Generally speaking, in the circuit, the moment of electrification to the load, often produce a large current, so it is called impulse current. This phenomenon is reflected in capacitive loads. For example, capacitance is equivalent to short circuit at the moment of electrification, and the instantaneous current generated is theoretically infinite.

The impulse current is also known as "aperiodic transient current". In general, there are two types of waveform:

1. The current rises from zero in a very short time to the peak value, and then drops to zero in an approximate exponential law or damped sinusoidal waveform. The waveform of the impulse current is expressed in terms of the wavefront time T1 and half peak time T2, denoted as T1/T2

2. The waveform is approximately rectangular and becomes the square wave impulse current (wave).

Above we understand the simple difference between surge current and impulse current in a switching power supply from the professional definition and the cause of generation. For switching power supply in the various names of the explanation, I think it is good to grasp, do not have to memorize. After the accumulation of experience in the future study of power technology, these problems will naturally be able to understand.