JPH048920B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a discharge lamp constant input dimming lighting device.

In general, discharge lamps have a negative characteristic in which the lamp terminal voltage increases when the current is reduced. Therefore, when switching from rated lighting to dimming lighting, the sudden decrease in lamp current causes the restriking voltage to exceed the power supply voltage. This may cause a phenomenon called "fading out" in which the discharge lamp goes out. Therefore, in controlling the dimming of a discharge lamp, the first requirement is to prevent the lamp from going out.

What is shown in FIG. 1 is a conventional dimming lighting device designed to prevent the above-mentioned dimming.
To explain the configuration below, a series circuit of an AC control element S ₁ , a current limiting inductance CH ₁ , and a discharge lamp L is connected to both ends of an AC power source E such as a commercial power source. rate improvement capacitor
An auxiliary choke coil CH ₂ and a series circuit of a capacitor C 1 and a resistor R ₁ are connected in parallel to both ends of the AC control element _{S 1 ,} and the gate of the AC control element _{S 1 is} connected to the control circuit 1 . The control circuit 1 is the second
As shown in the figure, before explaining its configuration, the operating principle of this conventional device will be explained.

Now, in the phase control of a discharge lamp, the lamp current (commutation) phase T, the off period ΔT, and the conduction phase T+ΔT can be considered as the quantities that indicate the state.
The lamp current phase T is the phase when an AC control element such as a triator commutates (extinguishing in this case), and the off period ΔT is the phase in which the AC control element is kept off from commutation until it is re-ignited. It is a period. If the point at which the power supply voltage crosses zero is used as a reference for measuring the phase, the lamp current phase T is a phase angle corresponding to the time from when the AC power supply voltage crosses zero until the AC control element commutates. According to actual measurements, the relationship between the lamp current phase T and the off period ΔT in the stable state of each dimming has a negative slope as shown by the solid line in Figure 5, and it varies depending on the type of discharge lamp. Although there are variations, each dimming ratio (for example, (a) is 60%, (b) is 70%)
Indicates the status at each dimming ratio, such as %.
It has been confirmed that the straight line connecting the points corresponding to (d) is the brightest state, which is the rated lighting with a dimming ratio of 100%, has an almost constant slope regardless of the type of discharge lamp. , this conventional device calculates T and ΔT by ΔT _i =k・T _i-1 + α (i indicates the order,
T _{i -1} indicates the immediately preceding T), that is, by controlling the light while maintaining a constant input condition, it is possible to lead to a stable dimming state without fading. In addition, the lamp current phase of the first half cycle
The reason why ΔT _i of the current half cycle is determined using T _i-1 is to converge the operating point on the control straight line.

FIG. 2 is a block diagram showing the configuration of a control circuit for creating the above relationship, and its configuration and functions will be explained below. The power supply voltage zero-crossing detection circuit 10 outputs a signal every time the voltage of the AC power supply E crosses zero, and the output is selected by a dimmer switch SW to be used directly or via a monostable multi 12. After that, it is given as an operation circuit signal for the addition counter 13. The addition counter 13 is given an initial value n ₀ and is incremented by the first clock CLK ₁ after the period T ₀ has elapsed. The commutation detection circuit 11 detects the commutation of the AC control element _S1 and outputs a signal, and uses the output to preset the calculated value of the addition counter 13 into the subtraction counter 15 via the latch 14, and at the same time presets the calculation value of the addition counter 13 into the subtraction counter 15. Start 15. Subtraction counter 15
The count value given by the latch 14 is subtracted by the second clock CLK ₂ , and when the count value becomes zero, it is detected by the zero comparison circuit 16, and the trigger circuit 17 is activated to restart the AC control element _S1 . ignite. That is, the lamp current phase T _i-1 of the first half cycle is detected in the form of the count value of the addition counter 13, and from this, the relationship ΔT _i of ΔT _i = kT _i-1 + α is obtained, and the AC control element S ₁ is controlled. The relationship between T _i-1 and ΔT _i when not dimming (dimmer switch SW is on side a) is shown in Figure 3, where point A is the operating point immediately after starting, and point B is the Indicates the stable point when lighting. On the other hand, during dimming, by turning the dimmer switch SW to the b side, the output of the power supply voltage zero cross detection circuit 10 is phase-shifted by the monostable multi 12 and given to the addition counter 13, so that T _i-1 in FIG. The same effect as when the coordinate axis is moved in parallel to the right is obtained, and the control conditions corresponding to the desired dimming state are created while the slope remains unchanged. In order to prevent the switch from chattering, an actual dimming switching circuit may have the configuration shown in FIG. 4. Gate
G ₁ and G ₂ constitute flip-flops, gates G ₃ and G ₄ constitute digital switches, and gate G ₅ is used for signal synthesis.

Figure 5 shows the operation of the above conventional example, and the intersection of the straight line of the discharge lamp itself (the straight line shown by the solid line in the figure) and the control condition ΔT _i =k・T _i-1 + α is stable. It becomes a point. That is, at the time of starting, the point A is approached and the lighting is stabilized at the rated lighting condition (d). Furthermore, during dimming, the off period ΔT increases by switching the dimmer switch SW, and the process follows the process shown by the broken line and is guided to a stable point corresponding to the dimming ratio. By the way, the shaded area in the figure shows the area where the off period ΔT is too large and the light goes out, but this conventional dimming lighting device may fall into this area (as shown in the figure). b') There is still a possibility that the lamp will go out by entering this area.

The present invention has been proposed in view of the above points, and does not directly shift from rated lighting to dimmed lighting, but gradually shifts to the desired dimming state, thereby avoiding passing through the fade-out region. An object of the present invention is to provide a highly reliable discharge lamp constant input dimming lighting device that can completely prevent a discharge lamp from going out.

The present invention will be described in detail below with reference to the drawings showing its operating principle and embodiments.

FIG. 6 shows the operation of the present invention, and shows how by gradually increasing the off-period ΔT, a transition to stable dimming is achieved without entering the lamp extinguishing region and without causing the lamp to extinguish. In extreme terms, by increasing the OFF period in very small increments, the dimming stability point can be reached at various dimming ratios, and this is ideal dimming switching control.
However, as a practical matter, such a control method has a complicated circuit configuration and the time required to transition from rated lighting to stable dimming is too long to be practical. A method is adopted in which the initial value of such a control circuit is gradually increased by using a clock with a long cycle, thereby increasing the off period ΔT.

FIG. 7 shows an embodiment of the present invention,
The configuration of the control circuit is shown in a block diagram. Note that parts having the same functions as those of the conventional example are given the same reference numerals. Further, the wiring state of the entire device is the same as that shown in FIG. Referring to FIG. 7, the configuration of the control circuit is the same as the conventional control circuit except that the output from the power supply voltage zero cross detection circuit 10 is directly applied to the addition counter 13 and thereafter. The difference is that since the initial value given to the addition counter 13 is not constant, a second counter 18, a comparator 19, and a comparator 19 are used to gradually increase the initial value during dimming.
A third clock CLK ₃ , a gate G, and an initial value n ₁ as a dimming reference signal are newly added.
Here, clock CLK ₃ is set to have a longer period than clocks CLK ₁ and CLK ₂ , and this clock CLK ₃ is applied to one input terminal of OR gate G, and is applied to the other input terminal of OR gate G. The output of the comparator 19 is added to the output of the comparator 19, and after the OR gate G performs a logical sum of the two, the output clock is applied to the second addition counter 18. The addition counter 18 is given an initial value n ₀ and is incremented by the clock given from the gate G. Further, the count output of the addition counter 18 is compared with the initial value _n1 set corresponding to the desired dimming state by the comparator 19, and the comparator 19 outputs "H" if the two match. If not, it outputs "L". That is, until the count output of the addition counter 18 and the initial value _n1 match, the output of the comparator 19 is "L", so the clock is
The addition counter 18 continues to add up each time CLK ₃ is input, and after a match occurs, the output of the comparator 19 becomes "L", so the output of the gate G remains constant at "H" and no addition is performed. Then the second
The count output of the counter 18 is the first counter 13
However, since the clock CLK ₃ is set to a sufficiently long period compared to the clocks CLK ₁ and CLK ₂ , the control conditions for each initial value are changed in the process of transitioning from the initial value n ₀ to n ₁ . and maintain control. The relationship between the lamp current phase T and the off period ΔT is shown in Figure 8. At startup and rated lighting, a control condition is created that passes through points A and B corresponding to the initial value n ₀ , and at dimming lighting. The control condition gradually shifts to the desired dimming state (point C). By controlling the AC control element _S1 under such control conditions, the operation shown in FIG. 6 can be obtained. In addition, the transition time from rated lighting to stable dimming is determined by the clock.
It can be changed by the cycle of CLK ₃ .

As described above, in the present invention, an AC power supply, an AC control element, a current limiting impedance, and a discharge lamp are connected in series, and the conduction phase of the AC control element is changed every half cycle of the AC power supply in accordance with the lamp current phase. In a lighting device that controls the dimming of a discharge lamp by controlling the dimmer, the control gradually shifts to a dimming state by delaying the conduction phase of the AC control element over time by a dimmer switch and a switching operation of the dimmer switch. Since the circuit is provided, it is possible to shift to a predetermined dimming state while maintaining the stable state of the discharge lamp, and since the lamp does not enter the extinguishing region, it is possible to completely prevent the occurrence of extinguishing.

In short, according to the present invention, (a) it is possible to shift to a predetermined dimming state while maintaining a stable state of the discharge lamp.

(b) The configuration of the present invention is a digital circuit configuration,
In addition to being a compact control circuit, the dimming signal can be set freely, and it can accommodate variations in lamp type and lamps, and the dimming ratio can be set up to the limit level of the lamp.

This has the effect of

[Brief explanation of drawings]

Fig. 1 is an overall circuit diagram of a discharge lamp lighting device according to a phase shift control method, Fig. 2 is a block diagram of a conventional control circuit, Fig. 3 is an explanatory diagram of its operation, and Fig. 4 is a control circuit shown in Fig. 2. 5 is an explanatory diagram of the operation of the conventional device, FIG. 6 is an explanatory diagram of the principle operation of the present invention, and FIG. 7 is a configuration block diagram of a control circuit according to an embodiment of the present invention. FIG. 8 is an explanatory diagram of its operation. DESCRIPTION OF SYMBOLS 1... Control circuit, 10... Power supply voltage zero cross detection circuit, 11... Commutation detection circuit, 13, 18... Addition counter, 14... Latch, 15... Subtraction counter, 1
6...Zero comparison circuit, 17...Trigger circuit, 19...Comparator, _S1 ...AC control element, _CH1 , _CH2 ...Inductor, L...Discharge lamp, E...AC power supply.

Claims (1)

[Claims] 1 An AC power supply, an AC control element, a current limiting impedance, and a discharge lamp are connected in series, and the conduction phase of the AC control element is controlled every half cycle of the AC power supply in accordance with the lamp current phase to control the dimming of the discharge lamp. In the lighting device, the conduction phase is changed by a dimmer switch and a switching operation of the dimmer switch, while comparing a dimming reference signal corresponding to the conduction phase of the AC control element with a signal in an excessive dimming state. A constant input dimmer lighting device for a discharge lamp, characterized in that the control circuit is configured to control the discharge lamp constant input.