Describe the operation of a switched-capacitor inverting charge pump for AC-DC conversion.
1 Answer
A switched-capacitor inverting charge pump is a type of circuit used for AC-DC conversion, specifically for generating a negative output voltage from a positive input voltage. It's commonly used in applications where a negative voltage source is required, such as in certain types of amplifiers, analog circuits, and display drivers.
The operation of a switched-capacitor inverting charge pump involves a series of capacitors, switches, and voltage inverters. The basic principle behind the circuit is to alternate between charging and discharging capacitors in a specific sequence to create a voltage inversion.
Here's a step-by-step description of how the circuit operates:
Initial State: The circuit starts in an initial state where all the switches are configured properly. Let's assume the input voltage (V_in) is positive, and the desired negative output voltage (V_out) is generated across a load resistor.
Phase 1 - Charging Phase: During this phase, the switches are set such that the input voltage V_in charges a capacitor (C1) connected to ground. The voltage across C1 gradually increases as it accumulates charge. The other capacitors in the circuit remain in a disconnected state.
Phase 2 - Switching Phase: The switches are then toggled. The charged capacitor C1 is now connected to an inverting voltage amplifier or inverter. This inverter inverts the voltage across C1, creating a negative voltage with respect to ground. The switched capacitors are essentially rearranged to form a series of charge-sharing paths.
Phase 3 - Discharging Phase: The inverted voltage is now used to discharge another capacitor (C2). The other capacitors remain disconnected. The voltage across C2 decreases as it releases its stored charge into the load and other connected components.
Phase 4 - Second Switching Phase: The switches are toggled again. The charged capacitor C2 is now connected to the inverter, creating a more negative voltage across it.
Repeat: Steps 2 through 5 are repeated in a cyclical manner, with the sequence of charging, inverting, discharging, and inverting again. This process continues to accumulate more negative charge on the capacitors and generate a higher negative output voltage across the load resistor.
It's important to note that the actual sequence and connections of the switches can vary based on the specific design of the circuit. Additionally, parasitic capacitances, resistances, and switching losses need to be carefully considered during the design process to ensure the circuit's efficiency and performance.
Switched-capacitor charge pumps, including inverting ones, are used in applications where efficiency isn't the main concern, and compact size, simplicity, and low-cost solutions are more important. They can provide a relatively simple way to generate negative voltage levels from positive inputs without requiring the use of transformers or more complex circuitry.
The operation of a switched-capacitor inverting charge pump involves a series of capacitors, switches, and voltage inverters. The basic principle behind the circuit is to alternate between charging and discharging capacitors in a specific sequence to create a voltage inversion.
Here's a step-by-step description of how the circuit operates:
Initial State: The circuit starts in an initial state where all the switches are configured properly. Let's assume the input voltage (V_in) is positive, and the desired negative output voltage (V_out) is generated across a load resistor.
Phase 1 - Charging Phase: During this phase, the switches are set such that the input voltage V_in charges a capacitor (C1) connected to ground. The voltage across C1 gradually increases as it accumulates charge. The other capacitors in the circuit remain in a disconnected state.
Phase 2 - Switching Phase: The switches are then toggled. The charged capacitor C1 is now connected to an inverting voltage amplifier or inverter. This inverter inverts the voltage across C1, creating a negative voltage with respect to ground. The switched capacitors are essentially rearranged to form a series of charge-sharing paths.
Phase 3 - Discharging Phase: The inverted voltage is now used to discharge another capacitor (C2). The other capacitors remain disconnected. The voltage across C2 decreases as it releases its stored charge into the load and other connected components.
Phase 4 - Second Switching Phase: The switches are toggled again. The charged capacitor C2 is now connected to the inverter, creating a more negative voltage across it.
Repeat: Steps 2 through 5 are repeated in a cyclical manner, with the sequence of charging, inverting, discharging, and inverting again. This process continues to accumulate more negative charge on the capacitors and generate a higher negative output voltage across the load resistor.
It's important to note that the actual sequence and connections of the switches can vary based on the specific design of the circuit. Additionally, parasitic capacitances, resistances, and switching losses need to be carefully considered during the design process to ensure the circuit's efficiency and performance.
Switched-capacitor charge pumps, including inverting ones, are used in applications where efficiency isn't the main concern, and compact size, simplicity, and low-cost solutions are more important. They can provide a relatively simple way to generate negative voltage levels from positive inputs without requiring the use of transformers or more complex circuitry.