Designand Implementation Of A DC/DC Chip With The PWM And PSM Control Mode

In modern society, there is a close relationship between huamn’s lift and varietiesof electronic devices. The increasing requirement of electronic devices, and therequirement of high efficiency, low power dissipation, high load capacity is the motivepower of the developing of the power management chip market. In recent years, themarket of the power management is thriving under geat sustain of the government.Howto meet the varieties of requirements of the market and accomplish the reasonable,smartcontrol about the power supply a new challenge to the power designer.This paper design a synchronous rectified buck DC/DC chip adapted the PWM andPSM control mode.This chip integrated voltage pre-regulation, bandgap, error amplifier,PWMcomparator, oscillator,over current protect and over temperature circuit. The traditionlpeak current mode adopts the PWM control mode, which has a lower efficiency with alight load. The chip adopts PWM and PSM control mode to improve the efficiency.That is, the part works at the PWM control mode when the load is heavy and works atPSM control mode when the load is light. Thus the chip will maintain a good efficiencyat all load. At the same time, A self-adjustable slope compensation circuit is present inthis paper. Though detecting the variation of the change of the duty cycle, the circuitcan adjust the slope compensation automatically.Thus,the influence of the slopecompensation over the maximum current ability is reduced by substituting a currentlimit comparator for error voltage clamping.Based on0.18um processing, chip design, simulation, and layout design have beenaccomplished by using Cadence.4V to24V DC input, maximum2A load, the highestefficiency is up to95%.