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# Isolated DC Converter for Digital using 555

This is an isolated DC to DC Converter circuit in digital. In using a digital measurement circuit to connecting with other circuits. If the primary voltage is 5 V, but you want a higher voltage between 9V to 12V.

This circuit may solve your problem! It can converter a DC 5V intput into DC 7.5V to 12V output at 50mA current. Important! it is an isolated style makes a good performance.

They include a few parts, 555 timer, small transformer, Zener Diode, and more in simple circuit. It may help you.

How it works

In circuit consist of an astable Multivibrators using 555 timer. They will control a power supply is on and off. To drives a transformer-T1 through the transistor Q1-BC547.

The output voltage of the secondary coil is rectified by D4 (in half wave) and filtered with the capacitor C3 and then there is the Zener diode-ZD1 as act regulated voltage.

## How choose parts in Isolated DC Converter

Transformer-T1—is 1 to 1 ratio pattern. You can look these transformers in many using. For example, To control an SCR and a small radio transformer, etc.

Each type of transformers is suitable for the different frequency and pulse width.

• SCR transformer is suitable for the frequency of 100 kHz.
• Audio frequency transformers, as well as approximately 0.5 to 40 Hz.

VR1 and VR2—adjust that frequency and pulse width of the output oscillator.

Then, look at Figure below. The frequency waveform includes two time width.

• Charging Time is controlled by VR1, R1, and C1.
• DisCharged Time is controlled by VR2, R2, and C1.

While Diodes D1, D2 set a direction of the current each time.

The frequency of the circuit can get by:

F = 1/[0.7C1(VR1+VR2+R1+R2)]
= Hz

Zener diode ZD1—set the output voltage. For example, 7.5V, 9V, 12V max.

Parts you will need
IC1: 555 timer
Q1: BC548, NPN transistor
D1-D4: 1N4148 diodes
C1,C3: 10uF 25V Electrolytic
C2: 0.001uF 50V Ceramic capacitor
0.25W 5% Resistors
R1, R2: 1K
R3: 4.7K
R4: 220 ohms
VR1, VR2: 100K to 1M potentiometer

Notice The transformer must be connected in proper polarity. Do not connect in the wrong terminal.

## ‘5V to 12V step up connverter, easy!’ »

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