Charge Pump Calculator

A charge pump is a switched capacitor circuit that uses capacitors as energy storage elements to generate higher or inverted voltages from a lower supply voltage. It works by alternately charging and discharging flying capacitors through switches to transfer charge to an output capacitor.

The number of stages determines the voltage multiplication factor. Use fewer stages for higher efficiency and lower output impedance, or more stages for higher voltage gain. Consider that each additional stage reduces efficiency due to parasitic losses.

Key factors include switching frequency, capacitor values, switch resistance, load current, and number of stages. Higher switching frequencies and larger capacitors improve efficiency, while switch resistance and heavy loads reduce it.

Flying capacitor value affects output ripple and efficiency. Larger capacitors reduce ripple and improve efficiency but increase cost and size. Start with 10-50μF and adjust based on your ripple and efficiency requirements.

Output voltage drops due to parasitic resistances, finite capacitor values, and load current. The actual output is always less than the ideal multiplication factor due to these real-world limitations.

Optimal frequency balances efficiency and component size. Higher frequencies allow smaller capacitors but increase switching losses. Typical ranges are 50kHz to 1MHz, with 100-500kHz being common for most applications.

Higher load currents cause larger voltage drops and reduced efficiency due to the finite charge transfer capability and parasitic resistances. The output voltage regulation degrades with increasing load current.

Charge pumps offer smaller size, no electromagnetic interference, lower cost, and easier PCB layout compared to inductor-based converters. However, they typically have lower efficiency and higher output impedance.