Tzu-Herng Song

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

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

Design and Implementation of a Single-Stage High-Frequency HID Lamp Electronic Ballast

We present a single-stage electronic ballast with a high power factor feature for driving high-intensity discharge (HID) lamps. A new frequency-modulation technique is proposed to eliminate the acoustic resonance problem in HID lamps under high-frequency operation. The proposed method has the merits of simple circuit and low cost; thus, it is suitable for use in commercial applications. The conducted emission caused by the high-frequency electronic ballast can be also effectively reduced. The operating principles and design considerations of the proposed electronic ballast are analyzed and discussed in detail. A 35-W laboratory prototype is designed and implemented. Simulation and experimental waveforms are given to verify the feasibility of the proposed method. The results are satisfactory.

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

A software-based CM and DM measurement system for the conducted EMI

In this paper, a software-based common mode (CM) and differential mode (DM) measurement system for the conducted EMI is presented. A user friendly interface is developed to provide an effective communication between the user and the system. The panel of the spectrum analyzer can be displayed on the PC screen and adjusted with the keyboard or the mouse by the user. Either CM or DM noise can be calculated from the other measured result. Experiments show that the proposed system works well.

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.

Elimination of voltage imbalance between the split capacitors in three-phase half-bridge switch-mode rectifiers

The voltage imbalance between the split capacitors in three-phase half-bridge switch-mode rectifiers is observed and the elimination of the imbalance is proposed in this paper. It is found that adding a DC bias to the source current of each phase can resolve the voltage imbalance problem. The elimination strategies are developed by thoroughly analyzing all possible conducting paths of the DC bias currents and their effect on the voltage imbalance. The proposed elimination control loop is implemented on a prototype system and the experiments show satisfactory results.

On approximating the frequency responses of the common-mode electromagnetic interference noise source

The frequency responses of the common-mode (CM) electromagnetic interference (EMI) noise source for a switch-mode power supply is approximated in this paper. The amplitude of the equivalent Norton current source and the shunt admittance for the CM noise model are obtained by numerical analysis. The calculated frequency responses are valid almost in the entire measured frequency range. The CM filter design can be facilitated by using the obtained frequency responses. It is verified that the results are satisfactory.

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.

An improved circuit arrangement for the ultrasonic level indicator controller

This paper presents a new controller circuit arrangement for the ultrasonic level indicators widely used in the chemical and process plants. A few measuring functions previously performed by the analog circuits are instead realized by a software-based controller incorporated in the microprocessor. The cost and complexity of the controller circuit are reduced. Also a power-saving strategy is proposed and applied to the A/D converter such that the A/D converter only operates when required. Satisfactory experimental results confirm the effectiveness of the proposed circuit arrangement.

Large signal analysis using discrete waveform modeling for discontinuous conduction mode boost rectifiers

A large signal analysis using discrete waveform modeling for discontinuous conduction mode boost rectifiers is presented in this paper. The conduction boundary of the rectifier operation is discussed. The voltage gain and the power factor are expressed as functions of the circuit parameters, including the duty ratio, switching frequency, input inductance and the load resistance. Experimental results show good conformation with the theoretical data.