US Patent 7427855 Circuit for measuring inrush current

A circuit for testing an inrush current of a power supply includes a rectifier (10), a capacitor (30), and an ammeter (90). The rectifier includes input terminals (1) adapted to connect with an AC supply (Vin), and output terminals (3) adapted to supply a direct voltage. The capacitor is connected in parallel to the output terminals of the rectifier. The ammeter is connected between the capacitor and the power supply. The capacitor is charged by the AC supply via the rectifier. When the voltage of the capacitor reaches a pre-determined value, the capacitor supplies energy to the power supply, and the ammeter measures the magnitude of the inrush current.