Power Supply Circuit

12V DC Power Supply Circuit

Often the beginner which has a 12V DC power supply circuit board with a maximum current 1A, looking for ways to increase the load capacity of more than 1A. In the sense of how to modify their power-supply circuits by adding an additional circuit in the form of the final transistor that has a larger load current. It required a little theory and a power-supply circuits diagram.

Actually, the power supply circuit is built from a LM7812 as is known in common is a 12V DC power supply is a simple to use IC 7812. Only by giving unregulated 15V DC input voltage to the IC 7812 and gives some capacitor as a voltage filter, then a stabilized power supply you are ready to use.

In the following power supply circuit diagram uses a single voltage regulator IC 7812 and multiple outboard pass transistor, power supply can deliver output load currents of up to 30 amps. Power supply circuit schematic design is shown below.

30A 12V DC Power Supply Circuit Diagram

This power supply circuit is a good example for the application of the law of Kirchhoff current and voltage. In summary, the amount of currents entering the junction, must equal the current leaving the junction, and the voltage around the loop must equal zero.

30A 12V DC Power Supply Circuit Diagram

For example, in the power supply circuit diagram above, the input voltage is 24 volts. 4 volts dropped in R7, and 20 volts across the regulator input, 24 -4 -20 = 0. At the end: – the total load current is 30 amps. The regulator provides 0.866 A and six amp transistors 4855 each, 30 = 6 * 4.855 + 0.866. Each power transistor contributes about 4.86 A to the load. The base current is approximately 138 mA per transistor. A DC gain of 35 to a current collector six amp is required.

It is well within the TIP2955. The resistors R1 to R6 are included for stability and prevent the flooding current manufacturing tolerances of DC Current Gain will be different for each transistor. Resistor R7 is 100 ohms and volts with 4 develops a maximun charge. Power dissipation is (4 ^ 2) / 200, about 160 mW. I recommend using a resistor R7 to 0.5 Watt.

The input current controller is powered through the emitter resistor and base-emitter junctions of the power transistors. Again using Kirchhoff’s current laws, current 871 mA input controller is derived from the base line and 40.3 mA flowing through the resistance of 100 Ohm. 871.18 = 40.3 + 830. 88. The current of the regulator itself cannot be greater than the input current. As you can see the regulator rely only about five mA and should run cold. For more information please go the following link 12 Volt 30 Amp Power Supply Circuit.

See also: High Voltage DC Converter Circuit