Figure 17. Constant Voltage/Constant Current CV/CC Power Supply
Figure 18 illustrates the output characteristic of an ideal CV/CC power supply. With no load attached (RL= ∞ ), IOUT= 0, and EOUT= ES, the front panel voltage control setting. When a load resistance is applied to the output terminals of the power supply, the output current increases, while the output voltage remains constant; point D thus represents a typical constant voltage operating point. Further decreases in load resistance are accompanied by further increases in IOUT with no change in the output voltage until the output reaches Is, a value equal to the front panel current control setting. At this point the supply automatically changes its mode of operation and becomes a constant current source; still further decreases in the value of load resistance are accompanied by a drop in output voltage with no accompanying change in the output current value. Thus, point B represents a typical constant current operating point. Still further decreases in the load resistance result in output voltage decreases with no change in output current, until finally, with a short circuit across the output load terminals. IOUT = Is and EOUT = 0.
By gradually changing the load resistance from a short circuit to an open circuit the operating locus of Figure 18 will be traversed in the opposite direction.
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