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US 5,001,620 AGranted
Power factor improvement
AssigneeAstec International Limited
InventorDavid A. Smith
Life of this patent
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AssigneeAstec International Limited
InventorDavid A. Smith
Estimating the term…
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.
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.
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:
The power convertor of claim 10 wherein said 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 measures said difference during each said switching cycle.
Dependencies are inferred from the claim text.