Abstract: A control apparatus for a power conversion circuit and a control method thereof are provided. The method of the control apparatus includes producing a first control signal and a second control signal; modulating the first control signal according to an output voltage of the power conversion circuit; detecting the output voltage of the power conversion circuit to attain a detecting result; if the detecting result exhibits the input voltage of the power conversion circuit below a normal operating level, using the second control signal to control the power conversion circuit; or if the detecting result exhibits the input voltage of the power conversion circuit above the normal operating level, using the first control signal to control the power conversion circuit. The duty cycle of the fist control signal is greater than that of the second control signal.

Abstract: A pulse width modulation (PWM) circuit includes a turn on/off switch and a PWM controller. The first terminal of the turn on/off switch is coupled to a turn off voltage. The control terminal of the turn on/off switch receives a turn on/off signal to decide whether the circuit between the first terminal and the second terminal of the turn on/off switch is turned on or not. The PWM controller includes a PWM pin and a turn on/off device. The PWM pin is coupled to the second terminal of the turn on/off switch to output a PWM signal. The turn on/off device is coupled to the PWM pin to decide the turn on/off of the PWM controller according to a signal swing state of the PWM pin.

Abstract: A control circuit for P-type power transistor. The P-type power transistor includes a gate coupled between an input voltage and an output voltage. A first switch is coupled between a first voltage and the gate. A current source provides a first current, and is coupled to a second voltage. A second switch is coupled between the first switch, the gate and the current source. The voltage level of the gate is determined according to the first current when the first switch is turned off and the second switch is turned on.

Abstract: A pulse width modulation (PWM) controller is provided. The PWM controller transfers a conventional enable mechanism integrated into a versatile pin (PH) and integrates it into a feedback pin (FB) of the PWM controller, so as to promote the noise reduction capability of the PWM controller and avoid false operation. Furthermore, the parasitic capacitance of an enable transistor employed in the enable mechanism of the PWM controller does not degrade the accuracy of the over-current protection performed by the PWM controller on an electronic device. Thus, the PWM controller can effectively perform the over-current protection mechanism on the electronic device.

Abstract: A voltage reference circuit and method for producing a voltage as a reference voltage for a liquid crystal display (LCD) panel. The voltage reference circuit with controllable temperature coefficients includes a logic operation unit and a voltage selection circuit. The logic operation unit receives a command corresponding to the temperature coefficient of an LCD panel and provides a selection signal according to the command. The selection signal is applied to the voltage selection circuit. Depending on the selection signal, the voltage selection circuit generates a selected voltage which is used to produce a reference voltage.

Abstract: A control circuit for eliminating residual image in an LCD includes: a detecting circuit, a comparator, a sub-control circuit, and a discharge circuit. When an LCD voltage generating circuit is turned on and the driving voltage of the circuit is built, the detecting circuit outputs an enable signal to the comparator, to compare a reference voltage and a threshold voltage. When the reference voltage is lower than the threshold voltage, the comparator outputs a data signal to the sub-control circuit. After receiving the data signals, the sub-control circuit outputs a control signal to the discharge circuit to release the charge stored in the at least one stable state capacitor of the LCD's voltage generating circuit, thus preventing the formation of residual image.

Abstract: A voltage reference circuit and method for producing a voltage as a reference voltage for a liquid crystal display (LCD) panel. The voltage reference circuit with controllable temperature coefficients includes a logic operation unit and a voltage selection circuit. The logic operation unit receives a command corresponding to the temperature coefficient of an LCD panel and provides a selection signal according to the command. The selection signal is applied to the voltage selection circuit. Depending on the selection signal, the voltage selection circuit generates a selected voltage which is used to produce a reference voltage.

Abstract: An apparatus and method is provided for generating VBI data coding waveforms. The present invention utilizes a single look-up table that stores sampled values of sine waves in direct waveform synthesis for both color burst processing and VBI data coding processing. Furthermore, the present invention utilizes a 2T pulse as a signalling waveform in direct synthesis to overcome the problem of overlap for conventional unit pulse durations.