CA1129483A - Converter for supplying discharge lamps, and more generally arc lamps and its application to projectors for such lamps - Google Patents
Converter for supplying discharge lamps, and more generally arc lamps and its application to projectors for such lampsInfo
- Publication number
- CA1129483A CA1129483A CA320,638A CA320638A CA1129483A CA 1129483 A CA1129483 A CA 1129483A CA 320638 A CA320638 A CA 320638A CA 1129483 A CA1129483 A CA 1129483A
- Authority
- CA
- Canada
- Prior art keywords
- converter
- voltage
- circuit
- lamps
- output
- 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
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
-
- 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
- H05B41/2885—Static converters especially adapted therefor; Control thereof
- H05B41/2886—Static converters especially adapted therefor; Control thereof comprising a controllable preconditioner, e.g. a booster
-
- 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
- H05B41/2887—Static converters especially adapted therefor; Control thereof characterised by a controllable bridge in the final stage
- H05B41/2888—Static converters especially adapted therefor; Control thereof characterised by a controllable bridge in the final stage the bridge being commutated at low frequency, e.g. 1kHz
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Circuit Arrangements For Discharge Lamps (AREA)
- Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE A converter for supplying discharge lamps, and more generally arc lamps from an ordinary voltage source. The converter comprises an imposed current distribution system formed by a chopper circuit whose input is connected to the output of a current rectifying circuit. The output of the chopper circuit is connected to the discharge tube through a switching circuit allowing the lamp to be supplied with alternating polarity. The converter allows the lamps to be relit when hot, eli-minates the stroboscopic effect, is insensitive to mains voltage and frequency variations, offers a smaller weight and volume than the conventional inductive ballast and lends itself to control of the light intensity.
Description
~lZ9483 The present invention relates to a converter for supplying lamps using discharge tubes, and more generally electric arc lamps, from an AC or DC voltage source. In the present text, the term "discharge lamps" refers to such lamps.
Besides being frequently used for town or street lighting, such discharge lamps find a special application in theatre, cinema, television or similar projectors, in which a faithful restitution of colours, continuous brightness and the possibility of controlling this latter are requirements of the first order. To satisfy these requirements, carbon arc lamps are used at present supplied from a DC voltage source with insertion of a resistive ballast which, besides the energy losses which it gives rise to, causes all the additional disadvantages associated with an arc in a free atmosphere (release of gases, wear of the carbons etc..) Discharge lamp projectors are also used supplied from the AC
mains voltage, with insertion of a ballast formed generally by an inductance capable of storing the excess energy when the voltage of the mains is greater than the arc voltage of the lamp in order to restore it when the mains voltage is low, or even with a reversal of polarity.
Now, it is known that the supply current variations have repercussions on the current delivered by the inductive ballast known at present, which causes a defect called stroboscopic effect, dangerous not only in the cinema and television but more generally for all lighting of live scenes, such as sports grounds, moving vehicles, workshops compri-sing rotary machines etc Moreover, the ballast inductance is heavy and cumbersome for it stores litt].e energy in relation to its mass and volume. It is also known that supply circuits of the above type do not allow the lighting intensity of the discharge lamp to be ad~usted, unless by operation Or power elements i.e. either ad~usting the supply voltage or swltching the turns of the ballast forming inductance, or by inserting an additional inductance.
It is to be noted furthermore that it is impossible to strike the discharge lamp having a series inductance ballast when the effective voltage of the network is 115V and that even mains of 220V is insufficient ~r ~129483 for some high arc voltage lamps. Furthermore, when the supply to a discharge lamp is voluntarily or accidentally cut off, it is impossible;
with a series ballast inductance, to cause the lamp to light up again without having let it cool down. The series inductance presents in fact, for the striking pulse frequency, a high impedance which makes then inoperative when hot, because of the high dielectric rigidity of the high pressure gases. The principal aim of the present invention is to eliminate these disadvantages by using a converter adapted to supply discharge lamps, from an ordinary voltage source, which is essentially characterized in that it comprises a converter which includes d.c.
voltage supply terminals, a chopping circuit which includes a chopping transistor arranged to be controlled by the output of an error amplifier which has one input connected to receive a reference current from a generator and another connected to the output of the signal amplifier.
The input of the signal amplifier is coupled to a series connected measuring shunt. The chopping circuit further includes a series connected conductive energy storage means, a parallel-connected capacitive energy storage means and a free-wheel diode. The chopping circuit is operable to receive at its input a d.c. voltage from the supply terminals while the chopping transistor is operable to successively switch the d.c.
voltage to an output of the chopping circuit via the inductlve and capacitive energy storage means. The converter also includes output terminals for connection to a discharge lamp and a switching clrcuit for applying the voltage at the output of the chopping circuit to the output terminals. The switching circuit is operable to successively alternate the polarity of the voltage at the output terminals. The inductive and capactive energy storage means are arranged to store energy which is discharged through the discharge lamp upon reduction of the d.c. voltage.
Converter also includes means for varying the reference current in order to alter the brightness of the discharge lamp.
With this arrangement, and as will be seen more clearly further on, the brightness emitted can be controlled because of the regulated current supply.
~Z9483 -2a-Moreover, the heavy ballast inductance is done away with, energy being stored in a capacitive form. For this reason, the power consumption and the light emitted by the lamp are independent of the frequency and, over a large range, of the mains voltage; supply from a DC voltage network is also possible.
Finally, with the switching circuit, the polarity at the electrodes of the lamp can be reversed at a higher frequency than that of the network, which reduces the scintillation and stroboscopic effects.
Advantageously, the chopper circuit comprises a chopper transistor driven by a current controlled system. The information is collected by a current sensor such as a measuring shunt placed in series, followed by an amplifier whose output drives one of the inputs of an error amplifier whose second input receives the reference value.
It will be readily understood that with this arrangement it is possible to regulate the brightness of the lamp by controlling the reference value of the current generator.
The rectifier circuit disposed at the input has preferably two filtering capacitors driven through a llO/220V switch, which allows ~, 112~483 the lamp to operate on llOV A.C., or 220V A.C. or 230V D.C.
As a variation, the input to the chopper circuit is connected to a low voltage DC source, such as an accumulator battery with few elements, said chopper circuit being a voltage booster circuit.
An embodiment of the present invention is described below by way of example with reference to the accompanying drawings in which:
Figure 1 is a diagram of a converter for supplying discharge tubes, in accordance with the present invention;
Figure 2 is a diagram of another embodiment of the converter of Figure l;
Figure 3 shows schematically, in median section, one of the possible applications of a converter according to the invention in a projector of the discharge type, along line III-III of Figure 4;
Figure 4 is a partial section of the projector along line IV-IV of Figure 3.
The converter shown in Figure 1 comprises a chopper circuit connected to the AC or DC supply source through a rectifier bridge D6, D7, D8, D9, two filtering capacitors Cl and C2, a current limiting thermistor Th disposed in series and a 110/220V switch I.
The chopper circuit comprises a chopper transistor T5 of the NPN type whose emitter is connected to the negative pole of the rectifier bridge and whose collector is connected to the anode of a retrieval diode D5, the cathode of this latter being connected to the positive pole of the rectifier bridge.
The chopper circult also comprises a serles smoothing induc-tance S and a parallel storage capacltor C. The chopper transistor is controlled by the current, the information therefor being collected by a series shunt R6. This inEormation is then amplified in an amplifier Al up to the level required for comparison in an error amplifler A2 whose second input Io receivas the reference value of the current generator.
This reference value is controllable, locally or remotely, to allow adjust-ment of the brightness.
In accordance with the technique usually used in chopper amplifiers, the result of the subtraction between the reference signal i.... ~
~lZ9483 I and the signal coming from shunt R6 after amplification is converted into an all or nothing signal with cyclical variation; a possible increase of the reference signal I , for example, generates an increase of the cyclical ratio so as to extend the conducting period of the chopper transistor T5 to provide the extra consumption required by the lamp.
The outputs of amplifier A2, also called control modulator of the cyclical ratio, are connected between the base and the emitter of the chopper transistor T5.
The output of this imposed current distribution circuit is connected to the discharge lamp L through a switching circuit comprising two pairs of transistor Tl, T2 and T3, T4 of the NPN type, each of which is shunted by a diode Dl, D2, D3 and D4 respectively. The disabling of the transistors and therefore the reversal of polarity of the lamp is controlled by a signal generator with galvanic insulation G driving each transistor between base and emitter. Resistors Rl, R2, R3 and R4 are each respectively connected between the base and the emitter of the corresponding transistor.
Of course, each transistor-diode-resistor group may be a commercially available integrated circuit.
The operation of each of the circuits forming the converter in accordance with the invention is conventional and will therefore not be explained in detail here.
It is simply to be noted that the cyclical ratio control modulator A2 controls chopper transistor T5 with high Erequency rect-angular signals, e.g. 25 kHz, which takes advantage of the speed of switching which this transistor allows so as to reduce the energy which smoothing inductance S must store. So as to reduce losses, the amplifier provides a square pulse signal which controls either the total enabling of the transistor, or its disabling, this latter being achieved by application of a negative polarity to the base so as to promote rapid disabling. The cyclical ratio of the square wave signal is then auto-matically controlled with respect to the value of the voltage which the lamp needs for its operation:
~`
llZ9483 - just before striking, since the current actually consumed is zero, the converter behaves like a high voltage generator with low internal resistance. The cyclical ratio is then fixed at a value defined by the maximum imposed voltage reference;
- at the moment of striking, the high voltage pulses emitted by striker A are directed to lamp L without meeting any obstacle when passing through the output of the converter; they are even reinforced by the extra voltage which this latter supplies;
- once the arc is struck, the cyclical ratio adapts itself to the fluctuations of the arc voltage with respect to the temperature so as to maintain the output current practically equal to the reference current;
- if the discharge lamp is extinguished, either by design or by accident, relighting is instantaneously possible since the converter has gone over from imposed current operation to imposed voltage operation.
The protection against overloads when switching on is provided on the one hand by thermistor Th which reduces the charge overvoltage of the filtering capacitors Cl and C2 and, on the other hand, by a starting up sequence which controls the rise of the cyclical ratio controlling the chopper transistor T5, so as to charge progressively capacitor C.
In a variation of the present invention described in Figure 2, the chopper system placed at the input couples together the transistor T5, diode D5 and smoothing inductance S according to another arrangement capable of increasing the source voltage lnstead of lowering it. This arrangement allows operation from an accumulator battery havin~ a small number of elements.
It follows then finally that the converter of the invention:
- allows the light intensity to be controlled according to the reference value Io acting on amplifier A2;
- abolishes scintillation and stroboscopic effects because of the use of high switching frequencies and rectangular current waves;
- does not use any heavy or cumbersome inductance;
l~Z9483 - allows instantaneous relighting of the lamp when cold or hot owi~g to the low internal resistance characteristic which its output offers in the case of very low power;
- is adaptable to the distribution networks of all industrial frequencies, as well as to DC voltage sources, even if the voltage distributed is less than the arc voltage.
The converter which has just been described may be adapted to any type of electric arc lamp, and particularly be applied to a discharge lamp projector for forming an integrated converter projector, this application being shown in Figures 3 and 4.
This projector comprises an optical chamber 1 which has on its front face a FRESNEL lens 2, on its rear face a spherical mirror 3 and inside a dishcarge lamp 4 whose position may be adjusted by means of a mobile apparatus 5 carried by slides 6 and whose position is controlled by focusing screws 7 connected to a knurled knob 6.
The base 9 of the projector supports the striking device 11 and the converter 12. Converter 12 is supplied by a lead 13 and it is connected to block 11 which is itself electrically connected to discharge lamp 4.
In conformity with the application in view, an antithermic separating wall 14 is placed between lamp 4 and base 9. Separating wall 14 is constructed for example from asbestos or a good heat resisting material such as agglomerated glass fibres, the two faces of this plate being metallized, e.g. with an aluminum layer, to avoid transmission of the heat flow coming from lamp 4 towards converter 12. Moreover, the walls of housing 15 contalning sub-assemblies 11 and 12 are provided with holes 16 on the front and back faces, at the lower part thereof, and other holes 17 are provided in the longitudina] faces at the upper part thereof.
There can thus be created by natural convection in the lower housing 15 a current of cooling air which cools sub-assemblies 11 and 12 and which also cools down the antithermic wall 14. Of course, the optical chamber 1 is also provided with a convection cooling device comprising holes 18, 19, 20 according to an arrangement known per se.
~lZ9483 The lower housing 15 contains also a potentiometric block 21 controlled by a knob 22 which allows the reference signal I determining the light intensity of lamp 4 to be controlled manually, as described with reference to Figure 3.
The reference signal I may be also remotely generated by means of a specialized connection which may be associated or not with lead 13. In this case, the potentiometric block 21 is made inoperative, the brightness control being effected from a central desk.
With the convection system provided for the electronic stages and with the antithermic separating wall 13, it is thus possible to construct a pro~ector in which all the electrical elements providing the supply for the discharge lamp and possibly the adjustment of its light intensity are integrated in the body of the projector.
~,
Besides being frequently used for town or street lighting, such discharge lamps find a special application in theatre, cinema, television or similar projectors, in which a faithful restitution of colours, continuous brightness and the possibility of controlling this latter are requirements of the first order. To satisfy these requirements, carbon arc lamps are used at present supplied from a DC voltage source with insertion of a resistive ballast which, besides the energy losses which it gives rise to, causes all the additional disadvantages associated with an arc in a free atmosphere (release of gases, wear of the carbons etc..) Discharge lamp projectors are also used supplied from the AC
mains voltage, with insertion of a ballast formed generally by an inductance capable of storing the excess energy when the voltage of the mains is greater than the arc voltage of the lamp in order to restore it when the mains voltage is low, or even with a reversal of polarity.
Now, it is known that the supply current variations have repercussions on the current delivered by the inductive ballast known at present, which causes a defect called stroboscopic effect, dangerous not only in the cinema and television but more generally for all lighting of live scenes, such as sports grounds, moving vehicles, workshops compri-sing rotary machines etc Moreover, the ballast inductance is heavy and cumbersome for it stores litt].e energy in relation to its mass and volume. It is also known that supply circuits of the above type do not allow the lighting intensity of the discharge lamp to be ad~usted, unless by operation Or power elements i.e. either ad~usting the supply voltage or swltching the turns of the ballast forming inductance, or by inserting an additional inductance.
It is to be noted furthermore that it is impossible to strike the discharge lamp having a series inductance ballast when the effective voltage of the network is 115V and that even mains of 220V is insufficient ~r ~129483 for some high arc voltage lamps. Furthermore, when the supply to a discharge lamp is voluntarily or accidentally cut off, it is impossible;
with a series ballast inductance, to cause the lamp to light up again without having let it cool down. The series inductance presents in fact, for the striking pulse frequency, a high impedance which makes then inoperative when hot, because of the high dielectric rigidity of the high pressure gases. The principal aim of the present invention is to eliminate these disadvantages by using a converter adapted to supply discharge lamps, from an ordinary voltage source, which is essentially characterized in that it comprises a converter which includes d.c.
voltage supply terminals, a chopping circuit which includes a chopping transistor arranged to be controlled by the output of an error amplifier which has one input connected to receive a reference current from a generator and another connected to the output of the signal amplifier.
The input of the signal amplifier is coupled to a series connected measuring shunt. The chopping circuit further includes a series connected conductive energy storage means, a parallel-connected capacitive energy storage means and a free-wheel diode. The chopping circuit is operable to receive at its input a d.c. voltage from the supply terminals while the chopping transistor is operable to successively switch the d.c.
voltage to an output of the chopping circuit via the inductlve and capacitive energy storage means. The converter also includes output terminals for connection to a discharge lamp and a switching clrcuit for applying the voltage at the output of the chopping circuit to the output terminals. The switching circuit is operable to successively alternate the polarity of the voltage at the output terminals. The inductive and capactive energy storage means are arranged to store energy which is discharged through the discharge lamp upon reduction of the d.c. voltage.
Converter also includes means for varying the reference current in order to alter the brightness of the discharge lamp.
With this arrangement, and as will be seen more clearly further on, the brightness emitted can be controlled because of the regulated current supply.
~Z9483 -2a-Moreover, the heavy ballast inductance is done away with, energy being stored in a capacitive form. For this reason, the power consumption and the light emitted by the lamp are independent of the frequency and, over a large range, of the mains voltage; supply from a DC voltage network is also possible.
Finally, with the switching circuit, the polarity at the electrodes of the lamp can be reversed at a higher frequency than that of the network, which reduces the scintillation and stroboscopic effects.
Advantageously, the chopper circuit comprises a chopper transistor driven by a current controlled system. The information is collected by a current sensor such as a measuring shunt placed in series, followed by an amplifier whose output drives one of the inputs of an error amplifier whose second input receives the reference value.
It will be readily understood that with this arrangement it is possible to regulate the brightness of the lamp by controlling the reference value of the current generator.
The rectifier circuit disposed at the input has preferably two filtering capacitors driven through a llO/220V switch, which allows ~, 112~483 the lamp to operate on llOV A.C., or 220V A.C. or 230V D.C.
As a variation, the input to the chopper circuit is connected to a low voltage DC source, such as an accumulator battery with few elements, said chopper circuit being a voltage booster circuit.
An embodiment of the present invention is described below by way of example with reference to the accompanying drawings in which:
Figure 1 is a diagram of a converter for supplying discharge tubes, in accordance with the present invention;
Figure 2 is a diagram of another embodiment of the converter of Figure l;
Figure 3 shows schematically, in median section, one of the possible applications of a converter according to the invention in a projector of the discharge type, along line III-III of Figure 4;
Figure 4 is a partial section of the projector along line IV-IV of Figure 3.
The converter shown in Figure 1 comprises a chopper circuit connected to the AC or DC supply source through a rectifier bridge D6, D7, D8, D9, two filtering capacitors Cl and C2, a current limiting thermistor Th disposed in series and a 110/220V switch I.
The chopper circuit comprises a chopper transistor T5 of the NPN type whose emitter is connected to the negative pole of the rectifier bridge and whose collector is connected to the anode of a retrieval diode D5, the cathode of this latter being connected to the positive pole of the rectifier bridge.
The chopper circult also comprises a serles smoothing induc-tance S and a parallel storage capacltor C. The chopper transistor is controlled by the current, the information therefor being collected by a series shunt R6. This inEormation is then amplified in an amplifier Al up to the level required for comparison in an error amplifler A2 whose second input Io receivas the reference value of the current generator.
This reference value is controllable, locally or remotely, to allow adjust-ment of the brightness.
In accordance with the technique usually used in chopper amplifiers, the result of the subtraction between the reference signal i.... ~
~lZ9483 I and the signal coming from shunt R6 after amplification is converted into an all or nothing signal with cyclical variation; a possible increase of the reference signal I , for example, generates an increase of the cyclical ratio so as to extend the conducting period of the chopper transistor T5 to provide the extra consumption required by the lamp.
The outputs of amplifier A2, also called control modulator of the cyclical ratio, are connected between the base and the emitter of the chopper transistor T5.
The output of this imposed current distribution circuit is connected to the discharge lamp L through a switching circuit comprising two pairs of transistor Tl, T2 and T3, T4 of the NPN type, each of which is shunted by a diode Dl, D2, D3 and D4 respectively. The disabling of the transistors and therefore the reversal of polarity of the lamp is controlled by a signal generator with galvanic insulation G driving each transistor between base and emitter. Resistors Rl, R2, R3 and R4 are each respectively connected between the base and the emitter of the corresponding transistor.
Of course, each transistor-diode-resistor group may be a commercially available integrated circuit.
The operation of each of the circuits forming the converter in accordance with the invention is conventional and will therefore not be explained in detail here.
It is simply to be noted that the cyclical ratio control modulator A2 controls chopper transistor T5 with high Erequency rect-angular signals, e.g. 25 kHz, which takes advantage of the speed of switching which this transistor allows so as to reduce the energy which smoothing inductance S must store. So as to reduce losses, the amplifier provides a square pulse signal which controls either the total enabling of the transistor, or its disabling, this latter being achieved by application of a negative polarity to the base so as to promote rapid disabling. The cyclical ratio of the square wave signal is then auto-matically controlled with respect to the value of the voltage which the lamp needs for its operation:
~`
llZ9483 - just before striking, since the current actually consumed is zero, the converter behaves like a high voltage generator with low internal resistance. The cyclical ratio is then fixed at a value defined by the maximum imposed voltage reference;
- at the moment of striking, the high voltage pulses emitted by striker A are directed to lamp L without meeting any obstacle when passing through the output of the converter; they are even reinforced by the extra voltage which this latter supplies;
- once the arc is struck, the cyclical ratio adapts itself to the fluctuations of the arc voltage with respect to the temperature so as to maintain the output current practically equal to the reference current;
- if the discharge lamp is extinguished, either by design or by accident, relighting is instantaneously possible since the converter has gone over from imposed current operation to imposed voltage operation.
The protection against overloads when switching on is provided on the one hand by thermistor Th which reduces the charge overvoltage of the filtering capacitors Cl and C2 and, on the other hand, by a starting up sequence which controls the rise of the cyclical ratio controlling the chopper transistor T5, so as to charge progressively capacitor C.
In a variation of the present invention described in Figure 2, the chopper system placed at the input couples together the transistor T5, diode D5 and smoothing inductance S according to another arrangement capable of increasing the source voltage lnstead of lowering it. This arrangement allows operation from an accumulator battery havin~ a small number of elements.
It follows then finally that the converter of the invention:
- allows the light intensity to be controlled according to the reference value Io acting on amplifier A2;
- abolishes scintillation and stroboscopic effects because of the use of high switching frequencies and rectangular current waves;
- does not use any heavy or cumbersome inductance;
l~Z9483 - allows instantaneous relighting of the lamp when cold or hot owi~g to the low internal resistance characteristic which its output offers in the case of very low power;
- is adaptable to the distribution networks of all industrial frequencies, as well as to DC voltage sources, even if the voltage distributed is less than the arc voltage.
The converter which has just been described may be adapted to any type of electric arc lamp, and particularly be applied to a discharge lamp projector for forming an integrated converter projector, this application being shown in Figures 3 and 4.
This projector comprises an optical chamber 1 which has on its front face a FRESNEL lens 2, on its rear face a spherical mirror 3 and inside a dishcarge lamp 4 whose position may be adjusted by means of a mobile apparatus 5 carried by slides 6 and whose position is controlled by focusing screws 7 connected to a knurled knob 6.
The base 9 of the projector supports the striking device 11 and the converter 12. Converter 12 is supplied by a lead 13 and it is connected to block 11 which is itself electrically connected to discharge lamp 4.
In conformity with the application in view, an antithermic separating wall 14 is placed between lamp 4 and base 9. Separating wall 14 is constructed for example from asbestos or a good heat resisting material such as agglomerated glass fibres, the two faces of this plate being metallized, e.g. with an aluminum layer, to avoid transmission of the heat flow coming from lamp 4 towards converter 12. Moreover, the walls of housing 15 contalning sub-assemblies 11 and 12 are provided with holes 16 on the front and back faces, at the lower part thereof, and other holes 17 are provided in the longitudina] faces at the upper part thereof.
There can thus be created by natural convection in the lower housing 15 a current of cooling air which cools sub-assemblies 11 and 12 and which also cools down the antithermic wall 14. Of course, the optical chamber 1 is also provided with a convection cooling device comprising holes 18, 19, 20 according to an arrangement known per se.
~lZ9483 The lower housing 15 contains also a potentiometric block 21 controlled by a knob 22 which allows the reference signal I determining the light intensity of lamp 4 to be controlled manually, as described with reference to Figure 3.
The reference signal I may be also remotely generated by means of a specialized connection which may be associated or not with lead 13. In this case, the potentiometric block 21 is made inoperative, the brightness control being effected from a central desk.
With the convection system provided for the electronic stages and with the antithermic separating wall 13, it is thus possible to construct a pro~ector in which all the electrical elements providing the supply for the discharge lamp and possibly the adjustment of its light intensity are integrated in the body of the projector.
~,
Claims (7)
1. A converter for supplying a discharge lamp from a voltage source, the converter comprising:
d.c. voltage supply terminals;
a chopping circuit comprising a chopping transistor arranged to be controlled by the output of an error amplifier having one input connected to receive a reference current from a generator and another input connected to the output of a signal amplifier the input of which is coupled to a series-connected measuring shunt, the chopping circuit further comprising a series-connected inductive energy storage means, a parallel-connected capacitive energy storage means and a free-wheel diode, the chopping circuit being operable to receive at an input thereof a d.c. voltage from said supply terminals, and the chopping transistor being operable successively to switch the d.c. voltage to an output of the chopping circuit via said inductive and capacitive energy storage means;
output terminals for connection to a discharge lamp;
a switching circuit for applying the voltage at the output of the chopping circuit to the output terminals, the switching circuit being operable successively to alternate the polarity of the voltage at the output terminals;
the inductive and capacitive energy storage means being arranged to store energy which is discharged through the discharge lamp upon a reduction of said d.c. voltage; and means for varying said reference current in order to alter the brightness of the discharge lamp.
d.c. voltage supply terminals;
a chopping circuit comprising a chopping transistor arranged to be controlled by the output of an error amplifier having one input connected to receive a reference current from a generator and another input connected to the output of a signal amplifier the input of which is coupled to a series-connected measuring shunt, the chopping circuit further comprising a series-connected inductive energy storage means, a parallel-connected capacitive energy storage means and a free-wheel diode, the chopping circuit being operable to receive at an input thereof a d.c. voltage from said supply terminals, and the chopping transistor being operable successively to switch the d.c. voltage to an output of the chopping circuit via said inductive and capacitive energy storage means;
output terminals for connection to a discharge lamp;
a switching circuit for applying the voltage at the output of the chopping circuit to the output terminals, the switching circuit being operable successively to alternate the polarity of the voltage at the output terminals;
the inductive and capacitive energy storage means being arranged to store energy which is discharged through the discharge lamp upon a reduction of said d.c. voltage; and means for varying said reference current in order to alter the brightness of the discharge lamp.
2. A converter as claimed in claim 1, including a rectifying circuit for connection to an a.c. voltage source, the rectifying circuit being arranged to provide a rectified voltage at said d.c. voltage supply terminals.
3. A converter as claimed in claim 2, including a 110/220 V
switch by means of which an operator can selectively adapt the rectifying circuit for operation with either a 110 volt a.c. source or a 220 volt a.c. or d.c. source.
switch by means of which an operator can selectively adapt the rectifying circuit for operation with either a 110 volt a.c. source or a 220 volt a.c. or d.c. source.
4. A converter as claimed in claims 1, 2 or 3, wherein the converter is adapted for operation with a d.c. low-voltage source, the chopping circuit being a voltage-increasing circuit.
5. A lamp device comprising a discharge lamp and a converter according to claim 1, wherein the converter is mounted in a chamber of a housing of the device.
6. A lamp device as claimed in claim 5, wherein the chamber is disposed below an optical chamber containing the lamp and is separated therefrom by an anti-heat screen.
7. A lamp device as claimed in claim 5 or 6, wherein convec-tion cooling means are disposed in the chamber containing the converter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7803386A FR2416617A1 (en) | 1978-02-07 | 1978-02-07 | CONVERTER FOR THE POWER SUPPLY OF DISCHARGE LAMPS, AND MORE GENERALLY OF ARC LAMPS, AND ITS APPLICATION TO PROJECTORS FOR SUCH LAMPS |
| FR78.03386 | 1978-02-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129483A true CA1129483A (en) | 1982-08-10 |
Family
ID=9204296
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA320,638A Expired CA1129483A (en) | 1978-02-07 | 1979-01-31 | Converter for supplying discharge lamps, and more generally arc lamps and its application to projectors for such lamps |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS54120974A (en) |
| AU (1) | AU531318B2 (en) |
| BE (1) | BE873930A (en) |
| BR (1) | BR7900773A (en) |
| CA (1) | CA1129483A (en) |
| DE (1) | DE2904393A1 (en) |
| ES (1) | ES477391A1 (en) |
| FR (1) | FR2416617A1 (en) |
| GB (1) | GB2016222B (en) |
| IT (1) | IT1118335B (en) |
| LU (1) | LU80881A1 (en) |
| NL (1) | NL7900941A (en) |
Families Citing this family (31)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE441563B (en) * | 1980-04-09 | 1985-10-14 | Selfrid Gunnar Ohlund | CONTROL DEVICE FOR A CONVERSION POWER VALVE FOR OPERATION OF A GAS EMISSION PIPE FROM A DIRECTION SHELL |
| NZ201203A (en) * | 1981-07-28 | 1985-08-30 | Lee Electric Lighting | Arc lamp supply:fet bridge inverter powered by constant current source |
| FR2514585A1 (en) * | 1981-10-14 | 1983-04-15 | Signaux Entr Electriques | ELECTRONIC SUPPLY DEVICE ABSORBING ON THE ALTERNATIVE NETWORK SINUSOIDAL CURRENT PHASE WITH VOLTAGE |
| GB2117192B (en) * | 1982-02-26 | 1986-01-02 | Transtar Limited | Lamp control circuit |
| GB2120869A (en) * | 1982-05-04 | 1983-12-07 | Gen Electric | Controlling the output level of an electrical power supply |
| JPH0691750B2 (en) * | 1983-01-14 | 1994-11-14 | 松下電工株式会社 | Inverter device |
| JPS60134776A (en) * | 1983-12-23 | 1985-07-18 | Matsushita Electric Works Ltd | Power source |
| JPS60180095A (en) * | 1984-02-27 | 1985-09-13 | 水野 道夫 | Power saving device for discharge lamp |
| JPS61110996A (en) * | 1984-11-05 | 1986-05-29 | 株式会社日立製作所 | High voltage discharge lamp lighting apparatus |
| DE3517297C1 (en) * | 1985-05-14 | 1986-07-24 | Trilux-Lenze Gmbh + Co Kg, 5760 Arnsberg | Ballast for discharge lamps |
| DE3608362A1 (en) * | 1985-05-14 | 1987-09-17 | Trilux Lenze Gmbh & Co Kg | Ballast for discharge lamps |
| DE3524681A1 (en) * | 1985-07-11 | 1987-01-22 | Trilux Lenze Gmbh & Co Kg | DIMMER SWITCH FOR AN ELECTRONIC FLUORESCENT LAMP CONTROLLER |
| DE3522569A1 (en) * | 1985-06-24 | 1987-01-02 | Metallgesellschaft Ag | ELECTRICITY POWER SUPPLY |
| US4734624A (en) * | 1985-07-25 | 1988-03-29 | Matsushita Electric Works, Ltd. | Discharge lamp driving circuit |
| DE3528838A1 (en) * | 1985-08-10 | 1987-02-12 | Diehl Gmbh & Co | IGNITION AND DIMMING CONTROL FOR A FLUORESCENT TUBE |
| DE3533548A1 (en) * | 1985-09-20 | 1987-04-02 | Trilux Lenze Gmbh & Co Kg | Fluorescent lamp ballast unit |
| NL8503475A (en) * | 1985-12-18 | 1987-07-16 | Oce Nederland Bv | CHARGING CIRCUIT FOR POWER CAPACITORS. |
| DE3607109C1 (en) * | 1986-03-05 | 1987-05-07 | Trilux Lenze Gmbh & Co Kg | Ballast for discharge lamps |
| DE3614708A1 (en) * | 1986-04-30 | 1987-11-19 | Schmidt Michael | CONTROL CIRCUIT FOR AN ARC LAMP |
| FR2601202B1 (en) * | 1986-07-01 | 1992-01-10 | Electricite De France | BUFFER SOURCE WITH STORAGE CAPACITOR FOR A DEVICE FOR PROTECTING AN INSTALLATION AGAINST BRIEF CUTTINGS AND VOLTAGE DROPS |
| GB2212995A (en) * | 1987-10-23 | 1989-08-02 | Rockwell International Corp | Fluorescent lamp dimmer |
| NL8800015A (en) * | 1988-01-06 | 1989-08-01 | Philips Nv | ELECTRICAL DEVICE FOR IGNITION AND POWERING A GAS DISCHARGE LAMP. |
| US4904907A (en) * | 1988-02-26 | 1990-02-27 | General Electric Company | Ballast circuit for metal halide lamp |
| FR2627911B1 (en) * | 1988-02-26 | 1990-08-10 | Electricite De France | METHOD AND DEVICE FOR SUPPLYING AN ELECTRICAL INSTALLATION AND ITS APPLICATION TO LIGHTING LAMPS |
| DE3829388A1 (en) * | 1988-08-30 | 1990-03-01 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | CIRCUIT ARRANGEMENT FOR OPERATING A LOAD |
| DE3925654A1 (en) * | 1989-08-03 | 1991-02-07 | Schmidt Michael | Control unit for discharge lamp(s) - has switches in series connected to DC circuit and diode in parallel in blocking direction |
| DE4039498B4 (en) * | 1990-07-13 | 2006-06-29 | Lutron Electronics Co., Inc. | Circuit and method for dimming gas discharge lamps |
| DE4141804C1 (en) * | 1991-12-18 | 1993-02-25 | Robert Bosch Gmbh, 7000 Stuttgart, De | |
| GB2269279A (en) * | 1992-08-01 | 1994-02-02 | Coolite Ltd | Fluorescent Tube Starting and Operating Circuit |
| DE4301184C2 (en) * | 1993-01-19 | 1997-12-18 | B & S Elektronische Geraete Gm | Control device for at least one discharge lamp |
| JP3802281B2 (en) * | 1999-06-21 | 2006-07-26 | 株式会社小糸製作所 | Discharge lamp lighting circuit |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2550550A1 (en) * | 1975-11-11 | 1977-05-12 | Gen Electric | Electronic ballast circuit for gas discharge lamp - has transistor switch, inductor energy store and static inverter |
-
1978
- 1978-02-07 FR FR7803386A patent/FR2416617A1/en active Granted
-
1979
- 1979-01-31 CA CA320,638A patent/CA1129483A/en not_active Expired
- 1979-02-01 ES ES477391A patent/ES477391A1/en not_active Expired
- 1979-02-05 BE BE0/193265A patent/BE873930A/en not_active IP Right Cessation
- 1979-02-05 LU LU80881A patent/LU80881A1/en unknown
- 1979-02-06 BR BR7900773A patent/BR7900773A/en unknown
- 1979-02-06 DE DE19792904393 patent/DE2904393A1/en not_active Withdrawn
- 1979-02-06 IT IT67253/79A patent/IT1118335B/en active
- 1979-02-06 NL NL7900941A patent/NL7900941A/en not_active Application Discontinuation
- 1979-02-06 AU AU43972/79A patent/AU531318B2/en not_active Ceased
- 1979-02-06 GB GB7904186A patent/GB2016222B/en not_active Expired
- 1979-02-07 JP JP1319779A patent/JPS54120974A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS54120974A (en) | 1979-09-19 |
| GB2016222B (en) | 1982-12-08 |
| GB2016222A (en) | 1979-09-19 |
| AU531318B2 (en) | 1983-08-18 |
| NL7900941A (en) | 1979-08-09 |
| ES477391A1 (en) | 1979-07-01 |
| LU80881A1 (en) | 1979-10-29 |
| BR7900773A (en) | 1979-08-28 |
| FR2416617B1 (en) | 1981-10-16 |
| IT1118335B (en) | 1986-02-24 |
| DE2904393A1 (en) | 1979-08-09 |
| IT7967253A0 (en) | 1979-02-06 |
| AU4397279A (en) | 1979-08-16 |
| FR2416617A1 (en) | 1979-08-31 |
| BE873930A (en) | 1979-08-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 19990810 |