Abstract: An LED driver circuit, including: an LED load, having a top end, a middle end, and a bottom end, wherein the top end is coupled to a line voltage; and a variable load device, having a first input end, a second input end, and an output end, wherein the first input end is coupled to the middle end of the LED load for receiving a first current, the second input end is coupled to the bottom end of the LED load for receiving a second current, and the output end is for providing an output current, which equals the sum of the first current and the second current, and wherein the first current increases/decreases as the second current decreases/increases.

Abstract: A fixed dead time PFC controller, comprising: an amplitude normalization circuit, used to generate a normalized signal according to a full-wave rectified input voltage; a comparator circuit, used to compare the normalized signal with a threshold voltage to generate a select signal, wherein the select signal exhibits a first state when the normalized signal is higher than the threshold voltage, and a second state when the normalized signal is lower than the threshold voltage; and a driving signal selection circuit, having a first input end coupled to a first driving signal, a second input end coupled to a second driving signal, a control end coupled to the select signal, and an output end for outputting a gate driving signal.

Abstract: A system corrected programmable integrated circuit is applied to a power supply and includes a comparator unit, a digital output unit and a programming unit. The comparator unit includes an external feedback voltage input end and a reference voltage input end for inputting a feedback voltage and a reference voltage respectively, such that when the feedback voltage equals the reference voltage, the comparator unit transmits a control signal to the digital output unit. When receiving the control signal, the digital output unit stops outputting the reference voltage and the current reference voltage is recorded as a programming voltage for outputting to the programming unit. When receiving the programming voltage, the programming unit programs the programming voltage and transmits the voltage to the reference voltage input end. Accordingly, the present invention automatically detects and compensates a system error to reduce external element, yet still achieving a qualified range of product specification.

Abstract: A low-pin count fan speed control system and a method thereof include primarily an activation unit to drive a fan to operate. When the fan starts completely, the fan slows down to a pre-determined rotation speed through an idle speed regulation unit. After achieving a pre-determined temperature through a temperature transition unit, the fan speed beings to increase from the idle speed. When the fan is operating, the rotation speed is properly increased in proportion to the temperature, using a positive temperature regulation slope unit. Therefore, through this method, the rotation speed will not be decreased by foreign objects when the fan is operating and a computer host can be provided with proper heat dissipation.

Abstract: The present invention discloses an open loop LED driving circuit, having a turn-on period and a turn-off period, the circuit comprising: a power stage, used to store a magnetic energy supplied from a voltage source during the turn-on period and deliver the magnetic energy to a set of LEDs during the turn-off period; and a control unit, having a turn-off period control terminal coupled to the voltage source, and a channel of which a first terminal is coupled to the power stage and a second terminal is coupled to a reference ground, wherein the channel is switched on at a time according to the voltage of the voltage source to determine the turn-off period.

Abstract: A low input voltage boost converter operable at low temperatures, comprising a boost controller and an NMOS transistor. The boost controller has a driver unit, a first inverter circuit, a second inverter circuit, and a comparator circuit, wherein the first inverter circuit is used to enhance the high level of a switching signal during a startup period.

Abstract: A high side controller capable of sensing input voltage and output voltage of a power conversion circuit, including: a first switch, having a control end and two channel ends, the control end being coupled to a gate signal, and one of the two channel ends being coupled to a voltage signal, wherein the voltage signal is proportional to a negative version of the input voltage when the gate signal is active; an inverting amplification circuit, having an input end coupled to the other one of the two channel ends, and an output end for providing a first processed voltage; and a first sample and hold circuit, having a control input end coupled to the gate signal, an input end coupled to the first processed voltage, and an output end for providing a first sample voltage.

Abstract: The present invention discloses an integrated circuit for system calibration, applicable to a power supply, comprising: a comparison module, having a feedback input end coupled to a feedback signal and a reference input end coupled to an analog reference signal for delivering a status signal; a detection and control module, for generating a reference signal and a calibration value according to the status signal, wherein the calibration value is derived from the reference signal at an instant when the status signal changes state, and the calibration value is stored into a calibration value register; a memory module, for receiving, storing and outputting the calibration value; and a reference signal generator, receiving the calibration value to provide the analog reference signal. The present invention can therefore be used to automatically calibrate a system with fewer external components to provide qualified systems.

Abstract: A novel LED driver controller, including: an auto-gain control unit, having an input end coupled to an input voltage signal which is derived from a line voltage, and an output end for providing a normalized signal; a comparator, used to perform voltage comparison on the normalized signal and a current sensing signal to generate a turn-off signal, wherein the turn-off signal will change state from inactive to active when the current sensing signal reaches the normalized signal; and a driving circuit, having a set input end, a reset input end, and an output end, the set input end being coupled to a turn-on signal, the reset input end being coupled to the turn-off signal, the output end being used for providing a gating signal.

Abstract: A current-level controlling device for a power supply includes a reception end for receiving a current sense signal, a reference voltage generator for generating a reference voltage, an adaptive reference voltage generator, coupled to the reference voltage generator and the reception end, for adjusting the reference voltage according to variation of peak values of the current sense signal, so as to generate an adaptive reference voltage, a comparator, coupled to the reception end and the adaptive reference voltage generator, for comparing the current sense signal and the adaptive reference voltage, to generate a comparison result, and a control unit, coupled to the comparator, for controlling a switch transistor of the power supply according to the comparison result.

Abstract: The present invention discloses a control circuit with frequency compensation, which can be applied to an open-loop control system. The control circuit includes an oscillator which is additionally connected to a first comparator including a first input end, a second input end and a first output end. The first input end provides for inputting a sampling current, the second input end provides for inputting a total voltage of a reference voltage and a DC-level voltage, and the first output end outputs a down-conversion signal. When the sampling current is larger than the total voltage, the first comparator will generate the down-conversion signal to the oscillator to reduce a frequency of the oscillator, such that a current of the open-loop control system can be controlled effectively to prevent an electronic element form being burned down.

Abstract: This patent discloses an efficient PWM controller for generating a pulse signal in response to a feedback signal, capable of operating in a normal mode or a green mode, comprising: a capacitor for building a saw-tooth signal by current integration, the saw-tooth signal having a ramp-up period and a ramp-down period; a first composite current source for the ramp-up period, detachable into a first constant current source and a first variable current source; and a second composite current source for the ramp-down period, detachable into a second constant current source and a second variable current source; wherein, the first variable current source is attached to the first constant current source and the second variable current source is attached to the second constant current source respectively in the green mode.

Abstract: The present invention discloses a minimum on-time reduction method for a switching power conversion, comprising the steps of: generating a first reset signal and an over-supply pulse signal according to a current sensing signal and a reference signal; generating a blanking signal according to a count number of the over-supply pulse signal; and generating a second reset signal by performing Logic-AND operation on the first reset signal and the blanking signal. Furthermore, the present invention also provides a minimum on-time reduction apparatus for a power conversion, and a system using the minimum on-time reduction apparatus for a power conversion.

Abstract: The present invention discloses an integrated circuit for system calibration, applicable to a power supply, comprising: a comparison module, having a feedback input end coupled to a feedback signal and a reference input end coupled to an analog reference signal for delivering a status signal; a detection and control module, for generating a reference signal and a calibration value according to the status signal, wherein the calibration value is derived from the reference signal at an instant when the status signal changes state, and the calibration value is stored into a calibration value register; a memory module, for receiving, storing and outputting the calibration value; and a reference signal generator, receiving the calibration value to provide the analog reference signal. The present invention can therefore be used to automatically calibrate a system with fewer external components to provide qualified systems.

Abstract: A method of testing a cursor interactive with a pointing device on a displaying device includes pointing at a position on a displaying device by the pointing device within a predetermined period, identifying whether a movement of the cursor makes any change corresponding to the pointing device, and concluding a testing result in accordance with the movement of the cursor.

Abstract: A method for identifying a fingerprint image includes inputting a fingerprint image captured by an electronic device, calculating an amount of valid ridge pixels in an amount of total ridge pixels of the fingerprint image to generate a first ratio, calculating an amount of successive ridge pixels in an amount of total ridge pixels of the fingerprint image to generate a second ration when the first ratio is identified within a first predetermined range, and determining the fingerprint image as a valid fingerprint image when the second ratio is identified within a second predetermined range.

Abstract: A primary-side feedback control device for a power converter includes a control unit for generating a pulse signal according to a feedback signal for controlling on and off states of a switching transistor of the power converter, a comparator coupled to an auxiliary winding of a primary side of the power converter for generating at least one control signal according to a voltage on the auxiliary winding and a reference voltage, a sample-and-hold unit coupled to the auxiliary winding, the comparator, and the control unit for generating the feedback signal according to the voltage on the auxiliary winding and the at least one control signal, and a voltage generator coupled to the control unit, the comparator, and the sample-and-hold unit for generating the reference voltage according to the feedback signal.

Abstract: The present invention discloses an open loop LED driving circuit, having a turn-on period and a turn-off period, the circuit comprising: a power stage, used to store a magnetic energy supplied from a voltage source during the turn-on period and deliver the magnetic energy to a set of LEDs during the turn-off period; and a control unit, having a turn-off period control terminal coupled to the voltage source, and a channel of which a first terminal is coupled to the power stage and a second terminal is coupled to a reference ground, wherein the channel is switched on at a time according to the voltage of the voltage source to determine the turn-off period.

Abstract: The present invention discloses a quasi-resonant valley voltage detecting method, comprising the steps of: generating a valley detection signal by detecting a valley of a first quasi-resonant signal; generating a count value by counting the valley detection signal; and determining a level transition instance of a gating signal according to the count value, wherein the level transition instance of the gating signal is pulled back by the valley detection signal to trace the valley of the first quasi-resonant signal. The present invention also provides a quasi-resonant valley voltage detecting apparatus.

Abstract: An overcurrent protection device for a power supply device includes a receiving end for receiving a current sensing signal, a compensating current unit coupled to the receiving end for compensating the current sensing signal in order to generate a current sense compensation signal, a first reference voltage generator for generating a first reference voltage, a comparator coupled between the compensating current unit and the first reference voltage generator for comparing the current sense compensation signal with the first reference voltage in order to generate a comparison result, a control unit coupled to the comparator for controlling a power switch of the power supply device according to the comparison result.