High frequency x-ray generator power supply

Claim 2

A dc-ac converter comprising: circuit means for providing an ac output voltage at a commanded frequency from a dc input voltage; a transformer coupled to said circuit means for receiving ac power from said circuit means; and control means responsive to a voltage magnitude command for providing a frequency command to said circuit means to adjust the input frequency to said transformer and thereby vary the output voltage, the frequencies provided to the transformer being selected to cause said transformer shunt capacitance and leakage reactance to act as a series resonant circuit and resonate about their resonant frequency to achieve voltage transformation due to the transformer turns ratio as well as the resonant change in voltage across the shunt capacitance of the transformer.

Claim 3

The dc-ac converter of claim 1 wherein said circuit means comprises an inverter having switches with gate turn-off capability.

Claim 4

A dc-dc step-up converter for supplying high voltage dc to a load comprising: a dc-ac voltage inverter for providing an ac output voltage at a commanded frequency from a dc input voltage; a step-up transformer adapted to receive ac power from said voltage inverter; rectifier means for rectifying said transformer output voltage coupling the output of said transformer to said load; and control means responsive 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 circuits 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.

Claim 5

A dc-dc step-up converter for supplying high voltage dc to a load comprising: a dc-ac voltage inverter for providing an ac output voltage at a commanded frequency from a dc input voltage; a step-up transformer adapted to receive ac power from said voltage inverter; rectifier means for rectifying said transformer output voltage coupling the output of said transformer to said load; and control means responsive 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 circuits 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.

Claim 6

The dc-dc converter of claim 3 wherein said inverter comprises switches with gate turn-off capability.

Claim 7

The dc-dc converter of claim 4 wherein said switches with gate turn-off capability comprise transistors each with an inverse parallel connected diode.

Claim 8

The dc-dc converter of claim 4 wherein said transformer comprises a primary winding magnetically coupled to two secondary windings.

Claim 9

The dc-dc converter of claim 6 wherein said rectifier means comprises two rectifier means, one rectifier means being connected to each of said secondary windings, the output of said rectifier means connected in series and the junction of said rectifiers being grounded.

Claim 10

The dc-dc converter of claim 4 wherein said control means comprises means for providing a signal proportional to the output voltage of the converters, means for comparing the commanded output voltage to the signal proportional to the output voltage to develop an error signal, limit circuit means receiving said error signal, a voltage control oscillator responsive to the output signal of said limit circuit means and base driver means responsive to the output frequency of said voltage control oscillator for providing switching signals to said inverter switches.

Claim 11

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.

Claim 12

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.

Claim 13

The dc-dc converter of claim 9 wherein said inverter comprises switches with gate turn-off capability.

Claim 14

The dc-dc converter of claim 10 wherein said switches with gate turn-off capability comprise transistors each with an inverse parallel connected diode.

Claim 15

The dc-dc converter of claim 10 wherein said transformer comprises a primary winding magnetically coupled to two secondary winding.

Claim 16

The dc-dc converter of claim 12 wherein said rectifier means comprises two rectifier means, one rectifier means being connected to each of said secondary windings, the output of said rectifier means connected in series and the junction of said rectifiers being grounded.

Claim 17

The dc-dc converter of claim 10 wherein said control means comprises means for providing a signal proportional to the output voltage of the converter, means for comparing the commanded output voltage to the signal proportional to the output voltage to develop an error signal, limit circuit means receiving said error signal, a voltage controlled oscillator responsive to the output signal of said limit circuit means and base driver means responsive to the output frequency of said voltage control oscillator for providing switching signals to said inverter switches.