This USB to 12V DC Boost Converter Circuit works as step-up converter, it take 5V from USB and make 12V DC; also this is useful to power small 12V device from USB, like power bank or computer USB.
Furthermore, it uses LT1618 boost IC inside which is good to change low voltage to high voltage and keep it stable and also this IC work from 1.8V to 18V input and can give output up to 35V.
Circuit Working:
Parts List:
| Components | Values | 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 and when switch is OFF energy goes through diode D1 and raise output voltage.
Then pin 9 is for shutdown and if less than 0.3V then chip goes OFF and pin 4 adjust current sense and put DC voltage to lower it.
Circuit get 5V from USB.
After that, capacitor C3 keep input steady and with less noise and LT1618 IC with L1 and D1 raise voltage to 12V DC.
Now resistors R1 and R2 make feedback to keep output right and 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
Hence, 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:
- First, connect IC1 LT1618 pin 1 between R1 and R2 resistor
- Next, connect L1 coil between IC1 pin 2 and pin 7 and then connect diode D1 anode between pin 7 and R1
- After that, connect IC1 pin 3 to pin 8 and also connect R6 between IC1 pin 3 and pin 2
- Now connect IC1 pin 4 to one side of R3 and other side R3 to GND
- Also, connect IC1 pin 5 to GND
- Then connect R5 between IC1 pin 9 and pin 4
- Pin 9 is shutdown pin
- Further, connect IC1 pin 10 to GND through R4 and C1
- Now connect transistor Q1 GATE pin to ADJ pin for output voltage control, connect Q1 DRAIN pin between R4 and IC1 pin 4 and then connect Q1 SOURCE pin to GND
- Finally, connect C3 positive to +5V and negative to GND and then connect C2 positive to +12V and negative to GND
Conclusion:
Overall, 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.
Also, IC LT1618 chip make efficient boost and external transistor give more control on output.