Shang-Chin Yen

A High-Efficiency AC-to-DC Adaptor With a Low Standby Power Consumption

A two-stage burst mode control scheme for an AC-to-DC adaptor is proposed in this paper. An upper limit for the output voltage is set to turn off both AC/DC and DC/DC controllers at no load. The burst-mode operations of the DC/DC and the AC/DC converters are in turn enabled when reaching the lower limit of the output voltage. Load analysis at standby mode is performed. A 50-mW no-load power loss is observed on an 80 W/12 V prototype adaptor.

A High-Efficiency AC-to-DC Adaptor with a Low Standby Power Consumption

A two-stage burst mode control scheme for a high-efficiency AC-to-DC adaptor is proposed in this paper. The boost power factor corrector (PFC) is operated at the discontinuous conduction mode (DCM). The half-bridge series-parallel resonant converter (HB-SPRC) is adopted as the DC/DC topology. An upper limit for the output voltage is set to turn off both two control ICs at either a light load or no load. One lower limit for the output voltage and a delay signal in turn enable the burst modes of the HB-SPRC and the DCM PFC. At light loads, the HB-SPRC provides higher voltage gains to store more energy and to shorten the burst mode period. Thus the no-load or standby power consumption may be reduced. An average active-mode efficiency of 90 % and a 50 mW no-load power loss are observed on a 80 W/12 V prototype adaptor.

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.

Analysis and Design of a Double-Output Series-Resonant DC–DC Converter

This paper presents a method for designing the ratio of the feedback weighting gains and the transformer secondary turns ratio of a double-output series-resonant dc-dc converter. The equivalent circuit models of the secondaries including the circuit parasitics are examined. The feedback line and load lines are drawn on a rectangular-coordinated output-voltage plane to check if the output specifications can be met. Three load ranges are classified. Then the ratio of the weighted feedback gains and the turns ratio of the transformer secondaries are determined. Design procedures are addressed. Satisfactory results on a double-output 180-W prototype are demonstrated and verified

Linearization of the control-to-output transfer function for a PWM buck-boost converter

A new method for linearizing the control-to-output transfer function of a PWM buck-boost converter is presented in this paper. The DC and the small-signal characteristics are derived. A compensating signal relating to the inverse of the nonlinear term appeared in the control-to-output transfer function is produced from the duty ratio, and then fed into the feedback loop. Experimental results show that the linearity is retained between the duty ratio and the output voltage by adopting the proposed feedback scheme.

On lessening the cross regulation in a forward converter

A new method is proposed in this paper to improve the cross regulation in a multioutput forward converter. An objective function is determined for each of the multiple DC outputs to track its reference. The error of each output is maintained within an acceptable level. The presented control scheme which minimizes the objective function can be applied to the multioutput system without a dominant load. Experiments are performed to show that there exists a duty cycle satisfying the defined objective function.

A High-Voltage Input Backlight Module Driver for Multi-Lamp LCD Panels

A high-voltage DC input backlight module driver for multi-lamp LCD panels is presented in this paper. The 400-V DC output of a power factor corrector (PFC) is directly coupled to a class-D resonant inverter. Thus the requirement of a buck converter conventionally adopted to provide a low input voltage for the DC/AC inverter is eliminated. Also a single transformer with multiple secondaries is utilized to drive multiple lamps. The proposed backlight module driver features less circuit components, a lower cost and a higher efficiency. Design considerations are discussed and design procedures are derived. Simulations and experimental results confirm with the theoretical analysis

Analysis and 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.

Input current harmonic analysis and filter capacitor design for discontinuous conduction mode boost rectifiers

The input current harmonic analysis using discrete waveform modeling for discontinuous conduction mode boost rectifiers is presented in this paper. The equations describing the input current waveforms and the current harmonics can be expressed as functions of the circuit parameters, including the duty ratio, switching frequency, input inductance and the load resistance. The procedures for estimating the input filter capacitance are also established. Experimental results show good conformation with the theoretical data.