Auto resonant driver for wireless power transmitter sensing required transmit power for optimum efficiency

摘要

An auto-resonant driver for a transmitter inductor drives the inductor at an optimal frequency for maximum efficiency. The transmitter inductor is magnetically coupled, but not physically coupled, to a receiver inductor, and the current generated by the receiver inductor is used to power a load. The system may be used, for example, to remotely charge a battery (as part of the load) or provide power to motors or circuits. A feedback circuit is used to generate the resonant driving frequency. A detector in the transmit side wirelessly detects whether there is sufficient current being generated in the receiver side to achieve regulation by a voltage regulator powering the load. This point is achieved when the transmitter inductor peak voltage suddenly increases as the driving pulse width is ramped up. At that point, the pulse width is held constant for optimal efficiency.

主权项

1. A power transmission system for wirelessly supplying power to a load comprising:
a transmitter inductor; a transmitter capacitor connected to the transmitter inductor to create a tank circuit having a resonant frequency; a first switch coupled to a first node of the tank circuit and to a first voltage to cause the tank circuit to be intermittently charged; a second switch coupled to the first node of the tank circuit and to a second voltage to cause the tank circuit to be intermittently discharged; and a feedback circuit for switching the power switch, the feedback circuit comprising:
a first comparator coupled to the first voltage and to the first node and having a first comparator output terminal;a second comparator coupled to the second voltage and to the first node and having a second comparator output terminal;a latch having a first latch input terminal coupled to the first comparator output terminal;the latch having a second latch input terminal coupled to the second comparator output terminal; anda latch output terminal automatically generating switching signals for the first switch and the second switch at the resonant frequency,wherein the first comparator, second comparator, and latch are configured such that positive and negative currents flow through the inductor as the first switch and the second switch are switched, wherein,a. at a negative to positive inductor current transition while the second switch is on, the first node goes from above the second voltage to below the second voltage, triggering the second comparator and the latch and turning on the first switch, wherein,b. at a positive to negative inductor current transition while the first switch is on, the first node goes from below the first voltage to above the first voltage, triggering the first comparator and the latch and turning on the second switch, and wherein,c. steps a and b repeat.