Simple 3.3V Power Supply circuit @ 1A for Digital

If you would like to build Simple 3.3V Power Supply circuit for digital microcontroller or esp8266. This circuit may be one way for you. It can power current at 1A maximum. We normally use common electronics parts, so easy and cheap.

The Working of Circuit

Schematic Diagram of Simple 3.3V Power Supply circuit @ 1A

Figure 1 : Schematic Diagram of Simple 3.3V Power Supply circuit @ 1A

This regulated power supply consists of step-down transformer T1, a full-wave rectifier bridge(D1 to D4), and a filtering regulator circuit made up of C1,C2,R1,R2,ZD1,and Q1.

To begin with, We feed a 220VAC/110VAC voltage to the transformer-T1, to change 220VAC to about 6.3VAC. Then,the rectifier bridge (D1 through D4) rectifies the AC into pulsating DC.

Next, the Electrolytic capacitor filter the DC Pulse to smooth better. The capacitor C1 acts as a storage capacitor.

Then the unregulated will flow to Zener Diode-ZD1 through R1-resistor. The Zener will keeps the voltage constant across the base of PNP transistor-Q1, it cause fixed voltage across resistor-R2 and the output terminals.

Fuse F1 will blow if the current through the output terminals is too high.


PNP transistor 2N456 or TIP42 or MJE2955,etc.If do you want other dc voltage, you must change ZD1 : 5.6V for 5V output.

C1-Capacitor use to smoothed current output, using 1500uF or 2200uF(better).

The float-voltage measured here for the 6.3V transformer was 8.4V.

If do you want to detail more, please read in image circuits.

Parts you will need

  1. Q1_2N456 or TIP42 or MJE2955__100V, 4A, PNP transistor; Quantity = 1
  2. R1_270 ohms_1/2W Resistors tolerance: 5%; Quantity = 1
  3. R2_1K_1/2W Resistors tolerance: 5%; Quantity = 1
  4. C1_1000uF 25V/2,200uF 25V_Electrolytic Capacitors; Quantity = 1
  5. C2_100uF 25V_Electrolytic Capacitors; Quantity = 1
  6. C2_0.1uF 50V___Ceramic Capacitors; Quantity = 1
  7. D1-D4_1N4002__100V 1A Diodes ; Quantity = 4
  8. ZD1_3.9V 1W_Zener Diode; Quantity = 1
  9. T1_230V AC primary to 6.3V,1A secondary transformer; Quantity = 1
  10. S1_SPST Power Switch; Quantity = 1
  11. F1_0.5A Fuse; Quantity = 1

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