CA1058277A - High pressure discharge lamp dimming circuit utilizing variable duty-cycle photocoupier - Google Patents
High pressure discharge lamp dimming circuit utilizing variable duty-cycle photocoupierInfo
- Publication number
- CA1058277A CA1058277A CA246,149A CA246149A CA1058277A CA 1058277 A CA1058277 A CA 1058277A CA 246149 A CA246149 A CA 246149A CA 1058277 A CA1058277 A CA 1058277A
- Authority
- CA
- Canada
- Prior art keywords
- input
- output
- led
- power
- power control
- 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
- 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
- H05B41/36—Controlling
- H05B41/38—Controlling the intensity of light
- H05B41/39—Controlling the intensity of light continuously
- H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
- H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
- H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation
- H05B41/3928—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation for high-pressure lamps, e.g. high-intensity discharge lamps, high-pressure mercury or sodium lamps
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S315/00—Electric lamp and discharge devices: systems
- Y10S315/04—Dimming circuit for fluorescent lamps
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S315/00—Electric lamp and discharge devices: systems
- Y10S315/05—Starting and operating circuit for fluorescent lamp
Landscapes
- Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
- Circuit Arrangements For Discharge Lamps (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The low-cost lighting control apparatus for high-pressure discharge lamps utilizing an ON-OFF photocoupler to provide isolation between the relatively high voltage AC
supplied to the lamp load and the relatively low voltage DC
control circuitry. Preferably, the apparatus is current-feedback stabilized utilizing a feedback resistor.
The low-cost lighting control apparatus for high-pressure discharge lamps utilizing an ON-OFF photocoupler to provide isolation between the relatively high voltage AC
supplied to the lamp load and the relatively low voltage DC
control circuitry. Preferably, the apparatus is current-feedback stabilized utilizing a feedback resistor.
Description
CROSS-REFERENCE TO RELATED APPLICAIION~
In U.S. Patent 3,991~44 issued November 9, 1976 to J, B~ Tabor and owned by the same assignee, is described a high-pressure discharge lamp dimmer for two high-pressure discharge lamps connected in series across a ballasting means which supplies twice the normal ballast output voltage and in which the dimmer is preferably current~feedback stabilized.
m is series connected lamp combination allows a greater dimming range, as when the voltage is reimpressed after both lamps have been off for some ~raction o~ a hal~-cycle, the voltage tends to appear primarily across one o~ the lamps, starting that lamp. The voltage across ~he lamp which has ~tarted quickly drops and the voltage then predominantly appears across the other lamp, starting it as well. This action provides reliable operation at relatively low power levels (where the lamps are off ~or a signi~icant portion of each half-cycle). The ser1es lamp arrangement of this copending application can conveniently be used with the apparatus described herei~O
BACKGROU~D OF TXE INVENTION
This invention relates to lighting systems which ., ~'~
45,62~
control the intensity of illumination such as in stage system or other llghting applications ~here the abl.lity to electronically ad~ust the level of illumination is desired.
In particular, this invention relates to controlling the intensity of light emitted from high-pressure discharge lampsO
In the past, the light intensity from high-pressure discharge lamps has generally not been ad~ustedO Incandescan~
lamp dimmers or fluorescent lamp dimmers (either with voltage feedback or with no feedback circuitry) are not satisfactory for dimming high-pressure discharge lamps. Incandescant lamp dimmers are generally not restricted to a particular fixed load but can instead be used with a vary~ng number o~
lamps. Because the load current is dependent on the load which is connected, such dimmers cannot control the current and thus current feedback, if any, merely limits the maximum load current, rather than providing a regulating or stablli-zation function. Further, as stabilizing feedback clrcuits in regulated incandescent dimmers control the voltage to the load~ such dimmers are not appropriate for high-pressure dis-charge lamps (the intensity from a high-pressure discharge lamp is not proportional to lamp voltage).
An additional problem which arises with high-pressure dlscharge lamps is that it is somewhat more dif~icult to design dimmers for more than one or two high-pressure dlscharge lamps, and thus a large number of dimmers will be required in most applications. Thus~ for high-pressure dis-charge lamps, the cost, size, and weight of the dlmmers is especially important.
SUMMARY OF TH~ INVENTION
The lighting control apparatus of this invention 45,~2~
3Z'7'~
provides a low ccst arrangement for varying the light intensity from a high-pressure discharge lamp load. The apparatus utili~es a photocoupler actuated by a variable duty cycle circuit which varies the ON time of a LED in response to an electrical demand signal. The use of a photo-coupler eliminates the need for a trans~ormer to provide electrical isolation between the higher voltage AC power and the lower voltage DC demand circuitry. The use of an ON-~OFF
type operation (rather than a proportional control in which the LED is always ON and the intensity of light from the LED is varied) eliminates the problems caused by the non-linear characteristics of the presently available photo-couplers~
Preferably, current feedback is prov~ded by a resistor and the current feedback transformer ls also ellminated.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be best understood by reference to the following drawings, in which:
Figure 1 is a block diagram illustrating the baslc relationship of the elements, including the~LED/photoresistor;
Figure 2 ls a block diagram illustrating the use of`
a current sensing means; and Figure 3 is a schematic showing a preferred embodiment.
DESCRIP'rION OF THE PREFERRED EMBODIMENTS
The block diagram of Figure 1 shows the basic elements of the llghting control apparatus to provide variable intensity light from a high-pressure discharge `lamp load. The power control means has a signal input, a powèr ~,628 ~ 5~7 ~
input and a power output (with the power input being adapted to be connected to a source of AC power). The ballasting means has an input and an output, and the ballasting means input is connected to the power control means outputO The discharge lamp load is connected to the output of the bal-lasting means. The varlable duty cycle circuit means has an , ~' lnput and an output and the variable duty-cycle circuit lnput is *~s~ed to be connected to a dëmand signal. The demand signal can be generated, for example, by a potentiometer be-tween DC~ and DC- terminals. The LED-photoresistor means provides electrical isolation between the demand signal and the power ontrol means. The LED-photoresistor means has an input and an output wlth the LED-photoresistor input being connected to the variable duty-cycle circuit output~ The LED-photoresistor output is connected to the signal input of the power control means. The dimmer comprises the power control means, the variable duty-cycle circuit means and the LED/photoresistor means. The dlmmer controls the power supplied (from the AC power source) to the ballasting means and thus controls the intensity of the high pressure lamp load.
The high-pressure discharge lamp load can consist of one or more high-pressure discharge lamps, and can consist of two serially-connected high-pressure discharge lamps as taught in the aforementioned copending applicationO Even with two lamps (lnstead of one) per dimmer, a large number of dimmers may be required. The elimination of transformers ln the dimmers reduces cost and also reduces size and welght.
The reduced size and welght makes lt practical to install dimmers in the light fixtures.
~ ~l5,628 ~8Z77 The block diagram of Figure 2 shows the use of a current sensing means to provide a regulated dimmer. The current sensing means must be located in series ~uch that it can sense a current proportional to load current, and can be located other than as shown in Figure 2 tfor example, between the AC power source and the power control means)O
The use of a resistor as the current sensing means avoids the the cost, wei~ht and size problems of current feedback trans-formers. As a relatively high current (iOeO the ballast pri-mary current) ~lows through this resistor, its value should be low (preferable less than 1 ohm) to avoid excessive power loss.
Figure 3 is a schematic showing a preferred embodiment.
Table l, below, gives typical values ~or use in the circuit shown in Figure 3O
TABLE I
Reference Identification Component Value -Rl 2.43K, lJ2W, 1%
R2 650 ohm, l/2w, 1%
R3 221K, l/2W, 1%
R4 515K, l/2W, 1%
R5 1.74K, l/2W, 1%
R6 lOK, l/2W, 1%
R7, R17 lOOK, 1/2W, 5%
R8 lM, 1/2W, 5%
R9 180K, l/2W, 5%
RlO 3.6K, l/2W, 5%
Rll 150K, 2W, 5%
Rl2 5K, 12W, 5%
- _5_ 45,62 ~ 5~Z7~
R13 0.1 ohm, 7W, 1%
R14 650K, 1/2W, 1%
R15 270K, 1/2W, 5%
R16 150K, 1/2W, 5%
R18 47K, 1/2W, 5%
Rl9 4.7K, 1/2W, 5%
R20 20K, 1/2W, 5%
R21 560 ohm, 1/2W, 5%
R22 lM, 2W, 5%
- ~ 20K, 5W, 1%`
R26 lM, 1/2W, 5%
CRl, CR3, CR4, CR5 IN645A
CR2 IN648B, 20V, 400MW
CR6 IN959B, 8.2V, 400MW
Cl oluF~ 50 C2, C6, C7 .o47uF, 50 C3 2200pF 50V
C4 47uF, 20V
C5 22uF, 35V
Ql. A01184, ECC Corp.
Q2 MBS 4991, Mo-torola Q3, Q4, Q5~ Q6 2N4351 Ul LM324N, National U2 MCT-2, Monsanto U3 741 Op Amp It will be noted that Figure 3 provides a circult ln which no transformers are used in the dlmmer cir~uit (the ballasts shown are of an autotransformer type but are not considered to be part of the dimmer). The use of resi6kor R13 as a current sen~ing means eliminates the need for a - ~l5,62~
~5~2~7 current f'eedback trans~ormer and the use of t,he LED-photo-resistor photocoupler U2 eliminates the need for an lsolation transformer. The circuit shown allows dimming of a h-Lgh-pressure mercury vapor lamp to about 5% of normal light output~
In khis particular circuit Rl, R2, R5, and R6 are selected such that various values of mercury lamps can be operated ~rom the same dimmer apparatus merely by inserting an appropriate ~umperc A jumper can be inserted such that Rl and R2 are in parallel for operation of 100-watt lamp~, or so that Rl and R5 are in parallel for operation of 175-watt lamps or that Rl and R6 are in parallel for operation o~
250-watt lamps or the circuit can be operated without a ~umper for operation of 400-watt lamps.
The AC switch Ql is connected in series with two hi~h reactance autotransformer ballasts Bl, B2 across the 277 VAC supply. The circuit compares the actual half-cycle average of the ballast primary current sensed by resist,or R13 to a demand signal related to the desired light level.
The result of this comparison i used to either advance or retard the turn-on time of Ql to either increase or decrease the lamp current. The AC switch (trlac) could, of course~
be replaced with back to back SCR's.
The demand signal is transferred by means of an optical coupler U2 formed by a light emitting diode (LED~
and a phototransistor. In this manner, the required isola-tion between the DC demand circuit and the AC power clrcuit is achieved without the use of an isolation transformerO
The DC demand signal is introduced into U3 and i5 converted to an ON-OFF (duty cycle type) signal by the relaxation oscillator circuit formed by operational amplifler ~5,~28 ~ 58Z7~
U30 The result of this converslon is to make the percentage of the time that the phototransistor U2 is ON proportional to the value o~ the demand signal. A mid-value of the demand signal results in the transistor portion of U2 being on approximately 50% of the time.
The photocoupler transistor current ~low~ through R3 to the summing node of the error detector amplifier UlC.
The duty cycle oscillator ~s formed by the com-bination of time~delayed negative feedback vla R9 and C`l and positive feedback via R8 and R70 The output voltage of U3 will, on the average, equal the input demand slgnal voltage.
Because of the hysteresis generated by the positive feedback, ~, however, the output will be a square wave oscillating between DC+ and DC- (supplied from a remote power supply having a voltage in the range of 8-30 volts). The square wave wlll have an average value equal to the pulse duty cycle multiplied by the power supply voltageO
Operational amplifier UlC forms an integral t~pe error detector which responds to the dif~erence between the reference current (average current through R3 and R4) and the ballast half-cycle average current as sensed by Rl30 During the negatlve half-cycle, the current flow through Rl (and any resistor R2 3 R5, R6 ~hich may be paralleled hy a ~umper~
from the error detector summing node of UlC (the ~unctlon of`
R3 and R4~ ls proportional to the average ballast currentO
The drop across CRl i8 offset by the drop across CR40 Capacitor C7 is used for noise suppression.
Should the ballast current be too large or too small, the current error present at the R3-R4 ~unctlon flows into C4 cau,~lng the capacitor voltage to go up or down. When 1~5~62~
~9S~3Z~7 UlC
the error is eliminated, the ~ output volkage stabilizes, A 120 Hz. ramp generator synchronized to line voltage zero crossing is formed by Rl5, C6 and the reset circult. The reset circuit is formed by the operational ampli~iers UlA and UlB which functions a voltage band detector which turns Q4 on whenever the instantaneous line voltage pas~es through a particular voltage range, With Q4 ON, capacitor C6 is clamped, When the line voltage passes through the partlcular voltage range, Q4 is turned of~ and capacitor C6 starts to charge. As explained belowg khe circuit which produces the AC switch gate trigger pulse, has a time delay of about 200 microseconds during the positive half cycle, but no delay during the negative half cycle and thus the ramp generated during the negative hal~ -cycle is des~gned (by means of the reset circuit~ to lag the ramp generated during the positive halY cycle by about 200 microseconds. In this way, the trigger pulses occur at the same time following zero voltage (each hal~ cycle) thereby eliminatlng any "60 Hz. flicker".
In the reset clrcuit, transistor Q4 is connected in an AND configuration such that i~ the output o~ Ul~ is high and the output of UlA is low (grounded), Q4 is ON?
This condition occurs at the beginning and end of each negative half cyc~e of the power llne, R19, R20~ R21, and R22 are selected such that the reset time interval is set at the desired 200 microsecond value (which compensates ~or the 200 mi¢rosecond o~set of the gate pulse generator~, In the gate pulse generator J the turn-on gate current pulses for the AC switch Ql are produced by slllcon bidirectional switch Q2, pulse discharge capacikor C2, and _9_ ~ 45j628 ~l~958;~7~7 charging resistor Rll. The bldirection switch Q2 ~s a three~
terminal device with a symmetrlcal switching voltage of about nine volts. The gate terminal Gl of Q2 provides the ability to lnhibit the switching process. When the gate termlnal Gl is grounded and transistor Q3 turned ON, the switch Q2 has the characteristic of an eight volt Zener diode between termlnals Gl and A2O The ~oltage across C2 is thus limited to about plus 1 volt in the positive direction and minus 8 volts in the negatlve direction. The difference in these voltages leads to the 200 mlcrosecond offset of the gate pulse generator. Once these voltages are reached, (each halI' cycle), excessive charging current through Rll is diverted to ground through Q2 terminals A2 and Gl and through transistor Q3~ -During the positive half cycle, the turn-off o~
Q3 causes C2 to start chargingO About 200 microseconds laterg when the voltage on C2 reaches 9 volts, the trlgger ~ires. Coupling capacitor C3 (between terminals A2 Or Q2 and the gate G2 of Q3) prevents the bidirectional switch Q2 from prematurely turning ON at the instant Q3 is turned OFF. When the gate voltage on G2 of Q3 drops, with Q5 turned ON, charge is transferred from C2 to C3 thereby reducing t,he voltage acroæs C20 The voltage across the bidirectional switch Q2 is dropped below its conduction level and thus premature turn-on is prevented.
R12 is used to prevent large inductive voltage transients when the AC switch Ql is turned OFF. R12 also provides a DC power supply current via CR3 (additiona1 cur-rent is provided by R25). When Ql is OFF and supportlng 400 volts, for example, the current through R12 is in excess of ~ 45,628 ~.~S827'7 the maximum holding eurrent of Ql. At the instant Ql turns ONg this current is switched from R12 to Ql.
The particular cireuit deseribed in Figure 3 illustrates the use of high-pressure mercury vapor lamps, however, the principles illustrated therein can be applied by one skilled in the art to other types of high-pressure discharge lamps such as metal-halide lamps. Appropriate modifications for different types of discharge lamps are known in the art, as some types (high pressure sodium lamps, for example) will normally require starting circuits.
In U.S. Patent 3,991~44 issued November 9, 1976 to J, B~ Tabor and owned by the same assignee, is described a high-pressure discharge lamp dimmer for two high-pressure discharge lamps connected in series across a ballasting means which supplies twice the normal ballast output voltage and in which the dimmer is preferably current~feedback stabilized.
m is series connected lamp combination allows a greater dimming range, as when the voltage is reimpressed after both lamps have been off for some ~raction o~ a hal~-cycle, the voltage tends to appear primarily across one o~ the lamps, starting that lamp. The voltage across ~he lamp which has ~tarted quickly drops and the voltage then predominantly appears across the other lamp, starting it as well. This action provides reliable operation at relatively low power levels (where the lamps are off ~or a signi~icant portion of each half-cycle). The ser1es lamp arrangement of this copending application can conveniently be used with the apparatus described herei~O
BACKGROU~D OF TXE INVENTION
This invention relates to lighting systems which ., ~'~
45,62~
control the intensity of illumination such as in stage system or other llghting applications ~here the abl.lity to electronically ad~ust the level of illumination is desired.
In particular, this invention relates to controlling the intensity of light emitted from high-pressure discharge lampsO
In the past, the light intensity from high-pressure discharge lamps has generally not been ad~ustedO Incandescan~
lamp dimmers or fluorescent lamp dimmers (either with voltage feedback or with no feedback circuitry) are not satisfactory for dimming high-pressure discharge lamps. Incandescant lamp dimmers are generally not restricted to a particular fixed load but can instead be used with a vary~ng number o~
lamps. Because the load current is dependent on the load which is connected, such dimmers cannot control the current and thus current feedback, if any, merely limits the maximum load current, rather than providing a regulating or stablli-zation function. Further, as stabilizing feedback clrcuits in regulated incandescent dimmers control the voltage to the load~ such dimmers are not appropriate for high-pressure dis-charge lamps (the intensity from a high-pressure discharge lamp is not proportional to lamp voltage).
An additional problem which arises with high-pressure dlscharge lamps is that it is somewhat more dif~icult to design dimmers for more than one or two high-pressure dlscharge lamps, and thus a large number of dimmers will be required in most applications. Thus~ for high-pressure dis-charge lamps, the cost, size, and weight of the dlmmers is especially important.
SUMMARY OF TH~ INVENTION
The lighting control apparatus of this invention 45,~2~
3Z'7'~
provides a low ccst arrangement for varying the light intensity from a high-pressure discharge lamp load. The apparatus utili~es a photocoupler actuated by a variable duty cycle circuit which varies the ON time of a LED in response to an electrical demand signal. The use of a photo-coupler eliminates the need for a trans~ormer to provide electrical isolation between the higher voltage AC power and the lower voltage DC demand circuitry. The use of an ON-~OFF
type operation (rather than a proportional control in which the LED is always ON and the intensity of light from the LED is varied) eliminates the problems caused by the non-linear characteristics of the presently available photo-couplers~
Preferably, current feedback is prov~ded by a resistor and the current feedback transformer ls also ellminated.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be best understood by reference to the following drawings, in which:
Figure 1 is a block diagram illustrating the baslc relationship of the elements, including the~LED/photoresistor;
Figure 2 ls a block diagram illustrating the use of`
a current sensing means; and Figure 3 is a schematic showing a preferred embodiment.
DESCRIP'rION OF THE PREFERRED EMBODIMENTS
The block diagram of Figure 1 shows the basic elements of the llghting control apparatus to provide variable intensity light from a high-pressure discharge `lamp load. The power control means has a signal input, a powèr ~,628 ~ 5~7 ~
input and a power output (with the power input being adapted to be connected to a source of AC power). The ballasting means has an input and an output, and the ballasting means input is connected to the power control means outputO The discharge lamp load is connected to the output of the bal-lasting means. The varlable duty cycle circuit means has an , ~' lnput and an output and the variable duty-cycle circuit lnput is *~s~ed to be connected to a dëmand signal. The demand signal can be generated, for example, by a potentiometer be-tween DC~ and DC- terminals. The LED-photoresistor means provides electrical isolation between the demand signal and the power ontrol means. The LED-photoresistor means has an input and an output wlth the LED-photoresistor input being connected to the variable duty-cycle circuit output~ The LED-photoresistor output is connected to the signal input of the power control means. The dimmer comprises the power control means, the variable duty-cycle circuit means and the LED/photoresistor means. The dlmmer controls the power supplied (from the AC power source) to the ballasting means and thus controls the intensity of the high pressure lamp load.
The high-pressure discharge lamp load can consist of one or more high-pressure discharge lamps, and can consist of two serially-connected high-pressure discharge lamps as taught in the aforementioned copending applicationO Even with two lamps (lnstead of one) per dimmer, a large number of dimmers may be required. The elimination of transformers ln the dimmers reduces cost and also reduces size and welght.
The reduced size and welght makes lt practical to install dimmers in the light fixtures.
~ ~l5,628 ~8Z77 The block diagram of Figure 2 shows the use of a current sensing means to provide a regulated dimmer. The current sensing means must be located in series ~uch that it can sense a current proportional to load current, and can be located other than as shown in Figure 2 tfor example, between the AC power source and the power control means)O
The use of a resistor as the current sensing means avoids the the cost, wei~ht and size problems of current feedback trans-formers. As a relatively high current (iOeO the ballast pri-mary current) ~lows through this resistor, its value should be low (preferable less than 1 ohm) to avoid excessive power loss.
Figure 3 is a schematic showing a preferred embodiment.
Table l, below, gives typical values ~or use in the circuit shown in Figure 3O
TABLE I
Reference Identification Component Value -Rl 2.43K, lJ2W, 1%
R2 650 ohm, l/2w, 1%
R3 221K, l/2W, 1%
R4 515K, l/2W, 1%
R5 1.74K, l/2W, 1%
R6 lOK, l/2W, 1%
R7, R17 lOOK, 1/2W, 5%
R8 lM, 1/2W, 5%
R9 180K, l/2W, 5%
RlO 3.6K, l/2W, 5%
Rll 150K, 2W, 5%
Rl2 5K, 12W, 5%
- _5_ 45,62 ~ 5~Z7~
R13 0.1 ohm, 7W, 1%
R14 650K, 1/2W, 1%
R15 270K, 1/2W, 5%
R16 150K, 1/2W, 5%
R18 47K, 1/2W, 5%
Rl9 4.7K, 1/2W, 5%
R20 20K, 1/2W, 5%
R21 560 ohm, 1/2W, 5%
R22 lM, 2W, 5%
- ~ 20K, 5W, 1%`
R26 lM, 1/2W, 5%
CRl, CR3, CR4, CR5 IN645A
CR2 IN648B, 20V, 400MW
CR6 IN959B, 8.2V, 400MW
Cl oluF~ 50 C2, C6, C7 .o47uF, 50 C3 2200pF 50V
C4 47uF, 20V
C5 22uF, 35V
Ql. A01184, ECC Corp.
Q2 MBS 4991, Mo-torola Q3, Q4, Q5~ Q6 2N4351 Ul LM324N, National U2 MCT-2, Monsanto U3 741 Op Amp It will be noted that Figure 3 provides a circult ln which no transformers are used in the dlmmer cir~uit (the ballasts shown are of an autotransformer type but are not considered to be part of the dimmer). The use of resi6kor R13 as a current sen~ing means eliminates the need for a - ~l5,62~
~5~2~7 current f'eedback trans~ormer and the use of t,he LED-photo-resistor photocoupler U2 eliminates the need for an lsolation transformer. The circuit shown allows dimming of a h-Lgh-pressure mercury vapor lamp to about 5% of normal light output~
In khis particular circuit Rl, R2, R5, and R6 are selected such that various values of mercury lamps can be operated ~rom the same dimmer apparatus merely by inserting an appropriate ~umperc A jumper can be inserted such that Rl and R2 are in parallel for operation of 100-watt lamp~, or so that Rl and R5 are in parallel for operation of 175-watt lamps or that Rl and R6 are in parallel for operation o~
250-watt lamps or the circuit can be operated without a ~umper for operation of 400-watt lamps.
The AC switch Ql is connected in series with two hi~h reactance autotransformer ballasts Bl, B2 across the 277 VAC supply. The circuit compares the actual half-cycle average of the ballast primary current sensed by resist,or R13 to a demand signal related to the desired light level.
The result of this comparison i used to either advance or retard the turn-on time of Ql to either increase or decrease the lamp current. The AC switch (trlac) could, of course~
be replaced with back to back SCR's.
The demand signal is transferred by means of an optical coupler U2 formed by a light emitting diode (LED~
and a phototransistor. In this manner, the required isola-tion between the DC demand circuit and the AC power clrcuit is achieved without the use of an isolation transformerO
The DC demand signal is introduced into U3 and i5 converted to an ON-OFF (duty cycle type) signal by the relaxation oscillator circuit formed by operational amplifler ~5,~28 ~ 58Z7~
U30 The result of this converslon is to make the percentage of the time that the phototransistor U2 is ON proportional to the value o~ the demand signal. A mid-value of the demand signal results in the transistor portion of U2 being on approximately 50% of the time.
The photocoupler transistor current ~low~ through R3 to the summing node of the error detector amplifier UlC.
The duty cycle oscillator ~s formed by the com-bination of time~delayed negative feedback vla R9 and C`l and positive feedback via R8 and R70 The output voltage of U3 will, on the average, equal the input demand slgnal voltage.
Because of the hysteresis generated by the positive feedback, ~, however, the output will be a square wave oscillating between DC+ and DC- (supplied from a remote power supply having a voltage in the range of 8-30 volts). The square wave wlll have an average value equal to the pulse duty cycle multiplied by the power supply voltageO
Operational amplifier UlC forms an integral t~pe error detector which responds to the dif~erence between the reference current (average current through R3 and R4) and the ballast half-cycle average current as sensed by Rl30 During the negatlve half-cycle, the current flow through Rl (and any resistor R2 3 R5, R6 ~hich may be paralleled hy a ~umper~
from the error detector summing node of UlC (the ~unctlon of`
R3 and R4~ ls proportional to the average ballast currentO
The drop across CRl i8 offset by the drop across CR40 Capacitor C7 is used for noise suppression.
Should the ballast current be too large or too small, the current error present at the R3-R4 ~unctlon flows into C4 cau,~lng the capacitor voltage to go up or down. When 1~5~62~
~9S~3Z~7 UlC
the error is eliminated, the ~ output volkage stabilizes, A 120 Hz. ramp generator synchronized to line voltage zero crossing is formed by Rl5, C6 and the reset circult. The reset circuit is formed by the operational ampli~iers UlA and UlB which functions a voltage band detector which turns Q4 on whenever the instantaneous line voltage pas~es through a particular voltage range, With Q4 ON, capacitor C6 is clamped, When the line voltage passes through the partlcular voltage range, Q4 is turned of~ and capacitor C6 starts to charge. As explained belowg khe circuit which produces the AC switch gate trigger pulse, has a time delay of about 200 microseconds during the positive half cycle, but no delay during the negative half cycle and thus the ramp generated during the negative hal~ -cycle is des~gned (by means of the reset circuit~ to lag the ramp generated during the positive halY cycle by about 200 microseconds. In this way, the trigger pulses occur at the same time following zero voltage (each hal~ cycle) thereby eliminatlng any "60 Hz. flicker".
In the reset clrcuit, transistor Q4 is connected in an AND configuration such that i~ the output o~ Ul~ is high and the output of UlA is low (grounded), Q4 is ON?
This condition occurs at the beginning and end of each negative half cyc~e of the power llne, R19, R20~ R21, and R22 are selected such that the reset time interval is set at the desired 200 microsecond value (which compensates ~or the 200 mi¢rosecond o~set of the gate pulse generator~, In the gate pulse generator J the turn-on gate current pulses for the AC switch Ql are produced by slllcon bidirectional switch Q2, pulse discharge capacikor C2, and _9_ ~ 45j628 ~l~958;~7~7 charging resistor Rll. The bldirection switch Q2 ~s a three~
terminal device with a symmetrlcal switching voltage of about nine volts. The gate terminal Gl of Q2 provides the ability to lnhibit the switching process. When the gate termlnal Gl is grounded and transistor Q3 turned ON, the switch Q2 has the characteristic of an eight volt Zener diode between termlnals Gl and A2O The ~oltage across C2 is thus limited to about plus 1 volt in the positive direction and minus 8 volts in the negatlve direction. The difference in these voltages leads to the 200 mlcrosecond offset of the gate pulse generator. Once these voltages are reached, (each halI' cycle), excessive charging current through Rll is diverted to ground through Q2 terminals A2 and Gl and through transistor Q3~ -During the positive half cycle, the turn-off o~
Q3 causes C2 to start chargingO About 200 microseconds laterg when the voltage on C2 reaches 9 volts, the trlgger ~ires. Coupling capacitor C3 (between terminals A2 Or Q2 and the gate G2 of Q3) prevents the bidirectional switch Q2 from prematurely turning ON at the instant Q3 is turned OFF. When the gate voltage on G2 of Q3 drops, with Q5 turned ON, charge is transferred from C2 to C3 thereby reducing t,he voltage acroæs C20 The voltage across the bidirectional switch Q2 is dropped below its conduction level and thus premature turn-on is prevented.
R12 is used to prevent large inductive voltage transients when the AC switch Ql is turned OFF. R12 also provides a DC power supply current via CR3 (additiona1 cur-rent is provided by R25). When Ql is OFF and supportlng 400 volts, for example, the current through R12 is in excess of ~ 45,628 ~.~S827'7 the maximum holding eurrent of Ql. At the instant Ql turns ONg this current is switched from R12 to Ql.
The particular cireuit deseribed in Figure 3 illustrates the use of high-pressure mercury vapor lamps, however, the principles illustrated therein can be applied by one skilled in the art to other types of high-pressure discharge lamps such as metal-halide lamps. Appropriate modifications for different types of discharge lamps are known in the art, as some types (high pressure sodium lamps, for example) will normally require starting circuits.
Claims (4)
1. A lighting control apparatus to provide variable intensity light from a high-pressure discharge lamp load utilizing a photocoupler actuated by a variable duty-cycle circuit which varies the ON time of an LED
in response to an externally generated electrical demand signal, said apparatus comprising:
(a) power control means having a signal input, a power input, and a power output, said power input being adapted to be connected to a source of AC power;
(b) ballasting means having an input and an output, said ballasting means input being connected to said power control means output;
(c) a discharge lamp load, said discharge lamp load being connected to the output of said ballasting means;
(d) variable duty-cycle circuit means having an input and an output, said demand signal adapted to be applied to the input of said variable duty-cycle circuit means; and (e) LED-photoresistor means for providing electrical isolation between said applied demand signal and said power control means, said LED-photoresistor means having an input and an output, said LED-photoresistor means input being connected to said variable duty-cycle circuit means output to cause said LED to be ON a percentage of the time which is proportional to the value of said demand signal, and said LED-photoresistor means output being connected to said signal input of said power control means.
in response to an externally generated electrical demand signal, said apparatus comprising:
(a) power control means having a signal input, a power input, and a power output, said power input being adapted to be connected to a source of AC power;
(b) ballasting means having an input and an output, said ballasting means input being connected to said power control means output;
(c) a discharge lamp load, said discharge lamp load being connected to the output of said ballasting means;
(d) variable duty-cycle circuit means having an input and an output, said demand signal adapted to be applied to the input of said variable duty-cycle circuit means; and (e) LED-photoresistor means for providing electrical isolation between said applied demand signal and said power control means, said LED-photoresistor means having an input and an output, said LED-photoresistor means input being connected to said variable duty-cycle circuit means output to cause said LED to be ON a percentage of the time which is proportional to the value of said demand signal, and said LED-photoresistor means output being connected to said signal input of said power control means.
2. The apparatus of claim 1, wherein a current sensing means is connected in series with said power control means for developing a current feedback signal and wherein said power control means has a feedback input and said current feedback signal is connected to said feedback input of said power control means.
3. The apparatus of claim 2, wherein said current sensing means is resistor having an electrical resistance of less than one ohm.
4. A lighting control apparatus to provide variable intensity light from a high-pressure discharge lamp load utilizing a photocoupler actuated by a variable duty-cycle circuit which varies the ON time of an LED in response to an externally generated electrical demand signal, said apparatus comprising:
(a) power control means having a signal input, a power input, and a power output, said power input being adapted to be connected to a source of AC power;
(b) ballasting means having an input and an out-put, said ballasting means input being connected to said power control means output;
(e) a discharge lamp load, said discharge lamp load being connected to the output of said ballasting means;
(d) variable duty-cycle circuit means having an input and an output, said demand signal adapted to be applied to the input of said variable duty-cycle circuit means;
(e) LED-photoresistor means for providing elec-trical isolation between said applied demand signal and said power control means, said LED-photoresistor means having an input and an output, and the output of said variable duty-cycle circuit means connected to the input of said LED-photoresistor means to cause said LED to be ON a percentage of the time which is proportional to the value of said demand signal;
(f) current sensing means connected with said power control means for developing a feedback signal; and (g) an error-detecting circuit having an input connected to the output of said current sensing means and the output of said LED-photoresistor means for receiving the signals therefrom and generating an error output signal which corresponds to the difference between the received signals;
and the output of said error-detecting circuit connected to the input of said power control means to control the current through said ballasting means.
(a) power control means having a signal input, a power input, and a power output, said power input being adapted to be connected to a source of AC power;
(b) ballasting means having an input and an out-put, said ballasting means input being connected to said power control means output;
(e) a discharge lamp load, said discharge lamp load being connected to the output of said ballasting means;
(d) variable duty-cycle circuit means having an input and an output, said demand signal adapted to be applied to the input of said variable duty-cycle circuit means;
(e) LED-photoresistor means for providing elec-trical isolation between said applied demand signal and said power control means, said LED-photoresistor means having an input and an output, and the output of said variable duty-cycle circuit means connected to the input of said LED-photoresistor means to cause said LED to be ON a percentage of the time which is proportional to the value of said demand signal;
(f) current sensing means connected with said power control means for developing a feedback signal; and (g) an error-detecting circuit having an input connected to the output of said current sensing means and the output of said LED-photoresistor means for receiving the signals therefrom and generating an error output signal which corresponds to the difference between the received signals;
and the output of said error-detecting circuit connected to the input of said power control means to control the current through said ballasting means.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/558,109 US4016451A (en) | 1975-03-13 | 1975-03-13 | High pressure discharge lamp dimming circuit utilizing variable duty-cycle photocoupler |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1058277A true CA1058277A (en) | 1979-07-10 |
Family
ID=24228247
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA246,149A Expired CA1058277A (en) | 1975-03-13 | 1976-02-19 | High pressure discharge lamp dimming circuit utilizing variable duty-cycle photocoupier |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4016451A (en) |
| CA (1) | CA1058277A (en) |
Families Citing this family (24)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4197485A (en) * | 1978-07-24 | 1980-04-08 | Esquire, Inc. | Optocoupler dimmer circuit for high intensity, gaseous discharge lamp |
| US4242614A (en) * | 1979-02-26 | 1980-12-30 | General Electric Company | Lighting control system |
| US4358716A (en) * | 1980-04-14 | 1982-11-09 | White Castle System, Inc. | Adjustable electrical power control for gas discharge lamps and the like |
| EP0104264A1 (en) * | 1982-09-24 | 1984-04-04 | White Castle System, Inc. | Adjustable electrical power control for gas discharge lamps and the like |
| US4682084A (en) * | 1985-08-28 | 1987-07-21 | Innovative Controls, Incorporated | High intensity discharge lamp self-adjusting ballast system sensitive to the radiant energy or heat of the lamp |
| US4686428A (en) * | 1985-08-28 | 1987-08-11 | Innovative Controls, Incorporated | High intensity discharge lamp self-adjusting ballast system with current limiters and a current feedback loop |
| US4999547A (en) * | 1986-09-25 | 1991-03-12 | Innovative Controls, Incorporated | Ballast for high pressure sodium lamps having constant line and lamp wattage |
| US5008865A (en) * | 1988-07-20 | 1991-04-16 | Blaine P. Shaffer | Light source with gradually changing intensity |
| US5402040A (en) * | 1993-11-23 | 1995-03-28 | The Watt Stopper | Dimmable ballast control circuit |
| US5744913A (en) * | 1994-03-25 | 1998-04-28 | Pacific Scientific Company | Fluorescent lamp apparatus with integral dimming control |
| US5686799A (en) * | 1994-03-25 | 1997-11-11 | Pacific Scientific Company | Ballast circuit for compact fluorescent lamp |
| US5691606A (en) * | 1994-09-30 | 1997-11-25 | Pacific Scientific Company | Ballast circuit for fluorescent lamp |
| US6037722A (en) * | 1994-09-30 | 2000-03-14 | Pacific Scientific | Dimmable ballast apparatus and method for controlling power delivered to a fluorescent lamp |
| US5821699A (en) * | 1994-09-30 | 1998-10-13 | Pacific Scientific | Ballast circuit for fluorescent lamps |
| US5596247A (en) * | 1994-10-03 | 1997-01-21 | Pacific Scientific Company | Compact dimmable fluorescent lamps with central dimming ring |
| US5925986A (en) * | 1996-05-09 | 1999-07-20 | Pacific Scientific Company | Method and apparatus for controlling power delivered to a fluorescent lamp |
| US5866993A (en) * | 1996-11-14 | 1999-02-02 | Pacific Scientific Company | Three-way dimming ballast circuit with passive power factor correction |
| US5798617A (en) * | 1996-12-18 | 1998-08-25 | Pacific Scientific Company | Magnetic feedback ballast circuit for fluorescent lamp |
| JP5657195B2 (en) * | 2005-01-19 | 2015-01-21 | コーニンクレッカ フィリップス エヌ ヴェ | Dimming control circuit dimming method and system |
| US7843145B2 (en) * | 2006-01-13 | 2010-11-30 | Universal Lighting Technologies, Inc. | System and method for power line carrier communication using high frequency tone bursts |
| JP5142403B2 (en) * | 2009-03-26 | 2013-02-13 | パナソニック株式会社 | Discharge lamp lighting device, lamp, and vehicle |
| JP6653452B2 (en) * | 2016-09-20 | 2020-02-26 | パナソニックＩｐマネジメント株式会社 | Protection circuit for dimmer and dimmer |
| US11152845B2 (en) * | 2018-02-16 | 2021-10-19 | Microchip Technology Incorporated | Feed-forward function for voltage mode control |
| US10630193B1 (en) | 2019-03-05 | 2020-04-21 | Ev Enterprises | Isolated phase control power regulation circuit and system |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3344310A (en) * | 1966-01-13 | 1967-09-26 | Gen Electric | Universal lamp control circuit with high voltage producing means |
| US3449619A (en) * | 1967-04-21 | 1969-06-10 | Tektronix Inc | Apparatus for controlling the voltage on an electron tube element |
| US3875458A (en) * | 1974-06-10 | 1975-04-01 | Westinghouse Electric Corp | Dimmer for discharge lamp utilizing a pulse enabling circuit |
-
1975
- 1975-03-13 US US05/558,109 patent/US4016451A/en not_active Expired - Lifetime
-
1976
- 1976-02-19 CA CA246,149A patent/CA1058277A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4016451A (en) | 1977-04-05 |
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