High voltage start-up circuit and method therefor
First Claim
1. A high voltage start-up circuit for a switchmode power supply comprising, in combination:
- switching means for turning off and on a high voltage input line of said start-up circuit and for limiting a current flow from said high voltage input line to an output of said start-up circuit;
comparator means coupled to said switching means for sending a signal to turn on said switching means when an output voltage of said start-up circuit falls below a first set value and for sending a signal to turn off said switching means when said output voltage falls below a second set value.
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Accused Products
Abstract
The present invention relates to a switchmode power supply (SMPS) high voltage start-up integrated circuit (IC) with output voltage sensing and output current limiting. The high voltage start-up IC allows low voltage pulse width modulated (PWM) controller ICs to operate directly off rectified AC lines of up to 450 VDC. The high voltage start-up IC allows PWM controller ICs to start-up with a start threshold larger than its operating voltage. The output voltage is monitored internally so that the internal high voltage switch turns off when the output voltage decreases below an internally set trip point voltage (Voff) The internal high voltage switch remains off and an external auxiliary voltage is generated and applied to the output voltage. If the output voltage falls below a lower set trip point voltage (Vreset) the internal high voltage switch turns back on. This allows the start-up circuit to reset itself when the PWM controller IC'"'"'s auxiliary voltage does not power up properly.
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Citations
15 Claims
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1. A high voltage start-up circuit for a switchmode power supply comprising, in combination:
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switching means for turning off and on a high voltage input line of said start-up circuit and for limiting a current flow from said high voltage input line to an output of said start-up circuit; comparator means coupled to said switching means for sending a signal to turn on said switching means when an output voltage of said start-up circuit falls below a first set value and for sending a signal to turn off said switching means when said output voltage falls below a second set value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of providing a high voltage start-up circuit for a switchmode power supply comprising the steps of:
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providing switching means for turning off and on a high voltage input line of said start-up circuit and for limiting a current flow from said high voltage input line to an output of said start-up circuit; providing comparator means coupled to said switching means for sending a signal to turn on said switching means when an output voltage of said start-up circuit falls below a first set value and for sending a signal to turn off said switching means when said output voltage falls below a second set value. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A high voltage start-up circuit for a switchmode power supply comprising, in combination:
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high voltage input line for supplying power to said start-up circuit; switching means coupled to said high voltage input line for turning off said high voltage input line by sensing a decrease in an output voltage of said start-up circuit; trip point setting means coupled to said switching means for resetting and turning on said high voltage input line; and current limiting means coupled to said high voltage input line for limiting current flow from said high voltage input line to an output of said start-up circuit.
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Specification