Patent ID: 9178439
Filing Date: 2015-11-03
Classification: H02H,H02M,Y02B

Abstract:
1. A switching power supply comprising: one or more power supply stages configured to receive power from an input power source and to generate an output voltage for powering a load by alternately opening and closing a set of switches, the one or more power supply stages comprising: a resonant tank having a resonant frequency; a switching inverter coupled to the resonant tank for charging the resonant tank with energy; and a synchronous rectifier coupled to the resonant tank and configured to draw power from the resonant tank for forming the output voltage; an output current sensor configured to monitor a level of an output current of the switching power supply, the output current sensor comprising a sensing impedance configured to receive a current that is representative of a level of the output current; and a controller configured to control switching of the switching inverter by controlling the opening and closing of the set of switches, wherein when the level of the output current is below a threshold, the controller controls the opening and closing of the set of switches to regulate the output voltage, and wherein in response to the level of the output current exceeding the threshold, the controller increases a frequency of opening and closing of the set of switches so as to limit the output current, and wherein the controller operates in a first mode in which the switching of the synchronous rectifier is performed above the resonant frequency of the resonant tank, the first mode employing a duty cycle for the synchronous rectifier, and wherein the controller operates in a second mode in which the switching of the synchronous rectifier is performed below the resonant frequency and the duty cycle of the synchronous rectifier in the second mode is reduced from that of the first mode, and wherein the controller operates in a third mode in which the duty cycle of the synchronous rectifier and the duty cycle of the switching inverter are reduced from that of the first mode and wherein the third mode is entered in response to the switching frequency exceeding a specified level, and wherein operation in the third mode is inhibited when the level of the output current exceeds the threshold.