Simple USB to 12V DC Boost Converter Circuit

This simple USB to 12V DC boost converter circuit works as a DC-DC step-up converter.

It takes power from a USB port that gives 5V DC and increases it to 12V DC.

This circuit is really useful for powering small 12V devices using a regular USB source, like a power bank or a computers USB port.

At its heart the circuit uses the LT1618 boost converter integrated circuit, which is well-known for efficiently changing a lower voltage into a higher one while keeping everything stable.

The IC has a wide input voltage range, from 1.8 to 18V DC and can provide an output voltage of up to 35V DC.

Circuit Working:

Parts List:

The LT1618 chip is the key part that boosts voltage levels.

When you connect a 5V direct current the inductor L1 stores energy while the chips internal switch is on.

When the switch turns off the stored energy is released through the Schottky diode D1 which increases the output voltage.

Pin 9 is for shutting down the chip, if it gets less than 0.3V the chip will turn off.

Pin 4 is for adjusting the current sense, you can lower the current sense voltage by putting a DC voltage on this pin.

The circuit gets 5V DC power from a USB port.

To keep the input voltage steady and reduce noise capacitor C3 is used.

The LT1618 chip along with inductor L1 and diode D1 successfully raises the voltage to 12V DC.

A voltage divider made of resistors R1 and R2 sends feedback to the chip helping it keep the output voltage at the right level.

The transistor Q1 allows for external control of the circuit through the shutdown (SHDN) pin.

Formulas with Calculations:

Output Voltage Calculation:

Vout = 1.23V × (1 + R1/R2)

where,

• Vout is the regulated output voltage
• 1.23V is where IC LT1618 uses an internal reference voltage
• R1 and R2 are output voltage set using the resistor divider

Substituting values:

R1 = 909k and R2 = 107k:

Vout = 1.23V × (1 + 909k / 107k)

Vout = 12V

Feedback Voltage Divider Calculation:

The feedback voltage is determined using resistors R1 and R2 forming a divider network:

Vfb = Vout × (R2 / (R1 + R2))

where,

• Vfb is feedback voltage sent to the ICs feedback pin
• Vout is the regulated output voltage
• R1 and R2 are the resistor divider

These calculations ensure that the circuit provides a stable 12V output from a 5V USB source.

How to Build:

To build a Simple USB to 12V DC Boost Converter Circuit follow the below mentioned steps for connections and assembling:

• Assemble all the components as mentioned in the above circuit diagram:
• Connect pin 1 of IC1 LT1618 between resistor R1 and R2
• Connect L1 inductor coil between pin 2 and pin 7 of IC1
• Connect anode of diode D1 between pin 7 and resistor R1
• Connect pin 3 to pin 8 of IC1
• Connect resistor R6 between pin 3 and pin 2 of IC1
• Connect pin 4 of IC1 to one terminal of resistor R3 and other terminal of R3 connect to GND
• Connect pin 5 of IC1 to GND of the circuit
• Connect resistor R5 between pin 9 and pin 4 of IC1
• Pin 9 of IC1 is a shutdown pin
• Connect pin 10 of IC1 to GND through resistor R4 and capacitor C1 and GND
• Connect a GATE pin of transistor Q1 to ADJ pin to set output voltage regulation
• Connect the DRAIN pin of transistor Q1 between one terminal of resistor R4 and pin 4 of IC1
• Connect the SOURCE pin of transistor Q1 to GND
• Connect positive of capacitor C3 to +5V DC and negative of C3 connect to GND
• Connect positive of capacitor C2 to +12V DC and negative of capacitor C2 connect to GND

Conclusion:

Simple USB to 12V DC Boost Converter Circuit is a smart way to create 12V DC from a regular 5V USB source.

It is great for small electronic projects that need 12V but still want to be portable.

The IC LT1618 ensures high efficiency and by using an external transistor you can have more control over the output.

References:

Datasheet IC LT1618