An active clamp switching power converter circuit includes a primary-side sensing circuit that generates a sensed voltage based on an auxiliary winding voltage of an auxiliary winding around the core having a same polarity as the primary winding. Based on the sensed voltage, a controller controls switching of a power switch coupled to the primary winding to control current through the primary winding and controls switching of an active clamp switch to control leakage current when the power switch is turned off. The controller regulates timing of the switching to turn on the power switch based on timing of a zero voltage switching condition for power efficient operation.

A theory and a technical foundation for building a technical framework of a color temperature tuning technology are disclosed, composing a power allocation algorithm and a power allocation circuitry, wherein the power allocation algorithm is a software for designing a process of dividing and sharing a total electric power between at least a first LED load emitting light with a first color temperature CT1 and a second LED load emitting light with a second color temperature CT2 to generate at least one paired combination of a first electric power X allocated to the first LED load and a second electric power Y allocated to the second LED load to create at least one mingled light color temperature CTapp thru a light diffuser according to color temperature tuning formulas CTapp=CT1.Math.X/(X+Y)+CT2.Math.Y/(X+Y) and X+Y=constant; and the power allocation circuitry is a hardware designed for implementing the process.

The present disclosure concerns a method and a circuit for controlling first and second switches electrically in series, wherein one or a plurality of crossings of a voltage threshold by a voltage across the first switch cause a conductive state of the second switch.

A drive circuit with a zero-crossing detection function, and a zero-crossing detection method. The drive circuit comprises: a power switch transistor, a pull-up drive transistor, a first pull-down drive transistor and a second pull-down drive transistor. When an inductor starts to discharge, the first pull-down current and the second pull-down current jointly pull down a gate terminal of the power switch transistor, such that the power switch transistor is in a cut-off state; after a set time, the first pull-down current is turned off; and when the inductor ends discharging, a parasitic capacitance of the power switch transistor couples with the drop signal, and when the drop signal is detected, the pull-up current pulls up the gate terminal of the power switch transistor, such that the power switch transistor is in a turn-on state.

A color temperature switching scheme for an LED lighting device is disclosed. The color temperature switching scheme comprises a plurality of different color temperature performances correspondingly generated by a plurality of different paired combinations of a first electric power allocated to a first LED load emitting a light with a first color temperature and a second electric power allocated to a second LED load emitting a light with a second color temperature such that a mingled color temperature between the first color temperature and the second color temperature can be generated thru a light diffuser. For tuning the mingled color temperature of the LED lighting device a reverse yet complementary power adjustment process for distributing a total electric power T between the first LED circuit and the second LED circuit is required such that a total light intensity remains essentially unchanged while the mingled color temperature is being adjusted.

A theory and a technical foundation for building a technical framework of a color temperature tuning technology are disclosed composing a power allocation algorithm and a power allocation circuitry, wherein the power allocation algorithm is a software for designing a process of dividing and sharing a total electric power between at least a first LED load with a color temperature CT1 and a second LED load with a color temperature CT2 to generate at least one paired combination of a first electric power X allocated to the first LED load and a second electric power Y allocated to the second LED load to create at least one mingled light color temperature CTapp thru a light diffuser according to color temperature tuning formulas CTapp=CT1.Math.X/(X+Y)+CT2.Math.Y/(X+Y) and X+Y=constant; and the power allocation circuitry is a hardware designed for implementing the process.

A drive circuit with a zero-crossing detection function, and a zero-crossing detection method. The drive circuit comprises: a power switch transistor, a pull-up drive transistor, a first pull-down drive transistor and a second pull-down drive transistor. When an inductor starts to discharge, the first pull-down current and the second pull-down current jointly pull down a gate terminal of the power switch transistor, such that the power switch transistor is in a cut-off state; after a set time, the first pull-down current is turned off; and when the inductor ends discharging, a parasitic capacitance of the power switch transistor couples with the drop signal, and when the drop signal is detected, the pull-up current pulls up the gate terminal of the power switch transistor, such that the power switch transistor is in a turn-on state.

A switch control circuit and a switch control system includes a plurality of parallel-connected signal processing units. A first voltage signal and second voltage signal control turning-on and turning-off of the first controllable switch, and converting the first voltage signal into a third voltage signal; and the third voltage signal being connected with the first port of the controller; and the controller, configured to send a switch control instruction to a to-be-controlled terminal based on the third voltage signal. This circuit converts a electrical signal of a high voltage in strong electricity into a stable electrical signal of a low voltage in weak electricity, implements multiplex switch control in conjunction with the controller, and only processes voltage signals in the whole circuit, thereby avoiding processing signals of a plurality of types, and guaranteeing the reliability of the multiplex switch control.

Methods, systems, and devices for controlling a variable capacitor. One aspect features a variable capacitance device that includes a capacitor, a first transistor, a second transistor, and control circuitry. The control circuitry is configured to adjust an effective capacitance of the capacitor by performing operations including detecting a zero-crossing of an input current at a first time. Switching off the first transistor. Estimating a first delay period for switching the first transistor on when a voltage across the capacitor is zero. Switching on the first transistor after the first delay period from the first time. Detecting a zero-crossing of the input current at a second time. Switching off the second transistor. Estimating a second delay period for switching the second transistor on when a voltage across the capacitor is zero. Switching on the second transistor after the second delay period from the second time.

Example MOSFET circuits include a first metal-oxide-semiconductor field-effect transistor (MOSFET) having a gate, a source and a drain, and a second MOSFET coupled in series with the first MOSFET. The second MOSFET has a gate, a source and a drain. The MOSFET circuit also includes a controller configured to supply a same control signal to the gate of the first MOSFET and the gate of the second MOSFET to turn on or turn off the first MOSFET and the second MOSFET when a drain-source voltage of the first MOSFET and a drain-source voltage of the second MOSFET are substantially zero. Other MOSFET circuits and methods of operating MOSFET circuits are also disclosed.