The invention discloses a method and circuit for converting alternating-current 
sine wave signals into direct-current step wave signals. The method comprises the steps that (1) the alternating-current 
sine wave signals are rectified into direct-current head signals; (2) the 
head wave signals are transmitted into a plurality of 
voltage adjusting devices with different amplitudes, and are divided into 
multiple stages of 
voltage signals; (3) the 
voltage signals are respectively transmitted into a 
constant current device, voltage 
signal waves form flat-topped 
waves, all flat-topped wave voltage signals are connected in sequence, and the direct-current step wave signals are obtained. The circuit comprises a 
rectifier bridge circuit, the voltage adjusting devices and a plurality of 
constant current control devices, the 
rectifier bridge circuit rectifies the alternating-current 
sine wave signals into the direct-current 
head wave signals, the voltage adjusting devices are connected in parallel to form a network, the voltage adjusting set values of the voltage adjusting devices are different, the direct-current 
head wave signals are divided into the multi-stage signals with different amplitudes, the number of the 
constant current control devices is equal to that of the voltage adjusting devices, the constant current control devices are correspondingly connected with the voltage adjusting devices respectively, and used for controlling the currents of the voltage adjusting devices to be kept constant, and the output signals of the voltages adjusting devices are made to be the flat-topped 
waves. All the flat-topped wave signals are connected in sequence, and the direct-current step wave signals are formed.