Research On Hysteresis Control Techniques Of Voltage Regulation Module(VRM)

The thesis briefly introduces the concept and the characteristics of the Voltage Regulation Module (VRM). The techniques for improving the transient response speed of VRM are surveied. Then two hysteresis control methods, voltage hysteresis control and capacitor current square hysteresis control, with fast transient response are studied in detailed, which improve the line and load transient response characteristics by adopting capacitor current.The steady state characteristics of these control techniques have been studied in this thesis. The switch frequency, voltage offset , voltage ripple at both continueous conduction mode(CCM) and discontinueous conduction mode(DCM) are derived. Therefore, we can analyze them quant ificationally.The dynamic characteristics of these two control techniques have also been studied. The voltage offset and its regulation time caused by load current variation are derived. The influence of circuit parameter on the system stability is analyzed. The reason of fast transient response with input voltage variation is stated.The comparison between the transient behaviors of voltage hysteresis control technique and V2 hysteresis control technique are performed, from which we get the conclusion that voltage hysteresis control technique has faster teansient response speed than V2 hysteresis control technique. The comparison between the transient behavior of capacitor current square hysteresis control technique and voltage hysteresis control technique are also performed, from which we can know that when ESR of capacitor is small, capacitor current square hysteresis control technique has faster transient response speed than voltage hysteresis control technique, while when ESR is larger, voltage hysteresis control technique has faster trasient response speed than capacitorcurrent square hysteresis control technique.The experimental results verify the analysis and simulation results.