US2572258A - X-ray tube safety device - Google Patents

X-ray tube safety device Download PDF

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Publication number
US2572258A
US2572258A US685095A US68509546A US2572258A US 2572258 A US2572258 A US 2572258A US 685095 A US685095 A US 685095A US 68509546 A US68509546 A US 68509546A US 2572258 A US2572258 A US 2572258A
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transformer
circuit
tube
ray tube
secondary
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US685095A
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Edwin R Goldfield
Ball Jack
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Philips Medical Systems Cleveland Inc
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Philips Medical Systems Cleveland Inc
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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05GX-RAY TECHNIQUE
    • H05G1/00X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08Electrical details
    • H05G1/26Measuring, controlling, protecting
    • H05G1/30Controlling
    • H05G1/46Combined control of different quantities, e.g. exposure time as well as voltage or current

Description

Oct. 23, 1951 E. R. GOLDFIELD ETAL 2,572,258

X-RAY TUBE SAFETY DEVICE Filed July 20, 1946 2 SI-lEETS-SI-IEET 1 L E Y INVENTORS EDWIN R. GOLDFELD & JACK BALL BY WW 46% ATTORNEYS Oc 3, 1 51 E. R. GOLDFIELD ET AL 7 X-RAY TUBE SAFETY DEVICE Filed July 20, 1946 2 SHEETS-'-SHEET 2 LI l 9 u L r- E 22a 22b ""7 I 22 I2 INVENTORS EDWIN R. GOLDFIELD & JACK BALL BY i M ATTORN EYS Patented Oct. 23, 1951 UNITED STATES PATETN T OF FREE 7 572,258 XLRAY SAFETY DEVICE Edwin E. Golflfield, University neigm ana Jack Ball;- Cleveland"; Ohio, assignorsto Picker X-Ray Cor 'l'ora't'ion.Waite ManufacturingDiv'ision,-. Inc., Cleveland, Ohio, a corporation of Ohio spit-saith July 20, 1946, Serial No. 685,095

This invention relates to improvements in con trol; circuits for X-ray tubes and more particularly to improvements insafety devices -for preventing injury to X-raytubes by overloading thesame. I object of the present invention is" to provide; means for preventing arr-overly long exposure combined-with an excessive kilovoltage applied tothe tube'. w

Another object of the present invention is prevent an excessive combination of time of exposure plus the milliamperage load on the tube:

Still another object of the invention is to prevent any excessive combination of time; kilovoltage or milliamperage so as to overload the tube to-the point of injury.

Another object of the present invention is to provide control means preventing overloading of the X-ray tube by an excessive combination of kilovoltage together with a second control factor which includes theproduct ofthe milliamperage load on the; X-ray tube=times the numberof-seconds'the tube-is energized.

Qther objects and. advantages of the present invention will be-apparent from the accompanyingdrawings and description and the essential features -tl'iereof'wil1 be set forth in the appended- -claiinsw Ii-r the drawings, g

lis an electrical wiring diagram illustrating one formoiour device; -Fig;'--2--is--a wiring diagram showing a modified form of. our device.

AnX-raytube will take a definite maximum leading which-is a function-oi the milliamperage, the .kilovol-tage and the time for a definite load limit. If any one of the above is increased, then it'z-is necessary to decrease at least one of the othentwo: factors;

J In Fignl we have shown an autoi transformer ilflfisupplied with electrical energy from the cir cuitlLl, L2. Suitable taps connect leads II and 12 with the primary Isa of a high tension transfiormer- 13. ,The secondary [3b of this transformer,: is connected by leads I4 and 5- with the ;X-raytube 16 in the usual manner. The midportion of the secondary circuit of the transformer is-groundedat I! in the usual manner.

An exposure. is initiated in the customary mannerby closing-push button l8 which completes a circuit from L-lthrough linesl9 and 26 through the push button and. line 21 torelay 22 and then through lines 23 andfill rto the mid-point of the auto-transformer. This energizes relay i Claims. (01. 250-95) 2t 22 attracting the armature 22a; so that current flows through line l2 and normally closed arma ture 25b of relay 25th the primary [3b of the high tension transformer. The timing of the exposure is controlled by the space discharge tube 26 which is of the gasfilled triode type having a cold cathode 2611? a plate 261) and acontrol grid 26c. I-hepower supplyfor this tubeis providedfrom the circuit L3, L4 to the primary 21 eftran'sformer 2]; The secondary oif th'i s ransformer 21b provided with a ieotifier" tube 28- SO that rectified ul'reiit is supplied to the leads '29 anqi: 30'. The siresof the control grid Zfi df the timer-tubeincliides resistance 3|, condenser 3 2, and a time-selector switch 33 having a series" of v limiting resistors 33a; 33b, 33c and 33dl The connecting lines 34 and 36 are tapped intovariable resistance" 31 so as to apply the desired voltage on grid zse. Means is provided for shdrt-circuitiiig condenser 32 upto the mement that an exposureis'initiated. This comprises lines 38, 39 normally closed arrn'ature 22b of relay 22; andlines 46, 29- and. When relay 22 is energized to start an exposure, armature 22b opens this short circuit of the con;- denser. Then; the condenser begins to charge; the rate depending; among other things, upon the position of, the time selector s witch'; 3". As. soon as thevolt'age oi", condenser-{32 re c es a critical value there is abrea'kdown between the control grid :60 and the cathodeltm thus firing the tube 26. This immediately carries over to the circuit ofplate' 26-2) and acts througlithe plate circuit, presently described; to; energize relay 25 which opens the normally closedarrn'a ture zlihstopping tl'ie exposure I 7 It, is .a wellykhblwn,characteristic,of the type Qf tube shown at 26 thateth firingof such" a isdependent notpnly upon.the, vo1'tage or gnu 2%,,bu1i on the.-,. V01fage bLplat'e fibuals'o. In other words; there ,is 'anlintererelationship between the. voltage of. the .Igrid andhplate either ofwhichwill c,a us.e.,tlie, tube .to me. Wev make use of this characteristic of thetubetointrofdu'ce factors responsive to variations in the Kilovoltage andmillia npere load applied. to X-ray tube H5 in order to 'cohtrolth'evfiiiilig Qfl fllbe 26}. It, is Obviousl. that .our invention might be 'appl'iedto modify ,theiiring of tube 26 either. uuon. ,varia' tions oi "kflovoltage. alone or of ,m'ill'iamperage alone, but welpreferto a-pply corrections for both of these factors'at the samet'iine.

. In .thecircuit of. plate 26,11 are; linen 6133? 25-, line 43, secondary flar qf transfonner 14, line 45 and secondaryvllid oi transformer '46.

The transformer 44 provides a corrective factor responsive to variations in the kilovoltage applied to the X-ray tube. To this end, the primary 44b of the transformer 44 is connected across lines I] and 12 with the variable resistor 41 to set the desired current for the transformer primary 44b. Thus, as the kilovoltage controlled through lines ll and I2 varies up or down the current in the transformer secondary 44a will vary up or down in like manner, so as to provide a corrective factor in the circuit of plate 261). If the kilovoltage increases beyond a predetermined point, then the voltage on plate 2619 will increase and will fire tube 26 so as to terminate the exposure.

The corrective factor for milliamperage of X-ray tube 16 is applied in the plate circuit of tube 26 by means of the secondary 46a of transformer 46 as previously mentioned. The primary 46b of this transformer is in circuit with the filament transformer for the X-ray tube. This circuit includes lines 48 and 49, primary 50a of the filament transformer 50, line primary 48b of transformer 46 and line l9. Since the load on the X-ray tube is roughly proportional to the current supplied to the primary 50a of the filament transformer, the transformer 46 will be responsive to variations in the load on the X-ray tube, and through its secondary 46a will supply a corrective factor in the circuit controlling plate 26b. Thus, as the load on the X-ray tube increases, the voltage on plate 251) will increase and upon reaching a predetermined level will fire tube 26 and terminate the exposure.

To limit the filament current corresponding to the time selected at switch 33, a gang switch 52 is provided which is operated in unison with switch 33, such connection being indicated by the broken line 53. A shunt resistor 54 is provided across the transformer primary 461), the various taps of which are connected to similar taps 52a, 52b, 52c; 52d and 52a of the gang switch 52. Thus, corresponding to a definite time setting picked off by switch 33, a filament current limiting resistor is picked off by switch 52 which governs the amount of voltage to be introduced into the plate circuit of the timer tube 26.

-The transformers 44 and 46 are so constructed and adjustable resistances so selected, that the voltages introduced by them into the circuit of plate 26?) cause the tube 26 to fire whenever excessive kilovoltage or milliamperage, or a combination of both, is introduced into the X-ray tube control circuits, always in correspondence to the time of tube exposure.

It should be noted that the compensating voltages in the control circuit for tube 26 are always on, even though an exposure is not initiated. Therefore, tube 26 may fire and open relay at the armature 25b thereof before push button I8 is closed, in an attempt to start the exposure. This means that should the factors for the exposure be chosen so as to impose too great a load upon the X-ray tube, then it would be impossible to start an exposure.

Preferably, we provide an indicating device 55, such as a lamp or the like, to show that relay 25 is open and that the exposure chosen would impose too great a load upon the X-ray tube. To this end, lamp 55 is in circuit with lines 24, 48, 56, 51 and [5 when relay armature 25a is attracted by the energization of relay 25.

Fig. 2 shows a modification of Fig. 1 wherein similar parts having similar functions have been given the same reference characters and only the differences will be explained here. The purpose of Fig. 2 is to provide a correction factor which more directly is responsive to the milliamperage applied to the X-ray tube l6. For this purpose, the correction factor for the load on the X-ray tube is supplied through transformer 58, whose secondary 58a occupies the same place in the eontrol circuit of plate 26?) as that occupied by the transformer secondary 46a previously described. The primary 58b of this transformer is connected by lines 59 and 60 in the central secondary circuit of high tension transformer 13. Here, as in the previously described modification, the shunt resistor 54 is connected to suitable taps on gang switch 52 so that a definite load factor permissible on the X-ray tube is selected with each movement of the timer switch 33. In this modification, the filament transformer 6| has a primary Bla connected with the source L5, L6, in any suitable manner, as the filament transformer is not directly concerned in the safety control circuit in this modification of our device.

All of the other factors of Fig. 2 correspond to those described in Fig. 1 and any change in kilovoltage or load applied to the X-ray tube provides a corresponding variation in the firing of tube 26 which opens the relay 25b of relay 25 to terminate the exposure. The armature 25a and the indicating lamp 55 have been omitted from Fig. 2, but obviously, they may be used as shown in Fig. 1, if desired.

In Figs. 1 and 2, we have shown the autotransformer [8 with energizing circuit Ll, L2, and a self-rectified unit. However, those skilled in this art will recognize that in most cases the type of X-ray unit used would be provided with a four-valve-bridge-circuit. Our invention may be used, however, using either a self-rectified circuit, a half-wave rectified circuit, or a fullwave rectified bridge circuit, as will be readily understood.

What we claim is:

1. In the combination of an X-ray tube having a high tension tube energizing circuit and a filament energizing circuit including a fila ment transformer having primary and secondary windings, switch means controlling energi zation of said X-ray tube, a space discharge tube operatively connected with said switch means, said space discharge tube having control electrode means, a variable resistance timing means in circuit with said control electrode means, a control transformer having a primary winding in series circuit with said filament transformer primary winding and having a secondary winding, and said control transformer secondary winding in electrical circuit with said control electrode means and varying the voltage applied to the latter.

2. In the combination of an X-ray tube hav ing a high tension tube energizing circuit including a high tension transformer having primary and secondary windings and including a filament energizing circuit having a filament transformer with primary and secondary windings, means controlling energization of said X-ray tube including a space discharge tube having control electrode means, timing means for selecting a variable resistance, a first control transformer having a primary winding in circuit with said high tension transformer primary winding, a second control transformer having a primary winding in circuit with said filament transformer primary winding, each of said control transformers having a secondary winding, and said secondary windings ofsaid control transformers and said variable resistance in electrical circuit with said control electrode means.

3. In the combination of an X-ray tube having a high tension tube energizing circuit including a high tension transformer having a primary winding and having a secondary winding with a central secondary grounded circuit, means controlling energization of said X-ray tube including a space discharge tube having control electrode means, timing means for selecting a variable resistance, a control transformer having a primary winding in said central secondary grounded circuit and having a secondary winding, and said control transformer secondary winding and said variable resistance in electrical circuit with said control electrode means.

4. In the combination of an X-ray tube having a high tension tube energizing circuit including a high tension transformer having a primary winding and having a secondary winding including a central secondary grounded circuit, means controlling energization of said X-ray tube including a space discharge tube having control electrode means, timing means for selecting a variable resistance, a first control transformer having a primary winding in circuit with said high tension transformer primary winding,

a second control transformer having a primary winding in said central secondary grounded circuit, both of said controi transformers having secondary windings, and said control transformer secondary windings and said variable resistance in electrical circuit with said control electrode means.

EDWIN R. GOLDFIELD.

JACK BALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 1 Date 2,053,587 Van Den Berg Sept. 8, 1936 2,339,902 Akers et-al. Jan. 25, 1944 2,379,125 Weisglass June 26, 1945 2,404,905 Garretson July 30, 1946 FOREIGN PATENTS Number Country Date 517,349 Great Britain Jan. 26, 1940 547,030 Great Britain Aug. 11, 1942 552,945 Great Britain Apr. 30, 1943

US685095A 1946-07-20 1946-07-20 X-ray tube safety device Expired - Lifetime US2572258A (en)

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US5798848 US2583095A (en) 1946-07-20 1948-11-02 X-ray tube safety device

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Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2745020A (en) * 1950-01-06 1956-05-08 Gen Electric Electrical protective system
DE945581C (en) * 1953-12-25 1956-07-12 Electricitaets Ges Sanitas Mit Roentgenapparat
US2883554A (en) * 1953-06-04 1959-04-21 Land Air Inc Control means for regulating the output of x-ray apparatus
US3069548A (en) * 1958-12-17 1962-12-18 Machlett Lab Inc Protective circuits for electron tubes
US3075082A (en) * 1959-07-23 1963-01-22 Westinghouse Electric Corp X-ray apparatus
US3323012A (en) * 1963-04-04 1967-05-30 Caps Res Ltd Superposed high frequeny starting circuit for discharge lamp
US3459941A (en) * 1966-10-24 1969-08-05 Gen Electric Instantaneous overload protector for an x-ray tube responsive to a combination of tube factor settings
US3842280A (en) * 1970-12-23 1974-10-15 Picker Corp Protective circuit for limiting the input power applied to an x-ray tube and method of operation
US20050093483A1 (en) * 2003-10-21 2005-05-05 Ball Newton E. Systems and methods for a transformer configuration for driving multiple gas discharge tubes in parallel
US7173382B2 (en) 2005-03-31 2007-02-06 Microsemi Corporation Nested balancing topology for balancing current among multiple lamps
US7183724B2 (en) 2003-12-16 2007-02-27 Microsemi Corporation Inverter with two switching stages for driving lamp
US7187139B2 (en) 2003-09-09 2007-03-06 Microsemi Corporation Split phase inverters for CCFL backlight system
US7242147B2 (en) 2003-10-06 2007-07-10 Microsemi Corporation Current sharing scheme for multiple CCF lamp operation
US7250731B2 (en) 2004-04-07 2007-07-31 Microsemi Corporation Primary side current balancing scheme for multiple CCF lamp operation
US7391172B2 (en) 2003-09-23 2008-06-24 Microsemi Corporation Optical and temperature feedbacks to control display brightness
US7411360B2 (en) 2002-12-13 2008-08-12 Microsemi Corporation Apparatus and method for striking a fluorescent lamp
US7414371B1 (en) 2005-11-21 2008-08-19 Microsemi Corporation Voltage regulation loop with variable gain control for inverter circuit
US7468722B2 (en) 2004-02-09 2008-12-23 Microsemi Corporation Method and apparatus to control display brightness with ambient light correction
US7569998B2 (en) 2006-07-06 2009-08-04 Microsemi Corporation Striking and open lamp regulation for CCFL controller
US7646152B2 (en) 2004-04-01 2010-01-12 Microsemi Corporation Full-bridge and half-bridge compatible driver timing schedule for direct drive backlight system
US20100123400A1 (en) * 2008-11-20 2010-05-20 Microsemi Corporation Method and apparatus for driving ccfl at low burst duty cycle rates
US7755595B2 (en) 2004-06-07 2010-07-13 Microsemi Corporation Dual-slope brightness control for transflective displays
US7977888B2 (en) 2003-10-06 2011-07-12 Microsemi Corporation Direct coupled balancer drive for floating lamp structure
US8598795B2 (en) 2011-05-03 2013-12-03 Microsemi Corporation High efficiency LED driving method
US8754581B2 (en) 2011-05-03 2014-06-17 Microsemi Corporation High efficiency LED driving method for odd number of LED strings
US9030119B2 (en) 2010-07-19 2015-05-12 Microsemi Corporation LED string driver arrangement with non-dissipative current balancer

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2053587A (en) * 1932-02-08 1936-09-08 Philips Nv X-ray installation
GB517349A (en) * 1938-07-25 1940-01-26 Gen Electric Co Ltd Improvements in or relating to control arrangements for x-ray apparatus
GB547030A (en) * 1940-12-10 1942-08-11 Charles Sydney Norton Improvements in and relating to protective devices for x-ray apparatus
GB552945A (en) * 1942-02-09 1943-04-30 Arthur Charles Gunstone Overload protection on x-ray control apparatus
US2339902A (en) * 1942-03-18 1944-01-25 Herbert S Akers X-ray apparatus
US2379125A (en) * 1942-07-04 1945-06-26 Westinghouse Electric Corp X-ray tube protective system
US2404905A (en) * 1944-01-31 1946-07-30 Philips Corp Electrical circuit arrangement

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2053587A (en) * 1932-02-08 1936-09-08 Philips Nv X-ray installation
GB517349A (en) * 1938-07-25 1940-01-26 Gen Electric Co Ltd Improvements in or relating to control arrangements for x-ray apparatus
GB547030A (en) * 1940-12-10 1942-08-11 Charles Sydney Norton Improvements in and relating to protective devices for x-ray apparatus
GB552945A (en) * 1942-02-09 1943-04-30 Arthur Charles Gunstone Overload protection on x-ray control apparatus
US2339902A (en) * 1942-03-18 1944-01-25 Herbert S Akers X-ray apparatus
US2379125A (en) * 1942-07-04 1945-06-26 Westinghouse Electric Corp X-ray tube protective system
US2404905A (en) * 1944-01-31 1946-07-30 Philips Corp Electrical circuit arrangement

Cited By (46)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2745020A (en) * 1950-01-06 1956-05-08 Gen Electric Electrical protective system
US2883554A (en) * 1953-06-04 1959-04-21 Land Air Inc Control means for regulating the output of x-ray apparatus
DE945581C (en) * 1953-12-25 1956-07-12 Electricitaets Ges Sanitas Mit Roentgenapparat
US3069548A (en) * 1958-12-17 1962-12-18 Machlett Lab Inc Protective circuits for electron tubes
US3075082A (en) * 1959-07-23 1963-01-22 Westinghouse Electric Corp X-ray apparatus
US3323012A (en) * 1963-04-04 1967-05-30 Caps Res Ltd Superposed high frequeny starting circuit for discharge lamp
US3459941A (en) * 1966-10-24 1969-08-05 Gen Electric Instantaneous overload protector for an x-ray tube responsive to a combination of tube factor settings
US3842280A (en) * 1970-12-23 1974-10-15 Picker Corp Protective circuit for limiting the input power applied to an x-ray tube and method of operation
US7411360B2 (en) 2002-12-13 2008-08-12 Microsemi Corporation Apparatus and method for striking a fluorescent lamp
US7187139B2 (en) 2003-09-09 2007-03-06 Microsemi Corporation Split phase inverters for CCFL backlight system
US7952298B2 (en) 2003-09-09 2011-05-31 Microsemi Corporation Split phase inverters for CCFL backlight system
US7525255B2 (en) 2003-09-09 2009-04-28 Microsemi Corporation Split phase inverters for CCFL backlight system
US7391172B2 (en) 2003-09-23 2008-06-24 Microsemi Corporation Optical and temperature feedbacks to control display brightness
US7560875B2 (en) 2003-10-06 2009-07-14 Microsemi Corporation Balancing transformers for multi-lamp operation
US8008867B2 (en) 2003-10-06 2011-08-30 Microsemi Corporation Arrangement suitable for driving floating CCFL based backlight
US7977888B2 (en) 2003-10-06 2011-07-12 Microsemi Corporation Direct coupled balancer drive for floating lamp structure
US8222836B2 (en) 2003-10-06 2012-07-17 Microsemi Corporation Balancing transformers for multi-lamp operation
US7990072B2 (en) 2003-10-06 2011-08-02 Microsemi Corporation Balancing arrangement with reduced amount of balancing transformers
US7294971B2 (en) 2003-10-06 2007-11-13 Microsemi Corporation Balancing transformers for ring balancer
US7242147B2 (en) 2003-10-06 2007-07-10 Microsemi Corporation Current sharing scheme for multiple CCF lamp operation
US7932683B2 (en) 2003-10-06 2011-04-26 Microsemi Corporation Balancing transformers for multi-lamp operation
US7279851B2 (en) * 2003-10-21 2007-10-09 Microsemi Corporation Systems and methods for fault protection in a balancing transformer
US7141933B2 (en) 2003-10-21 2006-11-28 Microsemi Corporation Systems and methods for a transformer configuration for driving multiple gas discharge tubes in parallel
US7250726B2 (en) 2003-10-21 2007-07-31 Microsemi Corporation Systems and methods for a transformer configuration with a tree topology for current balancing in gas discharge lamps
US20050093483A1 (en) * 2003-10-21 2005-05-05 Ball Newton E. Systems and methods for a transformer configuration for driving multiple gas discharge tubes in parallel
US7187140B2 (en) 2003-12-16 2007-03-06 Microsemi Corporation Lamp current control using profile synthesizer
US7183724B2 (en) 2003-12-16 2007-02-27 Microsemi Corporation Inverter with two switching stages for driving lamp
US7265499B2 (en) 2003-12-16 2007-09-04 Microsemi Corporation Current-mode direct-drive inverter
US7239087B2 (en) 2003-12-16 2007-07-03 Microsemi Corporation Method and apparatus to drive LED arrays using time sharing technique
US7468722B2 (en) 2004-02-09 2008-12-23 Microsemi Corporation Method and apparatus to control display brightness with ambient light correction
US8223117B2 (en) 2004-02-09 2012-07-17 Microsemi Corporation Method and apparatus to control display brightness with ambient light correction
US7646152B2 (en) 2004-04-01 2010-01-12 Microsemi Corporation Full-bridge and half-bridge compatible driver timing schedule for direct drive backlight system
US7965046B2 (en) 2004-04-01 2011-06-21 Microsemi Corporation Full-bridge and half-bridge compatible driver timing schedule for direct drive backlight system
US7557517B2 (en) 2004-04-07 2009-07-07 Microsemi Corporation Primary side current balancing scheme for multiple CCF lamp operation
US7250731B2 (en) 2004-04-07 2007-07-31 Microsemi Corporation Primary side current balancing scheme for multiple CCF lamp operation
US7755595B2 (en) 2004-06-07 2010-07-13 Microsemi Corporation Dual-slope brightness control for transflective displays
US7173382B2 (en) 2005-03-31 2007-02-06 Microsemi Corporation Nested balancing topology for balancing current among multiple lamps
US7414371B1 (en) 2005-11-21 2008-08-19 Microsemi Corporation Voltage regulation loop with variable gain control for inverter circuit
US7569998B2 (en) 2006-07-06 2009-08-04 Microsemi Corporation Striking and open lamp regulation for CCFL controller
US8358082B2 (en) 2006-07-06 2013-01-22 Microsemi Corporation Striking and open lamp regulation for CCFL controller
US8093839B2 (en) 2008-11-20 2012-01-10 Microsemi Corporation Method and apparatus for driving CCFL at low burst duty cycle rates
US20100123400A1 (en) * 2008-11-20 2010-05-20 Microsemi Corporation Method and apparatus for driving ccfl at low burst duty cycle rates
US9030119B2 (en) 2010-07-19 2015-05-12 Microsemi Corporation LED string driver arrangement with non-dissipative current balancer
US8598795B2 (en) 2011-05-03 2013-12-03 Microsemi Corporation High efficiency LED driving method
US8754581B2 (en) 2011-05-03 2014-06-17 Microsemi Corporation High efficiency LED driving method for odd number of LED strings
USRE46502E1 (en) 2011-05-03 2017-08-01 Microsemi Corporation High efficiency LED driving method

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