JPH0714686A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To generate high voltage and to start an electric discharge lamp without a heavy load on a switching element by making a saturable reactor connected to the electric discharge lamp in series non-saturated at the time of starting operation and saturable at the time of lighting operation. CONSTITUTION:A saturable reactor L2 is in a non-saturated condition when an electric discharge lamp 3 is started. An inverter circuit 2 is operated in the vicinity of a resonance frequency determined by an inductor L2 and a capacitor C, while a resonance condition is induced in a closed circuit, and high voltage is generated on both terminals of the electric discharge lamp 3. When a load side is seen from the circuit 2, the reactor LS having high inductance value while the reactor LS is in a non-saturated condition and an inductor L1, and a parallel resonance circuit consisting of the capacitor C and the inductor L2, are connected in series. A large current flows in the electric discharge lamp 3 in a lighted condition, and the reactor LS becomes saturated, while the inductance value is reduced. The output current of the circuit 2 is reduced at the time of starting, and the electric discharge lamp can be started without a heavy load on the switching element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device having a saturable reactor in series with a high frequency.

[0002]

2. Description of the Related Art FIG. 10 shows a circuit diagram of a conventional example. The input power supply Vs is converted into a DC voltage by the DC power supply 1, and this DC voltage is converted into a high frequency voltage by the inverter circuit 2 and applied to the discharge lamp 3 via the inductor L and the capacitor C. The frequency of the inverter circuit 2 changes during startup before the discharge lamp 3 causes dielectric breakdown and during lighting after the dielectric breakdown occurs. Since the discharge lamp 3 is in a high impedance state at startup, the circuit of FIG.
Is equivalent to the circuit of, and the inverter circuit 2 has an inductor L
And resonance frequency 1 / {2π√ (L
C)}, the inductor L and the capacitor C are brought into a series resonance state, and the discharge lamp 3
A high voltage is applied to both ends of the discharge lamp 3 to start the discharge lamp 3. When the discharge lamp 3 is turned on, the discharge lamp 3 operates at a frequency that provides the required output of the discharge lamp 3. Figure 1 shows the waveforms of the output voltage and output current of the inverter circuit 2 during startup and lighting.
Shown in 2. FIG. 12A shows the output voltage during lighting, and FIG.
12B shows the output current at lighting, FIG. 12C shows the output voltage at startup, and FIG. 12D shows the output current at startup.

[0003]

In the above-mentioned conventional example, since LC series resonance is utilized at the time of starting, it is necessary to flow a large current through the LC resonance circuit in order to generate a high voltage. However, there is a problem that the load on the switching element of the inverter is heavy. The present invention has been made in order to solve such a problem, and an object of the present invention is to generate a high voltage and start an electric discharge lamp without burdening a switching element. An object is to provide an electric lamp lighting device.

[0004]

In the discharge lamp lighting device of the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, a DC power supply 1 and an output from the DC power supply 1 And an inverter circuit 2 for converting into a discharge circuit, and a load circuit for supplying the output from the inverter circuit 2 to the discharge lamp 3.
The load circuit includes a saturable reactor Ls and a first inductor L ₁ that are connected in series to the discharge lamp 3, a capacitor C and a second inductor L ₂ that are connected in parallel to the discharge lamp 3, and during start-up operation. It is characterized in that the saturable reactor Ls is in a non-saturated state and operates in a saturated state during lighting operation. In addition, the saturable reactor L during lighting operation
It is preferable to include means for adjusting the inductance value of s.

[0005]

According to the present invention, during the starting operation of the discharge lamp 3,
Since the saturable reactor Ls is in a non-saturated state, the inductance value is high, the output current of the inverter circuit 2 can be extremely reduced, and the saturable reactor Ls is in a saturated state during the lighting operation. The output current of the circuit 2 can be increased. Further, the light output of the discharge lamp 3 can be adjusted by adjusting the inductance value of the saturable reactor Ls during the lighting operation. A lighting device using a saturable reactor is disclosed in Japanese Patent Laid-Open No. 4-126399, but this is one in which the saturable reactor is saturated only immediately after lighting, and the saturable reactor is usually in an unsaturated state. On the other hand, according to the present invention, the saturable reactor is in a non-saturated state at the time of starting the discharge lamp and is in a saturated state at the time of lighting.

[0006]

1 is a circuit diagram of a first embodiment of the present invention.
In this embodiment, the saturable reactor Ls is in a non-saturated state when the discharge lamp 3 is started. Inverter circuit 2
Operates near the resonance frequency 1 / {2π√ (L ₂ C)} determined by the inductor L ₂ and the capacitor C. As a result, a resonance state is induced in the closed circuit formed by the inductor L ₂ and the capacitor C, a high voltage is generated at both ends of the discharge lamp 3, and the insulation breakdown of the discharge lamp 3 is caused. At this time, when the load side is viewed from the inverter circuit 2, the saturable reactor Ls is in a non-saturated state, Ls having a high inductance value, the inductor L ₁ , and the capacitor C.
Since the parallel resonant circuit including the inductor L ₂ and the inductor L ₂ is connected in series, the output current of the inverter circuit can be extremely reduced. On the other hand, in the lighting state, a large current flows through the discharge lamp 3, so that the saturable reactor Ls is saturated and has a small inductance value. If the equivalent resistance of the discharge lamp 3 is R, and the inductor L ₂ is set so that ωL ₂ >> R, the circuit of FIG. 1 is considered to be almost equivalent to the circuit of the conventional example shown in FIG. be able to.

FIG. 2 is a circuit diagram of a second embodiment of the present invention. In the present embodiment, the saturable reactor Ls is provided with a secondary winding, and a direct current between the DC power supply 1 and the inverter circuit 2 is caused to flow through the secondary winding, so that the saturable reactor Ls is saturated more reliably in the lighting state. Therefore, the operation during lighting can be ensured. Other configurations and operations are similar to those of the first embodiment.

FIG. 3 is a circuit diagram of a third embodiment of the present invention. In the present embodiment, the saturable reactor Ls is provided with a secondary winding, and a direct current given from the control circuit 4 is passed through the secondary winding, whereby the output adjustment at the time of lighting is achieved in addition to the effect shown in the first embodiment. Can be done easily.

By the way, when the discharge lamp 3 is started, 100 KH
When a high frequency voltage exceeding z is applied, as shown in FIG. 4, a switch SW is provided in the vicinity of the lamp socket, the contact of which is switched depending on whether the lamp is mounted or not mounted. The non-wearing state is detected to control the operation of the igniter 5. As described above, when the switch SW for detecting whether the discharge lamp is mounted or not mounted is newly added to the lamp, the number of wires between the lighting device and the lamp also increases. Therefore, as shown in FIG. It is preferable to detect the mounting / non-mounting of the discharge lamp 3 by using a resistor Rd that detects a current flowing through the discharge lamp 3, stop the generation of a high-voltage pulse when the discharge lamp is not mounted, and improve safety. In the circuit of FIG. 5, the voltage generated in the resistor Rd for detecting the current flowing through the discharge lamp 3 is input to the detection circuit 6. The igniter 5 generates a high-voltage pulse for starting the discharge lamp 3 when the output of the detection circuit 6 is at a high level, and stops the high-voltage pulse at a low level.

The configuration of the detection circuit 6 is shown in FIG.
Voltage generated in the resistor Rd for detecting the current flowing to the discharge lamp is input to the comparator CP ₁ is compared with the reference voltages V ₁ through the integration circuit constituted by a resistor R ₁ and capacitor C _1, the reference voltage When V ₁ is exceeded, the output of the comparator CP ₁ becomes High level. Similarly,
Compared resistor R ₂ and is input to the comparator CP ₂ via an integration circuit constituted by the capacitor C ₂ and the reference voltage V _2, the comparator C when exceeding the reference voltage V ₂
The output of P ₂ becomes High level.

By the way, when considering only the high frequency component, the equivalent circuit of the tube lamp circuit and the discharge lamp when not lit can be represented as shown in FIG. Here, Ck is a stray capacitance of the tube lamp circuit, and Cd is a stray capacitance of the discharge lamp itself. Therefore, when the discharge lamp is started by the high-frequency high-voltage pulse, it can be seen that a voltage is generated in the resistor Rd that detects the current of the discharge lamp even if the discharge lamp does not cause dielectric breakdown. Further, when the discharge lamp is removed, the stray capacitance Cd is removed from the circuit of FIG. 7, the overall capacitance changes, and the voltage generated in the resistor Rd that detects the current of the discharge lamp also changes. The present invention utilizes this fact, and in FIG. 6, the output of the comparator CP ₂ becomes High when the discharge lamp 3 is mounted at the start-up operation, and becomes Low level when the discharge lamp 3 is removed. The reference voltage V ₂ is selected so that Further, when the discharge lamp 3 is turned on, the output of the comparator CP ₁ becomes H level.
The reference voltage V ₁ is selected so that it becomes the high level and becomes the low level while the light is off.

The operation of the circuit shown in FIG. 6 will be described below. First, when the discharge lamp is disconnected, the activation signal generation circuit TM generates a short pulse when the power is turned on. At this time, the outputs of the comparators CP ₁ and CP ₂ are both Lo
w level. Therefore, the output of the negation circuit N ₁ is High.
The output of the level and OR circuit OR is the start signal generation circuit T
The same waveform as the output of M appears. Therefore, AND circuit A ₁
The same waveform as that of the output of the start signal generation circuit TM appears in the output of. This becomes the output of the detection circuit 6, and the igniter 5 generates a high-voltage pulse for starting the discharge lamp only during the pulse width generated by the starting signal generation circuit TM. However,
Since the reference voltages V ₁ and V ₂ are set as described above,
The outputs of the comparators CP ₁ and CP ₂ are both kept at the Low level, and the high voltage pulse for activation is stopped at the same time as the fall of the activation signal.

Next, when the discharge lamp is mounted, the process of generating a high-voltage pulse after the power is turned on is the same as when the discharge lamp is disconnected. When a high voltage pulse is generated, the output of the comparator CP ₂ becomes High level, and even after the activation signal falls, the outputs of the OR circuit OR and the AND circuit A ₁ both maintain the High level and generate a high voltage pulse. . When the discharge lamp causes insulation breakdown and goes into a lighting state, the output of the comparator CP ₁ becomes Hi.
Since the output of the NOT circuit N ₁ becomes Low level, the output of the AND circuit A ₁ becomes Low level, and the high voltage pulse is stopped. In this way, the high-voltage pulse is generated only when the discharge lamp is mounted.

Incidentally, there is Japanese Patent Application No. 5-25837 as a prior application having a means for detecting the current of a discharge lamp as in the present invention and paying attention to the stray capacitance of the discharge lamp at the time of startup. Differs from the present invention in that it switches the level of the reference voltage for lighting determination before and after the inrush current flowing at the time of dielectric breakdown of the discharge lamp.

FIG. 8 shows another embodiment. The inverter circuit 2 has a load circuit including an inductor L, a capacitor C and a discharge lamp 3. The voltage generated in the resistance Rd for current detection connected in series with the discharge lamp 3 is input to the detection circuit 6. The structure of the detection circuit 6 is shown in FIG. This circuit is almost identical to the circuit of FIG. 6 but with two separate outputs. The inverter circuit 2 outputs a high-frequency rectangular wave voltage, but the outputs O1 and O2 of the detection circuit 6 cause
It switches to the following three modes. First, outputs O1 and O2
Is low level, the inverter circuit 2 stops oscillating. Next, output O1 is output O at Low level.
When 2 is at the high level, the inverter circuit 2 oscillates at a frequency at which the series resonance of the inductor L and the capacitor C occurs. Further, when the outputs O1 and O2 are both at the high level, the inverter circuit 2 oscillates at a frequency that provides the output required by the discharge lamp 3. As a result, the same effect can be obtained even when the inverter circuit 2 is used instead of the igniter 5.

[0016]

According to the invention of claim 1, in a lighting device for converting an output from a DC power supply into a high frequency by an inverter circuit and supplying the high frequency to a discharge lamp, a saturable reactor connected in series to the discharge lamp and a first step. 1, an inductor, a capacitor connected in parallel with the discharge lamp, and a second inductor,
Since the saturable reactor was in a non-saturated state during startup operation, the series impedance of the discharge lamp was high and the lamp current was limited, and when it was in the saturated state during lighting operation, the series impedance of the discharge lamp was low. ,
Due to the resonance action of the LC resonance circuit, the discharge lamp can be lit with a sufficient lamp current.

Further, according to the invention of claim 2, since the means for adjusting the inductance value of the saturable reactor at the time of lighting operation is provided, the lamp current flowing in the discharge lamp can be adjusted and the light output can be made variable. The effect is that you can.

Next, according to the invention of claim 3, in a discharge lamp lighting device for starting a discharge lamp by generating a high-frequency high-voltage pulse, by detecting the current of the discharge lamp before starting lighting, the discharge lamp is discharged. Since it is determined whether or not the electric lamp is installed and the generation of the high voltage pulse is stopped when the electric discharge lamp is not installed, it is not necessary to provide a separate switch for detecting the presence or absence of the electric discharge lamp. There is an effect that the structure of the lighting device can be simplified.

Further, according to the invention of claim 4, the means for detecting the current of the discharge lamp comprises a resistor connected in series with the discharge lamp, and the voltage generated at both ends of this resistor is larger than the reference voltage. In this case, since it is configured to determine that the discharge lamp is mounted, it is possible to determine whether or not the discharge lamp is mounted by a simple electronic circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the invention of claim 1;

FIG. 2 is a circuit diagram of another embodiment of the invention of claim 1;

FIG. 3 is a circuit diagram of still another embodiment of the invention according to claim 1;

FIG. 4 is a circuit diagram of a conventional discharge lamp lighting device.

FIG. 5 is a circuit diagram of an embodiment of the invention of claim 3;

FIG. 6 is a circuit diagram of a detection circuit used in an embodiment of the invention of claim 3;

FIG. 7 is an equivalent circuit diagram when the discharge lamp lighting device is activated.

FIG. 8 is a circuit diagram of another embodiment of the invention of claim 3;

FIG. 9 is a circuit diagram of a detection circuit used in another embodiment of the invention of claim 3;

FIG. 10 is a circuit diagram of a conventional discharge lamp lighting device.

FIG. 11 is an equivalent circuit diagram when the conventional discharge lamp lighting device is started.

FIG. 12 is a waveform diagram showing operations of the conventional discharge lamp lighting device at the time of startup and lighting.

[Explanation of symbols]

1 DC power supply 2 Inverter circuit 3 Discharge lamp Ls Saturable reactor L ₁ 1st inductor L ₂ 2nd inductor C Capacitor

Claims (4)

[Claims] 1. A DC power supply, an inverter circuit for converting the output from the DC power supply into a high frequency, and a load circuit for supplying the output from the inverter circuit to a discharge lamp, wherein the load circuit is connected in series to the discharge lamp. It comprises a saturable reactor and a first inductor that are connected, a capacitor and a second inductor that are connected in parallel to the discharge lamp, and the saturable reactor is in a non-saturated state during start-up operation and in a saturated state during lighting operation. A discharge lamp lighting device characterized by the above. 2. The discharge lamp lighting device according to claim 1, further comprising means for adjusting an inductance value of the saturable reactor during a lighting operation. 3. A discharge lamp lighting device for starting a discharge lamp by generating a high-frequency high-voltage pulse, comprising means for detecting the current of the discharge lamp, and detecting the current of the discharge lamp before the start of lighting. A discharge lamp lighting device, comprising: means for determining whether or not a discharge lamp is mounted, and stopping the generation of a high-voltage pulse when it is determined that the discharge lamp is not mounted. 4. The means for detecting the current of the discharge lamp comprises a resistor connected in series with the discharge lamp, and the discharge lamp is mounted when the voltage generated across the resistor is larger than a reference voltage. The discharge lamp lighting device according to claim 3, wherein the discharge lamp lighting device is configured to be determined to be present.