Regulated dc-dc converter using a resonating transformer
First Claim
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1. A dc-dc step-up converter for supplying two ranges of high voltage dc to a load comprising:
- a full bridge voltage inverter having a first and second leg, each leg having two series-connected controllable switch means with reverse current carrying ability;
said inverter adapted to be coupled to external dc source;
two series-connected capacitors connected in parallel with said first leg;
circuit means for connecting the junction of said two capacitors to the junction of the two switch means in said first leg and bypassing said switch means in said first leg to obtain a first range of output voltage and disconnecting the junctions and allowing operation of said switch means to obtain the second range of output voltage;
a step-up transformer receiving ac power from said voltage inverter said transformer coupled to the output of said inverter;
rectifying means connected to the output of said transformer for rectifying the output voltage of said transformer and supplying stepped up dc voltage to the load; and
control means coupled to said rectifying means and each of said switch means, and responsive to said load voltage and to a voltage magnitude command for providing a frequency command to said inverter to adjust the input frequency to said transformer and thereby vary the output voltage, the frequencies provided to the transformer being selected to cause the transformer shunt capacitance and leakage reactance to act as a series resonant circuit and resonate at or above the damped resonant frequency of the series resonant circuit to achieve voltage step up due to the resonant rise of voltage across the shunt capacitance of the resonant circuit as well as the transformer turns ratio.
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Abstract
A resonant dc-dc converter employing power transistors as the switching elements generates a high dc output voltage (150 kilovolts) to drive an X-ray tube. The converter is configured such that the resonating circuit elements can be realized using the transformer parasitic elements. Voltage step up is achieved due to the transformer turns ratio as well as the resonant rise of voltage across the energy storage elements of a series resonant circuit.
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6 Claims
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1. A dc-dc step-up converter for supplying two ranges of high voltage dc to a load comprising:
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a full bridge voltage inverter having a first and second leg, each leg having two series-connected controllable switch means with reverse current carrying ability;
said inverter adapted to be coupled to external dc source;two series-connected capacitors connected in parallel with said first leg; circuit means for connecting the junction of said two capacitors to the junction of the two switch means in said first leg and bypassing said switch means in said first leg to obtain a first range of output voltage and disconnecting the junctions and allowing operation of said switch means to obtain the second range of output voltage; a step-up transformer receiving ac power from said voltage inverter said transformer coupled to the output of said inverter; rectifying means connected to the output of said transformer for rectifying the output voltage of said transformer and supplying stepped up dc voltage to the load; and control means coupled to said rectifying means and each of said switch means, and responsive to said load voltage and to a voltage magnitude command for providing a frequency command to said inverter to adjust the input frequency to said transformer and thereby vary the output voltage, the frequencies provided to the transformer being selected to cause the transformer shunt capacitance and leakage reactance to act as a series resonant circuit and resonate at or above the damped resonant frequency of the series resonant circuit to achieve voltage step up due to the resonant rise of voltage across the shunt capacitance of the resonant circuit as well as the transformer turns ratio. - View Dependent Claims (2, 4, 5, 6)
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3. The dc-dc converter of claim 10 wherein said switches with gate turn-off capability comprise transistors each with an inverse parallel connected diode.
Specification