JPH0328036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device, which controls the tube current according to fluctuations in the tube voltage of the discharge lamp, reduces fluctuations in the tube power, and maintains the input current even when the tube voltage decreases. This is to prevent it from growing indefinitely.

Fig. 1 shows a conventional discharge lamp lighting device that controls the tube current to be proportional to the difference between the tube voltage and approximately twice the reference tube voltage. discharge lamp, 3 is a ballast, 4 is a control circuit,
5 is a tube current detection resistor, and 6 is a triax.
7, 8, 9 are transformers, 10, 11, 12 are rectifier circuits configured with diode bridges, 13,
14 is a smoothing circuit, 15 is a resistor, 16 is a Zener diode, and a detected voltage value Vla' (= α・Vla)
is detected, and the reference tube voltage Vo of the discharge lamp 2 is applied to both ends of the resistor 15 via the transformer 9 and the rectifier circuit 12 to a value proportional to the proportional value α of the detected voltage value Vl'a. Double the set voltage value Vo′ (=2α・
Vo) is obtained, and the set voltage value V′o− is obtained in the control circuit 4′.
The first detection signal _S1 indicating the value of the detected voltage value Vl'a (2α·Vo−α·Vla) is output. In addition, the tube current of the discharge lamp 2 is supplied to the output terminal of the smoothing circuit 14 via the transformer 8 and the rectifier circuit 11.
A detected current value Il'a (β·Ila) proportional to Ila is detected, and a second detection signal _S2 indicating the detected value is output to the control circuit 4. Then, in the control circuit 4, the detected current value Il′a is proportional to the value of the set voltage value V′o−detected voltage value Vl′a (Il′a∝V′o−Vl′a.∵
β・Ila∝2α・Vo−α・Vla). That is, in this discharge lamp lighting device, the tube current Ila is proportional to the difference between approximately twice the reference tube voltage Vo and the tube voltage Vla (Ila∝
2Vo−Vla) to perform negative feedback operation to control the phase.

According to the above configuration, the tube current Ila is the reference tube voltage
Since it is controlled to be proportional to the difference between approximately twice Vo and the tube voltage Vla, the tube power of discharge lamp 2 is Wla
Then, since Ila∝2・Vo−Vla and Wla∝Ila・Vla, Wla∝(2・Vo−Vla)・Vla Wla∝−Vla ² +2・Vo・Vla dWla／dVla=−2・Vla+2・Vo However, since Vo is the reference value of the tube voltage Vla, -2・Vla+2・Vo≒0∵dWla/dVla≒0. Therefore, the tube power Wla due to the fluctuation of the tube voltage Vla
It is possible to reduce the fluctuation to approximately 0.

To explain more clearly how the tube current Ila is controlled in this conventional device, the tube current is controlled as shown by the straight line A in Figure 2.
This means that Ila is controlled against tube voltage Vla,
When the tube voltage Vla is approximately equal to the rated voltage (±20%), the tube power Wla is controlled to be approximately constant. The graph in Figure 2 shows the rated power supply voltage.
200V, reference tube voltage Vo 100V, reference tube voltage Io
1A, standard tube power Wo is 100W.

Therefore, in the case of FIG. 1, the tube power Wla can be held approximately constant even if the tube voltage Vla varies, so that, for example, variations in color temperature and luminous efficiency do not occur in the discharge lamp due to variations in the tube power. Further, the discharge lamp 2 will not be extinguished unexpectedly. Moreover, the tube power
Since there is no need to detect Wla, there is no need for an integration circuit, and the device does not become complicated or expensive.

However, when lighting an HID lamp with this conventional device, the tube current Ila is large immediately after starting, and the capacity of the power supply needs to be increased. That is, immediately after the HID lamp is started, the tube voltage Vla is as low as about 10V, and after 3 to 5 minutes, the tube voltage Vla shifts from about 10V to the rated value of 100V. This is because immediately after startup, the mercury vapor pressure is low and the tube voltage Vla is low, but due to heat generation in the arc tube, the mercury vapor pressure increases, and the tube voltage Vla increases from 3 to 3.
This is because it takes 5 minutes to reach the rating. Therefore, in the past, when the tube voltage Vla was low, the tube current Ila was increased, and the input current correspondingly increased, so the power supply was required to have the ability to flow a very large current.

The present invention solves the above problems and is characterized by a first detection signal proportional to the difference between the tube voltage and approximately twice the reference tube voltage, and a second detection signal proportional to the tube current. In a discharge lamp lighting device that extracts a detection signal and controls the second detection signal to be proportional to the first detection signal, a limiting circuit is provided to limit the first detection signal from exceeding a certain value. , the limiting circuit is provided with a plurality of limiters so as to limit the value of the first detection signal in a plurality of stages.

Hereinafter, the present invention will be explained according to the illustrated embodiment. As shown in FIG. 3, a Zener diode 1
7, 17', 17'' and resistors 26', 26'' is provided, and this control circuit 18 adjusts the detected voltage value from the set voltage value V'o (2α・Vo).
The signal obtained by subtracting Vl′a (α・Vla) is limited, and the tube current Ila is made to flow in proportion to this limited current. That is, the first detection signal _S1 is limited so as not to exceed a certain value.

Therefore, the relationship between tube voltage Vla and tube current Ila becomes as shown by line C in FIG. 2, and tube current Ila decreases from twice to 1.4 times the reference tube voltage Io. As a result, even if the tube voltage Vla is extremely low, the tube current Ila is used as the reference tube voltage Io.
It can be controlled so that it does not become much larger. Furthermore, if the limiting circuit 18 is provided with one limiter consisting only of the Zener diode 17, the voltage value of the first detection signal _S1 will be limited in one step as shown by line A in FIG. In contrast,
Since the limiting circuit 18 is provided with three limiters: the Zener diode 17, the Zener diode 17', the resistor 26', the Zener diode 17'', and the resistor 26'', each limiter is The voltage value of the first detection signal _S1 can be limited in multiple stages.

In the above embodiment, the tube current Ila is limited to 1.4 times the reference tube voltage Io, but it is not limited to this magnification, and may be limited to 1.3 times or any other magnification. However, if it is multiplied by 1.0,
When the tube voltage Vla is lower than the rated value, the tube current Ila cannot be made larger than the reference tube current Io, so the function of keeping the tube power Wla constant is lost.

Figure 4 shows the tube current Ila and tube voltage based on point b.
Another embodiment is shown in which Vla is detected. In the figure, 19 is an absolute value amplifier having operational amplifiers 20 and 21, which detects a detected voltage value Vl′a (α・Vla) proportional to tube voltage Vla. do. 22 is an absolute value amplifier having operational amplifiers 23 and 24, and the tube current
A detected current value Il'a (β·Ila) proportional to Ila is detected, and a second detection signal _S2 indicating the detected value is output. 2
5 is an addition/subtraction amplifier that subtracts the detected voltage value Vl′a (α・Vla) from the set voltage value V′o (2α・Vo) produced by the Zener diode 16, and outputs a first detection signal S ₁ indicating the subtracted value. Output. The limiting circuit 18 is composed of a plurality of limiters including Zener diodes 17, 17, 17'' and resistors 26, 26', 26'', and prevents the first detection signal _S1 of the adder/subtractor amplifier 25 from exceeding a certain voltage value. . 27 is a comparison circuit that compares the second detection signal S ₂ of the absolute value amplifier 22 and the first detection signal S ₁ from the limiting circuit 18;
The relaxation oscillation circuit 28 is controlled by the output. The control circuit 4 is composed of a comparison circuit 27 and a relaxation oscillation circuit 28, and the second detection signal _S2 is the first detection signal S1 _.
Triax 6 is controlled to be proportional to . Note that (V _EE ) (V _CC ) is the power supply of the operational amplifier.

Therefore, in this embodiment as well, the limiting circuit 18 can control the tube current Ila so that it does not become significantly larger than the reference tube voltage Io.

According to the present invention, since a limiting circuit is provided that limits the first detection signal so that it does not exceed a certain value, this limiting circuit can control the tube current so that it does not become significantly larger than the reference tube voltage. Even if the tube voltage becomes extremely low during startup, etc., the input current can be suppressed from increasing significantly, and the power supply does not need to be capable of passing a large current, resulting in remarkable effects. Furthermore, since the limiting circuit is provided with a plurality of limiters to limit the value of the first detection signal in multiple stages, it is possible to arbitrarily set the relationship between the tube current and tube voltage. , the tube power can be made ideal for the tube current. Moreover, if the tube voltage does not become extremely low, the tube power can be maintained approximately constant even if the tube voltage fluctuates as in the conventional method, and the effect is significant.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional example, Figure 2 is a graph showing the relationship between tube voltage, tube current and tube power,
FIG. 3 is a circuit diagram showing one embodiment of the present invention, and FIG. 4 is a circuit diagram showing another embodiment. 1...AC power supply, 2...discharge lamp, 3...ballast, 4...
control circuit, 5...resistance, 6...triax, 7,
8, 9... Transformer, 10, 11, 12... Rectifier circuit, 13, 14... Smoothing circuit, 15... Resistor, 16...
Zener diode, 18... Limiting circuit, 19... Absolute value amplifier, 22... Absolute value amplifier, 25... Adding/subtracting amplifier.

Claims (1)

[Claims] 1. A first detection signal proportional to the difference between the tube voltage and approximately twice the reference tube voltage, and a second detection signal proportional to the tube current are extracted, and this second detection signal is used as the second detection signal. In a discharge lamp lighting device that is controlled to be proportional to a first detection signal, a limiting circuit is provided to limit the first detection signal so that it does not exceed a certain value, and the limiting circuit has a control circuit that controls the first detection signal so as to be proportional to the first detection signal. A discharge lamp lighting device characterized in that a plurality of limiters are provided so as to limit the amount of water in multiple stages.