This USB to 12V DC Boost Converter Circuit works as step-up converter.
It take 5V from USB and make 12V DC.
This is useful to power small 12V device from USB, like power bank or computer USB.
It uses LT1618 boost IC inside which is good to change low voltage to high voltage and keep it stable.
IC work from 1.8V to 18V input and can give output up to 35V.
Circuit Working:
Parts List:
| Component Type | Value | Quantity |
|---|---|---|
| Resistors( All resistors are 1/4 watt unless specified) | 909k | 1 |
| 107k | 1 | |
| 13k | 1 | |
| 2k | 1 | |
| 20k | 1 | |
| 0.1Ω | 1 | |
| Capacitors | Ceramic 10nF | 1 |
| Electrolytic 4.7µF 25V | 2 | |
| Semiconductors | IC LT1618 | 1 |
| Transistor BS170 | 1 | |
| Schottky Diode MBR0520 | 1 | |
| Inductor 10µH | 1 |
LT1618 chip is main part for boost voltage.
When 5V DC come inductor L1 store energy while chip switch is ON.
When switch is OFF energy goes through diode D1 and raise output voltage.
Pin 9 is for shutdown and if less than 0.3V then chip goes OFF.
Pin 4 adjust current sense and put DC voltage to lower it.
Circuit get 5V from USB.
Capacitor C3 keep input steady and with less noise.
LT1618 with L1 and D1 raise voltage to 12V DC.
Resistors R1 and R2 make feedback to keep output right.
Transistor Q1 let external control shutdown pin.
Formulas with Calculations:
Output voltage calculation:
Vout = 1.23V × (1 + R1/R2)
where,
- Vout is output voltage
- 1.23V is chip internal reference voltage
- R1 and R2 set output voltage by resistor divider
With R1 = 909k and R2 = 107k
Vout = 1.23V × (1 + 909k / 107k) = 12V
Feedback voltage divider:
Vfb = Vout × (R2 / (R1 + R2))
where,
- Vfb is feedback voltage to chip
- R1 and R2 make resistor divider
This keep circuit output stable.
How to Build:
To build a USB to 12V DC Boost Converter Circuit follow the below mentioned steps for connections and assembling:
- Connect IC1 LT1618 pin 1 between R1 and R2 resistor
- Connect L1 coil between IC1 pin 2 and pin 7
- Connect diode D1 anode between pin 7 and R1
- Connect IC1 pin 3 to pin 8
- Connect R6 between IC1 pin 3 and pin 2
- Connect IC1 pin 4 to one side of R3 and other side R3 to GND
- Connect IC1 pin 5 to GND
- Connect R5 between IC1 pin 9 and pin 4
- Pin 9 is shutdown pin
- Connect IC1 pin 10 to GND through R4 and C1
- Connect transistor Q1 GATE pin to ADJ pin for output voltage control
- Connect Q1 DRAIN pin between R4 and IC1 pin 4
- Connect Q1 SOURCE pin to GND
- Connect C3 positive to +5V and negative to GND
- Connect C2 positive to +12V and negative to GND
Conclusion:
This USB to 12V DC Boost Converter Circuit make 12V from normal 5V USB.
It is good for small projects and need 12V and is portable.
IC LT1618 chip make efficient boost and external transistor give more control on output.