August 1, 1997

Battery simulator provides current limiting

Hernán Tacca, University of Buenos Aires, Argentina

A constant-voltage active load can perform as a battery during the charge cycle (Figure 1). You can set the load voltage from 5 to 35V by using potentiometer P_V and thus can simulate batteries ranging from 6 to 32V. In testing a battery charger (during design or for calibration purposes), a current-limiting function is a desirable feature; you enable this protection feature by opening S₁. The LED lights if the current reaches the limit. This feature lets you know when the circuit goes out of its constant-voltage operating mode.

To simulate the dynamic behavior of a battery, you can connect several electrolytic capacitors. With the addition of these capacitors, current pulses can flow bidirectionally between the load and the battery charger. In some cases, a large capacitive load could cause oscillations, making it difficult to provide loop compensation for stable closed-loop operation. In case of such instability, switch S₂ provides capacitor disconnection. If you encounter closed-loop compensation problems, try to compensate without using capacitors. (DI #2065)

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