Investigation Of Simulated Output Voltage Ripple Technique For Switching Mode Power Supplies

For the voltage regulator module,the light load conversion efficiency and the load transient response speed are the important indexes of its performance.Nowdays the demand of these indexes in many applications is becoming gradually strict,which makes the control technology based on the output voltage ripple more and more widely used in the voltage regulation module.Although the control technology based on output voltage ripple has the advantages of fast transient response and high light load efficiency,this kind of control technology also has the problem that the stability is easy to be affected by the output capacitance equivalent series resistance(ESR)and the problem of poor steady-state accuracy.Now the existing solution to the problem that the stability is easy to be affected by the output capacitance ESR are ramp compensation technology,the ripple of the inductor current feedback structure and capacitor current feedback technology.The ramp compensation technology leads the slope compensation voltage by sampling inductor current into a feedback control loop,but it reduces the speed of transient response and increases the dc offset of the output voltage;The inductor current ripple feedback structure leads the virtual inductor current ripple into the feedback control loop,which is easy to implement,but it is difficult to take into account the stability of the system and the steady-state deviation of the output voltage;The capacitor current feedback technology leads the capacitor current into the feedback control loop,but which has the disadvantages of the high cost on account of detecting the capacitor current and the complexity of the control circuit and the design difficulty because of the addition of error amplifier.Aiming at the stability problem of the control technology based on output voltage ripple and the deficiencies of the existing solutions,this paper proposes the solution of simulated output voltage ripple(SOVR)structure,which is applied to two typical control technology based on output voltage ripple of Constant On-Time(COT)and voltage-mode hysteresis controlled Buck converter.This paper elaborates the working principle of SOVR structure,and analyzes the operating characteristics under the inductor current continuous conduction mode(CCM)and discontinuous conduction mode(DCM).The steady performance of the existing stability improvement schemes and SOVR solutions in CCM and DCM are compared by simulation.The simulation results show that the SOVR and the inductor current ripple feedback structure can be used to solve the stability problem of the ripple control technology,but the SOVR structure has better steady-state performance.In order to verify the correctness of the theoretical analysis and simulation results,the experimental prototype is built in the laboratory.The experimental results show that the SOVR and the ripple of the inductor current feedback structure can eliminate the influence of the output capacitance ESR on the stability of the system,but the inductor current ripple feedback structure has a influence on the dc offset of the output voltage.In other words,The SOVR structure has better steady-state performance.