JPH03156896A - Lighting device for high-pressure discharge lamp - Google Patents

Abstract

PURPOSE:To perform dimming without changing the color temperature so much by feeding the electric power containing the high-frequency ripple component to a high-pressure discharge lamp, and adjusting the ripple content. CONSTITUTION:A rest period that all switching elements Q1-Q4 are turned off is provided before the on-periode of switching elements Q1-Q3 and Q4. The short circuit state generated when Q3 and Q4 are concurrently turned on is prevented. Q1 and Q2 are turned on or off in the on-periods of Q3 and Q4. The on-duty of Q1 and Q2 is feedback-controlled to make the lamp current constant. When the value of the capacitor C of a filter circuit 2 is made small or the value of an inductance L2 is made large, the high-frequency ripple component contained in the lamp current to a high-pressure discharge lamp L is increased. The cutoff frequency of the circuit 2 is adjusted.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a high-pressure discharge lamp lighting device for lighting a high-pressure discharge lamp such as a metal halide lamp.

[Conventional technology]

Conventionally, as a lighting device for a high pressure discharge lamp of this type, a configuration using a lighting power supply circuit 1 comprising a full bridge type inverter as shown in FIG. 8, for example, is known. This lighting power supply circuit 1 is configured to turn on and off a DC power supply DC using four switching elements Q1 to Q4, and supply power to a high-pressure discharge lamp L via a current-limiting inductance L and a filter circuit 2. That is, the four switching elements Q, ~Q, are divided into two elements each (Q, Q, Q
2 and Q,) are connected in series, and each series circuit is connected between both ends of the DC power supply DC,
Switching elements Q, , Q, Q 2 , of each series circuit
A series circuit including a current limiting inductance L1, an inductance L2 of the filter circuit 2, and a high-pressure discharge lamp L is connected between the connection point Q4. Further, the capacitor C of the filter circuit 2 is connected in parallel to the series circuit of the inductance L2 and the high pressure discharge lamp L. Furthermore, diodes D, -D4 are connected in antiparallel to each of the switching elements Q1 to Q4, respectively, and the switching elements Q, Q2 are turned on and off at several tens of kHz, and the switching elements Q, , Q, is turned on and off at several hundred Hz. As shown in FIGS. 9(c) and (cl), the switching element Qs. Q4 is turned on and off alternately, as shown in Figure 9(b). As shown in (c), during the period when the switching element Q) is on, the switching element Q2 is turned on and off, and the 9th
As shown in Figures (a) and (d), switching element Q4
The operation timing is set so that the switching element Q1 is turned on and off during the period when Q1 is on. Therefore, when switching element Q is on, when switching element Q1 is on, DC power supply D
C → switching element Q, → current limiting inductance L1
→ Inductance 2 → High-pressure discharge lamp L) and capacitor C → Switching element Q4 → Resistor R → DC power supply DC. When switching element Q1 turns off, the energy accumulated in current-limiting inductance L1 causes a current to flow. , current-limiting inductance L1 → (inductance upper 2 - high pressure discharge lamp) and capacitor C → switching element Q, → resistor R → diode D, →
Current flows through the current-limiting inductance Ll. On the other hand, when switching element Q is on, switching element Q2 is on, DC power supply DC → switching element Q2 → (inductance upper 2 →
Current flows through the path of high-pressure discharge lamp) and capacitor C- + current-limiting inductance L1 → switching element Q, → resistor R - DC power supply DC, and the current flows through the switching element Q.
When 2 is turned off, the energy stored in the current limiting inductance L1 causes the current limiting inductance to become → switching element Q3 → resistor R - diode D, → (inductance upper 2 - high pressure discharge lamp L) and capacitor C - current limiting inductance. Current flows through a path called inductance. As a result of the above-described operation, a high-frequency current ILI flows through the current-limiting inductance L1, as shown in FIG. 9(e). The filter circuit 2 constituted by an inductance L2 and a capacitor C serves as a current-limiting inductance and is set to cut high frequency components flowing through the filter circuit 2. Therefore, the lamp current I flowing through the high-pressure discharge lamp. As shown in FIG. 9(f), the switching element Q
3. This is a rectangular wave corresponding to the on/off period of Q4 superimposed with a high frequency ripple component of the on/off period of switching elements Ql and Q2. By the way, in the above circuit, a current corresponding to the lamp current is detected as the voltage across the resistor R, and after being amplified by the amplifier circuit 3, the lamp current is controlled so as to be constant depending on the magnitude of the voltage across the resistor R. The on-duty of the switching elements Q t and Q 2 is feedback-controlled via the circuit 4 and the drive circuit 5. Here, if the amplification factor of the amplifier circuit 3 is changed by adjusting the resistance value of the variable resistor VR, the switching elements Q I, Q 2
Since the on-duty of the lamp can be changed, the amplitude of the lamp current can be adjusted using the variable resistor VR. That is, the light can be adjusted by operating the variable resistor VR.

[Problem to be solved by the invention]

As mentioned above, it is known that when dimming is performed by adjusting the lamp current, the color temperature of the light emitted from the high-pressure discharge lamp changes depending on the dimming I (for example, Sahara Hikari;
"New Studio Using a Dimmable HMI Lighting System," Broadcasting Technology, January 1985). That is,
As shown by the solid line in FIG. 4, as the amount of dimming increases and the illuminance decreases, the color temperature increases. As described above, when the color temperature changes, there is a problem in that the way things look and feel changes, and depending on the intended use, it may cause a sense of discomfort. The present invention aims to solve the above-mentioned problems, and provides a lighting device for a high-pressure discharge lamp that allows dimming without significantly changing the color temperature.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a lighting power supply circuit that can obtain an output in which a high-frequency ripple component generated from a real generator is superimposed on a basic output, and a high-pressure discharge lamp that is lit by the output of the lighting power supply circuit. , and a ripple control circuit that adjusts the ripple content of the high-frequency real component to dim the high-pressure discharge lamp.

[Effect]

According to the above configuration, the high-pressure discharge lamp is lit by supplying power containing a high-frequency ripple component, and the light is dimmed by adjusting the ripple content, so compared to the case where the light is dimmed by adjusting the lamp current. , there is less change in color temperature when dimming,
It is possible to dim the light without changing the way things look or feel.

【Example】

As shown in FIG. 1, the basic configuration of the lighting power supply circuit 1 is almost the same as the conventional configuration shown in FIG. The DC power source is obtained by rectifying and smoothing the commercial power source AC in the power supply unit 6. Switching element Q. ~Q4, diode D, ~D1, and current-limiting inductance L have the same connection relationship as in Figure 8.
The operation timing of switching elements Q and S-Q is also the ninth
It is equivalent to the one shown in the figure. However, Fig. 2(a)
As shown in (b), before the on period of the switching elements Q, , Q, there is provided a rest period (dead off time T) in which all the switching elements Q1 to Q are turned off. This operation prevents a short-circuit condition due to simultaneous ON of switching elements Q and Q. Switching element Q4. As shown in FIGS. 2(c) and 2(d), Q2 is turned on and off during the on-periods of the switching elements Qs and Q-, respectively. Further, the on-duty of the switching elements Q, , Q is feedback-controlled so as to keep the lamp current constant. The filter circuit 2 includes an inductance L2 connected in series to the high-pressure discharge lamp L, and a capacitor C connected in parallel to the series circuit of the high-pressure discharge lamp L and the inductance L2.
It is composed of At least one of the inductance L2 and the capacitor C is variable, and the cutoff frequency of the filter circuit 2 is variable. That is, when the value of the capacitor C is decreased or the value of the inductance L2 is increased, the high-rise ripple component included in the lamp current to the high-pressure discharge lamp L increases. This is based on the knowledge that the luminance (indicated by the illuminance ratio) of the high-pressure discharge lamp L decreases, as shown by the solid line in FIG. Third
In the figure, the broken line is the lamp voltage, and the dashed line is the lamp current. As shown in FIG. 5, the ripple content is the amplitude I of the fundamental current. Amplitude ILp of high frequency ripple current with respect to C
It is expressed as a percentage of <(I LP/I I)e)X 100). Furthermore, as shown by the broken line in FIG. 4, the color temperature changed only slightly when the illuminance ratio changed. That is, when dimming was performed by controlling the lamp current as in the conventional configuration, there was a significant change in color temperature as shown by the dashed line in FIG. Compared to the configuration, the change in color temperature was negligible. In FIG. 4, a double-ended metal halide lamp was used, and horizontal lighting was performed with the tip portion (the convex portion near the center) facing upward in the high-pressure discharge lamp L. By the way, in order to adjust the cutoff frequency of the filter circuit 2, as shown in FIG. 6(a), a plurality of capacitors C0 to CI3 are provided, and capacitors CI2. C
Contacts r 121 r 13 such as a relay may be connected in series to I3, and the contacts r 12r r 13 may be opened and closed. Moreover, as shown in FIG. 6(b), the inductance L2
Inductance L 11 + L 2 divided into multiple parts
2, the cutoff frequency can also be adjusted by connecting a contact r22 such as a relay in parallel to the inductance L2m and opening and closing the contact r22.
Also. These configurations may be used in combination. Here, the capacitor C2, high-voltage pulse transformer T, igniter 7 that generates high-voltage pulses, etc. in FIG. 6 are difficult to start, such as a double-ended metal halide lamp. It only needs to be provided when a high-pressure discharge lamp L is used.Also, as shown in FIG. It may be started by applying an electric current.

Embodiment 2 In Embodiment 1, a full-bridge type lighting power supply circuit 1 was shown, but as shown in FIG. 7, this embodiment shows an example in which the lighting power supply circuit 1 is a half-bridge type. That is, the switching element QQ and the diodes D, D
3 is removed, and capacitors C2 and C4 are connected in its place. The power supply section 6 includes a filter circuit 8, rectifying diodes Ds and Da, and a smoothing capacitor Cs,
Cb. Further, the lamp current is detected by the current detection unit 9, and the switching element Q,
, Q. Furthermore, an igniter 7 and an igniter control circuit 12 are provided to facilitate starting. Power is supplied to the PWM 11 control circuit 10 and the igniter control circuit 12 from a control power supply section 13. Here, when using a high-pressure discharge lamp L that can be started without the igniter 7, the igniter 7, the igniter control circuit 12, the high-voltage pulse transformer T, and the capacitor C2 need not be provided. Even with this configuration, by adjusting the cutoff frequency of the filter circuit 2, the ripple content of the lamp current can be adjusted and dimming can be performed, as in the first embodiment.

[Example 3] In the above example, dimming was performed by adjusting only the ripple content of the lamp current, but in high-pressure discharge lamps, if the ripple content becomes too large, an acoustic resonance phenomenon occurs. This may cause problems such as flickering or fading. Therefore, if the light is modulated by adjusting only the ripple content rate, the dimming range will be limited. This embodiment uses a configuration for adjusting the ripple content of the lamp current, and a configuration for adjusting the amplitude of the basic component of the lamp current, as shown in FIG. 8, to create an acoustic resonance phenomenon. This expands the dimming range without causing any problems. With this configuration, although the dimming range can be set to be the same as in the conventional configuration, changes in color temperature can be made smaller than in the conventional configuration.

【Effect of the invention】

As described above, the present invention provides a lighting power supply circuit that can obtain an output in which a high-frequency ripple component generated from a ripple generating section is superimposed on a basic output, a high-pressure discharge lamp that is lit by the output of the lighting power supply circuit, and a high-frequency ripple component that is generated by a ripple generator. It is equipped with a ripple control circuit that dims the high-pressure discharge lamp by adjusting the ripple content of the components, and supplies power containing high-frequency ripple components to the high-pressure discharge lamp to light it and adjust the ripple content. Compared to dimming by adjusting the lamp current, there is less change in color temperature when dimming, and dimming can be done without changing the way things look or feel. It has the advantage of being able to

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a first embodiment of the present invention, Figs. 2 to 5 are explanatory diagrams of the same operation as above, Fig. 6 is a main part circuit diagram of the same as above, and Fig. 7 is a second embodiment of the present invention. 8 is a circuit diagram showing a conventional example, and FIG. 9 is an explanatory diagram of the same operation. 1...Lighting power supply circuit, 2...Filter circuit, L.
...High pressure discharge lamp.

Claims (1)

[Claims] (1) A lighting power supply circuit that can obtain an output in which a high-frequency ripple component generated from a ripple generating section is superimposed on the basic output, and a high-pressure discharge lamp that is lit by the output of the lighting power supply circuit;
A lighting device for a high-pressure discharge lamp, comprising: a ripple control circuit that adjusts the ripple content of the high-frequency ripple component to dim the high-pressure discharge lamp.