JPS6322040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a constant input current for a discharge lamp that can control the input current of the discharge lamp to be below the input current at the rated time from immediately after the discharge lamp starts to when the discharge lamp shifts to the rated lighting state. It relates to a lighting device.

In recent years, in order to meet the demand for compact, lightweight, and power-saving lighting devices, AC control elements are connected in series with the discharge lamps, even in the lighting circuits of high-pressure vapor pressure discharge lamps such as mercury lamps and high-pressure sodium lamps. A so-called phase control method that reduces current-limiting impedance by controlling the conduction phase angle of an AC control element has been researched, and has been put into practical use in some cases. Figure 1 is a diagram showing the principle circuit, in which 1 is a commercial power supply, 2 is a current-limiting impedance element, 3 is a discharge lamp,
4 is an AC control element, and 5 is a current limiting element that compensates for the current limiting impedance element 2 when the AC control element 4 is off. Figure 2 a and b show the lamp current of discharge lamp 3.
The phase relationship between Ila and the power supply voltage Vs is shown. Figure a shows the state immediately after starting, and Figure b shows the state at the rated time.

Generally, immediately after starting a high-pressure discharge lamp, the lamp conductance is much larger than at the rated time, so it is necessary to appropriately delay the conduction phase θ of the AC control element 4 compared to the rated time, as shown in FIG. It is known that if such phase control is performed, the input current can be kept below the rated input current during the period until the engine reaches the rated value (hereinafter referred to as the starting period), and constant input starting is possible. There is.

One of the phase control methods is a method using lamp voltage. This takes advantage of the fact that the lamp voltage of a high-pressure discharge lamp is low immediately after starting, and increases as it reaches its rated value until it reaches a stable point.The lamp voltage is converted to DC voltage, and the DC voltage and power supply voltage are set at a constant phase. This is a control method in which the intersection with the advanced reference voltage is the conduction phase of the AC control element, and if this control method is used, the high-pressure sodium lamp can be started reliably. The reason is that high pressure sodium lamps generally require sufficient preheating current to the heater to start. To achieve this, it is necessary to advance the conduction phase of the AC control element from immediately after starting until a kick pulse is generated after the starter switch in the lamp is opened to obtain a sufficient preheating current. This is because the heater resistance is sufficiently larger than the lamp equivalent resistance immediately after starting. Since the lamp voltage is the voltage across the lamp, in the case of a high-pressure sodium lamp, when the power is turned on, current flows to the heater, but the voltage drop across the heater is obtained as the lamp voltage. As is clear from the principle circuit diagram shown in Figure 3, this voltage appears as a voltage close to the power supply voltage Vs,
The above-mentioned lamp voltage conversion value becomes high, and the conduction phase of the AC control element 4 determined by the intersection of the conversion value and the reference voltage advances compared to immediately after starting, and a sufficient preheating current is obtained.

Although this control method has the advantage of being able to reliably start even high-pressure sodium lamps, it requires a block circuit 7 to prevent a starting voltage from entering the control section 6, as shown in FIG. This block circuit 7 is constituted by a circuit including an inductance, and has the drawback of hindering its size and weight. Further, a control line 8 is required to be input from both ends of the discharge lamp 3 to the control section 6, and therefore there is a drawback that the control section 6 must be provided close to the discharge lamp 3.

As a phase control method to eliminate such drawbacks, a method of detecting and controlling the phase of the lamp current is being researched. This method utilizes the property that the internal conductance of a discharge lamp is large immediately after starting, and decreases as the lamp reaches its rated value, so that the phase of the lamp current is delayed immediately after starting compared to when it is rated. As mentioned above, FIGS. 2a and 2b are comparison diagrams of the conduction phase θ of the AC control element 4 when the input current is constant immediately after starting and at the rated time, respectively. For the commutation phase angle T until Ila commutates,
Looking at the relationship between the off-period ΔT of the AC control element 4, it is necessary to increase the off-period ΔT immediately after startup (see Figure 2 a), and reduce the off-period ΔT as it moves to the rated value. I understand.
If we follow this relationship along with the startup process, we will find that
It can be seen that the result is as shown in Figure 4. Conversely, if the phase is controlled from point A to point B, constant input starting is possible. In FIG. 4, the horizontal axis indicates the commutation phase angle Ti (deg) of the lamp current Ila, and the vertical axis indicates the off period ΔTi (deg) of the AC control element 4.
In the figure, point A indicates immediately after starting, and point B indicates the time of rated operation. The measurement conditions were that the discharge lamp 3 was a 400W mercury lamp, the impedance voltage of the current limiting impedance 2 was 80V/33A, the current voltage Vs was 200V, and the conduction phase of the triac 4 could be controlled arbitrarily by an external trigger. This is the case when the input current is 2.4A.

When the discharge lamp 3 is started under such control conditions, the following problems occur. That is, the AC control element 4
If the conduction phase θ of is fixed at point A and then controlled from point A to point B due to changes in lamp conditions, the lamp current Ila waveform will change immediately after commutation phase T of lamp current Ila becomes small. Positive/negative asymmetry may occur, and the asymmetric waveform not only causes a flickering phenomenon during the starting process, but also causes the disadvantage of not reaching the rated point. Therefore, it is necessary to add a convergence condition for the conduction phase θ of the AC control element 4 to the above control conditions (the process from point A to point B in FIG. The present invention has been filed to solve the above drawbacks by improving the control conditions of the commutation phase T and the off period ΔT of the AC control element. In other words, an AC control element is connected to the commercial power source.
A current limiting impedance element and a discharge lamp are connected in series, and the conduction phase of the AC control element is set according to the lamp current commutation phase angle from the zero cross phase of the commercial power supply voltage until the lamp current commutates. In a discharge lamp constant input lighting device having a control circuit that controls every half cycle, the conduction phase of the AC control element for the current half cycle is set in accordance with the lamp current commutation phase angle immediately before the current half cycle to be controlled. In such a lighting device, an asymmetrical waveform in the starting process has been improved, but the reliability of the AC control element during glow discharge is not considered. Of course, if a sufficient amount of time has passed, the AC control element conduction phase convergence effect due to the relationship between the lamp current commutation phase angle Ti _-1 immediately before the current half cycle and the off period ΔTi of the AC control element during the current half cycle Although the conduction phase is fixed, a large stress is applied to the AC control element until then, which has the drawback of significantly lowering reliability. Therefore, when glow discharge occurs, it is necessary to fix the conduction phase of the AC control element by some means, but if it is forcibly fixed with a timer after the power is turned on, the heater current will not be sufficient for high-pressure sodium lamps. This means that the engine cannot be started because it cannot be obtained.

The present invention has been made in view of these points,
The purpose of this is to suppress inrush current when starting up mercury lamps and metal halide lamps (i.e. during glow discharge), and to obtain an appropriate preheating current to the heater when starting up high-pressure sodium lamps. An object of the present invention is to provide a discharge lamp lighting device capable of stable and reliable constant-input starting by suppressing inrush current in the same way as mercury lamps, metal halide lamps, and the like.

In order to improve the reliability of the AC control element 4 during the glow discharge period, the conduction phase of the element 4 may be limited. The present invention detects the conduction phase and fixes the conduction phase using a timer for a certain period of time from when the conduction phase exceeds a preset upper limit.

In the case of high-pressure sodium lamps, a sufficient heater current must flow through the heater resistor immediately after the power is turned on, so the off-period ΔTi of the AC control element 4 needs to be much smaller than the off-period ΔTi that should be controlled immediately after the lamp starts. be. In addition, immediately after the power is turned on, the lamp current commutation phase Ti _-1 is due to the high resistance of the heater.
Go much further forward than immediately after the lamp starts. This situation is shown in Figure 4. Point A in the figure indicates a preheating current of 0.8A, which is generally sufficient to start a high-pressure sodium lamp.
The phase conditions for obtaining . This heater current phase is determined by the main chiyoke coil 2 shown in FIG.
It is a steady phase determined only by the inductance and heater resistance, and is constant when the heater is preheated. Therefore,
During the heater preheating period, the preset upper limit of the conduction phase of the AC control element 4 is fixed at point A without exceeding one and a half cycles.
Then, when the heater switch opens and the lamp starts to start and enters glow discharge, the lamp current commutation phase T
Since the above-mentioned upper limit of the conduction phase may be exceeded due to the disturbance, the conduction phase may be fixed with a timer for a certain period of time from this point on.

FIG. 6 is a block diagram showing the function of a circuit implementing the present invention, and FIG. 7 is a timing chart of each part of the same. The lamp current commutation phase Ti _-1 immediately before the current half cycle in FIG.
The off period ΔTi of the AC control element 4 in the current half cycle is determined by subtraction counter 1 by subtracting the same number of clock pulses from the second clock 11 as the number of addition counts from the first clock 10.
The content of 2 is the lamp current commutation phase of the current half cycle.
The period is defined as the period after Ti until it becomes zero.
Note that the initial value n ₀ of the addition counter 13 is ΔT ₀ in FIG.
is the second clock count number corresponding to .

Next, the operation will be explained. When the power supply voltage zero cross detection circuit 14 detects the zero cross phase of the power supply voltage Vs, the contents of the addition counter 13 are preset to an initial value n ₀ during the period T ₀ in FIG. 4. Then, after the time _T0 has elapsed, the addition counter adds and counts the first clock pulse and continues counting until the lamp current Ila commutates. On the other hand, the subtraction counter 12 presets the output of the delay circuit 15 (latch circuit) from after the zero crossing of the power supply voltage Vs is detected until the lamp current Ila commutates. lamp current
At the same time as the commutation of Ila, the contents of the addition counter 12 are input to the delay circuit 15, and the subtraction counter 12 starts subtracting the clock pulses of the second clock 11. Therefore, the subtraction counter 12 calculates the commutation phase angle of the lamp current Ila in the previous half cycle.
The number of first clock pulses corresponding to Ti _-1 will be subtracted. Then, the zero comparator circuit 16 outputs a pulse shown at c in FIG. 7 at the time when the content of the subtraction counter 12 becomes zero. This pulse c is generated at the conduction phase angle θ of the AC control element 4 determined by the constant input starting control condition Ti ₋₁ −ΔTi. 7b is a reference pulse generated by the reference pulse generation circuit 17, and the positive period is the prohibited phase of the conduction phase θ of the AC control element 4.

Therefore, in the current i-th half cycle, the output c of the zero comparison circuit 16 is outside the positive pulse of the reference pulse b, so it falls at the input of the reference pulse b and the pulse c output from the zero comparison circuit 16. The output e of the flip-flop (F.F) 18 which rises at the power supply voltage zero cross pulse a via the AND gate 19 does not become positive. And (i+1)
If the pulse c enters the positive pulse section of the reference pulse b in the half cycle, the AND gate 19 outputs a positive pulse. Therefore, this positive pulse (see e in Fig. 7) is output when the conduction phase θ of the AC control element 4, determined by the control condition Ti _-1 -ΔTi, enters the conduction prohibited zone. Become. The monostable multivibrator 20 is shown in FIG.
After receiving the positive pulse, it outputs a positive signal for several seconds as shown at f in FIG. When this positive signal of f is generated, the positive signal of d that has been input to the trigger pulse generation circuit 21 of the AC control element 4 is inhibited, and the OR gate 22 receives the following signal as shown in g in FIG. The signal of reference pulse b will be output. In Fig. 6, 23 is a lamp current commutation phase detection circuit, 24 is a NOT gate, and 25 and 26 are
It is an AND gate, and frame A is a conduction phase locking circuit during glow discharge. Further, the numbers a to g in the figure indicate the signal outputs a to g in FIG. 7, respectively.

In this way, even once a conduction phase exceeding a preset upper limit of the conduction phase is detected, it is prohibited, and the conduction phase of the AC control element is fixed at this upper limit phase for several seconds thereafter. Therefore, since the conduction phase of the AC control element is not forcibly fixed by a timer after the power is turned on as in the past, high-pressure sodium lamps can be started reliably.Furthermore, since the conduction phase is fixed during glow discharge, AC control is possible. Rush current to the element can be suppressed, and reliability of the element can be improved. Furthermore, as in the prior art, an excellent discharge lamp constant input lighting device can be provided in which the positive/negative asymmetry of the lamp current waveform during the starting process is quickly converged and no flickering phenomenon occurs.

[Brief explanation of drawings]

Fig. 1 is a principle circuit diagram of a discharge lamp constant input lighting device, Fig. 2 a and b are waveform diagrams of the lamp current and power supply voltage of the same discharge lamp, and a shows the state immediately after starting.
b indicates the rated state. Figure 3 is the principle circuit diagram of the phase control method that detects the lamp voltage.
The figure is an explanatory diagram showing the control conditions necessary for starting the high-pressure sodium lamp according to the present invention, Figure 5 is a principle circuit diagram of the present invention, Figure 6 is a block diagram showing the function of the control circuit of the present invention, Figure 7 is a time chart of each part of the same as above.

Claims (1)

[Claims] 1. An AC control element, a current limiting impedance element, and a discharge lamp are connected in series to a commercial power supply, and the AC control element In a discharge lamp constant input lighting device having a control circuit that controls the conduction phase of the current half cycle for each half cycle of the commercial power supply, the current half cycle A control circuit for controlling the conduction phase of the AC control element, and a control circuit for fixing the conduction phase for a certain period of time from when the conduction phase lags behind a fixed phase for each half cycle. Electric light constant input lighting device.