Bulk filter capacitor discharge in a switching power supply
First Claim
1. A power supply supplying power at a regulated DC voltage, comprising:
- an input for receiving current supplied from a power source;
a bulk filter capacitor;
a switching converter coupled to the bulk filter capacitor, the switching converter providing at an output thereof, current at a regulated DC voltage level, the switching converter including;
a main switching element electrically coupled to the bulk filter capacitor, wherein during a modulation mode of the switching converter, the main switching element is made conductive and non conductive in accordance with a duty cycle to control the DC voltage level of the output;
a discharge control circuit which in response to a cessation of current supplied from the power source to the input, makes the main switching element conductive at least until the bulk filter capacitor has discharged through the main switching element to a first charge level.
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Accused Products
Abstract
A discharge control circuit for a power supply switching converter that, in response to a cessation of current from an AC power source, makes conductive a main switching element of the switching converter to discharge the bulk filter capacitor through the main switching element to a charge level that meets safety standards. The discharge control unit includes a current limiting circuit for limiting the discharge current through the main switching element in which the rate of rise of the discharge current is controlled with the use of an RC circuit. The discharge control unit also includes a state machine that activates the current limiting circuit in response to a cessation of the modulation mode of the switching converter. The discharge control circuit also includes a reset circuit for placing the state machine in a known state during the startup of the switching converter.
57 Citations
44 Claims
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1. A power supply supplying power at a regulated DC voltage, comprising:
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an input for receiving current supplied from a power source; a bulk filter capacitor; a switching converter coupled to the bulk filter capacitor, the switching converter providing at an output thereof, current at a regulated DC voltage level, the switching converter including; a main switching element electrically coupled to the bulk filter capacitor, wherein during a modulation mode of the switching converter, the main switching element is made conductive and non conductive in accordance with a duty cycle to control the DC voltage level of the output; a discharge control circuit which in response to a cessation of current supplied from the power source to the input, makes the main switching element conductive at least until the bulk filter capacitor has discharged through the main switching element to a first charge level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A computer system comprising:
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a system processor; a power supply, the power supply supplying current to the computer system including the system processor at a regulated DC voltage, the power supply including; an input for receiving current supplied from a power source; a bulk filter capacitor; a first switching converter electrically coupled to the bulk filter capacitor, the first switching converter providing at an output, current at a regulated DC voltage level, the first switching converter including; a main switching element electrically coupled to the bulk filter capacitor, wherein during a modulation mode of the first switching converter, the main switching element is made conductive and non conductive in accordance with a duty cycle to control the DC voltage level of the output; a discharge control circuit, which in response to a cessation of current supplied from the power source to the input, makes the switching element conductive at least until the bulk filter capacitor has discharged through the main switching element to a first charge level. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method for discharging a bulk filter capacitor in a DC power supply comprising:
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supplying current from a power source to an input of the power supply; charging a bulk filter capacitor in the power supply; making a main switching element electrically coupled to the capacitor conductive and non conductive in accordance with a duty cycle to provide current at a regulated DC voltage level at an output of the power supply; terminating the supply of current from the power source to the input; in response to the termination of the supply of current, making conductive the main switching element to discharge the bulk filter capacitor to at least a first charge level. - View Dependent Claims (34, 35)
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36. A power supply supplying power at a regulated DC voltage, comprising:
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an input for receiving current supplied from a first power source; a bulk filter capacitor; a switching converter coupled to the bulk filter capacitor, the switching converter providing at an output, current at a regulated DC voltage level, the switching converter including; a main switching element electrically coupled to the bulk filter capacitor, the main switching element being made conductive and non conductive in accordance with a duty cycle to control the DC voltage level of the output during a modulation mode; means operative, in response to a cessation of current supplied from the power source to the input, for making the main switching element conductive at least until the bulk filter capacitor has discharged through the main switching element to a first charge level.
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37. A converter control circuit comprising:
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a pulse generator circuit, which when activated, provides a pulse signal having a duty cycle to make a switching element of a switching power supply converter conductive and non-conductive in accordance with the duty cycle to control the DC voltage level of an output of a switching power supply; a discharge control circuit, which when activated, provides a discharge signal to make the switching element conductive at least until a bulk filter capacitor of the power supply has discharged through the main switching element to a first charge level; a pulse generator activation circuit, wherein the pulse generator activation circuit activates the pulse generator circuit and wherein the pulse generator activation circuit activates the discharge control circuit in response to a cessation of current supplied from a power source to an input of the power supply. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44)
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Specification