DC 6V to 12V Boost Converter Circuit Using 555 Timer IC

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This post tells you how to convert a DC voltage at a higher  DC voltage.A boost converter (step-up converter) is a DC-to-DC power converter with an output voltage greater than its input voltage. It is a class of switched-mode power supply (SMPS) containing at least two semiconductor switches (a diode and a transistor) and at least one energy storage element, a capacitor, inductor, or the two in combination. Filters made of capacitors are normally added to the output of the converter to reduce output voltage ripple.

Since it “steps up” the source voltage and  power (P = VI) must be conserved, the output current will be lower than the source current.
Fig(a): Operation of a Boost Converter

 Operating principle of a Boost Converter:
There are two operating principle of describing the boost converter.

  1. When the switch is closed, current flows through the inductor in clockwise and the inductor stores some energy by generating a magnetic field. Polarity of the left side of the inductor is positive.
  2.  When the switch is opened, current will be reduced as the impedance is higher. The magnetic field previously created will be destroyed to maintain the current flow towards the load. Thus the polarity will be reversed (means left side of inductor will be negative now). As a result two sources will be in series causing a higher voltage to charge the capacitor through the diode D.
Description of 6V-12V Dc Boost Converter:
Here switching operation will be performed by a NPN transistor with the help of a clock pulse, i.e. a transistor will work as a switch . A clock pulse is designed by the 555 timer IC. This clock will help the transistor to act as a switch.See the figure below,


The 555 timer IC is operating in Astable mode. The duty cycle is 55% and the frequency is about 31.4 kHz. The source voltage is 6V. So the clock is generating 6V with 55% duty cycle and 31.4 kHz. This clock is applied to the base of transistor through a resistor.

Parts List:
  1. 555 Timer IC;
  2. Q1= TIP41C NPN Transistor;
  3. D1= 1N4007 or Equivalent;
  4. D2= 12V Zeber diode;
  5. C1= 2.2 nF;
  6. C2= 10 nF;
  7. C3= 1000 uF, 25V (Electrolyte capacitor);
  8. R1= 2.26 k ohms;
  9. R2= 10.2 k ohms;
  10. R3= 1 k ohms;
  11. L1= 2.2 mH;
  12. Supply: 6v DC.
For better performance, you can use a capacitor across the source.

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