Abstract: A bridgeless PFC (power factor correction) converter with improved efficiency is disclosed. The bridgeless PFC converter comprises: input terminals configured to receive an input AC power supply; an output terminal configured to provide power supply; a high frequency bridge arm comprising a first switch and a third switch coupled between the output terminal and a ground node; a low frequency bridge arm comprising a second switch and a fourth switch coupled between the output terminal and the ground node; an inductor coupled between the input AC power supply and the high frequency bridge arm; and a control circuit configured to control the switching of switches in the high frequency bridge arm and the low frequency bridge arm.

Abstract: The embodiments of the present invention disclose a ballast and associated control circuit wherein the control circuit comprises a multi function pin, a preheat cut-off circuit and an over-voltage protection circuit, wherein the multi function pin is coupled to the preheat cut-off circuit and a first switch configured to turn on the first switch at a preheat state of the ballast and to turn off the first switch at the end of the preheat state, and wherein the multi function pin is further coupled to the over-voltage protection circuit and a voltage sense circuit configured to receive a sensed output voltage signal and to stop the ballast after the preheat state when the sensed output voltage is larger than a first threshold. Compared with prior art, the present invention may reduce the volume and lower down the cost of circuit.

Abstract: Switching mode power supplies (SMPS) that can operate in a control mode for a normal load condition and operate with a burst-mode controller for a light load condition are disclosed herein. In one embodiment, a method for controlling the switching mode power supply includes when the load is in a light load condition, the switching mode power supply is controlled by a burst-mode controller.

Abstract: In accordance with the teachings described herein, systems and methods are provided for a switching mode power supply. In one example, the switching mode power supply may include a transformer, a switching circuit and a switching control circuit. The transformer receives a DC input voltage on a primary winding and generates a DC output voltage on a secondary winding. The switching circuit, which may include a MOSFET switch, is coupled to the transformer and is configured to switch the transformer on and off. The switching control circuit generates a switching control signal to control the switching circuit in order to regulate the DC output voltage of the transformer.

Abstract: A frequency limitation method used in quasi-resonant control of a switching regulator is disclosed. The switching frequency is limited through setting a minimum time limit, such as a minimum switching period or a minimum OFF time. The minimum time limit may be a first time limit or a second time limit. The minimum time limit is changed into another value if the minimum voltage point approaches the minimum time limit point, so as to eliminate the audible noise.

Abstract: A bridgeless PFC (power factor correction) converter with improved efficiency is disclosed. The bridgeless PFC converter comprises: a first input terminal and a second input terminal configured to receive an input AC signal; an output terminal; an inductor set comprising N inductors, wherein a first terminal of each inductor is coupled to the first input terminal; and an output stage comprising (N+1) switching circuits coupled between the output terminal and a ground node.

Abstract: A switching mode power supply with improved peak current control is disclosed. A varying reference signal is adopted to limit the peak current in the energy storage component. The varying reference signal is an exponential function of a time period when a power switch is ON, wherein the power switch is coupled to the energy storage component. The varying reference signal may be generated by a circuit comprising a RC circuit and one or several voltage sources.

Abstract: A compensation circuit and method for constant current regulation of switching mode power supply are disclosed. The ringing waveform of a feedback signal, indicative of the output current of the power supply, causes error. To eliminate the error, a current source charges a capacitor in response to a demagnetizing oscillation signal indicative of the error caused by the ringing waveform of the feedback signal. The voltage across the capacitor is compared to a reference signal to generate a more accurate signal indicative of the conductive time of a secondary diode in a secondary winding of the switching mode power supply. This more accurate signal is inputted to a logic circuit to generate a constant current control signal to control a power switch of the power supply.

Abstract: SIMO power converters and associated methods of control are disclosed herein. In one embodiment, a method of converting a signal input signal into multiple output signals includes supplying power to a plurality of output terminals based on a signal input signal, detecting a voltage at individual output terminals, determining an arithmetic relationship between the detected voltages of the output terminals, and adjusting the power supplied to the plurality of output terminals based at least in part on the determined arithmetic relationship between the detected voltages of the output terminals.

Abstract: Methods and apparatus for driving discharge lamps are disclosed herein. In one embodiment, a method for driving a discharge lamp includes generating a switching signal to drive a discharge lamp, monitoring a working status of the discharge lamp, and determining whether the discharge lamp is operating abnormally based at least in part on the monitored working status. The method also includes decreasing a duty cycle of the switching signal when the discharge lamp is determined to operate abnormally.

Abstract: The present invention provides a method and apparatus for driving multiple parallel discharge lamps, which increases the switching frequency once the open lamp condition is detected to provide an output voltage that is high enough to ignite the lamp again.

Abstract: The present invention discloses a smart driving method for a secondary synchronous rectifier of an isolated converter and its apparatus thereof. The apparatus comprises: a main circuit having a secondary synchronous rectifier Q1; a differentiation filter circuit, filtering the drain-source voltage Vds of the secondary synchronous rectifier, comprising a capacitor and at least one resistor connected in series and outputting a filtered voltage Vf from either between said capacitor and said at least one resistor or between said at least one resistor; a smart driver, receiving Vf and Vds and putting out a driving signal to the gate of the secondary synchronous rectifier. The control approach is fulfilled by comparing Vds to a reference voltage Vthr2 and comparing the absolute value of Vf to another reference voltage Vthr3. When Vds<Vthr2 and |Vf|>Vthr3, Q1 is turned on. When Vds>Vthr1, Q1 is turned off, where Vthr1 is a predetermined reference voltage.

Abstract: This disclosure presents method and circuit for current balance. An AC signal or a DC signal is applied to a circuit to source current to loads. A capacitor is configured to balance the current in loads. By matching the charging time and the discharging time of the balance capacitor in every cycle, the current balance of the loads is achieved.

Abstract: Triac dimmer compatible switching mode power supplies used as LED drivers are disclosed herein. A PFC controller is configured in the switching mode power supplies. With the PFC controller, the current keeping the triac in the on-state is supplied by the DC/DC converter, and the LC resonance is reduced.

Abstract: A CCFL inverter circuit integrates a feedback circuit and protection circuit together. For both in-phase and out-of-phase applications, sensed lamp voltages can be used for open lamp and short lamp detection and sensed currents can be used for open lamp detection. The driving circuit adjusts the open lamp frequency by using a duty cycle control signal so that the driving circuit can always achieve the desired lamp voltage gain.

Abstract: An inventive isolated converter which exempts the auxiliary isolation devices with accurate voltage regulation is disclosed. The converter includes the primary side circuit with a primary controller controlling the on and off of the primary switch and a secondary side circuit with a secondary controller controlling the on and off of the secondary synchronous rectifier. The isolated converter uses the secondary controller to turn on the secondary synchronous rectifier after the secondary current decreases to zero to generate a negative tail current and turns off the secondary synchronous rectifier at a reference tail current peak value to generate a reflected negative current at the primary side circuit for turning on the primary switch.

Abstract: LED driver systems and associated methods of control are disclosed herein. In one embodiment, the LED driver system comprises a converter and a controller. The controller is responsive to the LED current feedback signal and a dimming signal, and operable to generate a continuous gate drive signal to control the primary side switch of the converter. Thus, the controller regulates the output current of the converter.

Abstract: Embodiments of LED driver circuits and the associated methods are disclosed herein. In one embodiment, the LED driver circuit comprises a switch-mode converter, a controller, a feedback circuit, and a gating circuit. The feedback circuit includes a current balance circuit. The gating circuit is responsive to both a current feedback signal and a voltage feedback signal and is configured to select one of them as the feedback signal.

Abstract: Light emitting diode (LED) dimming and driver systems and associated methods of control are disclosed herein. In one embodiment, a system comprises a PFC stage and an LED driver stage. The LED driver stage comprises an isolated converter and a controller responsive to a dimming signal to dim LED strings for backlight. The controller also regulates an output current of the isolated converter.

Abstract: The present invention discloses a Class-D power amplifier and control method thereof. In one embodiment, the amplifier feeds back the signal at the output node to the inverting input of the comparator, and provides a high frequency triangular wave signal to the non-inverting input of the comparator. In addition, the non-inverting input of the comparator may be coupled to an offset voltage, while the inverting input of the comparator may be coupled to a fixed-frequency rectangular wave signal, a feedback signal which is derived from the output stage and an input signal. In use, the switching frequency may be at least substantially fixed, so as to reduce the influence on the system caused by electromagnetic interruption (EMI). Further, the control circuit is simple, and some devices can be integrated.