Abstract: The present invention is an apparatus for driving white LEDs. The apparatus includes a switchable current sink, a DC-DC converter and a reference circuit. The DC-DC converter provides a driving voltage to a plurality of LEDs. The switchable current sink regulates currents through the plurality of LEDs, and the switchable current sink further provides a first reference voltage and outputs a plurality of voltage drops. The reference circuit receives the first reference voltage and the plurality of voltage drops to provide a second reference voltage to the DC-DC converter. The DC-DC converter adjusts the driving voltage provided to the plurality of LEDs according to the second reference voltage. In this way, the driving voltage is regulated to a minimum possible value and consequently the voltage drops across the switchable current sink is minimized. Hence, the LED driving system maintains higher efficiency.

Abstract: A power supply topology with pulse width modulation frequency control allows the use of an inductor with higher inductance in a converter. By controlling the switching frequency of the pulse width modulation signal, the inductor can achieve high efficiency during a light load condition and is also suitable for a heavy load condition.

Abstract: A DC-to-DC converter with improved transient response, accuracy and stability is disclosed. The DC-to-DC converter includes a comparator, a driver, at least one switch and a stability circuit. The stability circuit receives a voltage signal based upon sensing one of the at least one switch. The configuration with elimination a current sensing resistor can create a simpler solution for the DC-to-DC converter.

Abstract: In one embodiment, a current sensing circuit for a converter includes a sensing switch and a comparator. The sensing switch is coupled to a power switch within the converter for receiving a first voltage signal indicative of the current through the power switch. The sensing switch also produces a second voltage signal based on the first voltage signal. The comparator is coupled to the sensing switch for detecting an operation condition of the converter based on the second voltage signal. An offset voltage between the second voltage signal and the first voltage signal can compensate for a delay at the comparator.

Abstract: A method for using a single pin to support both power input and power control functions for an integrated circuit, wherein the integrated circuit is in communication with a system. The method includes receiving at the pin a power input signal from the system, generating a power control signal based on the power input signal through a control signal generating circuit, and sending the power control signal to the integrated circuit.

Abstract: A circuit according to the present invention is used for driving a photoflash diode and comprises a current sink, a feedback circuit, and a DC-DC converter. The current sink is coupled to the photoflash diode for controlling the current through the photoflash diode. The feedback circuit receives a feedback signal indicative of the electrical condition of said first current regulator. The DC-DC converter is coupled to an external power source and the feedback circuit for powering the photoflash diode so as to control the electrical condition of the current sink to a predetermined value.

Abstract: A power supply topology with pulse width modulation frequency control allows the use of an inductor with higher inductance in a converter. By controlling the switching frequency of the pulse width modulation signal, the inductor can achieve high efficiency during a light load condition and is also suitable for a heavy load condition.

Abstract: A DC-to-DC converter with improved transient response, accuracy and stability is disclosed. The DC-to-DC converter includes a comparator, a driver, at least one switch and a stability circuit. The stability circuit receives a voltage signal based upon sensing one of the at least one switch. The configuration with elimination a current sensing resistor can create a simpler solution for the DC-to-DC converter.

Abstract: The present invention is an apparatus for driving white LEDs. The apparatus includes a switchable current sink, a DC-DC converter and a reference circuit. The DC-DC converter provides a driving voltage to a plurality of LEDs. The switchable current sink regulates currents through the plurality of LEDs, and the switchable current sink further provides a first reference voltage and outputs a plurality of voltage drops. The reference circuit receives the first reference voltage and the plurality of voltage drops to provide a second reference voltage to the DC-DC converter. The DC-DC converter adjusts the driving voltage provided to the plurality of LEDs according to the second reference voltage. In this way, the driving voltage is regulated to a minimum possible value and consequently the voltage drops across the switchable current sink is minimized. Hence, the LED driving system maintains higher efficiency.

Abstract: A method for using a single pin to support both power input and power control functions for an integrated circuit, wherein the integrated circuit is in communication with a system. The method includes receiving at the pin a power input signal from the system, generating a power control signal based on the power input signal through a control signal generating circuit, and sending the power control signal to the integrated circuit.

Abstract: A circuit according to the present invention is used for driving a photoflash diode and comprises a current sink, a feedback circuit, and a DC-DC converter. The current sink is coupled to the photoflash diode for controlling the current through the photoflash diode. The feedback circuit receives a feedback signal indicative of the electrical condition of said first current regulator. The DC-DC converter is coupled to an external power source and the feedback circuit for powering the photoflash diode so as to control the electrical condition of the current sink to a predetermined value.