Electronic – How to improve efficiency of a boost converter

boostpowerpower supply

I have built a 3V to 5V boost converter with discrete components.

L = 220uH

Vf(Diode) = 0.25V


C = 470uF

f = 47KHz

My load is a microcontroller board (M16C QSK62P Plus) that takes upto 90mA of current. I am using the PWM signal from the same microcontroller for the switching pulse for the converter.
I tested my circuit for a constant load of R = 100Ohm

I measured average current flowing through the inductor and output voltage.
From that I calculated powers Pin and Pout.

I am getting the efficiency of approx. 75%. I know that boost converters can be more efficient (90%). So, I need some suggestion about modifications in my circuit to improve the efficiency.

Best Answer

  1. Your inductor probably have high serial resistence. You might want to take lower value with thicker wire. Increase frequency if needed (but not too high, switching losses increases).

  2. Use ulta-low ESR caps, tantalum ones. Add some 0.1 + 22-66uF of ceramic cap in parralel. If frequency is high enough just leave ceramic.

  3. Implement synchronious rectification to get rid of that 0.25 vDrop (and I am not sure it's really 0.25, should be higher)

  4. Use proper MOSFET. Why take 100V part? 1.5Ohm Rds? This is not suitable for efficient DCDC. You want some 12-24V logic-level MOSFET with some 0.1 - 0.01 Rds.