System and method for conversion of high voltage AC to low voltage DC using input voltage gating
First Claim
1. An apparatus for converting high voltage alternating current (AC) power input to a low voltage direct current (DC) power output, comprising:
- a first rectifier to receive a high voltage AC line power input and to output a full wave rectified waveform;
an electronically actuated switch coupled to receive the full wave rectified waveform and provide a voltage-modulated pulse output in response to a gating signal;
an input voltage detector to provide an input voltage signal corresponding to a voltage of the AC power input;
a threshold voltage generator connected to receive the low voltage DC power output and provide a threshold voltage signal that varies in proportion to the low voltage DC power output;
a voltage comparator to compare the input voltage signal to the threshold voltage signal and to provide a control signal when the input voltage signal is below the threshold voltage;
a pulse generator to generate the gating signal at a predetermined frequency in response to the control signal;
a transformer having a primary coil coupled to the switch to receive the voltage-modulated pulse output and a secondary coil coupled with a second rectifier that provides the DC power output; and
a filter capacitor to smooth the DC power output, whereby the apparatus is to provide the low voltage DC power output using the transformer, and the filter capacitor has voltage ratings less than a voltage peak of the AC power input by only gating power though the switch to the transformer and the filter capacitor when the AC power input voltage is below a predetermined value.
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Abstract
A method and apparatus for conversion of high voltage AC to low voltage high current DC without using high voltage capacitors or transformers. A single switch is used to perform both the functions of pre-regulation and switching conversion. An input voltage detector determines when the input power AC is below a predetermined voltage limit. A threshold voltage generator provides a threshold voltage corresponding to the output voltage. A voltage comparator coupled to the input voltage detector and threshold voltage generator enables a pulse generator to activate the switch to gate a number of pulses of the input power below the predetermined voltage limit at predetermined frequency to a transformer. The converter regulates its output voltage by changing the input voltage threshold at which it starts switching, instead of using PWM or other known regulation technique.
43 Citations
20 Claims
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1. An apparatus for converting high voltage alternating current (AC) power input to a low voltage direct current (DC) power output, comprising:
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a first rectifier to receive a high voltage AC line power input and to output a full wave rectified waveform; an electronically actuated switch coupled to receive the full wave rectified waveform and provide a voltage-modulated pulse output in response to a gating signal; an input voltage detector to provide an input voltage signal corresponding to a voltage of the AC power input; a threshold voltage generator connected to receive the low voltage DC power output and provide a threshold voltage signal that varies in proportion to the low voltage DC power output; a voltage comparator to compare the input voltage signal to the threshold voltage signal and to provide a control signal when the input voltage signal is below the threshold voltage; a pulse generator to generate the gating signal at a predetermined frequency in response to the control signal; a transformer having a primary coil coupled to the switch to receive the voltage-modulated pulse output and a secondary coil coupled with a second rectifier that provides the DC power output; and a filter capacitor to smooth the DC power output, whereby the apparatus is to provide the low voltage DC power output using the transformer, and the filter capacitor has voltage ratings less than a voltage peak of the AC power input by only gating power though the switch to the transformer and the filter capacitor when the AC power input voltage is below a predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for operating a circuit for converting high voltage alternating current (AC) power input to a low voltage direct current (DC) power output, comprising:
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receiving a high voltage AC line power input; rectifying the AC line power input to provide a full wave rectified waveform Vrectified; determining a threshold voltage Vthreshold above which the full wave rectified waveform Vrectified is to be isolated from a low voltage rated transformer having a primary coil and a secondary coil; comparing the threshold voltage Vthreshold to a signal corresponding to an instantaneous voltage of the full wave rectified waveform Vrectified; switching the full wave rectified waveform Vrectified to the primary coil of the low voltage rated transformer at a predetermined frequency greater than that of a frequency of the AC power input, while the full wave rectified waveform Vrectified is less than the threshold voltage Vthreshold; and providing power from the secondary coil of the low voltage rated transformer as the low voltage DC power output, whereby the circuit provides the low voltage DC power output using the low voltage rated transformer having voltage ratings less than a voltage peak of the AC power input by only gating power though the switch to the transformer when the AC power input voltage is below a predetermined value. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification