Boost power supply having power factor correction circuit
First Claim
1. In a boost power supply having a diode-rectifying bridge, an inductor, diode and filter capacitor connector in series with said bridge, a shunting switch in parallel with the series combination of said diode and said filter capacitor, an improved power factor correction circuit comprising:
- current-sensing means for generating a current-indicating signal indicative of the current flowing into said power supply circuit;
reference waveform generating means producing first and second reference waveforms, each a function of a sinusoidal voltage applied to said bridge, said first reference waveform being larger than said second reference waveform by a predetermined offset voltage; and
switch control means receiving said reference waveforms and the output of said current-sensing means for closing said shunting switch when the input current falls to said second reference waveform and for opening said shunting switch when said reference current rises to said first reference waveform.
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Accused Products
Abstract
A boost power supply having a full-wave rectifier driving an inductor, diode, and the parallel combination of a filter capacitor and load. A shunting switch connected between the inductor and diode is periodically closed to draw current through the inductor, thereby charging the inductor. The switch is then opened so that the inductor, while discharging, generates a relatively high voltage which is applied to the load and filter capacitor through the diode. The shunting switch is opened and closed in a manner which causes the input current to follow a sinusoidal waveform in phase with the input voltage with an amplitude that maintains the output voltage of the power supply constant. Specifically, a harmonically pure sinusoidal waveform is multiplied by a voltage inversely proportional to the output voltage. An offset is then added and subtracted to this waveform to generate respective positive and negative reference waveforms which are both in phase with the input voltage but differ slightly in magnitude from each other. A signal indicative of the input current is compared to the positive and negative reference waveforms to open the shunting switch when the input current reaches the level of the positive reference waveform and to close the shunting switch when the input current falls to the level of the negative reference waveform. In order to maintain the operating frequency of the switch constant, the difference between the positive and negative reference waveforms may be varied throughout the sinusoidal cycle so that the time for the inductor to charge to the positive reference waveform and discharge to the negative reference waveform is constant.
127 Citations
17 Claims
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1. In a boost power supply having a diode-rectifying bridge, an inductor, diode and filter capacitor connector in series with said bridge, a shunting switch in parallel with the series combination of said diode and said filter capacitor, an improved power factor correction circuit comprising:
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current-sensing means for generating a current-indicating signal indicative of the current flowing into said power supply circuit; reference waveform generating means producing first and second reference waveforms, each a function of a sinusoidal voltage applied to said bridge, said first reference waveform being larger than said second reference waveform by a predetermined offset voltage; and switch control means receiving said reference waveforms and the output of said current-sensing means for closing said shunting switch when the input current falls to said second reference waveform and for opening said shunting switch when said reference current rises to said first reference waveform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A high power factor, voltage-regulated boost power supply circuit comprising:
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a diode-rectifying bridge connected to a sinusoidal power source; an inductor, diode, and load connected in series with each other and with said bridge; a filter capacitor connected in parallel with said load; a shunting switch connected in parallel with the series combination of said diode and filter capacitor to selectively shunt said diode, load, and filter capacitor, thereby alternately charging and discharging said inductor; voltage-sensing means generating an output voltage feedback signal that is inversely proportional to the deviation of the voltage at the output of said power supply circuit from a predetermined reference voltage; current-sensing means for generating a current feedback signal indicative of the input current to said power supply circuit; reference waveform-generating means for producing a reference waveform that is a function of the sinusoidal waveform applied to said bridge; multiplying means receiving the output of said reference waveform-generating means and the output of said voltage-sensing means for generating a scaled reference waveform that is proportional to the product of said reference waveform and said voltage feedback signal; offset-generating means for adding and subtracting an offset voltage to said scaled reference waveform, thereby providing respective first and second reference waveforms; comparator means receiving said first and said second reference waveforms, respectively, on one input and said current feedback signal on their other inputs; and shunting switch control means connected to the outputs of said first and second comparator means for closing said shunting switch when said second comparator means determines that said current feedback signal has fallen to the level of said second reference waveform and for opening said shunting switch when said first comparator means determines that said current feedback signal has risen to the level of said first reference waveform. - View Dependent Claims (14, 15, 16, 17)
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Specification