12 to 5 volt Converter Circuit (for cars)

Apr 182023

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12 to 5 volt converter circuit (for cars)

This 12 to 5 volt converter circuit is very useful. It can be used to connect 5 volt electronic devices to a 12 volt battery. (Automotive lead-acid batteries can be up to 13.5 volts). When a 5V regulator such as the LM7805 is used, the maximum current it can deliver is 1 Amp.

This current may not be enough for some of the devices we want to connect. It may also be insufficient if we connect 2 or more devices at the same time. To solve this problem, we will use a transistor to increase the output current.

How does the 12 to 5 volt converter circuit work?

This circuit can supply enough current using the 5 volt regulator and a transistor (Q1) as shown in the figure. Capacitors C1 and C3 are used to flatten the voltage at the input and output of the regulator. Capacitors C2 and C4 are used to filter any noise generated by the vehicle’s electrical system.

This circuit has the disadvantage of a base-emitter voltage drop (Vbe) of 0.6 or 0.7 volts, resulting in an output voltage of 4.3 or 4.4 volts. This voltage is different from the required 5 volts. Therefore, a diode is connected to the GND pin of the voltage regulator to compensate for this voltage drop.