JP3694146B2 - Discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device for lighting a discharge lamp at a high frequency by an inverter circuit.
[0002]
[Prior art]
FIG. 4 is a circuit diagram of a conventional discharge lamp lighting device, for example. In the figure, 1 is a commercial AC power source, 2 is a rectifier circuit, 3 is a booster circuit composed of a resonance inductor 4 and a resonance capacitor 5, 6 is a smoothing capacitor, 7 is an inverter, and 8 is a control circuit for controlling the inverter 7. , 9 is a DC cut capacitor, 10 is a ballast coil, 11 is a discharge lamp, 12 is a discharge lamp end of life detection means, and 13 is a comparison circuit.
[0003]
Next, the operation will be described.
First, the operation until the discharge lamp 11 is turned on will be described.
The AC power supplied from the commercial AC power 1 is full-wave rectified by the rectifier circuit 2. Thereafter, the voltage is boosted by the resonant action of the resonant inductor 4 and the resonant capacitor 5 in the booster circuit 3, smoothed by the smoothing capacitor 6, and used as the input power source of the inverter 7.
[0004]
The inverter 7 is driven by the control circuit 8 and outputs a high-frequency current when the switching element in the inverter 7 is turned on / off. This high-frequency current is supplied to the discharge lamp 11 via the DC cut capacitor 9 and the ballast coil 10 to light the discharge lamp 11. Here, the ballast coil 10 has a function of an inductor that limits a current flowing to the discharge lamp 11.
[0005]
Next, drive control of the inverter 7 that accompanies detection of the normal state or the end of life state of the discharge lamp 11 will be described.
The discharge lamp end-of-life detection means 12 uses the characteristic that the voltage across the discharge lamp increases when the discharge lamp 11 reaches the end of life, detects the voltage increase, and inputs it to the comparison circuit 13. The comparison circuit 13 compares the output value of the discharge lamp end of life detection means 12 with a predetermined threshold value, and outputs the comparison result to the control circuit 8. Therefore, the threshold value of the comparison circuit 13 is V0, the output value of the discharge lamp end of life detection means 12 is V1 when the discharge lamp 11 is normal, and V2 when the discharge lamp 11 is at the end of life, and the relationship between the values is V1. <V0 <V2.
[0006]
As a result, the output of the comparison circuit 13 is at a high level when the discharge lamp 11 is normal, and is at a low level when the discharge lamp 11 is at the end of its life. The control circuit 8 controls the inverter 7 by the output of the comparison circuit 13. That is, the control circuit 8 continues to drive the inverter 7 if the output from the comparison circuit 13 is high level, and stops driving when the output is low level. Therefore, when the discharge lamp 11 reaches the end of its life, the inverter 7 stops driving.
[0007]
[Problems to be solved by the invention]
In the conventional discharge lamp lighting device as described above, when the discharge lamp 11 is at the end of its life, this end of life can be detected and the drive of the inverter 7 can be stopped to cope with it, but when the smoothing capacitor 6 becomes overvoltage due to some kind of trouble. However, there is no means for detecting this, and in particular, in the step-up circuit configuration as shown in FIG. 4, the smoothing capacitor 6 deteriorates due to this overvoltage, or the switching element constituting the inverter 7 breaks down. There was a point.
[0008]
The present invention has been made in order to solve the above-described problems. Even when the discharge lamp reaches the end of its life or when the smoothing capacitor becomes overvoltage, the discharge lamp lighting device can cope with a simple circuit configuration. Is what you get.
[0009]
[Means for Solving the Problems]
A discharge lamp lighting device according to the present invention includes a rectifying circuit for full-wave rectification of a commercial power source, a smoothing capacitor for smoothing the output of the rectifying circuit, an inverter for converting an input power source from the smoothing capacitor to a high-frequency power source, A control circuit for controlling the drive of the inverter, a discharge lamp supplied with high-frequency power from the inverter, an end of life detection means for detecting the end of life of the discharge lamp, and an end of life detection by the end of life detection means A first comparison circuit that outputs a signal according to the presence / absence, a voltage dividing circuit having a variable voltage dividing ratio that divides the voltage of the smoothing capacitor, a switching element that changes the voltage dividing ratio of the voltage dividing circuit, and ON / OFF of the switching element. A second comparison circuit that outputs a signal corresponding to the presence or absence of an OFF state and an overvoltage state of the smoothing capacitor, and the second comparison circuit and the output unit of the first comparison circuit Constitute an AND circuit connected to the output section of the road, by inputting the output from the connection portion to the control circuit and the switching element, when a or the smoothing capacitor when the discharge lamp is turned end of life has become overvoltage, Until the commercial power source is turned on again, the switching element is kept in the OFF state and the drive of the inverter is stopped.
[0011]
Furthermore, a discharge lamp mounting detection means for detecting the mounting of the discharge lamp, and a third comparison circuit for outputting a signal corresponding to the presence or absence of mounting detection by the discharge lamp mounting detection means, The output is input to the second comparison circuit and the control circuit, the discharge lamp is removed, the switching element is turned on, and the discharge stop is attached to release the drive stop of the inverter.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a circuit diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention. In the figure, the same reference numerals are given to the same or corresponding parts as in the conventional example, and the description is omitted. Reference numeral 14 denotes a voltage dividing circuit for detecting an overvoltage of the smoothing capacitor 6, 15, 16 and 17 are resistors, 18 is a switching element made of, for example, a transistor, and 19 is a comparison circuit.
The comparison circuit 13 and the comparison circuit 19 indicate a first comparison circuit and a second comparison circuit, respectively.
[0013]
The voltage dividing circuit 14 divides the voltage of the smoothing capacitor 6 by the resistor 15, the resistor 16 and the resistor 17 when the switching element 18 is ON, and the resistor 15 and the resistor 16 of the smoothing capacitor 6 when the switching element 18 is OFF. The voltage is divided, and the divided value is input to the comparison circuit 19.
[0014]
Further, in the voltage dividing circuit 14 and the comparison circuit 19, the threshold value of the comparison circuit 19 is set to V10, the voltage of the smoothing capacitor 6 is normal, and the voltage dividing circuit 14 is in the ON state. The voltage dividing value is V11, the voltage dividing value of the voltage dividing circuit 14 when the smoothing capacitor 6 is overvoltage is V12, the voltage of the smoothing capacitor 6 is normal, and the voltage dividing circuit 14 when the switching element 18 is OFF. When the divided voltage value is V13, the resistor 15, the resistor 16, the resistor 17, and the threshold value V10 are set so that the relationship between the values is V11 <V10 <V12 and V13.
[0015]
Therefore, when the voltage of the smoothing capacitor 6 is normal, the output value of the comparison circuit 19 becomes high level. When the smoothing capacitor 6 becomes overvoltage, the output value becomes low level, the voltage of the smoothing capacitor 6 is normal, and the switching element 18. When is OFF, the output value is at a low level.
[0016]
Further, the output portions of the comparison circuit 13 and the comparison circuit 19 are connected, and the output from the connection portion is input to the control circuit 8 and the base of the switching element 18. The comparison circuit 13 and the comparison circuit 19 constitute an AND circuit by connecting the output parts of both. That is, when both the outputs of the comparison circuit 13 and the comparison circuit 19 are at a high level, a high-level output value is input to the control circuit 8 and the switching element 18 is turned on.
[0017]
Next, the operation will be described.
First, the case where the discharge lamp 11 is normal and the voltage of the smoothing capacitor 6 is normal will be described.
Since the output value of the comparison circuit 13 becomes high level as in the conventional example and the output value of the comparison circuit 19 becomes high level by the above setting, the control circuit 8 drives the inverter by inputting the high level output value. And the switching element 18 maintains the ON state when a high-level output value is input to the base. As a result, the discharge lamp 11 continues to be lit.
[0018]
Next, the case where the smoothing capacitor 6 becomes overvoltage will be described.
The output value of the comparison circuit 19 becomes a low level from the above setting. Here, the control circuit 8 continues the operation if both the outputs of the comparison circuit 13 and the comparison circuit 19 are at the high level, and stops the operation of the inverter 7 if at least one of both is at the low level. In that case, the control circuit 8 stops the operation of the inverter 7.
[0019]
Further, in the voltage dividing circuit 14, if both the outputs of the comparison circuit 13 and the comparison circuit 19 are high level, the switching element 18 is maintained in the ON state, and if at least one of both is low level, the switching element 18 is OFF. Therefore, when the smoothing capacitor 6 is overvoltage, the switching element 18 is turned off in the voltage dividing circuit 14.
[0020]
Next, a case where the discharge lamp 11 reaches the end of its life will be described.
Since the output value of the comparison circuit 13 is at the low level as in the conventional example, the control circuit 8 stops the operation of the inverter 7.
[0021]
Therefore, the voltage dividing circuit 14, the comparison circuit 13, and the comparison circuit 19 constitute a latch circuit, and once the switching element 18 is turned off, the OFF state is continued until the commercial AC power supply 1 is turned off. If the switching element 18 is OFF, the input to the control circuit 8 is also maintained at a low level, and the stopped state of the inverter 7 is maintained.
[0022]
Therefore, when the discharge lamp 11 reaches the end of its life or when the smoothing capacitor 6 becomes overvoltage, the switching element 18 is kept off and the inverter 7 is stopped until the commercial AC power supply 1 is turned on again. Accordingly, it is possible to prevent the smoothing capacitor 6 from being deteriorated or the switching element constituting the inverter 7 from being broken.
[0023]
Embodiment 2. FIG.
FIG. 2 is a circuit diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention. In the figure, the same or corresponding parts as those in the first embodiment and the conventional example are denoted by the same reference numerals, and description thereof is omitted. In the figure, 20 is a discharge lamp mounting detection means, 21 is a comparison circuit, and 22 is a resistance. The output result of the discharge lamp mounting detection means 20 is input to the comparison circuit 21, and the output section of the comparison circuit 21 is a resistance 22. Is connected to the output side of the voltage dividing circuit 14 and input to the comparison circuit 19.
The comparison circuit 21 is a third comparison circuit according to claim 2.
[0024]
In this circuit configuration, the voltage dividing ratio of the voltage dividing circuit 14 is changed by the low level output of the comparison circuit 21 and the resistor 22, and the resistor 22 has a resistance value equivalent to that of the resistor 17. Further, when the discharge lamp mounting detection means 20 detects that the discharge lamp 11 is normally mounted, the output value of the comparison circuit 21 becomes high level, and when it detects that the discharge lamp 11 is not mounted, it becomes low level. As described above, the output value of the discharge lamp mounting detection means 20 and the threshold value in the comparison circuit 21 are set.
[0025]
Next, the operation will be described.
Since the operation when the discharge lamp 11 is normally lit is the same as that of the first embodiment, the description thereof is omitted.
As for the operation when the discharge lamp 11 reaches the end of its life or when the smoothing capacitor 6 becomes overvoltage, the stop state of the inverter 7 is latched as in the first embodiment.
[0026]
Here, the case where the discharge lamp 11 is removed when the stop state of the inverter 7 is latched will be described.
The output of the comparison circuit 21 becomes low level by the above setting, the voltage dividing ratio is determined by the resistors 15, 16 and 22, and the output of the comparison circuit 19 becomes high level. Further, the output of the comparison circuit 13 becomes high level. Therefore, upon receiving the high level output of the comparison circuit 13 and the comparison circuit 19, the switching element 18 is turned on, and the control circuit 8 resumes driving of the inverter 7.
[0027]
Therefore, when the discharge lamp 11 is at the end of its life or the smoothing capacitor 6 is overvoltaged, the switching element 18 is kept in the OFF state and the inverter 7 is stopped. Then, the switching element 18 can be turned on to drive the inverter 7.
Even when the commercial AC power supply 1 is turned off, the latch can be released, the switching element 18 can be turned on, and the inverter 7 can be driven.
[0028]
Embodiment 3 FIG.
FIG. 3 is a circuit diagram of a discharge lamp lighting device according to Embodiment 3 of the present invention. In the figure, the same or corresponding parts as those in the first and second embodiments and the conventional example are denoted by the same reference numerals, and description thereof is omitted. In the figure, a path for directly inputting the output of the comparison circuit 21 to the control circuit 8 is provided. Thus, the control circuit 8 starts the operation of the inverter 7 when the outputs of the comparison circuits 13, 19 and 21 all become high level.
The comparison circuit 21 is a third comparison circuit according to claim 3.
[0029]
Next, the operation will be described.
Since the operation when the discharge lamp 11 is normally lit is the same as that of the first embodiment, the description thereof is omitted.
As for the operation when the discharge lamp 11 reaches the end of its life or when the smoothing capacitor 6 becomes overvoltage, the stop state of the inverter 7 is latched as in the first embodiment.
[0030]
Here, the case where the discharge lamp 11 is removed when the stop state of the inverter 7 is latched will be described.
The comparison circuit 13 and the comparison circuit 19 become high level, and the latch of the switching element 18 is released. However, since the discharge lamp 11 is not attached, the output of the comparison circuit 21 is at a low level, and the inverter 7 remains stopped. Thereafter, when the discharge lamp 11 is newly mounted, the comparison circuit 21 becomes high level, and the control circuit 8 restarts the operation of the inverter 7.
[0031]
Therefore, when the discharge lamp 11 reaches the end of its life or the smoothing capacitor 6 becomes overvoltage, when the switching element 18 is kept in the OFF state and the inverter 7 is stopped, the switching lamp 18 is removed to remove the switching element 18. Is turned on, and the discharge lamp 11 is newly mounted, whereby the inverter 7 can be driven.
[0032]
The resistance value of the resistor 22 is preferably equal to the resistance value of the resistor 17 for convenience of design, but other values may be set as long as the above operation is satisfied.
[0033]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0034]
The output part of the first comparison circuit and the output part of the second comparison circuit are connected to form an AND circuit, and the output from this connection part is input to the control circuit and the switching element, so that the discharge lamp is at the end of its life. If the discharge lamp becomes overdue or the smoothing capacitor becomes overvoltage , the switching element is kept off until the commercial power supply is turned on again to stop the drive of the inverter. Even when the voltage becomes an overvoltage, a discharge lamp lighting device having a simple circuit configuration that can bring the switching element and the inverter into a latched state can be obtained.
[0036]
Furthermore, a discharge lamp mounting detection means for detecting the mounting of the discharge lamp, and a third comparison circuit for outputting a signal corresponding to the presence or absence of mounting detection by the discharge lamp mounting detection means, Since the output is input to the second comparison circuit and the control circuit, the discharge lamp is removed, the switching element is turned on, and the drive stop of the inverter is released by attaching the discharge lamp. A discharge lamp lighting device having a simple circuit configuration that can release the latched state of the inverter can be obtained by replacing the discharge lamp even when the end stage is reached or the smoothing capacitor is overvoltaged.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a discharge lamp lighting device showing Embodiment 1 of the present invention.
FIG. 2 is a circuit diagram of a discharge lamp lighting device showing Embodiment 2 of the present invention.
FIG. 3 is a circuit diagram of a discharge lamp lighting device showing Embodiment 3 of the present invention.
FIG. 4 is a circuit diagram of a conventional discharge lamp lighting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Commercial AC power supply, 2 Rectifier circuit, 6 Smoothing capacitor, 7 Inverter, 8 Control circuit, 11 Discharge lamp, 12 Discharge lamp end of life detection means, 13 Comparison circuit, 14 Voltage dividing circuit, 18 Switching element, 19 Comparison circuit, 20 21. discharge lamp wearing detection means, 21 comparison circuit.

Claims (2)

A rectifier circuit for full-wave rectification of commercial power;
A smoothing capacitor for smoothing the output of the rectifier circuit;
An inverter that converts the input power from the smoothing capacitor to a high-frequency power source;
A control circuit for controlling the drive of the inverter;
A discharge lamp supplied with high-frequency power from the inverter;
Means for detecting the end of life of this discharge lamp,
A first comparison circuit that outputs a signal corresponding to the presence or absence of the end of life detection by the end of life detection means;
A voltage dividing circuit having a variable voltage dividing ratio for dividing the voltage of the smoothing capacitor;
A switching element that changes the voltage dividing ratio of the voltage dividing circuit;
A second comparison circuit that outputs a signal corresponding to the ON / OFF state of the switching element and the presence or absence of an overvoltage state of the smoothing capacitor;
With
An AND circuit is configured by connecting the output section of the first comparison circuit and the output section of the second comparison circuit, and the output from this connection section is input to the control circuit and the switching element, and the release is performed. When the lamp reaches the end of its life or when the smoothing capacitor becomes overvoltage, the switching element is kept in the OFF state until the commercial power supply is turned on again , and the drive of the inverter is stopped. Electric light lighting device. Discharge lamp mounting detection means for detecting mounting of the discharge lamp;
A third comparison circuit for outputting a signal corresponding to whether or not the discharge lamp mounting detection means detects mounting;
With
The output of the third comparison circuit is input to the second comparison circuit and the control circuit, the discharge lamp is removed, the switching element is turned on, and the discharge lamp is attached to the inverter. The discharge lamp lighting device according to claim 1, wherein the drive stop is released.

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