12 volt DC Power Supply from USB port
The circuit given below infact is a 5 volt to 12 volt converter. It uses the 5 Volts from USB port and converts it to 12 volts DC with the help of IC LT1618.
Using this circuit we can convert 5V DC from the computer USB port to 12V DC and a circuit like this will find a lot of application in USB powered systems. The heart of this circuit is IC LT1618 which is a constant current, constant voltage boost converter. The IC has a wide input voltage range of 1.8 to 18V DC and output voltage can be up to 35V DC.
In the circuit resistors R1, R2 sets the output voltage. Pin number 9 is the shutdown pin, less than 0.3V to this pin will shut down the IC. Pin number four is the current sense adjust pin. The current sense voltage can be reduced by applying a DC voltage to this pin. If this adjustment is not needed connect this pin to ground and you can omit components R3, R5 and Q1.
Circuit diagram of 12 volts dc power supply:
- C2 and C3 must be rated at least 15V.
- Less than 0.3V at the shutdown pin will shutdown the IC.
- Output voltage is governed by the following equation R1 = R2 ( (Vout /1.263V) -1).
Other Circuits Related to Power Supplies:
2. Votage Doubler and Inverter
4. Simple DC Power Delay Circuit
Check our category on Power Supplies for more circuits,articles and applications.
Where should we connect SHDN and ADJ in USB output port? plz hlp
shutdown and adj to be connected to the incoming supply, at PIN No 3 of the IC. refer LIN IC datasheet.
Hi Robert you can try this circuit which has appeared earlier the ic is available in most of the places(LM2698)
which component do i use instead of LT1618 it is not locally availaible
Hi Rohit use one 3pin regulator IC 7805 through 1 ohm 1 watt connect to cigar lighter socket observing the polarity. use typical application drawing 1 circuit add 1 ohm for short circuit protection, use a good heat sink for the IC
I am looking for a power supply, i want to use in the car, 12volt input and 5v output, approx. 1A (i want to charge my IPOD in the car).
Any help will help.
thanks and regards
Hi Onurtasar the maximum output limit is 150mA at 12Volt. This is a switching supply. You can limit the input current limit facility also such that you don’t draw large current from USB port. kindly go through datasheet for more information.
what is the value of the max output current of this circuit?
And could you please explain your design.
how the working principle of this circuit…
thanks for your valuable updates. really helpful