Basics on Constant Voltage CV and Constant Current CC Part 1

Constant Voltage CV and Constant Current CC
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A basic introduction on constant voltage and constant current modes of the power supply. An ideal Constant Voltage source has zero output impedance at all frequencies. The voltage output is represented as a horizontal line parallel to the x-axis on V/I plot. e.g. voltage is constant regardless of current. Likewise, an ideal current source would have infinite output impedance and would produce the same current regardless of voltage. The typical power supply will act primary as a Constant Voltage source up to the current limit. When the power supply outputs current at its limit it shifts to Constant Current mode.

Most of our power supplies can also act as a low frequency Current Source in CC mode. It is common for a power supply to have a large output capacitance which provides a very stable output voltage in Constant Voltage Mode. This prevents the power supply from having a good Constant Current mode of operation. As you go up in frequency the output capacitor makes the output impedance lower. A Constant Current source should have high output impedance at all frequencies.

The reason there are so few true Constant Current sources is that equipment typically uses a constant input voltage. Our solar array simulator is an example of a supply that acts primarily as a current source and we also have a family of supplies the N678XA that do a good job of behaving as a current source. LED lighting is another technologies that can benefit from a constant current source. LEDs are driven with a current as the means of regulating the amount of light output not voltage.