JPH0311075B2 - - Google Patents

Description

Detailed Description of the Invention The present invention connects an AC control element such as a triac, a current limiting reactor such as a choke coil, and a discharge lamp such as a high-pressure mercury lamp in series to an AC power source, thereby adjusting the conduction phase angle of the AC control element. The present invention relates to an improvement of a discharge lamp lighting device configured to control a lamp current value every half cycle of an AC power source by appropriately adjusting it according to the operating state of a discharge lamp lighting circuit.

In the above-mentioned discharge lamp lighting device, part of the current limiting action by the current limiting reactor is performed by a semiconductor element such as an AC control element, so the entire device is small and lightweight, and the conduction phase of the AC control element is The lamp current and lamp power of a discharge lamp can be appropriately controlled by adjusting the angle appropriately according to the operating status of the discharge lamp lighting circuit. It is rapidly becoming popular as a lighting device for electric lights.

As an example of such a discharge lamp lighting device, as shown in FIG. A reference voltage circuit 5 that detects a signal that changes depending on the operating state of the AC control element 2, for example, the voltage that is the sum of the voltage across the AC control element 2 and the voltage across the current limiting reactor 3, and uses it as a reference signal.
and a timer circuit 6 that charges and discharges the capacitor at a predetermined phase angle every half cycle of the AC power supply voltage.
a comparison/pulse generation circuit 7 which compares the charging voltage of the capacitor of the timer circuit 6 with the reference voltage of the reference voltage circuit 5 and generates a trigger pulse to make the AC control element 2 conductive when the two values match;
A device equipped with the following has been proposed. In such a lighting device, when the AC power supply 1 is turned on and the power supply voltage [Fig. 2 a] is applied to the lighting circuit, a circuit that detects the turn-off phase of the AC control element 2 is activated.
Turn-off phase of the AC control element 2 [Fig. 2b]
The capacitor of the timer circuit 6 begins to be charged in synchronization with . When this charging voltage [Fig. 2 c] matches the value of the reference voltage V _n of the reference voltage circuit 5, the comparison/pulse generation circuit 7 operates to generate a trigger pulse [Fig. 2 d], and the AC control element 2 becomes conductive. Therefore, a phase-controlled lamp current [Fig. 2e] flows. After the discharge lamp has stabilized, when the lamp power of the discharge lamp increases or decreases due to fluctuations in the power supply voltage, the reference voltage V _n also increases or decreases to V _n1 or V _n2 , so the trigger pulse generation phase angle also changes backward or forward. The lamp power is held constant to reduce or increase the lamp current. FIG. 3 shows a specific embodiment of the lighting device as described above, in which the voltage that is the sum of the voltage across the AC control element 2 and the voltage across the current limiting reactor 3 is detected by the isolation transformer 8, and the rectifier circuit 9 and a programmable union transistor (hereinafter referred to as
PUT) 12 is input as a reference voltage, while the capacitor 16 is rapidly charged via the diode 15 from another isolation transformer 13 and rectifier circuit 14 connected to the AC power supply 1, and the charging voltage of the capacitor 16 is set to a predetermined voltage. When the value of 1 is reached, the capacitor 1 is
6 is charged slowly, and the value of the reference voltage is set so that the charging voltage of the capacitor matches the reference voltage in this region where the capacitor is charged slowly.

Such a lighting device, as shown in Fig. 4,
Since the charging voltage of the capacitor and the reference voltage are compared in the part where the capacitor of the timer circuit is slowly charged, that is, in the part A of the capacitor charging voltage curve, the range of change in the reference voltages V _n1 and V _n2 is small. Also, since the range of change in the trigger pulse generation phase angles θ ₁ and θ ₂ is large, the lamp current can be sufficiently controlled without amplifying the reference voltage. Also,
When slowly charging the capacitor, since the voltage source of the reference voltage circuit charges the capacitor in response to changes in the reference voltage, the range of change in the reference voltages V _n1 and V _n2 is the same, that is, V _n1 −V. Even if ₀ = V ₀ - V _n2, the width of change in trigger pulse generation phase angle θ ₁ and θ ₂ is θ ₁ - _{θ 0}
<θ ₀ −θ ₂ and the control area of lamp current B is S ₁ =
S ₂ , it is possible to accurately control the lamp power. In addition, since the reference voltage is taken out from both ends of the series circuit of the AC control element and the current limiting reactor, the reference voltage at the time of starting the discharge lamp is a high value, and the trigger pulse generation phase angle is shifted backwards, so the lamp at the time of starting the lamp. This has the advantage of keeping the current low.

However, such a lighting device has the following problems. That is, the relationship between lamp voltage and lamp power when a discharge lamp is lit by the lighting device is as shown in FIG. It has a constant current characteristic that the power also increases linearly. For this reason, there is no particular problem when lighting a high-pressure mercury lamp whose lamp voltage remains almost constant until the end of its life, but when lighting a high-pressure sodium lamp or metal halide lamp, which has the characteristic that the lamp voltage increases at the end of its life. When a discharge lamp approaches the end of its lifespan, excessive lamp power is applied to the discharge lamp, which may cause damage to the discharge lamp.
In order to eliminate this drawback, it may be possible to add a circuit that detects the lamp voltage and controls it to prevent excessive input, but this would result in a complicated configuration and pose a problem in terms of reliability of circuit operation.

The present invention has been made in view of the above points, and has the advantages of the previously proposed lighting device, that is, sufficient and accurate current and power control can be performed without using an amplifier or other special equipment, Without sacrificing the advantage of being able to keep the lamp current low during startup, the lamp voltage-lamp power characteristic approaches the ideal shape, and even when using high-pressure sodium lamps or metal halide lamps, there is no overload. This is an improvement.

FIG. 6 shows a specific circuit example of the discharge lamp lighting device according to the present invention. In the figure, 1 is an AC power supply,
A discharge lamp 2, a current limiting reactor 3, and an AC control element 4 are connected in series to this, and these constitute a lighting circuit. Reference numeral 5 denotes a high impedance element connected in parallel with the AC control element 4, which is connected for the purpose of preventing the discharge lamp 2 from going out by passing a small amount of current through the lighting circuit even when the AC control element 4 is non-conductive. It is something that The current limiting reactor 3
An isolation transformer 6 is connected to both ends of the series circuit of the AC control element 4 and the AC control element 4. On the output side of the isolation transformer 6, a rectifier circuit 7, a diode 8, a voltage dividing resistor 9,
The gate of PUT11 is connected via 10. Further, another isolation transformer 12 is connected to the AC power supply 1, and a diode 15 is connected to the output side of the isolation transformer 12 via a rectifier circuit 13, and one end of the diode 15 is connected in series with the voltage dividing resistors 9 and 10. connected to one end of the circuit. These are the voltage that is the sum of the voltage across the current limiting reactor 3 and the voltage across the AC control element 4, or the power supply voltage is detected and PUT
A reference voltage circuit is configured to apply a reference voltage to the 11 gate electrodes. Further, a resistor 16 and a capacitor 17 are connected to both ends of the voltage dividing resistors 9 and 10.
A CR time constant circuit is connected, and a capacitor 17 of this circuit is connected to a diode 20 and an impedance 21 as necessary from the output side of the isolation transformer 12 through a constant voltage circuit consisting of a resistor 18 and a zener diode 19. It is configured so that it can also be charged from a bypass circuit consisting of. These constitute a timer circuit for charging the capacitor 17 at a predetermined phase angle every half cycle of the AC power supply voltage and applying the charging voltage to the anode of the PUT 11 as an input. Further, a turn-off phase detection circuit 24 of the AC control element 4 is connected to both ends of the AC control element 4 via an insulation transformer 22 and a rectifier circuit 23. This turn-off phase detection circuit 24 functions to give a signal to the timer circuit so that charging of the capacitor 17 is started in synchronization with the turn-off phase of the AC control element 4. The turn-off phase detection circuit 24 uses the rectifier circuit 13 as a power source via the resistor 14.

Next, the operation of the lighting device having such a circuit configuration will be explained. First, when the AC power supply 1 is turned on, voltage is applied to the discharge lamp 2 through a circuit consisting of the discharge lamp 2, the current limiting reactor 3, and the high impedance element 5, and the discharge lamp 2 starts. Immediately after the discharge lamp starts, a voltage almost equal to the power supply voltage is applied to the current limiting reactor 3.
is applied to both ends of the series circuit of the AC control element 4, so if the output level from the isolation transformer 12 is set lower than the output level from the isolation transformer 6,
A reference voltage based on the sum of the voltage across the current limiting reactor 3 and the voltage across the AC control element 4 is applied to the gate of the PUT 11 via the diode 8. On the other hand, since a voltage is also applied to the timer circuit at the same time as the AC voltage 1 is applied, the turn-off phase detection circuit 24 also operates, and charging of the capacitor 17 is started in synchronization with the turn-off phase of the AC control element 4. In this case, first, the capacitor 17 is rapidly charged mainly from the output side of the isolation transformer 12 through a bypass circuit consisting of a diode 20 and an impedance 21 to a constant voltage value set by a resistor 18 and a zener diode 19. After reaching a certain voltage value, it is slowly charged from the voltage source of the reference voltage circuit through the resistor 16 in response to the reference voltage. In this case, the change in the charging voltage of the capacitor 17 is as shown in FIG. 4 in the present invention, and as a result, sufficient current and power control can be performed without amplifying the reference voltage, and The present invention has the advantage that accurate current and power control can be performed without using means such as limiting the upper limit value of voltage, and that the lamp current at the time of starting can be kept low. For example, even if a high-pressure sodium lamp or metal halide lamp is used, safe and ideal current and power control can be performed until the end of the discharge lamp's life in the following manner. That is, in the lighting device according to the present invention, immediately after starting the discharge lamp 2, the voltage that is the sum of the voltage across the current limiting reactor 3 and the voltage across the AC control element 4 is applied to the PUT 11 as a reference voltage via the isolation transformer 6. However, when the lamp voltage of the discharge lamp 2 gradually increases and reaches a predetermined value, the output level of the isolation transformer 6 and the output level of the isolation transformer 12 connected to the AC power supply 1 match, and When the lamp voltage increases, a voltage corresponding to the power supply voltage is applied to the gate of the PUT 11 via the diode 15. If the power supply voltage fluctuates in such a state, PUT11
Since both the gate voltage and the anode voltage of the timer circuit fluctuate, the relationship between the charging voltage of the capacitor of the timer circuit and the trigger pulse generation phase angle is as shown in FIG. However, the reference voltage will not fluctuate due to fluctuations in the lamp voltage. In other words, in the present invention, as shown in FIG. 7, the reference voltage is plotted on the vertical axis with the power supply voltage as a parameter, and the lamp voltage is plotted on the horizontal axis to show changes in the reference voltage. When taking out from both ends of the series circuit of AC control element 4 and AC control element 4, the reference voltage changes as the lamp voltage changes, as shown in the left part from the C-C' line, but the reference voltage limit switches to the AC power supply. In the part to the right of the C-C' line, the reference voltage does not change at all if the AC power supply voltage is constant. As a result, the relationship between lamp voltage and lamp power becomes a rainbow curve as shown in Figure 8, and the discharge lamp 2
Even if the lamp voltage increases at the end of its life, the discharge lamp will not be damaged due to excessive input. Note that the lamp voltage-lamp power characteristics shown in FIG. 8 cannot be achieved in this type of discharge lamp lighting device by simply switching the voltage source of the reference voltage to an AC power supply midway through. First, as in the present invention, the capacitor of the timer circuit is rapidly charged by the bypass circuit until its charging voltage reaches a certain value, and thereafter it is slowly charged in response to fluctuations in the reference voltage or power supply voltage. This can only be achieved by using a method of setting the reference voltage so that the charging voltage of the capacitor matches the reference voltage in this slow charging region.

As is clear from the above description, the discharge lamp lighting device according to the present invention has the following advantages. First, the capacitor of the timer circuit is rapidly charged mainly through the bypass circuit until its charging voltage reaches a certain value, and thereafter it is slowly charged in response to fluctuations in the reference voltage or power supply voltage. Since the reference voltage is set so that the charging voltage of the capacitor matches the reference voltage in the range where the capacitor is charged, sufficient control can be achieved without amplifying the reference voltage, and accurate control can be achieved without using a reference voltage limiting circuit. Moreover, the lamp current at startup can be kept low. Next, in addition to the above configuration, until the lamp voltage of the discharge lamp reaches a predetermined value, the voltage that is the sum of the voltage across the AC control element and the voltage across the current limiting reactor is detected and used as the reference voltage. When the voltage reaches a predetermined value, the power supply voltage is detected and used as the reference voltage, so in areas where the lamp voltage is high, the reference voltage does not fluctuate as the lamp voltage fluctuates, thus extending the life of the discharge lamp. Since the lamp voltage rise at the end of its life will not cause excessive input and will not damage the discharge lamp, accurate and ideal current and power control is possible even over a wide range of power supply voltage fluctuations and lamp voltage changes. It is.

Furthermore, the circuit configuration does not require a reference voltage amplification circuit or over-input prevention circuit as in the past, so the structure is simple and reliable, and it is small and low cost, which has only technical value. However, it also has great economic value and has great industrial utility value.

[Brief explanation of drawings]

Figure 1 is a basic circuit diagram of a conventional discharge lamp lighting device.
Figure 2 is a current/voltage waveform diagram of each part of the device during operation, Figure 3 is a specific circuit diagram of the device, and Figure 4 is a diagram of the current and voltage waveforms of each part during operation.
The figure shows the relationship between the change curve of the charging voltage of the capacitor in the timer circuit of the device and the control area of the lamp current.
Fig. 5 is a curve diagram showing the relationship between the lamp voltage and lamp power of the device, Fig. 6 is a specific circuit diagram of the discharge lamp lighting device according to the present invention, and Fig. 7 is a curve diagram showing the relationship between the lamp voltage and the reference voltage in the device. FIG. 8 is a curve diagram showing the relationship between lamp voltage and lamp power in the same device. In Fig. 6, 1... AC power supply, 2... discharge lamp, 3... current limiting reactor,
4... AC control element, 8, 15... Diode,
16...Resistor, 17...Capacitor, 20...Diode, 24...Turn-off phase detection circuit.

Claims (1)

[Claims] 1. A lighting circuit including an AC control element, a current limiting reactor, and a discharge lamp connected in series to an AC power supply, and a signal that changes depending on the operating state of the lighting circuit and a reference voltage. and a timer circuit that charges and discharges a capacitor at a predetermined phase angle every half cycle of the AC power supply voltage, and compares the charging voltage of the capacitor of the timer circuit with the reference voltage of the reference voltage circuit. In the device configured to generate a trigger pulse for the AC control element when the two values match, the reference voltage circuit generates a voltage that is the sum of the voltage across the AC control element and the voltage across the current limiting reactor. and a circuit to detect the power supply voltage, and from the time the discharge lamp starts until the lamp voltage reaches a predetermined value, the voltage across the AC control element and the voltage across the current limiting reactor are added together. The voltage is detected and set as a reference voltage, and after the lamp voltage reaches a predetermined value, the power supply voltage is detected and set as the reference voltage. It consists of an RC time constant circuit consisting of a resistor and a capacitor connected to a bypass circuit connected to a separate voltage source, and the capacitor in the RC time constant circuit is charged until its charging voltage reaches a certain value. The capacitor is charged through the bypass circuit and thereafter charged by the voltage source of the reference voltage circuit, and the reference voltage is set so that it matches the reference voltage of the reference voltage circuit in a region where the charging voltage of the capacitor exceeds the certain value. A discharge lamp lighting device characterized in that: 2. The discharge lamp lighting device according to claim 1, wherein the capacitor of the timer circuit is configured to start charging in synchronization with the turn-off phase of the AC control element of the lighting circuit. lighting device. 3 In the discharge lamp lighting device according to claim 1, the bypass circuit for charging the capacitor of the timer circuit rectifies the AC power supply voltage and then connects a diode to the voltage source obtained through the constant voltage circuit. 1. A discharge lamp lighting device comprising a circuit connected to an impedance element according to the requirements.