-Triac now we can produce this power supply easily.

In this article we will give you one electronic circuit design that give you 12 volt power supply with very low drop voltage in output using MOSFET based linear voltage regulator look like shown in Figure 1 below. Read also: 24V/7A Lead Acid Battery Charger Circuit using LM317 IC.


Figure 1. 12V Ultra Low Drop Power Supply with MOSFET Based Linear Voltage Regulator Circuit

Component Parts

  1. Transformer 12-CT-12 with 2A
  2. Resistors
  3. MOSFET IRF540
  4. Capacitors
  5. IC1 MOC3021 Opto-Triac
  6. Diodes
  7. IC2 TL431
  8. Zener diode
  9. Variable resistor

Circuit like in Figure 1 above show you about the 12 Volt Ultra Low Drop Power Supply with MOSFET Based Linear Voltage Regulator Circuit that can give you ultra low drop power supply 12 volt output. The main component used in this circuit is MOSFET IRF540 that will give a voltage drop of as low as 60 mV at 1 A.

With better MOSFETs having lower RDS(on) resistance it is very possible get a drop of a fewer millivolts only. In the first condition that voltage 220VAC/50Hz from AC source will connected to transformer step-down with 15V-0-15V secondary and it will employ an n-channel MOSFET IRF 540 to get the regulated 12V output from DC input after rectification, it which could be as low as 12.06V output voltage. 

A voltage doubler circuit consisting of diodes D1 and D2 and capacitors C1 and C4 generate to the gate drive voltage required for the MOSFET IRF540. The gate terminal should be around 10V above the source terminal to turn the MOSFET fully on, which is connected to the output here. 

The voltage doubler consumes this voltage to the gate through resistor R2. The dynamically adjusts the gate voltage to maintain the regulation at the output and an error amplifier in this circuit is used by Adjustable shunt regulator TL431 (IC2) or similarity

The MOSFET, the circuit can served up to 3A output at slightly elevated minimum voltage drop with adequate heatsink. Trimpot RV1 in the circuit is used for good adjustment of the output voltage. Te capacitor C6 and resistor R4 serves error-amplifier compensation. The circuit is served with a short-circuit crow-bar security to guard the components against over-stress during accidental short at the output. 

When this crow-bar security or protection will work? It work when it under normal working conditions, the voltage across capacitor C4 will be 6.3V and D5 zener diode will be in the off state since it will be reverse-biased with the output voltage more than of 12V. The output will momentarily drop during output short-circuit condition, causing D5 zener diode to conduct and the opto-triac MOC3021 (IC1) will get triggered and pulling down the gate voltage to ground. It is will make the limiting the output current. The circuit will reside latched in this condition, and input voltage has to be switched off to reset the circuit work.


  • Please use heat sink for MOSFET IRF540 for reducing the temperature.


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