Sheng-Yuan Ou

Switching-Frequency Control for Regulated Discontinuous-Conduction-Mode Boost Rectifiers

A novel switching-frequency control method for regulated one-switch boost rectifiers operating at the boundary of discontinuous and continuous conduction modes is presented in this paper. To obtain a source current with the least amount of low-order harmonics, the duty cycle within a switching period is proportional to the ratio of the instantaneous value of the source voltage to the output voltage. According to the voltage gain analysis, the output voltage can be regulated by adjusting the switching frequency. Small-signal modeling is performed to facilitate the design process. The proposed control scheme features advantages such as higher input power factor and higher regulated output voltage compared to the traditional discontinuous conduction control with a fixed switching frequency and a constant duty cycle. Any well-developed commercial pulsewidth-modulation control integrated circuit can be adopted with only a minor modification. Experimental results show good conformation with the theoretical analysis

The analysis and elimination of voltage imbalance between the split capacitors in half-bridge boost rectifiers

The voltage imbalance between the split capacitors in a half-bridge boost rectifier is reviewed in this paper. It can be proven that the optimal compensation strategy is to add only a DC component in the source current. Also the effect of imbalance elimination control loop to the input power factor are studied. The analytical results are verified through experiments.

Switching-frequency control for regulated discontinuous conduction mode boost rectifiers

A novel switching-frequency control method for regulated 1-switch boost rectifiers operating at the boundary of the discontinuous and continuous conduction modes is presented in this paper. To obtain a source current with least amount of low-order harmonics, the duty cycle within a switching period is proportional to the ratio of the instantaneous value of the source voltage to the output voltage. According to the large signal analysis, the output voltage can be regulated by adjusting the switching frequency. Small signal modelling is performed to facilitate the design process. The proposed control scheme features advantages such as a higher input power factor and a higher regulated output voltage compared to the traditional discontinuous conduction control with a fixed switching frequency and a constant duty cycle. Any well-developed commercial PWM control IC can be adopted with only a minor modification. Experimental results show good conformation with the theoretical analysis.

On evaluating the current distortion of the single-phase switch-mode rectifiers with current slope maps

This paper presents a simple way to evaluate the distortion level of the input current for single-phase switch-mode rectifiers (SMRs). Based on the possible conducting paths of various topologies of SMRs, slopes of the input and command currents are defined to form a slope map. By comparing the defined current slopes, the causes of current distortion are examined. Distorted waveforms of the input currents under hysteresis control are reviewed and classified into three types. Design criteria for the circuit parameters are also studied to reduce the current distortion level. Simulations and experiments are performed and the results show strong conformity to the theoretical analysis.

Constant-switching-frequency control of switch-mode rectifiers without current sensors

A novel control scheme for single-phase switch-mode rectifiers is presented in this letter. By utilizing the constant-switching-frequency pulsewidth modulation scheme, the duty ratios of the switches in each switching cycle are determined based on the available input current slopes. No current sensors are required. The simulations and experiments show satisfactory results.

Improved control-to-output characteristics of a PWM buck-boost converter

An indirect control variable for improving the control-to-output characteristics of a Pulse Width Modulation (PWM) buck-boost converter is introduced in this letter. The voltage gain and the small-signal model of the buck-boost converter are reviewed. The actual voltage command at one input of the PWM comparator is from the proposed indirect control variable and the peak value of the high-frequency PWM carrier. The resulted voltage gain function appears proportional to this indirect control command. Also the dependence of the DC gain of the control-to-output transfer function on the duty cycle is eliminated. Experimental results conform well to the theoretical analysis. Copyright

Criteria for setting the reference DC voltage of an active power line conditioner

A new strategy for setting the reference DC voltage of an active power line conditioner (APLC) is proposed in this paper. By measuring the peak slope of the command for the compensating current within a defined load range, an optimal value for the reference DC voltage can be determined based on a trade-off between an undistorted input current and a minimum switching loss.

Design of a two‐output forward converter with an output voltage objective function

A new method is proposed in this paper to distribute the steady-state errors of the output voltages in a two-output forward converter. The cross regulation among the two output voltages are described in terms of the circuit parameters. An objective function is formed for each of the two dc outputs to track its reference within the specified error. The weighting feedback gains of the two output voltages and the duty cycle range can be determined by the presented control scheme which optimizes the objective function. The proposed method is especially suitable for a two-output system without a dominant load. Experiments on a prototype are performed to show that there exists a duty cycle range and a set of weighted feedback gains satisfying the defined objective function.

Coupling analysis of a three-phase power-factor corrector composed of three single-phase modules

The coupling behavior, during the turn-off intervals, of the main switches in a three-phase boost power-factor corrector composed of three single-phase modules is analyzed by the authors in this paper. The rejoining of the split inductor currents of the same phase is also proven theoretically and verified with experiments.

A novel variable frequency modulation technique to improve light-load efficiency for multiphase synchronous rectified VRM

A novel variable frequency modulation technique for multiphase synchronous rectified voltage regulator module (VRM) is proposed in this paper. The proposed technique provides zero voltage switching (ZVS) for high-side and low-side power switches under both light- and heavy-load conditions, thereby increasing the efficiency as compared to the conventional approach. The dependency of switching frequency on the load condition for the proposed modulation technique and the related conduction loss are analyzed. It will be shown that the frequency increases for light-load condition in order to retain ZVS and decrease the conduction loss. Although the switching loss will slightly increase due to the increase of switching frequency, the analysis and experimental results will show that the contribution of frequency increasing can cover this additional loss. Experimental results derived from a single-phase and an eight-phase synchronous rectified VRM show that the proposed modulation technique is superior to the conventional one and compared to conventional constant switching frequency techniques with 250 and 550thinspacekHz, the efficiency can be increased up to 17 and 5% for single-phase VRM and 8 and 4% for eight-phase VRM under various load conditions. Even an off-the-shelf controller with an additional simple and cheap control circuit comprising one switch, two operational amplifiers and several resistors is used to realize the proposed technique, that is, a very low cost and small circuitry is attached to gain the significant benefit. Copyright