An inductive power receiver including: a resonant circuit having a receiving coil and a tuning network; and rectifier coupled to the resonant circuit and adapted to provide a DC output to a load, wherein the tuning network is controlled to regulate the power provided to the load and includes: a series tuning branch connected from the receiving coil to the rectifier; and a variable shunt tuning branch connected from a node between the series tuning branch and the receiving coil to a common ground on the DC output side of the rectifier.

A control circuit includes: an input terminal for receiving an input AC voltage; a voltage decreasing unit for decreasing the input AC voltage; an A-D converter for converting the decreasing AC voltage to a DC voltage; a driving unit for receiving the DC voltage and to driving a motor, a detecting unit for detecting the DC voltage; and a current shunt unit configured to be conductive to lower the DC voltage at the output terminal of the A-D converter to a voltage which is less than a threshold voltage when the detecting signal indicates that the detected DC voltage exceeds the threshold value. A motor device includes the control circuit and a motor.

The number of constituent components is reduced so as to provide a small-size and inexpensive electric-power conversion system. The electric-power conversion system is provided with an inverter circuit (14) connected with the rear stage of an AC power source, a smoothing capacitor (22) connected with the rear stage of the inverter circuit (14) by way of a rectifying device (20), a charging switch (2) that is connected with the front stage of the inverter circuit (14), that inputs an electric quantity based on an output of the AC power source (1) to the inverter circuit (14) when being turned on, and that cuts off an input of the electric quantity to the inverter circuit (14) when being turned off, and an inrush current prevention circuit (7) having an inrush current prevention switch (3) and an inrush current prevention resistor (4) that is connected in series with the rear stage of the inrush current prevention switch (3); the electric-power conversion system is characterized in that the inrush current prevention circuit (7) is connected in parallel with the charging switch (2).

The number of constituent components is reduced so as to provide a small-size and inexpensive electric-power conversion system. The electric-power conversion system is provided with an inverter circuit (14) connected with the rear stage of an AC power source, a smoothing capacitor (22) connected with the rear stage of the inverter circuit (14) by way of a rectifying device (20), a charging switch (2) that is connected with the front stage of the inverter circuit (14), that inputs an electric quantity based on an output of the AC power source (1) to the inverter circuit (14) when being turned on, and that cuts off an input of the electric quantity to the inverter circuit (14) when being turned off, and an inrush current prevention circuit (7) having an inrush current prevention switch (3) and an inrush current prevention resistor (4) that is connected in series with the rear stage of the inrush current prevention switch (3); the electric-power conversion system is characterized in that the inrush current prevention circuit (7) is connected in parallel with the charging switch (2).

Disclosed are an alternating current rectifying circuit and an alternating current rectifying method for driving an LED module. The method comprises: when an alternating current module is in a positive half cycle, after an alternating current output by the alternating current module is rectified, outputting the alternating current to a positive half cycle rectifying branch circuit of an external LED module; when the alternating current module is in a negative half cycle, carrying out charging according to the alternating current output by the alternating current module, and when the alternating current module is in the positive half cycle, carrying out discharging, and outputting the alternating current to a positive half cycle feed branch circuit of the external LED module; when the alternating current module is in the negative half cycle, rectifying the alternating current output by the alternating current module, and outputting the alternating current to a negative half cycle rectifying branch circuit of the external LED module; when the alternating current module is in the positive half cycle, carrying out charging according to the alternating current output by the alternating current module, and when the alternating current module is in the negative half cycle, carrying out discharging, and outputting the alternating current to a negative half cycle feed branch circuit of the external LED module. By using the present invention, stability of an output voltage can be improved, and luminous efficiency of the LED module can be improved.

Disclosed is a power supply circuit, including: a voltage source, providing an input voltage; a switch unit, a first terminal thereof being electrically coupled to a first terminal of the voltage source; a first capacitor, having an initial voltage, a first terminal thereof being electrically coupled to a second terminal of the switch unit, and a second terminal thereof being electrically coupled to a second terminal of the voltage source; a reference signal generating unit, configured to generate a first reference signal according to a first time, and a difference between a peak value of the input voltage and the initial voltage of the first capacitor; and a control unit, configured to obtain a real-time voltage of the first capacitor, and generate a first control signal for controlling the switch unit according to the first reference signal and the real-time voltage of the first capacitor.

An electronic transformer includes a first forward rectifier, a second forward rectifier, a third forward rectifier and a backward rectifier. The first forward rectifier is coupled between a first-phase power and a first output terminal. The second forward rectifier is coupled between a second-phase power and the first output terminal. The third forward rectifier is coupled between a third-phase power and the first output terminal. The backward rectifier is coupled between a neutral line and a second output terminal. The first forward rectifier, the second forward rectifier, and the third forward rectifier are configured to half-wave rectify the first-phase power, the second-phase power, and the third-phase power to generate rectified first-phase to third-phase power sources, and superimpose the rectified first-phase to third-phase power sources on the first output end to serve as an output voltage of the electronic transformer.

A playback circuit including a digital-to-analog converter (DAC), an amplifying output circuit and a control circuit coupled to both is provided. The DAC is configured to convert an input playback audio signal into an input analog playback audio signal according to a first control signal for controlling an upper limit of power consumption of the DAC. The amplifying output circuit is coupled to the DAC and configured to generate an output playback audio signal according to the input analog playback audio signal and a second control signal for controlling an upper limit of power consumption of the amplifying output circuit. The control circuit is configured to generate the first control signal and second control signal according to a volume value of the input playback audio signal, thereby controlling the upper limit of power consumption of the DAC and the upper limit of power consumption of the amplifying output circuit.