JPH11317298A - Lighting device for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a uniform starting characteristic in spite of errors in production, when electric power larger than the rated electric power is supplied in the time of starting of the discharge lamp to secure the sufficient amount of light from just after the starting, in the time of the constant power control of the lamp. SOLUTION: A microcomputer circuit 21 stores detected lamp voltage at the time of stable lighting of the high-pressure discharge lamp 7 in an EEPROM 29, in every lighting. During initial phases of the operating, if the lamp voltage is lower than, for example, 68V, the microcomputer circuit 21 controls a lighting circuit 5 to supply electric power larger than the rated power to the high- pressure discharge lamp 7. In this case, a CPU 26 of an arithmetic circuit 22 reads the detected lamp voltage in the time of the previous lighting from the EEPROM 29. And the CPU 26 looks up a data table stored in a ROM 27 to regulate a load characteristic of the high-pressure discharge lamp 7, according to the lamp voltage read in from the EEPROM 29.

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 for lighting a discharge lamp by controlling lamp power to a constant value.

[0002]

2. Description of the Related Art When a high-pressure discharge lamp is controlled so that its lamp power is constant, the high-pressure discharge lamp has a temperature dependency, so that the amount of light is insufficient at the rated power from the beginning of operation. Therefore, a technique is used in which a power larger than the rated power is supplied at the time of starting the lamp and a sufficient amount of light is secured immediately after the lamp is started.

[0003]

However, due to a manufacturing error of the lamp, even if the lamp is lit by the same lighting circuit, the startability differs depending on the lamp.

FIG. 5 is a graph showing an example of a variation in lamp light quantity when a lamp is lit by a lighting circuit using the above-mentioned conventional technique. is there. FIG. 5A shows an example when the lamp voltage at the time of stability is 42 V, and FIG. 5B shows an example when the lamp voltage at the time of stability is 52 V. As can be seen from FIG. 5, the difference in the lamp voltage at the time of stability is the difference in the lamp light amount. That is, when the lamp voltage at the time of stability is 42 V, the value of the lamp light amount about 8 seconds after the start of the lamp is about 1.5 times the lamp light amount at the stable time only for a short time. Therefore, when the lamp voltage at the time of stability is 52 V, it reaches only about half of the lamp light amount at the time of stability.

As described above, due to the manufacturing error of the lamp,
There is a problem that the lamp light quantity cannot be quickly started or that excessively bright light is emitted for a short time.

An object of the present invention is to supply a power larger than a rated power at the time of starting a discharge lamp and to secure a sufficient amount of lamp light immediately after the start of the discharge lamp when performing a constant power control of the lamp power. Another object of the present invention is to make the starting characteristics uniform even by the production error of the discharge lamp.

[0007]

According to the present invention, there is provided a lighting device for a discharge lamp, comprising: a discharge lamp; a lighting circuit for supplying electric power to the discharge lamp for lighting; and detecting a lamp voltage of the discharge lamp. A voltage sensor; a current sensor for detecting a lamp current of the discharge lamp; and a target lamp current value obtained by dividing a preset target lamp power value by the detected lamp voltage, to adjust the detected lamp current. A constant power operation control means for controlling the lighting circuit; a non-volatile storage device for storing the power; and a power larger than a rated power to the discharge lamp when the detected lamp voltage is low by a predetermined amount at the beginning of the operation of the discharge lamp. The lighting circuit is controlled so as to supply the load, and at this time, the load characteristic of the discharge lamp is stored in the nonvolatile storage device, and the detection at the previous lighting is performed. And an overpower operation control means for adjusting such that the one corresponding to the value of the lamp voltage.

[0008] Therefore, when the detected lamp voltage is low by a predetermined degree at the beginning of the operation of the discharge lamp, when controlling the lighting circuit so as to supply a power larger than the rated power to the discharge lamp, the load characteristic of the discharge lamp is determined by the load characteristic of the discharge lamp. It can be adjusted so as to correspond to the detected lamp voltage value at the time of lighting.

According to a second aspect of the present invention, in the discharge lamp lighting device according to the first aspect, the overpower operation control means sets a load characteristic to be adjusted to a peak value of the lamp current.

Therefore, the peak value of the lamp current of the discharge lamp can be adjusted so as to correspond to the detected lamp voltage value at the time of the previous lighting of the discharge lamp.

According to a third aspect of the present invention, in the discharge lamp lighting device according to the first or second aspect, the overpower operation control means adjusts the load characteristic to be adjusted so that the lamp current according to the change in the lamp voltage has a peak. It is the change when falling from the value.

Therefore, the change when the lamp current falls from the peak value can be adjusted so as to correspond to the detected lamp voltage value at the time of the previous lighting of the discharge lamp.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a circuit diagram of a lighting device 1 for a discharge lamp according to this embodiment. As shown in FIG. 1, reference numeral 2 denotes a main circuit, and a power supply line of a DC power supply 3 of the main circuit 2 includes a smoothing capacitor 4, a lighting circuit 5, a starter 6,
The high-pressure discharge lamps 7 are sequentially connected.

The lighting circuit 5 includes a step-up transformer 11 and an output of the lighting circuit 5 on the primary side of the step-up transformer
A main switching element 12 for controlling, a PWM converter 13 which is an IC for driving the main switching element 12 on and off variably with a duty ratio, and a rectifying circuit 14 for rectifying an output on the secondary side of the step-up transformer 11. , And a smoothing circuit 15 for smoothing. The starter 6 is a high-pressure discharge lamp 7
Start by applying a start pulse to.

The voltage sensor 16 detects the lamp voltage of the high-pressure discharge lamp 7 using the divided voltage of the resistor, and the current sensor 17 detects the lamp current of the high-pressure discharge lamp 7. The voltage sensor 18 detects the voltage between the power supply lines of the lighting circuit 5 by using the divided voltage of the resistor.

The microcomputer circuit 21 includes an arithmetic circuit 22, a timer 23, an A / D converter 24, and a D / A converter 25.

The arithmetic circuit 22 stores, in the CPU 26, a ROM 27 storing predetermined programs and fixed data,
M28, EEPROM 29 and the like are connected by a bus.
The output of the voltage sensor 16 is supplied to the A / D
The data is A / D converted by the converter 24 and input to the arithmetic circuit 22. The output of the arithmetic circuit 22 is D / A converted by a D / A converter 25.

The output of the arithmetic circuit 22 after the D / A conversion is input to the inverting input terminal of the comparator 32, and the output of the current sensor 17 is input to the non-inverting input terminal.

The output of the voltage sensor 18 is input to the non-inverting input terminal of the comparator 33, and a predetermined reference voltage is input to the inverting input terminal.

The output voltages of the comparators 32 and 33 are input to the analog OR circuit 34, and the analog OR circuit 34
Takes the OR of these two output voltages and outputs the output to PWM.
Output to the converter 13.

The timer 23 is connected to the arithmetic circuit 22, and has four timers a, b, c, and d.

In the following, the operation of the discharge lamp lighting device 1 will be described focusing on the microcomputer circuit 21 with reference to the flowchart of the operation of the microcomputer circuit 21 shown in FIGS. The following describes that the rated lamp voltage is 85
This is an example in the case of V.

First, when the microcomputer circuit 21 is turned on,
The memory and the like are initialized (step S1), and the timers a, b, c, and d of the timer 23 start counting (step S2).

When the lighting device 1 for the discharge lamp is started, a relatively high voltage is output from the lighting circuit 5 and the voltage between both ends of the unlit high-pressure discharge lamp 7 is, for example, 3
Maintain as high as about 00 to 500 V (voltage output at no load). This is because the transition from glow discharge to arc discharge cannot be performed only by the output of the starter 6. The voltage between both ends of the high-pressure discharge lamp 7 is detected by the voltage sensor 18, and this voltage is compared with a predetermined reference voltage by the comparator 33 until the voltage falls below a certain level, that is, the high-pressure discharge lamp 7 is turned on. Until the determination is made, the comparator 33 outputs an ON signal to the PWM converter 34 via the analog OR circuit 34.

Therefore, the microcomputer circuit 21 starts each of the timers a, b, c and d (step S2),
The output voltage of the voltage sensor 16 is fetched via the A / D converter 24 (step S3). Until the timer b elapses 1 second (N in step S4), is the output voltage of the voltage sensor 16 lower than, for example, 105 V? The determination as to whether or not is repeated (step S5). When the output voltage falls below 105 V (Y in step S5), the high-pressure discharge lamp 7
Is determined to be lit, and the timer b is stopped (step S7). If the output voltage of the voltage sensor 16 is 105 V or more within one second from the start of counting by the timer b,
The timers a and c are kept reset (step S6). When the timer b has passed 1 second without the output voltage dropping below 105 V, zero is output to the D / A converter 25 and PW
The M converter 13 is turned off, the operation of the microcomputer circuit 21 is stopped, and the operation of the discharge lamp lighting device 1 is notified by turning on an LED (not shown) (step S15). That is, since the timer b outputs a high voltage at no-load voltage output, when the high-pressure discharge lamp 7 does not turn on even if the no-load voltage output is maintained for a fixed short time, in this example, one second, in this example. , A timer for stopping the operation to protect the circuit.

After steps S3 to S7, the detected voltage of the voltage sensor 16 is taken into the arithmetic circuit 22 as a ramp voltage (step S8), and the count value of the timer a is set to 1 ms.
Is set to the rated current, 0.41 A in this example (step S10), and the digital control signal is output to the D / A converter 25 (step S10).
21). That is, a signal serving as a reference voltage for setting the lamp current to 0.41 A is output to the comparator 32 via the D / A converter 25, and is compared with the detection signal of the current sensor 17 to generate an ON signal or Outputs off signal. After the start of the high-pressure discharge lamp 7 is thus confirmed (Y in step S5), the rated current is maintained for a short time and the high-pressure discharge lamp 7 is maintained.
Is operated in order to cancel the delay of the control system at the moment when the lighting device 1 of the discharge lamp is started and to prevent the control system from running away.

After driving the high-pressure discharge lamp 7 at a lamp current of 0.41 A for 1 ms, the following processing is performed.
That is, it is determined whether the lamp voltage taken in step S8 is not lower than a predetermined low voltage, in this example, 3V (step S11). This determination is for determining whether or not the circuit is short-circuited. When the voltage is 3 V or less, the operation is stopped and the stop of the high-pressure discharge lamp 7 is notified (step S15).

If it is determined in step S11 that the lamp voltage is not short-circuited (Y in step S11),
It is determined whether the lamp voltage exceeds 28 V in this example (step S12). 28V increases the maximum lamp power (75 W in this example) to the maximum lamp current (2.6 in this example).
When the lamp voltage is equal to or less than 28 V (N in step S12), the execution of the routine for setting the lamp current to a predetermined constant current and executing the operation is selected (step S2).
0). This constant current routine acts as a limiter for the output current.

If the lamp voltage is higher than 28 V (Y in step S12), it is determined whether the lamp voltage is higher than 68V. This value of 68 V is equivalent to the rated lamp voltage of 85 V and the tolerance of 17 V. Therefore, if the high pressure discharge lamp 7 is as specified in the specification,
When the lamp voltage falls below 68 V, it is determined that the high-pressure discharge lamp 7 is cold. Lamp voltage is 68V
If there is the above (Y in step S13), it is determined whether the voltage is lower than 105V (step S14). This is to detect that no load has occurred due to the falling off of the high-pressure discharge lamp 7 when the lamp voltage exceeds 105 V (N in step S14). In that case, the operation of the discharge lamp lighting device 1 is stopped, and the fact is notified by an LED (not shown) (step S1).
5).

If the lamp voltage is lower than 105 V, a constant power routine for operating the lamp power of the high-pressure discharge lamp 7 at a constant level, for example, 35 W in this example, is executed (step S17). That is, the detection value of the voltage sensor 16 is taken into the arithmetic circuit 22, and the target lamp power value is divided by the detection value of the voltage sensor 16 to obtain a target lamp current value. The value is output to the comparator 32 and compared with the lamp current detected by the current sensor 17.
The signal is output to the PWM converter 13 via the circuit 34.

If the lamp voltage is 68 V or less in step S13 (N in step S13), it is determined that the high-pressure discharge lamp 7 is cold. In such a case, if the lamp is driven at the rated power from the beginning of the operation, the amount of lamp light is insufficient. Therefore, in order to supply power larger than the rated power at the time of starting the lamp and to secure a sufficient amount of light immediately after starting the lamp,
The following processing is performed.

That is, until the timer c elapses, for example, 20 seconds (N in step S16), the EEPROM 2
9 and reads the lamp voltage value at the time of stable operation at the time of the previous lamp lighting (storage processing of the lamp voltage value will be described later), and looks up a predetermined data table stored in the ROM 27. Then, a load characteristic corresponding to the read lamp voltage value is read from the data table (step S18). Then, based on the read value, the overdrive routine (step S19), that is, from the rated power (35 W in this example)
Operate with large power.

The load characteristics mentioned here are characteristics of lamp power and lamp current according to the lamp voltage of the high-pressure discharge lamp 7 as shown in FIG. That is, as shown in FIG. 4, the peak value of the lamp current is varied as shown by an arrow 41 (in this case, the rising characteristic of the corresponding lamp power fluctuates as shown by an arrow 42) or the lamp current is changed. Is changed as shown by an arrow 43 (in this case, the corresponding fall characteristic of the lamp power fluctuates as shown by an arrow 44). Then, the load characteristic of the electric power value (current value) is varied as shown in FIG. 4, and the lamp current value is increased or decreased by a predetermined amount at a predetermined timing in accordance with the level of the lamp voltage at the time of the stable operation at the time of the previous lamp lighting. I do. Note that the overdrive routine in step S19 has a double setting with the constant current routine in step S20.

As a more specific example, for example, in the example shown in FIG. 5A described above, about 7 seconds after the start of the rise of the lamp current, it suddenly decreases from the time when the lamp light intensity reaches 100%. Adjust to reduce the lamp current. Thereby, it is possible to prevent a problem that excessively bright light is emitted for a short time. In addition, FIG.
In the example shown in FIG.
Since the lamp current sharply decreases after a few seconds, more lamp current can be supplied from this point to quickly increase the amount of lamp light.

After the elapse of 20 seconds from the timer c (Y in step S16), the routine shifts from the overdrive routine to the constant power routine. This is to prevent the circuit from being burdened by a long overdrive routine.

When the timer d reaches the predetermined time A seconds (Y in step S22), the lamp voltage after A seconds is set to E.
It is stored in the EPROM 29 (step S23), and the timer d is stopped (step S24). A seconds counted by the timer d is a time period in which the lighting device 1 of the high-pressure discharge lamp is considered to be in a stable state after starting, for example, 30 seconds to 1 minute. At this time, the lamp voltage stored in the EEPROM 29 is used in the execution of the overdrive routine at the next lighting (step S19).

[0038]

According to the first aspect of the present invention, when the lighting circuit is controlled to supply power greater than the rated power to the discharge lamp when the detected lamp voltage is low by a predetermined amount at the beginning of operation of the discharge lamp, Since the load characteristics of the lamp can be adjusted so as to correspond to the detected lamp voltage value at the time of stable operation at the last lighting of the discharge lamp, the discharge lamp of the discharge lamp can be adjusted from the detected lamp voltage value of stable operation at the previous operation. By judging the starting characteristics, manufacturing errors of the discharge lamp can be absorbed, and the starting characteristics can be made uniform.

According to a second aspect of the present invention, in the first aspect of the present invention, the peak value of the lamp current of the discharge lamp is adjusted so as to correspond to the detected lamp voltage value when the discharge lamp was lit last time. As a result, manufacturing errors of the discharge lamp can be absorbed, and the starting characteristics can be made uniform.

According to a third aspect of the present invention, in the first or second aspect of the invention, the change when the lamp current falls from the peak value corresponds to the detected lamp voltage value when the discharge lamp was last turned on. By adjusting so that the manufacturing error of the discharge lamp is absorbed, the starting characteristics can be made uniform.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a lighting device for a high-pressure discharge lamp according to an embodiment of the present invention.

FIG. 2 is a flowchart of an arithmetic circuit of the lighting device for the high-pressure discharge lamp.

FIG. 3 is a flowchart of an arithmetic circuit of the lighting device for the high-pressure discharge lamp.

FIG. 4 is a graph showing load characteristics of a lighting device of the high-pressure discharge lamp.

FIG. 5 is a graph of a lamp current and a lamp light amount for explaining a problem of a conventional high pressure discharge lamp lighting device;
(A) shows a case of a stable lamp voltage of 42 V, and (b) shows a case of a stable lamp voltage of 52 V.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-pressure discharge lamp lighting device 5 Lighting circuit 7 Discharge lamp 16 Voltage sensor 17 Current sensor 29 Non-volatile storage device

Claims (3)

[Claims] A discharge lamp; a lighting circuit for supplying power to the discharge lamp and lighting the discharge lamp; a voltage sensor for detecting a lamp voltage of the discharge lamp; a current sensor for detecting a lamp current of the discharge lamp; Constant power operation control means for controlling the lighting circuit so as to adjust the detected lamp current, using a quotient obtained by dividing a preset target lamp power value by the detected lamp voltage as a target lamp current value; A non-volatile storage device for storing a detected lamp voltage at the time of stable lighting of the lamp; and, when the detected lamp voltage is low by a predetermined amount at the beginning of the operation of the discharge lamp, the lighting circuit to supply power greater than a rated power to the discharge lamp. The load characteristic of the discharge lamp is stored in the non-volatile storage device at this time, and the value of the detected lamp voltage at the time of previous lighting is stored. And an over-power operation control means for adjusting the operation of the discharge lamp in accordance with the following. 2. The discharge lamp lighting device according to claim 1, wherein the overpower operation control means uses a load characteristic to be adjusted as a peak value of the lamp current. 3. The discharge lamp according to claim 1, wherein the overpower operation control means sets the load characteristic to be adjusted to a change when a lamp current corresponding to a change in the lamp voltage falls from a peak value. Lighting device.