Patent US3567940A successfully refreshed from Google Patents.
US3567940A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cineradiographic x-ray tube grid pulsing circuit employing series connected high voltage switching transistors
Assignee: General Electric Co
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Filing: 1969-02-24
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Granted: 1971-03-02
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Expires: 1989-02-24
Abstract
Abstract A light-emitting diode is pulsed at a preselected rate. Emitted light is conducted through a glass image conduit to a phototransistor which operates a solid state control switch at the same rate. The solid state switch controls conduction of a series connected string of transistors whose collectors swing from essentially zero voltage when the transistors are conducting to a high voltage when they are not conducting. The circuit features means for turning all of the transistors off in such manner that no transistor is subjected to overvoltage. The voltage pulses developed on the collector of the last transistor in the series may, for example, be applied to the grid of an xray tube to control its conduction intervals during high rate cinefluorography with an x-ray image converter. A signal that depends on image brightness is used to modulate the width of the pulses and, hence, the output of the x-ray tube so that each film frame has uniform exposure.
Inventors
- 👤 Thomas W Lambert
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:10
CPC Classifications
H; H05; H05G; H05G1/00; H05G1/08; H05G1/60; H03; H03K; H03K17/00; H03K17/10; H03K17/51; H03K17/56; H03K17/60; H03K17/615
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
450 words
A transistor switching system for controlling the bias voltage between the grid and cathode of an x-ray tube comprising: a. terminals that are adapted to be connected to a DC source; b. a resistor voltage divider connected across said source terminals; c. a load resistor means having one end connected to the positive source terminal; d. a plurality of series connected transistor stages each of which has a base, an emitter and a collector, the collector of one being connected to the other end of the load resistor and the emitter of the one being connected to the series connected collector-emitter paths of the others; e. a control switch connected between the last emitter in the series and the negative source terminal; f. base resistors connected between successive intermediate points on the resistor divider and the respective transistor bases whereby to supply forward-bias current through the baseemitter junctions of the transistors when said control switch is conducting to turn the series connected transistors on and thereby make the potential of the other end of the load resistor substantially equal to that of the negative source termiNal; g. a voltage divider comprising series connected capacitors that are connected across said source terminals; h. a first diode connected between each transistor base and a corresponding intermediate point on the capacitor voltage divider, said diodes being biased oppositely at the baseemitter junctions; i. a second diode connected in parallel with each base-emitter junction and biased in the direction of the first diode and being in series with it to provide a conductive path between each emitter and its associated capacitor; j. the turning off of said control switch causing successive increased potentials on the transistor-emitters, beginning with the stage next to the control switch, which causes collectoremitter current from the stage to divert through the second and first diodes into the said capacitor whereby to reverse bias the base-emitter junctions of the series connected transistors in succession during turn off; k. a discharge resistor in parallel with each capacitor; l. a collector leakage current resistor shunting the emitter and collector of path of each transistor, said leakage current resistors being series connected to each other and connected between said source terminals; m. turnoff of said series transistor stages causing the voltage to rise positively on said other end of the load resistor with respect to said second source terminal; n. an x-ray tube having an anode, a cathode and a control grid; and o. the cathode of said x-ray tube being connected to the other end of said load resistor means and said grid being connected to the cathode when said transistor switches are not conducting to thereby turn off the x-ray tube.
Claim 2
Dependent Claim
450 words
A transistor switching system for controlling the bias voltage between the grid and cathode of an x-ray tube comprising: a. terminals that are adapted to be connected to a DC source; b. a resistor voltage divider connected across said source terminals; c. a load resistor means having one end connected to the positive source terminal; d. a plurality of series connected transistor stages each of which has a base, an emitter and a collector, the collector of one being connected to the other end of the load resistor and the emitter of the one being connected to the series connected collector-emitter paths of the others; e. a control switch connected between the last emitter in the series and the negative source terminal; f. base resistors connected between successive intermediate points on the resistor divider and the respective transistor bases whereby to supply forward-bias current through the baseemitter junctions of the transistors when said control switch is conducting to turn the series connected transistors on and thereby make the potential of the other end of the load resistor substantially equal to that of the negative source termiNal; g. a voltage divider comprising series connected capacitors that are connected across said source terminals; h. a first diode connected between each transistor base and a corresponding intermediate point on the capacitor voltage divider, said diodes being biased oppositely at the baseemitter junctions; i. a second diode connected in parallel with each base-emitter junction and biased in the direction of the first diode and being in series with it to provide a conductive path between each emitter and its associated capacitor; j. the turning off of said control switch causing successive increased potentials on the transistor-emitters, beginning with the stage next to the control switch, which causes collectoremitter current from the stage to divert through the second and first diodes into the said capacitor whereby to reverse bias the base-emitter junctions of the series connected transistors in succession during turn off; k. a discharge resistor in parallel with each capacitor; l. a collector leakage current resistor shunting the emitter and collector of path of each transistor, said leakage current resistors being series connected to each other and connected between said source terminals; m. turnoff of said series transistor stages causing the voltage to rise positively on said other end of the load resistor with respect to said second source terminal; n. an x-ray tube having an anode, a cathode and a control grid; and o. the cathode of said x-ray tube being connected to the other end of said load resistor means and said grid being connected to the cathode when said transistor switches are not conducting to thereby turn off the x-ray tube.
Claim 3
Dependent Claim
67 words
The invention set forth in claim 1 including: a. a phototransistor controlling conduction of said control switch; b. a light source that is operated synchronously with the desired operating intervals of the x-ray tube, said light source being optically coupled with said phototransistor; and c. an electric signal source adapted to energize said light source for timed intervals to thereby turn said control switch on and off.
Claim 4
Dependent Claim
26 words
The invention set forth in claim 2 wherein: a. said light source is a light-emitting diode and a light conduit couples the same to said phototransistor.
Claim 5
Dependent Claim
101 words
The invention set forth in claim 2 including: a. an x-ray image converter having an output phosphor on which there is an optical image when the x-ray tube is energized; b. a camera optically coupled with said phosphor; c. a camera control adapted to operate the camera at a selected recording rate; and d. the said electric signal source being adapted to produce an output signal synchronously with operation of the camera to thereby turn said control switch on and off as aforesaid and to thereby control both conduction of said transistor means and the bias on said x-ray tube grid.
Claim 6
Dependent Claim
97 words
The invention set forth in claim 4 including: a. detector means adapted to produce a signal proportional to the brightness of the image on the phosphor; b. means that respond to the signal from said detector by producing a second signal that represents a percentage deviation from reference brightness; and c. said electric signal source comprising a pulse generator that is pulse rate modulated in response to the frame rate of the camera and is continually pulse width modulated in response to said second signal, whereby the exposure of the consecutive film frames is held substantially uniform.
Claim 7
Dependent Claim
106 words
The invention set forth in claim 1 including: a. an x-ray fluorescent screen; b. a camera optically coupled with the screen; c. a photodetector optically coupled with the screen and producing a first electric signal depending on brightness of the screen; d. means integrating said first electric signal with respect to time and producing an output signal that is related to brightness; e. an electric signal source whose output signal is conTrolled by said integrated signal; f. a light-emitting diode energized by the output signals from said electric signal source; and g. a phototransistor optically coupled with said light-emitting diode said phototransistor controlling said control switch.
Claim 8
Dependent Claim
45 words
The invention set forth in claim 1 including: a. a phototransistor controlling said control switch; b. an electrically energized light-emitting device optically coupled with the phototransistor; and c. an electric signal source for selectively energizing and deenergizing said light-emitting device to define x-ray exposure intervals.
Claim 9
Dependent Claim
89 words
The invention set forth in claim 7 including: a. a cinerecording camera that is operable at a preselected frame rate for recording an optical version of an x-ray image; b. the said electric signal source being a pulse generator that is adapted to have its pulse rate modulated in accordance with the frame rate of the camera and the width of its output pulses modulated in accordance with the brightness of said optical image; and c. the x-ray tube being turned on and off in synchronism with the camera.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-01 | 1974-08-31 | 1975-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-01 | 1978-08-31 | 1979-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-01 | 1982-08-31 | 1983-03-02 | $7700.00 | Window Closed / Lapsed |