A switched-capacitor voltage multiplier circuit is a type of circuit used for DC voltage multiplication and conversion from AC to DC. It's commonly used in low-power applications where high voltage levels are needed, such as in energy harvesting circuits, charge pumps, and some types of electronic displays.
The basic principle behind a switched-capacitor voltage multiplier circuit is to use a series of capacitors, switches, and diodes to create a voltage multiplication effect. The circuit operates in a cyclic manner, with each cycle consisting of several phases:
Charging Phase: During this phase, the switches are configured in such a way that the capacitors are connected in parallel to the input AC voltage source. As the capacitors charge up, they accumulate charge and store energy.
Switching Phase 1: The switches are then toggled so that the charged capacitors are connected in series. This effectively adds their voltages together. However, since the capacitors are connected in series, the total charge remains constant, but the voltage is multiplied by the number of capacitors in the series.
Discharging Phase: The charged capacitors are now connected in series with a load. The diodes prevent the capacitors from discharging back into the circuit. The load draws current from the capacitors, and the capacitors gradually discharge while providing power to the load.
Switching Phase 2: The switches are toggled again, this time to return the capacitors to their parallel configuration. The capacitors that were discharged in the previous phase are now recharged using the input AC voltage source, while the other set of capacitors is connected in series to be used for the next multiplication cycle.
By repeating these phases in a cyclic manner, the voltage across the capacitors is multiplied with each cycle. The voltage multiplication factor is determined by the number of capacitors used in each phase.
Keep in mind that while switched-capacitor voltage multipliers are useful for voltage conversion, they typically have limitations in terms of current handling capacity and efficiency. They are more suitable for low-power applications where high voltage levels are needed but not necessarily high current levels.
Overall, switched-capacitor voltage multipliers offer a simple and compact solution for voltage multiplication in AC-DC conversion scenarios, especially in situations where traditional transformers might be too bulky or impractical.