JPH09251899A - Electric discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate detection of wasteful lamp current due to performing feed back control for the full range of light adjustment signals, widen a dynamic range, and enhance detection precision of lamp current. SOLUTION: A current detection circuit 5 detects current which flows an electric discharge lamp 4 and outputs it as a lamp current signal A to a feed back control circuit 7. The feed back control circuit 7 takes the difference between the lamp current signal A and a light adjustment signal B and amplified it and outputs an amplified signal D to an adder 12. The adder 12 adds the amplified signal D and the light adjustment signal B, constitutes a control signal E, and feed backs it to a high-frequency power supply 2, however, if a comparator circuit 15 detects that the light adjustment degree against the full light of the light adjustment signal B is 40 to 60% or more, it is disconnected by means of a switch 13 provided between an error amplifier circuit 9 and the adder 12 to stop feed back control, the range in which feed back control is performed for the full light adjustment range of the light adjustment signal B is limited, the detection range of the lamp current signal is narrowed, a dynamic range is widened relatively, and the detection precision of the lamp current signal is enhanced.

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, and more particularly to a discharge lamp lighting device that performs feedback control for adjusting the brightness of a fluorescent lamp or the like.

[0002]

2. Description of the Related Art Although a light control device for adjusting the brightness of a discharge lamp or the like is known, in order to prevent flicker or moving stripes when the dimming degree is deep (dark) or when the air temperature is low, For example, a technique related to feedback control as disclosed in JP-A-6-302393 is known. FIG. 13 is a block diagram showing the outline of the technique of this known example.

In this example, from the high frequency power source 2 to the load circuit 3
The current detection circuit 5 detects the electric power supplied to the discharge lamp 4 and the lamp current signal A detected by the detection circuit 5 is detected.
And the dimming signal B input from the outside, the high frequency power supply 2
The feedback control circuit 7 produces a control signal E for controlling the. The feedback control circuit 7 subtracts the lamp current signal A and the dimming signal B, and the error signal C is amplified by the error amplification circuit 9. The amplified signal D and the dimming signal B are further added to form a control signal E. FIG. 14 shows the relationship between the dimming signal B and the lamp current signal A at room temperature.

In this example, when the value of the lamp current signal A is the same as that of the dimming signal B, the error signal C is 0 and the output of the error amplifier circuit 9 is also 0. Therefore, the dimming control signal E is used. The signal B is directly input to the high frequency power supply 2. When the lamp current signal A is smaller than the dimming signal B, the error signal C is generated, amplified by the error amplification circuit 9, and further added to the dimming signal B to form the control signal E.
It is input to the high frequency power supply 2. By performing feedback control according to the dimming signal B in this way, the lamp current signal A is increased and flicker or moving stripes of the discharge lamp 4 are prevented.

[0005]

In the discharge lamp lighting device of this type, since the feedback control circuit 7 for inputting the lamp current signal A normally operates with a low voltage power source, when the detected lamp current signal A is large. Therefore, it is necessary to increase the response capability of the feedback control circuit 7. However, in the above case, FIG.
As shown in FIG. 4, even if the lamp current signal A to be controlled is detected in the entire range of the dimming signal B and the dimming degree is shallow and the need for feedback control is poor, the feedback control is activated.

That is, most of the cases where the feedback control is necessary are the cases where the dimming is deep (dark), and this is referred to as the dimming signal B.
The detection range of the lamp current signal A with respect to the entire dimming range is about ⅓ to ⅕, and therefore, the feedback control is unnecessarily operated. Therefore, in the above example, the lamp current signal A for the entire dimming range of the dimming signal B is
By wastefully performing the detection of, the dynamic range of the actually required detection range is relatively squeezed, the detection accuracy is reduced by that amount, and noise resistance is deteriorated.

The present invention has been made in order to solve the above-mentioned problems, and in a device for performing feedback control to prevent extinction of a discharge lamp or the like, the dynamic range of the detection range that is actually necessary can be improved. An object of the present invention is to obtain a lighting device for a discharge lamp, which can be widened, can improve detection accuracy, and can improve noise resistance.

[0008]

To this end, in the invention according to claim 1, a load circuit including a discharge lamp, a high frequency power supply for supplying a high frequency power higher than a commercial power supply to the load circuit, and the discharge lamp are provided. A current detection circuit that detects a flowing lamp current and outputs a lamp current signal, a dimming unit that controls the high frequency power source and outputs a dimming signal for dimming the discharge lamp, and the lamp current signal And an error amplifier circuit that amplifies an error between the dimming signal and an adder that adds the signal amplified by the error amplifying circuit and the dimming signal as a control signal and outputs the control signal to the high-frequency power source, It is characterized in that when the dimming signal reaches a preset value, the signal amplified by the error amplification circuit is prevented from being input to the high frequency power source.

In the invention according to claim 2, the dimming degree of the dimming signal is approximately 40 to 100% or 60 to 1 with respect to the total light.
It is characterized in that a signal amplified by the error amplification circuit is prevented from being input to the high frequency power supply when the dimming degree is within the range of 00%.

According to another aspect of the invention, a plurality of load circuits and a plurality of current detection circuits are provided for the high frequency power source, and the lamp current signals output from the respective current detection circuits are compared and the smaller value side is subtracted. It is characterized by outputting to.

In the invention according to claim 4, a plurality of load circuits and current detection circuits are respectively provided in parallel with the high frequency power source, and each load circuit and current detection circuit are provided through a balancer transformer. And

In the invention according to claim 5, a temperature detecting circuit for detecting the ambient temperature is provided, and when the temperature detected by this temperature detecting circuit is below a certain value, the value of the lamp current signal is reduced to the subtractor. It is characterized by outputting.

According to another aspect of the invention, there is provided a sequence control circuit for at least performing a sequence of turning off and turning on the discharge lamp. When the sequence control circuit is in the turning off state of the discharge lamp, the control signal is a high frequency power source. It is characterized in that it is designed so as to be prevented from being input to.

In the invention according to claim 7, when the discharge lamp is in the extinguished state, the sequence control circuit replaces the sequence control signal corresponding to the extinguished state with the control signal and inputs it to the high frequency power supply. And

According to an eighth aspect of the invention, the error amplifier circuit sets the output to 0 when the dimming signal reaches a preset value.

According to a ninth aspect of the invention, the error amplifying circuit is a variable error amplifying circuit that increases the feedback control gain as the dimming degree of the dimming signal becomes deeper and decreases the feedback control gain as the dimming degree becomes shallower. .

According to a tenth aspect of the invention, there is provided a limiting circuit for preventing the magnitude of the feedback control gain of the error amplifying circuit from exceeding a certain level.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, each embodiment will be described with reference to the drawings, but configurations indicated by the same reference numerals indicate the same or corresponding configurations. Embodiment 1 FIG. 1 is a configuration diagram of a discharge lamp lighting device of this example, in which 1 is a commercial power source, 2 is a high frequency power source which is connected to the commercial power source and supplies high frequency power to a load circuit 3 including a discharge lamp 4. Yes, it is composed of a general VCO (voltage controlled oscillator), a switching element, and the like. Reference numeral 5 denotes a current detection circuit for detecting a lamp current flowing through the discharge lamp 4, and A denotes a lamp current signal detected and output by the current detection circuit 5.

Reference numeral 7 denotes a feedback control circuit, which is a known subtractor 8
And an error amplifier circuit 9. The subtractor 8 takes the difference between the lamp current signal A and the dimming signal B and outputs the error signal C to the error amplification circuit 9. The dimming signal B is output as a predetermined voltage from the dimming unit 11 provided with the light intensity varying means such as a known adjustment dial for adjusting the dimming intensity. Error amplifier circuit 9
Is constituted by an operational amplifier or the like, receives the error signal C, amplifies it, and outputs it to the adder 12. Reference numeral 13 denotes a switch provided between the feedback control circuit 7 and the high frequency power supply 2 for connecting / disconnecting, and provided between the adder 12 and the error amplification circuit 9. The connection / disconnection of the switch 13 is performed by a comparison circuit 15 such as a comparator that compares the values of the dimming signal B and the operation switching dimming degree signal F output from the reference signal generating unit 14.

The operation switching dimming degree signal F output to the comparison circuit 15 is a signal serving as a reference value for determining at which dimming degree the feedback control is started and stopped.
The comparator 15 is operated by determining whether the value of this signal is larger or smaller than the dimming signal B. FIG. 2 of this example shows a case where the feedback control is started when the dimming degree of the discharge lamp 4 is in the range of 0% (when adjusted to the darkest) to 50% (medium brightness), The intersection of L1 indicating the dimming signal B and L2 indicating the operation switching dimming degree signal F is set to be located at 50% of the dimming degree.

The value of the operation switching dimming degree signal F is preferably set within a range of approximately 40 to 60% with respect to the dimming degree of the dimming signal B. The upper side of FIG. 3 shows the operation / non-operation of the feedback control with respect to the dimming signal B, and the lower side is a diagram for explaining the characteristics relating to the dimming control. As shown in the figure, when the dimming degree is about 40% or less, problems such as discharge lamps disappearing or blinking easily occur at low temperature, and when the dimming degree is about 60% or less, it occurs when the discharge lamp lighting device is commercialized. It is understood that there may be individual differences (for example, variations in components) and that the need for feedback control is low when the dimming degree is approximately 50%. Therefore, the feedback control is stopped when the dimming degree is between approximately 40 to 60% for the reasons that it is preferable that the range in which unnecessary feedback control is omitted is wider and that the discharge lamp flicker is sufficiently dealt with. Is most effective.

According to this example, when the dimming signal 11 reaches a preset value (in the case of this example, the dimming degree for all lights is 50% or more), the switch 13 is disconnected. Since the feedback control is stopped by the current detection circuit 5, the lamp current signal A may be detected from the current detection circuit 5 only within a limited range (0 to 50% of the dimming degree). Therefore, the lamp current unnecessary for the feedback control is detected. Since it is not necessary to detect even the signal A and the detection range is narrowed, the dynamic range can be relatively widened to improve the detection accuracy of the lamp current signal, and the noise resistance can also be improved.

Further, the dimming signal B is about 40 for all lights.
By stopping the feedback control when it is -60% or more, it is possible to prevent the discharge lamp from flicker when the dimming is deep (dark) at low temperature, and to deal with the influence of individual differences of the discharge lamp lighting device. The detection range width of the lamp current signal A can be narrowed to relatively widen the dynamic range, and the detection accuracy of the lamp current signal can be improved.

Embodiment 2 In this example, an embodiment in which the discharge lamp 4 is provided in parallel with the high frequency power supply 2 in Embodiment 1 will be described. FIG. 4 is a configuration diagram showing this example, in which the load circuit 3-discharge lamp 4-current detection circuit 5 and load circuit 3a-discharge lamp 4a-current detection circuit 5a.
Are provided in parallel with the high frequency power supply 2 via the balancer transformer 30, and other configurations are similar to those of the first embodiment. The balancer transformer 30 is a two-winding transformer of the same turn having the same magnetic path. When the same current flows in each winding, magnetic flux is not generated and the balancer transformer itself does not operate, but it flows in each winding. When there is a difference in current, magnetic flux is generated according to the difference in current, and a voltage in one direction is generated in each winding. As a result, the currents flowing through the windings are made to be the same, and the currents from the high frequency power supply 2 are distributed equally to the load circuits 3 and 3a, so that the same currents flow in the series circuits.

A switching circuit 31 is provided between each of the current detection circuits 5 and 5a and the subtractor 8, and the switching circuit 31 connects the current detection circuit 5 and the subtractor 8 by the output of the comparator 32 (contact point). 33), the connection (contact 34) between the current detection circuit 5a and the subtractor 8 is selected and switched. The comparator 32 compares the lamp current signals A1 and A2 flowing through the current detection circuits 5 and 5a so that the lamp current signal with the smaller value is input to the subtractor 8. For example, when the lamp current signal A1 is smaller than the lamp current signal A2, a positive logic signal is output and the lamp current signal A1
Is larger than the lamp current signal A2, a negative logic signal is output, and when the comparison circuit 32 outputs a positive logic signal, the switching circuit 31 is connected to the current detection circuit 5 side (contact 3).
The lamp current signal A1 may be input to the subtractor 8 by switching to 3), and when the comparison circuit 32 outputs a negative logic signal, conversely, on the side of the current detection circuit 5a (contact 34).
Then, the lamp current signal A2 may be input to the subtractor 8.

According to the present embodiment, the comparator circuit 32 and the switching circuit 31 are connected to the side having a smaller lamp current signal, and the side which is most likely to be extinguished or flicker is selected and output to the feedback control circuit 7. The control reference is based on the side that is more likely to be extinguished, and the most effective extinction prevention and flicker prevention for two or more discharge lamps are possible.

Further, since the discharge lamps 4 and 4a are provided in parallel with the high frequency power source 2 via the balancer transformer 30, not only can the brightness of each discharge lamp be made uniform,
Even when the feedback control is performed by detecting the current flowing through one discharge lamp, the brightness of each discharge lamp can be made substantially uniform. Particularly when the dimming degree is deep (dark), variations in brightness are likely to occur due to differences in individual discharge lamps, but this variation can be well prevented.

Embodiment 3 In this example, a light control device will be described in which a structure capable of responding to a change in conditions due to temperature is added to that of the first embodiment. FIG.
2 is a configuration diagram of a discharge lamp light control device of this example, which is different from FIG. 1 in that a lamp current signal is formed. That is, reference numeral 35 in the figure is a general temperature detection circuit, for example, the output is 0 when the ambient temperature (air temperature) is 10 ° C. or higher, and when it is lower than that, the negative temperature detection signal H is output to the second adder. An output is generated at 36 (FIG. 6). Second adder 3
Reference numeral 6 is provided between the current detection circuit 5 and the subtractor 8 so that the lamp current signal A output from the current detection circuit 5 and the temperature detection signal H are added and output to the subtractor 8. The subsequent configuration is the same as that of the first embodiment.

When the ambient temperature is 10 ° C. or lower, the temperature detection signal H output from the temperature detection circuit 35 is negative, and therefore is added by the second adder 36 and input to the feedback control circuit 7. The signal is the lamp current signal A that is actually detected.
It becomes a value smaller than. Since the same feedback control as that of the first embodiment is performed for a value smaller than this actual value, the control signal E compensated by this feedback control is compared with that based on the actually detected lamp current signal A. Grows. Therefore, when feedback control is performed at low temperatures, the discharge lamp 4
The decrease in the optical output can be compensated more largely, and by performing the greater compensation at the low temperature when the discharge lamp easily goes out or flickers, the optical output can be obtained at the same level as that at the normal temperature. However, the setting of the temperature at which the temperature detection circuit 35 outputs a negative value may be appropriately determined and is not limited to 10 ° C.
Further, the magnitude of the negative signal output by the temperature detection circuit 35 may be appropriately set in consideration of the power consumption of the discharge lamp and the like.

Fourth Embodiment The present example relates to the first embodiment which prevents malfunction of feedback control. FIG. 7 is a partial configuration showing the configuration between the high frequency power supply 2 and the second adder 12, and since the configuration other than this part is the same as that of FIG. 1, it is omitted.

In the figure, reference numeral 40 is a sequence control circuit for switching the preheating, starting, lighting and abnormality protection sequences of the discharge lamp 4. Sequence control circuit 4
0 outputs a positive logic signal as the sequence control signal I during the period when the discharge lamp 4 is lit, for example, during the preheating period when the discharge lamp 4 is off, the starting period, and the abnormal protection period, the preheating start abnormality. A negative logic signal is used as the protection signal J and the switching circuit 41
The switching circuit 41 switches between the contact 42 and the contact 43 by switching the logic signal. The switching circuit 41 is connected to the contact 43 when receiving a positive logic signal, and has a negative logic. When the signal is received, it is connected to the contact 42. This sequence is shown in FIG.

Therefore, when the sequence control circuit 40 lights the discharge lamp 4 and outputs the sequence control signal I to the switching circuit 41, the control signal E is output to the high frequency power source 2, but the filament preheating is performed. The sequence control circuit 40 connects the switching circuit 41 to the contact 42 when the discharge lamp 4 is not lit, such as during the period, the starting period, and the abnormality protection period, and the preheating start abnormality protection signal J is used as the control signal E. Will be output to. Therefore, when the discharge lamp 4 is not turned on, the control signal E for feedback control is not input, and a malfunction due to this is prevented.

When the discharge lamp 4 is off,
Since the lamp current signal A is not input to the feedback control circuit 7, the difference in value between the control signal E in the stable lighting state and the control signal E in the extinguished state becomes large, but in the extinguished state, the control signal E is replaced by preheating. Since the starting abnormality protection signal J is output to the high frequency power supply 2 as a sequence control signal corresponding to the off state, the high frequency power supply 2 is turned on in both the lighting and extinguishing states.
It is possible to substantially reduce the change in the value of the signal input to the discharge lamp and prevent the discharge lamp from suddenly emitting light during lighting.

Fifth Embodiment In the first embodiment, the switch 13 controls the operation / non-operation of the feedback control, but in this example, the operation / non-operation of the feedback control is controlled by another means. Explain what. FIG. 9 is a block diagram of the device according to the present example. In the figure, 16 is a variable error amplifier circuit in which the amplification degree of the error signal C is variable. For example, a transconductance amplifier (this element is New Japan Radio NJM1360 of the company
0/13700) and the like. The variable error amplification circuit 16 makes the amplification degree of the error signal C variable by detecting the voltage of the dimming signal B. The upper side of FIG. 10 is a diagram showing the time point and the degree of variability at which the variable error amplification circuit 16 starts the feedback control, and the lower side is a diagram for explaining the characteristics relating to the dimming control. In this example, as in the first embodiment, 50% of the dimming degree of the dimming signal B with respect to all the lights.
The feedback control is started at the time of, and the feedback control gain of the variable error amplification circuit 16 increases as the dimming degree of the dimming signal B is deeper (darker), and the dimming degree of the dimming signal B is shallower. It becomes smaller when it is (bright).

That is, the variable error amplifier circuit 16 gradually increases the feedback control gain according to the dimming signal B from the time when the feedback control is started, and when the dimming signal B becomes shallow (bright), it becomes the dimming signal B. Accordingly, the feedback control gain is gradually reduced. The variable error amplifier circuit 16 outputs the signal D obtained by amplifying the error signal C to the second adder 12,
When the subtraction result of the lamp current signal A and the dimming signal B subtracted by the subtractor 8 is 0, the amplified signal D also becomes 0, so that the control signal output from the adder 12 to the high frequency power supply 2 is It becomes the dimming signal B.

According to the present embodiment, the variable error amplifier circuit 16 operates and deactivates the feedback control according to the dimming signal B, and the feedback control is not performed at the dimming degree at which the feedback control is substantially unnecessary. The range of the lamp current to be made can be limited and narrowed, so that the dynamic range can be relatively widened to improve the detection accuracy of the lamp current, and the noise resistance can also be improved. Further, the variable error amplifier circuit 16
Since the feedback control gain is gradually amplified in accordance with the magnitude of the dimming signal B, it is possible to suppress a sharp change in the control signal E, and thus a sharp change in the optical output of the discharge lamp 4 or the like occurs. Can be prevented.

Further, since the variable error amplifier circuit 16 starts the feedback control when the dimming degree of the dimming signal B is in the range of approximately 40 to 60% of the total light, even if the dimming degree is deep at low temperature. It is possible to sufficiently prevent the discharge lamp and the like from extinguishing, and it is possible to sufficiently adapt to individual differences in the discharge lamp lighting device and the like. Further, it can be realized by a simpler configuration as compared with that of FIG.

Embodiment 6 FIG. FIG. 11 is a block diagram of the device of this example, and since the configuration other than the limiting circuit 17 is the same as that of the fifth embodiment, its explanation is omitted. The limiting circuit 17 controls the dimming signal B input to the variable error amplifier circuit 16 to prevent the discharge lamp 4 from oscillating due to excessive feedback control. 1 in the figure
Reference numeral 8 denotes a limit value generating circuit that outputs the limit signal G, and the limit signal G is a signal for preventing the feedback control gain of the variable error amplifier circuit 16 from exceeding a certain level. Reference numeral 19 is a comparator including a comparator, which compares the limiting signal G with the dimming signal B, and inverts the inverter 20 including an inverter according to the comparison result. The inverter 20 selectively connects either the switch 21 or the switch 22,
Either the dimming signal B or the limiting signal G is input to the variable error amplifier circuit 16 of the feedback control circuit 7.
Note that FIG. 11 shows a state in which the switch 21 side is connected by the inverter 20 and the limiting signal G is input to the variable error amplification circuit 16, and the switch 22 side is disconnected.

Therefore, when the value of the dimming signal B is smaller than the limiting signal G, the inverter 20 puts the switch 22 in the connected state and inputs the dimming signal B to the variable error amplifier circuit 16. When the value of B is larger than the limit signal G, the inverter 20 is inverted by the output of the comparator 19 to bring the switch 21 into the connected state, and the limit signal G is output to the variable error amplifier circuit 16 and at the same time, the switch 22. Is disconnected so that the dimming signal B is not output to the variable error amplifier circuit 16. In this case, the limit signal G may have a value that can prevent the feedback control gain of the variable error amplification circuit 16 from rising too much above a certain value and causing an unstable operation such as oscillation of the entire system. When the dimming degree becomes deep (dark) and the dimming signal B becomes smaller than the limiting signal G again, the output of the comparator 19 causes the inverter 20 to invert again,
The switch 22 side may be connected so that the dimming signal B is input to the variable error amplifier circuit 16.

FIG. 12 is a diagram showing the correspondence between the feedback control gain of the variable error amplifier circuit 16 and the dimming signal B. By setting the limiting signal G for the dimming signal B, the upper limit of the feedback control gain is set. It indicates that you want to set.

According to this example, the limiting circuit 17 outputs the limiting signal G
And the dimming signal B are compared, and when the dimming signal B is larger than the limiting signal G, it is regulated that the feedback control gain of the variable error amplification circuit 16 continues to increase with the magnitude of the dimming signal B. By doing so, unstable operation such as oscillation of the entire system can be prevented. Further, by setting an upper limit on the feedback control gain, the rate of change of the feedback control gain with respect to the dimming signal B is relatively increased, and even when the variation width of the dimming signal B is narrowed, the feedback gain is increased and abnormal oscillation or the like occurs. Can be prevented. In this example, the limit signal G output from the limit value generation circuit 18 of the limit circuit 17 prevents an abnormal increase in the feedback control gain of the variable error amplifier circuit 16.
It is also possible to prevent the feedback control gain from abnormally increasing by setting a limit value to 6 itself.

[0042]

According to the first aspect of the present invention, in a device for performing feedback control by detecting a lamp current signal flowing in a discharge lamp, feedback control to a high frequency power source is performed when a dimming signal reaches a preset value. Since the control signal for input is blocked, it is only necessary to detect the lamp current signal in a more limited range. Therefore, the dynamic range of the actually required detection range should be relatively wide. Therefore, there is an effect that detection accuracy can be improved and noise resistance can be improved.

In the invention according to claim 2, the dimming degree of the dimming signal is approximately 40 to 100% or 60 to 1 with respect to the total light.
Since the signal amplified by the error amplification circuit is prevented from being input to the high frequency power supply when the dimming degree is within the range of 00%, that is, when the dimming degree reaches 40 to 60%, the high frequency power supply receives the error amplification. Since the circuit starts to prevent the input of the amplified signal, the range in which unnecessary feedback control is omitted can be increased, so that the dynamic range of the lamp current signal in the necessary detection range can be widened, and the individual discharge lamp lighting device can be used. It has an effect of being able to well prevent the difference and flicker due to the difference.

According to the third aspect of the present invention, a plurality of load circuits and current detection circuits are provided for the high frequency power source, and the lamp current signals output from the respective current detection circuits are compared and the smaller value side is subtracted. Therefore, the feedback control is performed based on the lamp current signal of the discharge lamp on the side that is most likely to be extinguished, so that the dimming of a plurality of discharge lamps can be stably performed.

In the invention according to claim 4, a plurality of load circuits and current detection circuits are respectively provided in parallel with the high frequency power supply, and each load circuit and current detection circuits are provided through a balancer transformer. It has an effect that the dimming of the discharge lamp can be stably performed.

In the invention according to claim 5, a temperature detecting circuit for detecting the ambient temperature is provided, and when the temperature detected by this temperature detecting circuit is below a certain value, the value of the lamp current signal is reduced to the subtractor. In order to output, feedback control is performed based on a value lower than the actually detected value, and compensation for the dimming degree can be increased only when the temperature is low, which has the effect of improving the dimming stability at low temperatures.

In the invention according to claim 6, there is at least a sequence control circuit for performing a sequence of turning off and turning on the discharge lamp, and when the sequence control circuit is in the turning off state of the discharge lamp, the control signal is input to the high frequency power supply. Therefore, when the discharge lamp is not turned on, the control signal for feedback control is not input to the high frequency power supply, and it is possible to prevent malfunction when the discharge lamp is turned off. .

In the invention according to claim 7, when the discharge lamp is in the extinguished state, the sequence control signal corresponding to the extinguished state is input to the high frequency power source instead of the control signal. In addition to preventing the erroneous operation, the change in the current flowing through the discharge lamp can be reduced when the sequence changes from extinguishing to lighting, and steep light emission can be prevented.

In the eighth aspect of the invention, the error amplifier circuit sets the output to 0 when the dimming signal reaches a preset value. Therefore, it is simpler to stop the feedback control depending on the dimming degree. It has the effect that can be realized by such a configuration.

According to the ninth aspect of the invention, the error amplifying circuit is a variable error amplifying circuit in which the feedback control gain is increased as the dimming degree of the dimming signal becomes deeper and becomes smaller as the dimming degree becomes shallower. Since the feedback control gain is gradually amplified according to the magnitude of the dimming signal,
This has the effect of suppressing abrupt changes in the control signal and thus preventing abrupt changes in the optical output of the discharge lamp.

According to the tenth aspect of the present invention, since the feedback control gain of the error amplifying circuit is provided with a limiting circuit for preventing the magnitude of the feedback control gain from exceeding a certain level, the dimming signal increases and the feedback control gain continues to increase. This has the effect of restricting this and preventing unstable operation such as oscillation of the entire system.

[Brief description of drawings]

FIG. 1 is a configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating operation / non-operation of feedback control according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining operation / non-operation of feedback control according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram according to a third embodiment of the present invention.

FIG. 6 is a diagram for explaining the operation of the temperature detection circuit according to the third embodiment of the present invention.

FIG. 7 is a partial configuration diagram according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating a sequence of the sequence control circuit according to the fourth embodiment of the present invention.

FIG. 9 is a configuration diagram according to a fifth embodiment of the present invention.

FIG. 10 is a diagram for explaining operation / non-operation of feedback control according to the fifth embodiment of the present invention.

FIG. 11 is a configuration diagram according to a sixth embodiment of the present invention.

FIG. 12 is a diagram illustrating the upper limit of the feedback control gain according to the sixth embodiment of the present invention.

FIG. 13 is a configuration diagram of a conventional device.

FIG. 14 is a diagram illustrating an operation of a conventional device.

[Explanation of symbols]

1 is a commercial power supply, 2 is a high frequency power supply, 3 is a load circuit, 4 is a discharge lamp, 5 is a current detection circuit, 7 is a feedback control circuit, 8 is a subtractor, 9 is an error amplification circuit, 12 is an adder, and 13 is A switch, 15 is a comparison circuit, 16 is a variable error amplifier circuit, 17 is a limit circuit, 18 is a limit signal generation circuit, 19 is a comparator, 2
0 is an inverter, 21 and 22 are switches, 30 is a balancer transformer, 31 is a switching circuit, 32 is a comparator, 33 and 34 are contacts, 35 is a temperature detection circuit, 36 is a second adder, 40
Is a sequence control circuit, 41 is a switching circuit, 42 and 43 are contacts, A is a lamp current signal, B is a dimming signal, C is an error signal, D is an amplified signal, E is a control signal, and F is an operation switching adjustment. A light intensity signal, G is a limit signal, H is a temperature detection signal, I is a sequence control signal, and J is a preheat start abnormality protection signal.

Front page continuation (72) Kenichiro Nishi Nishino 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. (72) Inventor Jun Jun 2-3 2-3 Marunouchi 2-3, Chiyoda-ku, Tokyo Sanryo Denki Co., Ltd. (72) Inventor Takeshi Arai 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. (72) Inventor Koji Shibata 2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. Within

Claims (10)

[Claims] 1. A load circuit including a discharge lamp, a high frequency power supply for supplying the load circuit with high frequency power higher than a commercial power supply, and a current detection for detecting a lamp current flowing through the discharge lamp and outputting a lamp current signal. A circuit, a dimming unit for controlling the high frequency power source to output a dimming signal for dimming the discharge lamp, and an error amplification circuit for amplifying an error between the lamp current signal and the dimming signal. And an adder that adds the signal amplified by the error amplification circuit and the dimming signal to a control signal and outputs the control signal to the high frequency power source. When the dimming signal reaches a preset value, A discharge lamp lighting device, characterized in that a signal amplified by the error amplification circuit is prevented from being input to a high frequency power supply. 2. The signal amplified by the error amplification circuit is input to the high frequency power supply when the dimming degree of the dimming signal is in the range of about 40 to 100% or 60 to 100% with respect to the total light. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is configured to prevent such a situation. 3. A plurality of load circuits and current detection circuits are provided for each high-frequency power source, and the lamp current signals output from the respective current detection circuits are compared to output the side with the smaller lamp current to the subtractor. Claim 1 characterized by
The discharge lamp lighting device as described in the above. 4. The load circuit and the current detection circuit are respectively provided in parallel with respect to the high frequency power supply, and each load circuit and the current detection circuit are provided via a balancer transformer. Discharge lamp lighting device. 5. A temperature detecting circuit for detecting the ambient temperature is provided, and when the temperature detected by this temperature detecting circuit is below a certain value, the value of the lamp current signal is reduced and output to a subtractor. The discharge lamp lighting device according to claim 1. 6. A sequence control circuit for carrying out a sequence of at least extinguishing and lighting of a discharge lamp, wherein a control signal is input to a high frequency power source when the sequence control circuit is in the extinguished state of the discharge lamp. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is configured to prevent the discharge lamp. 7. The sequence control circuit, when the discharge lamp is in the extinguished state, converts the sequence control signal corresponding to the extinguished state into a control signal and inputs it to the high frequency power supply. The discharge lamp lighting device described. 8. The discharge lamp lighting device according to claim 1, wherein the error amplifier circuit sets the output to 0 when the dimming signal reaches a preset value. 9. The error amplifying circuit is a variable error amplifying circuit that increases the feedback control gain as the dimming degree of the dimming signal becomes deeper and darker, and decreases the feedback control gain as the dimming degree becomes shallower and brighter. 8. The discharge lamp lighting device according to item 8. 10. The discharge lamp lighting device according to claim 8, further comprising a limiting circuit for preventing the magnitude of the feedback control gain of the error amplification circuit from exceeding a certain level.