METHOD AND APPARATUS FOR SENSING A CURREN FOR VARYING IMPEDANCE LOADS
First Claim
Patent Images
1. An apparatus comprising:
- a class-D amplifier having a low-side recycling mode, a pair of low-side NMOS transistors, and a pair of output terminals;
a sample-and-hold (S/H) that is coupled to the pair of output terminals, wherein the S/H circuit samples a voltage on each of the pair of output terminals of the class-D amplifier when its associated low-side NMOS transistor is actuated;
a current generator that is coupled to the S/H circuit, wherein the current generator uses the voltages on the pair of output terminals sampled by the S/H circuit to minor the drain-source voltages of the pair of low-side NMOS transistors on a pair of sense transistors, and wherein the drain-source voltages mirrored on the pair of sense transistors generates a pair of sense currents; and
a current-to-voltage (I-to-V) converter that is coupled to the current generator so as to convert the sense currents to a sense voltage.
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Abstract
Recently, there has been an increased desire to measure load currents of class-D amplifiers to improve performance. The traditional solution has been to include one or more discrete components in series with the load, but this degrades performance. Here, however, circuit is provided (which includes sample-and-hold circuit) that accurately measures load currents without inhibiting performance and that is not inhibited by the phase differences between the load voltage and load current.
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Citations
20 Claims
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1. An apparatus comprising:
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a class-D amplifier having a low-side recycling mode, a pair of low-side NMOS transistors, and a pair of output terminals; a sample-and-hold (S/H) that is coupled to the pair of output terminals, wherein the S/H circuit samples a voltage on each of the pair of output terminals of the class-D amplifier when its associated low-side NMOS transistor is actuated; a current generator that is coupled to the S/H circuit, wherein the current generator uses the voltages on the pair of output terminals sampled by the S/H circuit to minor the drain-source voltages of the pair of low-side NMOS transistors on a pair of sense transistors, and wherein the drain-source voltages mirrored on the pair of sense transistors generates a pair of sense currents; and a current-to-voltage (I-to-V) converter that is coupled to the current generator so as to convert the sense currents to a sense voltage. - View Dependent Claims (2, 3)
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4. An apparatus comprising:
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an H-bridge having a first input terminal, a second input terminal, a first output terminal, and a second output terminal; a first driver that is coupled to provide a first control signal to the first terminal of the H-bridge; a second driver that is coupled to provide a second control signal to the second terminal of the H-bridge; an S/H circuit that is coupled to the first driver, second driver, the first output terminal of the H-bridge, and the second output terminal of the H-bridge, wherein the S/H circuit samples a first output voltage from the first output terminal of the H-bridge based at least in part on the state of the first control signal, and wherein the S/H circuit samples a second voltage from the second output terminal of the H-bridge based at least in part on the state of the second control signal; a current generator including; a first amplifier having a first input terminal, a second terminal, and an output terminal, wherein the first input terminal of the first amplifier is coupled to the S/H circuit; a second amplifier having a first input terminal, a second terminal, and an output terminal, wherein the first input terminal of the second amplifier is coupled to the S/H circuit; a first transistor having a first passive electrode, a second passive electrode, and a control electrode, wherein the control electrode of the first transistor is coupled to the output terminal of the first amplifier; a second transistor having a first passive electrode, a second passive electrode, and a control electrode, wherein first passive electrode of the second transistor is coupled to the second passive electrode of the first transistor; a third transistor having a first passive electrode, a second passive electrode, and a control electrode, wherein the control electrode of the third transistor is coupled to the output terminal of the second amplifier; and a fourth transistor having a first passive electrode, a second passive electrode, and a control electrode, wherein first passive electrode of the fourth transistor is coupled to the second passive electrode of the third transistor; and an I-to-V converter that is coupled to the first passive electrodes of the first and third transistors. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. An apparatus comprising:
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a class-D amplifier having; a negative output terminal; a positive output terminal; a first NMOS transistor that is coupled to the negative output terminal at its drain and that is controlled by a first control signal; a second NMOS transistor that is coupled to the positive output terminal at its drain and that is controlled by a second control signal; an S/H circuit that is coupled to the negative output terminal and the positive output terminal, wherein the S/H circuit samples the voltage on the negative output terminal when the first NMOS transistor is actuated, and wherein the S/H circuit samples the voltage on the positive output terminal when the second NMOS transistor is actuated; a current generator having; a first amplifier having a first input terminal, a second terminal, and an output terminal, wherein the first input terminal of the first amplifier is coupled to the S/H circuit; a second amplifier having a first input terminal, a second terminal, and an output terminal, wherein the first input terminal of the second amplifier is coupled to the S/H circuit; a third NMOS transistor that is coupled to the output terminal of the first amplifier at its gate; a fourth NMOS transistor that is coupled to the source of the third NMOS at its drain; a fifth NMOS transistor that is coupled to the output terminal of the second amplifier at its gate; a sixth NMOS transistor that is coupled to the source of the fifth NMOS at its drain; and an I-to-V converter that is coupled to the drains of the third and fifth NMOS transistors. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A method comprising:
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actuating at least one of a first and a second low-side NMOS transistors within a class-D amplifier; sampling voltages on each of positive and negative output terminals of the class-D amplifier when its associated low-side NMOS transistors is actuated; generating first and second sense currents from the first and second low-side NMOS transistors of the class-D amplifier, respectively; and converting the first and second sense currents into a sense voltage. - View Dependent Claims (18, 19, 20)
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Specification