Abstract: Disclosed is a single-inductor DC-DC converter capable of delivering a multiple output voltages. One of the output voltages is always higher than the input voltage, while other output voltages may by higher or lower than the input voltage. The DC-DC converter requires no input power switch connected between the input voltage source and the power inductor. The DC-DC converter delivers power to all output voltages during the same switching cycle. The highest output voltage is used to reset the inductor current.

Abstract: An active power factor correction (PFC) circuit and its controlling method are provided. The method comprises the following steps. Drive the power switch of the circuit so that the average inductor current waveform follows the rectified input voltage waveform. Suspend the operation of the power switch at a first moment in a first line cycle of the rectified input voltage and then resume the operation of the power switch at a second moment in a second line cycle of the rectified input voltage. The first moment is when the phase angle of the rectified input voltage exceeds a predetermined angle and the switching frequency of the power switch exceeds a predetermined frequency. The time span from the first moment to the end of the first line cycle is substantially as long as the time span from the beginning of the second line cycle to the second moment.

Abstract: A driving circuit includes an input node, a power storage unit, a transformer, a charger IC, a rectifier diode and a high-voltage capacitor. The input node receives an DC input voltage. The transformer has a primary coil, whose first end connected to the input node, and a secondary coil. The power storage unit is connected to the second end of the primary coil for providing a supply voltage. The charger IC has a power pin for receiving the supply voltage, and a switch pin connected to the second end of the primary coil for providing a pulse series such that the transformer generates an AC voltage from the first end of the secondary coil. The rectifier diode is connected to the first end of the secondary coil. The high-voltage capacitor is connected to the cathode of the rectifier diode and charged for providing a high voltage to the photo-flash.

Abstract: The speed control apparatus comprises a plurality of Hall sensors, a plurality of switches, a turn-on control circuit, and a gate drive logic. The Hall sensors are configured to detect magnetic rotor sections of a poly-phase brushless DC motor at different positions. The switches apply voltages on a plurality of windings to respectively produce magnetic north or south on stator poles of the poly-phase BLDC motor. The turn-on control circuit generates a conduction time reduction after each output transition of the Hall sensors. The gate drive logic separately turns on or turns off the switches according to different output transitions of the Hall sensors to respectively apply voltages on the windings with the conduction time reduction.

Abstract: A double reference wave modulation scheme for filterless power amplifiers is disclosed for reducing EMI and common mode voltages. In the filterless power amplifier, differential outputs for driving load impedance are feedback and corrected based on input audio signals. Reference wave generators generate reference waves. A control logic results pulses in the pair of differential outputs in response to a clock signal or a reference voltage and a cross relationship between the input audio signal and the first and second reference waves. Pulses of one of the differential outputs are not overlapped with pulses of the other of the differential outputs for eliminating common mode noises of the power amplifier.

Abstract: A DC to DC converter has an inverter, an inductor, a voltage sensor, a comparator, a clock generator, a driver and an output capacitor. The inverter converts an input voltage into a square-wave voltage. The inductor is electrically connected to an output of the inverter. The voltage sensor is electrically connected to the inductor and derives a sense voltage. The comparator compares the sense voltage and a reference voltage. The clock generator generates a reference clock pulse. The driver is triggered by the reference clock pulse and switches the inverter according to an output of the comparator. The output capacitor is electrically connected between the voltage sensor and the ground.

Abstract: A family of quasi-resonant converters is disclosed as comprising a voltage source, a transformer having primary and secondary windings, and a switch for periodically coupling the voltage source to the primary winding, whereby a charging current appears on the secondary winding. The transformer exhibits a characteristic leakage inductance. A capacitor exhibiting a characteristic capacitance is coupled to the secondary winding to form a resonant circuit including the leakage inductance and the capacitor. The secondary winding is coupled to apply the charging current to the capacitor. A rectifying circuit couples the capacitor to a load, whereby the voltage stored in the capacitor is delivered to the load. The capacitor is directly connected to the secondary winding and to the rectifying circuit to permit positive and negative going voltages to be stored therein, whereby magnetic flux within the core of the transformer is dissipated and the transformer magnetically reset.

Abstract: A family of quasi-resonant converters for providing regulated power is disclosed as comprising a voltage source, a load and a resonant switch circuit, for periodically connecting the voltage source to the load. The resonant switch circuit includes a switch, and a resonant circuit comprised of a resonant capacitor and a resonant inductor. The switch is actuated to its first state to permit a current flow in a first direction from the voltage source to the load and to block a current flow in a second, opposite direction, and deactuated to a second state to permit a current flow in the second direction from the load to the voltage source and to block the current flow in the first direction, whereby the quasi-resonant converter is operative in a full-wave mode. More specifically, the switch in its first state couples the resonant capacitor and the resonant inductor together to form a resonant switch circuit.

Abstract: A quasi-resonant converter is disclosed as comprising a power source, a load and a resonant switch circuit for periodically connecting the power source to the load. The resonant switch circuit includes a switch for connecting the power source to the load and for disconnecting the power source from the load, and a resonant circuit comprised of a resonant capacitor and a resonant inductor. The switch is operated at a switching frequency in excess of 1 MHz and in the order of 10 to 20 MHz or greater. The resonant circuit is connected to the switch to impose thereon a voltage waveform as developed across the resonant capacitor. The resonant capacitor and the resonant inductor have respective impedances selected to shape the voltage waveform such that a zero-voltage condition is imposed upon the switch when it is disposed to its on state, whereby the parasitic capacitive losses associated with the switch are eliminated.