Heating circuit for a filament of an X-ray tube

Claim 2

A heating circuit (100) for a filament of an X-ray tube characterized by comprising: transformer means (T1) having at least a primary winding (L1) coupled to a DC source (10) and a secondary winding (L2) coupled to the filament (52) of the X-ray tube (50); switching means (SW1), connected between the primary winding (L1) of the transformer means (Tl) and the DC source (10), having at least a capacitor (C1) and a diode (D1) functioning as a damper diode, connected parallel to the capacitor (C1) and the switching means (SW1), the switching means (SW1) constituting a voltage resonance type switch (20) in conjunction with at least the capacitor (C1) and the primary winding (L1), whereby a DC voltage of the DC source (10) is interrupted and thus an AC voltage having an arc waveform is induced at the secondary winding (L2); detection means (30), coupled to the filament (52) of the X-ray tube (50) for detecting a filament current to produce a switching control signal; and means (40) for driving the switching means (SW1) by controlling at least one of a switching period and a conducting period thereof with remaining a resonant condition of the voltage resonance type switch (20) so as to vary the filament current.

Claim 3

A circuit (100) as claimed in claim 1, characterized by further comprising a diode rectifier bridge circuit (60) connected between the secondary winding (L2) and the filament (52) so as to rectify the AC voltage induced at the secondary winding (L2).

Claim 4

A circuit (100) as claimed in claim 1, characterized in that the detection means includes a current sensor (32) coupled to the filament (52) and a filament current detector/controller (30), the current sensor (32) being constructed by a current transformer.

Claim 5

A circuit (100) as claimed in claim 1, characterized in that the detection means includes a current sensor (32) coupled to the filament (52) and a filament current detector/controller (30), the current sensor (32) being constructed by a Hall-effect element.

Claim 6

A circuit (100) as claimed in claim 1, characterized in that the voltage resonance type switch (20) is a transistor.

Claim 7

A circuit (100) as claimed in claim 1, characterized in that the voltage resonance type switch (20) is a thyristor.

Claim 8

A heating circuit (200) for a filament of an X-ray tube characterized by comprising: transformer means (Tl) having at least a primary winding (Ll) coupled to a DC source (10) and a secondary winding (L2) coupled to the filament (52) of the X-ray tube (50); first switching means (SW1), connected between the primary winding (L1) of the transformer means (Tl) and the DC source (10), having at least a capacitor (Cl) and a first diode (Dl) functioning as a damper diode, connected parallel to the capacitor (Cl) and the first switching means (SW1), the first switching means (SW1) constituting a voltage resonance type switch (20) in conjunction with at least the capacitor (Cl) and the primary winding (L1), whereby a DC voltage of the DC source (10) is interrupted and thus an AC voltage having an arc waveform is induced at the secondary winding (L2); second switching means (SW2), series-connected to the first switching means (SW1), having a second diode (D2) connected parallel to the second switching means (SW1); first driving means (40) having an oscillator that produces a first switching control signal, for driving the first switching means (SW1) based upon the first switching control signal by controlling at least one of a switching period and a conducting period of the first switching means (SWl) with remaining a resonant condition of the voltage resonance type . switch (20); detection means (30), coupled to the filament (52) of the X-ray tube (50), for detecting a filament current to produce a second switching control signal; and second driving means (80) for driving the second switching means (SW2) based upon the first and second switching control signals so as to vary the filament current.

Claim 9

A heating circuit (200) for a filament of an X-ray tube characterized by comprising: transformer means (Tl) having at least a primary winding (Ll) coupled to a DC source (10) and a secondary winding (L2) coupled to the filament (52) of the X-ray tube (50); first switching means (SW1), connected between the primary winding (L1) of the transformer means (Tl) and the DC source (10), having at least a capacitor (Cl) and a first diode (Dl) functioning as a damper diode, connected parallel to the capacitor (Cl) and the first switching means (SW1), the first switching means (SW1) constituting a voltage resonance type switch (20) in conjunction with at least the capacitor (Cl) and the primary winding (L1), whereby a DC voltage of the DC source (10) is interrupted and thus an AC voltage having an arc waveform is induced at the secondary winding (L2); second switching means (SW2), series-connected to the first switching means (SW1), having a second diode (D2) connected parallel to the second switching means (SW1); first driving means (40) having an oscillator that produces a first switching control signal, for driving the first switching means (SW1) based upon the first switching control signal by controlling at least one of a switching period and a conducting period of the first switching means (SWl) with remaining a resonant condition of the voltage resonance type . switch (20); detection means (30), coupled to the filament (52) of the X-ray tube (50), for detecting a filament current to produce a second switching control signal; and second driving means (80) for driving the second switching means (SW2) based upon the first and second switching control signals so as to vary the filament current.

Claim 10

A circuit (200) as claimed in claim 7, characterized by further comprising a diode rectifier bridge circuit (60) connected between the secondary winding (L2) and the filament (52) so as to rectify the AC voltage induced at the secondary winding (L2).

Claim 11

A circuit (200) as claimed in claim 7, characterized by further comprising a filtering capacitor (C2) and a diode rectifier bridge circuit (70) connected between the filament current detection means (30) and the second driving means (80) so as to remove RF ripple components contained in the second switching control signal.

Claim 12

A circuit (200) as claimed in claim 7, characterized in that the detection means includes a current sensor (32) coupled to the filament (52) and a filament current detector/controller (30), the current sensor (32) being constructed by a current transformer.

Claim 13

A circuit (200) as claimed in claim 7, characterized in that the detection means includes a current sensor (32) coupled to the filament (52) and a filament current detector/controller (30), the current sensor (32) being constructed by a Hall-effect element.

Claim 14

A circuit (200) as claimed in claim 7, characterized in that the voltage resonance type switch (20) is a transistor.

Claim 15

A circuit (200) as claimed in claim 7, characterized in that the voltage resonance type switch (20) is a thyristor.