Introduction: 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.
Step 1: 10 Ohm / 2W Resistor Burning From 10Volts 1Amp Output (10W) of Inverter Circuit
Step 2: Circuit Diagram
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.
Step 3: Circuit Operation Details
Step 4: Charge Pump Operation
Step 5: Charge Pump Animation
Step 6: Output Ripple
Output ripple amplitude varies with load current and has a frequency of 10KHz