GB2093644A - Apparatus for operating discharge lamps - Google Patents
Apparatus for operating discharge lamps Download PDFInfo
- Publication number
- GB2093644A GB2093644A GB8105425A GB8105425A GB2093644A GB 2093644 A GB2093644 A GB 2093644A GB 8105425 A GB8105425 A GB 8105425A GB 8105425 A GB8105425 A GB 8105425A GB 2093644 A GB2093644 A GB 2093644A
- Authority
- GB
- United Kingdom
- Prior art keywords
- voltage
- inverter
- rectifier
- discharge lamp
- lamp
- 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.)
- Withdrawn
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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
- H05B41/292—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
Landscapes
- Circuit Arrangements For Discharge Lamps (AREA)
Abstract
A low frequency AC voltage is rectified through a full-wave rectifier (2) to obtain a pulsating voltage, which is superimposed with an auxiliary voltage of a predetermined level provided from an auxiliary power source (6), and the resultant composite pulsating voltage is inverted at an inverter (3) to a high frequency voltage. The high frequency voltage thus obtained from the inverter (3) is used to operate a discharge lamp. Minimum value Vmin of the resultant voltage is set to be 1/3 to 4/5 of the maximum value Vmax of the resultant voltage. <IMAGE>
Description
SPECIFICATION
Apparatus for operating discharge lamps
This invention relates to apparatus for operating a discharge lamp with a pulsating voltage.
A discharge lamp may be operated using the 50 Hz or 60 Hz commercially available AC power source by full-wave rectifying the AC voltage, obtaining from the pulsating voltage thus obtained a high frequency voltage having the envelope of the voltage waveform of the pulsating voltage using an inverter and using the high frequency voltage as a lamp operating voltage. By this method, while the high frequency voltage is being applied, the discharge lamp can be continuously lit since the lamp energizing cycle period is shorter than the ion re-excitation period of the lamp. However, since the pulsating voltage is a low frequency wave having the frequency of 100
Hz or 1 20 Hz, for example, the high frequency voltage is zero at the time of the zero level of the low frequency voltage, and during this period the lamp is not lit.During this pause period of lamp, energy is consumed by the re-excitation of ions, so that the lamp efficiency or light emission efficiency is reduced that much. For example, it has been found that with a 250-watt mercury lamp the light emission efficiency obtainable with the high frequency voltage lamp operation system mentioned above is lower by 10% than that obtainable with a DC high frequency voltage lamp operation system.
In order to improve the light emission efficiency, it may be conceived to operate a dicharge lamp by coupling a full-wave rectified voltage (i.e., pulsating voltage) that is obtained from a commercial AC voltage to a smoothing circuit to obtain a DC voltage and driving an inverter with this DC voltage to obtain a DC high frequency voltage for use as the lamp operation voltage.
In this case, however, a capacitor of a large capacitance is required for the smoothing circuit and greatly reduces the power factor of the lamp operating circuit, and also it is undesired from the standpoint of reducing the size and cost.
An object of the invention is to provide apparatus for operating a discharge lamp, which can operate a discharge lamp with satisfactory lamp efficiency and circuit power factor.
According to the invention, the above objective is achieved by apparatus for operating a discharge lamp comprising rectifying means for rectifying a low frequency AC voltage to obtain a pulsating voltage, an inverter for inverting the pulsating voltage to a high frequency voltage and means for operating a discharge lamp according to the output of the inverter, in which an auxiliary power source for generating an auxiliary voltage and a switch circuit for adding the auxiliary voltage to the pulsating voltage to have a resultant voltage only while the pulsating voltage is lower than the auxiliary voltage are provided, minimum value Vmin of the resultant voltage and the maximum value Vmax of the resultant voltage being set to meet a condition 4/5 VmsxVmix1 /3may This invention can be more fully understood from the following detailed description when taken in conjuction with the accompanying drawings, in which:
Figure 1 is a circuit diagram showing an embodiment of the apparatus for operating discharge lamps according to the invention;
Figures 2A to 2D show waveform charts for illustrating the functions of the apparatus shown in Fig. 1;
Figures 3 to 6 and 7A to 7C are graphs illustrating the scope of the invention;
Figure 8 is a circuit diagram, partly in block form, showing a different embodiment of the invention; and
Figure 9 is a circuit diagram showing a specific circuit construction of a further embodiment of the invention.
Referring now to Fig. 1, designated at 1 is a low frequency AC power source, for instance a 50 Hz, 200 volt commercial power source. The output terminals of the AC power source 1 are connected to the AC input termints of a full-wave rectifier 2 formed by four diodes. The positive side Qutput terminal of the full-wave rectifier 2 is connected to a center tape 3-0 of the primary winding 3-2 of a transformer 3-1 in an inverter 3. A capacitor 3-3 is connected between the opposite terminals of the primary winding 3-2. Of these terminals, one is connected to the collector of a transistor 3-4, and the other to the collector of a transistor 3-5.The transitors 3-4 and 3-5 have their bases connected through respective resistors 3-6 and 3-7 to the positive output terminal of the full-wave rectifier 2 and their emitters commonly connected to one end of a choke coil 4, which has its other end connected to the negative output terminal of the full-wave rectifier 2.
The transformer 3-1 also includes a second primary winding 3-8 and a secondary winding 3-9. The second primary winding 3-8 has its one end connected to the base of the transistor 3-4 and other end connected to the base of the transistor 3-5. A discharge lamp 5 has its one electrode 5-1 connected to one end 3-10 of the secondary winding 3-9 and the other electrode 5-2 connected to the other end 3-11 of the secondary winding 3-9. The transformer 3-1 is of a leakage type having leakage inductance functioning as a current limiting component for the discharge lamp.
The output terminals of the AC power source 1 are connected to the opposite ends.
of the primary winding 6-2 of a step-down transformer 6-1 of an auxiliary DC power source 6. The secondary winding 6-3 of the transformer 6-1 are connected to AC input terminals of a full-wave rectifier 6-4 which is formed by four diodes. The pulsating voltage output terminals of the rectifier 6-4 are connected to the opposite terminals of a smooth
ing capacitor 6-5. The capacitor 6-5 has its
positive terminal connected to an anode electrode of a diode 6-5 the cathode electrode of which is connected to the positive output terminal of the full-wave rectifier 2. The negative terminal of the rectifier 6-4 is connected to the negative output terminal of the rectifier 2.
The operation of the circuit of Fig. 1 will now be described with reference to Figs. 2A to 2D. The 50 Hz AC voltage from the AC power source 1 has a peak-to-peak level V1, and the full-wave rectifier 2 full-wave rectifies this voltage to obtain a pulsating voltage of a peak level V"2 or Vmax as shown in 2A.
Meanwhile, the AC voltage V1 is stepped down through the transformer 6-1 to have a cirtain voltage, and this stepped down AC voltage is smoothed through the capacitor 6-5. Thus, a DC voltage of substantially V2 as shown in Fig. 2B is obtained across the capacitor 6-5.
This DC voltage V2, as will be described later, is set to be above at least one-third of the peak value Vmax of the pulsating voltage, so that the pulsating voltage is lower than V2 in the neighborhood of instants T1, T2 ..., at which the pulsating voltage is zero. Every time the pulsating voltage becomes lower than V2, the diode switch 6-6 is rendered conductive, so that DC voltage V2 is superimposed upon the pulsating voltage. The resultant voltage has a waveform as shown in Fig. 2C, and it is supplied to the inverter 3.
The inverter 3 generates a voltage output at a high frequency, for instance 100 KHz, and having the envelope of the input voltage waveform of Fig. 2C. When a voltage as shown in Fig. 2C, of the ilustrated polarity at T = 0, is induced across the primary winding 3-8, the transistor 3-4 becomes "off" while the transistor 3-5 becomes "on", so that current flows from the center tap 3-0 of the primary winding 3-2 into the transistor 3-5, thus providing the high frequency voltage half cycle of one polarity in the secondary winding 3-9 of the transformer 3-1. With this current from the center tap 3-0 to the transistor 3-5, the capacitor 3-3 is charged to the illustrated polarity, while the primary winding 3-8 is excited in the opposite direction to generate voltage of the opposite polarity to that illustrated.As a result, the transistor 3-4 is triggered while the transistor 3-5 is cut off, thus causing current to pass from the tape 3-0 into the transistor 3-4 to let the secondary winding 3-9 provide the high frequency voltage half cycle of the opposite polarity. The
capacitor 3-3 is thus charged to the opposite
polarity to that illustrated, and the voltage of the illustrated polarity is generated in the
primary winding 3-8. As the transistors 3-4
and 3-5 are alternately turned on and off, a
high frequency voltage corresponding to their
on-off cycle period appears as inverter output
across the secondary winding 3-9 of the transformer 3-1. Fig. 2D shows the waveform
of this inverter output.Since the output volt
age of the inverter 3 corresponds to the
primary input voltage to the transformer 3-1, having the waveform as shown in Fig. 2C, its
envelope corresponds to that shown in Fig.
2C. In this case, the lamp current of the
discharge lamp 5 has a waveform similar to that of the output voltage of the inverter 3.
The output of the inverter 3 is impressed across the electrodes 5-1 and 5-2 of the discharge lamp 5. The discharge lamp 5 is supplied with a high frequency voltage, for
instance at 100 KHz, so that it is energized with a cycle period shorter than the internal ion re-excitation period and is continuously lit.
In addition, since the minimum voltage of the driving voltage supplied to the inverter 3 is set to correspond to the DC voltage V2 equal to or higher than one-third of the peak voltage
Vmax, so that practically no extra energy for ion re-excitation is required even during the low voltage period. Thus, it is possible to eliminate pause period of the lamp operation, which would reduce the lamp efficiency.
Now, the reason why the DC voltage V2 is set to be equal to or above one-third of the peak value Vmax of the pulsating voltage will be discussed.
Fig. 3 shows a characteristic curve of a lamp efficiency versus voltage ratio obtained with respect to a mercury lamp as the discharge lamp. In this case, a rated lamp power is 250 watts and the rated lamp voltage is 1 30 volts. Further, a lamp efficiency which is achieved by using a conventional low frequency ballast with a secondary no-load voltage of 200 volts is set at 100% in this characteristic curve. This is true also in the cases of Figs. 4 to 6. In the Figure, the ordinate is taken for the lamp efficiency (in %), and the abscissa is taken for the voltage ratio V2Vmax. As the lamp operating circuit the embodiment of Fig. 1 has been used, and a 50 Hz power source as the source 1. It will be seen from Fig. 3 that when the 100 (%) lamp efficiency is the permissible efficiency, the voltage ratio is about 0.3. With the decrease of the voltage ratio from 0.3 the lamp efficiency is sharply reduced. Thus the voltage ratio should be set to be above 0.3, that is, V2 should be v2 > /3Vmax.
Fig. 4 shows a similar lamp efficiency versus voltage ratio plot obtained with a metal halide lamp of 250 watt rated lamp power and 1 30 volt rated lamp voltage. In this case again a voltage ratio of about 0.35 corresponds to the 100 % lamp efficiency.
Fig. 5 shows a plot obtained with a high pressure sodium lamp of 250 watt rated lamp power and 95 volt rated lamp voltage, and
Fig. 6 shows a plot obtained with a fluorescent lamp of 1 10 watt lamp power and 1 55 volt rated lamp voltage. In either case, a voltage ratio of around 0.3 corresponds to the 100 % lamp efficiency.
It will be seen from any of the above plots that for providing a lamp efficiency in excess of 100 % the DC voltage V2 should be V21 /3Vrnsx. The value of the voltage V2 varies with the change of the discharging period of the capacitor 5-5 and the minimum value of the voltage V2 during the discharging period should be so set as to satisfy the relation V21 1 / 3may In the meantime, it is to be noted that in any of the characteristic curves of Figs. 3 to 6 that the lamp efficiency is practically constant for voltage ratio values above a certain value.
While the voltage ratio may be set to any value above 0.3 so far as the lamp efficiency alone is considered, for the operation of this kind of discharge lamp as high power factor of the lamp operation circuit as possible is required together with the high lamp efficiency. Usually, the power factor of more than 85 % is desired in this type of lamp operation circuit.
The power factor of the circuit of the embodiment of Fig. 1 depends upon the stepdown ratio of the transformer 6-1 and the capacitance of the smoothing capacitor 6-5 used in the DC power source 6. By setting the output voltage of the transformer 6-1 high and the capacitance of the capacitor 6-5 large, the ratio of V2 and Vmax will become approximately 1 to operate the discharge lamp 5 in a range in which the lamp efficiency is saturated as shown in Figs. 4 to 6. In this case, however, the circuit power factor remarkably raduces. Fig. 7A to Fig. 7C show characteristic curves of the circuit power factor versus the voltage ratio of V2 and Vmax. The characteristic curve with respect to a mercury lamp and a metal halide lamp is shown in Fig.
7A. Those of high-pressure sodium lamp and the fluorescent lamp are shown in Fig. 7B and
Fig. 7C, respectively. Though the characteristic of Figs. 7A to 7B slightly differ with the lamp voltage of the discharge lamp 5, the differences thereof can be negligible. As is evident from Figs. 7A to 7C, the voltage ratio
V2/Vmax should be set not larger than 0.8.
When the voltage ratio is larger than 0.8, the circuit power factor will reduce remarkably and a so-called high power factor of 0.85 can not be realized. While the use of a combination of inductance and capacitance for improving the power factor is conceivable, pronounced power factor improvement cannot be expected in this case, and the size and cost of the apparatus become inevitably large.
While in the above embodiment of Fig. 1 the DC power source 6 has been formed by the transformer 6-1, full-wave rectifier 6-4 and smoothing capacitor 6-5, this is by no means limitative. For example, a DC power source as shown in Fig. 8, including a fullwave rectifier 11-1, an inverter 11-2, a smoothing capacitor 11-3 and a rectifying diode 11-4, may be employed as well. In
Figs. 1 and 8, like parts are designated by like reference numerals.
In Fig. 8, the inverter 3 is the same as that in Fig. 1 and simply shown as a block. The inverter 11-2 is also shown as a block for the same reason. The AC voltage from the AC power source 11 is impressed between the
AC input terminals of the full-wave rectifying circuit 11-1, and a plusating voltage is obtained from the DC output terminals thereof.
The pulsating voltage is coupled to the inverter 11-2, whereby a high frequency voltage having the envelope of pulsating voltage waveform is obtained. The amplitude of the high frequency voltage can be appropriately set depending upon the turns ratios of the primary and secondary windings of the transformer employed in the inverter 11-2 (corresponding to the transformer 3-1 in the case of the Fig. 1 circuit). The output of the inverter 11-2 is rectified through the diode 11-4 and smoothed through the capacitor 11-3 to obtain the DC voltage V2 coupled to the diode switch 6-6.
Fig. 9 shows an embodiment which is provided with a different DC power source 21 for obtaining the DC voltage V2. In Figs. 1 and 9 like parts are designated by like reference numerals. In this embodiment, part of the output of the inverter 3 is used as power for the DC power source 21. A transformer 3-1 in the inverter 3 includes a second secondary winding 3-1 5 which is connected between the AC input terminals of a full-wave rectifier 21-1. The DC output terminals of the fullwave rectifier 21-1 are connected across a smoothing capacitor 21-2, and the positive side terminal thereof is connected through a switching diode 6-6 to the positive output terminal of the full-wave rectifier 2.
In operation, a high frequency output, for instance at 100 KHz, obtained from the secondary side of the transformer 3-1 in the inverter 3 is set to a predetermined amplitude by the secondary winding 3-15 and rectified by the full-wave rectifier 21-1 to obtain a pulsating voltage, which is smoothed through the smoothing capacitor 21-2 to obtain DC voltage V2. The remaining part of operation is the same as in the embodiment of Fig. 1.
In the embodiment of Fig. 8 the transformer 6-1 shown in Fig. 1 can be omitted, and in the embodiment of Fig. 9 the inverter 11-2 shown in Fig. 8 is omitted. Thus, the circuit construction can be simplified.
Also, while in the above embodiments the diode switch 6-6 has been used to superimpose the DC voltage V2 on the pulsating voltage obtained from the full-wave rectifier 2, it is possible to use in lieu of the diode switch 6-6 a thyristor which is on-off phase controlled for switching the DC voltage V2.
Claims (6)
1. Apparatus for operating a discharge lamp comprising rectifying means for rectifying a low frequency AC voltage to obtain a pulsating voltage, an inverter for inverting said pulsating voltage to a high frequency voltage and means for operating a discharge lamp according to the output of said inverter, characterized by an auxiliary power source for generating an auxiliary voltage, and a switch circuit for adding said auxiliary voltage to said pulsating voltage to have a resultant voltage only while said pulsating voltage is lower than said auxiliary voltage, minimum value Vmjn of the resultant voltage and the maximum value V of said resultant voltage being set to meet a condition 4/SVmxxVminl/3Vmax
2.Apparatus for operating a discharge lamp according to claim 1, characterized in that said auxiliary power source includes a transformer for stepping down the low frequency AC voltage to a predetermined level, a second rectifier for rectifying the secondary output voltage of said transformer, and a smoothing circuit including at least a smoothing capacitor for smoothing the output voltage of said rectifier and supplying the smoothed
DC voltage to said switch circuit.
3. Apparatus for operating a discharge lamp according to claim 1, characterized in that said auxiliary power source includes a second rectifier for rectifying the low frequency AC voltage, a second inverter driven by the pulsating voltage output of said second rectifier to generate a high frequency voltage, and a third rectifier including a capacitor and a diode for rectifying and smoothing the output voltage of said second inverter to obtain a
DC voltage of a predetermined level and supplying said DC voltage to said switch circuit.
4. Apparatus for operating a discharge lamp according to claim 1, characterized in that said auxiliary power source includes a secondary winting provided in said inverter, a second rectifier for rectifying a high frequency voltage generated in said secondary winding and a smoothing capacitor for smoothing the pulsating voltage output of said second rectifier, a smoothed DC voltage thus obtained being supplied to said switch circuit.
5. Apparatus for operating a discharge lamp according to any one of claims 1 to 4, characterized in that said switch circuit has the anode connected to the positive output terminal of said auxiliary power source and the cathode connected to the positive output terminal of said rectifier.
6. Apparatus for operating a discharge lamp, substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8105425A GB2093644A (en) | 1981-02-20 | 1981-02-20 | Apparatus for operating discharge lamps |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8105425A GB2093644A (en) | 1981-02-20 | 1981-02-20 | Apparatus for operating discharge lamps |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2093644A true GB2093644A (en) | 1982-09-02 |
Family
ID=10519847
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8105425A Withdrawn GB2093644A (en) | 1981-02-20 | 1981-02-20 | Apparatus for operating discharge lamps |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2093644A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996007296A2 (en) * | 1994-08-24 | 1996-03-07 | Philips Electronics N.V. | Circuit arrangement for a discharge lamp comprising first and second means for generating low frequency current to the lamp |
-
1981
- 1981-02-20 GB GB8105425A patent/GB2093644A/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996007296A2 (en) * | 1994-08-24 | 1996-03-07 | Philips Electronics N.V. | Circuit arrangement for a discharge lamp comprising first and second means for generating low frequency current to the lamp |
| WO1996007296A3 (en) * | 1994-08-24 | 1996-05-30 | Philips Electronics Nv | Circuit arrangement for a discharge lamp comprising first and second means for generating low frequency current to the lamp |
| CN1082330C (en) * | 1994-08-24 | 2002-04-03 | 皇家菲利浦电子有限公司 | Circuit arrangement |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |