5 volts DC Regulator without Transformer Using MOSFET

If you are looking for the 5-volts DC regulator without transformer. This circuit may help you. It is suitable for the digital circuit, using low current. Use the MOSFET is based.

The advantage of this circuit is that it is small and lightweight. Ideal for circuits without enough space for transformers.

Caution! This circuit, DC Regulator Without Transformer is not suitable for connecting with others circuits outside. Because it does not have the isolation transformer. This circuit requires working alone In a plastic box or electrical insulation is good. It has the high voltage inside may kill you!

How 5V Transformerless power supply works

The diodes D1 to D4 are used to convert the AC power line to the DC pulse voltage. The peak voltage is about 310 volts. Then, It comes to the drain of the MOSFET-T1 through the limit current resistor-R9.

5 volts DC Regulator without Transformer Using MOSFET

The controller circuit causes the MOSFET works briefly only, in before and after of AC line cut at zero volts.

Now, the DC pulse voltage is lower than 5 volts.

In the same times, the current filter capacitors-C2 will be discharged. Also, it provides the output current. Thus, capacitor-C2 need to high capacitance about 10,000uF. The maximum current of DC pulse is 4A.

The stability of output voltage depends on the load. The maximum output current may be 110 mA.


The power supply of the controller includes The resistor-R2, capacitor-C1 and diodes-D5 and D6.

In the controller section is the window comparator circuit that includes three Op-Amp. Which we need to adjust correctly.

Before entering the AC-voltage to the input of the circuit. You should adjust P1 to a middle. Next, rotate P2 to low close the ground.

After that, apply the AC-voltage to the circuit. Then, check the working, voltage of the circuit. Using the DC voltmeter to measure the output voltage.

Next, adjust P2 until the meter needle starts to slightly wriggle. Next, adjust P1 until can read the meter is 4.8 to 5 volts.

The T1 and R9 generate the heat just about 3 watts only. So, it can be installed in tight spaces.
But you must be careful in making and using the circuit. It has the high voltage to appear in the circuit.

IC1,IC2,IC3: CA3130 op-amp
D1…D5: 1N4007, 1000V 1A Diodes
Pinouts of MOSFET BUZ74
BUZ74 MOSFET pinouts

‘Keep reading: Transformerless AC to DC power Supply circuits’ »

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