JP5019694B2 - Discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device that lights a lamp with high-frequency power from an inverter, and more particularly to a discharge lamp lighting device that includes a protection circuit that detects an abnormal discharge at the end of the lamp life and protects the inverter.
[0002]
[Prior art]
FIG. 7 is a circuit diagram showing an outline of a conventional discharge lamp lighting device. The discharge lamp lighting device shown in this figure is a half-bridge type inverter, and switching elements Q1 and Q2 connected in series to a DC power source E, and an inductor L1 connected in series to a lamp 1 connected in parallel to the switching element Q2. And capacitors C1 and C2, an oscillation circuit 2 for alternately switching on and off the switching elements Q1 and Q2 with a high-frequency signal, and a protection circuit 3 for protecting the apparatus from abnormal discharge at the end of the life of the lamp 1. Yes.
The protection circuit 3 includes a voltage detection circuit 4, an abnormal voltage detection circuit 5 that turns off the output when the voltage value detected by the voltage detection circuit 4 is equal to or greater than a predetermined value, and the output of the abnormal voltage detection circuit 5. And an oscillation stop circuit 6 for stopping the operation of the oscillation circuit 2 at the time.
[0003]
The voltage detection circuit 4 described above detects the sum of the lamp voltage and the charging voltage of the capacitor C2 (coupling capacitor) by the capacitors C3 and C4, and the voltage divided by the capacitors C3 and C4 is detected by peak-peak. The diodes D1 and D2 and the voltages V1 and V2 (V1: voltage when the lamp is normally lit, V2: voltage when the lamp is abnormally lit) detected by the diodes D1 and D2 are halved, for example. Voltage dividing resistors R1 and R2, and a smoothing capacitor C5 that smoothes the divided voltages V11 and V21. The smoothing capacitor C5 has a capacity that is fully charged with a delay determined by a time constant with the resistor R1 so that the abnormal voltage detection circuit 5 does not malfunction due to a high voltage at the time of starting the lamp.
[0004]
The abnormal voltage detection circuit 5 includes a Zener diode (not shown) that is turned on when a voltage equal to or higher than the Zener voltage (predetermined value), that is, the voltage V21 when the lamp is abnormally lit, and the Zener diode 5a operates. And a transistor (not shown) that turns on and turns off the output.
[0005]
Next, the operation of the protection circuit of the conventional discharge lamp lighting device will be described.
The capacitors C3 and C4 of the voltage detection circuit 4 divide the high-frequency voltage (the sum of the lamp voltage and the charging voltage of the capacitor C2) applied to the lamp 1 side by alternately turning on and off the switching elements Q1 and Q2, The divided voltages are detected by the diodes D1 and D2 using a peak-peak, and full-wave rectification is generated. Then, the full-wave rectified voltages V1 and V2 are divided by approximately ½ times (V11 and V21) by the voltage dividing resistors R1 and R2, and the smoothing capacitor C5 smoothes the voltages V11 and V21. Applied to the Zener diode of the voltage detection circuit 5.
[0006]
The Zener diode of the abnormal voltage detection circuit 5 does not conduct when the DC voltage smoothed by the smoothing capacitor C5 does not reach the Zener voltage, but turns on a transistor (not shown) when the DC voltage is equal to or higher than the Zener voltage. To shut off the output. At this time, the oscillation stop circuit 6 stops the oscillation operation of the oscillation circuit 2 and stops the on / off operation of the switching elements Q1, Q2.
[0007]
[Problems to be solved by the invention]
In the protection circuit for the conventional discharge lamp lighting device described above, the voltages V1 and V2 detected by the peak-peak by the capacitors C3 and C4 and the diodes D1 and D2 are divided by the resistors R1 and R2 so as to be almost halved. Further, as shown in FIG. 8, the peak voltage V1 when the lamp is normally lit is the voltage V11 (both ends of the resistor R2), and the peak voltage V2 when the lamp is abnormally lit is the voltage V21, and the voltage level difference between the voltages V11 and V21. V3 was also reduced by the same ratio. For this reason, when an error (variation voltage) has occurred in the Zener voltage of the Zener diode of the abnormal voltage detection circuit 5, the Zener diode 5a conducts at the voltage V11 when the lamp is normally lit, and the oscillation circuit 2 is stopped. In addition, there is a problem that the Zener voltage of the Zener diode 5a does not reach the Zener voltage even when the voltage V21 is abnormally lit.
[0008]
The present invention has been made to solve the above-described problems. Even if there is an error in the Zener voltage of the Zener diode of the abnormal voltage detection circuit, the present invention operates when the lamp is normally lit or when the lamp is lit abnormally. It is an object of the present invention to provide a discharge lamp lighting device that has never existed.
[0009]
[Means for Solving the Problems]
The discharge lamp lighting device according to the present invention includes an inverter for applying a voltage to the discharge lamp side based on the oscillation frequency of the oscillation circuit, a voltage applied to the discharge lamp side being cut by a first predetermined value, and the remaining voltage has a Zener diode for outputting is a first predetermined value partial cut the potential difference between the voltage and the abnormal lighting when voltage of the discharge lamp in the normal lighting mode of the discharge lamp output from the Zener diode at the Zener diode A voltage detection circuit that generates a voltage value that is kept substantially equal to the previous potential difference; and an abnormal voltage detection circuit that detects an abnormality in the discharge lamp when the voltage value generated by the voltage detection circuit is equal to or greater than a second predetermined value. It is a thing.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, some embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent part as the prior art example demonstrated in FIG. 7, and description is abbreviate | omitted.
Embodiment 1 FIG.
The discharge lamp lighting device shown in FIG. 1 is a half-bridge inverter, and is connected to a protection circuit 3 in series with voltage dividing resistors R11 and R12 having a predetermined voltage dividing ratio and these voltage dividing resistors R11 and R12. For example, a voltage detection circuit 4 having a Zener diode DZ is provided. The Zener diode DZ has a Zener voltage VZ, and is converted by the capacitors C3 and C4 and the diodes D1 and D2. The full-wave rectified voltages V1 and V2 (V1: voltage when the lamp is normally lit, V2: when the lamp is lit abnormally) This is because the zener voltage VZ is cut. This is because the voltage level difference V4 between the voltage V12 when the lamp is normally lit and the voltage V22 when the lamp is abnormally lit is generated at both ends of the resistor R12 by adjusting the resistance values of the voltage dividing resistors R11 and R12. (See FIG. 2). As the Zener voltage VZ of the Zener diode DZ increases, the voltage level difference between the voltage V12 when the lamp is normally lit and the voltage V22 when the lamp is abnormally lit can be increased.
[0011]
In the first embodiment, for example, the voltage V12 detected when the lamp is normally lit becomes substantially the same voltage level (V11) as before, and the voltage V22 detected when the lamp is abnormally lit is supplied to the abnormal voltage detection circuit 5. The value of the Zener voltage VZ of the Zener diode DZ and the resistance values of the voltage dividing resistors R11 and R12 are adjusted so as to be equal to or higher than the variation voltage of the Zener voltage of the Zener diode (not shown) provided. When the voltage V12 detected when the lamp is normally lit is set to a voltage level almost the same as the conventional voltage level, the voltage dividing ratio of the voltage dividing resistors R11 and R12 is higher than the voltage dividing ratio of the conventional voltage dividing resistors R1 and R2 described in FIG. It is getting bigger.
[0012]
In the discharge lamp lighting device configured as described above, the high-frequency voltage when the lamp is normally lit is divided by the capacitors C3 and C4 and converted to the full-wave rectified voltage V1 by the diodes D1 and D2. The voltage V1 is cut by the Zener diode DZ by the Zener voltage VZ as shown in the following equation (1), and the remaining voltage V1 is divided by the voltage dividing resistors R11 and R12 to become the voltage V12.
V12 = (V1-VZ) × R12 / (R11 + R12) (1)
[0013]
Then, the divided voltage V12 is smoothed by the smoothing capacitor C5 and applied to the Zener diode of the abnormal voltage detection circuit 5. In this case, since the smoothed voltage V12 is lower than the Zener voltage of the Zener diode, the output of the abnormal voltage detection circuit 5 is held, and the on / off control of the switching elements Q1, Q2 by the oscillation circuit 2 is continued. .
[0014]
Further, the high-frequency voltage when the lamp is abnormally lit is divided by the capacitors C3 and C4 in the same manner as described above, and is converted to the full-wave rectified voltage V2 by the diodes D1 and D2. This voltage V2 is cut by the Zener diode DZ by the Zener voltage VZ as shown in the following equation (2), and the remaining voltage V2 is divided by the voltage dividing resistors R11 and R12 to become the voltage V22.
V22 = (V2−VZ) × R12 / (R11 + R12) (2)
[0015]
The divided voltage V22 is smoothed by the smoothing capacitor C5 and applied to the Zener diode of the abnormal voltage detection circuit 5. In this case, since the smoothed voltage V22 becomes equal to or higher than the variation voltage of the Zener voltage of the Zener diode, the transistor (not shown) of the abnormal voltage detection circuit 5 is turned on to cut off the output. At this time, the oscillation stop circuit 6 stops the oscillation operation of the oscillation circuit 2 and stops the on / off operation of the switching elements Q1, Q2.
[0016]
As described above, according to the first embodiment, the voltages V1, V2 detected by the capacitors C3, C4 and the diodes D1, D2 are cut by the Zener diode DZ by the Zener voltage VZ, and the remaining voltage is divided by the voltage dividing resistor R11, Since the voltage is divided by R12, it is possible to increase the voltage level difference V4 between the voltage V12 detected when the lamp is normally lit and the voltage V22 detected when the lamp is abnormally lit. The malfunction of the circuit 3 or the fact that the protection circuit 3 did not operate when the lamp is abnormally lit is eliminated, and since the protection is reliable, the circuit failure and the lamp socket can be prevented from being damaged. Further, since only the Zener diode DZ is inserted, there is an effect that it is possible to solve the problem with an inexpensive and simple circuit configuration.
[0017]
In the first embodiment, the voltage V12 detected when the lamp is normally lit becomes substantially the same voltage level (V11) as before, and the voltage V22 detected when the lamp is abnormally lit is the abnormal voltage detection circuit 5. It has been described that the value of the Zener voltage VZ of the Zener diode DZ and the resistance values of the voltage dividing resistors R11 and R12 are adjusted so as to be equal to or higher than the variation voltage of the Zener voltage of the Zener diode provided in FIG. The value of the Zener voltage VZ of the Zener diode DZ and the resistance values of the voltage dividing resistors R11 and R12 may be adjusted so that the voltage V22 detected at the time of lighting becomes substantially the same voltage level (V21) as before. . In this case, the voltage dividing ratio of the voltage dividing resistors R11 and R12 is smaller than that in the first embodiment.
[0018]
Embodiment 2. FIG.
In the first embodiment described above, the high-frequency voltage applied to the lamp 1 side is converted into the voltages V1 and V2 by the capacitors C3 and C4 and the diodes D1 and D2, but this second embodiment is shown in FIG. As shown, instead of the capacitors C3 and C4, voltage dividing resistors R13 and R14 are used, and the voltages V1 and V2 divided by the voltage dividing resistors R13 and R14 are half-wave rectified by a diode D2. is there. The operation and effect in the second embodiment are the same as those in the first embodiment.
[0019]
Embodiment 3 FIG.
In the third embodiment, as shown in FIG. 4, Zener diodes DZ1 and DZ2 are inserted between capacitors C3 and C4 that divide the high-frequency voltage applied to the lamp 1 so that the anodes face each other. is there. The zener diodes DZ1 and DZ2 have, for example, the same zener voltage VZ as that of the zener diode DZ used in the first embodiment, and cut the zener voltage VZ by the voltage divided by the capacitors C3 and C4. .
[0020]
When the high-frequency voltage divided by the Zener diodes DZ1 and DZ2 when the lamp is normally lit as shown in FIG. 5A is cut by the Zener voltage VZ (shaded portion), a waveform as shown in FIG. 5C is obtained. As shown in FIG. 5B, when the high-frequency voltage divided when the lamp is abnormally lit is cut by the zener voltage VZ (shaded portion), a waveform as shown in FIG. 5D is obtained. As shown in (c) and (d), the voltage level difference V5 between the waveform when the lamp is normally lit and the waveform when the lamp is abnormally lit is larger than the voltage level difference V6 shown in FIGS. Yes.
[0021]
The waveform shown in (g) is obtained by dividing the waveform (e) when the lamp is normally lit by the capacitors C3 and C4, and the waveform shown in (h) is the waveform (f) when the lamp is abnormally lit. , Divided by C4.
[0022]
In the third embodiment, when the high-frequency voltage applied to the lamp 1 side is divided by the capacitors C3 and C4, the zener diodes DZ1 and DZ2 cut the zener voltage VZ. It is possible to increase the voltage level difference between the waveform and the waveform when the lamp is abnormally lit. For this reason, the protection circuit 3 malfunctions when the lamp is normally lit, or the protection circuit 3 does not operate when the lamp is abnormally lit. In addition, since the protection is reliable, circuit failure and lamp socket damage can be prevented.
[0023]
Embodiment 4 FIG.
In the third embodiment, it has been described that the two Zener diodes DZ1 and DZ2 are inserted between the capacitors C3 and C4 that divide the high-frequency voltage applied to the lamp 1 side. Uses a voltage dividing resistor R13, R14 in place of the capacitors C3, C4, and a Zener diode DZ1 for cutting a voltage in only one direction of the high-frequency voltage by the Zener voltage VZ is inserted between the voltage dividing resistors R13, R14. Is.
[0024]
In the fourth embodiment, the high frequency voltage applied to the lamp 1 side is divided by the voltage dividing resistors R13 and R14, and the divided one-way voltage is cut by the zener diode DZ1 by the zener voltage VZ. The remaining voltage is divided by the voltage dividing resistors R11 and R12, smoothed by the smoothing capacitor C5, and applied to the abnormal voltage detection circuit 5.
[0025]
As described above, since the Zener diode DZ1 is inserted between the voltage dividing resistors R13 and R14, the voltage level difference between the voltage when the lamp is normally lit and the voltage when the lamp is abnormally lit can be greatly increased. It is possible to prevent malfunction of the protection circuit 3 when the lamp is normally lit, and that the protection circuit 3 did not operate when the lamp is abnormally lit. Moreover, since the protection is reliable, circuit failure and damage to the lamp socket can be prevented.
[0026]
In each of the above-described embodiments, description has been made by applying to a half-bridge type inverter. However, a circuit for lighting the lamp 1 using the resonance of the inductor L1 and the capacitors C1 and C2, such as a one-stone resonance inverter, etc. You may apply to.
[0027]
【Effect of the invention】
As described above, according to the present invention, the voltage applied to the discharge lamp side by the inverter is input, the input voltage is cut by the first predetermined value by the Zener diode, and the remaining voltage is output. It generates a voltage value to keep substantially equal to the previous voltage difference being a potential difference the first predetermined value partial cut Zener diode of the normal lighting mode of the voltage of the output discharge lamp and abnormal lighting when voltage of the discharge lamp from, An abnormality of the discharge lamp is detected when the voltage value is equal to or greater than a second predetermined value. As a result, malfunctions during normal lighting of the discharge lamp and malfunctions during abnormal lighting of the discharge lamp are eliminated, and because the protection is reliable, failure of the inverter and damage to the socket of the discharge lamp can be prevented. .
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an outline of a discharge lamp lighting device according to Embodiment 1 of the present invention.
FIG. 2 is an explanatory diagram of a detection voltage when the lamp is normally lit and when the lamp is abnormally lit in the first embodiment.
FIG. 3 is a circuit diagram showing an outline of a discharge lamp lighting device according to a second embodiment.
4 is a circuit diagram showing an outline of a discharge lamp lighting device according to Embodiment 3. FIG.
FIG. 5 is an explanatory diagram of a detection voltage when the lamp is normally lit and when the lamp is abnormally lit in the third embodiment.
FIG. 6 is a circuit diagram showing an outline of a discharge lamp lighting device according to Embodiment 4;
FIG. 7 is a circuit diagram showing an outline of a conventional discharge lamp lighting device.
FIG. 8 is an explanatory diagram of detected voltages when a lamp is normally lit and when a lamp is abnormally lit in a conventional discharge lamp lighting device.
[Explanation of symbols]
1 lamp, 2 oscillation circuit, 3 protection circuit, 4 voltage detection circuit, 5 abnormal voltage detection circuit, 6 oscillation stop circuit, E DC power supply.

Claims (4)

An inverter that applies a voltage to the discharge lamp based on the oscillation frequency of the oscillation circuit;
The voltage applied to the discharge lamp side first cut predetermined value content has a Zener diode for outputting a remaining voltage, the normal lit the voltage of the discharge lamp output from the Zener diode and the discharge lamp abnormality A voltage detection circuit that generates a voltage value that keeps the potential difference from the voltage at the time of lighting substantially equal to the potential difference before being cut by the first predetermined value by the zener diode;
A discharge lamp lighting device comprising: an abnormal voltage detection circuit that detects an abnormality of the discharge lamp when the voltage value generated by the voltage detection circuit is equal to or greater than a second predetermined value.   The discharge lamp lighting device according to claim 1, wherein the voltage detection circuit includes a voltage conversion unit that divides an input voltage and converts the divided voltage into a DC voltage.   3. The discharge lamp lighting device according to claim 2, wherein the voltage detection circuit includes a voltage dividing unit that divides a voltage that remains after the DC voltage is cut by the Zener diode by a first predetermined value.   4. The discharge lamp lighting device according to claim 3, wherein the voltage dividing unit includes a resistor or a capacitor connected in series.

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