Switched Capacitor Positive DC To Negative DC Voltage Inverter

The circuit is a switched capacitor positive DC to negative DC voltage inverter. When clock is high the switch Sw is in position 1, this connects the negative electrode of the flying/charge pump capacitor Ccp to ground and the positive electrode of Ccp to the positive terminal of power supply Vsp. This charges capacitor Ccp to Vsp. When clock is low the switch Sw is in position 2, this connects the positive electrode of capacitor Ccp to ground and the negative electrode of Ccp to the negative electrode of reservoir capacitor Cres. With the positive electrode of Ccp at ground, the voltage at its negative electrode is negative and therefore the negative electrode of capacitor Cres becomes charged to a negative voltage.