CA1281369C - Apparatus for limiting arc discharge current in incandescent lamp - Google Patents
Apparatus for limiting arc discharge current in incandescent lampInfo
- Publication number
- CA1281369C CA1281369C CA000496652A CA496652A CA1281369C CA 1281369 C CA1281369 C CA 1281369C CA 000496652 A CA000496652 A CA 000496652A CA 496652 A CA496652 A CA 496652A CA 1281369 C CA1281369 C CA 1281369C
- Authority
- CA
- Canada
- Prior art keywords
- incandescent lamp
- discharge current
- circuit
- resistance
- arc discharge
- 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 - Lifetime
Links
Classifications
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- Y02B20/14—
Landscapes
- Circuit Arrangement For Electric Light Sources In General (AREA)
Abstract
Abstract of the Disclosure An arc discharge current occurred in dc-illuminated incandescent lamp can be effectively suppressed with an appar-atus comprising first resistance connected in series with an incandescent lamp circuit; a second resistance connected in series with the incandescent lamp circuit; and a reverse-blocking triode thyristor connected in parallel with the second resistance and openable with the voltage drop produced across the first resistance by an arc discharge current.
Description
~L~8~3~i9 APPARATUS FOR LIMITING ARC DISCHARGE CURRENT
IN INCANDESCENT LAMP
Field of the Invention The present invention relates to an apparatus to limit arc discharge current in incandescent lamp.
Description of the Prior Art When incandescent lamp is dc-illuminated to reduce flicker, the filament snapping instantly starts arc to flow a relatively high discharge current through the charged gas.
The arc occurs almost in a short-circuit state because the circuit resistance during discharge is extremely low. Upon an actual survey, a discharge current of up to 200 amperes was observed when the filament of 60-watt incandescent lamp was snapped during illumination with dc 130 volts.
The arc discharge current may damage many of the circuit parts.
Brief Summary of the Invention In view of the foregoing, the main object of the present invention îs to provide a means to limit arc discharge current in incandescent lamp.
~ 28~3Çi~
Still another object of the present invention is to provide a means to automatically effect such current limitation.
The invention relates to a device to limit arc discharge arising in a dc-operated incandescent lamp, comprising: (a) a rectifier circuit having input terminals connected with an ac sourc~, and output terminals connected with the incandescent lamp; (b) first resistance means connected in series with the incandescent lamp, for limiting both an initial switch-on surge into the incandescent lamp and an arc discharge current due to the filament of the incandescent lamp being snapped; (c) second resistive means connected in series with the incandescent lamp, for providing by virtue of a voltage drop across it a signal indicating occurrence of arc discharge current; (d) switching means having a trigger ~lectrode and a main current path, the main current path being connected in parallel with the first resistive means; and (e) a time constant circuit, having an output connected with the trigger electrode of the switching means, to retard, on switch-on, the conduction of the switching means in accordance with its time constant, and to suspend the conduction of the switching means when the voltage across the second resistive means reaches a predetermined level.
Descri~tion of the Preferred Embodiments Several embodiments according to the invention will hereinafter be explained taken in connection with the rn~
2a accompanying drawings wherein:
Figure 1 shows the ~asic circuit of the apparatus according to the invention, particularly the connection instantly upon turning-on;
Figure 2 shows the basic circuit of the apparatus according to the invention, particularly the connection instantly after the filament snapping has generated an arc;
Figure 3 shows a current curve that appears in the basic circuit as shown in Figure :L;
Figure 4 shows a current curve that appears in the basic circuit as shown in Figure 2;
rn/~
~ 3 FIG.5 shows the circuit of an embodiment according to the invention;
FIG.6 sh~ws the voltage waveform that appears in the circuit as shown in FIG.5;
FIG.7 shows the current waveform that appears in the circuit as shown in FIG.5 upon turning-on;
FIG.8 shows the current waveform that appears in the circuit as shown in FIG.5 during arc clischarge; and FIG.9 shows the circuit of an embodiment according to the invention, wherein a transistor is equipped to the limiting circuit.
Throughout the accompanying drawings, symbol A
designates rectifier; B, time-constant circuit; C, capaci-tance; D, diode; L, lamp; R, resistance; S, switch; AC, ac power source; and SCR, thyristor.
FIGs.l and 2 show the basic circuit of the apparatus according to the invention.
The circuit as shown in FIG.l is arranged in such a manner that ac current is supplied from ac power source AC to capacitance C and lamp L through power switch Sl and the plus output terminal of full-wave rectifier A. The return circuit is connected to the minus output terminal of full-wave recti-fier A through limiting resistance R2.
After a lapse of a prescribed time upon turning-on of power switch Sl, time-constant circuit B closes breaking switch S2 to short Limiting resistance R2 connected in paral-~ 3~9 lel to switch S2. Thus, the full output of recti~ier A issupplied to lamp L.
In the connection as shown in FIG.2, if the filament of lamp L is snapped when switch S2 is closed, the resultant arc decreases the circuit resistance to approximately zero to flow a discharge current of up to 200 amperes. The discharge current produces a voltage drop across low resistance Rl, connected in series to the main current circuit, and the voltage drop operates time-constant circuit B to open breaking switch S2. Thus, the inflow of the discharge current is switched to limiting resistance R2 to suppress the circuit current.
These operation will be further explained with reference to FIGs.3 and 4.
Instantly after power switch Sl is closed at time to~ a surge current with a magnitude of 10-fold larger than that of the rating flows as shown in FIG.3 with the broken line. If limiting resistance R2 is connected in series with lamp L, the circuit current is suppressed as shown in FIG.3 with the solid line.
FIG.4 shows the current curve that appears upon filament snapping. The filament snapping instantly starts arc at time t2, and the inflow of a discharge current with a magnitude of 180 amperes continues. If low resistance Rl, e.g. 2 ohms, is connected in series to lamp ~ as particularly shown in FIG.2, the discharge current is suppressed to 50 ;~:
. 1~8~L3~9 amperes or lower. Simultaneously, the voltage drop of about 50 volts, produced ~cr~ss resistance Rl by the discharge current, operates time-constant circuit B to open breaking switch S2. Thus, the circuit current is suppressed as shown in FIG.4 with thP solid line.
FIG.5 shows the circuit of an embodiment according to the invention. This embodiment is arranged so that turn-ing-on of switch Sl energizes both capacitance C and lamp L.
The return circuit is connected to the minus output terminal of rectifier A through both limiting resistance R2 and low resistance Rl, placed within lamp L, in order to limit an initial surge current.
The ~ilament resistance of lamp L upon turning-on of power switch Sl is 10 ohms or lower, and the voltage across capacitance C is, therefore, approximately zero. For this reason, the surge current upon turning-on of power switch Sl reaches 20 amperes or higher if limiting resistance R2 and low resistance Rl are not used. The surge current can be sup-pressed to a level of one ampere or lower by the insertion of limiting resistance R2.
After a lapse of the time as determined by ti~e-constant circuit B consisting of resistance R4 and capacitance Cl, capacitance Cl charged through resistance R4 energiæes the gate of reverse-blocking triode thyristor SCR to bring it into conduction. The conduction of reverse-blocking triode thyris-tor SCR shorts limiting resistance R2 to supply the full ~'~8~36 output of rectifier A to lamp L.
If the filament of lamp L is snapped during illumi-nation, an arc occurs and permits a discharge current of up to 200 amperes to flow through the charged gas. Although in ac-illumination arc occurs similarly but disappears within one cycle, in dc illumination an arc discharge current continues to damage the relating circuit parts.
In the circuit according to the invention, a relat-ively high discharge current produces a voltage drop of up to 100 volts between resistance Rl.
The voltage drop negatively charges capacitance Cl through diode D to c-ancel the positive voltage from resistance R4 and also to decrease the gate voltage of reverse-blocking triode thyristor SCR below its gate-triggering level. Thus, the conduction of the thyristor is suspended, and the increas-ing voltage drop between limiting resistance R2 stops the arc occurred in lamp L.
The current- and voltage-waveforms at this momen~
are as shown in FIGs.6 to 7.
FIG.6 shows the voltage curve that appears between the plus- and minus-terminals of rectifier A. As is evident from FIG.6, reverse-blocking triode thyristor SCR requires a continuous triggering because the voltage curve 7ero-cross-overs every half-cycles.
If limiting resistance R~ and low resistance Rl are removed from the circuit as shown in FIG.5, a surge current of ~2 ~
10 amperes or higher flows upon turning-on o power switch S2 at time to as shown in FIG.7 with the broken line. In the circuit as shown in FIG.5, the circ~lit current is suppressed by reverse-blocking triode thyristor SCR and limiting resis-tance R2 as shown in FIG.5 with the solid line, and, after a lapse of a prescribed time tl, e.g. 10-odd hundredths of one second, limiting resistance R2 is shorted by reverse-blocking triode thyristor SCR. Thus, the current across the filament of lamp L slightly increases at first, but shortly reaches the stationary level as shown in FIG.7 with the solid line.
As shown in FIG.8 with the broken line, when lamp L
is dc-illuminated in conventional manner, the filament snap-ping of lamp L produces arc at time t3, and an discharge current of up to 200 amperes comes into flow. The solid line as shown in FIG.8 indicates that the discharge current can be suppressed to 50 amperes by setting low resistance Rl in the circuit as shown in FIG.5 to 2 ohms. The voltage drop produc-ed across low resistance Rl by the discharge current nega-tively energizes the gate of reverse-blocking triode thyristor SCR to suspend its conduction in the next half-cycle of the waveform chart as shown in FIG.6.
FIG.9 shows the circuit of another embodiment ac-cording to the invention. This circuit is arranged by replac-ing a part of the circuit as shown in FIG.5 with transistor T
so that the voltage drop produced across low resistance Rl keeps the base voltage at cut-off level. Thus, the operation ~;
.~ , .
._ of reverse-blocking triode thyristor SCR is suspended with the discharge current for a prescribed time.
~ pon turning-on of power switch Sl, transistor T is conducted by resistances R4 and R6 to charge capacitance C, and the discharge current from capacitance C conducts reverse-blocking triode thyristor SCR. The voltage drop produced across low resistance Rl negative]y charges capacitance C
through diode D to keep transistor T at cut-off state for a prescribed time so that no triggering voltage is supplied to reverse-blocking triode thyristor SCR. Thus, the discharge current occurred in lamp L is broken.
While I have shown and described particular embodi-ments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.
,.
IN INCANDESCENT LAMP
Field of the Invention The present invention relates to an apparatus to limit arc discharge current in incandescent lamp.
Description of the Prior Art When incandescent lamp is dc-illuminated to reduce flicker, the filament snapping instantly starts arc to flow a relatively high discharge current through the charged gas.
The arc occurs almost in a short-circuit state because the circuit resistance during discharge is extremely low. Upon an actual survey, a discharge current of up to 200 amperes was observed when the filament of 60-watt incandescent lamp was snapped during illumination with dc 130 volts.
The arc discharge current may damage many of the circuit parts.
Brief Summary of the Invention In view of the foregoing, the main object of the present invention îs to provide a means to limit arc discharge current in incandescent lamp.
~ 28~3Çi~
Still another object of the present invention is to provide a means to automatically effect such current limitation.
The invention relates to a device to limit arc discharge arising in a dc-operated incandescent lamp, comprising: (a) a rectifier circuit having input terminals connected with an ac sourc~, and output terminals connected with the incandescent lamp; (b) first resistance means connected in series with the incandescent lamp, for limiting both an initial switch-on surge into the incandescent lamp and an arc discharge current due to the filament of the incandescent lamp being snapped; (c) second resistive means connected in series with the incandescent lamp, for providing by virtue of a voltage drop across it a signal indicating occurrence of arc discharge current; (d) switching means having a trigger ~lectrode and a main current path, the main current path being connected in parallel with the first resistive means; and (e) a time constant circuit, having an output connected with the trigger electrode of the switching means, to retard, on switch-on, the conduction of the switching means in accordance with its time constant, and to suspend the conduction of the switching means when the voltage across the second resistive means reaches a predetermined level.
Descri~tion of the Preferred Embodiments Several embodiments according to the invention will hereinafter be explained taken in connection with the rn~
2a accompanying drawings wherein:
Figure 1 shows the ~asic circuit of the apparatus according to the invention, particularly the connection instantly upon turning-on;
Figure 2 shows the basic circuit of the apparatus according to the invention, particularly the connection instantly after the filament snapping has generated an arc;
Figure 3 shows a current curve that appears in the basic circuit as shown in Figure :L;
Figure 4 shows a current curve that appears in the basic circuit as shown in Figure 2;
rn/~
~ 3 FIG.5 shows the circuit of an embodiment according to the invention;
FIG.6 sh~ws the voltage waveform that appears in the circuit as shown in FIG.5;
FIG.7 shows the current waveform that appears in the circuit as shown in FIG.5 upon turning-on;
FIG.8 shows the current waveform that appears in the circuit as shown in FIG.5 during arc clischarge; and FIG.9 shows the circuit of an embodiment according to the invention, wherein a transistor is equipped to the limiting circuit.
Throughout the accompanying drawings, symbol A
designates rectifier; B, time-constant circuit; C, capaci-tance; D, diode; L, lamp; R, resistance; S, switch; AC, ac power source; and SCR, thyristor.
FIGs.l and 2 show the basic circuit of the apparatus according to the invention.
The circuit as shown in FIG.l is arranged in such a manner that ac current is supplied from ac power source AC to capacitance C and lamp L through power switch Sl and the plus output terminal of full-wave rectifier A. The return circuit is connected to the minus output terminal of full-wave recti-fier A through limiting resistance R2.
After a lapse of a prescribed time upon turning-on of power switch Sl, time-constant circuit B closes breaking switch S2 to short Limiting resistance R2 connected in paral-~ 3~9 lel to switch S2. Thus, the full output of recti~ier A issupplied to lamp L.
In the connection as shown in FIG.2, if the filament of lamp L is snapped when switch S2 is closed, the resultant arc decreases the circuit resistance to approximately zero to flow a discharge current of up to 200 amperes. The discharge current produces a voltage drop across low resistance Rl, connected in series to the main current circuit, and the voltage drop operates time-constant circuit B to open breaking switch S2. Thus, the inflow of the discharge current is switched to limiting resistance R2 to suppress the circuit current.
These operation will be further explained with reference to FIGs.3 and 4.
Instantly after power switch Sl is closed at time to~ a surge current with a magnitude of 10-fold larger than that of the rating flows as shown in FIG.3 with the broken line. If limiting resistance R2 is connected in series with lamp L, the circuit current is suppressed as shown in FIG.3 with the solid line.
FIG.4 shows the current curve that appears upon filament snapping. The filament snapping instantly starts arc at time t2, and the inflow of a discharge current with a magnitude of 180 amperes continues. If low resistance Rl, e.g. 2 ohms, is connected in series to lamp ~ as particularly shown in FIG.2, the discharge current is suppressed to 50 ;~:
. 1~8~L3~9 amperes or lower. Simultaneously, the voltage drop of about 50 volts, produced ~cr~ss resistance Rl by the discharge current, operates time-constant circuit B to open breaking switch S2. Thus, the circuit current is suppressed as shown in FIG.4 with thP solid line.
FIG.5 shows the circuit of an embodiment according to the invention. This embodiment is arranged so that turn-ing-on of switch Sl energizes both capacitance C and lamp L.
The return circuit is connected to the minus output terminal of rectifier A through both limiting resistance R2 and low resistance Rl, placed within lamp L, in order to limit an initial surge current.
The ~ilament resistance of lamp L upon turning-on of power switch Sl is 10 ohms or lower, and the voltage across capacitance C is, therefore, approximately zero. For this reason, the surge current upon turning-on of power switch Sl reaches 20 amperes or higher if limiting resistance R2 and low resistance Rl are not used. The surge current can be sup-pressed to a level of one ampere or lower by the insertion of limiting resistance R2.
After a lapse of the time as determined by ti~e-constant circuit B consisting of resistance R4 and capacitance Cl, capacitance Cl charged through resistance R4 energiæes the gate of reverse-blocking triode thyristor SCR to bring it into conduction. The conduction of reverse-blocking triode thyris-tor SCR shorts limiting resistance R2 to supply the full ~'~8~36 output of rectifier A to lamp L.
If the filament of lamp L is snapped during illumi-nation, an arc occurs and permits a discharge current of up to 200 amperes to flow through the charged gas. Although in ac-illumination arc occurs similarly but disappears within one cycle, in dc illumination an arc discharge current continues to damage the relating circuit parts.
In the circuit according to the invention, a relat-ively high discharge current produces a voltage drop of up to 100 volts between resistance Rl.
The voltage drop negatively charges capacitance Cl through diode D to c-ancel the positive voltage from resistance R4 and also to decrease the gate voltage of reverse-blocking triode thyristor SCR below its gate-triggering level. Thus, the conduction of the thyristor is suspended, and the increas-ing voltage drop between limiting resistance R2 stops the arc occurred in lamp L.
The current- and voltage-waveforms at this momen~
are as shown in FIGs.6 to 7.
FIG.6 shows the voltage curve that appears between the plus- and minus-terminals of rectifier A. As is evident from FIG.6, reverse-blocking triode thyristor SCR requires a continuous triggering because the voltage curve 7ero-cross-overs every half-cycles.
If limiting resistance R~ and low resistance Rl are removed from the circuit as shown in FIG.5, a surge current of ~2 ~
10 amperes or higher flows upon turning-on o power switch S2 at time to as shown in FIG.7 with the broken line. In the circuit as shown in FIG.5, the circ~lit current is suppressed by reverse-blocking triode thyristor SCR and limiting resis-tance R2 as shown in FIG.5 with the solid line, and, after a lapse of a prescribed time tl, e.g. 10-odd hundredths of one second, limiting resistance R2 is shorted by reverse-blocking triode thyristor SCR. Thus, the current across the filament of lamp L slightly increases at first, but shortly reaches the stationary level as shown in FIG.7 with the solid line.
As shown in FIG.8 with the broken line, when lamp L
is dc-illuminated in conventional manner, the filament snap-ping of lamp L produces arc at time t3, and an discharge current of up to 200 amperes comes into flow. The solid line as shown in FIG.8 indicates that the discharge current can be suppressed to 50 amperes by setting low resistance Rl in the circuit as shown in FIG.5 to 2 ohms. The voltage drop produc-ed across low resistance Rl by the discharge current nega-tively energizes the gate of reverse-blocking triode thyristor SCR to suspend its conduction in the next half-cycle of the waveform chart as shown in FIG.6.
FIG.9 shows the circuit of another embodiment ac-cording to the invention. This circuit is arranged by replac-ing a part of the circuit as shown in FIG.5 with transistor T
so that the voltage drop produced across low resistance Rl keeps the base voltage at cut-off level. Thus, the operation ~;
.~ , .
._ of reverse-blocking triode thyristor SCR is suspended with the discharge current for a prescribed time.
~ pon turning-on of power switch Sl, transistor T is conducted by resistances R4 and R6 to charge capacitance C, and the discharge current from capacitance C conducts reverse-blocking triode thyristor SCR. The voltage drop produced across low resistance Rl negative]y charges capacitance C
through diode D to keep transistor T at cut-off state for a prescribed time so that no triggering voltage is supplied to reverse-blocking triode thyristor SCR. Thus, the discharge current occurred in lamp L is broken.
While I have shown and described particular embodi-ments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.
,.
Claims (4)
1. A device to limit arc discharge arising in a dc-operated incandescent lamp, comprising:
(a) a rectifier circuit having input terminals connected with an ac source, and output terminals connected with said incandescent lamp;
(b) first resistance means connected in series with the incandescent lamp, for limiting both an initial switch-on surge into the incandescent lamp and an arc discharge current due to the filament of the incandescent lamp being snapped;
(e) second resistive means connected in series with the incandescent lamp, for providing by virtue of a voltage drop across it a signal indicating occurrence of are discharge current;
(d) switching means having a trigger electrode and a main current path, said main current path being connected in parallel with the first resistive means; and (e) a time constant circuit, having an output connected with the trigger electrode of the switching means, to retard, on switch-on, the conduction of the switching means in accordance with its time constant, and to suspend the conduction of the switching means when the voltage across the second resistive means reaches a predetermined level.
(a) a rectifier circuit having input terminals connected with an ac source, and output terminals connected with said incandescent lamp;
(b) first resistance means connected in series with the incandescent lamp, for limiting both an initial switch-on surge into the incandescent lamp and an arc discharge current due to the filament of the incandescent lamp being snapped;
(e) second resistive means connected in series with the incandescent lamp, for providing by virtue of a voltage drop across it a signal indicating occurrence of are discharge current;
(d) switching means having a trigger electrode and a main current path, said main current path being connected in parallel with the first resistive means; and (e) a time constant circuit, having an output connected with the trigger electrode of the switching means, to retard, on switch-on, the conduction of the switching means in accordance with its time constant, and to suspend the conduction of the switching means when the voltage across the second resistive means reaches a predetermined level.
2. The device of claim 1, wherein said switching means comprises a reverse-blocking triode thyristor.
3. The device of claim 1, wherein the first and second resistive means are resistors.
4. The device of claim 1 comprising a capacitor connected in parallel with said incandescent lamp.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP93511984 | 1984-12-20 | ||
| JP259351/1984 | 1984-12-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1281369C true CA1281369C (en) | 1991-03-12 |
Family
ID=18529014
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000496652A Expired - Lifetime CA1281369C (en) | 1984-12-20 | 1985-12-02 | Apparatus for limiting arc discharge current in incandescent lamp |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1281369C (en) |
-
1985
- 1985-12-02 CA CA000496652A patent/CA1281369C/en not_active Expired - Lifetime
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| Date | Code | Title | Description |
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| MKLA | Lapsed |