Over current protection circuit and method
First Claim
1. An integrated circuit, comprising:
- a voltage controlled oscillator for providing pulses at a frequency corresponding to a voltage received at an feedback input pin;
a first switching output for driving a high-side driver transistor at a frequency proportional to the pulses;
a second switching output for driving a low-side driver transistor at a frequency proportional to the pulses, the second switching output being a non-overlapping inverted signal from the first switching output;
a current sense input pin for receiving a voltage corresponding to current flowing in an external load circuit;
a latch off function that outputs a latch off signal when the voltage received at the current sense input pin is greater than a first threshold voltage;
a VCO influence function outputting a VCO influence signal that increases the frequency of the VCO when the voltage input to the current sense input pin is greater than a second threshold voltage, and that decreases the frequency of the VCO when the voltage input to the current sense input pin is less than a third threshold voltage, the second threshold voltage being less than the first threshold voltage and greater than the third threshold voltage; and
a switch off function that outputs a switch off signal when the voltage at the feedback input pin exceeds a maximum operating voltage for a time period greater than a blanking time period.
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Accused Products
Abstract
Circuit and method for providing over-current and overloading protection with a single additional pin. A converter controller circuit is provided that includes a voltage controlled oscillator and outputs upper and lower gating signals for driving the upper and lower driving transistors in a voltage converter, for example, in an inductor-inductor capacitor half-bridge circuit topology. A current sense input pin of the circuit receives a voltage corresponding to the current flowing in the half-bridge circuit. A feedback input pin has an external capacitor coupled to it and receives a voltage from an output voltage sensor at the output terminals. Over-current protection is provided by sensing the voltage at the current sense input pin with no external components needed. Overload protection is provided by utilizing the external feedback capacitor and the feedback input pin during overload conditions. Methods for providing over-current and overload protection are disclosed.
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Citations
34 Claims
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1. An integrated circuit, comprising:
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a voltage controlled oscillator for providing pulses at a frequency corresponding to a voltage received at an feedback input pin; a first switching output for driving a high-side driver transistor at a frequency proportional to the pulses; a second switching output for driving a low-side driver transistor at a frequency proportional to the pulses, the second switching output being a non-overlapping inverted signal from the first switching output; a current sense input pin for receiving a voltage corresponding to current flowing in an external load circuit; a latch off function that outputs a latch off signal when the voltage received at the current sense input pin is greater than a first threshold voltage; a VCO influence function outputting a VCO influence signal that increases the frequency of the VCO when the voltage input to the current sense input pin is greater than a second threshold voltage, and that decreases the frequency of the VCO when the voltage input to the current sense input pin is less than a third threshold voltage, the second threshold voltage being less than the first threshold voltage and greater than the third threshold voltage; and a switch off function that outputs a switch off signal when the voltage at the feedback input pin exceeds a maximum operating voltage for a time period greater than a blanking time period. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A circuit, comprising:
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an upper driver transistor coupled between a positive power supply and a node and receiving an upper gate control signal; a lower driver transistor coupled between the node and a ground potential and receiving a lower gate control signal; a first inductor having an input terminal coupled to the node and having an output terminal; a second inductor having an input terminal coupled to the first inductor output terminal and having an output terminal, the first inductor being part of a transformer having a second inductor coupled to a voltage output; a capacitor coupled to the output terminal of the second inductor and coupled to the ground potential, the first inductor, second inductor and capacitor forming an LLC circuit; a current sense resistor coupled in series with the LLC circuit and outputting a current sense voltage proportional to the current flowing in the LLC circuit; and a converter integrated circuit, comprising; an internal voltage controlled oscillator (VCO) and circuits outputting the upper gate control signal at an UPPER output pin and the lower gate control signal at a LOWER output pin, the upper and lower gate control signals being non-overlapping pulses of a frequency determined by the VCO frequency; an over-current protection coupled to a current sense voltage input pin for receiving the current sense voltage, and outputting a latch off signal when the current sense voltage is greater than a first threshold voltage, and outputting a VCO influence signal to the VCO to change the frequency of the VCO when the voltage at the current sense voltage input pin is above a second threshold voltage that is less than the first threshold voltage, and outputting an opposite VCO influence signal when the voltage at the current sense voltage input pin is below a third threshold voltage that is lower than the second threshold voltage; and an overload protection function coupled to a feedback voltage input pin outputting a switch off signal when the voltage at the feedback voltage input pin is greater than a fourth threshold voltage for a time period that exceeds the sum of a first and an extended blanking time. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. A method, comprising:
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providing an upper gate control signal to an upper driving transistor coupled to supply a voltage to a node; providing a lower gate control signal to a lower driving transistor coupled between the node and a ground reference; coupling an inductor-inductor capacitor (LLC) circuit to the node and to an output voltage; providing a circuit supplying the upper and lower gate control signals to the upper and lower driving transistors responsive to the frequency of a voltage controlled oscillator (VCO), the upper and lower gate controls signals being non overlapping periodic signals with a frequency proportional to the VCO frequency; providing a voltage feedback at a feedback input to the circuit from the voltage output to the circuit, the circuit modifying the frequency of the VCO responsive to the feedback input; coupling an external feedback capacitor between the feedback input pin and the ground potential; providing a current sense voltage proportional to the current flowing in the LLC circuit at a current sense input to the circuit; outputting a latch off signal from an over-current protection function in the circuit when the voltage at the current sense input is greater than a first threshold voltage, and outputting a VCO influence signal for modifying the VCO frequency when the voltage at the current sense input is greater than a second threshold voltage that is less than the first threshold voltage, and outputting the VCO influence signal modifying the VCO frequency when the voltage at the current sense input is less than a third threshold voltage that is less than the second threshold voltage; and outputting a switch off signal to provide overload protection for the LLC circuit when the voltage at the feedback input is greater than a fourth threshold voltage for a time exceeding a blanking time period. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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25. A method of providing overload (OLP) and overcurrent (OCP protection for a half-bridge DC convertor circuit having a DC output, comprising:
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providing an inductor-inductor capacitor (LLC) circuit coupled to a node; providing an upper driver transistor coupling the node to a positive power supply, responsive to a periodic upper gating signal having a duty cycle; providing a lower driver transistor coupling the node to a ground potential, responsive to a periodic lower gating signal having the duty cycle and being non overlapping with the upper gating signal; providing an integrated circuit that outputs the upper and lower gating signals of said DC convertor circuit, the integrated circuit receiving only a current sense voltage input and a feedback voltage input as signals necessary for controlling said OLP and OCP protection; coupling an external feedback capacitor to the feedback voltage input; coupling a feedback sensor to the feedback voltage input; and wherein the integrated circuit provides the upper and lower gating signals responsive to the frequency of an on board voltage controlled oscillator (VCO), and the integrated circuit provides over-current protection responsive to a voltage at the current sense voltage input that corresponds to the current flowing in the LLC circuit. - View Dependent Claims (33, 34)
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26. A method, comprising:
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providing an inductor-inductor capacitor (LLC) circuit coupled to a node; providing an upper driver transistor coupling the node to a positive power supply, responsive to a periodic upper gating signal having a duty cycle; providing a lower driver transistor coupling the node to a ground potential, responsive to a periodic lower gating signal having the duty cycle and being non overlapping with the upper gating signal; providing an integrated circuit that outputs the upper and lower gating signals, the integrated circuit having a current sense voltage input and a feedback voltage input; coupling an external feedback capacitor to the feedback voltage input; coupling a feedback sensor to the feedback voltage input; and wherein the integrated circuit provides the upper and lower gating signals responsive to the frequency of an on board voltage controlled oscillator (VCO), and the integrated circuit provides over-current protection responsive to a voltage at the current sense voltage input that corresponds to the current flowing in the LLC circuit, and further comprising; latching off the upper and lower gating signals to the upper and lower driver transistor when the voltage at the current sense input pin exceeds a first threshold voltage; and modifying the frequency of the VCO when the voltage input to the current sense voltage input pin is greater than a second threshold voltage that is less than the first threshold voltage, and modifying the frequency of the VCO oppositely when the voltage at the current sense input pin is less than a third threshold voltage that is less than the second threshold voltage. - View Dependent Claims (27, 28, 29, 30, 31)
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32. A circuit, comprising:
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an inductor-inductor capacitor half-bridge circuit coupled a node to deliver energy to a rectifier circuit with an output; an upper driver transistor coupling a positive power supply to the node responsive to a periodic upper gating signal; a lower driver transistor coupling the node to a ground reference responsive to a periodic lower gating signal, the lower gating signal being complementary to and non overlapping with the upper gating signal; a integrated circuit comprising; an upper output pin for outputting the upper output signal having a frequency corresponding to the frequency of an on board voltage controlled oscillator (VCO); a lower output pin for outputting the lower output signal having a frequency corresponding to the frequency of the VCO; a feedback voltage input pin for receiving an input voltage corresponding to the output voltage of the rectifier; and a current sense input pin for receiving a voltage corresponding to the current in the LLC half-bridge; and wherein the integrated circuit provides a first over-current protection function by stopping the outputs of the upper and lower gating signals when the voltage at the current sense input pins exceeds a first threshold voltage and provides a second over-current protection function by modifying the frequency of the VCO when the voltage at the current sense input is greater than a second threshold voltage that is less than the first threshold voltage and modifying the frequency of the VCO when the voltage t the current sense input is less than a third threshold voltage that is less than the second threshold voltage.
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Specification