Describe the operation of a switched-capacitor charge doubler in AC-DC conversion.
1 Answer
A switched-capacitor charge doubler is a circuit used in AC-DC conversion to efficiently double the voltage of an incoming alternating current (AC) signal. This is accomplished by periodically switching capacitors to charge and discharge in a controlled manner. The circuit operates based on the principles of charge conservation and voltage division.
Here's a step-by-step explanation of the operation of a switched-capacitor charge doubler:
Basic Configuration: The circuit consists of two main capacitors, labeled C1 and C2. These capacitors are connected in series, with their common node acting as the output voltage node. An AC input voltage source is connected across the series combination of C1 and C2.
Clock Signal: The circuit is driven by a clock signal (square wave) with a frequency much higher than the frequency of the AC input signal. The clock signal is typically generated using an oscillator or a clock generator.
Phase 1 - Charging: During the first phase of the clock cycle, the clock signal is in a state that connects C1 to the input voltage source (V_in). This causes C1 to charge to the instantaneous voltage of V_in. At the same time, C2 is disconnected from the output node.
Phase 2 - Voltage Doubling: In the second phase of the clock cycle, the clock signal switches to the opposite state, connecting the negative terminal of C1 to the positive terminal of C2. This effectively adds the voltages across C1 and C2, doubling the voltage across C2. Since the common node of C1 and C2 is the output node, the output voltage (V_out) becomes twice the instantaneous voltage of V_in.
Phase 3 - Discharging: During the third phase of the clock cycle, C2 is disconnected from the output node, and its negative terminal is connected to ground. At the same time, C1 is connected to the output node. This causes C1 to discharge its stored charge into the output node. The voltage across C1 decreases, but the voltage across C2 remains constant due to its connection to ground.
Phase 4 - Resetting: In the fourth phase of the clock cycle, the clock signal returns to its original state, and C1 is disconnected from the output node while C2 is connected to the positive input voltage source. This prepares the capacitors for the next cycle.
Repetition: The process is repeated for every clock cycle. Over time, the output voltage settles to approximately twice the peak value of the input AC voltage. The voltage across C2 accumulates and contributes to the output voltage, effectively doubling the voltage of the AC signal.
Switched-capacitor charge doublers are used in various applications where voltage doubling is required, such as in charge pumps, voltage multipliers, and certain power supply circuits. They offer advantages such as simplicity, small footprint, and relatively high efficiency, making them suitable for low-power and portable electronics.
Here's a step-by-step explanation of the operation of a switched-capacitor charge doubler:
Basic Configuration: The circuit consists of two main capacitors, labeled C1 and C2. These capacitors are connected in series, with their common node acting as the output voltage node. An AC input voltage source is connected across the series combination of C1 and C2.
Clock Signal: The circuit is driven by a clock signal (square wave) with a frequency much higher than the frequency of the AC input signal. The clock signal is typically generated using an oscillator or a clock generator.
Phase 1 - Charging: During the first phase of the clock cycle, the clock signal is in a state that connects C1 to the input voltage source (V_in). This causes C1 to charge to the instantaneous voltage of V_in. At the same time, C2 is disconnected from the output node.
Phase 2 - Voltage Doubling: In the second phase of the clock cycle, the clock signal switches to the opposite state, connecting the negative terminal of C1 to the positive terminal of C2. This effectively adds the voltages across C1 and C2, doubling the voltage across C2. Since the common node of C1 and C2 is the output node, the output voltage (V_out) becomes twice the instantaneous voltage of V_in.
Phase 3 - Discharging: During the third phase of the clock cycle, C2 is disconnected from the output node, and its negative terminal is connected to ground. At the same time, C1 is connected to the output node. This causes C1 to discharge its stored charge into the output node. The voltage across C1 decreases, but the voltage across C2 remains constant due to its connection to ground.
Phase 4 - Resetting: In the fourth phase of the clock cycle, the clock signal returns to its original state, and C1 is disconnected from the output node while C2 is connected to the positive input voltage source. This prepares the capacitors for the next cycle.
Repetition: The process is repeated for every clock cycle. Over time, the output voltage settles to approximately twice the peak value of the input AC voltage. The voltage across C2 accumulates and contributes to the output voltage, effectively doubling the voltage of the AC signal.
Switched-capacitor charge doublers are used in various applications where voltage doubling is required, such as in charge pumps, voltage multipliers, and certain power supply circuits. They offer advantages such as simplicity, small footprint, and relatively high efficiency, making them suitable for low-power and portable electronics.