Phase shift inverter, X-ray high-voltage device using same, X-ray CT device, and X-ray imaging device
View Patent ↗An inverter circuit allowing a single drive circuit to perform both tracking control for tracking resonance frequency fluctuations caused by load fluctuations, and power control, thereby reducing switching loss. An inverter drive circuit part obtains a phase difference between output current and output voltage directed to a load circuit connected to a midpoint of two arm circuits of the inverter circuit, and controls a phase of the driving signal directed to each semiconductor switch such that the phase difference becomes zero or a predetermined value, enabling an operating frequency of the inverter circuit part to track a resonance frequency of the load circuit, and enabling a current phase to be delayed with respect to a voltage phase, thereby achieving ZCS. Since the phase difference is used, an auxiliary circuit is not necessary for measuring a current value in proximity to the semiconductor switches.
1. A phase shift inverter circuit comprising:
an inverter circuit part where two arm circuits are connected in parallel, each arm circuit having two semiconductor switches being serially connected, the switches respectively connected inversely in parallel with diodes; and
an inverter drive circuit part for providing a driving signal to each of the semiconductor switches of the inverter circuit,
wherein the inverter drive circuit part obtains a phase difference between output current and output voltage directed to a load circuit which is connected to a midpoint of the two arm circuits, and controls a phase of the driving signal directed to each of the semiconductor switches in such a manner that the phase difference between the output current and the output voltage becomes zero or a predetermined value, thereby allowing an operating frequency of the inverter circuit part to track a resonance frequency of the load circuit,
wherein the inverter drive circuit part controls the phase of the driving signal of each of the semiconductor switches, in such a manner that the output current has a phase delayed from the output voltage by a predetermined value.
2. The phase shift inverter circuit according to claim 1 , wherein the inverter drive circuit part adjusts a phase difference of the driving signals directed to the semiconductor switches which are determined in advanced to be used in a pair, among four semiconductor switches in the inverter circuit part, thereby enabling a control of an output power of the inverter circuit part.
3. The phase shift inverter circuit according to claim 1 , wherein the inverter drive circuit part comprises a circuit for generating a fundamental wave signal with a certain duty cycle having a pulse width with a center equivalent to the center of a positive-polarity pulse width of the output voltage, and the driving signal is allowed to be generated by use of the fundamental wave signal.
4. The phase shift inverter circuit according to claim 1 , wherein the inverter drive circuit part comprises a circuit for generating a fundamental wave signal with a certain duty cycle, the signal being inversed at a timing when the output voltage is changed from zero voltage to a positive polarity pulse or a negative polarity pulse, and the driving signal is allowed to be generated by use of the fundamental wave signal.
5. The phase shift inverter circuit according to claim 1 , wherein the inverter drive circuit part obtains the phase difference between the output current and the output voltage, by using a phase of the current detected between the midpoint of the two arm circuits and the load circuit as the output current, and by using the phase of the driving signal as the phase of the output voltage.
6. An X-ray high voltage generator comprising:
a phase shift inverter circuit for converting a DC power source output into a high-frequency AC output;
a high voltage transformer for converting the high-frequency AC output of the inverter circuit into a high voltage output;
a rectifier circuit for rectifying the output of the high voltage transformer and supplying DC power to an X-ray tube; and
a control circuit,
wherein the control circuit comprises a filament heating circuit for heating a filament of the X-ray tube, and an anode rotary drive circuit for performing rotary drive of an anode of the X-ray tube, and
wherein the inverter circuit corresponds to the phase shift inverter circuit according to claim 1 .
7. An X-ray CT apparatus comprising:
a disc provided with an aperture for inserting a test subject;
an X-ray tube and an X-ray detector respectively mounted on positions opposed to each other placing the aperture of the disc therebetween;
an X-ray high voltage generator for supplying DC power to the X-ray tube;
a bed for placing the test subject thereon to be inserted into the aperture of the disc; and
a rotary drive part for rotating the disk,
wherein the X-ray high voltage generator corresponds to the X-ray high voltage generator according to claim 6 .
8. An X-ray imaging apparatus comprising:
an X-ray tube;
an X-ray image receiver for detecting X-rays transmitted through a test subject; and
an X-ray high voltage generator for supplying DC power to the X-ray tube,
wherein the X-ray high voltage generator corresponds to the X-ray high voltage generator according to claim 6 .
9. A phase shift inverter circuit comprising:
an inverter circuit part where two arm circuits are connected in parallel, each arm circuit having two semiconductor switches being serially connected, the switches respectively connected inversely in parallel with diodes; and
an inverter drive circuit part for providing a driving signal to each of the semiconductor switches of the inverter circuit,
wherein the inverter drive circuit part obtains an operating frequency of output power directed to a load circuit which is connected to a midpoint of the two arm circuits, and controls a phase of the driving signal directed to each of the semiconductor switches in such a manner that the operating frequency becomes higher than a resonance frequency of the load circuit, by a predetermined value,
wherein the inverter drive circuit part comprises a circuit for generating a fundamental wave signal with a certain duty cycle having a pulse width with a center equivalent to the center of positive-polarity pulse width of an output voltage, and the driving signal is allowed to be generated by use of the fundamental wave signal.
10. The phase shift inverter circuit according to claim 9 , wherein the inverter drive circuit part adjusts a phase difference of the driving signals directed to the semiconductor switches which are determined in advance to be used in a pair, among four semiconductor switches in the inverter circuit part, thereby enabling a control of the output power of the inverter circuit part.
11. An X-ray high voltage generator comprising:
a phase shift inverter circuit for converting a DC power source output into a high-frequency AC output;
a high voltage transformer for converting the high-frequency AC output of the inverter circuit into a high voltage output;
a rectifier circuit for rectifying the output of the high voltage transformer and supplying DC power to an X-ray tube; and
a control circuit,
wherein the control circuit comprises a filament heating circuit for heating a filament of the X-ray tube, and an anode rotary drive circuit for performing rotary drive of an anode of the X-ray tube, and
wherein the inverter circuit corresponds to the phase shift inverter circuit according to claim 9 .
12. An X-ray CT apparatus comprising:
a disc provided with an aperture for inserting a test subject;
an X-ray tube and an X-ray detector respectively mounted on positions opposed to each other placing the aperture of the disc therebetween;
an X-ray high voltage generator for supplying DC power to the X-ray tube;
a bed for placing the test subject thereon to be inserted into the aperture of the disc; and
a rotary drive part for rotating the disc,
wherein the X-ray high voltage generator corresponds to the X-ray high voltage generator according to claim 11 .
13. An X-ray imaging apparatus comprising:
an X-ray tube;
an X-ray image receiver for detecting X-rays transmitted through a test subject; and
an X-ray high voltage generator for supplying DC power to the X-ray tube,
wherein the X-ray high voltage generator corresponds to the X-ray high voltage generator according to claim 11 .
14. A phase shift inverter circuit comprising:
an inverter circuit part where two arm circuits are connected in parallel, each arm circuit having two semiconductor switches being serially connected, the switches respectively connected inversely in parallel with diodes; and
an inverter drive circuit part for providing signal to each of the semiconductor switches of the inverter circuit,
wherein the inverter drive circuit part obtains an operating frequency of output power directed to a load circuit which is connected to a midpoint of the two arm circuits, and controls a phase of the driving signal directed to each of the semiconductor switches in such a manner that the operating frequency becomes higher than a resonance frequency of the load circuit, by a predetermined value, and
wherein the inverter drive circuit part comprises a circuit for generating a fundamental wave signal with a certain duty cycle, the signal being inversed at a timing when an output voltage is changed from zero voltage to a positive polarity pulse or a negative polarity pulse, and the driving signal is allowed to be generated by use of the fundamental wave signal.
15. The phase shift inverter circuit according to claim 14 , wherein the inverter drive circuit part adjusts a phase difference of the driving signals directed to the semiconductor switches which are determined in advance to be used in a pair, among four semiconductor switches in the inverter circuit part, thereby enabling a control of the output power of the inverter circuit part.
16. An X-ray high voltage generator comprising:
a phase shift inverter circuit for converting a DC power source output into a high-frequency AC output;
a high voltage transformer for converting the high-frequency AC output of the inverter circuit into a high voltage output;
a rectifier circuit for rectifying the output of the high voltage transformer and supplying DC power to an X-ray tube; and
a control circuit,
wherein the control circuit comprises a filament heating circuit for heating a filament of the X-ray tube, and an anode rotary drive circuit for performing rotary drive of an anode of the X-ray tube,
wherein the inverter circuit corresponds to the phase shift inverter circuit according to claim 14 .
17. An X-ray CT apparatus comprising:
a disc provided with an aperture for inserting a test subject;
an X-ray tube and an X-ray detector respectively mounted on positions opposed to each other placing the aperture of the disc therebetween;
an X-ray high voltage generator for supplying DC power to the X-ray tube;
a bed for placing the test subject thereon to be inserted into the aperture of the disc; and
a rotary drive part for rotating the disc, wherein the X-ray high voltage generator corresponds to the X-ray high voltage generator according to claim 16 .
18. An X-ray imaging apparatus comprising:
an X-ray tube;
an X-ray image receiver for detecting X-rays transmitted through a test subject; and
an X-ray high voltage generator for supplying DC power to the X-ray tube,
wherein the X-ray high voltage generator corresponds to the X-ray high voltage generator according to claim 16 .