JPH0210559B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device, and an object of the present invention is to provide a discharge lamp lighting device that can improve the lighting operation of a discharge lamp regardless of fluctuations in power supply voltage.

For example, in a discharge lamp lighting device, an ignition circuit Q is used as a pulse generation circuit B as shown in FIG. That is, when starting the discharge lamp L, a voltage is applied by the discharge lamp power supply E to the oscillation capacitor C and the ignition circuit Q via the ballast CH, and the voltage applied to the ignition circuit Q exceeds the ignition voltage V _Bp . Then, the ignition circuit Q becomes conductive for ignition, and the voltage of the capacitor C is boosted by the pulse transformer P and applied to the discharge lamp L, and the discharge lamp L is started. After starting, the discharge lamp voltage Vla is applied to the ignition circuit Q, but power supply voltage Eo > ignition voltage V _Bp > discharge lamp voltage Vla
If the relationship is set as follows, the ignition circuit Q will maintain a non-conducting state, no pulse will be generated, and stable lighting will continue.

However, in the case of the conventional circuit (Fig. 1),
When the power supply voltage Eo increases or decreases as shown in Figure 6 A,
Discharge lamp voltage Vla when lighting, ballast CH current I _CH when starting, ignition circuit Q (SSS) voltage V _Q when starting,
The waveform of the current I _Q of the ignition circuit Q (SSS) at the time of starting is:
The ignition voltage V _BO is determined by the characteristics of the ignition circuit Q, and the same
Although it is constant in SSS, there are variations between elements, and the peak voltage of power supply voltage E ₀ is equal to the ignition voltage V _BO
Below that, pulses will no longer be output. Since the conventional ignition circuit Q is composed of a symmetrical switching element SSS, its ignition voltage V _Bp is determined by the switching element SSS and cannot be set arbitrarily, and it cannot be set by applying a signal from outside. ignition voltage
It was also not possible to vary V _BP . Therefore, for example, in the case of a discharge lamp lighting device, even when the power supply voltage Eo fluctuates, it may not be possible to obtain an ignition circuit with an ignition voltage V _Bp that satisfies the above condition Eo > V _Bp > Vla. In some cases, the discharge lamp L did not operate properly.

An object of the present invention is to provide a discharge lamp lighting device that can solve the above-mentioned problems, and is characterized in that a discharge lamp L is connected to a discharge lamp power source E via a ballast CH, and an ignition circuit Q In a discharge lamp lighting device in which a pulse generating circuit _B ' having a pulse generating circuit B' having a pulse generating circuit Q1 is connected in parallel to a discharge lamp L, the ignition circuit _Q1 is connected between a thyristor SCR and an anode and a gate of the thyristor SCR. A charging/discharging circuit CF is charged so that the anode side becomes positive, and a diode D is interposed between the gate of the thyristor SCR and the charging/discharging circuit CF so as to be in the forward direction with respect to the charging direction of the charging/discharging circuit CF. The charging/discharging circuit CF is composed of a parallel circuit of a resistor _R1 and a capacitor _C1 , and the charging/discharging circuit CF is connected to the pulse generating circuit B' in proportion to the power supply voltage _E0 of the discharge lamp power supply E. A power supply circuit F is provided which charges the _discharge lamp with a voltage of The charging voltage Vc of the capacitor _C1 of the charging/discharging circuit CF is higher than the discharge lamp voltage Vla and the power supply voltage Eo so that the discharge lamp L operates after the ballast current I _CH finishes flowing and lights up the discharge lamp L every half cycle. is set lower than the peak value of the capacitor C1 so that the charging voltage Vc of the capacitor _C1 includes a ripple synchronized with the power supply voltage Eo.
The point is that the resistance value of the resistor _R1 of the discharge circuit CF is set to be small.

Hereinafter, the present invention will be described according to the illustrated embodiment. FIG. 2 shows an embodiment of the present invention, in which _Q1 is a roll call circuit and includes a thyristor SCR. Thyristor SCR has anode A and cathode K
and a gate G, and the anode A and the gate G
In between, a charging/discharging circuit CF constituted by a parallel circuit of a resistor _R1 and a capacitor _C1 is connected via a diode D, and the anode A side of the thyristor SCR is connected to the positive side of the capacitor _C1 by a power supply circuit F. The diode D is connected in the forward direction with respect to the charging direction.

The ignition circuit Q ₁ is connected in parallel to the oscillation capacitor C _via the saturable choke CH' and the rectifier RE ₁ to constitute the pulse generation circuit B _' . It is said to be bidirectional depending on its function. The power supply voltage Eo of the discharge lamp power supply E is set to be approximately the same as the discharge lamp voltage Vla, and the pulse generating circuit B' is connected in parallel to the discharge lamp L via the capacitor C', and the voltage Vc of the capacitor _C1 is set to be approximately the same as the discharge lamp voltage Vla. When set to be lower than the peak value of the power supply voltage Eo and higher than the discharge lamp voltage Vla, the pulse generation circuit is activated every half cycle.
A high frequency voltage is applied to the discharge lamp L from B' via the capacitor C', the discharge lamp L is turned on, and the discharge is maintained so that the lamp is turned on every half cycle. In addition, the power supply circuit F that charges the charging/discharging circuit CF of the ignition circuit _Q1 is connected to a voltage regulating transformer T whose primary winding is connected to both ends of the power supply E, and a secondary winding of this voltage regulating transformer T. The charging voltage _Vc of the charging/discharging circuit CF, that is, the ignition circuit Q ₁
The ignition voltage V _Bp can be controlled in proportion to the power supply voltage Eo.

According to the configuration of the embodiment, the charge/discharge circuit CF is charged by the power supply circuit F, and the charging voltage Vc is changed by changing the output voltage of the power supply circuit F.
Can be set arbitrarily. If the voltage applied between the anode A and the cathode K of the thyristor SCR is lower than the charging voltage Vc, no current flows from the gate G to the cathode K, so the thyristor SCR
remains off. Also, anode A and cathode K
When the voltage between them becomes higher than the charging voltage Vc, a current flows between the gate G and the cathode K as a charging current for the capacitor _C1 via the diode D, and the thyristor SCR is turned on. At this time, the resistor R ₁ acts to prevent the voltage of the capacitor C ₁ from rising due to this charging current. When the thyristor SCR is turned on, the anode A, cathode K and gate G are at approximately the same voltage, the voltage of capacitor _C1 is applied to diode D, and diode D is connected to capacitor C1.
This prevents the charge of C ₁ from discharging between the anode A and the gate G. Therefore, the ignition circuit Q ₁ is an ignition circuit in which the charging voltage Vc of the charging/discharging circuit CF, which can be set arbitrarily, is set to the ignition voltage V _Bp . In addition, in the case of the circuit of the present invention (Fig. 2), when the power supply voltage Eo increases or decreases as shown in Fig. 7 A, the discharge lamp voltage Vla at the time of lighting becomes as shown in Fig. 7 B, and when starting Current in ballast CH at time I _CH , thyristor
Voltage of SCR V _SCR , current of saturable choke CH′ I _CH ′
The waveforms of are as shown in FIG. 7, C, D, and E, respectively.
The waveform of the discharge lamp voltage Vla during lighting shown in Figure 7B is determined by the characteristics of the discharge lamp L, and the discharge lamp current
The time when Ila is 0 and the time when discharge lamp voltage Vla is 0 are the same. When the power supply voltage Eo changes, the charging voltage Vc of the capacitor _C1 also changes as shown in Figure 7D.
Since Vc<Eo, the thyristor SCR is always turned on at startup, and pulses are generated from the pulse generation circuit B'. Furthermore, the charging voltage Vc of the capacitor _C1 is determined by the transformer T, so there is no variation. Since the power supply voltage Eo is approximately equal to the discharge lamp voltage Vla, the voltage applied to the ballast CH (Eo - Vla) becomes low. Therefore, fluctuations in the voltage applied to the ballast CH due to fluctuations in the power supply voltage Eo become large, and as a result, fluctuations in the current flowing through the ballast CH become large. Also, the power supply voltage
Since Eo and the discharge lamp voltage Vla are approximately equal, if the pulse generating circuit B' is not provided, even if the discharge lamp L is lit once, it cannot be kept lit. Therefore, after the discharge lamp current Ila has finished flowing, the pulse generating circuit B' is operated to start the discharge lamp L every half cycle.
That is, when the voltage Vc of the capacitor _C1 is set higher than the discharge lamp voltage Vla and lower than the peak value of the power supply voltage Eo, the pulse generation circuit B' starts to turn on from the moment the discharge lamp current Ila reaches 0, as shown in FIG. Start working,
The ballast generates pulses at both ends of the discharge lamp L.
The current flowing through CH increases. Thereafter, when the discharge lamp L is lit by a pulse, a voltage obtained by subtracting the voltage of the capacitor C' from the voltage across the discharge lamp L is applied to the pulse generation circuit B', and the pulse generation circuit B' stops its oscillation operation.

However, the current flowing through the discharge lamp L is
The current flowing to CH minus the current flowing to pulse generation circuit B' via capacitor C',
Since the current value flowing into the pulse generation circuit B' in every half cycle becomes the current value at which the discharge lamp current Ila starts flowing, when the power supply voltage Eo becomes high,
If the current flowing to the pulse generating circuit B' becomes smaller, the increase in the discharge lamp current will be relatively small. That is, the current flowing through capacitor C' is mainly determined by its capacitance, but since ignition circuit Q ₁ turns on when the ignition voltage exceeds V _Bp , the capacitor C'
As a current flows through C' and it is charged, eventually a voltage higher than the ignition voltage V _Bp is no longer applied to the ignition circuit _Q1 , and the current flowing to the pulse generation circuit B' becomes 0. When this current becomes 0, the discharge lamp L is lit, and the discharge lamp current Ila flows from the current value flowing through the pulse generating circuit B'. capacitor
If the current flowing through C′ has a constant capacity, as the ignition voltage V _Bp of the ignition circuit Q ₁ increases, the pulse voltage increases, the discharge lamp L lights up faster, and the ignition voltage _BO increases. As a result, the current flowing through the pulse generating circuit B' tends to reach 0 quickly, so when the operation of the pulse generating circuit B' stops, the current flowing through the ballast CH becomes smaller, and the discharge lamp current Ila starts to flow. As a result, the discharge lamp current Ila decreases. Since the ignition voltage V _Bp varies in proportion to the power supply voltage Eo, fluctuations in the discharge lamp current due to fluctuations in the power supply voltage Eo can be reduced. Therefore, even if the power supply voltage Eo fluctuates, the discharge lamp L can be operated satisfactorily.

Moreover, if the resistance value of the resistor R ₁ is reduced, the charging voltage Vc of the capacitor C ₁ includes a ripple synchronized with the power supply voltage Eo, and the ignition voltage V _Bp can be changed during a half cycle of the power supply voltage Eo, and the capacitor C ₁ When the current starts to flow, the ignition voltage V _Bp can be lowered, and when the current stops flowing, the ignition voltage V _Bp can be increased, so that the fluctuation of the ignition voltage V _Bp can be made particularly good. Can be done.

In the above embodiment, the pulse generation circuit B' is generated by the rebound voltage from the saturable chiyoke CH', but a pulse transformer or other circuit is used in place of the saturable chiyoke CH'.
B′ may also be configured. Furthermore, if a resistor R ₁ ' is connected between the capacitor C ₁ and the power supply circuit F as shown in Figure 4, in addition to varying the resistor R ₁ or the voltage regulating transformer T, the resistor R ₁ ' can also be varied It also becomes possible to adjust the ignition voltage V _Bp of the ignition circuit Q ₁ .

In addition, as shown in Figure 2, a resistor is connected to diode D.
By connecting R ₂ in parallel, when the thyristor SCR is turned on, a negative voltage is applied to the gate G via the resistor R ₂ to the anode A and cathode K, shortening the turn-off time of the thyristor SCR. This enables high frequency operation. That is, as shown in FIG. 5, a reverse gate current i flows when the thyristor SCR is turned on.

According to the invention, the ignition circuit Q ₁ includes a thyristor SCR, an anode of the thyristor SCR,
A charging/discharging circuit CF is connected between the gates and is charged so that the anode side becomes positive, and a charging/discharging circuit CF is connected between the gate of the thyristor SCR and the charging/discharging circuit CF so that the charging direction is forward with respect to the charging direction of the charging/discharging circuit CF. The charging/discharging circuit CF is composed of a parallel circuit of a resistor _R1 and a capacitor _C1 , and the charging/discharging circuit CF is connected to the discharge lamp power source E in the pulse generating circuit B'. A power supply circuit F is provided which charges with a voltage proportional to the power supply voltage Eo, and the power supply voltage Eo of the discharge lamp power supply E and the discharge lamp voltage Vla of the discharge lamp L are set to be substantially the same, and the pulse generation circuit
The charging voltage Vc of the capacitor _C1 of the charging/discharging circuit CF is adjusted such that B' operates after the ballast current I _CH of the ballast CH finishes flowing and lights the discharge lamp L every half cycle. The resistance of the discharging circuit CF is set higher than the lamp voltage Vla and lower than the peak value of the power supply voltage Eo, so that the charging voltage Vc of the capacitor _C1 includes a ripple synchronized with the power supply voltage Eo.
Since the resistance value of R ₁ is set small, the ignition voltage V _BO of the ignition circuit Q ₁ fluctuates in proportion to the power supply voltage Eo, and when the power supply voltage Eo becomes high, the ignition voltage V BO of the ignition circuit Q 1 changes in proportion to the power supply voltage Eo. As the current decreases, the discharge lamp current Ila
In order to suppress the increase in power supply voltage Eo, fluctuations in the discharge lamp current due to fluctuations in the power supply voltage Eo can be minimized, and therefore the discharge lamp L can be operated satisfactorily even if the power supply voltage Eo fluctuates. .

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a conventional example, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a current waveform diagram for explaining operation, and Fig. 4 is a circuit diagram showing another embodiment. ,
FIG. 5 is a circuit diagram for explaining the operation, FIG. 6 is a waveform diagram for explaining the operation of the conventional circuit, and FIG. 7 is a waveform diagram for explaining the operation of the present invention. Q ₁ ...Ignition circuit, SCR...Thyristor, CF...
...charging/discharging circuit, L...discharge lamp, B'...pulse generation circuit, E...discharge lamp power supply, F...power supply circuit.

Claims (1)

[Claims] 1. The discharge lamp L is connected to the discharge lamp power supply E via the ballast CH.
In a discharge lamp lighting device in which a pulse generating circuit B' having an ignition circuit _Q1 is connected in parallel to a discharge lamp L, the ignition circuit _Q1 includes a thyristor SCR and a pulse generating circuit B' having an ignition circuit Q1. A charging/discharging circuit CF is connected between the anode and the gate and is charged so that the anode side becomes positive, and a charging/discharging circuit CF is connected between the gate of the thyristor SCR and the charging/discharging circuit CF in the forward direction with respect to the charging direction of the charging/discharging circuit CF. The charging/discharging circuit CF is composed of a parallel circuit of a resistor _R1 and a capacitor _C1 , and the charging/discharging circuit CF is connected to the discharge lamp power supply to the pulse generating circuit B'. A power supply circuit F is provided which charges with a voltage proportional to the power supply voltage E ₀ of the discharge lamp power supply E, and the power supply voltage E ₀ of the discharge lamp power supply E and the discharge lamp voltage Vla of the discharge lamp L are set to be approximately the same, and the pulse generation circuit B ' is activated after the ballast current IcH of the ballast CH finishes flowing, and the discharge lamp _L is lit every half cycle. set higher than Vla and lower than the peak value of the power supply voltage Eo, such that the charging voltage Vc of the capacitor _C1 includes a ripple synchronized with the power supply voltage Eo;
A discharge lamp lighting device characterized in that the resistance value of the resistor _R1 of the discharge circuit CF is set to be small.