Abstract: In a wireless power transfer operation, the operating parameters are adjusted to improve efficiency by reducing the transmit and receive coil currents as follows. First, the transmitter causes the receiver to reduce the receive coil current to the lowest value based on the transmitter/receiver communication while still delivering the same amount of power to the load as before the AC current was adjusted to the minimum value. Then the transmitter may change the operating parameters to increase or preserve the power provided to the receiver without decreasing efficiency or with only small decrease in efficiency, or with increasing the efficiency. For example, the transmitter may increase the VBRG voltage (the DC voltage powering the transmit coil) or the operating frequency to maintain or increase output power levels at lower or the same AC and DC current levels. Other features are also provided.

Abstract: A wireless power circuit is presented that includes a transmit coil coupled to a first node; a receive coil coupled to the first node; a switch circuit coupled to the transmit coil and the receive coil opposite the first node, the switch switching the transmit coil to a second node in a transmit mode and switching the receive coil to the second node in a receive mode; a controller coupled to the first node and the second node, the controller coupled to provide signals to the switch circuit; and a self-start circuit coupled to the receive coil (or Tx coil) that automatically selects one of the coils to be used, the self-start circuit providing power to the switch circuit to hold the switch circuit in the receive mode (or predefined coil to be selected by default).

Abstract: An isolating self-oscillation flyback converter includes a coupling transformer T1, a FET TR1, a transistor TR2, a photoelectric coupling isolator OC1 and a load feedback circuit Adj. The common polarity terminal of a feedback winding Nfb of the coupling transformer T1 is connected to the gate of the FET TR1 via a capacitance C1 and a resistance R2, and connected to the base of the transistor TR2 via a capacitance C2. The base of the transistor TR2 is also connected to the emitter of the photoelectric coupling isolator OC1. The photoelectric coupling isolator OC1 is connected to the positive terminal of the output voltage. The opposite polarity terminal of the feedback winding Nfb is connected to the collector of the photoelectric coupling isolator OC1 via a resistance R5, and connected to ground via a capacitance C5. The common polarity terminal of the feedback winding Nfb is also connected to the cathode of a diode D, and the anode of the diode D is connected to ground.

Abstract: An isolating self-oscillation flyback converter includes a coupling transformer T1, a FET TR1, a transistor TR2, a photoelectric coupling isolator OC1 and a load feedback circuit Adj. The common polarity terminal of a feedback winding Nfb of the coupling transformer T1 is connected to the gate of the FET TR1 via a capacitance C1 and a resistance R2, and connected to the base of the transistor TR2 via a capacitance C2. The base of the transistor TR2 is also connected to the emitter of the photoelectric coupling isolator OC1. The photoelectric coupling isolator OC1 is connected to the positive terminal of the output voltage. The opposite polarity terminal of the feedback winding Nfb is connected to the collector of the photoelectric coupling isolator OC1 via a resistance R5, and connected to ground via a capacitance C5. The common polarity terminal of the feedback winding Nfb is also connected to the cathode of a diode D, and the anode of the diode D is connected to ground.