Yan-Pei Wu

A procedure for designing EMI filters for AC line applications

A procedure for designing AC power line EMI filters is presented. This procedure is based on the analysis of conducted EMI problems and the use of a noise separator. Design examples are given, and results are experimentally verified.

A cold-cathode fluorescent lamp driver circuit with synchronous primary-side dimming control

A novel synchronous primary-side dimming control scheme is proposed and tested for a cold-cathode fluorescent lamp (CCFL) driver circuit for liquid crystal display (LCD) backlight illumination display applications. This new control scheme features high efficiency, even-dimming sensitive adjustment, even-brightness control for a two-lamp system, less lamp flickering problems, stable feedback control and simplicity. An analysis of the circuit is given, from which a design example is presented.

Control-loop modeling of multiple-output feedback of forward converters

A small-signal model is developed for the forward converter with multioutput feedback. In the basis of the model developed, feedback compensation schemes are proposed to stabilize the circuit. The closed-loop circuit performances such as line regulation, cross regulation, and load regulation, are expressed analytically in terms of multiple-loop gains of the system. >

Closed-form expressions for the frequency-domain model of the series resonant converter

The steady-state analysis of the series resonant converter is presented using a novel frequency-domain model. Closed-form expressions are derived for the infinite Fourier series. The effects of load resistance, nonzero resistance of the inductor coil, and transistor and diode voltage drops are considered. The output current and voltage characteristics are plotted using the transistor conduction angle as the parameter. The operating point is easily obtained by superimposing on these characteristics a shifted load line that accounts for transistor and diode voltage drops. An example illustrating the solving procedures using the graphical and Newton-Raphson (N-R) methods is included. >

Small-signal modeling of multiple-output forward converters with current-mode control

A small-signal model of current-mode multiple-output feedback forward power converter has been developed. Based on the model, control performances are analytically expressed, and a compensation scheme is proposed. Comparison of such control with other control schemes is also discussed.

Modeling of control loop behavior of magamp post regulators

Small-signal control models are presented for a magamp switching-mode post regulator. Two commonly used current reset schemes are considered: an external reset scheme and a self-reset scheme. Models for both continuous and discontinuous modes of operation are presented. It is mathematically shown that the open-loop gain is a two-pole, single-zero transfer function for continuous-mode operation and a single-pole function for discontinuous-mode operation. The equations for predicting the loop gains for both types of reset circuits are derived and verified experimentally. It is shown that the loop gain characteristics of a magamp regulator depend on power circuit parameters, the reset circuit parameters, and the saturable reactor parameters. Therefore, in a normal design procedure of a magamp, if the design parameters of the saturable reactor are changed, a corresponding change of the compensation network must be made to optimize the control performance. The models presented provide the designer with a tool to facilitate the feedback loop design of a voltage-mode magamp post regulator.<<ETX>>

A PSpice-compatible model of PWM IC for switching power converters with soft-start characteristic

A new PSpice-based model is developed for simulating the soft-start characteristics of switching power supplies. Three commonly-used control ICs: TL494; SG3525; and UC3825 are considered. Using this model, starting characteristics of power supply circuits can be simulated effectively even with popular personal computers.<<ETX>>

Small-signal modeling of multiple-output flyback converters in continuous conduction mode with weighted feedback

A small-signal model of multiple-output flyback power converters is developed. From the model, closed-loop power converter performances, such as line regulation and load regulation, can be predicted. Based on the model, a design procedure for feedback compensation is suggested. The model is experimentally verified.