Principle and production of power converter for vehicle

The circuit is shown in the figure. The 12V power supply is taken out from the car cigarette lighter jack and sent to the input pin of the adjustable three-terminal regulator LM317 through one of the two-pole six-position band switch SW1A. Resistors of different resistances to the negative terminal of the power supply. When SW1 is in different gears, several voltages of 1.5V, 3.0V, 5.0V, 6.0V, 9.0V, and 12V can be obtained at the output end for corresponding low-voltage electrical appliances. LM317 should be installed on an aluminum radiator (100 × 100 × 25mm), mainly because it generates more heat at 1.5V. The entire circuit is packed into a suitable small box, and only the band switch is provided on the panel.

In the figure, R2 ~ R6 are the output voltage setting resistors. If other voltage levels are needed, they can be calculated as follows:

VOUT = (1 + R2 / R1) VREF + IADJ≌ (1 + R2 / R1) VREF

In the formula, VREF is the reference voltage, the typical value is 1.25V, IADJ is the current flowing from the ADJ pin, the typical value is 50μA, and R2 represents one of R2 ~ R6 in the figure.

In the figure, C1 and C2 are anti-vibration capacitors, C3 can improve the ripple removal rate and circuit stability, D1 is an output short-circuit protection diode, and D2 prevents damage to the regulator when the output is higher than the input potential.

The cigarette lighter jack in the car can only get 12V, but CD, LCD TV, MP3, game consoles, etc. require different power supply voltages. The simple converter made below can solve this problem.

Guangzhou Yunge Tianhong Electronic Technology Co., Ltd , https://www.e-cigarettesfactory.com