With the development of electronic technology, a variety of pulse width modulation (Pulse width modulation, PWM) technologies have emerged, including: phase voltage control PWM, pulse width PWM method, random PWM, SPWM method, line voltage control PWM, etc. The pulse width PWM method used in the intelligent charger of nickel-metal hydride batteries, it uses the pulse train with the same pulse width as the PWM waveform, the frequency can be adjusted by changing the period of the pulse train, and the voltage can be adjusted by changing the pulse width or duty cycle , the voltage and frequency can be coordinated with the appropriate control method. The purpose of controlling the charging current can be achieved by adjusting the period of the PWM and the duty cycle of the PWM.

By digitally controlling analog circuits, the cost and power consumption of the system can be greatly reduced. In addition, many microcontrollers and DSPs already include a PWM controller on-chip, which makes digital control easier to implement.