PWM/PDM double-mode modulation selective circuit and double-mode modulation method

The invention discloses a PWM/PDM double-mode modulation selecting circuit and a double-mode modulation method, which mainly solves the problem that the prior DC/DC converter is not high in average conversion efficiency within a heavy-load range. The whole circuit comprises a bias circuit, a band gap reference voltage source, an error amplifier, an isolation common-source follower, an oscillator, an integrator, a mode judgment comparator, a control comparator, a latch and a driving buffer, wherein the mode judgment comparator and the latch are connected between the output end of the error amplifier and the control end of the oscillator; the magnitude comparison of load current is converted into voltage comparison through the relation of duty cycle and triangular wave; and when the load current is larger, the circuit selects a PWM modulation mode otherwise the circuit selects a PDM modulation mode when the load current is smaller. Under the condition of guaranteeing the performance of the DC/DC converter, the invention improves the average conversion efficiency in a load change interval, and is applicable to the DC/DC switch converter with great load current change, low requirement on circuit volume and high requirement on conversion efficiency.