High voltage generator and control methods thereof

A high voltage generator comprising:

• an inverter bridge including a first bridge leg and a second bridge leg, at least one of the first bridge leg or the second bridge leg including at least two switch transistors distributed in series;
• a first resonant branch coupled in series to the first bridge leg;
• a transformer coupled in series between the first resonant branch and the second bridge leg;
• a second resonant branch coupled in parallel with the transformer;
• a rectifier circuit coupled with the transformer for providing an output voltage to an X-ray source;
• and
• a control circuit, the control circuit comprising a first control branch, a second control branch, and a modulator, and both the first control branch and the second control branch being coupled to the modulator,
• wherein the first control branch is operable to obtain an output current and a bridge leg voltage of the inverter bridge, and to produce a first control signal based on the output current and the bridge leg voltage of the inverter bridge,
• wherein the second control branch is operable to receive a voltage feedback signal from the rectifier circuit or the X-ray generating device, and to produce a second control signal based on the voltage feedback signal,
• wherein the first control branch comprises:
• a first zero-crossing comparator, an input of the first zero-crossing comparator being coupled with the output of the first bridge leg;
• a second zero-crossing comparator, an input of the second zero-crossing comparator being coupled with the output of the inverter bridge;
• a phase delay coupled in series to the first zero-crossing comparator;
• a phase comparator, an output of the phase delay and the output of the second zero-crossing comparator being coupled with an input of phase comparator;
• and
• a carrier generator, an input of the carrier generator being coupled with an output of the phase comparator, and an output of the carrier generator being coupled with the input of the modulator.

A method for controlling a high voltage generator, the high voltage generator comprising:

• an inverter bridge, the inverter bridge comprising a first bridge leg and a second bridge leg, the first bridge leg and the second bridge leg being coupled in parallel, and the first bridge leg or the second bridge leg comprising two or more switch transistors distributed in series;
• a first resonant branch, the first resonant branch being coupled with the first bridge leg;
• a transformer comprising a primary side winding and a secondary side winding, the primary side winding and the first resonant branch being coupled in series, and the primary side winding being coupled with the second bridge leg;
• a second resonant branch, the second resonant branch being coupled in parallel to the primary side winding or the secondary side winding of the transformer, wherein
• the second resonant branch includes a capacitor and an inductor,
• a first end of the capacitor is connected to a first end of the inductor,
• a second end of the capacitor is connected to a first end of the transformer, and
• a second end of the inductor is connected to a second end of the transformer;
• a rectifier circuit, the rectifier circuit being coupled with the secondary side winding of the transformer for providing output voltage to an X-ray generating device;
• the method comprising:
• controlling the phase relationship between the bridge leg voltage and the output current of the inverter bridge to control a frequency of a driving signal of the switch transistors of the inverter bridge.

A high voltage generator, comprising:

• an inverter circuit coupled to receive a direct-current (DC) input voltage, wherein the inverter circuit includes a first bridge leg and a second bridge leg, the first bridge leg or the second bridge leg including at least two switch transistors distributed in series;
• a resonant circuit coupled to the inverter circuit, wherein the resonant circuit includes a first resonant branch coupled in series to the first bridge leg and a second resonant branch coupled in parallel with a transformer;
• the transformer coupled in series between the first resonant branch and the second bridge leg, and also coupled to a rectifier circuit, wherein the rectifier circuit is configured to provide a high voltage output to an X-ray source, wherein
• the second resonant branch includes a second capacitor and a second inductor,
• a first end of the second capacitor is connected to a first end of the second inductor,
• a second end of the second capacitor is connected to a first end of the transformer, and
• a second end of the second inductor is connected to a second end of the transformer;
• and
• a phase control circuit coupled to receive a voltage across and a current through the resonant circuit and also coupled to the inverter circuit, wherein the phase control circuit generates control signals to drive the inverter circuit, and wherein the control signals drive the inverter circuit to keep the resonant circuit operating in an inductive region.