DIY Adjustable Power Supply: ToughTested & LEI

Voltage output from the cigarette lighter socket is 12V, manufactured by LEI in Taiwan with good craftsmanship and foldable copper prongs. Paired with the ToughTested car charger using the CXW8508 scheme, a DIY adjustable DC low-voltage power supply ranging from 1 to 9V was created, providing satisfactory performance.

I. Materials Section

The 12V power supply with a foldable copper plug used in the input power section is outsourced by LEI in Taiwan. It boasts good craftsmanship and a foldable copper plug.

The voltage regulation section utilizes the CXW8508 scheme from ToughTested's car charger. The CX8508 is a single-chip synchronous buck regulator with an integrated MOS, employing current control mode with quick instantaneous response and uninterrupted overcurrent detection. It features soft start, over-temperature protection, and consumes only 1μA in standby mode. With an input voltage range of 4.75V to 25V, an adjustable output voltage between 0.925V and 20V, and theoretically supporting up to 2A current, we've configured it for a 1-9V adjustable voltage. In a simple test, outputting at 1.5V with a load of 0.72A resulted in a voltage of 1.18V.

The circuit is straightforward, and by adjusting the resistances R1 (513/51K) and R2 (05C/11K), the output voltage can be modified following Vo=0.925x(1+R1/R2), with a default setting of 5.21V.

II. Combination Section

Adjustments were made to the car charger section to reduce size. The USB part of the car charger was removed, R1 (513/51K) resistor was eliminated, replaced by a 100K adjustable resistor (the basic single-turn horizontal type for easy scale identification). The output uses a 5.5-2.1mm DC cable.

To meet requirements, the car charger circuit board underwent some modifications, retaining only the circuit part and removing the USB output section.

A 100K blue-white adjustable resistor was chosen, providing a voltage range of 1 to 9V in approximately half a turn. Adjustments were made as needed.

After confirming correct functionality through testing, the components were assembled.

III. Expansion Section

The quality of the cigarette lighter socket in this power supply is excellent, making it suitable for DIY ATX power supplies with multiple output interfaces. Power can be drawn from both 12V and 5V lines of a computer ATX power supply. The cigarette lighter socket is connected to a DC 5.5mm female jack, outputting 12V, while a USB port outputs 5V.

An extension cable for the car charger housing was DIYed.