Voltage regulator with load pole stabilization
First Claim
1. A voltage regulator circuit having an error amp, an amplifier, a pass transistor, and a feedback circuit, wherein the amplifier further comprises:
- a compensation capacitor coupled to the amplifier; and
a switched capacitor having a clock input coupled to an output of the amplifier, the switched capacitor operable to vary the zero of the voltage regulator as a function of the current draw on the voltage regulator output.
1 Assignment
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Accused Products
Abstract
A voltage regulator with load pole stabilization is disclosed. The voltage regulator consists of an error amplifier, an integrator which includes a switched capacitor, a pass transistor, and a feed back circuit. In one embodiment, the integrator circuit includes an amplifier, a capacitor, and a switched capacitor which is driven by a voltage controlled oscillator. The voltage controlled oscillator changes its frequency of oscillation proportional to the output current. In another embodiment, the switched capacitor is driven by a current controlled oscillator whose frequency of oscillation is also proportional to the output current of the voltage regulator. When the output current demand is large, the controlled oscillators increase the frequency which decreases the effective resistance of the switched capacitor thereby changing the frequency of the zero to respond to the change in the load pole. Conversely, the effective resistance is increased as the current demand is decreased, also to respond to the decrease in load pole. Consequently, the disclosed voltage regulator has high stability without consuming excess power.
50 Citations
27 Claims
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1. A voltage regulator circuit having an error amp, an amplifier, a pass transistor, and a feedback circuit, wherein the amplifier further comprises:
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a compensation capacitor coupled to the amplifier; and a switched capacitor having a clock input coupled to an output of the amplifier, the switched capacitor operable to vary the zero of the voltage regulator as a function of the current draw on the voltage regulator output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A voltage regulator circuit comprising:
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an error amp having a noninverting input for receiving a reference voltage, an inverting input, and an output; an amplifier with an input coupled to the output of the error amp and having an output; a compensation capacitor coupled to the amplifier; a switched capacitor having a clock input coupled to the output of the amplifier and operable to vary the zero of the voltage regulator as the output current of the voltage regulator varies; a pass transistor having a current path with a first end coupled to a voltage source and a second end coupled to an output of the voltage regulator, and having a control input coupled to the output of the amplifier; and a feedback path coupled between the second end of the conductive path of the pass transistor and the inverting input of the error amp. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method for stabilizing a regulating voltage from a voltage regulator with a load pole by generating a load pole cancelling zero comprising the steps of:
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generating a clock signal having a frequency that varies with the load current of the voltage regulator; and driving a switched capacitor with the generated clock signal to vary the zero of the voltage regulator as a function of the load current. - View Dependent Claims (18, 19)
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20. A power supply which includes a voltage regulating circuit comprising:
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an error amp having a noninverting input for receiving a reference voltage, an inverting input, and an output; an integrator circuit comprising; an amplifier with an input coupled to the output of the error amp and having an output, a switched capacitor and a capacitor coupled in series across the input and output of the amplifier, the switched capacitor operable to vary the zero of the voltage regulating circuit as a function of the current draw on the voltage regulating circuit; a pass transistor having a current path with a first end coupled to a voltage source and a second end, and having a control element coupled to the output of the integrator circuit; and a feedback circuit coupled between the second end of the conductive path of the pass transistor and the inverting input of the error amp.
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21. A voltage regulator circuit comprising:
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an error amp having a first input for receiving a reference voltage, a second input, and an output; an amplifier having an input coupled to the output of the error amp and having an output; a compensation capacitor coupled to the amplifier; a switched capacitor coupled to the amplifier and having a clock input; a variable oscillator having an input coupled to the output of the amplifier and an output coupled to the clock input of the switched capacitor, the variable oscillator and the switched capacitor together operable to vary the zero of the voltage regulator to track the varying load pole of the voltage regulator; and a feedback path having one end coupled to the output of the amplifier and another end coupled to the second input of the error amp. - View Dependent Claims (22, 23, 24, 25, 26)
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27. An automatic stabilization circuit for a voltage regulator having a regulating element coupled to an output terminal and connectable to a load, a feed back element, and an amplifier having input and output terminals, the automatic stabilization circuit comprising:
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a variable oscillator having a control input coupled to the output terminal and an oscillator output generating a variable frequency clock signal whose frequency is dependent on changes in the load; and a switched capacitor circuit coupled to the amplifier to provide variable compensation to the amplifier, the switched capacitor circuit receiving the variable frequency clock signal and generating a variable impedance whose value varies in response to changes in the frequency of the variable frequency clock signal.
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Specification