Abstract: A buck DC/DC switching regulator is implemented by automatically altering the modulation mode according to the load current that ranges from 0.01 to 3A.The pseudo-PFM mode is applied when duty cycle is less than 20%,and the PWM mode is selected in a range of duty cycle from 20% to 100%.The average conversion efficiency of the regulator is about 90% when the output current varies.The proposed dual-mode-control die is implemented in a 0.5μm DPDM CMOS mixed-signal process and a power p-MOSFET is used in the chip by hybrid integration.

Key words: pulse-width-modulation, pseudo-pulse-frequency-modulation, duty cycle, hybrid integrated