Power factor improvement
First Claim
1. A power supply including a boost convertor comprising an electronic switch for controlling current through a boost inductance, rectifier means for charging capacitor means which accumulate the resulting boost charge from the boost inductance, means for repeatedly switching the electronic switch, means for measuring the current conducted through said electronic switch and for generating a switch current signal related to the measured current through said electronic switch, pulse width modulation means responsive to said switch current signal for varying the relative on/off period of each cycle of switching to cause the peak switch current to follow a variable amplitude waveform of shape corresponding to the input voltage applied to the boost convertor and amplitude controlled by an error amplifier and multiplier thereby regulating the output voltage, the multiplier including a comparator which switches on/off at a duty cycle determined by the error amplifier, a supplementary inductor operated within its linear region and not biased into saturation by the line current passing through it in series with the boost inductance, an output from the supplementary inductor following the slope of the ripple current caused by the switching of the boost inductance, the output of said supplementary inductor being used both to generate an error correction signal having a value proportional to the sum of the positive and negative slopes of the ripple current plus a bias for stable control at low output levels and to control a ramp signal generator for pulse width stability, means for adding the error correction signal to the variable amplitude waveform to reduce line current distortion, and means for generating a ramp signal and adding it to the switch current signal for pulse width stability.
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Accused Products
Abstract
A boost convertor power supply comprising an electronic switch controlling current through a boost inductance, a rectifier for charging a capacitor which accumulates the resulting boost charge from the boost inductance, and circuitry for repeatedly switching the electronic switch. A pulse width modulation circuit varies the relative on/off period of each cycle of switching to cause the peck switch current to follow a variable amplitude wave of shape corresponding to the input voltage applied to the boost converter and amplitude controlled by an error amplifier and multiplier thereby regulating the output voltage. A ramp signal generator provides for pulse width stability. An error correction circuit corrects for the difference between average current in the boost inductor and peak switch current to modify the pulse width modulation circuit to reduce distortion of the line current waveform.
182 Citations
19 Claims
- 1. A power supply including a boost convertor comprising an electronic switch for controlling current through a boost inductance, rectifier means for charging capacitor means which accumulate the resulting boost charge from the boost inductance, means for repeatedly switching the electronic switch, means for measuring the current conducted through said electronic switch and for generating a switch current signal related to the measured current through said electronic switch, pulse width modulation means responsive to said switch current signal for varying the relative on/off period of each cycle of switching to cause the peak switch current to follow a variable amplitude waveform of shape corresponding to the input voltage applied to the boost convertor and amplitude controlled by an error amplifier and multiplier thereby regulating the output voltage, the multiplier including a comparator which switches on/off at a duty cycle determined by the error amplifier, a supplementary inductor operated within its linear region and not biased into saturation by the line current passing through it in series with the boost inductance, an output from the supplementary inductor following the slope of the ripple current caused by the switching of the boost inductance, the output of said supplementary inductor being used both to generate an error correction signal having a value proportional to the sum of the positive and negative slopes of the ripple current plus a bias for stable control at low output levels and to control a ramp signal generator for pulse width stability, means for adding the error correction signal to the variable amplitude waveform to reduce line current distortion, and means for generating a ramp signal and adding it to the switch current signal for pulse width stability.
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5. An alternating-current to direct-current power convertor having an input port, an output port, and an output voltage reference, said power convertor regulating the voltage at said output port with respect to said output voltage reference, comprising:
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a boost convertor including a boost inductor coupled to said input port for storing electrical energy, an electronic switch for controlling the current through said boost inductor, and a rectifier means for directing electrical energy from said boost inductor to said output port; means for repeatedly switching said electronic switch in cycles, each cycle having an on-period when said electronic switch is conducting current and an off-period when said electronic switch is not conducting current, said means including pulse width modulating means for varying the amount of the on-period and the off-period in each said switch cycle; monitoring means for measuring the current conducted through said electronic switch and for generating a switch current signal related to the measured current through said electronic switch; reference comparison means for generating an error voltage signal related to the difference between the voltage at said output port and said output voltage reference; means for generating a line voltage reference signal, said line voltage reference signal having a waveform shape related to the voltage at said input port and having an amplitude related to the value of said error voltage signal; means for measuring the difference between the peak value of current through said electronic switch and the average value of current through said boost inductor and for generating an error-correction signal related to said difference in peak and average values; and means for summing said error-correction signal and said line voltage reference signal to produce an error-corrected line voltage reference signal, said pulse width modulating means responsive to said error-corrected line voltage reference signal and to said switch current signal, said pulse width modulating means beginning each cycle with an on-period and switching to an off-period when said switch current signal exceeds said error-corrected line voltage reference signal, said pulse width modulating means thereby regulating the voltage at said output port to said output voltage reference and reducing the distortion of the line current waveform at said input port with respect to the line voltage waveform at said input port. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification