A switched-capacitor voltage doubler is a type of electronic circuit used for DC voltage multiplication, specifically in AC-DC conversion. It is a popular choice for generating a higher DC voltage from a lower AC voltage source, commonly found in low-power applications and voltage boosters. The basic principle behind its operation involves using a network of capacitors and switches to alternate between charging and discharging phases, effectively doubling the input voltage.
Here's a step-by-step description of how a switched-capacitor voltage doubler operates in AC-DC conversion:
Initial State: The circuit begins with an input AC voltage source. This AC voltage is typically first rectified to convert it into a pulsating DC voltage.
Charging Phase (Switch Closed):
During the charging phase, the switches in the circuit are closed.
Capacitors are connected in series with the input voltage source. Each capacitor effectively divides the input voltage in half.
The capacitors start to charge up to their respective voltages, which are half of the input voltage.
Because the capacitors are in series, their voltages add up, resulting in a net voltage across them that is equal to the input voltage.
Switching Phase (Switch Open):
After the capacitors are charged, the switches are opened.
The charged capacitors are now isolated from the input source.
The capacitors are connected in parallel, effectively adding their charges together.
Discharging Phase (Switch Closed):
During the discharging phase, the switches are closed again.
The combined charge stored in the capacitors is transferred to the output load or storage capacitor.
Since the capacitors are in parallel, their charges combine, resulting in an output voltage that is double the input voltage.
Output Filtering and Regulation:
The output of the switched-capacitor voltage doubler may be further filtered and regulated to smooth out voltage fluctuations and provide a stable DC voltage to the load.
Additional components, such as diodes and smoothing capacitors, can be added to improve the output quality.
It's important to note that while the switched-capacitor voltage doubler can double the input voltage, it does so at the expense of reduced current capability. The output current is limited by the switching frequency, the capacitance values, and the efficiency of the switches. As a result, switched-capacitor voltage doublers are best suited for low-power applications where efficiency and high current output are not critical.
Overall, the switched-capacitor voltage doubler offers a simple and compact solution for AC-DC conversion, particularly when a moderate voltage boost is required in low-power scenarios.