DC-DC Polarity Inverter

This circuit generates a negative polarity voltage from a positive polarity one. This is useful for OP-amp circuits and low power audio amps where you need simultaneous +V and -V supplies from a single voltage source as a battery. Maximum input voltage is 18V, and output is up to 10W at 1 Amp. 555 based polarity inverter circuits can only provide a few milliamps of current output.

Main blocks of circuit are an oscillator stage (10KHz), a complementary power FET driver, and a capacitive charge pump. FET gates are preceded by a delay circuit to avoid simultaneous ON state of both FETs. Time constant is provided by a 470K resistor and input stray capacitance of 4011 gates (around 6pF). A 1N4148 diode cuts off FET with no delay. Schottky diodes in the charge pump provide fast switching and low forward voltage drop.

Output ripple amplitude varies with load current and has a frequency of 10KHz