Sunday, July 31, 2016

Adjustable DC to DC step up voltage booster using LM2577 -Adj P+ chip

One simple circuit to step up voltage using LM2577 -Adj P+ chip. The schematic is from Texas Instrument and it works expected - and below is demonstration video using 4.05 Volts 18650 battery the nominal step up voltage is up to 19 volts. However the true voltage is around 15 Volts to 10 Volts which is still good.

In the video there is one slight modification from the original schematic diagram instead of using 2KOhm resistor on the feedback to ground I've change it using 10 KOhms potentiometer to allow adjustable voltage boost. This gives flexibility how much voltage you want instead of having it fixed so that you can adjust accordingly to the need of the loads.

As you can see an LED that requires 8 Volt cannot be powered up by 18650 battery rated at 4.05 Volts. With the step up booster circuit we can adjust to the voltage how it requires and it will light up brightly as in the Video. This is a good circuit to power up something larger voltage circuit including mobile phones, iPhone, iPad or any electronic gadget charger. As you can see from the Texas instrument diagram 5 volt can step up to 12 volt with the current output draw approximately 800mA. This is quite efficient.

Component Requires in this circuit

0.1 uF - ceramic capacitor
0.33 uF - ceramic capacitor
2.2KOhm - Resistor
100 uH - Inductor (choose the one with less resistance but high current)
LM2577 +Adj - This is the driver of the circuit
1N5821 - Schottky Diode
17.4KOhm - Resistor
2KOhm - Change with Potentiometer 10KOhm
680 uF - Electrolyte capacitor (Choose low ESR capacitor)
Volt/Amp meter to measure voltage and current

After soldered on permanent circuit board it's very simple but useful