A state monitoring circuit is disclosed for monitoring health states of N energy storage capacitors in an energy-storage capacitor device, the energy-storage capacitor device including N channels, and each channel comprising one energy storage capacitor, where the state monitoring circuit is configured to: disconnect first terminals of the N energy storage capacitors from the energy-storage capacitor device one by one; and determine whether each of the N energy storage capacitors is abnormal in accordance with a voltage at the first terminal of a corresponding one of the energy storage capacitors, where N is a positive integer.