JPH0331040Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field This invention relates to a discharge lamp lighting device in which light is controlled by a switching element for controlling flow angle, such as a thyristor.

(b) Prior art and its disadvantages The general method for dimming a discharge lamp is to connect a switching element such as a bidirectional three-terminal thyristor in series to the power supply side of the discharge lamp to control the flow angle of the power supply voltage. This is how it was done. However, a conventional discharge lamp lighting device using such a switching element has a problem in that the discharge lamp is difficult to start when the power is turned on with the dimming state set to a deep level. This is because the voltage application time to the discharge lamp is short and the filament is not sufficiently preheated. In order to solve this problem, circuits have conventionally been configured so that the light is in a fully lit state with no dimming for several seconds immediately after the power is turned on. FIG. 3 shows a circuit diagram of such a conventional discharge lamp dimming device. In the figure, 1 is a discharge lamp, 2 is a bidirectional three-terminal thyristor (hereinafter referred to as a TRIAT), 3 is a timer circuit, and 51 and 52 are phase control circuits. In the state where normal dimming is possible, the phase control circuit 5
The gate of the triac 2 is controlled by the output of the triac 2, and immediately after the power is turned on, the gate of the triac 2 is controlled by the phase control circuit 51. That is, the time constant of the phase control circuit 51 is set to be small, and the on timing is determined by the time constant of the phase control circuit 51 regardless of the value of the variable resistance of the phase control circuit 52. A few seconds after power is turned on, the timer circuit 3 acts to substantially short-circuit P1 and P2, and the phase control circuit 51 becomes ineffective. Therefore, after that, the phase control circuit 52 can arbitrarily perform dimming. In such a conventional discharge lamp lighting device, it is necessary to sufficiently preheat the filament by reducing the time constant of the phase control circuit 51, but in order to stabilize the trigger of the switching circuit, the capacitance of the capacitor must be increased. cannot be made very small, and since the upper limit of the gate current of the switching circuit is regulated, the resistance cannot be made very small. As a result, it was not possible to reduce the non-conduction angle of the switching circuit at startup to a certain level. Another drawback was that two trigger elements were required.

(c) Purpose of the invention This invention eliminates the above-mentioned conventional drawbacks, and provides a discharge lamp that makes it possible to extremely reduce the non-conduction angle of the switching circuit when starting the discharge lamp, and to use a single trigger element. The purpose of the present invention is to provide a lighting device.

(d) Structure and effect of the invention In summary, this invention connects in series a capacitor with a relatively large capacitance and a second capacitor with a small capacitance in series with a starting resistor of low resistance, and connects the starting resistor and the second capacitor in series. A dimming variable resistor is connected in parallel to the series circuit of the first capacitor,
Furthermore, a timer circuit is connected in parallel to the series circuit of the first and second capacitors.

According to this invention, when the timer circuit is activated, the switching element is controlled by a time constant circuit consisting essentially of the starting resistor and the first and second capacitors in series, so that the non-conduction angle can be made extremely small. can do. Further, when the timer circuit is activated, the first and second capacitors are connected in parallel, so that conventional dimming can be performed. Furthermore, since the signal to be output to the switching circuit can be extracted from the same point regardless of the state of the timer, a single trigger element is required.

(e) Embodiment FIG. 1 is a circuit diagram of a discharge lamp lighting device which is an embodiment of this invention. The discharge lamp 1 is connected in series to a commercial power source 6 together with a ballast (choke coil) L and a triax 2 which is a switching circuit. A phase control circuit 5 controls the gate of the triac 2 via the trigger element 4. 3 is a timer circuit, and for a few seconds immediately after the power is turned on, P1,
P2 is in a high impedance state. After a few seconds, P1 and P2 are substantially short-circuited.

The phase control circuit 5 is a starting resistor R with relatively low resistance.
A first capacitor C1 with a relatively large capacity and a capacitor C2 with a small capacity are connected in series, and a variable resistor VR for dimming is connected in parallel to the series circuit of the starting resistor and the first capacitor. It is connected. Furthermore, the timer circuit is connected in parallel to the circuit in series with the first and second capacitors. Therefore, for several seconds immediately after power is turned on, a time constant circuit is formed by a series circuit of resistor R1 and capacitors C1 and C2. In this case, since the resistor R1 has a low resistance and the capacitor C2 has a small capacity, the time constant is small and the triac 2 can be turned on at a very fast timing. That is, if the charging voltage of capacitor C2 exceeds the switching voltage of trigger element 4, the charge on capacitor C2 causes trigger element 4 to conduct, but is insufficient to turn on the triac. However, since the capacitance of the capacitor C1 is large, a series circuit of the resistor R1 and the capacitor C1 connects the triac 2.
A sufficient gate current can be passed through the gate of the Therefore, the switching circuit can operate stably. Furthermore, even if the value of the resistor R1 is small, the gate current is limited to the current required to charge the capacitor C1. In addition, C1, C2, R
1. VR is, for example, 0.1μF, 0.022μF, 1.8kΩ, 50k
It is Ω.

A few seconds after the power is turned on, the timer circuit 3 is activated, and P1 and P2 are substantially short-circuited. FIG. 2 shows the configuration of the phase control circuit in this case. As is clear from the figure, capacitors C1 and C2 are connected in parallel to form a series circuit with variable resistor VR for dimming. Since the capacitor C2 has a large capacity, the time constant is substantially determined by the values of the variable resistor VR and the capacitor C2. In this case, the charging voltage of capacitors C1 and C2 is applied to trigger element 4.
If the switching voltage of capacitor C1 is exceeded,
The charge on C2 and C2 is discharged to the gate of the triac and is sufficient to turn on the triac. In addition, the above operation explanation is based on the T of the triack.
Although the explanation has been made assuming that the two terminals are at positive potential, if the two terminals are in opposite phases, the directions of charging and discharging the capacitor will of course be reversed.

In the timer circuit 3, D is a diode bridge, which rectifies P1 and P2 as input,
Outputs positive voltage to P3. A time constant circuit is constructed by capacitor C3 and resistor R2, and its output is
Connected to the PUT gate. Therefore, immediately after the power is turned on, PUT is in the off state and capacitor C
When a certain amount of charge accumulates in step 3 and the gate voltage of PUT decreases, PUT turns on. LED is P3
It is inserted to apply a reverse bias between the anodes of PUT, and when PUT is turned on, P1 and P2 are substantially short-circuited by this LED and PUT. Note that the LED also serves as an indicator to indicate that the light is dimmable.

In FIG. 1, a resistor R0 is used to flow a tube current to keep the excitation state of the discharge lamp constant when the triac 2 is off, and a capacitor C0 is a noise prevention capacitor.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a discharge lamp lighting device that is an embodiment of this invention, Figure 2 is an equivalent circuit diagram of a phase control circuit when the timer circuit is in an inactive state, and Figure 3 is an equivalent circuit diagram of a phase control circuit when the timer circuit is in an inactive state.
The figures each show a circuit diagram of a conventional discharge lamp lighting device.

Claims (1)

[Claim for Utility Model Registration] A bidirectional three-terminal thyristor connected in series with a discharge lamp, a timer circuit that is activated for a certain period of time immediately after power is turned on and maintains both ends at high impedance, and a timer circuit connected in series to the gate of the thyristor. a trigger element connected to the trigger element, a starting resistor for turning on the trigger element at an early phase when the timer circuit is activated, and a variable resistor for turning the trigger element on at a predetermined phase when the timer circuit is not activated. In the device comprising a control circuit, a first capacitor with a relatively large capacitance and a second capacitor with a small capacitance are connected in series with the starting resistor, and the starting resistor and the first capacitor are connected in series. A discharge lamp lighting device characterized in that the variable resistor is connected in parallel to a series circuit, and the timer circuit is further connected in parallel to the series circuit of the first and second capacitors.