Automatic power supply stabilizer SEPIC

  • Dec 24, 2019
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This device is able to output a constant voltage of 0.8 to 30 volts with a current up to 5 amps at a voltage input of 4.5 to 30 volts. Digital indicator indicates the voltage at the output or at the input.


It has long been used in the electronics, reducing (Step Down) and increase (Step Up) converters, and the relatively Automatic SEPIC converters have recently emerged, which can both depress and raise the input voltage. IN this review He explained in detail how this works converter.

The converter is capable of delivering up to 5A, but no more than 80 watts.

Output voltage is set multiturn trimmer.

The indicator shows the output voltage (lit green LED) or an input voltage (red). The display mode switch small button under the display and is stored at power off.

When the voltage to 9.99 volts indicator shows, tenths and hundredths. At a voltage greater than 10 volts and the LED indicates tenths volts.


If you hold the button for 1 second, and the LED indicator will go out. To re-enable them, you need to press the button again. This condition is also stored, and turn off the indicator lights up when powered off and on the inverter.

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Pressing the button 3 seconds starts voltmeter calibration mode. Measurement of the input and output voltage is calibrated separately. First, the red LED and the indicator displays the value of the reference voltage (3.55-3.75 in). Each click button increases the value by one-tenth, and when the value of 3.75, jumps to 3.55. Keeping in what direction and how much to change the readings, change the value of the rate of 0.01 V reference voltage measured at 0.02 in. After a three-second pressing keys stored value, the green LED becomes and similarly exhibited significance for measuring the output voltage. I was able to calibrate the voltmeter so that it always shows the input and output voltage to within a tenth of a volt.

The board features two large inductor and two capacitors SANYO 1000 uF 35V. The remaining circuit elements are closed radiator.


View of the side of the board.


Bottom anything interesting.


Is input to the inverter 12 volts and exposed at the output voltage of 15 volts, I checked whether changing the output voltage of the load current. When the current is increased from 0 to 2.3a voltage remains stable.


To check the level of ripple, I applied for a 12-volt converter with a lead battery (I did not use the AC power source to eliminate the influence of pulsations). The load used 1.1 ohm resistor 200 watts.


When the voltage 5.7 V and the load current of 5 A ripple 17 mV. converter frequency is about 160 kHz.


When the same voltage and the output load of 0.5 A, the voltage ripple was about 12 mV.


When the voltage 22 volts and a current of 1 amp, voltage pulsations of about 30 mV.

Regardless of the nature of the input voltage changes (smooth or irregular), the output voltage remains stable.

At idle turned off indicator drive consumes 15-25 mA.

Converter efficiency depends on many factors. Maximum efficiency of 89.7% was recorded at an input voltage of 12-15 volts, the output voltage of 20 volts and a load current of 1A. Minimum efficiency - 78% when the converter 15 lowers to 5 volts.

The converter is worth only $ 7.90 with free shipping.
A few examples of its use:

- in the car to power any device requiring a stable supply voltage;
- for power devices requiring non-standard power supply voltage;
- as a cheap power source laboratory together with any conventional power supply (e.g. 12 V or 24 V).

© 2018 Alex Nadozhin