LLC converter and loss of inductive mode detection circuit
First Claim
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1. A power conversion system, comprising:
- a resonant circuit, comprising;
a series circuit including at least one inductance, a transformer primary winding, and at least one capacitance coupled in series with one another between a switching node and a constant voltage node, anda switching circuit including first and second switching devices coupled with one another between an input voltage node and the circuit ground node, the first switching device coupled between the input voltage node and the switching node and operative in a first state to selectively couple the switching node with the input voltage node and in a second state to decouple the switching node from the input voltage node according to a first switching control signal, the second switching device coupled between the switching node and the constant voltage node and operative in a first state to selectively couple the switching node with the constant voltage node and in a second state to decouple the switching node from the constant voltage node according to a second switching control signal;
a controller operatively coupled to provide the first and second switching control signals as modulated signals to the switching circuit in each of a plurality of switching cycles to modify a voltage at the switching node to control a converter output voltage;
a sensing circuit operatively coupled with the series circuit to provide a sense signal representing a resonant current flowing in the series circuit; and
a detection circuit operatively coupled with the sensing circuit to receive the sense signal and operative to selectively provide a detection signal or value to the controller in a first state if an amplitude of the sense signal is below a predetermined threshold in a predetermined portion of a given half cycle of a given one of the plurality of switching cycles and to provide the detection signal or value in a different second state if the amplitude of the sense signal is greater than or equal to the predetermined threshold in the predetermined portion of the given half cycle;
wherein the controller is operative to selectively modify the first and second switching control signals responsive to receiving the detection signal or value in the first state.
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Abstract
Methods, control apparatus and series resonant or LLC power conversion systems are presented in which a resonant series circuit current is compared with a threshold during a portion of a modulation switching cycle following turn on of a corresponding switching device and one or more indications or remedial actions are undertaken to modify modulation control of a switching circuit in response to a determination that the resonant current is below the threshold to facilitate our promote zero voltage switching or near-zero voltage switching and provide current reversal protection.
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Citations
22 Claims
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1. A power conversion system, comprising:
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a resonant circuit, comprising; a series circuit including at least one inductance, a transformer primary winding, and at least one capacitance coupled in series with one another between a switching node and a constant voltage node, and a switching circuit including first and second switching devices coupled with one another between an input voltage node and the circuit ground node, the first switching device coupled between the input voltage node and the switching node and operative in a first state to selectively couple the switching node with the input voltage node and in a second state to decouple the switching node from the input voltage node according to a first switching control signal, the second switching device coupled between the switching node and the constant voltage node and operative in a first state to selectively couple the switching node with the constant voltage node and in a second state to decouple the switching node from the constant voltage node according to a second switching control signal; a controller operatively coupled to provide the first and second switching control signals as modulated signals to the switching circuit in each of a plurality of switching cycles to modify a voltage at the switching node to control a converter output voltage; a sensing circuit operatively coupled with the series circuit to provide a sense signal representing a resonant current flowing in the series circuit; and a detection circuit operatively coupled with the sensing circuit to receive the sense signal and operative to selectively provide a detection signal or value to the controller in a first state if an amplitude of the sense signal is below a predetermined threshold in a predetermined portion of a given half cycle of a given one of the plurality of switching cycles and to provide the detection signal or value in a different second state if the amplitude of the sense signal is greater than or equal to the predetermined threshold in the predetermined portion of the given half cycle; wherein the controller is operative to selectively modify the first and second switching control signals responsive to receiving the detection signal or value in the first state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A control apparatus for operating a series resonant or LLC power conversion system with a series circuit and a switching circuit, the control apparatus comprising:
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a modulation controller operatively coupled to provide first and second switching control signals as alternating modulated signals to corresponding first and second switching devices of the power conversion system in each of a plurality of switching cycles to modify a voltage at a switching node to control a converter output voltage; and a detection circuit comprising an input for receiving a sense signal representing a resonant current flowing in the series circuit, and an output providing a detection signal or value to the controller in a first state if an amplitude of the sense signal is below a predetermined threshold in a predetermined portion of a given half cycle of a given one of the plurality of switching cycles and to provide the detection signal or value in a different second state if the amplitude of the sense signal is greater than or equal to the predetermined threshold in the predetermined portion of the given half cycle; wherein the controller is operative to selectively modify the first and second switching control signals to promote zero voltage switching or near-zero voltage switching operation of the first and second switching devices in response to receiving the detection signal or value in the first state. - View Dependent Claims (17, 18, 19)
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20. A method for controlling a resonant power conversion system, the method comprising:
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sensing a resonant current flowing in a series circuit of the power conversion system; determining whether the resonant current is below a predetermined threshold in a predetermined portion of a given modulation half cycle, the predetermined portion beginning a non-zero predetermined time after a switching device of the power conversion system is turned on and ending before the switching device is turned off; and in response to determining that the resonant current is below the predetermined threshold in the predetermined portion of the given modulation half cycle, selectively modifying at least one modulation switching control signal provided to the power conversion system to promote zero voltage switching or near-zero voltage switching operation of the switching device. - View Dependent Claims (21, 22)
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Specification