I often make the small projects. They require the small power supply. But I cannot find the small transformers. The normal transformer is big and heavy, not suitable for my project. But I look around my home in a small appliance in China. They use the transformerless power supply circuit.
They use a capacitor instead of a transformer. Thus, power supplies are smaller and lighter. Today, I collect these transformerless power supply circuit. So you can select as you want.
Hopefully, it will be useful to you. There are three circuits, as follows. (see below!)
First—9V DC Power Supply circuit, no transformer
This is 9V DC power supply no transformer, It is an easy circuit and small size.
The output voltage is the same as the voltage drop across the Zener diode-ZD1. The Output Current is about 100mA (min).
9VDC Power Supply circuit diagram, no transformer
You may know the reason that makes power supply is large-sized. Because of a transformer. How to do if not use it. We use a capacitor instead of a transformer.
In the 9V, DC Power Supply circuit, no transformer. First, the capacitor 0.33uF and R1 makes a low AC voltage. The F1 protects output overload. R2 is the limited current resistor.
The Zener diode keeps the output voltage to be stable 9V DC Regulator. This circuit cannot power the output with high current.
Second—No transformer DC power supply circuit
How does it work? Both C1 and R1 reduces AC Current Source to rectifies to DC pulse voltage with bridge diodes. Which D1 through D4 convert AC to DC.
Then, the C2 filtering capacitor smooths to the stable DC voltage. The output voltage is regulated to maintain a constant DC voltage with the Zener diode, ZD1-9V. Last, the C3-capacitor filter the output voltage to be more smooth.
This is the mini power supply circuit out of 6V, in negative voltage. Also, it does not use the transformer like the above circuits.
It can give the output current at less than 100mA. It uses the Zener diode to provide a constant output voltage, 6V. There is a transistor to increase the current up. It has still overcurrent protection or Shot Circuit Protection with Transistor as well.
Transformerless power supply circuit, 15V
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