JPS6314480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a dimming circuit in a discharge lamp lighting device.

In a lighting device for a high-pressure vapor pressure discharge lamp, a subtidal yoke is inserted in series with the main yoke, and a triax (bidirectional three-terminal thyristor) circuit connected in parallel or a three-terminal thyristor circuit connected in anti-parallel is provided to the subtidal yoke. There are some devices that perform dimming by controlling the firing phase of a triax or thyristor. Figure 1 shows its basic circuit configuration. Main channel 1, sub channel 2, and discharge lamp 3 are connected in series, and power source 4 is connected to this series circuit.
is now connected, and subti yoke 2
A triax 5 is connected in parallel to the triax 5, and the gate terminal 5a of the triax 5 is supplied with the output of a control circuit 6. The primary coil 7a of the transformer 7 of the control circuit 6 is connected to the power source 4 in series with the dimmer switch 8. Here, when the dimmer switch 8 is open, the triax 5 does not ignite, so the sub yoke 2 is inserted and the discharge lamp 3 lights up in a dimmed state, but when the dimmer switch 8 is closed, the gate of the triax 5 is turned on. The output of the control circuit 6 is applied to the terminal 5a, the triax 5 becomes conductive, and the sub-choke 2 is short-circuited, so that the discharge lamp 3 is 100% lit only by the main chain-yoke 1. The discharge lamp 3 can be dimmed by opening and closing, but since this configuration uses stepwise dimming, the tube voltage changes instantaneously during dimming, making the lighting state of the discharge lamp 3 unstable. There is a higher possibility that flickering or fading may occur over time.
There was a problem that the product value decreased.

The present invention was made with the aim of solving the problems with the conventional devices as described above, and it is possible to avoid instantaneous changes in the phase of the pulse signal that controls the triax during stepwise dimming operation. By providing a delay circuit that changes over a certain period of time, a discharge lamp lighting device is provided which prevents sudden changes in tube voltage due to dimming operation and does not cause flickering or turning off.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the configuration of a basic circuit example of the present invention, in which a series circuit of a main chain yoke 1, a subtire yoke 2, and a discharge lamp 3 is connected to a power source 4, and a triax 5 is connected in parallel to the subtire yoke 2. It is connected to the. 11 is a pulse generator that sends an ignition pulse to the gate terminal 5a of the triax 5;
12 is a phase shift circuit 12a consisting of a resistor and a capacitor.
and a reference voltage generating section 13 consisting of a rectifier circuit 20b.
is a tube voltage detection section having a delay circuit 13a,
The dimmer switch 8 is connected in parallel to a resistor R ₁ which together with a capacitor C ₁ constitutes a delay circuit 13a. The tube voltage detection section 13 has a comparison circuit between the output voltage of the reference voltage generation section 12 and the tube voltage, and the output voltage Vb of the reference voltage generation section 12 is applied to the base of the transistor Tr ₁ via the resistor R ₂ . becomes a full-wave rectified waveform as shown in Fig. 3, and the tube voltage _Vl is converted to direct current through the transformer 7 and the rectifier circuit 13b, and then through the constant voltage diode D to the resistor _R1 and the capacitor.
The voltage Va divided by _C1 becomes a DC voltage as shown in Figure 3. During the period when Va>Vb, the transistors Tr ₁ and Tr ₂ of the pulse generator 11 are turned off as shown in waveform A in FIG. 3, and the resistance of the pulse generator 11 is
The circuit of R ₃ and the capacitor C ₂ is charged by the DC voltage E ₁ obtained by rectifying the voltage of the secondary coil 1a of the main chain 1 by the rectifier circuit 11a, and the terminal voltage Vc of the capacitor C ₂ is as shown in FIG. As shown in Figure 2, the charge gradually rises along the charging curve B of the circuit of resistor _R3 and capacitor _C2 . On the other hand, programmable union transistor (PUT) (hereinafter simply referred to as
(referred to as PUT) is the control voltage of the voltage E ₁ and the resistances R ₄ and R ₅
Since the voltage is divided by the voltage Vp (=E ₁ ×R ₄ /R ₄ +R ₅ ), PUT is turned on at time t ₃ when Vc > Vp, and the voltage is applied to the gate terminal 5a of the triac 5 via the control transformer Tp. A trigger pulse shown as Ip in FIG. 3 is sent and triac 5 is fired. Now, for example, if the power supply voltage increases for some reason, the voltage Vb
increases, the phase angle at which the trigger pulse Ip is generated increases, and time _t3 is delayed, so the ignition of the triax 5 is delayed and the input to the discharge lamp 3 is suppressed. Furthermore, if the tube current of the discharge lamp 3 increases due to fluctuations in the power supply voltage or waveform distortion, for example, the voltage
Since E ₁ and therefore the voltage Vp increase, time t ₃ is delayed and the input to the discharge lamp 3 is suppressed, and the input to the discharge lamp 3 is kept constant.

In this device, the dimming of the discharge lamp 3 is performed by changing the voltage division ratio in the tube voltage detection section 13.
That is, when the dimmer switch 8 is closed, the resistance R ₁
The capacitor is shorted and the voltage division ratio increases.
The phase of time t ₃ advances when the voltage Va of C ₁ rises and transistors Tr ₁ and Tr ₂ are turned off, and accordingly, the time when the voltage Vc of capacitor C ₂ becomes larger than the voltage Vp.
The phase of _t3 also advances, the ignition phase of the triac 5 advances, and the input to the discharge lamp 3 increases, resulting in a state of 100% lighting without dimming. Moreover, when the dimmer switch 8 is opened, the output of the discharge lamp 3 decreases due to the reverse operation and enters the dimming state, but the tube voltage
Since Vl cannot change suddenly and rather increases transiently, a resistor R ₁ is used to detect and divide this voltage.
Even if the voltage division ratio of capacitor _C1 is reduced, the phase angle does not reach the final value in the dimming state immediately. Furthermore, since the resistor R ₁ and the capacitor C ₁ constitute the delay circuit 13a, the change in the tube voltage V _l is not instantaneously transmitted to the pulse generator ₁₁ , and the change in the tube voltage V l is not instantaneously transmitted to the pulse generator ₁₁ , and the change in the tube voltage V l is The phase at time _t3 gradually lags over a predetermined period of time, for example, a period T of several tens of cycles, and reaches the final phase. Figure 4 shows this state. When the tube voltage V _l changes as shown in figure a, in the conventional example the output of the discharge lamp 3 changes rapidly as shown in figure b, but in this basic example , it changes smoothly as shown in c in the figure, and the time constant of C ₁ R ₁ should be selected to be sufficiently large for the period T.

In this embodiment, as mentioned above, the phase of the pulse signal that controls the triax 5 is set such that the second half of every half cycle of the reference voltage, which is a certain phase ahead of the power supply voltage, is lower than the voltage obtained by dividing the tube voltage and rectifying and smoothing it. The phase delay of this pulse signal is not changed instantaneously by the dimming operation, but is gradually changed within a preset fixed period T. This prevents the discharge lamp from flickering or turning off due to sudden changes, and allows stable and good dimming at all times.

FIG. 5 shows a delay circuit according to an embodiment of the present invention, in which the dimmer switch 8 is closed and set to the dimming state, the transistor Tr 1 is turned on, and the transistor Tr ₁ is turned on.
Time t _b when T ₂ is turned off and charges the circuit of resistor R ₆ and capacitor C ₃ , and capacitor C ₂ is charged to the divided voltage by the parallel circuit of resistors R ₅ and R ₆ and resistor R ₄ .
, the transistor _T1 is turned off, the dimmer switch 8 is opened and set to the non-dimmer state, and the transistor T1 is turned off.
When _T2 is turned on, the circuit of capacitor _C3 and resistor _R6 is discharged, and the voltage of capacitor _C3 is changed to the resistors _R5 and _R4.
By appropriately selecting the phase between the time t _a when the voltage drops to the divided voltage of 100% and the lighting becomes 100% by turning on and off the transistors T ₁ and T ₂ , the discharge lamp input voltage can be changed as shown in Figure 4. Preventing sudden changes,
This is designed to eliminate the flickering and fading of discharge lamps.

Note that the transistors T ₁ and T ₂ are controlled by turning the dimmer switch 8 on and off so that when the dimmer switch 8 is turned on, the transistor T ₁ is turned on and the transistor T ₂ is turned off. In addition, when the dimmer switch 8 is turned off, the transistor _T1 is turned off and the transistor _T2 is turned on.This control circuit can be easily realized using a general circuit equipped with an inverting circuit. . In addition, the delay circuit output (output voltage E ₁ , E ₂ ) of the delay circuit
is applied to the same points as in the basic example of FIG. 2, and the other circuit configurations are the same as in the basic example of FIG.
However, the dimmer switch 8 and the resistor connected in parallel to the resistor R ₁ in FIG. 2 are unnecessary, and the dimmer switch 8 is provided in the control circuit of the transistors T ₁ and T ₂ .

In the above embodiment, if the discharge lamp is started in a dimmed state, the starting current may decrease and it may take time to start, but it is important to appropriately select the value of the constant voltage diode D of the tube voltage detection unit 13. This can prevent a decrease in current at the initial stage of startup. Figure 6 explains this relationship, where Vb' is the reference voltage with a delayed phase, and E ₂ is the _voltage of the constant voltage diode D. Since _the starting phase _{t s ′ of}
Since transistor Tr ₂ turns on first and emits a pulse before turning on, there is no difference in the current phase at the time of starting, even when dimming and when lighting at 100%, and the tube voltage of the discharge lamp remains constant. Until this value is reached, the phase of the pulse signal that controls the triac is maintained at the non-dimming phase, allowing for a good start even in dimming mode.

As described above, the present invention involves inserting a subtire yoke in series with the main yoke inserted into the lighting circuit of a high vapor pressure discharge lamp, and providing a triax circuit connected in parallel to the subtire yoke to control the firing phase of the triac. In a discharge lamp lighting device that performs dimming by dimming, a delay circuit is installed that changes the phase of the pulse signal that controls the triack over a certain period of time instead of changing it instantaneously during stepwise dimming operation. The phase of the pulse signal that controls the tri-attack is kept at the phase of the non-dimming state until the tube voltage of the discharge lamp reaches a certain value when starting in the dimming state. This has the effect that the tube voltage is prevented from changing suddenly even when the operation is performed, and that it is possible to perform dimming while maintaining a stable lighting condition without flickering or turning off during dimming. Even when the discharge lamp is started in a dimmed state, a predetermined starting current flows and the discharge lamp is reliably started, and the starting time is not increased.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional example, Fig. 2 is a circuit diagram of a basic example of the present invention, Figs. 3 and 4 are explanatory diagrams of the same operation, and Fig. 5a is a circuit diagram of an embodiment of the same. , FIG. 5b is an explanatory diagram of the same operation, and FIGS. 6a and 6b are explanatory diagrams of the same operation. 1 is the main chain yoke, 2 is the subtire yoke, 3 is the discharge lamp, 5 is the triax, 8 is the dimmer switch,
11 is a pulse generator, 12 is a reference voltage generator, 1
3 is a tube voltage detection section, and 13a is a delay circuit.

Claims (1)

[Claims] 1 A subtire yoke is inserted in series with the main chain yoke inserted in the lighting circuit of a high vapor pressure discharge lamp, a triax circuit is connected in parallel to the subtire yoke, and dimming is performed by controlling the firing phase of the triax. In such a discharge lamp lighting device, a delay circuit is provided that changes the phase of the pulse signal that controls the triact during stepwise dimming operation over a certain period of time, rather than changing it instantaneously. 1. A discharge lamp lighting device characterized in that the phase of a pulse signal for controlling a triass is maintained at a non-dimming state until the tube voltage of the discharge lamp reaches a certain value at the time of starting.