cold start

Some power devices experience a temporary current greater than the specified level, known as inrush current, during startup, which requires countermeasures. One simple and cost-effective method to suppress inrush current is to insert a resistor, but it has the disadvantage of reduced efficiency due to resistor loss. As a solution to this drawback, a cold start method uses a thermistor with the characteristic that the resistance decreases as the temperature rises. In a cold start, inrush current is suppressed at startup by the high resistance due to low temperature, and as the temperature rises to operating levels, the resistance decreases, reducing losses. However, if there is a short power outage after reaching the operating temperature and the power is restored immediately after shutdown, there is no cooling time for the thermistor, resulting in a large inrush current that can adversely affect the equipment.