JPH0328040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp dimming control circuit using a bi-directional three-terminal thyristor (hereinafter referred to as a thyristor), and in particular to a dimming control circuit for a discharge lamp using an interlocking switch. This invention relates to improvement of a discharge lamp dimming circuit that expands the dimming range.

Dimming a discharge lamp, even if the dimming range is from 0 to 100%, is as simple as lowering the voltage applied to the discharge lamp by controlling the phase of the main circuit's triax, just as when using an incandescent light bulb as a load. This cannot be done through 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 triax, the rest period becomes longer and the excitation state inside the tube worsens. Therefore, the dimming control of the discharge lamp cannot have a range of 0 to 100%. Therefore, conventional dimming control of discharge lamps was carried out using special fluorescent lamps 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, it still had the drawback that continuous dimming from 0 to 100% 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.
Dimming the discharge lamp over a range exceeding 100% was not possible from the viewpoint of the filament life, that is, the life of the discharge lamp.

Furthermore, the driving voltage of the phase control circuit for controlling the phase of the tri-attack in the main circuit of the conventional discharge lamp dimmer circuit was supplied directly from the power supply through the resistor. The drawback was that it caused a Joule loss in the resistance and was low in efficiency.

This invention was made in view of the above-mentioned circumstances, and even when using ordinary fluorescent lamps, it can continuously achieve 0 to 140%.
The purpose of the present invention is to provide a discharge lamp dimmer circuit which is capable of dimming to a certain extent and is efficient.

To summarize this invention, a capacitor with non-linear charging characteristics is connected to both ends of a discharge lamp, a driving voltage of a phase control circuit is obtained from a heater voltage of a heater winding, and a primary winding of a heater transformer is connected to a power source. Alternatively, the first switch to short-circuit, and the switch is turned OFF when the primary winding is connected to the power supply, and the first switch is turned ON and released when the primary winding is short-circuited. 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. ,
The triax 3 and the stabilizer 4 are also connected in series. The switch _S1 has a contact A connected to a terminal a and a contact B connected to a terminal b, and the contact B is normally set. Further, a switch S ₂ interlocked with the switch S ₁ is connected to the center tap of the ballast 4 and one filament electrode of the fluorescent lamp 2. The secondary side of the heater transformer 1 has two heater windings of several volts each connected to a filament electrode of a 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 triax 3 via a resistor 6. ing.

Here, the phase control circuit 7 will be explained. Input terminals c and d of the diode bridge 71 are connected to the resistor 6 and the gate terminal of the triac 3, respectively. A silicon control element 72 is connected to the output terminals e and f.
(hereinafter, this control element will be referred to as SCR), series-connected resistors 73 and 74, and a variable resistor 75 having a variable center point tap are connected in parallel. The pace terminal of the transistor 76 is connected to the connection point of the resistors 73 and 74, the emitter terminal is connected to the midpoint tap of the variable resistor 75 via the resistor 77, and the collector terminal is connected to the SCR7.
They are connected to the gate terminals of No. 2 and 2, respectively. Furthermore, a gate current adjustment resistor 79 connected to the gate terminal of the SCR 72 and a capacitor 78 connected to the emitter terminal of the transistor 76 are connected to the e side of the output terminal of the diode bridge 71.

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

First, before lighting, the interlocking switches S ₁ and S ₂ are set so that S ₁ is set to the contact A side and S ₂ is set to OFF. Next, when a power switch (not shown) is turned on and a commercial frequency voltage of 100V is applied to the a and b terminals, voltage is induced in the two heater windings on the secondary side of the heater transformer 1, and the fluorescent lamp A current flows through the second filament electrode. At the same time, a drive voltage is also applied to the phase control circuit 7 via the resistor 6. A portion of the current from the output terminal f of the diode bridge 71 charges the capacitor 78 through the resistor 75 and the resistor 77, which are divided by the tap at the center of the variable resistor 75. As the charging of the capacitor 78 progresses and becomes almost higher than the voltage across the resistor 73, the transistor 76 is immediately turned on and the charge stored in the capacitor 78 is transferred via the emitter and collector of the transistor 76.
It is discharged as the gate current of SCR72. In addition,
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. Moving the center tap to the right increases the amount of current that charges the capacitor 78, and moving the center tap to the left decreases the same amount of current. That is, the charge stored in the capacitor 78 is determined by the time constant determined by the capacitance c of the capacitor 78 and the total value R of the resistor 75' and the resistor 77 divided by the midpoint tap.

When the gate current flows as above, SCR7
The anode and cathode of No. 2 are turned on, and the output terminals e and f of the diode bridge are short-circuited. This causes a current to flow from the input terminal d of the diode bridge 71 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 voltage of approximately 80 V as shown in FIG.
It has steep charge/discharge current characteristics centered around . Therefore, when a gate current flows through the triax 3, the current flows for a short period of time through the triax 3 and the ballast 4 until the capacitor 5 is charged to about 80V. However, when the capacitor 5 is charged to about 80V, its current (charging current) suddenly drops to zero. This current change generates a kick voltage across the ballast 4, which causes the fluorescent lamp 2 to ignite. The fluorescent lamp 2 is thus started with the kick voltage generated by the ballast 4, and for half a cycle the fluorescent lamp 2 is
5. Lights at commercial voltage with firing angle determined by the position of the center tap.

In the next half cycle when the polarity of the commercial power source is reversed, the same operation as described above is repeated to restart the fluorescent lamp. That is, the trigger 3 is activated at the firing angle determined by the position of the midpoint tap of the variable resistor 75.
At the same time as turns on, capacitor 5 becomes approximately 80V.
The fluorescent lamp 2 is charged immediately after charging.
A kick voltage is applied to the lamp to re-ignite it.

By repeating the above operation, the lamp is re-ignited every half cycle by the action of the capacitor 5 and the ballast 4, and the lighting is maintained. Therefore, even if the firing angle is delayed sufficiently by the phase control circuit 7, failure to restart is prevented.
The brightness can be adjusted continuously from 0 to 100%.

Next, we will discuss the operation when performing dimming exceeding 100%.

First, the fluorescent lamp 2 is turned on at 100% or less to ensure an excited state inside the tube of the fluorescent lamp 2. Then, switch interlock switch _S1 to contact B side and switch _S2 to ON. Then, the inductance of the ballast 4 decreases, and there is an increase in the discharge current corresponding to the decrease. In other words, this increase increases the brightness of fluorescent lamp 2.
It can be set to about 140%. In this embodiment, 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 a slider may be used. The brightness can be adjusted continuously from 100% to 140%.

By the way, even if the discharge current increases and the phosphor 2 becomes brighter as described above, the heater transformer 1 on the primary side is only cut off by the connection to the contact B side of the switch S ₁ , and the secondary side becomes brighter. The heater circuit is connected. Therefore, the discharge current that reaches the filament electrode is split into two parts from the middle of the filament electrode, joins 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 primary winding is short-circuited. As a result, the discharge current does not decrease, and even if the discharge is about 140%, the discharge current flows through the entire filament and then merges, which prevents the filament from overheating and prevents deterioration of the fluorescent lamp. I can do it.

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 figure, a heater transformer 1 has a capacity sufficient to supply power to a plurality of fluorescent lamps, and a plurality of fluorescent lamps 2 are connected to both heater windings on the secondary side. Each of the filament electrodes of the plurality of fluorescent lamps 2 has a non-linear charging characteristic capacitor 5.
is connected. Terminal a and one filament electrode of each fluorescent lamp 2 are connected via a triax 3. Terminal b and the other filament electrode of each fluorescent lamp 2 are connected via a ballast 4 each having a center tap. An interlocking switch S ₁ is installed on the primary side of the heater transformer 1, and an interlocking switch S ₁ is connected between the heater winding on the secondary side and the midpoint tap of the ballast 4.
A switch _S2 which operates in conjunction with and in the opposite direction is connected in the same way as in the previous embodiment. Further, a switch _S3 , which is linked to the switch _S1 , is connected between both terminals of the triac 3. Further, one connection point of the non-linear charging characteristic capacitor 5 is connected to the gate terminal of the triac 3 via a resistor 6 and a phase control circuit 7.

To explain the operation, first, the variable resistor 75 of the phase control circuit 7 is adjusted to determine the firing angle of the triax 3. When Triack 3 turns on,
Each capacitor 5 is charged at the same time, and then a kick voltage is generated across each ballast 4, and each fluorescent lamp 2 is turned on at the same time by the kick voltage. Thereafter, the light is dimmed at the firing angle determined by the phase control circuit 7 while repeating restriking every half cycle by the same operation as described above.

To dim over 100%, turn on fluorescent lamp 2 at 100% or less, then turn interlock switch S ₁ to contact B side.
This is done by turning switch _S2 ON and switch _S3 ON.

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 is used as the discharge lamp in this embodiment, other discharge lamps such as a mercury lamp can be used in the same manner.

In addition, the ON/OFF operation of the interlocking switches S ₁ , S ₂ , S ₃ means the ON/OFF of the main circuit, and by applying a relay circuit, etc., the interlocking switches S ₁ , S ₂ ,
Reverse ON/OFF of _S3 to turn main circuit ON/OFF
You can also have them do this.

As described above, according to the present invention, the discharge lamp can be relit every half cycle by utilizing the steep charging/discharging current characteristics of the capacitor with non-linear charging characteristics. The problem of arc voltage is solved and the light can be dimmed continuously from 0 to 100%. Also, 100
At dimming of about ~140%, the discharge current is not biased to a portion of the filament electrode, so the life of the discharge lamp is not shortened. Moreover, 0 to 100
%, the drive voltage of the phase control circuit that controls the tri-attack of the main circuit is supplied from the secondary side of the heater transformer, which has the advantage of reducing power loss and improving efficiency.

[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. 1... Heater transformer, 2... Fluorescent lamp, 3... Bidirectional 3-terminal sahastor (triax), 4... Ballast,
5...Non-linear charging characteristic capacitor, 7...Phase control circuit.

Claims (1)

[Claims] 1. In a discharge lamp circuit in which the filament of the discharge lamp is heated by two heater windings on the secondary side of a heater transformer and dimmed by phase control, a capacitor with non-linear charging characteristics is connected to both ends of the discharge lamp. At the same time, a bidirectional three-terminal switching element such as a triax connected in series with the discharge lamp is driven by the output voltage of the heater winding, and a conduction pulse is applied to the switching element at an arbitrary phase angle every half cycle of the power supply. a first switch that connects or shorts the primary winding of the heater transformer to a power source; and a first switch that connects or shorts the primary winding of the heater transformer to a power source; and a second switch that turns off and turns on when the first switch short-circuits the primary winding to reduce the inductance of a ballast connected in series with the discharge lamp. dimmer circuit.