A switched-capacitor voltage quadrupler is a type of circuit used for DC voltage multiplication from an AC input source. It is a component commonly employed in various electronic systems, such as power supplies, energy harvesting circuits, and charge pumps. The primary purpose of a switched-capacitor voltage quadrupler is to increase the voltage level of a DC signal, making it suitable for applications requiring higher voltages.
Here's how a switched-capacitor voltage quadrupler operates in AC-DC conversion:
Basic Components: The core components of a switched-capacitor voltage quadrupler typically include capacitors, switches (usually implemented using transistors), and diodes. The circuit can be constructed using multiple stages, each consisting of these components.
Clock Signal: The operation of the quadrupler is controlled by a clock signal, which determines when the switches are turned on and off. This clock signal is usually generated by an external oscillator or a clock generator.
Switching Action: The switches in the circuit alternate between two states: charging and discharging. During the charging phase, a switch connects one side of a capacitor to the input voltage source, and during the discharging phase, the switch connects the other side of the capacitor to the output.
Charge Transfer: When the switch is closed during the charging phase, the capacitor accumulates charge from the input source. Since the switch is closed, the voltage across the capacitor is approximately the same as the input voltage.
Voltage Doubling: During the discharging phase, the switch is opened, and the capacitor is connected to the output through a diode. The capacitor's stored charge is transferred to the output through the diode. Due to the presence of the diode, the voltage across the capacitor adds to the output voltage, effectively doubling it.
Stages and Voltage Multiplication: To achieve voltage multiplication, multiple stages of capacitors and switches can be cascaded. In each stage, the voltage across the capacitor is doubled during each discharge phase, resulting in an accumulated multiplication effect. A voltage quadrupler uses four stages to achieve a four-fold increase in the output voltage compared to the input.
Voltage Ripple: One of the challenges in switched-capacitor voltage multipliers is voltage ripple. The voltage across the capacitors can experience fluctuations due to imperfections in components and the switching process. This ripple can be reduced by using larger capacitance values, optimizing switching timings, and employing regulation techniques.
Efficiency: The efficiency of a switched-capacitor voltage quadrupler depends on factors like component quality, switching losses, and voltage ripple. While switched-capacitor voltage multipliers are generally not as efficient as some other voltage multiplication methods, they are compact, relatively simple, and can be suitable for applications where higher efficiency is not the primary concern.
In summary, a switched-capacitor voltage quadrupler is a circuit that uses capacitors, switches, and diodes to multiply the input voltage by accumulating and transferring charge through multiple stages. It provides a simple way to increase DC voltage levels for various applications.