a first detection circuit, coupled to the power device, and configured to detect a first electrical parameter of the power device based on an i-th level short circuit time;

a second detection circuit, coupled to the power device, and configured to detect a second electrical parameter of the power device so as to generate an i-th level detection signal based on the i-th level short circuit time; and

a control circuit, coupled to the first detection circuit and the second detection circuit, and configured to generate an i-th level heat estimation value to determine whether the power device is damaged according to the first electrical parameter and to determine whether the power device is abnormal in operation according to the i-th level detection signal,

wherein the control circuit records the i-th level heat estimation value and the i-th level short circuit time when the power device is determined to be damaged and abnormal in operation, the control circuit adjusts the i-th level short circuit time to an i+1-th level short circuit time when the power device is determined to be non-damaged and not abnormal in operation, and an i is a non-negative integer.