X-ray generating apparatus

• US 4,700,372 A
• Filed: 10/11/1985
• Issued: 10/13/1987
• Est. Priority Date: 10/18/1984
• Status: Expired due to Fees

• Current Assignee: Toshiba Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Tsuchiya, Akira
• Primary Examiner(s): Fields, Carolyn E.
• Assistant Examiner(s): Grigsby, T. N.
• Application Number:
  US06/786,610
• Time in Patent Office: 732 Days
• Field of Search: 378/101, 378/105, 378/102, 363/138
• US Class Current: 378/105
• CPC Class Codes: H05G 1/20 with high-frequency ac; with pulse trains pulse generators in general H03K3/00, H03K4/00
• CPC Class Codes: H05G 1/32 Supply voltage of the X-ray apparatus or tube

Abstract

An X-ray generating apparatus is adapted to obtain an X-ray tube voltage by rectifying an incoming AC voltage to obtain a DC voltage, supplying the DC voltage, after being switched through a switching section, in a predetermined cycle to a resonance circuit comprised of a primary winding of a transformer and resonance capacitors and rectifying the AC voltage which is induced in the secondary winding of the transformer. The switching section comprises a three-phase bridge inverter circuit including parallel arrays of arms each of which is made up of a pair of switching elements. The switching section is so controlled that the switching elements in each respective arm are fired without being continuously turned ON. Each resonance capacitor is connected between an intermediate connection point of the respective arm of the switching section and the primary winding of the transformer.

Claims

1. An X-ray generating apparatus comprising:

first rectifying means, having positive and negative output terminals and a return terminal, for rectifying an input AC voltage to generate a first DC voltage between said output terminals;

a transformer having a primary winding and a secondary winding;

second rectifying means, coupled across said secondary winding, for rectifying a first AC voltage induced in said secondary winding to generate a second DC voltage;

an X-ray tube connected to receive said second DC voltage from said second rectifying means;

first, second and third capacitors;

a bridge inverter circuit having first, second and third phase arms with each arm comprising a pair of switching elements connected in series between said positive and negative output terminals of said first rectifying means in a manner to permit selective conduction of current from said terminals to a common node between said elements, said first, second and third capacitors each coupled between a respective one of said common nodes and one end of said primary winding of said transformer to form respective first, second and third resonance circuits each comprising one of said capacitors and said primary winding;

by-pass means, connected in parallel with each said switching element for conducting resonance current from a respective one of said resonance circuits, past said each said switching element in a direction opposite the flow of current through that switching element;

means for coupling said return terminal of said first rectifying means to the other end of said primary winding; and

control circuit means, connected to each of said switching elements, for sequentially turning on said switching elements (i) in an order to permit altcrnate half cycle positive and negative current flow through said primary winding with each consecutive half cycle of current flow involving a different one of said arms and (ii) at a repetition rate which prevents ever simultaneously turning on both switching elements in any one arm.

2. An X-ray generating apparatus according to claim 1 in which said by-pass means each comprise a diode connected in an inverse parallel fashion to a corresponding switching element.

3. An X-ray generating apparatus according to claim 1 in which said switching elements each comprise a thyristor.

4. An X-ray generating apparatus according to claim 1 in which said switching elements each comprise a gate turn-off thyristor.

5. An X-ray generating apparatus according to claim 1 in which said switching elements each comprise a transistor.

6. An X-ray generating apparatus comprising:

first rectifying means, having positive and negative output terminals, for rectifying an input AC voltage to generate a first DC voltage between said output terminals;

a transformer having a primary winding and a secondary winding;

second rectifying means, coupled across said secondary winding, for rectifying a first AC voltage induced in said secondary winding to generate a second DC voltage;

an X-ray tube connected to receive said second DC voltage from said second rectifying means;

first, second, third, fourth, fifth and sixth capacitors;

first and second half bridge inverter circuits each having first, second and third phase arms with each arm comprising a pair of switching elements connected in series between said positive and negative output terminals of said first rectifying means in a manner to permit selective conduction of current from said terminals to a common node between said elements, said first, second and third capacitors each coupled between a respective one of said common nodes of said first half bridge inverter circuit and one end of said primary winding of said transformer to form respective first, second and third resonance circuits each comprising one of said first, second and third capacitors and said primary winding, and said fourth, fifth and sixth capacitors each coupled between a respective one of said common nodes of said second half bridge inverter circuit and the other end of said primary winding of said transformer to form respective fourth, fifth and sixth resonance circuits each comprising one of said fourth, fifth and sixth capacitors and said primary winding;

by-pass means, connected in parallel with each said switching element, for conducting resonance current from a respective one of said resonance circuits past each said switching element in a direction opposite the flow of current through that switching element; and

control circuit means, connected to each of said switching elements, for sequentially turning on said switching elements (i) in an order to permit alternate half cycle positive and negative current flow through said primary winding with each consecutive half cycle of current flow involving a different one of said arms in said first half bridge inverter circuit and a different one of said arms in said second half bridge inverter circuit and (ii) at a repetition rate which prevents ever simultaneously turning on both switching elements in any one arm of said first half bridge inverter circuit or in any one arm of said second bridge inverter circuit.