System and method for limiting output current in a switching power supply
AssigneeChampion Microelectronics Corporation
InventorsJeffrey Hwang, Alland Chee
Life of this patent
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Abstract
A switching power supply comprises 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. An output current sensor is configured to monitor a level of an output current of the switching power supply. The opening and closing of the set of switches is controlled so as to maintain the output voltage at a desired level when the level of the output current is below the threshold and so as to limit the output current when the level of the output current exceeds the threshold.
Claims23
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.
A switching power supply comprising:
- one or more power supply stages configured to receive power from an input power source and to generate output voltages for powering a plurality of loads by alternately opening and closing a set of switches, each load provided with a respective output current;
- a multiple output current sensor configured to monitor a level of each output current, the output current sensor forming a current sense signal representative of the highest one of the output currents;
- and
- controller circuitry configured to control the opening and closing of the sets of switches so as to maintain each output voltage at a desired level when the level of the current sense signal is below a threshold and wherein the controller is configured to control the opening and closing of the set of switches so as to limit the output current when the level of the current sense signal exceeds the threshold.
The switching power supply according to clam 18, 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 highest one of the output currents exceeds the threshold.
A controller for a switching power supply comprising;
- means for generating switching signals for alternately opening and closing a set of switches using frequency modulation for forming an output voltage;
- means for monitoring a level of an output current;
- and
- means for controlling the switching signals so as to maintain the output voltage at a desired level when the level of the output current is below a threshold and to limit the output current when the level of the output current exceeds the threshold, wherein the means for controlling is configured to operate in a first mode in which the switching is performed above a resonant frequency of the switching power supply, the first mode employing a switching duty cycle, and wherein the means for controlling is configured to operate in a second mode in which the switching is performed below the resonant frequency and the switching duty cycle in the second mode is reduced from that of the first mode, and wherein the means for controlling is configured to operate in a third mode in which the switching duty cycle is 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.
Dependencies are inferred from the claim text.