JPH0589988A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent thermal destruction of a high frequency oscillating circuit even if the rate of rise of lamp voltages with respect to the oscillation output of the high frequency oscillating circuit is lowered. CONSTITUTION:Lamp voltages at both ends of a discharge lamp 47 are divided by the voltage dividing circuits of capacitors 73, 74 and are then rectified and smoothed by a smoothing circuit comprising diodes 75, 76, a capacitor 77 and a resistance 78, and are fed to a safety circuit comprising Zener diodes 91, 92, the light emitting portion of a photocoupler 93, resistances 94, 95, a transistor 96 and a posistor 97. The posistor 97 is a temperature detecting element for detecting the temperature for an DC bypass resistance 50 and is thermally connected to the DC bypass resistance 50. Therefore, even if the rate of rise of the lamp voltages with respect to the oscillation output of a high frequency oscillating circuit is lowered, the resistance of the posistor 97 is increased by the heat of the resistance 50 and the oscillation frequency of the high frequency oscillating circuit is lowered through attenuation and regulation, thereby preventing thermal destruction of the high frequency oscillating circuit.

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 provided with a safety circuit for preventing thermal destruction of a high frequency oscillating circuit, and particularly when the rate of increase of the lamp voltage with respect to the oscillation output of the high frequency oscillating circuit decreases Also, the present invention relates to a discharge lamp lighting device capable of appropriately operating a safety circuit.

[0002]

2. Description of the Related Art Conventionally, fluorescent lamps have been commercialized as discharge lamps. A conventional discharge lamp lighting device for lighting such a discharge lamp is provided with a safety circuit in order to prevent damage to the discharge lamp due to a rise in lamp voltage and thermal destruction of the high frequency oscillation circuit.

FIG. 5 is a circuit diagram showing a discharge lamp lighting device provided with such a safety circuit.

An AC power supply voltage from the commercial AC power supply 101 is rectified and smoothed by a rectifying circuit 102 and a smoothing circuit 103, and then given to a high frequency oscillation circuit 104. The high-frequency oscillator circuit 104 creates a high-frequency current from the rectified power supply voltage and supplies the high-frequency current to the discharge lamp 106 while the oscillation output is controlled by the control circuit 105. Safety circuit 107
Detects the lamp voltage of the discharge lamp 106 and supplies a lamp abnormality detection signal to the control circuit 105 when the lamp voltage exceeds a predetermined value. When the lamp abnormality detection voltage is supplied, the control circuit 105 controls the high frequency oscillation circuit 104 to attenuate and adjust the oscillation output.

In such a conventional discharge lamp lighting device, when the safety circuit 107 supplies a lamp abnormality detection signal to the control circuit 105 when the lamp voltage exceeds a predetermined value, the lamp is used at the life of the discharge lamp. Discharge lamp 10 due to voltage rise
6 is prevented, and the high frequency oscillation circuit 104 is prevented from being thermally destroyed. However, if the ambient temperature of the discharge lamp becomes high or low even during the life of the discharge lamp in which this safety circuit should operate, the rise rate of the lamp voltage with respect to the oscillation output of the high frequency oscillation circuit 104 decreases, and the high frequency oscillation occurs. It becomes impossible to prevent the thermal destruction of the circuit 104.

[0006]

In the above-mentioned conventional discharge lamp lighting device, when the ambient temperature of the discharge lamp becomes high or low during the life of the discharge lamp, the lamp voltage with respect to the oscillation output of the high frequency oscillation circuit is changed. The rise rate decreases, and it becomes impossible to prevent thermal destruction of the high-frequency oscillator circuit.

Therefore, it is an object of the present invention to provide a discharge lamp lighting device capable of preventing thermal destruction of the high frequency oscillation circuit even when the rate of increase of the lamp voltage with respect to the oscillation output of the high frequency oscillation circuit decreases. It is what

[0008]

A discharge lamp lighting device according to the present invention according to claim 1 is a DC power supply, a high-frequency oscillator circuit for outputting the output from the DC power supply in an adjustable oscillation output state, and the high-frequency oscillator. A discharge lamp to which the output of the oscillation circuit is supplied, a lamp voltage of the discharge lamp is detected, and a safety circuit that outputs a lamp abnormality detection signal when this lamp voltage exceeds a set value, and a safety circuit from this safety circuit. A control circuit that attenuates and adjusts the oscillation output of the high-frequency oscillation circuit in response to a lamp abnormality detection signal, a DC bypass resistor that is provided in the high-frequency oscillation circuit and that bypasses the DC component of the high-frequency current, and this DC bypass resistor. And a circuit means for adjusting the oscillation output of the high-frequency oscillation circuit based on the temperature detection result of the temperature detection element. To.

[0009]

According to this structure, the temperature detecting element detects the temperature of the DC bypass resistor provided in the high frequency oscillation circuit and adjusts the oscillation output of the high frequency oscillation circuit based on the temperature detection result. Even when the rate of increase of the lamp voltage with respect to the oscillation output of the high frequency oscillation circuit decreases, thermal destruction of the high frequency oscillation circuit can be prevented.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting device according to the present invention.

In FIG. 1, reference numeral 41 denotes a commercial AC power supply, and the AC power supply voltage from the commercial AC power supply 41 is rectified and smoothed by a rectifying circuit 42 and a smoothing capacitor 43 forming a smoothing circuit. A high frequency oscillator circuit is connected to the smoothing capacitor 43. The high frequency oscillating circuit is of the one-stone self-excitation type voltage resonance type, in which the resonance capacitor 45 is connected in parallel to the primary winding 44a of the high frequency transformer 44, and the oscillation transistor 46 is connected to one end of the primary winding 44a.
The secondary winding 44b of the high-frequency transformer 44 has one end connected to the electrode at one end of the discharge lamp 47, and the other end connected via the capacitor 48 and the primary winding of the positive feedback current transformer 49 to the other end of the discharge lamp 47. Connected to the electrode. The other end of the secondary winding 44b of the high frequency transformer 44 is connected to the electrode at the other end of the discharge lamp 47 through the series connection of the DC bypass resistors 50 and 51. The DC bypass resistors 50 and 51 are for bypassing the DC component of the high frequency current. Discharge lamp 47
A startup capacitor 52 is connected in parallel with the. One end of the secondary winding of the positive feedback current transformer 49 is connected to the base of the transistor 46. Between the other end of the secondary winding of the transformer 49 and the collector of the transistor 46, capacitors 53, 5 for controlling the ON time of the transistor 46 are provided.
4, MOSFET 55 and resistor 56 are connected, and MO
The connection point between the SFET 55 and the resistor 56 and the transistor 4
A diode 57 and a resistor 58 for controlling the on-time are connected to the base of the transistor 6. The MOSFET 55 works as a variable resistor, and its gate has
A drive voltage is supplied. The resistance value of the MOSFET 55 can be controlled by its drive voltage.

The collector of the oscillation transistor 46 is provided with a control circuit for controlling the oscillation voltage of the oscillation transistor 46 to be constant. That is, the oscillation silane transistor 4
Between the collector and emitter of 6 is a diode 60 and a resistor 6
A peak voltage detection circuit including 1 and capacitors 62 and 63 is provided, and the peak voltage value obtained at the connection point between the resistor 61 and the capacitor 63 is input to the base of the switching transistor 64. The emitter of the transistor 64 is connected to the positive side of the power supply rectification circuit 42 via resistors 65, 66 and 67, and the collector of the transistor 64 is resistor 68,
It is connected to the negative electrode side of the power supply rectification circuit 42 via 69. The connection point of the resistors 68 and 69 is connected to the gate of the MOSFET 55. On the other hand, the base of the transistor 64 is connected to the negative side of the power supply rectifier circuit 42 via the bias resistors 70, 71, 72. The resistor 71 is a variable resistor, and by adjusting this, the bias value of the transistor 64 can be varied and the on-time of the transistor 46 can be adjusted.

On the other hand, a circuit for generating a high voltage when starting the lamp is provided between the electrodes of the discharge lamp 47. This high voltage generating circuit divides the lamp voltage across the discharge lamp 47 by a voltage dividing circuit of capacitors 73 and 74, and then rectifies and smoothes it by a smoothing circuit of diodes 75 and 76, a capacitor 77 and a resistor 78, and further It is led to the base of the switching transistor 81 through a delay circuit composed of 79 and a resistor 80. A diode 82 for preventing reverse charging of the capacitor 79 in the reverse direction is connected between the base and emitter of the transistor 81, and a capacitor 83, a resistor 84, and a light emitting portion of a photocoupler 85 are provided on the collector side of the transistor 81. Connected. Here, when the capacitor 79 is gradually charged after the power is turned on at the time of starting the lamp,
During the charging process, the base current is supplied to the transistor 81, the transistor 81 is turned on, a current flows through the transistor 81 through the light emitting portion of the photocoupler 85, and the light emitting portion of the photocoupler 85 emits light. This light emission continues for a certain period until the charging of the capacitor 79 is completed.

The optical signal from the light emitting portion of the photo coupler 85 is input to the light receiving portion of the photo coupler 85. One end of the light receiving portion of the photocoupler 85 is connected to the base of the transistor 64 via resistors 71 and 70, and the other end is connected to the negative side of the rectifier circuit 42. The collector of the transistor 86 is connected to the positive electrode side of the rectifier circuit 42 via the resistors 66 and 67, and the emitter is connected to the negative electrode side of the rectifier circuit 42. A resistor 87 is connected between the base and emitter of the transistor 86, and a capacitor 88 is connected between the collector and emitter of the transistor 86. The collector of the transistor 86 is connected to the cathode of the chainer diode 89, and the emitter of the transistor 86 is connected to
The anode of the Zener diode is connected via the resistor 90.

Light enters the light receiving portion of the photocoupler 85,
When the light receiving portion of the photo coupler 85 is turned on, the photo coupler 8
An electric current flows through the light receiving part of the transistor 5 and thereby the transistor 6
The base voltage of 4 drops, the transistor 64 turns on,
MOSF is generated by the voltage generated at the connection points 68 and 69 of the resistors.
The ET 55 is operated in the ON direction, the ON time of the oscillation transistor 46 is lengthened to increase the oscillation output, and the discharge lamp 4
Turn on 7. When the discharge lamp 47 is in a lighting state, the capacitor 79 completes charging, so that the transistor 81 is turned off because no current is supplied thereto, and thus the light emitting portion of the photocoupler 85 is turned off. Then, the light receiving portion of the photocoupler 85 also turns off, the transistor 64 also turns off, and the MOSFET 55
Also, the resistance value becomes large, and the oscillation output of the transistor 64 is set to the low output required for maintaining stable lighting.
After that, the charge charged in the capacitor 79 is discharged and flows into the light emitting portion of the photocoupler 85, so that the current instantaneously flowing in the light emitting portion of the photocoupler 85 is changed to the capacitor 8
It is not absorbed by 3 and the transistor 64 is not turned on. Therefore, the lighting state is kept stable, and an abnormal oscillation waveform does not occur in the transistor.

Next, a safety circuit when the lamp voltage exceeds a predetermined value will be described.

The lamp voltage across the discharge lamp 47 is divided by the voltage dividing circuit of the capacitors 73 and 74, and then the diode 7
5, 76, a capacitor 77, and a resistor 78 are used for rectification and smoothing, and Zener diodes 91 and 92, a light emitting portion of a photocoupler 93, resistors 94 and 95, and a transistor 96.
And a safety circuit consisting of a posistor 97. The cathode of the light emitting portion of the photocoupler 93 is connected to the anode of the diode 82, and the anode of the light emitting portion of the photocoupler 93 is connected to the cathode of the diode 76 via the anode / cathode path of the Zener diode 91. The Zener diode 91 and the photo coupler 93 are used in a conventional safety circuit.

In the present embodiment, the cathode of the Zener diode 91 is connected to the anode of the Zener diode 91 via the resistor 94 and the collector-emitter path of the transistor 96, while the cathode of the light emitting portion of the photocoupler 93 and the Zener diode 91 are connected. A voltage detection resistor 95 and a posistor 97 are connected in series between the cathodes of
The connection point between the resistor 95 and the posistor 97 is connected to the cathode of the zener diode 92,
Is connected to the base of the transistor 96. The posistor 97 is a temperature detecting element that detects the temperature of the DC bypass resistor 50.
Is thermally connected to, that is, thermally coupled to.

The optical signal from the light emitting portion of the photo coupler 93 is input to the light receiving portion of the photo coupler 93. The light receiving portion of the photocoupler 93 is connected between the collector and base of the transistor 86.

FIG. 2 is an explanatory view for explaining a method of thermally connecting the posistor to a resistor for inverter transformer bias.

The glass-enclosed posistor 97 has terminal pairs 111 and 112 at one end of the cylindrical case 110, while the resistor 50 has terminal pairs 121 and 122 at one end of the cylindrical case 120. is doing. The resistors 50 and the posistor 97 are adhered to each other by an adhesive 130, and the terminals 111, 112, 1 are connected to each other in a state where the case is erected.
21 and 122 are terminal insertion holes 132 and 13 of the substrate 131.
2, 132, 132 and soldering lands 133, 133, 133, 13 formed on the back surface of the substrate 131.
3 via solders 134, 134, 134, 134. With such a structure, the heat generated from the resistor 50 is transferred to the posistor 97.

The operation of such an embodiment will be described below.

If the lamp voltage does not exceed the Zener voltage of the Zener diode 91 when the ambient temperature of the discharge lamp 47 is room temperature, current does not flow in the light emitting portion of the photocoupler 93 and light is not emitted. The discharge lamp lighting device does not operate and performs a normal lighting operation. When the lamp voltage exceeds the Zener voltage of the Zener diode 91, a current flows in the light emitting unit of the photocoupler 93 to emit light, and the optical signal from the light emitting unit of the photocoupler 93 is input to the light receiving unit of the photocoupler 93. As a result, the collector-emitter of the transistor 86 is connected, the emitter voltage of the transistor 64 decreases, the gate voltage of the MOSFET 55 decreases, the resistance value of the MOSFET 55 also increases, and the oscillation output of the transistor 46 is set to a low output. The oscillation output of the high-frequency oscillator circuit is attenuated and lowered.

When the oscillation output of the high-frequency oscillator circuit increases at the end of the life of the discharge lamp and the ambient temperature of the discharge lamp is high or low, the lamp voltage relatively decreases, so that the high-frequency oscillator circuit oscillates. The lamp voltage does not exceed the Zener voltage of the Zener diode 91 because the rate of increase of the lamp voltage with respect to the output decreases. However, the power supply current flows through the lamp circuit, the voltage of the capacitor 48 rises, the resistance of the hosi- ter 97 increases due to the heat generation of the resistor 50, and the voltage at the connection point of the resistor 95 and the posistor 97 exceeds the zener voltage of the zener diode 92. , Transistor 9
When 6 is turned on, a current flows through the light emitting portion of the photocoupler 93 to emit light. As a result, the gate voltage of the MOSFET 55 decreases, the resistance value of the MOSFET 55 also increases, the oscillation output of the transistor is set to a low output, and the oscillation output of the high frequency oscillation circuit is attenuated and adjusted to decrease.

According to the present embodiment, even when the rate of increase of the lamp voltage with respect to the oscillation output of the high frequency oscillation circuit decreases at the end of the lamp life, the resistance of the resistor 97 increases due to the heat generation of the resistor 50, and the high frequency oscillation circuit Since the oscillation output is attenuated and lowered, the thermal breakdown of the high frequency oscillation circuit can be prevented. This makes it possible to provide the user with a highly safe discharge lamp lighting device.

FIG. 3 is an explanatory view showing a modification of the embodiment shown in FIG.

As the posistor 97, the same one as in the embodiment of FIG. 1 is used. On the other hand, the resistor 150 corresponding to the resistor 50 of FIG. 1 has terminals 14 at both ends of the cylindrical case 140.
1, 142. The resistors 140 and the posistor 97 are adhered to each other by an adhesive 100 and the terminals 111,
112, 141, 142 are the terminal insertion holes 15 of the substrate 151.
2, 152, 152, 152, and soldering lands 153, 153, 15 formed on the back surface of the substrate 151.
3, 153 via solders 154, 154, 154, 154.

With such a structure, the same effect as that of the embodiment of FIG. 2 can be obtained.

FIG. 4 is a circuit diagram showing another embodiment of the discharge lamp lighting device according to the present invention. The same components as those in FIG. 1 are designated by the same reference numerals and their description is omitted.

The difference in this embodiment lies in the safety circuit shown in FIG.
Resistors 94, 95, posistor 97, transistor 96,
Instead of providing the Zener diode 92, the variable resistor 7
1 and a resistor 72, a posistor 1 thermally coupled to the resistor 50.
97 is inserted.

In such an embodiment, when the oscillating output of the high frequency oscillating circuit is increased due to the life of the discharge lamp and the ambient temperature of the discharge lamp is high or low, the lamp voltage changes to that of the high frequency oscillating circuit 4. The ramp voltage does not exceed the Zener voltage of the Zener diode 91 because the rate of increase of the lamp voltage with respect to the oscillation output decreases. However, the resistance of the transistor 197 increases due to the heat generation of the resistance 50, the base voltage of the transistor 64 increases, the collector voltage of the transistor 64 decreases, the gate voltage of the MOSFET 55 decreases, and the resistance value of the MOSFET 55 also increases. The oscillation output of the transistor 46 is set to a low output, and the oscillation output of the high frequency oscillation circuit decreases.

As a result, the same effect as that of the embodiment shown in FIG. 1 can be obtained.

[0034]

According to the present invention, even when the rate of increase of the lamp voltage with respect to the oscillation output of the high frequency oscillation circuit decreases,
Since it is possible to prevent thermal destruction of the high frequency oscillation circuit, a highly safe discharge lamp lighting device can be provided to the user.

[0035]

[Brief description of drawings]

[0036]

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting device according to the present invention.

[0037]

FIG. 2 is an explanatory diagram illustrating a method of thermally connecting the posistor of FIG. 1 to a resistor.

[0038]

FIG. 3 is an explanatory view showing a modification of the embodiment of FIG.

[0039]

FIG. 4 is a circuit diagram showing another embodiment of the discharge lamp lighting device according to the present invention.

[0040]

FIG. 5 is a circuit diagram showing a conventional discharge lamp lighting device.

[0041]

[Explanation of symbols]

 41 Commercial AC Power Supply 42 Rectifier Circuit 43 Smoothing Capacitor 44 High Frequency Transformer 47 Discharge Lamp 50 DC Bias Resistor 97 Posistor

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[Procedure amendment]

[Submission date] October 21, 1991

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

Claims (3)

[Claims] 1. A DC power supply, a high-frequency oscillation circuit that outputs an output from the DC power supply in an adjustable oscillation output state, a discharge lamp to which the output of the high-frequency oscillation circuit is supplied, and a lamp voltage of the discharge lamp. The safety circuit outputs a lamp abnormality detection signal when this lamp voltage exceeds the set value, and the oscillation output of the high-frequency oscillation circuit is attenuated and adjusted according to the lamp abnormality detection signal from this safety circuit. Control circuit, a DC bypass resistor provided in the high frequency oscillation circuit for bypassing the DC component of the high frequency current, a temperature detection element for detecting the temperature of the DC bypass resistance, and a temperature detection result of the temperature detection element. And a circuit means for adjusting the oscillation output of the high-frequency oscillation circuit based on the above. 2. A DC power supply, a high-frequency oscillation circuit that outputs an output from the DC power supply in an adjustable oscillation output state, a discharge lamp to which the output of the high-frequency oscillation circuit is supplied, and a lamp voltage of the discharge lamp. The safety circuit outputs a lamp abnormality detection signal when this lamp voltage exceeds the set value, and the oscillation output of the high-frequency oscillation circuit is attenuated and adjusted according to the lamp abnormality detection signal from this safety circuit. Control circuit, a DC bypass resistor provided in the high frequency oscillation circuit for bypassing the DC component of the high frequency current, a temperature detection element for detecting the temperature of the DC bypass resistance, and a temperature detection result of the temperature detection element. And a circuit means for adjusting the oscillation output of the high-frequency oscillation circuit by adjusting the set value of the safety circuit based on Apparatus. 3. A DC power supply, a high-frequency oscillation circuit that outputs the output from the DC power supply in an adjustable oscillation output state, a discharge lamp to which the output of the high-frequency oscillation circuit is supplied, and a lamp voltage of the discharge lamp. The safety circuit outputs a lamp abnormality detection signal when this lamp voltage exceeds the set value, and the oscillation output of the high-frequency oscillation circuit is attenuated and adjusted according to the lamp abnormality detection signal from this safety circuit. Control circuit, a DC bypass resistor provided in the high frequency oscillation circuit for bypassing the DC component of the high frequency current, a temperature detection element for detecting the temperature of the DC bypass resistance, and a temperature detection result of the temperature detection element. Circuit means for adjusting the oscillation output of the high frequency oscillation circuit by adjusting the attenuation rate of the attenuation adjustment of the control circuit based on the above. Lamp lighting device.