Presented here is the simple circuit of one boost
(step-up) converter, which can output steady
5VDC supply from a 3VDC input. This circuit can
be used to power your 5V microcontroller/similar
circuits from two standard AA cells (1.5V x2).
Schematic of 3V to 5V Booster Circuit
At the heart of the circuit is one tiny chip
HT7750A, which is a “pulse frequency
modulation” (PFM) step-up DC/DC converter with
high efficiency and low ripple. The chip features
extremely low start-up voltage and high output
voltage accuracy.
They require only three external components to
provide a fixed output voltage of 5.0V. CMOS
technology ensures ultra low supply current and
makes them ideal for battery-operated
applications powered from one or more cells.
HT7750A consists of an oscillator, a PFM control
circuit, a driver transistor, a reference voltage unit,
and a high speed comparator.
If you do not have a LCR meter the inductive part
(L1) of the circuit is a bit more complicated to
make! Capacitors (C1 & C2) also recommended
by the manufacturer for this circuit is a bit hard to
get, I have used tantalum types recovered from a
discarded smps circuit board. Last but not least,
say that the diode (D1) has to be a fast, not worth
as the 1N400X rectifiers, the 1N5817 is
recommended schottky type, characterized by
high response time and low internal resistance,
which is what ideal for this type of boost-
converter circuits.
In my prototype, I have used a “home-made”
100uH inductor as L1. I wound near 8 turns of 0. 3
mm enamelled copper wire on a small toroidal
core, lifted from an old CFL circuit board.Volts DC to 5 Volts DC
Converter
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