JPH0266889A - Lighting-up device - Google Patents

Abstract

PURPOSE:To ensure protection of a circuit by furnishing a current sensing means and a reference signal generating means, comparing the sensed value with the reference value, and opening the power supply if judgement is such that any abnormal condition has arisen. CONSTITUTION:AC power is rectified by a diode bridge 1, and switch elements 3, 5 are turned on and off alternately by an inverter means, to produce high frequency voltage. A voltage dividing circuit consisting of a series circuitry of a thermo--sensitive element 21 and resistances 23, 25 is connected with the output side of the bridge 1, to generate a reference voltage. The current flowing in the switch elements 3, 5 of the inverter means is sensed by resistances 29, 31 as corresponding voltage signal VE. A protector circuit 27 compares this voltage signal VE with the reference voltage, and in the event of abnormality the currents of the switch elements 3, 5 become larger to release the inverter circuit from the power supply. Thereby the sensitivity of the circuit 27 is enhanced, and the circuit is protected certainly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lighting device, and in particular is capable of detecting an abnormal state such as an overload state with extremely high sensitivity and protecting a circuit. The present invention relates to a lighting device equipped with circuit protection means that causes fewer malfunctions during normal operation.

[Prior art] Conventionally, in a lighting circuit that drives a lamp load such as a halogen lamp, the current flowing through the inverter circuit is detected, and when this current exceeds a predetermined value, the oscillation of the inverter circuit is stopped to protect the circuit. was doing.

[Problems to be Solved by the Invention] However, in such conventional devices, the sensitivity of the protection circuit is poor, and even if an overload condition occurs, such as when a load higher than the rated value is connected to the device, the overload cannot be prevented. If the load is not very large, the protection circuit will not necessarily operate.
In the worst case scenario, the unit would be destroyed. Furthermore, if the sensitivity of the protection circuit is increased, there is a problem that the protection circuit may malfunction, for example, when the power is turned on.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lighting device that has a high detection sensitivity for abnormal conditions and is equipped with a protection circuit that prevents malfunctions during normal operation or when power is turned on, in view of the problems with the conventional devices described above. It is in.

[Means for Solving the Problems] A lighting device according to aspect 1B of the present invention includes an inverter unit that generates a high-frequency power source for lamp lighting, and outputs a signal corresponding to a current flowing through a switch element of the inverter unit. a current detecting means, a reference signal generating means for generating a reference signal by dividing a predetermined power supply voltage by a voltage dividing circuit including a temperature sensing element such as a temperature sensitive resistor, an output signal of the current detecting means and the reference signal. protection circuit means for stopping the output of the inverter means based on the comparison with the inverter means.

Further, a lighting device according to a second aspect of the present invention includes: an inverter means for generating a high frequency power source for lamp lighting; a current detecting means for outputting a signal corresponding to a current flowing through a switch element of the inverter means; A protection circuit means for stopping the output of the inverter means based on a comparison between the output signal of the current detection means and a predetermined reference signal, and a timer means for stopping the operation of the protection circuit means for a predetermined period of time after power is turned on. It is characterized by

"Operation" In the lighting device according to the first aspect described above, for example, in an abnormal state of the shade where a load higher than the rated value is connected, the current flowing through the switch element of the inverter means increases,
For example, the output signal of the current detection means increases. The temperature of the circuit elements of the lighting device also increases, and the temperature sensing element responds to this temperature increase, for example by increasing its resistance and lowering the reference signal. As a result, the output signal of the current detection means rapidly becomes higher than the reference signal, and the operation of the protection circuit means stops the output of the inverter means, thereby protecting the circuit. Furthermore, in the lighting device according to the second aspect, since the timer means stops the operation of the protection circuit for a predetermined period of time after the power is turned on, malfunction of the protection circuit due to inrush current at startup, for example, is prevented. At the same time, the operating sensitivity of the protection circuit during steady state can be increased.

[Example] Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a lighting device according to an embodiment of the present invention. The device in the figure includes a diode bridge 1 that rectifies AC power source AC, switching transistors 3 and 5 that constitute an inverter circuit, a drive circuit 7 that drives each switching transistor 3 and 5, a starting circuit 9, a stabilizer 11, and a coupling capacitor. 13,15, Output Lance 1
It is equipped with 7th class.

A lamp load 19, such as a halogen lamp, is connected to the output transformer 17. Also, connected to the output side of the diode bridge 1 is a voltage dividing circuit for generating a reference voltage, which is constituted by a series circuit of a temperature sensing element 21 such as a temperature sensing resistor and a resistor 23.25.

Furthermore, resistors 29 and 31 are connected to the emitters of each switching transistor 3.5, and among these resistors, for example, the voltage across the resistor 31 and the reference voltage VRFr of the voltage divider circuit are connected to each other. Input protection circuit 2
7 is provided. In addition, as the temperature sensing element 21, the first
In the case shown in the figure, a positive temperature sensing element whose resistance value increases in accordance with temperature is used.

In the device shown in FIG. 1, an alternating current power source AC is rectified by a diode bridge 1 to generate a direct current power source, which is applied to various parts of the circuit. As a result, as is well known, each switching 1 transistor 3, 5 is alternately turned on and off by the action of the drive circuit 7 and starting circuit 9, thereby generating a high frequency voltage. This high frequency voltage is applied to the primary coil of output 1 to lance 17 via ballast 11 and coupling capacitor 13.15, and a lamp load connected to the secondary coil of output 1 to lance 17 is driven. In addition, when the inverter circuit is an automatic type, the high frequency voltage is fed back to the drive circuit 7 via the secondary coil provided in the ballast 11.

Further, the output voltage of the diode bridge 1 is divided by a voltage dividing circuit composed of a temperature sensing element 21, a resistor 23, and a resistor 25, and is applied as a reference voltage V to a protection circuit 27EF. On the other hand, the voltage across the emitter resistor 31 of the switching transistor 5 is input to the protection circuit 27 as the detection voltage VE. The protection circuit 27 protects these voltages
and (2) are compared, and if the detected voltage 11EE E (2) is lower than the reference voltage (2) R11, it is determined that the lighting device is operating normally. On the other hand, if, for example, a load higher than the rated value is connected to the lighting device or other abnormal conditions occur, the switching transistor 3,
5 current increases. Furthermore, in this case, the temperature of the diode bridge 1 also rises because the power supply current supplied to each part of the circuit via the diode bridge 1 also increases.

Therefore, the moisture sensitive element r.21 is connected to the diode bridge 1, for example.
By thermally coupling the diode bridge 1 to the temperature sensing element 21, the resistance value R1 of the temperature sensing element 21 also increases as the temperature of the diode bridge 1 increases. As a result, the reference voltage vREF decreases, and in combination with the increase in the detection voltage V, the voltage of the detection voltage (2) rapidly becomes higher than the voltage of the reference voltage (1).

Therefore, the protection circuit 27 operates, for example, lowers the base voltage of the switching transistor 5 to cut off the transistor 5. This stops the output of the inverter circuit and protects the circuit.

Furthermore, as for the configuration of the protection circuit 27, for example, the detection voltage
It can be constituted by a comparison circuit that compares the reference voltage (1) and the reference voltage (1, 1), and a switching transistor that short-circuits the base of the I transistor 5 to the negative power supply line using the output of this comparison circuit.

Further, the resistance value R□ of the temperature sensing element 21 is, for example, as shown in FIG.
The selection may be made so that the magnitude relationship between and the detection voltage ■[ is changed to EF. In other words, the temperature of the diode bridge 1 and other heat generating components or the ambient temperature.
It is preferable to set the detection voltage V1 to be larger than the reference voltage RE when the temperature of the temperature sensing element 21 exceeds T1 by increasing the temperature by one.

FIG. 3 shows a schematic configuration of a lighting device according to another embodiment of the present invention. The device shown in FIG. 3 uses a reference voltage generation circuit having a resistor 37.39 and a time constant circuit 49 instead of the voltage dividing circuit made up of the temperature sensing element 21 and the resistor 23.25 in the device shown in FIG. It is something.

Other parts are the same as the apparatus of FIG. 1, and like parts are designated with like reference numerals. The time constant circuit 49 includes a diode 45, a capacitor 47, and a resistor 4 connected in series.
3, and a resistor 41 connected in parallel with a diode 45. Such a time constant circuit 49 is connected in parallel with the resistor 37.

In the lighting device shown in FIG. 3, when the alternating current power supply AC is applied, the switching transistor 3,
5 is alternately turned on and off to generate a high frequency voltage and drive the lamp load 19. And during steady operation, the resistance is 37.39
The reference voltage generated by the voltage divider circuit consisting of ■
By comparing the voltage across the emitter resistor 31EF with the voltage (2) across the emitter resistor 31EF, an abnormal state is detected and the circuit is protected in the same way as described above.

However, since the lighting device shown in FIG. 3 is provided with a time constant circuit 49, the reference voltage RE is raised above its normal value when the AC power source AC is turned on. That is, when the power is turned on, the voltage across the capacitor 47 is approximately equal to O, so the parallel circuit of the diode 45, the resistor 41, and the series circuit of the resistor 43 are connected in parallel with the resistor 37, and the reference voltage REF is constant. Higher than normal value. Thereafter, the capacitor 47 is gradually charged via the diode 45, etc., and after a predetermined time, the time constant circuit 4
The raising of the reference voltage (RE) by the operation in step 9 has no effect, and the reference voltage (RE) becomes the normal value. Therefore,
During a predetermined period of time after the power is turned on, the reference voltage REF is higher than its normal value, making it more difficult for the protection circuit 27 to operate than during normal operation. Therefore, malfunction of the protection circuit due to rush current at startup, for example, can be prevented, and the operational sensitivity of the protection circuit during steady state can be increased. Incidentally, a temperature sensing element can also be used in the voltage dividing circuit for generating the reference voltage in the apparatus shown in FIG. 3, as in the apparatus shown in FIG.

[Effects of the Invention] As described above, according to the present invention, it is possible to increase the operating sensitivity of the protection circuit and reliably protect the circuit without sacrificing stability during steady operation.

Furthermore, it is possible to accurately prevent malfunctions of the protection circuit due to inrush current or the like when the device is started up, while increasing the operating sensitivity of the protection circuit during normal operation, thereby reliably protecting the circuit from abnormal conditions.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the general configuration of a lighting device according to an embodiment of the present invention, FIG. 2 is a graph showing the characteristics of the temperature sensing element in the device of FIG. 1, and FIG. It is a block circuit schematically showing a lighting device according to another embodiment of the present invention. 1: diode bridge, 3.5 switch 1 to transistor, 7: drive circuit, 9: starting circuit, 11: ballast, 13.15: content, 17: output transformer,
19: Lamp load, 21: Temperature sensing element, 2325, 29.
31.37.39.41.43: Resistor, 27: Protection circuit, 33.35.45: Diode, 47::Rn capacitor, 49: Time constant circuit.

Claims (1)

[Claims] 1. Inverter means for generating a high-frequency power source for lamp lighting; current detection means for outputting a signal corresponding to the current flowing through a switch element of the inverter means; a reference signal generating means for generating a reference signal by dividing a power supply voltage of the inverter; and a protection circuit means for stopping the output of the inverter means based on a comparison between the output signal of the current detecting means and the reference signal. A lighting device featuring: 2. Inverter means for generating a high-frequency power source for lamp lighting; current detecting means for outputting a signal corresponding to the current flowing through the switch element of the inverter means; and for comparing the output signal of the current detecting means with a predetermined reference signal. A lighting device comprising: protection circuit means for stopping the output of the inverter means based on the power source; and timer means for stopping the operation of the protection circuit means for a predetermined period of time after power is turned on.