CA1116690A - High frequency circuit for operating a high-intensity, gaseous discharge lamp - Google Patents
High frequency circuit for operating a high-intensity, gaseous discharge lampInfo
- Publication number
- CA1116690A CA1116690A CA000266718A CA266718A CA1116690A CA 1116690 A CA1116690 A CA 1116690A CA 000266718 A CA000266718 A CA 000266718A CA 266718 A CA266718 A CA 266718A CA 1116690 A CA1116690 A CA 1116690A
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- CA
- Canada
- Prior art keywords
- circuit
- lamp
- operating
- transistor
- high frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
- H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
- H05B41/2885—Static converters especially adapted therefor; Control thereof
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
- H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
- H05B41/292—Arrangements for protecting lamps or circuits against abnormal operating conditions
- H05B41/2928—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the lamp against abnormal operating conditions
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
Landscapes
- Circuit Arrangements For Discharge Lamps (AREA)
- Dc-Dc Converters (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A high frequency drive circuit operating as a push-pull, Class C oscillator for driving a high-intensity, gaseous dis-charge lamp and avoiding the use of a relatively large ballast coil. A highly stable power supply for operating in conjunction with such circuit is also provided.
A high frequency drive circuit operating as a push-pull, Class C oscillator for driving a high-intensity, gaseous dis-charge lamp and avoiding the use of a relatively large ballast coil. A highly stable power supply for operating in conjunction with such circuit is also provided.
Description
6~
HIGH FREQUENCY CIRCUIT FOR OPERATING
A HIGH-INTENSITY, GASEOUS DISCHARGE L~P
BACXGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a circuit for operating a high intensity, gaseous-discharge lamp without requiring a large ballast transformer, and more specifically, for operating such a lamp at a frequency higher than acoustic resonance for such lamps.
DESCRIPTION OF THE PRIOR ART
Conventional ballasting of high intensity discharge lamps, such as metal-additive arc lamps, employ transformer-like coils, capacitors, or inductor coils in various combinations to pro-vide proper voltage for starting and limiting the current during operation. Such ballasts are large, relatively expensive, and not efficient at low cost. Simple inductor ballasts are avail-able; however, they provide poor regulation for line voltage variations.
Regulating solid state ballasts have been developed, but heretofore no commercial ballasts have been developed which is suitable for the operating conditions of high pressure mercury, sodium and metal halide lamps to give proper control of lamp wattage for high ranges of lamp voltages, line fluctuations and temperatures.
Although theoretically a lamp may be operated on a com-bination of applied dc and ac, which would give lower noise than ac alone, it has been discovered that the application of dc is bad for lamp efficiency and life. The application of low audio frequency ac causes noisy ballast conditions. The application of medium frequency ac causes noisy and unstable lamp conditions.
In fact, the high pitch whine of lamps operated under such conditions is extremeIy unpleasant. Therefore, it has not been recognized that high frequency ac may be used with regard to lamps; however, life tests and lumen tests have revealed that high frequency operation beyond a certain range is per-fectly satisfactory, both as to providing acceptab~e lamp operating stability and an absence of audible noise.
Therefore, it is a feature of this invention to provide an improved operating circuit for a high intensity gaseous discharge lamp that provides a high frequency mode of operation.
SUMMARY OF THE INVENTION
The invention in one broad aspect pertains to a circuit for operating a high frequency, gaseous-discharge lamp, comprising a ballast impedance connectable to the lamp, and an oscillator operating at a frequency above the acoustic resonances of the lamp connectable thereto, the oscillator providing the lamp with high power and high frequency current.
In another aspect the invention pertains to a circuit for operating a high frequency, gaseous-discharge lamp including a ballast connected to receive a DC source voltate and a base-driven triode transistor for supplying at least a portion ofthe high frequency current to the ballast. The improvement comprises regulating means connected to the ballast and the base-driven triode transistor for changing the conduction time of the transistor when the voltage applied to the ballast exceeds a predetermined value.
,~ .
A still further aspect of the invention comprehends a circuit for operating a high frequency, gaseous-discharge lamp, comprising a push-pull, Class C oscillator having a resonant circuit including a high-Q coil connected to a first operating electrode of the lamp, the oscillator being connected to a power source and the resonant circuit establishing an operating frequency for the oscillator at a frequency above the acoustic resonant frequence of the lamp. A ballast impedance is connected to a second operating electrode of the lamp and the high-Q coil in the resonant circuit provides the lamp with high power and high frequency current.
A preferred embodiment of the present invention includes a drive circuit having a push-pull, Class C oscillator employ-ing a high efficiency transformer, the center tap of the trans-former being connected to a dc power source. The oscillator halves are driven in such a fashion so that the application of current provides high frequency at high efficiency to a tank-and-lamp network, which from lamp starting, normal operation, to lamp failure may exhibit a wide range of load impedances to the drive circuit.
' . .
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Also disclosed is a coil configuration used in the tank-andwlamp network for providing an unloaded high-Q of approxi-mately 300 in conjunction with the operating conditions existing for mèrcury, metal halide and high pressure sodium lamps.
Finally, a stable power supply including emergency fea-tures for operation with the circuit is also described, such circuit being capable of removing transients from the applied line voltage. The circuit may incorporate a battery connected through diode connec-tions when the nominal output, dc-line voltage from the power supply varies beyond predetermined limits, either high or low.
BRIEF DESCRIPTION OF TIIE DRAWING
So that the manner in which the above-recited features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the invention and are therefore not to be considered limit-ing of its scope, for the invention may admit to other equally effective embodiments.
IN THE DRAWINGS:
FIG. 1 is a simplified schematic diagram of the present invention showing a preferred embodiment of a push-pull, Class C oscillator connected for driving a high frequency, gaseous-discharge lamp.
FIG. 2 are wave form diagrams illustrating the operation of the preferred circuit illustrated in Fig. 1.
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FIG. 3 diagramatically illus~ratcs in three dimensional form, high-Q for a preferred high-Q coil confic3uration embodi-ment.
FIG. ~ illustrates a cross section of a preferred higll-Q coil configuration.
FIG. 5 is a par~ial schematic diagram of a regulating circuit that may be connected as part of the circuit show in Fig. 1.
FIG. 6 illustrates in simplified block-a}ld-scllematic-diagram form a preferred power supply for operation with the preferred circuit illustrated in Fig. 1.
FIG. 7 is a schematic diagram of a preferred power supply for operation with the preferred circuit illustrated in Fig. 1.
FIG. 8 is a schematic diagram of a preferred embodiment of the ~ network shown in Fig. 7, appearing with Fig. l.
FIG. 9 is a schematic diagram of an alternate preferred embodiment of the ~ network shown in Fig. 7, with Fig. 1.
FIG. 10 is a partial schematic diagram of an alternate preferred embodiment of a regulating circuit that may be connected as part of the circuit shown in Fig. l.
FIG. 11 is a partial schematic diagram of an alternate preferred embodiment of a power supply for operation with the r circuit illustrated in Fig. 1.
DESCRIPTION OF PR~I;'ERRED EMBODIMENTS
-Now referring to the drawings and first to Fig. 1, a high frequency, gaseous-discharge lamp operating circuit is shown in~accordance with the present invention. Lamp 10 in--cludes two operating electrodes. One is connected to capa-citor 12, WhiCIl may be characterized as a mica ballastcapacitor. Capacitor 12 is connected in series with trans-6~
former winding 14, which is then connected to the other op-erati~g electrode of lamp 10 to complete a ballast-like con-nection thereto. As will be explained, this completes a current source connection to a tank-and-lamp network. Con-nected in shunt with transformer winding 14 is a resonant or tank circuit comprising the parallel combination of capacitor 16 and high-Q coil 18. These components aid in stahilizing the frequency of operation of the current applied to lamp 10 at a high frequency above the acoustic resonance of the lamp, preferably in the range between 60 and 100 kHz.
Transformer winding 14 has a center tap Z0 for application of a dc voltage via connecting terminal 22. Transformer winding 14 is part of a push-pull, Class C oscillator having alterna-tively driving networks especially suited for providing alter-nate current conduction to transformer winding 14 for efficient high-frequency operation of lamp 10. Conduction time of the drive circuit for transformer wlnding 14, as hereafter further explained, is for about one-quarter or 90 degrees of the operating cycle of the voltage across the lamp.
The frequency of operation of the curren-t and voltage applied to lamp 10 is determined by the resonance of -the tank circuit comprising coil 18 and capacitor 16, with capacitor 12 exerting some influence. Normally, capacitor 16 will have at least twice the capacitance value as capacitor 12, although it may have many times such value. Moreover, when lamp 10 represents a large load, the influence of capacitor 12 lessens and hence, the frequency of operation is almost solely depen-dent on the values of components 16 and 18.
Viewing the right side of the dra~ing, npn triode tran-sistor 24 is connected with its collector terminal to the ad-jacent end of transformer winding 14 and its emitter connected . r~ k~
to ground. Alt}lough illustrated as an npn transistor, it is understood that component 24 may be a pnp, an SCR or other active device connected in a suitable circuit for functional operation in accordance with the present invention. The base of transistor 24 is connected to the drive circuit, the drive voltage and current being principally derived from transformer winding 26 and capacitor 28, as hereafter explained.
A fast recovery clamping diode 25 is connected across the collector-emitter connection of transistor 24. ~ resistor L0 30 connected in parallel with another fast acting diode 32 connects the base of transistor 24 to ground. A slow-acting diode 34 is connected in series with capacitor 28 and the base of transistor 24. Resistor 36 is connected across diode 34. ' In operation of transistor 24 and its related components, an applied dc voltage on terminal 22 causes conduction of transistor 24. The voltage drop across starter resistor 38 biases transistor 24 into its linear region of operation.
Positive feedback supplied by transformer isolation winding 26, which may be only a single turn magnetically coupled with winding 14, causes conduction turn on to become greater with each cycle. When the high gain region of transistor 24 is reached, it then turns on hard and the oscillator will be operating at full amplitude. Once full turn-on operation of transistor 24 has been established, the currents through wind-ing 14 and through the tank circuit comprising coil 18 and capacitor 16 drive transistor 40 into conduction on alternate half cycles from the conduction of transistor 24. Operation is sustained for transistor 40 in a manner similar to that for transistor 24, described more fully hereinafter.
Under steady operating conditions, fast turn-on of trans-istor 24 at each cycle is influenced primarily by three factors.
First, previous to turn-on, the base emitter junction of trans-istor 24 is barely reversed biased because diode 32 clamps the reverse biasing voltage to a small value. This means that at turn-on, there is only a small negative voltage on this base-emitter junction that needs to be overcome.
Second, capacitor 2~, diode 34, and winding 26 in the base circuit of transistor 24 for supplying the drive voltage are all low impedance devices. Therefore, the drive source to trans-istor 24 respcnds rapidly.
Third, diode 32 is a fast-acting diode. Diode 32 C~n-ducts during turn-off. If it continued to conduct for a short time during turn-on, then it would take current from the drive circuit, but it does not, and therefore the full source is im-mediately applied to turn on the transistor.
Turn off of transistor 24 is fast primarily because of the slow action of series diode 34. As previously mentioned, diode 34 has a low impedance. Its slow recovery causes a fast reverse current drain of transistor 24 during turn off, and hence, causes transistor 24 to turn off rapidly. Note that even though turn-off is rapid, it is not "hard" ~i.e., a large base-emitter voltage is not developed) because of the clamping action of diode 32.
Diode 25 is also a fast acting diode, primarily because of operating conditions during start up and when the tank cir-cuit becomes unloaded (such as with a failure of lamp 10). The dlode clamps the voltage applied to it when the tank circuit tries to force voltage VCe below ground and therefore keeps transistor 24 from being overdriven. The reverse recovery time is fast to prevent shorting out the tank.
Resistor 30 protects transistor 24 during build up of oscillations at start up when the transistor is off by reducing the collector-to-emitter leakage current.
Alternate transistor 40 operates in a similar manner to that just described for transistor 24, but on alternate fre-quency cycles of the developed current determined by the resonant tank-and-lamp circuit. Variable resistors 36 and 42, around the respective series capacitors, and variable capaci-tors 28 and 44, in respective series therewith, are part of the drive circuits for transistors 24 and 40 to provide ad-justment for operation of the circuit.
"Q" or "Q factor" is a figure of merit for an energy-storing device or a tuned circuit, which for the embodiment disclosed herein would be coil 18. Q is equal to the reac-tance of such device divided by its resistance. The Q deter-mines the rate of decay of stored energy and hence the higher the Q the more efficient the device. Therefore, high Q opera-tion in a gaseous-discharge lamp circuit is highly desirable.
Diagrammatically, and assuming core, frequency, voltage and temperature to be constant, high-Q for a given coil may be represented by Fig. 3 which shows a three-dimensional rela-tionship between number of turns and air gap to achieve ahigh-Q operation. This Q curve is arrived at experimentally by the following procedure. A selected number of turns is chosen for a given size pot core. A wire size is selected and bundled with other similar wires to form a litz wire combina-tion so that the core may be wound to nearly completely fill the bobbin and thereby minimize copper loss. Then a gap is selected and a point on the Q "mountain" is measured. Other gap spacings are then made and other points at that number of turns measured. The entire process is then repeated for other numbers of turns. By this process the "peak" of the Q mountain 6~
is determined, as illustrated in Fig. 3. A coil for operating as coil 18 for providing high voltage and high frequency to gaseous-discharge lamp 10 may be made on a pot core made of ferrite material.
Following the above described procedure and using No. 40 insulated wire, a bundle of such wire comprising 85 strands twisted together was wound on a No. 2616 FERROXCUB ~ nylon bobbin in such a manner as to form five layers of eig~it turns each. Each layer was insulated from the adjoining layers by MYLAR~ tape. The two parts of the core (with a wound bobbin in between) were separated so as to form an air gap of approxi-mately 65 thousandths of an inch. A nylon screw through the two parts of the core was used to secure them together. It is important that a metallic screw not be used. It is important that both the bobbin and the screw be of materials having a low dielectric loss at high fequency.
A coil made in the above manner is nominally rated for a Q of 300 at 240 volts rms, 100 kHz. Such a coil is illustrated in cross section in Fig. 4.
In a similar fashion, a twisted bundle of 189 No. 44 insulated wire strands was found acceptable in making a similar coil. Further, to achieve a higher voltage rating, a coil of 60 turns was made for operating in conjunction with multi-vapor lamp operation.
Note that the tank circuit is connected to lamp 10 and hence the reactance and resistance of lamp 10 influence the Q of the entire tank-and-lamp circuit. The efficiency of the tank or resonant circuit may be represented by the following formula:
Efficiency : Qu Ql Qu wherein: Qu = ~ of tank circuit only without other components Ql = Q of circuit under load Hence, when unloaded Qu is high, the efficiency of the tank circuit may be very high on the order of 97-99 percent.
An efficiency of about 85 percent is achievable for the over-all circuit shown in Fig. 1 with the coil structure herein disclosed.
The operation of the tank-and-lamp circuit may be ana-- logized to the operation of a mechanical swing with little friction. At the end of each arc of the swing, a small push is provided. The more the friction (load), the more the power consumption and hence the more the push necessary to make the swing make the same arc. Hence, as seen in Fig. 2, Ic is for a short duration and the transistor is slightly over driven (beyond a sine wave drive).
The transformer comprising winding 14 and isolation wind-ing 26 and its alternate may be made identically to coil 14, except in this case, the air gap may be eliminated.
Transformer winding 14 may also include taps 46 and 48 spaced equal distance from center tap 20 toward the two res-pective ends of the winding. Such taps provide connection of the transistors to provide a higher voltage to the lamp than with the end connections, as shown. This is particularly ad-vantageous in operating a multivapor lamp 10.
Fig. 5 illustrates a regulation circuit acting in conjunc-tion with the circuit shown in Fig. 1. There are two identical .
networks 100 and 102 operating in conjunction with the respec-tive alternate halves of the oscillator. For simplicity of illustration, only the half operating in conjunction with 6C"~
.
transistor 40 is illustrated in detail.
' Connected across capacitor 44 and its accompanyin(J trans-former isolation windiny 111 is the followinc; series conl-ection:
diode 104, collector-emitter of pnp transistor 106 and resistor 108. Connected to the high side of the winding is the cathode of diode 110 and conneeted to the anode thereof to ground is capacitor 112. Connected across capacitor 112 is the series combination of Zener diode 114, variable resistor 116 and diode 118 for matching the base-emitter drop of transistor 120. l'he variable tap on resistor 116 is connected to the base of pnp transistor 120. The emitter of transistor 120 is connected to ground throuyh resistor 122 and the collector thereof is connected to the anode of 2ener diode 114 via resistor 124. The collector of transistor 120 is connected to terminal 126, other-wise designated VRl and the base of transistor 106 is con~lected through resistor 128 to terminal 130, otherwise designated Bl.
In operation of ~he regulation cireuit of Fig. 5, the voltage on the base winding, designated with numeral 111, charges eapaeitor 112 throug}l 110. When the eharge on eapacitor 112 exeeeds the voltage thresholds of Zener diode 114 and diode 118, eurrent flows aeross resistor 116. This turns on trans-istor 120 as an amplifier. As the voltage on resistor 122 inereases, the voltage on r,esistor 124 increases and the voltage at terminal 126 decreases with respect to ground. Assume that terminal 126 is conneeted to terminal 130, an alternative con-neetion thereof as explained hereinafter, as the voltage on resistor 108 decreases eurrent through transistor lO6 decreases, henee redueing the amount of discharge f~rom capacitor 44.
The voltage on base winding 111 plus capacitor 44 appears across ,the series eonneetion of resistors 326 and 108, transistor 106 and diode 104. When transistor 106 conducts less, the less capacitor 44 discharges. I~ence, on the next half-cycle of voltage operation of transistor 40, the less current capacitor 44 can deliver before charge up. On Fig. 2, this may be seen as a higher intersection of V~l with the curve of VBl and hence the delay in starting of IBl.
Hence, it may be seen that when the voltage on base winding 111 exceeds a predetermined value, diode 110 conducts to cause a regulation voltage signal VRl to occur at terminal 126. The adjustment of resistor 116 determines the value of the output.
Although regulating voltage signal VRl may be attached to terminal 130, its preferred connection is to alternate terminal B2 of regulating network 102 and terminal 130 is preferably connected to receive the alternate regulating voltage signal VR2 from network 102. This is because when transistor 40 is conducting, base winding 111 is loaded. It is best to sense the unloaded winding voltage for regulation purposes, WhiC]l would indicate the preference for the connections shown in Fig. 5.
In any event, when there is a regulating signal applied to terminal 130, there is conduction of transistor 106 to partly discharge capacitor 44 and to thereby regulate the circuit.
This protects transistor 40 from overheating by preventing an extensive overdrive condition. In similar fashion transistor 24 is also protected.
Although one regulation circuit is shown, many alternative arrangements are also available. For example, an alternate pre-ferred embodiment is illustra-ted in Fig. 10.
The embodiment which is illustrated is a partial schematic diagram which assumes a similar network is connected to the opposite end of transformer winding 14 so that the complete circuit operates as a push-pull, Class C oscillator as previously descrlbed. The exception is that with this ernbodiment, only one regulating circuit is necessary, to be described hereinafter.
Components numbered less than 200 in the Fig. 10 embodim~nt identify similar components to those illustrated in Figs. 1 and 5, which are connected similar fashion.
Resistor 310 is connected between capacitor 312, across which the dc input from the power supply is applied, and cir-cuit common which may be a floating ground. This is also true for the common connectors illustrated with a ground symbol in other drawings. Diode 314 is connected in parallel across resistor 310. The cathode of diode 314 is connected throuyh current limiting resistor 316 to the anode of light emitting diode (L.E.D.) 318. The cathode of L.E.D. 318 is connected to common. L.E.D. 318 is packaged in an opto-isolator with photo-transistor 320. Phototransistor 320 is connected betweell the anode of diode 110 and the base of npn transistor 120.
Base resistor 322 is connected to the base of transistor 120 and capacitor 324 is connected to its collector. The output from transistor 120 is taken from its collector and is labelled ''Vc''. Connection of this output 126 is made to points or terminals "Bl" (130) and "B2", previously described.
Connected across capacitor 44 and its accompanying trans-former isolation winding 111 is the following series connection:
variable resistor 326, diode 104, collector-emitter of Darling-ton pair transistors 106 and resistor 108. The base of Dar-lington pair transistors 106 is connected through resistor 128 to point 130 (Bl), which point is connected to point 126, where Vc is present.
The circuit will regulate and operate in a satisEactory - manner without further connection. Ilowever, to ensure smoot}
operation with both halves of the push-pull oscillator, the junction point between diode 110 and capacitor 112 can be connected to an anode of a diode 330, the cathode of which is connected to transEormer isolation winding 26. In this event, ~ r~ ?~
capacitor 112 is charged up eacll half cycle of oscillator operation.
In operation, this regulation circuit senses the presence of too much base drive by sensing the ne~ative current through power device or transistor 40 with resistor 310. Negative current through device 40 causes a positive voltage across resistor 310. Thls voltage causes current to flow througll L.E.D. 318, and hence phototransistor 320 conducts current.
When this occurs, the base drive to tL-ansistor 120 is reduced to cause Vc to decrease and to allow less current to flow through Darlington pair 106. Thus, capacitor 44 discharges less and the next cycle of base drive to transistor 40 is less than before.
The base drive increase is controlled by the time con-stant of the R of resistor 124 and the C of capacitor 324. The base drive decrease is controlled by the time constant of C o~
capacitor 324 and the R of resistor 128 (and its counterpart at terminal B2). So that an HID lamp being ignited will not cause tank circuit oscillations to die out, the time constant of resistor 124 and capacitor 324 is a shorter time constant of the two.
Transistor 106 is preferably a Darlington pair in the Fig. 10 embodiment for greater amplification. This permits capacitor 324 to be smaller and allows regulation Witll less conduction by transistor 120.
It may also be noted that a variable resistor 326 is present in the collector-emitter series connection of transis-tor 106 to provide a variable control for the base drive to power device 40 when the HID lamp or lamps connected to the circuit warms up. As the lamp or lamps warm up, transistor 106 begins to conduct. The rate of conduction is not linear, how-ever. When the lamp is approximately one-third brightness, 6~
.
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transistor 106 is substantially completely turned on and hence the current therethrough controls the base drive. Therefore, resistor 42 provides control for the base drive current during start up and resistor 326 provides control for the base drive current after the lamp or lamps have reached a certain warm up condition.
Now turning to a suitable power supply, reference is made to the circuit illustrated in Fig. 6. The applied ac source imput is connected to the illustrative power supply at termi-nals 50 and 52. Input coils 54 and 56 connected to these terminals, respectively, and varistor 58, connected in parallel with resistor 60 and capacitor 62, are connected across the ac input line to perform a transient clipping operation.
Triac 64 is a power control device connected in serieswith one side of the ac line and controlled by variable con-duction phase control 66 to provide ac power control over a wide range of applied power.
Device 64 may also be an SCR or other active device having a controllable gate for regulating conduction through the device for only a part of each half cycle of the applied voltage.
~hen the detected dc output from rectifier 6~ is too high, control circuit 66 connected thereto triggers the gate to lessen the conduction time, and hence the effective output.
The control circuit may include a convenient timing network having an RC time constant circuit to provide this function.
A more complete circuit is illustrated in Fig. 7.
The output from the power control device 64 is applied to rectifier 68. The output from the rectifier is nominally the dc line voltage. However, transients may be present and therefore capacitor 70, together with yet another transient circuit to be described, is connected to prevent such tran-sients from being applied to the output.
Nominal output from -the rectifier appears on output line 72. The anode of diode 74 is connected thereto with its cath-ode connected to the top of battery 76. Also connected to the cathode of diode 74 is resistor 78, which, in turn, is con-nected to a small dc power supply 80, the other side of which is connec-ted to line 72. For illustration purposes, this supply is shown as providing 10 volts. Therefore, the connec-tion to resistor 78 is at a level 10 volts higher than the voltage on line 72.
By example, the voltage on line 72 may be nominally 170 volts. This would make the output of power supply 80 at l80 volts. Assuming a 5-volt drop across reslstor 78, the voltage at the cathode of diode 74 is at 175 volts. When the line vol-tage exceeds a predetermined value slightly above 175 volts, the same as the cathode voltage on diode 74 (175 volts), diode 74 conducts and reduces the line voltage to 175 volts.
The batteries also effectively clips any transients that still may occur on the output from the rectifier, but because of the other transient attentuators, the batteries are not required for this purpose.
Battery 76 as illustrated includes many cells and pro-vides a voltage at a predetermined level slightly below the nominal line voltage. In any event, connected near.the top side of the battery, but just below the top, is the anode of diode 82. The cathode of diode 82 is connected to output line 72. Hence, when the line voltage falls below a pre-determined level, battery 76 completely takes over through diode 82 and the output therefrom is applied as the line voltage to the output.
Note that low voltage power supply 80 also provides a trickle charge to battery 76.
A low voltage sensing and cutout circuit 84 may be connected to the battery so that when there is battery failure (output drops below an acceptable predetermined level), the battery will be disconnected from the circuit and not be a drain on low voltage power supply 80. Additionally, sensing circuit 84 may also detect an extended power outage of the ac source, which would cause the lamp module(s) to put a drain on the batteries over a long period of time. In this event, a switch in line 72, for example at terminal 90, would bc opened to disconnect the load from the batteries.
Note that the battery circuits are principally for emergency operation and not required when the output from rectifier 68 is within acceptable limits or to suppress transients.
A so-called crow bar circuit 86 may be used to protect the circuit from sudden extreme surges, such as might be caused by lightning. One such device may merely be a vol-tage amplitude sensing device that shorts out, and therefore places a short across the input line, to blow a fuse or cir-cuit breaker (not shown). Because replacing fuses or re-setting circuit breakers is a nuisance, a preferred crow bar arrangement is shown in Fig. 6. Such a preferred device 86 includes a voltage sensing element and a relay coil connected to normally closed relay contacts 88 in the input line to rectifier 68. When the voltage on this line exceeds a pre-determined value, an internal relay coil in device 86 is energized to open contacts 88. When the applied line voltage returns to a more normal level, the sensing element de-energizes the internal relay coil and closes contacts 88.
Crow bar circuit 86 may also be sensitive to rate-of-voltage change so as to operate faster than just with an amplitude change. This device is strictly a safety device and not required for circuit operation. A detail preferred network is shown in Fig. 7.
The output on line 72 is filtered from remaining tran-sients by-capacitor 70, as previously mentioned. It also may be seen that with a low line voltage condition requiring switching to the battery, as above explained, the voltage on capacitor 70 helps prevent the lamp connection from being in-terrupted and therefore the possible loss of light.
Control circuit 66 connected to control the conduction through power control device 64 may take the form of a circuit for monitoring the output dc level on line 72 including a light emitting diode. That is, the higher the voltage above a preset level (such às determined by a series-connected Zener diode), the brighter the produced light. This produced light is detectable by a photo-sensitive device in an RC network for controlling the angle of conduction (time of conduction) through device 64. A detail network operating in this manner is shown in Fig. 7.
The output is applied to output terminals 90 and 92.
These terminals, one of which may be grounded, such as illus-trated at 92, are applied as the dc input to terminal 22 inFig. 1.
Now referring to Fig. 7, it may be seen that a detail circuit operating in the manner just described for Fig. 1 is illustrated. For example, rectifier 68 is illustrated by the conventional diode bridge comprising diodes 68a, 68b, 68c and 68d. Varistor 58 and the filter including resistor 60 and capacitor 62 in the simplified circuit of Fig. 1 are expanded to include varistors 58a, 58b and 58c and there are two tran-sient filters, one including resistor 60b and capacitor 62a and the other including resistor 60b and capacitor 62b.
Inductors 54 and 56 are expanded to include inductors 54a and 54b and 56a and 56b. Inductors 54a and 56a at the input are preferably ferrite core inductors. These inductors and . ~ r~ 6.~
the first stage varistors and transient filters attenuate fast transients and reduce their frequencies so that subse-quent tape-wound, steel-core inductors 54a and 54b and varis-tor 58c, resistor 60b, and capacitor 62b can at;tenuate the existing transients still further.
The crow bar circuit 86 is shown in Fiy. 7 as including many components. Relay contacts 88 are actuated by coil 200, connected in parallel with resistor 202 and in series with triac 204. Connected from resistor 202 to the gate terminal of the triac is box Z circuit 206, which is explained more fully below. The gate resistor is resistor 208. This cir-cuit forms a load-disconnecting, transient-shunting, non-fuse blowing protection circuit.
Box Z circuit 206 may take the form of either of the circuits shown in Figs. 8 and 9, or their equivalents. For example, the Fig. 8 circuit includes two opposite facing Zener diodes 210 and 212 connected in parallel with capacitor 214. Fig. 9 shows a parallel combination of Zener diode 216 and capacitor 218 connected to diodes 220, 222, 224 and 226.
These diodes form two paths around the parallel combination, each path comprising two diodes. The connections to the cir-cuit of Fig. 7 are made to the juncture between the two diodes in each of the paths. In operation, the Zener diodes operate as amplitude sensing devices and the capacitors in the re-spective circuits are sensitive to rate of voltage change.
When the gate voltage on the triac exceeds about 1 volt, caused by either sensing a large voltage amplitude or a fast voltage increase, then the triac conducts. This energi7.es relay coii 200 to open normally closed contacts 88. The re-moval of the triggering condition will cause the contacts to re-close.
Control circuit 66 may be characterized as a soft-start , ~ ' f~ 7~
circuit for the operation of the power supply. Ultimately, the application of source voltage to the rectifier bridge shown in Fig. 7 is controlled by triac 230, the conduction time of which is determined by the operation of pulse trans-former 232. Windiny 232 is magnetically linked to winding 234 in the cathode circuit of programmable unijunction transistor (PUT) 236. The control of the operation of PUT
236 is described below.
The gate connection to PUT 236 is connected to a rec-tified dc voltage via variable resistor 238. The rectifiedvoltage is derived from bridge rectifier 240 connected across the ac source line through current limiting resistors 239 and 241 just ahead of triac 230. The timing of the con-duction of PUT 236 is determined by the voltage difference between the voltage applled via resistor 238 and the voltage applied to the anode of PUT 236. Both the voltage applied to the anode and to the gate of PUT 236 are important to its conduction.
That is, conduction is dependent on the arithmetic difference between the voltage applied to the anode and gate.
Therefore, the setting of resistor 238 "programs" what anode voltage is required to produce conduction. The dc voltage applied to resistor 238 is developed by bridge rectifier 240.
A Zener diode 242 and bleeder resistor 244 insures that the voltage applied to resistor 238 never exceeds a predetermined value.
The output from bridge rectifier 240 is also connected through resistors 246 to a time constant control network con-nected to the anode of PUT 236. This time constant network includes capacitors 248 and 250 and resistors 246 and 252.
Basically, the charging of capacitor 248 through resistor 246 determines the soft start or the ultimate speed of r 1 ~
conduction or angle advancement in the conduction of triac 230 and the charging of capacitor 250 through resistor 252 determines the phase or conduction angle of triac 230. The RC time constants of these networks and the voltages applied to them, as explained below, are important in the operation of this regulation circuit.
The photo transistor voltage is determined by the brightness of the light emitting diode connected in series with resistor 262 and Zener diode 264 across dc line 72.
10 The resistor and Zener diode protect L.E.D. 260 against an overload condition.
By this operation, it may be seen that the L.E.D~ and photo transistor regulate the dc output voltage and that there is really no regulation of the ac input. A too high dc voltage causes Zener diode 264 and L.E.D. 260 to conduct, turning photo transistor 258 partly on and retards the phase or firing angle of triac 230 to thus lower the dc output to about the voltage for causing conduction of Zener diode 264 and L.E.D. 260.
Fuses 270 and 272 at the input and 274 and 276 provide further safety to the circuit.
Now referring to Fig. 11, an alternate embodiment of a suitable power supply is illustrated, the primary differences to the circuit shown in Fig. 7 being in the network associated triac 204 operating as a crow bar power device. The transient clipping and attenuation circuit 63 preceding this network is the same as that illustrated for Fig. 7. Triac 230 for ultimately controlling the application of source voltage to rectifier bridge 68 is connected in the-positive line. Its gate voltage for determining the time of its conduction is controlled by the operation of pulse transformer 232, as with the Fig. 7 embodimen.t. The main terminals of triac 230 are connected to rectifier 6~, wllich is precede-l by bleedel-resistor 2~9.
Connected across the line just ahead of resistor 219 is the RC network comprising resistor 215 and capacitor 217.
Back-to-back Zener dio~es 209 are connected to the high side of capacitor 217 and, through resistor 207, to the gate ter-minal of triac 204. The main terminals of a triac 205 are connected between the high side of capacitor 217 and the gate of triac 204. The gate of triac 205 is connected to the junction between resistor 207 and back-to-back Zener diodes 209. Gate resistor 211 to triac 204 completes the network.
In operation, crow bar power device 204 is turned on only when the voltage across capacitor 217 exceeds the Zener voltage across Zener diodes 209~ Transients occurriny wllen triac 230, which may be functionally characterized as a soft-start/regulation circuit po~er device, is off, are not applied to the ac input of rectifier bridge 68. ~ence, capacitor 217 is not charged up and the crow bar is not activated. When triac 230 is on and a transient occurs that is large enougll to endanger the electronic ballast or ballasts connected to the dc output, the transients remaining after treatment by transient suppression circuit 63 are applied to the ac side of rectifier bridge 68 and to RC network comprising resistor 215 and capacitor 217. If the voltage on capacitor 217 is great enough, triac 204 is triggered as a result of back-to-back Zener diode 209 triggering triac 205. Since the transient can be either positive or negative, one or the other of the two Zener diodes will conduct to initiate the triggering action.
It should be also noted that resistor 215 and capacitor 217, in combination with capacitor G2b, form a ~nubber for ;~
13i.1~i ~ ~r~
in-line triac 230.
While particular embodiments of the invention have been shown and described, it will be understood that the invention is not limited thereto, since modifications may be made and will become apparent to those skilled in the art. ~or exam-ple, the operation of a single lamp module as illustrated in Figs. 1 and 5 has been described. It is understood that the preferred embodiment will include a plurality of such modules connected to a common power supply, such as illustrated in Figs. 6 and 7.
Furthermore, it may be recognized that the dc power supply which has been described is a preferred embodiment with somewhat elaborate features for ensuring highly stable dc output to the high frequency operating circuit for the lamp. Such an elaborate supply may not be desirable for installation not having extremely important stability re-quirements.
HIGH FREQUENCY CIRCUIT FOR OPERATING
A HIGH-INTENSITY, GASEOUS DISCHARGE L~P
BACXGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a circuit for operating a high intensity, gaseous-discharge lamp without requiring a large ballast transformer, and more specifically, for operating such a lamp at a frequency higher than acoustic resonance for such lamps.
DESCRIPTION OF THE PRIOR ART
Conventional ballasting of high intensity discharge lamps, such as metal-additive arc lamps, employ transformer-like coils, capacitors, or inductor coils in various combinations to pro-vide proper voltage for starting and limiting the current during operation. Such ballasts are large, relatively expensive, and not efficient at low cost. Simple inductor ballasts are avail-able; however, they provide poor regulation for line voltage variations.
Regulating solid state ballasts have been developed, but heretofore no commercial ballasts have been developed which is suitable for the operating conditions of high pressure mercury, sodium and metal halide lamps to give proper control of lamp wattage for high ranges of lamp voltages, line fluctuations and temperatures.
Although theoretically a lamp may be operated on a com-bination of applied dc and ac, which would give lower noise than ac alone, it has been discovered that the application of dc is bad for lamp efficiency and life. The application of low audio frequency ac causes noisy ballast conditions. The application of medium frequency ac causes noisy and unstable lamp conditions.
In fact, the high pitch whine of lamps operated under such conditions is extremeIy unpleasant. Therefore, it has not been recognized that high frequency ac may be used with regard to lamps; however, life tests and lumen tests have revealed that high frequency operation beyond a certain range is per-fectly satisfactory, both as to providing acceptab~e lamp operating stability and an absence of audible noise.
Therefore, it is a feature of this invention to provide an improved operating circuit for a high intensity gaseous discharge lamp that provides a high frequency mode of operation.
SUMMARY OF THE INVENTION
The invention in one broad aspect pertains to a circuit for operating a high frequency, gaseous-discharge lamp, comprising a ballast impedance connectable to the lamp, and an oscillator operating at a frequency above the acoustic resonances of the lamp connectable thereto, the oscillator providing the lamp with high power and high frequency current.
In another aspect the invention pertains to a circuit for operating a high frequency, gaseous-discharge lamp including a ballast connected to receive a DC source voltate and a base-driven triode transistor for supplying at least a portion ofthe high frequency current to the ballast. The improvement comprises regulating means connected to the ballast and the base-driven triode transistor for changing the conduction time of the transistor when the voltage applied to the ballast exceeds a predetermined value.
,~ .
A still further aspect of the invention comprehends a circuit for operating a high frequency, gaseous-discharge lamp, comprising a push-pull, Class C oscillator having a resonant circuit including a high-Q coil connected to a first operating electrode of the lamp, the oscillator being connected to a power source and the resonant circuit establishing an operating frequency for the oscillator at a frequency above the acoustic resonant frequence of the lamp. A ballast impedance is connected to a second operating electrode of the lamp and the high-Q coil in the resonant circuit provides the lamp with high power and high frequency current.
A preferred embodiment of the present invention includes a drive circuit having a push-pull, Class C oscillator employ-ing a high efficiency transformer, the center tap of the trans-former being connected to a dc power source. The oscillator halves are driven in such a fashion so that the application of current provides high frequency at high efficiency to a tank-and-lamp network, which from lamp starting, normal operation, to lamp failure may exhibit a wide range of load impedances to the drive circuit.
' . .
6~&~
Also disclosed is a coil configuration used in the tank-andwlamp network for providing an unloaded high-Q of approxi-mately 300 in conjunction with the operating conditions existing for mèrcury, metal halide and high pressure sodium lamps.
Finally, a stable power supply including emergency fea-tures for operation with the circuit is also described, such circuit being capable of removing transients from the applied line voltage. The circuit may incorporate a battery connected through diode connec-tions when the nominal output, dc-line voltage from the power supply varies beyond predetermined limits, either high or low.
BRIEF DESCRIPTION OF TIIE DRAWING
So that the manner in which the above-recited features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the invention and are therefore not to be considered limit-ing of its scope, for the invention may admit to other equally effective embodiments.
IN THE DRAWINGS:
FIG. 1 is a simplified schematic diagram of the present invention showing a preferred embodiment of a push-pull, Class C oscillator connected for driving a high frequency, gaseous-discharge lamp.
FIG. 2 are wave form diagrams illustrating the operation of the preferred circuit illustrated in Fig. 1.
f \ ~-~
FIG. 3 diagramatically illus~ratcs in three dimensional form, high-Q for a preferred high-Q coil confic3uration embodi-ment.
FIG. ~ illustrates a cross section of a preferred higll-Q coil configuration.
FIG. 5 is a par~ial schematic diagram of a regulating circuit that may be connected as part of the circuit show in Fig. 1.
FIG. 6 illustrates in simplified block-a}ld-scllematic-diagram form a preferred power supply for operation with the preferred circuit illustrated in Fig. 1.
FIG. 7 is a schematic diagram of a preferred power supply for operation with the preferred circuit illustrated in Fig. 1.
FIG. 8 is a schematic diagram of a preferred embodiment of the ~ network shown in Fig. 7, appearing with Fig. l.
FIG. 9 is a schematic diagram of an alternate preferred embodiment of the ~ network shown in Fig. 7, with Fig. 1.
FIG. 10 is a partial schematic diagram of an alternate preferred embodiment of a regulating circuit that may be connected as part of the circuit shown in Fig. l.
FIG. 11 is a partial schematic diagram of an alternate preferred embodiment of a power supply for operation with the r circuit illustrated in Fig. 1.
DESCRIPTION OF PR~I;'ERRED EMBODIMENTS
-Now referring to the drawings and first to Fig. 1, a high frequency, gaseous-discharge lamp operating circuit is shown in~accordance with the present invention. Lamp 10 in--cludes two operating electrodes. One is connected to capa-citor 12, WhiCIl may be characterized as a mica ballastcapacitor. Capacitor 12 is connected in series with trans-6~
former winding 14, which is then connected to the other op-erati~g electrode of lamp 10 to complete a ballast-like con-nection thereto. As will be explained, this completes a current source connection to a tank-and-lamp network. Con-nected in shunt with transformer winding 14 is a resonant or tank circuit comprising the parallel combination of capacitor 16 and high-Q coil 18. These components aid in stahilizing the frequency of operation of the current applied to lamp 10 at a high frequency above the acoustic resonance of the lamp, preferably in the range between 60 and 100 kHz.
Transformer winding 14 has a center tap Z0 for application of a dc voltage via connecting terminal 22. Transformer winding 14 is part of a push-pull, Class C oscillator having alterna-tively driving networks especially suited for providing alter-nate current conduction to transformer winding 14 for efficient high-frequency operation of lamp 10. Conduction time of the drive circuit for transformer wlnding 14, as hereafter further explained, is for about one-quarter or 90 degrees of the operating cycle of the voltage across the lamp.
The frequency of operation of the curren-t and voltage applied to lamp 10 is determined by the resonance of -the tank circuit comprising coil 18 and capacitor 16, with capacitor 12 exerting some influence. Normally, capacitor 16 will have at least twice the capacitance value as capacitor 12, although it may have many times such value. Moreover, when lamp 10 represents a large load, the influence of capacitor 12 lessens and hence, the frequency of operation is almost solely depen-dent on the values of components 16 and 18.
Viewing the right side of the dra~ing, npn triode tran-sistor 24 is connected with its collector terminal to the ad-jacent end of transformer winding 14 and its emitter connected . r~ k~
to ground. Alt}lough illustrated as an npn transistor, it is understood that component 24 may be a pnp, an SCR or other active device connected in a suitable circuit for functional operation in accordance with the present invention. The base of transistor 24 is connected to the drive circuit, the drive voltage and current being principally derived from transformer winding 26 and capacitor 28, as hereafter explained.
A fast recovery clamping diode 25 is connected across the collector-emitter connection of transistor 24. ~ resistor L0 30 connected in parallel with another fast acting diode 32 connects the base of transistor 24 to ground. A slow-acting diode 34 is connected in series with capacitor 28 and the base of transistor 24. Resistor 36 is connected across diode 34. ' In operation of transistor 24 and its related components, an applied dc voltage on terminal 22 causes conduction of transistor 24. The voltage drop across starter resistor 38 biases transistor 24 into its linear region of operation.
Positive feedback supplied by transformer isolation winding 26, which may be only a single turn magnetically coupled with winding 14, causes conduction turn on to become greater with each cycle. When the high gain region of transistor 24 is reached, it then turns on hard and the oscillator will be operating at full amplitude. Once full turn-on operation of transistor 24 has been established, the currents through wind-ing 14 and through the tank circuit comprising coil 18 and capacitor 16 drive transistor 40 into conduction on alternate half cycles from the conduction of transistor 24. Operation is sustained for transistor 40 in a manner similar to that for transistor 24, described more fully hereinafter.
Under steady operating conditions, fast turn-on of trans-istor 24 at each cycle is influenced primarily by three factors.
First, previous to turn-on, the base emitter junction of trans-istor 24 is barely reversed biased because diode 32 clamps the reverse biasing voltage to a small value. This means that at turn-on, there is only a small negative voltage on this base-emitter junction that needs to be overcome.
Second, capacitor 2~, diode 34, and winding 26 in the base circuit of transistor 24 for supplying the drive voltage are all low impedance devices. Therefore, the drive source to trans-istor 24 respcnds rapidly.
Third, diode 32 is a fast-acting diode. Diode 32 C~n-ducts during turn-off. If it continued to conduct for a short time during turn-on, then it would take current from the drive circuit, but it does not, and therefore the full source is im-mediately applied to turn on the transistor.
Turn off of transistor 24 is fast primarily because of the slow action of series diode 34. As previously mentioned, diode 34 has a low impedance. Its slow recovery causes a fast reverse current drain of transistor 24 during turn off, and hence, causes transistor 24 to turn off rapidly. Note that even though turn-off is rapid, it is not "hard" ~i.e., a large base-emitter voltage is not developed) because of the clamping action of diode 32.
Diode 25 is also a fast acting diode, primarily because of operating conditions during start up and when the tank cir-cuit becomes unloaded (such as with a failure of lamp 10). The dlode clamps the voltage applied to it when the tank circuit tries to force voltage VCe below ground and therefore keeps transistor 24 from being overdriven. The reverse recovery time is fast to prevent shorting out the tank.
Resistor 30 protects transistor 24 during build up of oscillations at start up when the transistor is off by reducing the collector-to-emitter leakage current.
Alternate transistor 40 operates in a similar manner to that just described for transistor 24, but on alternate fre-quency cycles of the developed current determined by the resonant tank-and-lamp circuit. Variable resistors 36 and 42, around the respective series capacitors, and variable capaci-tors 28 and 44, in respective series therewith, are part of the drive circuits for transistors 24 and 40 to provide ad-justment for operation of the circuit.
"Q" or "Q factor" is a figure of merit for an energy-storing device or a tuned circuit, which for the embodiment disclosed herein would be coil 18. Q is equal to the reac-tance of such device divided by its resistance. The Q deter-mines the rate of decay of stored energy and hence the higher the Q the more efficient the device. Therefore, high Q opera-tion in a gaseous-discharge lamp circuit is highly desirable.
Diagrammatically, and assuming core, frequency, voltage and temperature to be constant, high-Q for a given coil may be represented by Fig. 3 which shows a three-dimensional rela-tionship between number of turns and air gap to achieve ahigh-Q operation. This Q curve is arrived at experimentally by the following procedure. A selected number of turns is chosen for a given size pot core. A wire size is selected and bundled with other similar wires to form a litz wire combina-tion so that the core may be wound to nearly completely fill the bobbin and thereby minimize copper loss. Then a gap is selected and a point on the Q "mountain" is measured. Other gap spacings are then made and other points at that number of turns measured. The entire process is then repeated for other numbers of turns. By this process the "peak" of the Q mountain 6~
is determined, as illustrated in Fig. 3. A coil for operating as coil 18 for providing high voltage and high frequency to gaseous-discharge lamp 10 may be made on a pot core made of ferrite material.
Following the above described procedure and using No. 40 insulated wire, a bundle of such wire comprising 85 strands twisted together was wound on a No. 2616 FERROXCUB ~ nylon bobbin in such a manner as to form five layers of eig~it turns each. Each layer was insulated from the adjoining layers by MYLAR~ tape. The two parts of the core (with a wound bobbin in between) were separated so as to form an air gap of approxi-mately 65 thousandths of an inch. A nylon screw through the two parts of the core was used to secure them together. It is important that a metallic screw not be used. It is important that both the bobbin and the screw be of materials having a low dielectric loss at high fequency.
A coil made in the above manner is nominally rated for a Q of 300 at 240 volts rms, 100 kHz. Such a coil is illustrated in cross section in Fig. 4.
In a similar fashion, a twisted bundle of 189 No. 44 insulated wire strands was found acceptable in making a similar coil. Further, to achieve a higher voltage rating, a coil of 60 turns was made for operating in conjunction with multi-vapor lamp operation.
Note that the tank circuit is connected to lamp 10 and hence the reactance and resistance of lamp 10 influence the Q of the entire tank-and-lamp circuit. The efficiency of the tank or resonant circuit may be represented by the following formula:
Efficiency : Qu Ql Qu wherein: Qu = ~ of tank circuit only without other components Ql = Q of circuit under load Hence, when unloaded Qu is high, the efficiency of the tank circuit may be very high on the order of 97-99 percent.
An efficiency of about 85 percent is achievable for the over-all circuit shown in Fig. 1 with the coil structure herein disclosed.
The operation of the tank-and-lamp circuit may be ana-- logized to the operation of a mechanical swing with little friction. At the end of each arc of the swing, a small push is provided. The more the friction (load), the more the power consumption and hence the more the push necessary to make the swing make the same arc. Hence, as seen in Fig. 2, Ic is for a short duration and the transistor is slightly over driven (beyond a sine wave drive).
The transformer comprising winding 14 and isolation wind-ing 26 and its alternate may be made identically to coil 14, except in this case, the air gap may be eliminated.
Transformer winding 14 may also include taps 46 and 48 spaced equal distance from center tap 20 toward the two res-pective ends of the winding. Such taps provide connection of the transistors to provide a higher voltage to the lamp than with the end connections, as shown. This is particularly ad-vantageous in operating a multivapor lamp 10.
Fig. 5 illustrates a regulation circuit acting in conjunc-tion with the circuit shown in Fig. 1. There are two identical .
networks 100 and 102 operating in conjunction with the respec-tive alternate halves of the oscillator. For simplicity of illustration, only the half operating in conjunction with 6C"~
.
transistor 40 is illustrated in detail.
' Connected across capacitor 44 and its accompanyin(J trans-former isolation windiny 111 is the followinc; series conl-ection:
diode 104, collector-emitter of pnp transistor 106 and resistor 108. Connected to the high side of the winding is the cathode of diode 110 and conneeted to the anode thereof to ground is capacitor 112. Connected across capacitor 112 is the series combination of Zener diode 114, variable resistor 116 and diode 118 for matching the base-emitter drop of transistor 120. l'he variable tap on resistor 116 is connected to the base of pnp transistor 120. The emitter of transistor 120 is connected to ground throuyh resistor 122 and the collector thereof is connected to the anode of 2ener diode 114 via resistor 124. The collector of transistor 120 is connected to terminal 126, other-wise designated VRl and the base of transistor 106 is con~lected through resistor 128 to terminal 130, otherwise designated Bl.
In operation of ~he regulation cireuit of Fig. 5, the voltage on the base winding, designated with numeral 111, charges eapaeitor 112 throug}l 110. When the eharge on eapacitor 112 exeeeds the voltage thresholds of Zener diode 114 and diode 118, eurrent flows aeross resistor 116. This turns on trans-istor 120 as an amplifier. As the voltage on resistor 122 inereases, the voltage on r,esistor 124 increases and the voltage at terminal 126 decreases with respect to ground. Assume that terminal 126 is conneeted to terminal 130, an alternative con-neetion thereof as explained hereinafter, as the voltage on resistor 108 decreases eurrent through transistor lO6 decreases, henee redueing the amount of discharge f~rom capacitor 44.
The voltage on base winding 111 plus capacitor 44 appears across ,the series eonneetion of resistors 326 and 108, transistor 106 and diode 104. When transistor 106 conducts less, the less capacitor 44 discharges. I~ence, on the next half-cycle of voltage operation of transistor 40, the less current capacitor 44 can deliver before charge up. On Fig. 2, this may be seen as a higher intersection of V~l with the curve of VBl and hence the delay in starting of IBl.
Hence, it may be seen that when the voltage on base winding 111 exceeds a predetermined value, diode 110 conducts to cause a regulation voltage signal VRl to occur at terminal 126. The adjustment of resistor 116 determines the value of the output.
Although regulating voltage signal VRl may be attached to terminal 130, its preferred connection is to alternate terminal B2 of regulating network 102 and terminal 130 is preferably connected to receive the alternate regulating voltage signal VR2 from network 102. This is because when transistor 40 is conducting, base winding 111 is loaded. It is best to sense the unloaded winding voltage for regulation purposes, WhiC]l would indicate the preference for the connections shown in Fig. 5.
In any event, when there is a regulating signal applied to terminal 130, there is conduction of transistor 106 to partly discharge capacitor 44 and to thereby regulate the circuit.
This protects transistor 40 from overheating by preventing an extensive overdrive condition. In similar fashion transistor 24 is also protected.
Although one regulation circuit is shown, many alternative arrangements are also available. For example, an alternate pre-ferred embodiment is illustra-ted in Fig. 10.
The embodiment which is illustrated is a partial schematic diagram which assumes a similar network is connected to the opposite end of transformer winding 14 so that the complete circuit operates as a push-pull, Class C oscillator as previously descrlbed. The exception is that with this ernbodiment, only one regulating circuit is necessary, to be described hereinafter.
Components numbered less than 200 in the Fig. 10 embodim~nt identify similar components to those illustrated in Figs. 1 and 5, which are connected similar fashion.
Resistor 310 is connected between capacitor 312, across which the dc input from the power supply is applied, and cir-cuit common which may be a floating ground. This is also true for the common connectors illustrated with a ground symbol in other drawings. Diode 314 is connected in parallel across resistor 310. The cathode of diode 314 is connected throuyh current limiting resistor 316 to the anode of light emitting diode (L.E.D.) 318. The cathode of L.E.D. 318 is connected to common. L.E.D. 318 is packaged in an opto-isolator with photo-transistor 320. Phototransistor 320 is connected betweell the anode of diode 110 and the base of npn transistor 120.
Base resistor 322 is connected to the base of transistor 120 and capacitor 324 is connected to its collector. The output from transistor 120 is taken from its collector and is labelled ''Vc''. Connection of this output 126 is made to points or terminals "Bl" (130) and "B2", previously described.
Connected across capacitor 44 and its accompanying trans-former isolation winding 111 is the following series connection:
variable resistor 326, diode 104, collector-emitter of Darling-ton pair transistors 106 and resistor 108. The base of Dar-lington pair transistors 106 is connected through resistor 128 to point 130 (Bl), which point is connected to point 126, where Vc is present.
The circuit will regulate and operate in a satisEactory - manner without further connection. Ilowever, to ensure smoot}
operation with both halves of the push-pull oscillator, the junction point between diode 110 and capacitor 112 can be connected to an anode of a diode 330, the cathode of which is connected to transEormer isolation winding 26. In this event, ~ r~ ?~
capacitor 112 is charged up eacll half cycle of oscillator operation.
In operation, this regulation circuit senses the presence of too much base drive by sensing the ne~ative current through power device or transistor 40 with resistor 310. Negative current through device 40 causes a positive voltage across resistor 310. Thls voltage causes current to flow througll L.E.D. 318, and hence phototransistor 320 conducts current.
When this occurs, the base drive to tL-ansistor 120 is reduced to cause Vc to decrease and to allow less current to flow through Darlington pair 106. Thus, capacitor 44 discharges less and the next cycle of base drive to transistor 40 is less than before.
The base drive increase is controlled by the time con-stant of the R of resistor 124 and the C of capacitor 324. The base drive decrease is controlled by the time constant of C o~
capacitor 324 and the R of resistor 128 (and its counterpart at terminal B2). So that an HID lamp being ignited will not cause tank circuit oscillations to die out, the time constant of resistor 124 and capacitor 324 is a shorter time constant of the two.
Transistor 106 is preferably a Darlington pair in the Fig. 10 embodiment for greater amplification. This permits capacitor 324 to be smaller and allows regulation Witll less conduction by transistor 120.
It may also be noted that a variable resistor 326 is present in the collector-emitter series connection of transis-tor 106 to provide a variable control for the base drive to power device 40 when the HID lamp or lamps connected to the circuit warms up. As the lamp or lamps warm up, transistor 106 begins to conduct. The rate of conduction is not linear, how-ever. When the lamp is approximately one-third brightness, 6~
.
.
transistor 106 is substantially completely turned on and hence the current therethrough controls the base drive. Therefore, resistor 42 provides control for the base drive current during start up and resistor 326 provides control for the base drive current after the lamp or lamps have reached a certain warm up condition.
Now turning to a suitable power supply, reference is made to the circuit illustrated in Fig. 6. The applied ac source imput is connected to the illustrative power supply at termi-nals 50 and 52. Input coils 54 and 56 connected to these terminals, respectively, and varistor 58, connected in parallel with resistor 60 and capacitor 62, are connected across the ac input line to perform a transient clipping operation.
Triac 64 is a power control device connected in serieswith one side of the ac line and controlled by variable con-duction phase control 66 to provide ac power control over a wide range of applied power.
Device 64 may also be an SCR or other active device having a controllable gate for regulating conduction through the device for only a part of each half cycle of the applied voltage.
~hen the detected dc output from rectifier 6~ is too high, control circuit 66 connected thereto triggers the gate to lessen the conduction time, and hence the effective output.
The control circuit may include a convenient timing network having an RC time constant circuit to provide this function.
A more complete circuit is illustrated in Fig. 7.
The output from the power control device 64 is applied to rectifier 68. The output from the rectifier is nominally the dc line voltage. However, transients may be present and therefore capacitor 70, together with yet another transient circuit to be described, is connected to prevent such tran-sients from being applied to the output.
Nominal output from -the rectifier appears on output line 72. The anode of diode 74 is connected thereto with its cath-ode connected to the top of battery 76. Also connected to the cathode of diode 74 is resistor 78, which, in turn, is con-nected to a small dc power supply 80, the other side of which is connec-ted to line 72. For illustration purposes, this supply is shown as providing 10 volts. Therefore, the connec-tion to resistor 78 is at a level 10 volts higher than the voltage on line 72.
By example, the voltage on line 72 may be nominally 170 volts. This would make the output of power supply 80 at l80 volts. Assuming a 5-volt drop across reslstor 78, the voltage at the cathode of diode 74 is at 175 volts. When the line vol-tage exceeds a predetermined value slightly above 175 volts, the same as the cathode voltage on diode 74 (175 volts), diode 74 conducts and reduces the line voltage to 175 volts.
The batteries also effectively clips any transients that still may occur on the output from the rectifier, but because of the other transient attentuators, the batteries are not required for this purpose.
Battery 76 as illustrated includes many cells and pro-vides a voltage at a predetermined level slightly below the nominal line voltage. In any event, connected near.the top side of the battery, but just below the top, is the anode of diode 82. The cathode of diode 82 is connected to output line 72. Hence, when the line voltage falls below a pre-determined level, battery 76 completely takes over through diode 82 and the output therefrom is applied as the line voltage to the output.
Note that low voltage power supply 80 also provides a trickle charge to battery 76.
A low voltage sensing and cutout circuit 84 may be connected to the battery so that when there is battery failure (output drops below an acceptable predetermined level), the battery will be disconnected from the circuit and not be a drain on low voltage power supply 80. Additionally, sensing circuit 84 may also detect an extended power outage of the ac source, which would cause the lamp module(s) to put a drain on the batteries over a long period of time. In this event, a switch in line 72, for example at terminal 90, would bc opened to disconnect the load from the batteries.
Note that the battery circuits are principally for emergency operation and not required when the output from rectifier 68 is within acceptable limits or to suppress transients.
A so-called crow bar circuit 86 may be used to protect the circuit from sudden extreme surges, such as might be caused by lightning. One such device may merely be a vol-tage amplitude sensing device that shorts out, and therefore places a short across the input line, to blow a fuse or cir-cuit breaker (not shown). Because replacing fuses or re-setting circuit breakers is a nuisance, a preferred crow bar arrangement is shown in Fig. 6. Such a preferred device 86 includes a voltage sensing element and a relay coil connected to normally closed relay contacts 88 in the input line to rectifier 68. When the voltage on this line exceeds a pre-determined value, an internal relay coil in device 86 is energized to open contacts 88. When the applied line voltage returns to a more normal level, the sensing element de-energizes the internal relay coil and closes contacts 88.
Crow bar circuit 86 may also be sensitive to rate-of-voltage change so as to operate faster than just with an amplitude change. This device is strictly a safety device and not required for circuit operation. A detail preferred network is shown in Fig. 7.
The output on line 72 is filtered from remaining tran-sients by-capacitor 70, as previously mentioned. It also may be seen that with a low line voltage condition requiring switching to the battery, as above explained, the voltage on capacitor 70 helps prevent the lamp connection from being in-terrupted and therefore the possible loss of light.
Control circuit 66 connected to control the conduction through power control device 64 may take the form of a circuit for monitoring the output dc level on line 72 including a light emitting diode. That is, the higher the voltage above a preset level (such às determined by a series-connected Zener diode), the brighter the produced light. This produced light is detectable by a photo-sensitive device in an RC network for controlling the angle of conduction (time of conduction) through device 64. A detail network operating in this manner is shown in Fig. 7.
The output is applied to output terminals 90 and 92.
These terminals, one of which may be grounded, such as illus-trated at 92, are applied as the dc input to terminal 22 inFig. 1.
Now referring to Fig. 7, it may be seen that a detail circuit operating in the manner just described for Fig. 1 is illustrated. For example, rectifier 68 is illustrated by the conventional diode bridge comprising diodes 68a, 68b, 68c and 68d. Varistor 58 and the filter including resistor 60 and capacitor 62 in the simplified circuit of Fig. 1 are expanded to include varistors 58a, 58b and 58c and there are two tran-sient filters, one including resistor 60b and capacitor 62a and the other including resistor 60b and capacitor 62b.
Inductors 54 and 56 are expanded to include inductors 54a and 54b and 56a and 56b. Inductors 54a and 56a at the input are preferably ferrite core inductors. These inductors and . ~ r~ 6.~
the first stage varistors and transient filters attenuate fast transients and reduce their frequencies so that subse-quent tape-wound, steel-core inductors 54a and 54b and varis-tor 58c, resistor 60b, and capacitor 62b can at;tenuate the existing transients still further.
The crow bar circuit 86 is shown in Fiy. 7 as including many components. Relay contacts 88 are actuated by coil 200, connected in parallel with resistor 202 and in series with triac 204. Connected from resistor 202 to the gate terminal of the triac is box Z circuit 206, which is explained more fully below. The gate resistor is resistor 208. This cir-cuit forms a load-disconnecting, transient-shunting, non-fuse blowing protection circuit.
Box Z circuit 206 may take the form of either of the circuits shown in Figs. 8 and 9, or their equivalents. For example, the Fig. 8 circuit includes two opposite facing Zener diodes 210 and 212 connected in parallel with capacitor 214. Fig. 9 shows a parallel combination of Zener diode 216 and capacitor 218 connected to diodes 220, 222, 224 and 226.
These diodes form two paths around the parallel combination, each path comprising two diodes. The connections to the cir-cuit of Fig. 7 are made to the juncture between the two diodes in each of the paths. In operation, the Zener diodes operate as amplitude sensing devices and the capacitors in the re-spective circuits are sensitive to rate of voltage change.
When the gate voltage on the triac exceeds about 1 volt, caused by either sensing a large voltage amplitude or a fast voltage increase, then the triac conducts. This energi7.es relay coii 200 to open normally closed contacts 88. The re-moval of the triggering condition will cause the contacts to re-close.
Control circuit 66 may be characterized as a soft-start , ~ ' f~ 7~
circuit for the operation of the power supply. Ultimately, the application of source voltage to the rectifier bridge shown in Fig. 7 is controlled by triac 230, the conduction time of which is determined by the operation of pulse trans-former 232. Windiny 232 is magnetically linked to winding 234 in the cathode circuit of programmable unijunction transistor (PUT) 236. The control of the operation of PUT
236 is described below.
The gate connection to PUT 236 is connected to a rec-tified dc voltage via variable resistor 238. The rectifiedvoltage is derived from bridge rectifier 240 connected across the ac source line through current limiting resistors 239 and 241 just ahead of triac 230. The timing of the con-duction of PUT 236 is determined by the voltage difference between the voltage applled via resistor 238 and the voltage applied to the anode of PUT 236. Both the voltage applied to the anode and to the gate of PUT 236 are important to its conduction.
That is, conduction is dependent on the arithmetic difference between the voltage applied to the anode and gate.
Therefore, the setting of resistor 238 "programs" what anode voltage is required to produce conduction. The dc voltage applied to resistor 238 is developed by bridge rectifier 240.
A Zener diode 242 and bleeder resistor 244 insures that the voltage applied to resistor 238 never exceeds a predetermined value.
The output from bridge rectifier 240 is also connected through resistors 246 to a time constant control network con-nected to the anode of PUT 236. This time constant network includes capacitors 248 and 250 and resistors 246 and 252.
Basically, the charging of capacitor 248 through resistor 246 determines the soft start or the ultimate speed of r 1 ~
conduction or angle advancement in the conduction of triac 230 and the charging of capacitor 250 through resistor 252 determines the phase or conduction angle of triac 230. The RC time constants of these networks and the voltages applied to them, as explained below, are important in the operation of this regulation circuit.
The photo transistor voltage is determined by the brightness of the light emitting diode connected in series with resistor 262 and Zener diode 264 across dc line 72.
10 The resistor and Zener diode protect L.E.D. 260 against an overload condition.
By this operation, it may be seen that the L.E.D~ and photo transistor regulate the dc output voltage and that there is really no regulation of the ac input. A too high dc voltage causes Zener diode 264 and L.E.D. 260 to conduct, turning photo transistor 258 partly on and retards the phase or firing angle of triac 230 to thus lower the dc output to about the voltage for causing conduction of Zener diode 264 and L.E.D. 260.
Fuses 270 and 272 at the input and 274 and 276 provide further safety to the circuit.
Now referring to Fig. 11, an alternate embodiment of a suitable power supply is illustrated, the primary differences to the circuit shown in Fig. 7 being in the network associated triac 204 operating as a crow bar power device. The transient clipping and attenuation circuit 63 preceding this network is the same as that illustrated for Fig. 7. Triac 230 for ultimately controlling the application of source voltage to rectifier bridge 68 is connected in the-positive line. Its gate voltage for determining the time of its conduction is controlled by the operation of pulse transformer 232, as with the Fig. 7 embodimen.t. The main terminals of triac 230 are connected to rectifier 6~, wllich is precede-l by bleedel-resistor 2~9.
Connected across the line just ahead of resistor 219 is the RC network comprising resistor 215 and capacitor 217.
Back-to-back Zener dio~es 209 are connected to the high side of capacitor 217 and, through resistor 207, to the gate ter-minal of triac 204. The main terminals of a triac 205 are connected between the high side of capacitor 217 and the gate of triac 204. The gate of triac 205 is connected to the junction between resistor 207 and back-to-back Zener diodes 209. Gate resistor 211 to triac 204 completes the network.
In operation, crow bar power device 204 is turned on only when the voltage across capacitor 217 exceeds the Zener voltage across Zener diodes 209~ Transients occurriny wllen triac 230, which may be functionally characterized as a soft-start/regulation circuit po~er device, is off, are not applied to the ac input of rectifier bridge 68. ~ence, capacitor 217 is not charged up and the crow bar is not activated. When triac 230 is on and a transient occurs that is large enougll to endanger the electronic ballast or ballasts connected to the dc output, the transients remaining after treatment by transient suppression circuit 63 are applied to the ac side of rectifier bridge 68 and to RC network comprising resistor 215 and capacitor 217. If the voltage on capacitor 217 is great enough, triac 204 is triggered as a result of back-to-back Zener diode 209 triggering triac 205. Since the transient can be either positive or negative, one or the other of the two Zener diodes will conduct to initiate the triggering action.
It should be also noted that resistor 215 and capacitor 217, in combination with capacitor G2b, form a ~nubber for ;~
13i.1~i ~ ~r~
in-line triac 230.
While particular embodiments of the invention have been shown and described, it will be understood that the invention is not limited thereto, since modifications may be made and will become apparent to those skilled in the art. ~or exam-ple, the operation of a single lamp module as illustrated in Figs. 1 and 5 has been described. It is understood that the preferred embodiment will include a plurality of such modules connected to a common power supply, such as illustrated in Figs. 6 and 7.
Furthermore, it may be recognized that the dc power supply which has been described is a preferred embodiment with somewhat elaborate features for ensuring highly stable dc output to the high frequency operating circuit for the lamp. Such an elaborate supply may not be desirable for installation not having extremely important stability re-quirements.
Claims (17)
1. A circuit for operating a high frequency, gaseous-discharge lamp, comprising a ballast impedance connectable to the lamp, and an oscillator operating at a frequency above the acoustic resonances of the lamp connectable thereto, said oscillator providing the lamp with high power and high frequency current.
2. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 1, wherein the operating frequency of said oscillator is in the range between ap-proximately 60 kHz and 100 kHz.
3. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 1, and including regulating means connected to said oscillator to compensate for a variation in voltage levels applied thereto.
4. A circuit for operating a high frequency, gaseous-discharge lamp, comprising a push-pull, Class C oscillator having a resonant circuit including a high-Q coil connected to a first operating electrode of the lamp, said oscillator being connected to a power source, said resonant circuit establishing an operating frequency for said oscillator at a frequency above the acoustic resonant frequence of the lamp, a ballast impedance connected to a second operating electrode of the lamp, and said high-Q coil in said resonant circuit providing the lamp with high power and high frequency current.
5. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 4, wherein said resonant circuit establishes an operating frequency for said oscil-lator at a frequency in the range between approximately 60 kHz and 100 kHz.
6. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 4, wherein said oscillator includes a center-tapped transformer connected across said high-Q coil and alternate networks connected to opposite ends of said transformer, each of said networks comprising a base-driven triode transistor, the collector-emitter circuit being connected between the adjacent end of said transformer primary winding and ground, a low impedance drive circuit including an isolation winding of said transformer, and a fast-acting diode connecting the base of said tran-sistor to ground so as to prevent hard turn-off operation of said transistor, thereby enhancing fast turn-on operation thereof.
7. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 6, and including regulating means connected to said transformer and to said base-driven triode transistor for changing the conduction time of said transistor when the voltage applied to said transformer exceeds a predetermined value.
8. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 7, wherein said regulating means is connected to a base winding of said transformer, said drive circuit includes a capacitor charged by the voltage on said base winding, the discharge thereof determining the conduction of said transistor, and said regulating means includes semiconductor means connected to said capacitor for controlling the discharge of said capacitor and thereby the con-duction time of said transistor.
9. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 6, wherein each of said os-cillator networks includes a slow-acting diode connected in series with the base of said transistor having a recovery time longer than the turn-off time of said transistor to provide fast reverse current drain therefore, thereby speed-ing turn-off of said transistor.
10. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 7, wherein said transformer includes a first and second tap connection equal distance from said center tap toward respective ends of said trans-former for connecting said oscillator to provide higher voltage to the lamp than with end connections.
11. In a circuit for operating a high frequency, gaseous-discharge lamp including a ballast connected to receive a DC
source voltage and a base-driven triode transistor for supplying at least a portion of the high frequency current to the ballast, the improvement comprising regulating means connected to the ballast and the base-driven triode transis-tor for changing the conduction time of the transistor when the voltage applied to the ballast exceeds a predetermined value.
source voltage and a base-driven triode transistor for supplying at least a portion of the high frequency current to the ballast, the improvement comprising regulating means connected to the ballast and the base-driven triode transis-tor for changing the conduction time of the transistor when the voltage applied to the ballast exceeds a predetermined value.
12. A high frequency, gaseous-discharge lamp operating cir-cuit as set forth in claim 11, wherein said regulating means is connected to a base winding of the ballast, a drive circuit connected to said base-driven triode transistor including a capacitor charged by the voltage on said base winding, the discharge thereof determining the conduction of said transistor, and said regulating means including semiconductor means con-nected to said capacitor for controlling the dis-charge of said capacitor and thereby the conduc-tion time of said transistor.
13. A high frequency, gaseous-discharge lamp operating circuit as set forth in claim 12, and including resistance means for sensing the presence of current applied to said ballast, and photoelectric means connected to said resistance means and said semiconductor means, the voltage on said resistance means determining the conduction of the controlling semiconductor means and the discharge of said capacitor and thereby the conduction of said base-driven triode transistor.
14. A circuit for energizing a gaseous discharge lamp, at high frequency, the lamp characterized by one or more acoustic resonant frequencies at which acoustic resonance occurs to thereby disrupt energization to the lamp and produce visually detectable disturbances in the light emitted from the lamp, said circuit comprising a ballast impedance connectable to the lamp; and an oscillator circuit for providing the lamp with high power and current at a frequency higher than said more than one acoustic resonant frequencies.
15. The energizing circuit according to claim 14 wherein said oscillator circuit includes a center-tapped transformer having its secondary terminals coupled to said ballast impedance and to said lamp.
16. A circuit for operating a high frequency, gaseous discharge lamp, comprising a ballast impedance connectable to the lamp, and an oscillator operating at a substantially constant frequency above the acoustic resonance frequency of the lamp connectable thereto, said oscillator providing the lamp with high power frequency current.
17. The circuit for energizing a gaseous discharge lamp according to claim 14, wherein said oscillator circuit includes means for generating said higher frequency at a substantially constant higher frequency during operation of the lamp.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA353,200A CA1112730A (en) | 1976-02-02 | 1980-06-02 | High frequency circuit for operating a high-intensity, gaseous discharge lamp |
| CA380,861A CA1128995A (en) | 1976-02-02 | 1981-06-29 | High frequency circuit for operating a high-intensity, gaseous discharge lamp |
| CA380,859A CA1128991A (en) | 1976-02-02 | 1981-06-29 | High frequency circuit for operating a high-intensity, gaseous discharge lamp |
| CA380,860A CA1128992A (en) | 1976-02-02 | 1981-06-29 | High frequency circuit for operating a high-intensity, gaseous discharge lamp |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65492676A | 1976-02-02 | 1976-02-02 | |
| US654,926 | 1976-02-02 | ||
| US70022276A | 1976-07-26 | 1976-07-26 | |
| US700,222 | 1976-07-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116690A true CA1116690A (en) | 1982-01-19 |
Family
ID=27096847
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000266718A Expired CA1116690A (en) | 1976-02-02 | 1976-11-26 | High frequency circuit for operating a high-intensity, gaseous discharge lamp |
Country Status (8)
| Country | Link |
|---|---|
| AU (2) | AU502711B2 (en) |
| BR (1) | BR7700007A (en) |
| CA (1) | CA1116690A (en) |
| DE (1) | DE2704311A1 (en) |
| FR (1) | FR2345886A1 (en) |
| GB (1) | GB1577520A (en) |
| IT (1) | IT1077475B (en) |
| MX (1) | MX142946A (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4170746A (en) * | 1977-12-27 | 1979-10-09 | General Electric Company | High frequency operation of miniature metal vapor discharge lamps |
| US4151445A (en) * | 1978-02-15 | 1979-04-24 | General Electric Company | Instant light lamp control circuit |
| FR2500251A1 (en) * | 1981-02-13 | 1982-08-20 | Accumulateurs Fixes | DEVICE FOR SUPPORTING FEEDBACK OF A FLUORESCENT LUMINAIRE |
| US4705991A (en) * | 1981-06-04 | 1987-11-10 | U.S. Philips Corporation | Method of operating a high-pressure metal vapor discharge lamp and circuit arrangement for carrying out this method |
| EP0107019B1 (en) * | 1982-09-24 | 1989-05-17 | Jürgen Rensch | Lamp, in particular a signalling lamp for water-borne vehicles |
| GB2172451B (en) * | 1985-02-07 | 1989-06-14 | El Co Villamos Keszulekek Es S | Circuit system for igniting and lighting a high-pressure discharge lamp particulary a sodium vapour lamp |
| GB2197760A (en) * | 1986-10-31 | 1988-05-25 | Fano Int Ltd | Emergency lighting unit |
| GB8711131D0 (en) * | 1987-05-12 | 1987-06-17 | Emi Plc Thorn | Power supply |
| US4935673A (en) * | 1987-07-08 | 1990-06-19 | Led Corporation | Variable impedance electronic ballast for a gas discharge device |
| GB2360150B (en) * | 2000-03-10 | 2002-02-20 | Microlights Ltd | Improvements in and relating to high intensity discharge lighting |
| ITNA20100024A1 (en) * | 2010-05-11 | 2011-11-12 | Red Electronics S N C Di Mares Ca Aniello & C | ELECTRONIC DEVICE FOR PHASE PARTIALIZATION CONTROL FOR OHMICO-INDUCTIVE LOADS WITH NETWORK SWITCHING SYSTEM - INTEGRATED LOAD. |
| CN114567943B (en) * | 2022-02-10 | 2023-10-31 | 浙江大华技术股份有限公司 | Light supplementing lamp |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1401628A (en) * | 1971-11-18 | 1975-07-16 | Victor Products Ltd | Electric power supply systems |
| US3753076A (en) * | 1972-04-27 | 1973-08-14 | Lighting Systems Inc | Inverter circuit and switching means |
| GB1506390A (en) * | 1974-04-27 | 1978-04-05 | Ew Controls | Electric lighting systems |
-
1976
- 1976-11-26 CA CA000266718A patent/CA1116690A/en not_active Expired
- 1976-12-15 AU AU20565/76A patent/AU502711B2/en not_active Expired
- 1976-12-16 MX MX167458A patent/MX142946A/en unknown
-
1977
- 1977-01-03 BR BR7700007A patent/BR7700007A/en unknown
- 1977-01-07 FR FR7700367A patent/FR2345886A1/en active Granted
- 1977-01-12 IT IT47597/77A patent/IT1077475B/en active
- 1977-02-01 GB GB4118/77A patent/GB1577520A/en not_active Expired
- 1977-02-02 DE DE19772704311 patent/DE2704311A1/en not_active Withdrawn
-
1978
- 1978-11-07 AU AU41421/78A patent/AU512489B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU502711B2 (en) | 1979-08-02 |
| AU512489B2 (en) | 1980-10-16 |
| AU2056576A (en) | 1978-06-22 |
| MX142946A (en) | 1981-01-20 |
| DE2704311A1 (en) | 1977-08-04 |
| FR2345886B1 (en) | 1981-07-31 |
| FR2345886A1 (en) | 1977-10-21 |
| IT1077475B (en) | 1985-05-04 |
| GB1577520A (en) | 1980-10-22 |
| BR7700007A (en) | 1977-09-06 |
| AU4142178A (en) | 1979-04-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |