JPS63245899A - Dimmer in discharge lamp lighter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a dimming device in a discharge lamp lighting device having a series inverter configuration, regardless of whether it is a self-excited or separately excited inverter.

Conventional technology Traditionally, this kind of series inverter (half bridge)
Some discharge lamp lighting devices using a light source have a dimming function as shown in FIG. First, a full-wave rectifier circuit 2 is connected to an AC power source 1, a capacitor C0 is connected between its DC output terminals, and an inverter circuit 3 is connected to the AC power source 1.
is connected. This inverter circuit 3 is a drive circuit 4
Is it connected in series that is alternately driven on and off by oscillation? switching transistors Q1. It is composed of Q as the main part. In addition, two rectifier diodes D, D, connected in parallel to these transistors Q, Q2, and transistors Q, D, are connected in parallel.
Two DC cut capacitors C, C2 in parallel with Q are provided between the DC power lines. A discharge lamp 5 is provided as a load, and a current-limiting inductor choke L and a capacitor C are connected to each other via filaments 5a and 5b of the discharge lamp 5. , C, and are connected in series to form an LC series resonant circuit.

With such a configuration, a sine wave flows through the LC series resonant circuit according to the switching transistor Q□IQR which is turned on and off alternately, and after the discharge lamp 5 is turned on, the Q of the LC series resonant circuit decreases and it is not in a resonant state. Therefore, a triangular wave is supplied.

Here, in order to light the discharge lamp 5 in a dimmed state, conventionally, by controlling the level of the external DC signal S to the drive circuit 4, the signal is applied to the switching transistors Q, , Q, via the drive circuit 4. The lighting frequency is changed from the full-light lighting frequency to the dimming frequency.

That is, when considering the discharge lamp 5, which is this type of load, its equivalent circuit can be considered as one in which an inductor component is connected in series to a parallel circuit of a resistance component and a capacitance component. As a result, there is a resonance curve characteristic between the operating frequency f in the inverter circuit 3 and the secondary voltage in the discharge lamp 5 as shown in FIG. f,
is the resonant frequency. As a result, for example, in the full-light lighting state, the lighting frequency is fl and the lighting frequency is set to fl, but in dim lighting mode, the lighting frequency is increased to f2. As a result, as shown in FIG.
The secondary voltage decreases as shown in (2) compared to (1) when full light is on, and the brightness also decreases, resulting in a dimmed lighting state.

Incidentally, in many cases, when the discharge lamp 5 is dimmed and lit, the discharge lamp 5 is dimmed to be gradually brought into a full-light state when the discharge lamp 5 is started. That is, it is a dimming start. However,
According to the conventional dimming method, as shown in Figs. 4 and 5, when the DC level of the external DC signal S is controlled to increase the lighting frequency for dimming, the secondary voltage also decreases. .

As a result, when dimming at the time of starting, if the dimming level is too low (if the frequency is too high)
The next voltage could not be obtained, and in the end, the dimming level (specifically, 5
It is not possible to start dimming depending on the dimming level (below 0%).

Therefore, the applicant has considered a method as shown in FIG. 6 as a method for controlling dimming so that the engine can be started in a dimmed state. That is, in the circuit configuration of FIG. 3, instead of the external DC signal S as the signal input to the drive circuit 4, for example, a PWM signal (pulse width modulation signal) is input as the external signal for dimming, and the drive circuit 4 The lighting state of the discharge lamp 5 is determined by alternately and periodically switching between a full-light lighting frequency state and a dimming frequency state as the lighting frequency applied to the inverter circuit 3 including the switching transistors Q, , Q, using a PWM signal. It dims the light.

In other words, at the time of dimming lighting, the dimming frequency (for example,
f, ), but during the entire period, instead of using the dimming frequency f2 as the lighting frequency, the full light lighting frequency (for example, f,) is also used,
The lighting frequency is alternately and periodically switched between the full-light lighting frequency state and the dimming frequency state to dim the discharge lamp 5.

Here, for example, a relatively low frequency f for all-light lighting
1 as the lighting frequency, and t2 as the period in which the relatively high dimming frequency f2 is used as the lighting frequency. Under the condition that 10tt=constant period t, period 1. , 1° ratio (duty ratio)
The dimming state is controlled by changing the PWM signal.

Figure 6(a) shows the external dimming signal (PWM signal) when the full light is on (brightness 100%), and the lamp current I flowing through the discharge lamp 5.
This shows the state of L and secondary voltage (■). in this case,
The PWM signal remains at O level, and the lighting frequency is a relatively low lighting frequency f for full light lighting.

However, in Figure 6(b), the brightness is 50% when all lights are on.
The PWM signal is a signal state in which H and L levels repeat at equal intervals within a certain period.

As a result, the period t and the period t2 have the same length, as shown in the lamp current IL and the secondary voltage (2). Here, the period t1 is a lighting period at the full-light lighting frequency f, and since the frequency is relatively low, a large lamp current IL is obtained as can be understood from FIGS. 4 and 5. In addition, the secondary voltage (2) is also high as shown in (1). On the other hand, the period t2 is a lighting period using the dimming frequency f2, and the frequency is relatively high, so
This is a period in which the lamp current IL becomes low and the secondary voltage (2) also becomes low as shown in (2). Such a period 1. ．． 1. Since these are alternately repeated at the same rate, the entire lighting state is a dimmed lighting state (50%). Even if the discharge lamp 5 is started in such a dimming state, the period t1 is periodically included and a state in which a high secondary voltage 1 is generated is ensured, so the discharge lamp 5 can be started reliably. becomes.

Then, FIG. 6(C) shows a case where the dimming level is further increased, for example, the brightness is set to 25% of the brightness when all lights are on.
Period 1. , 1. This shows a state controlled by a PWM signal such that the ratio of t: t2=1=3.

In this way, even during dimming, by periodically mixing the full-light lighting frequencies, a large secondary voltage necessary for starting with dimming is ensured. Therefore, dimming start is possible.

Problems to be Solved by the Invention However, in the case of the dimming method shown in FIG. 6, the dimming level is set to 50%, and the PWM signal is Even if control is performed, the actual dimming state of the discharge lamp 5 may be higher than or equal to the desired dimming level due to distortion of the power supply, such as harmonic distortion of the power supply waveform. It is something.

In other words, a lighting state at a desired dimming level cannot be obtained, and flickering may occur due to power supply distortion or the like.

Means for Solving the Problems A setting means for setting the dimming level of the discharge lamp is provided, a detecting means for detecting the lighting state of the discharge lamp is provided, and a detection signal from the detecting means and a dimming level by the setting means are provided. and generates a dimming control signal that alternately and periodically switches between a full-light lighting frequency state and a dimming frequency state as a lighting frequency to be applied to the switching element so as to match this dimming level. A dimming control means for outputting to the drive circuit is provided.

At the time of operation dimming, the application state of the dimming frequency and the application state of the full-light lighting frequency are alternately and periodically switched and applied as the lighting frequency. Thereby, even if the light is dimmed at the time of starting, a secondary voltage that can be used for starting is ensured. On the other hand, in the dimming lighting state, the lighting state of the discharge lamp, that is, the brightness, is detected by the detection means, and by inputting the detection signal to the dimming control means, the difference from the set dimming level is checked. be done. Here, if the lighting state is such that there is a difference between the dimming level and the dimming level due to power supply distortion, etc., the dimming control means corrects the duty ratio of the image frequency application period in the dimming control signal and applies it. , the light is turned on at the desired dimming level.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 and 2. Components that are the same as those shown in FIGS. 3 to 6 are indicated using the same reference numerals. In this embodiment, the basic dimming method is as explained in FIG. 6. This difference is within a certain period of time 1, . The duty ratio of 12 is automatically corrected and controlled by a feedback control system.

First, for the discharge lamp 5, a photoelectric element 6 is used as a detection means for detecting the lighting state of the discharge lamp 5, specifically, the brightness.
are placed facing each other. The light output from the photoelectric element 6 is amplified by an amplifier 7 and input to an integrator 8. This integrator 8 calculates the lighting state of the discharge lamp 5 within a predetermined period of time by integrating the light output output from the photoelectric element 6, and it calculates the lighting state of the discharge lamp 5 within a predetermined period of time by a reset signal sent to the reset terminal every fixed period t,/2. will be reset.

The output VB from this integrator 8 is input to one input terminal of a comparator 9. Further, a reference voltage vA from a variable reference power source 10 serving as a dimming level setting means is input to the other input terminal of the comparator 9. The light control means 11 is controlled by the integrator 8 and comparator 9.
is formed, and P is transmitted from the comparator 9 to the drive circuit 4.
A dimming control signal in the form of a WM signal is output.

In such a configuration, during dimming lighting, the dimming frequency f2 and the full-light lighting frequency f2 are set as shown in FIG.
, and are periodically switched alternately.

For example, assume that the state shown in FIG. 2(a) is a reference state that is a dimmed lighting state corresponding to the reference voltage vA set by the variable reference power source 10.

That is, for example, period 1. , 1. The duty ratio of is tl:
The condition is t=1:3. In such a state, the level of the dimming control signal is switched at the point when the values of the outputs V and H from the integrator 8, which is obtained by integrating the light reception output by the photoelectric element 6, reach the reference voltage vA, and the level of the dimming control signal is changed to a higher frequency. This is ensured by switching the dimming frequency f2, which is , to the period t2, in which the lighting frequency is used as the lighting frequency.

Consider a case where the dimming lighting state of the discharge lamp 5 deviates from the desired dimming level due to power supply distortion or the like. For example, when the actual lighting level of the discharge lamp 5 is higher and brighter than the set dimming level, the output VB detected by the photoelectric element 6 and integrated by the integrator 8 is shown in FIG. 2(b). Since it is larger than the standard time shown in the same figure (,a),
It quickly reaches the level of the reference voltage vA. As a result, from the comparator 9, the lighting period t is determined by the full-light lighting frequency f.
The periods t, , 1 . A dimming control signal is generated by correcting the duty ratio of , and is output to the drive circuit 4. As a result, the proportion occupied by the full-light lighting state in the constant period t is reduced compared to the case of FIG. 2(a), and the lighting is substantially at the desired dimming level.

Conversely, when the actual lighting level of the discharge lamp 5 is lower than the set dimming level and is darker, the output VB detected by the photoelectric element 6 and integrated by the integrator 8 is shown in FIG. 2(c). Since it is smaller than the standard time shown in the same figure (,a),
The level of the reference voltage vA is reached at a delayed timing.・As a result, the duty ratio of the period t□+'ta is corrected so that the lighting period t according to the full-light lighting frequency f is longer than the case of FIG. 2 1(a) from the comparator 9. A dimming control □ signal is generated and the drive circuit 4
Output to. As a result, the proportion of the full-light lighting state in the constant period t increases compared to the case of FIG. 2(a), and the lighting is substantially at the desired dimming level.

In this way, even if the dimming lighting state fluctuates due to power distortion or the like, the feedback control system by the dimming control means 11 ensures that the lighting state is always at the preset dimming level. and does not cause flickering. Further, the dimming level itself can be arbitrarily set by variably adjusting the value of the reference voltage vA by the variable reference power supply 10.

Effects of the Invention As described above, the present invention applies the lighting frequency by alternating and periodically switching the application state in the state of the dimming frequency and the application state in the state of the full-light lighting frequency as the lighting frequency during dimming. By doing so, it is possible to start dimming, but in such a dimming lighting state, the lighting state of the discharge lamp, that is, the brightness is detected by the detection means, and the detection signal is input to the dimming control means. The difference from the set dimming level is checked, and if there is a difference between the lighting level and the dimming level due to power supply distortion, etc., the dimming control means changes the image frequency in the dimming control signal. The duty ratio of the application period is corrected and applied, so that the lighting state can be maintained at a desired dimming level.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a waveform diagram showing its operation, Fig. 3 is a circuit diagram showing a conventional example, and Fig. 4 is a circuit diagram showing an embodiment of the present invention.
The figure is a frequency-secondary voltage characteristic diagram, and Figure 5 is a lighting frequency-2
The next voltage/brightness characteristic diagram, FIG. 6, is a waveform diagram showing a method already proposed by the present applicant. 4... Drive circuit, 5... Discharge lamp, 6... Photoelectric element (detection means), 10... Variable reference power source (light control level setting means), 11... Light control control means, Q ,, Q...
・Switching transistor (switching element), f
l... Frequency for full light lighting, f2... Frequency for dimming,
t... constant period

Claims (1)

[Claims] In a discharge lamp lighting device for lighting a discharge lamp by driving two switching elements connected in series alternately by a drive circuit to cause oscillation operation, a setting means for setting a dimming level of the discharge lamp is provided, A detection means for detecting the lighting state is provided, and a detection signal by the detection means is compared with a dimming level by the setting means, and a full-light lighting frequency is determined as a lighting frequency to be applied to the switching element so as to match the dimming level. 1. A dimming device for a discharge lamp lighting device, comprising a dimming control means for generating a dimming control signal that alternately and periodically switches between a state and a dimming frequency state and outputting it to the drive circuit.