Abstract: Disclosed are a totem-pole bridgeless power factor correction (PFC) soft switch control device and method, wherein, the device includes a totem pole bridgeless PFC circuit, and the totem pole bridgeless PFC circuit includes at least two bridge arms connected in parallel between a first connecting point and a second connecting point: the first bridge arm includes two switches or diodes connected in serial in a same direction, the second bridge arm includes two switches that are connected in serial in the same direction, the totem pole bridgeless PFC circuit includes at least one PFC inductor, and further a filter capacitor and a load connected in parallel between the first connecting point and the second connecting point.

Abstract: A control circuit for a power converter can include: a current detection circuit configured to generate a current detection signal that represents an input current; a control signal generator configured to generate a switching control signal such that the current detection signal is directly proportional to a voltage conversion function; and a power stage circuit of the power converter being controlled by the switching control signal, where the voltage conversion function is a ratio of an input voltage and an output voltage of the power converter.

Abstract: A circuit includes a power supply end, a switching tube and a first loop connected to the power supply end in order, a second loop, and a load. The power supply end provides an input voltage for the circuit through a positive busbar and a negative busbar. The first loop includes a first capacitor, a first inductor, and a first freewheeling diode. When the switching tube is on, the first inductor is charged by the input voltage through the first capacitor; and when the switching tube is off, the first inductor discharges through the first capacitor and the first freewheeling diode. The second loop includes a second inductor coupled with the first inductor, a second capacitor and a second freewheeling diode forming a loop with the second inductor. The second capacitor and the first capacitor are connected in series.

Abstract: An isolated switching mode power supply, having: an input terminal; an output terminal; a transformer having a primary winding and a secondary winding; a primary power switch coupled to the primary winding; a secondary power switch coupled between the secondary winding and the output terminal of the power supply; a secondary controller configured to generate a frequency modulation signal based on the output voltage and the first feedback signal; a coupled device configured to provide a frequency control signal based on the output voltage and the frequency modulation signal; and a primary controller configured to provide a switching signal to control the primary power switch based on the current sense signal and the frequency control signal.

Abstract: Disclosed are a current zero-cross detection device, zero-cross current signal acquisition circuit and totem pole bridgeless circuit system. The current zero-cross detection device includes a current transformer, first sampling switch, second sampling switch, sampling resister, comparator. The current transformer includes a primary winding and a secondary winding; the primary winding is connected to a circuit to be detected; two ends of the secondary winding are connected respectively to drain electrodes of the first and second sampling switches; source electrodes of first and second sampling switches are connected to ground; two ends of the sampling resistor are connected respectively to the drain electrode and source electrode of the second sampling switch; the negative input end of the comparator is connected to the drain electrode of the second sampling switch, its positive input end is connected to a reference voltage; the first and second sampling switches are in ON or OFF state.

Abstract: A peak sample circuit for AC voltage, including: a rectifier coupled to receive an AC voltage and to rectify the AC voltage to generate a rectified signal; a delay circuit coupled to receive the rectified signal and to delay the rectified signal to generate a delayed rectified signal; a comparison circuit coupled to receive the delayed rectified signal and to generate a square signal based on the comparison of the rectified signal and the delayed rectified signal; and a sample output circuit coupled to receive the rectified signal, wherein the sample output circuit samples the rectified signal under the control of the square signal and provides a peak sample signal representative of the peak value of the AC voltage.

Abstract: A PFC circuit includes: a switching circuit having a power switch; an on time control circuit for controlling an on time period of the power switch; a first off time control circuit; a second off time control circuit; and a logic circuit selectively controls the power switch working under CCM or DCM; when working under CCM, the first off time control circuit controls an off time period of the power switch and when working under DCM, the second off time control circuit controls the off time period of the power switch.

Abstract: An improved gate drive circuit is provided for a power device, such as a transistor. The gate driver circuit may include: a current control circuit; a first secondary current source that is used to control the switching transient during turn off of the power transistor and a second secondary current source that is used to control the switching transient during turn on of the power transistor. In operation, the current control circuit operates, during turn on of the power transistor, to source a gate drive current to a control node of the power transistor and, during turn off of the power transistor, to sink a gate drive current from the control node of the power transistor. The first and second secondary current sources adjust the gate drive current to control the voltage or current rate of change and thereby the overshoot during the switching transient.

Abstract: Disclosed are a totem-pole bridgeless power factor correction (PFC) soft switch control device and method, wherein, the device includes a totem pole bridgeless PFC circuit, and the totem pole bridgeless PFC circuit includes at least two bridge arms connected in parallel between a first connecting point and a second connecting point: the first bridge arm includes two switches or diodes connected in serial in a same direction, the second bridge arm includes two switches that are connected in serial in the same direction, the totem pole bridgeless PFC circuit includes at least one PFC inductor, and further a filter capacitor and a load connected in parallel between the first connecting point and the second connecting point.

Abstract: An isolated switching converter includes a transformer having a primary winding, a secondary winding and an auxiliary winding, a primary switch coupled to the primary winding, a secondary switch coupled to the secondary winding, and a feedback circuit coupled to the auxiliary winding to generate a feedback signal indicative of the output voltage. Under normal operation, the primary switch is controlled based on the feedback signal and the secondary switch is controlled based on the status of the primary switch. Under light load condition, the secondary switch is controlled based on the output voltage. The secondary switch is turned on to generate a negative secondary current flowing through the secondary winding and turned off when the negative secondary current reaches a secondary current threshold. The primary switch is turned on based on a negative primary current and turned off when the primary current reaches a primary current threshold.

Abstract: Disclosed are a current zero-cross detection device, zero-cross current signal acquisition circuit and totem pole bridgeless circuit system. The current zero-cross detection device includes a current transformer, first sampling switch, second sampling switch, sampling resister, comparator. The current transformer includes a primary winding and a secondary winding; the primary winding is connected to a circuit to be detected; two ends of the secondary winding are connected respectively to drain electrodes of the first and second sampling switches; source electrodes of first and second sampling switches are connected to ground; two ends of the sampling resistor are connected respectively to the drain electrode and source electrode of the second sampling switch; the negative input end of the comparator is connected to the drain electrode of the second sampling switch, its positive input end is connected to a reference voltage; the first and second sampling switches are in ON or OFF state.

Abstract: A switch mode power supply having an output terminal configured to provide an output voltage, the switch mode power supply has a first switch and a control circuit. The control circuit is configured to provide a switching control signal to control the first switch. The control circuit is configured to provide the switching control signal based on a first pulse signal having a first frequency and a second frequency for a light load condition, and the control circuit is configured to provide the switching control signal based on a second pulse signal for a non-light load condition.

Abstract: An AC signal detector having: a rectify circuit having a first input terminal and a second input terminal configured to receive an AC signal, and an output terminal configured to provide a rectified signal based on the AC signal; a detecting circuit having an input terminal coupled to the output terminal of the rectify circuit to receive the rectified signal, and an output terminal configured to provide a square signal based on the rectified signal; and an unplug indicate circuit having an input terminal coupled to the detecting circuit to receive the square signal, and an output terminal configured to provide an unplug indicate signal based on the square signal.

Abstract: A switching mode power supply, having: an input port; an output port; an energy storage component and a pair of power switches coupled between input port and the output port; an error amplifier configured to generate an amplified error signal based on the feedback signal and the reference signal; an error comparator configured to generate a frequency control signal based on the amplified error signal and the first sawtooth signal; a peak current generator configured to generate a peak current signal based on the frequency control signal; a peak current comparator configured to generate a current limit signal based on the peak current signal and the current sense signal; and a logic circuit configured to generate a switching signal to control the power switches based on the frequency control signal and the current limit signal.

Abstract: An isolated switching mode power supply, having: a transformer having a primary winding, a secondary winding and a third winding; a current limit comparator configured to provide a current limit signal based on the current sense signal and the peak current signal; a logic circuit configured to provide a logic control signal based on the frequency control signal and the current limit signal; a startup control circuit configured to generate a startup control signal based on the current sense signal; a load detecting circuit configured to provide a load detecting signal based on the second feedback signal and the switching signal; and a selector configured to provide the logic control signal or the startup control signal based on the load detecting 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: An isolated switching converter includes a transformer having a primary winding, a secondary winding and an auxiliary winding, a primary switch coupled to the primary winding, a secondary switch coupled to the secondary winding, and a feedback circuit coupled to the auxiliary winding to generate a feedback signal indicative of the output voltage. Under normal operation, the primary switch is controlled based on the feedback signal and the secondary switch is controlled based on the status of the primary switch. Under light load condition, the secondary switch is controlled based on the output voltage. The secondary switch is turned on to generate a negative secondary current flowing through the secondary winding and turned off when the negative secondary current reaches a secondary current threshold. The primary switch is turned on based on a negative primary current and turned off when the primary current reaches a primary current threshold.

Abstract: The present invention provides an off time control method and switching regulator using it. The current flowing through a switch is compared with a current threshold, and the switch is turned off if the current flowing through the switch is larger than the current threshold. The off time of the switch is determined by the load. The current threshold is variable at light load to prevent generating the audible noise and improve the whole efficiency.

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: An improved gate drive circuit is provided for a power device, such as a transistor. The gate driver circuit may include: a current control circuit; a first secondary current source that is used to control the switching transient during turn off of the power transistor and a second secondary current source that is used to control the switching transient during turn on of the power transistor. In operation, the current control circuit operates, during turn on of the power transistor, to source a gate drive current to a control node of the power transistor and, during turn off of the power transistor, to sink a gate drive current from the control node of the power transistor. The first and second secondary current sources adjust the gate drive current to control the voltage or current rate of change and thereby the overshoot during the switching transient.