JPS58192297A - Circuit for dimming discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] This invention is bidirectional! Regarding the dimming control circuit for a discharge lamp using a 1U 3-terminal thyristor (hereinafter referred to as the thyristor), in particular, it uses an interlocking switch to
This invention relates to an improvement of a discharge lamp dimming circuit that expands the dimming range to about 140%.

Dimming a discharge lamp, even if the dimming range is 0 to 100%1, is as simple as simply lowering the voltage applied to the discharge lamp by controlling the phase of the triac in the main circuit, like when using an incandescent bulb as a load. This cannot be done with proper control.

In order for the discharge lamp to continue discharging in a steady state, the excited state within the discharge lamp tube must be maintained when the polarity of the commercial frequency power supply is reversed, and the applied voltage must be equal to or higher than the restriking voltage. The relationship between the quality of the excited state within the discharge lamp tube and the restriking voltage is inversely proportional.

If the excited state is maintained sufficiently, the restriking voltage can be low. However, if the firing angle is increased by controlling the phase of the triac, the rest period becomes longer and the excitation state inside the tube worsens. Therefore, the dimming control of the discharge lamp could not have a range of 1 to 100%. Therefore, conventional dimming control of discharge lamps was performed using a special fluorescent lamp with a proximal conductor attached to the tube wall of the fluorescent lamp in order to expand the control range limited by the restriking voltage. However, there was a drawback that continuous dimming from 0 to 100% 1 was not possible. Furthermore, in conventional discharge lamp circuits, when the discharge lamp is turned on, the heater circuit of the filament electrode is cut off, and the discharge current flows only through a portion of the filament electrode. This was not possible due to the filament lifespan, that is, the lifespan of the discharge lamp.

Furthermore, the driving voltage for the phase control circuit for controlling the phase of the triac in the main circuit of conventional discharge lamp dimmer circuits was supplied directly from the power supply via a resistor. It had the disadvantage of causing Joule loss in the resistance and poor efficiency.

The present invention was made in view of the above-mentioned circumstances, and provides a highly efficient discharge lamp dimming circuit that can continuously dim 1 to 140% even when using an ordinary fluorescent lamp. With the goal.

To summarize this invention, a capacitor with non-linear charging characteristics is connected to both ends of a discharge lamp, the drive voltage of the phase control circuit is obtained from the high voltage of the heater winding, and the primary winding of the heater transformer is used as a power source. A first switch that connects or shorts the circuit, and in conjunction with this switch, the switch turns OFF when the primary winding is connected to the power supply, and turns ON when the first switch short-circuits the primary winding. and a second switch for reducing the inductance of the ballast connected in series with the discharge lamp.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a discharge lamp dimming circuit according to an embodiment of the present invention.

In the figure, terminals a and b are terminals that are connected to a commercial power source via a power switch (not shown), and are connected to the 100V primary winding of a heater transformer 1 via a switch S1. , triac 3, stabilizer 4
Switch S is also connected in series with VC.
1 has a contact A connected to the terminal alc and a contact B connected to the terminal B. Normally, the contact B is set. - Also, a switch S2, which is linked to the switch 51, is connected to the center tap of the ballast 4 and to one filament electrode of the fluorescent lamp 2.

The secondary side of the heater transformer l has two heater windings of several volts each connected to a filament electrode of the fluorescent lamp 2. These heater windings are connected via a non-linear charging characteristic capacitor 5, and a phase control circuit 7 is connected between this connection point and the gate terminal of the triac 3 via a resistor 6. ing.

Here, the phase control circuit 7 will be explained. An input terminal c1d of the diode bridge 71 is connected to the resistor 6 and the gate terminal of the triac 3, respectively. Output terminal e, fH
/recon control element 72 (hereinafter referred to as SCR)
), series-connected resistors 73 and 74, and variable resistor 75 having a variable center tap are connected in parallel. The base terminal of the transistor 76 is connected to the connection point of the resistors 73 and 74, and the emitter terminal is connected to the variable resistor 7 via the resistor 77.
The center tap of 5CR72 and the collector terminal are respectively connected to the gate terminal of 5CR72. In addition, the output terminal e11111 of the diode bridge 71 has a 5CR72
A gate current adjustment resistor 79 connected to the gate terminal of
and a capacitor 78 connected to the emitter terminal of the transistor 76.

Next, the operation of the discharge lamp dimming circuit having the above configuration will be explained.

First, before lighting, the interlocking switches S1 and S2 are set so that Sl is turned on to the contact A side and S2 is turned off. Next, a power switch (not shown) is turned on, and terminals a and b [10
When a commercial frequency voltage of 0V is applied, heater transformer 1
A current flows through the filament electrode of the fluorescent lamp 2, inducing a voltage in the two heater windings on the secondary side of the lamp. At the same time, a drive voltage is also applied to the phase control circuit 7 via the resistor 6. A part of the current from the output terminal f of the diode bridge 71 is divided by the midpoint tap of the variable resistor 75.
' and a resistor 77 to charge a capacitor 78. As the charging of the capacitor 78 progresses and becomes approximately greater than the voltage across the resistor 73, the transistor 76 is immediately turned on and the charge stored in the capacitor 781C is discharged through the emitter and collector of the transistor 76 as the gate current of the 5CR 72. Note that the charging speed of the charging voltage of the capacitor 78 is determined by the position of the midpoint tap of the variable resistor 75. If you move the center tap to the right, capacitor 78
The amount of current charged increases, and moving the center tap to the left decreases the same amount of current. That is, the charge stored in the capacitor 78Vc is determined by the capacitance C of the capacitor 78 and a time constant determined by the sum of the resistor 75 and the resistor 77 divided by the center tap.

When the gate current flows as described above, the anode and talker nodes of the 5CR72 are turned on, and the output terminals e%f of the diode bridge are short-circuited. This causes a current to flow from the input terminal d of the diode bridge 710 to the gate of the triac 3.

On the other hand, the non-linear charging characteristic capacitor 5 connected between both heater windings has a steep charging/discharging current characteristic around about 80V, as shown in FIG. Therefore, when a gate current flows through the triac 8, approximately 8
Current flows for a short period of time through the triac 3 and the ballast 4 until it is charged to about 0V. However, capacitor 5 is about 80
When charged to about V, the current (charging current) suddenly drops to zero. This current change generates a kick voltage across the ballast 4, which causes the fluorescent 2 to ignite.

The fluorescent lamp 2 is thus started with the kick voltage produced by the ballast 4 and is lit for half a cycle with the mains voltage at the firing angle determined by the position of the midpoint tap of the variable resistor 75.

Even in the next half cycle when the polarity of the utility power is reversed,
The fluorescent lamp is re-ignited by repeating the same operation as above. That is, the triac 3 is turned on at the firing angle determined by the position of the center tap of the variable resistor 75, and at the same time the capacitor 5 is rapidly charged to about 80 V r, and immediately after charging, a kick voltage is applied to the fluorescent device 2. applied and re-ignited.

By repeating the above operation, the lamp is re-ignited every half cycle by the action of the capacitor 5 and the ballast 40, and the lighting is maintained. Therefore, even if the firing angle is delayed sufficiently by the phase control circuit 7, failure to re-ignite is prevented, and the brightness is continuously adjusted from 0 to 100.
Can be dimmed up to %.

Next, the operation when performing dimming exceeding 100% will be described.

1. Lighting of the fluorescent device 2 is performed at 100% or less to ensure an excited state within the tube of the fluorescent device 2. And interlocking switch SL
Turn on the contact B side, and turn S on the contact B side. Then, the inductance of the ballast 4 decreases, and there is an increase in the discharge current corresponding to the decrease. That is, by this increase, the brightness of the fluorescent device 2 can be made approximately 140%. In this example, the midpoint tap of the ballast 4 was set at a fixed midpoint tap so that the brightness of the discharge lamp 2 was approximately 140%, but an inductor with a variable midpoint tap such as Slydac etc. If so, the brightness can be adjusted continuously from 100% to 140%.

By the way, even if the discharge current increases and the fluorescent device 2 becomes brighter as described above, the heater transformer 1 on the negative side is connected to the switch S! The heater circuit on the secondary side is connected only by the connection to the contact B side. Therefore, the discharge current that reaches the filament electrode is split into two parts from the middle of the filament electrode, joins together through the heater winding, and returns to the power source. Therefore, current flows through the filament electrode over its entire length. The impedance of the secondary winding at this time is very small because the - secondary winding is short-circuited. As a result, the discharge current does not decrease, and moreover,
Even if a discharge of about 40% is performed, the discharge current flows through the entire filament and then merges, so overheating of the filament can be prevented and deterioration of the fluorescent device can be prevented.

FIG. 3 is a circuit diagram of a multi-discharge lamp dimmer circuit according to another embodiment of the present invention. The same or corresponding parts shown in FIG. 1 are given the same numbers.

In the illustration, the heater transformer I has a capacity sufficient to supply power to a plurality of fluorescent devices, and a plurality of fluorescent devices 6 are connected to both heater windings on the secondary side or II. A non-linear charging characteristic capacitor 5 is connected between both filament electrodes of the plurality of fluorescent lamps 2, respectively. Terminal a and one filament electrode of each fluorescent lamp 2 are connected via a triac 3. Terminal and each fluorescent light 2
The other filament electrodes are connected via ballasts 4 each having a center tap. In the above embodiment, an interlocking switch Sl is provided on the primary side of the heater transformer 1, and a switch S, which operates in the opposite direction in conjunction with the S switch, is provided between the heater winding on the secondary side and the center tap of the ballast 4. are connected in the same way. Further, a switch S+ [an interlocking switch S3 is connected between both terminals of the triac 3. Further, one connection point of the non-linear charging characteristic capacitor 5 is connected to a triac 3 via a resistor 6 and a phase control circuit 7.
connected to the gate terminal of

To explain the operation, first, the variable resistor 75 of the phase control circuit 7
The firing angle of the Tora Rin Asoku 3 is determined by adjusting the . When triac 3 turns on, each capacitor 5 simultaneously -
is charged, and subsequently a kick voltage is generated across each ballast 4, and the kick voltage lights up each fluorescent lamp 2 all at once. Thereafter, the light is dimmed at the firing angle determined by the phase control circuit 7 while repeating restriking by the same operation as described above every half cycle.

Dimming over 100% is performed by turning on the fluorescent lamp 2 at 100% or less, then turning the interlocking switch S1 to the contact B side, turning on the switch S2, and turning on the switch S1.

Although a 100V fluorescent lamp was used in the first embodiment, a 200V fluorescent lamp may also be used, and the rated capacity of each element such as a heater transformer may be increased accordingly. Furthermore, although a fluorescent lamp was used as the discharge lamp in this example,
The same method can be applied to other discharge lamps such as mercury lamps.

Also, the ON/OFF of interlocking switches S, S, Ss
Operation means ON and OFF of the main circuit, and by applying a relay circuit etc., interlocking swing f Ss,
"The main circuit can also be turned on and off by reversing the ON and OFF states of S2 and S8.

As described above, according to the present invention, the discharge lamp is surely re-ignited every half cycle by utilizing the steep charging/discharging current characteristics of the capacitor with non-linear charging characteristics, so that the re-ignition voltage of the discharge lamp is This problem has been solved and the light can be adjusted continuously from 0 to 100%. Further, even in dimming of about 100 to 140%, the discharge current is not biased toward a portion of the filament electrode, so the life of the discharge lamp is not shortened. Moreover, during o-too% dimming, the drive voltage of the phase control circuit that controls the triac in the main circuit is supplied from the secondary side of the heater transformer, which has the advantage of reducing power loss and improving efficiency. be.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a single-lamp discharge lamp dimmer circuit according to an embodiment of the present invention, FIG. 2 is a diagram of a voltage-current curve of a capacitor with non-linear charge/discharge characteristics, and FIG. 3 is a diagram of another embodiment of the present invention. FIG. 2 is a circuit diagram of a multi-discharge lamp dimming circuit according to an embodiment. ■...Heater transformer, 2...Fluorescent lamp, 3...-
Bidirectional 3-terminal thyristor (TRIAC) 4... Ballast, 5... Non-linear charging characteristic capacitor, 7... Phase control circuit. Applicant Kuroi Electric Co., Ltd. Agent Patent Attorney Hisao Komori

Claims (1)

[Claims] (1) In a discharge lamp circuit in which the filament of a discharge lamp is heated by two heater windings on the secondary side of a heater transformer and dimmed by phase control, a capacitor with nonlinear charging characteristics is connected to both ends of the discharge lamp, and a A first circuit that derives the drive voltage of the control circuit from the heater voltage of the heater winding and connects or shorts the primary winding of the heater transformer to a power source.
and a switch in conjunction with this switch, which is turned OFF when the primary winding is connected to the power supply, and turned ON when the first switch short-circuits the primary winding, and is connected in series with the discharge lamp. and a second switch for reducing the inductance of the ballast.