JP2003031394A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of stably starting and lighting a discharge lamp while suppressing a cost increase, and coping with a change such as the momentary drop of supply voltage. SOLUTION: A control circuit 8 is composed of a control part 8a comprising a microcomputer; a comparator 11 for comparing a primary side current flowing to a switching element Q1 when the switching element Q1 is turned on, with a primary side current peak value outputted from the control part 8a; and an RS flip-flop 12 inputting the output signal of the comparator 11 and an ON timing signal from the control part 8a into a set terminal S and outputting a signal for controlling the switching element Q1. The control part 8a is constituted to have more frequency of performing current error operation which is error operation, to perform feedback control than the frequency of performing operation for obtaining a lamp current command value which is a load current command value.

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 high intensity discharge lamp (HID lamp) such as a metal halide lamp.

[0002]

2. Description of the Related Art A high-intensity discharge lamp such as a metal halide lamp has a characteristic of high brightness, and in recent years, it has been used for in-vehicle applications. In recent years, there have been increasing demands for smaller size and lower cost of in-vehicle discharge lamp lighting devices that are used for in-vehicle applications. Computers are being used.

FIG. 25 shows a circuit example of a discharge lamp lighting device for lighting a discharge lamp composed of a high-intensity discharge lamp. The discharge lamp lighting device configured as shown in FIG. 25 includes a DC power supply 1 and a DC power supply 1
The voltage at which the lamp La, which is a discharge lamp, can be turned on (the voltage required to stably turn on the lamp La)
DC-DC conversion circuit 2 that steps up and down to and an inverter circuit (polarity inversion circuit) that converts the DC voltage output from the DC-DC conversion circuit 2 into an alternating voltage and applies it to the lamp La.
3, a starting device 4 including an igniter that generates a high-voltage starting pulse for starting the lamp La, a drive circuit 5 that drives the switching elements Q2 to Q5 of the inverter circuit 3, and a lamp voltage that detects the lamp voltage. Control for controlling the output voltage of the DC-DC conversion circuit 2 by sampling the detection unit 6, the lamp current detection unit 7 for detecting the lamp current, the output of the lamp voltage detection unit 6 and the output of the lamp current detection unit 7, respectively. And a circuit 8. Here, the lamp La and the starting device 4 function as a load circuit including the lamp La as a load.

The DC-DC conversion circuit 2 is a flyback type DC-CC converter, and a series circuit of a primary winding of a transformer T1 and a switching element Q1 composed of a MOSFET is connected between both ends of a DC power supply 1. And the transformer T
A series circuit of a diode D1 and a smoothing capacitor C1 is connected between both ends of the secondary winding of No.1. Diode D
1 is connected to a polarity that blocks the charging current from the transformer T1 to the capacitor C1 when the switching element Q1 is turned on. That is, electromagnetic energy is accumulated in the transformer T1 when the switching element Q1 is turned on, this electromagnetic energy is discharged from the transformer T1 when the switching element Q1 is turned off, and a charging current flows through the capacitor C1 through the diode D1.

The control circuit 8 controls ON / OFF of the switching element Q1 at a high frequency, and the control circuit 8 controls the output voltage of the DC-DC conversion circuit 2 by changing the on-duty of the switching element Q1. .
In addition, the lamp voltage detection unit 6 uses the potential at the connection point between one end of the capacitor C1 and the anode of the diode D1 to generate a DC voltage.
The output voltage of the DC conversion circuit 2 is detected as a lamp voltage, and the lamp current detection unit 7 uses a current transformer CT for current detection provided between the other end of the capacitor C1 and the inverter circuit 3 to form a DC-DC conversion circuit. The output current of 2 is detected as the lamp current. The control circuit 8 changes the on-duty of the switching element Q1 on the basis of the lamp voltage detected by the lamp voltage detection unit 6 and the lamp current detected by the lamp current detection unit 7, so that the DC-DC conversion circuit 2 operates. It controls the output voltage.
The control circuit 8 controls the on / off of the switching element Q1 so that the output voltage of the DC-DC conversion circuit 2 becomes a specified constant voltage during the no-load period before the lamp La is turned on.

The output voltage of the DC-DC conversion circuit 2 is input to the inverter circuit 3. The inverter circuit 3 is a MOS
It is provided with four switching elements Q2 to Q5 each composed of an FET, and two arms each composed of a series circuit of two switching elements Q2 to Q5 are connected in parallel to form a bridge connection, and the switching element Q2 in each arm is connected. ~
The connection point of Q5 is used as the output terminal. Switching element Q
2 to Q5 are turned on and off by the control circuit 8 by the control circuit 8 so that the high potential side switching elements Q2 and Q3 of one arm and the low potential side switching elements Q4 and Q5 of the other arm coincide with each other. Controlled via 5. That is, when the switching elements Q2 and Q5 are on, the switching elements Q3 and Q4 are off, and when the switching elements Q3 and Q4 are on, the switching elements Q2 and Q5 are off. Switching element Q2 forming the inverter circuit 3
~ Q5 is turned on and off at a relatively low frequency, and the lamp La
A rectangular wave alternating voltage is applied to. However, the lamp La
Before lighting, the control circuit 8 controls the switching elements Q3, Q of the switching elements Q2 to Q5 of the inverter circuit 3.
Only 4 is turned on and the switching elements Q2 and Q5 are kept off (initial setting).

The control circuit 8 outputs a command value of the power to be supplied to the lamp La (lamp power command value), a lamp power command value generator 81, a lamp power command value, and a lamp voltage detected by the lamp voltage detector 6. A lamp current command value calculation unit 82 that calculates a lamp current command value based on the above (the lamp current command value calculation unit 82 calculates the lamp current command value by dividing the lamp power command value by the lamp voltage). , A current error calculation unit 83 that calculates a current error based on the lamp current command value and the lamp current detected by the lamp current detection unit 7 and outputs a primary-side current peak value, an on-timing that sets the on-timing of the switching element Q1 The control unit 8a including the setting unit 84 and the primary side current flowing through the switching element Q1 when the switching element Q1 is on and the current error. A comparator 11 for comparing the primary current peak value outputted from the arithmetic unit 83, an output terminal set terminal S of the on-timing setting section 84 together with the output terminal connected to a reset terminal R of the comparator 11
And an RS flip-flop 12 which controls the switching element Q1 to be turned on / off by an output signal. The control unit 8a is realized by a microcomputer.

The set terminal S of the RS flip-flop 12
A rectangular wave signal as shown in FIG. 26A is input from the on-timing setting unit 84, and the primary side current flowing through the switching element Q1 turns on the switching element Q1 as shown in FIG. Since it gradually increases from the time point, assuming that the current-side error calculating unit 83 outputs the primary-side current peak value as shown by the broken line in FIG. 7B, the primary-side current exceeds the primary-side current peak value. At the same time, an H level signal is input to the reset terminal R of the RS flip-flop 12, and the output signal of the RS flip-flop 12 changes from H level to L level. That is, RS
From the flip-flop 12, P as shown in FIG.
A WM (pulse width modulation) signal will be output. When the primary-side current does not reach the primary-side current peak value, the on-time of the rectangular wave signal output from the on-timing setting unit 84 becomes equal to the on-time of the PWM signal output from the RS flip-flop 12. .

The operation of the control section 8a will be described below with reference to the flowchart of FIG.

When the power is turned on, the program of the microcomputer starts, and the switching elements Q2 to Q5 of the inverter circuit 3 are initialized (S1). In the initial setting of the inverter circuit 3, the switching element Q
Among the elements 2 to Q5, only the switching elements Q3 and Q4 are turned on and the switching elements Q2 and Q5 are kept off. After the initial setting of the inverter circuit 3 is performed, the initial setting on the microcomputer is performed (S2). afterwards,
The lamp La is controlled by applying a no-load voltage to the lamp La before performing lighting and applying a starting pulse (for example, a voltage of 20 kV) from the starting device 4 to the lamp La.
Is started (S3). Here, with no load control,
The ON / OFF of the switching element Q1 of the DC-DC conversion circuit 2 is set to a lower frequency than in the normal operation period.

Then, it is judged whether or not the lamp La is turned on (S4), and if the lamp La is not turned on, no-load control is performed. That is, the no-load control is continued until the lamp La is turned on. On the other hand, when the lamp La is turned on, a power command value as shown in FIG. 28 is output for several tens of seconds from the start in order to raise the luminous flux of the lamp La, and the on-timing setting unit 84 outputs the above rectangular wave signal. The output is started (S5). The electric power command value has a curve as shown in FIG. 28, but the electric power command value becomes a constant value in the stable lighting state of the lamp La, and the lamp electric power command value is read from the lamp electric power command value generation unit 81. (S
6) Then, the lamp voltage is read from the lamp voltage detector 6 (S7), and the lamp current command value is obtained by dividing the lamp power command value by the lamp voltage (S8). Next, the lamp current is read from the lamp current detector 7 (S
9), the primary current peak value is calculated from the error between the lamp current command value and the lamp current (S10), and the primary current peak value is output (S11). Next, it is determined whether a predetermined time has passed (S12), and if the predetermined time has passed, the switching element of the inverter circuit 3 is controlled so that the output voltage of the inverter circuit 3 becomes an alternating voltage of a rectangular wave. Q2-
The on / off of Q5 is started (S13). After turning on / off the switching elements Q2 to Q5 or when the above predetermined time has not elapsed, it is determined whether the power supply voltage is within the standard range (S14), and the power supply voltage is within the specified range. If it has not entered, it is judged whether or not it should be restarted (S16). If it is judged that it should be restarted, the process returns to S1, and if it is judged that it should not be restarted, it is stopped. On the other hand, when the power supply voltage is within the specified range, it is determined whether or not the lamp La is on (S1).
5) If the lamp La is on, the process returns to S6. on the other hand,
If the lamp La is not turned on (when it is determined that it is turned off), it is determined whether or not to restart (S16),
If it is determined that the restart should be performed, the process returns to S1, and if it is determined that the restart should not be performed, the process is stopped.

According to the above-mentioned flow chart, the controller 8a
Operates to turn on the lamp La. That is, in the stable lighting state after the luminous flux is raised, S6 to
By repeating the step of S15, the power supplied to the lamp La is controlled.

[0013]

By the way, in the discharge lamp lighting device having the above-mentioned conventional structure, since the calculation speed of the microcomputer constituting the control section 8a is limited, the lamp La is stably activated and lit. In addition, there is a problem that it cannot respond to a sudden change in power supply voltage or load such that the power supply voltage drops momentarily. Further, it is conceivable to use a microcomputer capable of high-speed calculation so as to cope with such a situation, but the cost becomes very high, and it is difficult to meet the demand for cost reduction. was there.

The present invention has been made in view of the above circumstances, and an object thereof is to enable a discharge lamp to be stably started up and to be lit while suppressing an increase in cost, and a power supply voltage is momentarily lowered. An object of the present invention is to provide a discharge lamp lighting device capable of coping with such changes.

[0015]

In order to achieve the above object, the invention of claim 1 is a DC-DC conversion circuit for converting the output of a DC power supply into DC-DC by turning on / off a switching element, and a discharge lamp as a load. Load circuit to which electric power is supplied from the DC-DC conversion circuit, load voltage detection means for detecting the load voltage, load current detection means for detecting the load current, and load voltage detected by the load voltage detection means. Calculating a load current command value based on the above, performing an error calculation between the load current command value and the load current, and feedback-controlling ON / OFF of the switching element of the DC-DC conversion circuit according to the calculation result of the error calculation. DC-DC
A control circuit for adjusting the output of the conversion circuit is provided, and the control circuit is characterized in that the frequency of performing the error calculation and performing the feedback control is higher than the frequency of performing the calculation for obtaining the load current command value. The change in load current can be dealt with faster than before without increasing the calculation speed, and the discharge lamp can be lit more stably than before while suppressing an increase in cost.

According to a second aspect of the present invention, in the first aspect of the present invention, the control circuit changes the frequency of the above-mentioned two types of calculations according to the load state, so that the transient period and the lamp voltage in which the lamp voltage is unstable. However, it is possible to appropriately change the frequency of calculation during a stable period in which the discharge lamp is relatively stable, and it is possible to more stably turn on the discharge lamp.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the control circuit performs the error calculation at substantially constant time intervals except at least the time when the load state is unstable. During a period in which the lamp voltage is relatively stable compared to the current, it becomes possible to quickly respond to changes in the lamp current, and more stable lighting of the discharge lamp becomes possible.

According to a fourth aspect of the present invention, in the first to third aspects of the invention, the control circuit performs the proportional / integral control in the error calculation, so that the proportional / integral control can be realized and the quick response to the current error can be realized. Precise output adjustment is possible and stable lamp lighting is possible.

According to a fifth aspect of the invention, in the fourth aspect of the invention, the control circuit changes at least one of the proportional gain and the integral gain with respect to the current error value in the proportional-plus-integral calculation in a non-linear manner. The stability in the stable state can be improved as compared with the case where both and are linearly changed.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the invention, the control circuit is arranged such that, after the discharge lamp is started, until a predetermined time set according to the rising time of the luminous flux elapses. Since the proportional control is not performed, overshoot of the lamp current with respect to the target value can be prevented in a state where the lamp current is not stable as when the luminous flux is raised, and the stability at the time of luminous flux rise can be improved.

According to a seventh aspect of the present invention, in the invention according to the fourth or fifth aspect, the control circuit is arranged such that after the discharge lamp is started, DC is applied.
When the output power of the DC conversion circuit is equal to or more than a predetermined value set according to the power at the time of starting the luminous flux, proportional control is not performed, so that the lamp current with respect to the target value in the state where the lamp current is not stable as at the time of starting the luminous flux. The current overshoot can be prevented, and the stability at the time of starting the luminous flux can be improved.

According to the invention of claim 8, in the invention of claim 6, the control circuit gradually increases the proportional gain of the proportional control with time when the proportional control is started after a predetermined time has elapsed. The stability at startup can be further improved.

According to a ninth aspect of the present invention, in the fourth or fifth aspect of the invention, the control circuit provides a predetermined limit value for the amount of change in the integral control value by the integral gain with respect to the current error value. When the current error value at start-up is relatively large, the change amount of the integral control value is limited by the limit value. Therefore, it is possible to prevent the change amount of the integral control value from becoming too large and making stable rising difficult. be able to.

According to a tenth aspect of the present invention, in the invention according to the fourth or fifth aspect, the control circuit has at least the proportional gain and the integral gain of the proportional-plus-integral calculation according to the fluctuation of the input voltage to the DC-DC conversion circuit. Change one, so
It is possible to improve both stability and transient response.

According to the invention of claim 11, in the invention of claim 4 or 5, the control circuit raises the output of the DC-DC conversion circuit with respect to at least one of the proportional gain and the integral gain in the proportional-plus-integral calculation. Since the gain value is set to a large value compared to the gain value to be lowered, it is possible to prevent the lamp current from dropping too much and increase the lighting sustainability and stability when the power supply voltage drops momentarily. Can be made.

According to a twelfth aspect of the present invention, in the control circuit according to the fourth or fifth aspect of the invention, the control circuit is configured so that the change amount of the proportional control value by the proportional gain with respect to the current error value is D
When the output of the C-DC conversion circuit is increased, the amount of change in the proportional control value is held for a predetermined time after the output is increased, so the lamp current settles down during the predetermined time, and the power supply voltage is momentarily increased. It is possible to increase the lighting maintenance ability and stability when it is lowered.

According to a thirteenth aspect of the present invention, in the invention of the fourth or fifth aspect, the control circuit is configured such that when the change amount of the proportional control value by the proportional gain with respect to the current error value is a predetermined value or more,
When the output of the C-DC conversion circuit is increased, the amount of change in the proportional control value is decreased with a predetermined time constant, so that the lamp current oscillation can be suppressed, and when the power supply voltage instantaneously decreases. The lighting maintenance ability and stability of can be increased.

According to a fourteenth aspect of the present invention, in the inventions of the first to thirteenth aspects, since the control circuit is composed of at least a microcomputer, it is possible to reduce the size and cost of the entire discharge lamp lighting device.

According to a fifteenth aspect of the invention, there is provided an inverter circuit according to any one of the first to fourteenth aspects, wherein the output of the DC-DC conversion circuit is used as a power source to apply an alternating voltage to the load circuit, and the control circuit includes the inverter circuit. Since the control signal is output, the accuracy of the timing for controlling the inverter circuit is improved.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) The discharge lamp lighting device according to the present embodiment has the same basic structure as the conventional structure.
As shown in, the DC power supply 1 and the voltage of the DC power supply 1 are raised and lowered to a voltage at which the lamp La, which is a discharge lamp (high-intensity discharge lamp), can be turned on (a voltage required for stable lighting of the lamp La). DC-DC conversion circuit 2 for pressure and DC-D
An inverter circuit (polarity inversion circuit) 3 for converting the DC voltage output from the C conversion circuit 2 into an alternating voltage of a rectangular wave and applying it to the lamp La, and a high-voltage start pulse for starting the lamp La are generated. Starting device 4 consisting of an igniter
A drive circuit 5 for driving the switching elements Q2 to Q5 of the inverter circuit 3, a lamp voltage detector 6 for detecting a lamp voltage as a load voltage, a lamp current detector 7 for detecting a lamp current as a load current, and a DC An input voltage detection unit 9 that detects an input voltage to the -DC conversion circuit 2, an output voltage of the DC-DC conversion circuit 2 and an inverter by sampling the output of the lamp voltage detection unit 6 and the output of the lamp current detection unit 7, respectively. The control circuit 8 controls the output voltage of the circuit 3. That is, the lamp La is connected to the inverter circuit 3 via the starting device 4. The lamp La and the starting device 4 function as a load circuit including the lamp La as a load. Further, in this embodiment,
The lamp voltage detection unit 6 constitutes load voltage detection means, and the lamp current detection unit 7 constitutes load current detection means.

The DC-DC conversion circuit 2 includes a transformer T2,
Switching element Q1, diode D2, capacitor C
2 and C3, the switching element Q1
The voltage across the capacitor C3 can be adjusted by turning on / off the control circuit 8.

The control circuit 8 controls ON / OFF of the switching element Q1 at a high frequency, and the control circuit 8 controls the output voltage of the DC-DC conversion circuit 2 by changing the ON duty of the switching element Q1. .
Further, the lamp voltage detection unit 6 detects the voltage across the capacitor C3 (the output voltage of the DC-DC conversion circuit 2) as the lamp voltage, and the lamp current detection unit 7 detects the DC-DC conversion circuit 2 and the inverter circuit 3. An output current of the DC-DC conversion circuit 2 is detected as a lamp current by a current transformer CT2 for current detection provided between the two. The control circuit 8 changes the on-duty of the switching element Q1 on the basis of the lamp voltage detected by the lamp voltage detection unit 6 and the lamp current detected by the lamp current detection unit 7, so that the DC-DC conversion circuit 2 operates. It controls the output voltage. The control circuit 8 controls the on / off of the switching element Q1 so that the output voltage of the DC-DC conversion circuit 2 becomes a specified constant voltage during the no-load period before the lamp La is turned on.

The output voltage of the DC-DC conversion circuit 2 is input to the inverter circuit 3. The inverter circuit 3 is provided with four switching elements Q2 to Q5 made of MOSFETs as in the conventional configuration.
5 is controlled by the control circuit 8 via the drive circuit 5. The drive circuit 5 converts the control signal from the control circuit 8 into a voltage signal suitable for controlling the switching elements Q2 to Q5. After lighting the lamp La, the control circuit 8 turns off the switching elements Q3 and Q4 when the switching elements Q2 and Q5 are on, and turns off the switching elements Q2 and Q4 when the switching elements Q3 and Q4 are on.
The switching elements Q2 to Q5 are controlled so that Q5 is turned off. The switching elements Q2 to Q5 forming the inverter circuit 3 are turned on and off at a relatively low frequency, and a rectangular wave alternating voltage is applied to the lamp La. However, before the lamp La is turned on, the control circuit 8 controls the inverter circuit 3
Of the switching elements Q2 to Q5, for example, only the switching elements Q3 and Q4 are turned on, and the switching element Q
2, Q5 is kept off (initial setting).

As in the conventional configuration, the control circuit 8 includes a control section 8a composed of a microcomputer, a primary side current flowing through the switching element Q1 when the switching element Q1 is on, and a primary side current output from the control section 8a. A comparator 11 that compares the peak value, and a comparator 11
And an on-timing signal from the controller 8a is input to the set terminal S to control the switching element Q1 on / off by the output signal. The primary side current flowing through the switching element Q1 is detected by the current transformer CT1 for current detection. Further, the detection voltage by the above-mentioned input voltage detection unit 9 including a series circuit of two resistors R1 and R2 is input to the control unit 8a.

The operation of the controller 8a will be described below with reference to the flow chart of FIG.

When the power is turned on, the program of the microcomputer starts, and the switching elements Q2 to Q5 of the inverter circuit 3 are initialized (S1). In the initial setting of the inverter circuit 3, the switching element Q
Among the elements 2 to Q5, only the switching elements Q3 and Q4 are turned on and the switching elements Q2 and Q5 are kept off. After the initial setting of the inverter circuit 3 is performed, the initial setting on the microcomputer is performed (S2). afterwards,
The lamp La is controlled by applying a no-load voltage to the lamp La before performing lighting and applying a starting pulse (for example, a voltage of 20 kV) from the starting device 4 to the lamp La.
Is started (S3). Here, with no load control,
The ON / OFF of the switching element Q1 of the DC-DC conversion circuit 2 is set to a lower frequency than in the normal operation period.

Then, it is determined whether or not the lamp La is turned on (S4), and if the lamp La is not turned on, no-load control is performed. That is, the no-load control is continued until the lamp La is turned on. On the other hand, when the lamp La is turned on, the lamp power command value is set (S5), then the lamp voltage is averaged (S6), and the lamp power command value is divided by the lamp voltage to perform the calculation. A command value is obtained (S7). The control section 8a is provided with a digital filter for extracting the average value of the lamp voltage.

After obtaining the lamp current command value, it is judged whether or not the power source voltage is within the standard range based on the voltage detected by the input voltage detector 9 (S8), and the power source voltage is within the specified range. If not, it is determined whether or not to restart (S10), and if it is determined to restart, S1
Return to and stop if it should not be restarted.
On the other hand, if the power supply voltage is within the specified range, it is determined whether or not the lamp La is on (S9), and if the lamp La is on, the process returns to S5. On the other hand, the lamp La
If is not lit (judging it is off),
It is determined whether or not to restart (S10), the process returns to S1 if it is determined to restart, and stops if it is determined not to restart.

As can be seen from the above description, the lamp La
While is lit, S described in the flowchart of FIG.
The main loop consisting of steps 5 to S9 is repeated, but interrupts occur at a constant interrupt interval during the repetition, and the interrupt processing shown in FIG.
The interrupt process shown in is alternately performed.

In the interrupt process shown in FIG. 3 (a), the lamp voltage is read from the lamp voltage detector 6 (S21),
Next, the lamp current is read from the lamp current detector 7 (S22), a current error between the lamp current command value and the lamp current is calculated (S23), and the primary current peak value is output based on the result of the current error calculation. Yes (S24). Next, it is determined whether or not a predetermined time has elapsed (S25), and if the predetermined time has elapsed, the switching element of the inverter circuit 3 is adjusted so that the output voltage of the inverter circuit 3 becomes an alternating voltage of a rectangular wave. Start turning on and off Q2 to Q5 (S2
6). After starting switching on / off of the switching elements Q2 to Q5 or when the predetermined time has not elapsed, the process returns to the main loop.

In the interrupt process shown in FIG. 3B, the input voltage (power supply voltage) is read from the input voltage detection unit 9 (S21), and then the lamp current is read from the lamp current detection unit 7 (S22). A current error calculation between the lamp current command value and the lamp current is performed (S23), and the primary side current peak value is output based on the result of the current error calculation (S2).
4). Next, it is determined whether or not a predetermined time has elapsed (S2
5) If the predetermined time has passed, the switching elements Q2 to Q5 of the inverter circuit 3 are turned on / off so that the output voltage of the inverter circuit 3 becomes an alternating voltage of a rectangular wave (S26). After starting switching on / off of the switching elements Q2 to Q5 or when the predetermined time has not elapsed, the process returns to the main loop.

As can be seen from the above description, FIG.
The interrupt processing shown in FIG. 3 and the interrupt processing shown in FIG. 3B are different only in reading the lamp voltage or the input voltage in the first step (S21), and in the other steps (S22 to S26). The same, Figure 3
The time taken for the calculation in the interrupt processing shown in (a) and the time taken for the calculation in the interrupt processing shown in FIG. 3 (b) are the same.

By the way, assuming that the time required for one round of the main loop is T1, the interrupt interval is T2, and the time required for calculation in the interrupt process is T3, the control unit 8a in the present embodiment has a stable lighting state of the lamp La. In consideration of the fact that the lamp voltage is relatively stable compared to the lamp current, by setting T1> T2-T3, [frequency of calculation of lamp current command value by lamp voltage] <[current error calculation According to the present embodiment, the frequency of the primary current peak value is updated. However, in the present embodiment, feedback control is performed by performing a current error calculation that is an error calculation rather than a frequency of performing a calculation for obtaining a lamp current command value that is a load current command value. Is performed more frequently than before, without increasing the operation speed of the microcomputer used as the control unit 8a. Will be able to be accommodated quickly to changes in the current, it is possible to light the lamp La stable than conventional while suppressing an increase in cost.

Further, the control unit 8 outputs a control signal for turning on / off the switching elements Q2 to Q5 of the inverter circuit 3.
Since the signal is supplied from a through the drive circuit 5, the accuracy of the timing of controlling the inverter circuit is improved as compared with the case where the control signal of the inverter circuit 3 is supplied from a control circuit different from the control unit 8a. Since the control unit 8a can recognize the timing for controlling the switching elements Q2 to Q5 so that the inverter circuit 3 outputs the alternating voltage of the rectangular wave, it is easy to take a measure such as changing the control method.

Further, the constant power control by the current error calculation is greatly affected by the timing of the current error calculation, but in the present embodiment, since the primary side current peak value is updated by the current error calculation by the interrupt process, The current error calculation is repeated at a substantially constant timing, and it becomes possible to more stably turn on the lamp La.

In this embodiment, the primary current peak value is controlled, but PWM control by comparison with a triangular wave may be performed.

(Second Embodiment) The basic configuration of the discharge lamp lighting device of the present embodiment is the same as that of the first embodiment.
The operation will be different, and will be described with reference to the circuit diagram of FIG. By the way, although the lamp voltage of the lamp La is more stable than the lamp current in the stable period,
The fluctuation of the lamp voltage is large during the transitional period immediately after the lamp is turned on or when the luminous flux is started.

On the other hand, in this embodiment, the time T1 required for one round of the main loop and the interrupt interval T2 are set to T2-T3 = αT1 (0 <α ≦ 1) in the transition period, and set in the stable period. By setting T2−T3 = βT1 (0 <β ≦ 1) (where α> β), the lamp current due to the lamp voltage is more stable when the lamp voltage is unstable compared to the stable period when the lamp voltage is more stable. The command value is calculated more frequently.

The operation of the control section 8a in the present embodiment will be described below with reference to the flowchart of FIG. 4. However, except for the operation of the main loop described in the first embodiment, the operation similar to that of the first embodiment will be described. Briefly explained.

When the power is turned on, the microcomputer program starts and the switching elements Q2 to Q5 of the inverter circuit 3 are initialized (S1). After the initial setting of the inverter circuit 3, the initial setting on the microcomputer is performed (S2). After that, control is performed at the time of no load before lighting, and a no-load voltage is applied to the lamp La,
The lamp La is started by applying a starting pulse (for example, a voltage of 20 kV) to the lamp La from the starting device 4 (S3).

Then, it is judged whether or not the lamp La is turned on (S4), and if the lamp La is not turned on, no-load control is performed. On the other hand, when the lamp La is turned on, the lamp power command value is set (S5), then the lamp voltage is averaged (S6), and the lamp power command value is divided by the lamp voltage to perform the calculation. A command value is obtained (S7). Then, the state of the lamp La (lamp state)
Is stable (whether in a stable period or in a transitional period) (S8), and if the lamp La is stable, T2-T3 = βT1 is set. If the lamp La is not stable, Let T2-T3 = αT1. In addition, as a method of determining the lamp state, for example, determination based on the power of the lamp La,
The judgment based on the electric power command value of the lamp La, the judgment based on the elapsed time from the lighting of the lamp La (also taking into account the restart) may be appropriately adopted.

Then, it is judged whether the power supply voltage is within the standard range based on the voltage detected by the input voltage detecting unit 9 (S11). Judge whether to start (S1
3) If it is determined that the restart should be performed, the process returns to S1, and if it is determined that the restart should not be performed, the process is stopped. On the other hand, if the power supply voltage is within the specified range, it is determined whether or not the lamp La is on (S12), and if the lamp La is on, the process returns to S5. On the other hand, if the lamp La is not lit, it is determined whether or not the restart is required (S13),
If it is determined that the restart should be performed, the process returns to S1, and if it is determined that the restart should not be performed, the process is stopped.

As can be seen from the above description, the lamp La
While is lit, S described in the flowchart of FIG.
The main loop consisting of steps 5 to S12 is repeated, and during the repetition, the interrupt processing shown in FIG. 5 (a) and the interrupt processing shown in FIG. 5 (b) are alternated at a constant interrupt interval T2. It has become. Note that FIG.
The interrupt process shown in FIG. 3A is the same as the interrupt process shown in FIG. 3A, and the interrupt process shown in FIG. 5B is the same as the interrupt process shown in FIG.

By the way, among the time T1 required for one round of the main loop, the interrupt interval T2, and the time T3 required for calculation in the interrupt, the times T1 and T3 are fixed values, and only the interrupt interval T2 is variable. As can be seen from the description, in the present embodiment, the interrupt interval for updating the primary-side current peak value by the current error calculation is changed according to the lamp state determination result.

In the present embodiment, however, the frequency of calculation of the lamp current command value and the frequency of current error calculation are changed according to the state of the lamp La, which is the load, so that the transition period during which the lamp voltage is unstable and the lamp voltage are unstable. The frequency of calculation can be appropriately changed during the stable period when the voltage is relatively stable, and more stable lighting of the lamp La becomes possible.

In the present embodiment, the interrupt interval T2
However, the interrupt interval T2 may be changed in multiple steps.

By the way, the current error calculation (S23) in each of the interrupt processes of FIG. 5A may be performed, for example, in steps S23a to S23d of FIG. That is,
First, a value obtained by subtracting the read lamp current from the lamp current command value calculated in the main loop is set as a current error value (S23a), and a value obtained by integrating a value obtained by multiplying the current error value by the integral gain KI. Is the current error integral value (S23b). Then, the current error integrated value is determined as the primary side current command value (S23c), and the value obtained by adding the product of the current error value and the proportional gain KP to the primary side current command value is set as the final primary side current command value (S23d). ), And outputs this primary side current command value as a primary side current peak value (S24).

The current error calculation (S23) in the interrupt process of FIG. 5B described above may be performed in the same steps S23a to S23d.

In this embodiment, however, the control unit 8a performs proportional-integral control in the current-error calculation to perform proportional-integral control, so that proportional-integral control can be realized at regular time intervals and a quick response to the current error. And the precise output adjustment is possible, and the stable lighting of the lamp La is possible.

(Embodiment 3) The structure and basic operation of the discharge lamp lighting device of this embodiment are the same as those of Embodiment 2,
The current error calculation in interrupt processing differs from that of the second embodiment.

In the present embodiment, the current error calculation (S23) in the above-mentioned interrupt processing of FIG. 5A is performed in steps S23a to S23f of FIG. That is, first, a value obtained by subtracting the read lamp current from the lamp current command value calculated in the main loop is set as the current error value (S23a), and the current error value is integrated into the gain by the table shown in FIG. The integrated control value change amount multiplied by is read (S23b), and the value obtained by integrating the integrated control value change amount is set as the current error integrated value (S23c). Then, the integrated value of the current error is determined as the primary side current command value (S23
d), the proportional control value change amount obtained by multiplying the current error value by the proportional gain is read from the table as shown in FIG. 8B (S2).
3e), the value obtained by adding the proportional control value change amount to the primary side current command value is updated as the primary side current command value (S23f), and this primary side current command value is output as the primary side current peak value (S24).

In short, in the second embodiment, the change amounts of the control values due to the integral gain and the proportional gain are obtained by using the multiplication, whereas in the present embodiment, the table of FIG. 8A is used. 8B, the result (first result) of multiplying the current error value by the integral gain is obtained.
The result of multiplying the current error value by the proportional gain (second result) is obtained using the table of (1), the current error integral value is calculated using the first result (S23c), and the second result is used. The primary side current command value is updated (S23f).

Here, in the table of FIG. 8A, the integral gain is changed nonlinearly with respect to the current error value (the smaller the current error value, the smaller the integral gain, and the larger the current error value, the integral. The gain will increase)
Therefore, compared to the case where the integral gain is changed linearly,
The more stable it is, the smaller the control amount can be,
The stability can be increased. Further, in the table of FIG. 8B, when the current error value is smaller than the predetermined value, the proportional control value change amount is set to 0. Therefore, in the stable state, integral control is the main component to improve the stability of the stable state. be able to. Further, since the stability of the stable state can be ensured, the value of the proportional gain can be increased when the amount of deviation of the proportional control value is out of the region of 0, and when the power supply voltage momentarily drops, etc. High-speed response is possible in the abnormal state of. Also, the resolution of the proportional control value change amount can be reduced, and the calculation speed can be increased.

The current error calculation (S23) in the above-described interrupt processing of FIG. 5B may be performed in the same steps as steps S23a to S23f in FIG.

(Embodiment 4) The structure and basic operation of the discharge lamp lighting device of the present embodiment are the same as those of the third embodiment.
As shown in the flowchart of FIG. 9, step S23f of adding the proportional control value control value change amount to the primary side current command value by the proportional gain is not executed when the elapsed time after the lamp has started has not reached the predetermined time. The only difference is that they are doing so. Here, the predetermined time may be set to, for example, the time required for the luminous flux of the lamp La to rise (that is, the predetermined time may be set, for example, according to the rising time of the luminous flux of the lamp La).

By the way, when the luminous flux is turned on, the lamp current command value greatly changes due to the change of the lamp power command value, and the lamp current is not stable.
Flickering of a is undesirable. If the control unit 8a performs the proportional control at the time of raising the luminous flux, the lamp current may overshoot the target value of the lamp current, and the lamp La may not be stably started.

On the other hand, in the present embodiment, since the proportional control is not performed when the luminous flux is raised,
It is possible to improve the stability at the time of raising the luminous flux.

The current error calculation (S23) in the interrupt processing of FIG. 5B described above may be performed in the same steps.

By the way, the time for starting the luminous flux is the lamp L
Since it changes depending on the temperature of a, as a guide for checking the temperature of the lamp La, the elapsed time (extinguishing time) after the lamp La in the lit state is extinguished is measured by the time constant circuit of the capacitor and the resistance, and restarted. It's time. Then, by changing the predetermined time according to the restart time, it is possible to accurately know the end of the light flux startup, and more stable startup is possible.

Further, it is possible to judge whether the luminous flux is rising or stable by monitoring the output power of the DC-DC conversion circuit 2 instead of measuring the restart time.
Instead of step 23g in FIG. 9, step 23h for determining whether or not the lamp output power is equal to or lower than a predetermined power is provided as shown in FIG. 10, and when the lamp output power exceeds the predetermined power, when the luminous flux is raised. Therefore, even if the proportional control is not performed, it is possible to improve the stability at the time of raising the luminous flux.

In the present embodiment, when the proportional control is started, the magnitude of the proportional gain is changed from 0 to a predetermined value.
The value is raised, but it is better to raise it in multiple steps.

(Embodiment 5) The structure and basic operation of the discharge lamp lighting device of the present embodiment are the same as those of Embodiment 3,
In the interrupt processing according to the flowchart of FIG. 11,
A table as shown in FIG. 12A is used as a table of the integration control value change amount by the integration gain, and the integration control value change amount is limited by a predetermined limit value. That is, in the present embodiment, the integral control value change amount changes linearly with respect to the current error value until the integral control value change amount reaches the limit value, and when the current error value increases, the integral control value change amount increases. The amount is kept at the limit.

However, in this embodiment, when the current error value at the time of raising the luminous flux becomes relatively large, the integral control value change amount is limited by the limit value, and therefore the integral control value change amount becomes too large. It is possible to prevent the difficulty of stable and stable rising.

The current error calculation (S23) in the interrupt processing of FIG. 5B described above may be performed in the same steps.

(Embodiment 6) The structure and basic operation of the discharge lamp lighting device of this embodiment are the same as those of Embodiment 3,
The interrupt processing as shown in FIG. 13 and the interrupt processing as shown in FIG. 14 are performed alternately. Here, in the interrupt process of FIG. 14, when the input voltage is read in step 21, the value is saved, and when the input voltage is newly read, the read input voltage and the saved input voltage (input Voltage stored value) (S31),
When the absolute value of the difference between the two exceeds a predetermined voltage value, the flag A is turned on (S33), and when it does not exceed the predetermined voltage value, the flag A is turned off and the process proceeds to step S22. It is different from interrupt processing. Further, in both the interrupt processing of FIG. 13 and FIG. 14, after the primary side current command value is determined in step S23d, it is confirmed whether or not the flag A is turned on (S2
3i), if the flag A is turned on, FIG.
When the flag A is off, the proportional control value change amount is read using a table such as that shown in FIG.
The proportional control value change amount is read using the table as shown in (c) (S23e2). The operation after reading the proportional control value change amount is the same as in the third embodiment.

That is, in any interrupt process, the flag A is checked when performing proportional control, and when the flag A is on, the proportional control value change amount is calculated using the table as shown in FIG. Seek proportional control
When the flag A is not set, the proportional control value change amount is calculated using the table as shown in FIG. 15C to perform the proportional control. Here, the table of FIG. 15B and the table of FIG. 15C are set so that the former has a larger proportional gain. Further, once the flag A is turned on, it is held for a predetermined time and then turned off.

By the way, if the proportional gain is set in accordance with the response of the primary side current command value when the power supply voltage fluctuates such that the power supply voltage momentarily drops, the stability in the steady state deteriorates. Further, in consideration of stability in a steady state, there is a case where the lamp La flickers largely without responding when the power supply voltage fluctuates such that the power supply voltage momentarily drops, and the lamp La may be turned off (turned off). .

On the other hand, in the present embodiment, the value of the proportional gain can be increased only in a transient case such as a power supply voltage fluctuation in which the power supply voltage instantaneously drops. It is possible to satisfy both stability and transient response.

In this embodiment, the value of the proportional gain is set binary depending on the fluctuation of the input voltage, but the value of the proportional gain may be changed depending on the magnitude of the fluctuation of the input voltage. .

(Embodiment 7) The structure and basic operation of the discharge lamp lighting device of the present embodiment are the same as those of Embodiment 3,
The difference is that the interrupt process of FIG. 16 is performed instead of the interrupt process of FIG. 5A described in the third embodiment. Further, the interrupt processing of FIG. 5B is also similar to that of FIG. In the present embodiment, in the interrupt process of FIG. 16, a table as shown in FIG. 17A is used as a table of the integral control value change amount by the integral gain, and a table of the proportional control value change amount by the proportional gain is shown in FIG. ) Is characterized by using a table such as. That is,
In the present embodiment, the absolute value of the integral control value change amount differs depending on whether the current error value is positive or negative, and the absolute value of the integral control value change amount is larger when the current error value is positive than when it is negative. There is. Similarly, the absolute value of the proportional control value change amount differs depending on whether the current error value is positive or negative, and the absolute value of the proportional control value change amount is larger when the current error value is positive than when it is negative.

By the way, when the absolute values of the integrated value control value change amount and the proportional control value change amount do not differ depending on whether the current error value is positive or negative, the input voltage changes as shown in FIG. When the waveform on the left side sharply decreases, the lamp current sharply decreases as shown on the left side waveform in FIG. 18 (b), and the primary side current command value is proportional to the left side in FIG. 18 (c) due to the proportional control. It rises sharply as shown in the waveform. As a result, the lamp current recovers as shown in the waveform diagram on the left side of FIG. 18B, and when the lamp current command value is overshooted, the primary side current command value is suddenly reduced, and at this time the lamp current Discharge lamp L
There was a possibility that a could not be kept lit and turned off.

On the other hand, also in this embodiment, when the lamp current recovers as shown in the waveform diagram on the right side of FIG. 18B and the lamp current command value overshoots,
Although the primary side current command value decreases as in the waveform diagram on the right side of 8 (c), the gain (that is, the primary side current command value) used when the current error value is negative is the same in this embodiment. 18 is relatively small, it is possible to prevent the primary side current command value from dropping too much as shown in the waveform diagram on the right side of FIG.
Since it is possible to prevent the lamp current from dropping too much as shown in the waveform diagram on the right side of (b), it is possible to improve the lighting sustainability and stability when the power supply voltage drops momentarily. The broken line in FIG. 18C shows the change in the primary side current command value when the proportional control is not performed.

(Embodiment 8) The structure and basic operation of the discharge lamp lighting device of the present embodiment are the same as those of Embodiment 3,
As shown in FIG. 19, FIG. 5A described in the third embodiment.
In the same interrupt processing as the above, after the comparison control value change amount is read in S23e, it is determined whether or not the comparison control value change amount is equal to or more than a predetermined value (S23j). The proportional control value change amount at that time is stored (S23k), the stored proportional control value change amount is set as the proportional control value change amount (S23n), and the primary side current command value is changed (updated) (S23f). When the flag B is turned on, it is turned off after a predetermined time.

If the comparison control value change amount is less than the predetermined value, it is determined whether the flag B is on (S23).
m), if the flag B is on, the stored proportional control value change amount is set as the proportional control value change amount (S23n), and the primary side current command value is changed (updated) (S23f). On the other hand, when the flag B is off, the primary side current command value is changed (updated) (S23f). By performing such control, when the comparison control value change amount exceeds the predetermined value, the proportional control value change amount is held for a certain period of time. Note that in the present embodiment, a table as shown in FIG. 20A is used as a table of integral control value changes, and a table as shown in FIG. 20B is used as a table of proportional control value changes. These tables are the same as those described in the third embodiment. In addition, the interrupt processing of FIG. 5B described in the third embodiment is also illustrated in FIG.
The same processing as 9 is performed.

By the way, when such control is not performed, if the input voltage sharply decreases as shown in the waveform diagram on the left side of FIG. 21 (a) due to a momentary decrease of the power supply voltage, the lamp current of FIG. As shown in the waveform diagram on the left side of (b), the primary side current command value decreases sharply due to the proportional control, as shown in FIG.
As shown in the waveform diagram on the left side of 1 (c), it sharply rises. As a result, the lamp current recovers as shown in the waveform diagram on the left side of FIG. 21 (b), and when the lamp current command value is overshooted, the primary current command value works sharply,
At this time, there is a possibility that the lamp current will drop too much and the lamp La will not be able to maintain lighting and will be extinguished.

On the other hand, also in the present embodiment, when the lamp current is recovered as shown in the waveform diagram on the right side of FIG. 21B and the lamp current command value is overshot,
Although the primary side current command value decreases as in the waveform diagram on the right side of 1 (c), it is proportional in the present embodiment when the proportional control value change amount of the primary side current command value becomes equal to or larger than a predetermined value. Since the control value change amount is held for a predetermined period of time, FIG.
As shown in the waveform diagram on the right side of (b), the lamp current during that period settles down, and compared to the waveform diagram on the left side, it is possible to reduce the fall width of the lamp current and the probability that the lamp current falls sharply. It becomes possible to improve the lighting sustainability and stability when the power is momentarily lowered. In addition,
The broken line in FIG. 21C shows the change in the primary-side current command value when the proportional control is not performed.

(Ninth Embodiment) The configuration and basic operation of the discharge lamp lighting device of the present embodiment are the same as those of the third embodiment.
As shown in FIG. 22, FIG. 5A described in the third embodiment.
In the same interrupt processing as above, after the comparison control value change amount is read in S23e, it is determined whether or not the comparison control value change amount is equal to or more than a predetermined value (S23j). Is stored in the proportional control value change amount stored value (S23p), and the flag B is turned on (S23q). After that, it is determined whether the proportional control value change amount is larger than the proportional control value change amount stored value (S23r), and if the proportional control value change amount is larger, the process returns to S23p, and the proportional control value change amount If it is smaller, it is judged whether or not the stored value of proportional control value change amount is a positive value (S23s), and if it is a positive value, proportional control is performed using the stored value of proportional control value change amount. Performing (S23t), subtracting the predetermined change amount from the proportional control value change amount stored value (S23u), and outputting the primary side current command value (S24). On the other hand, if the proportional control value change amount stored value is a negative value, the flag B is turned off (S23).
o), proportional control is performed using the proportional control value change amount (S
23f), the primary side current command value is output as the primary side current peak value (S24).

If the proportional control value change amount is less than the predetermined value in S23j, it is determined whether or not the flag B is on (S23m), and if the flag B is on, S2.
3q, if the flag B is off, proceed to S23o. In the present embodiment, the table as shown in FIG. 23A is used as the table of the integral control value change amount, and the table as shown in FIG. 23B is used as the table of the proportional control value change amount. These tables are the same as those described in the third embodiment. Further, the same processing as that of FIG. 22 is performed for the interrupt processing of FIG. 5B described in the third embodiment.

By the way, when such control is not performed, if the input voltage sharply decreases as shown in the waveform on the left side of FIG. 24 (a) due to a momentary decrease of the power supply voltage, the lamp current of FIG. As shown in the waveform diagram on the left side of (b), the primary side current command value decreases sharply due to the proportional control, as shown in FIG.
As shown in the waveform diagram on the left side of FIG. As a result, the lamp current recovers as shown in the waveform diagram on the left side of FIG. 24 (b), and when the lamp current command value is overshooted, the primary current command value is suddenly decreased,
At this time, there is a possibility that the lamp current will drop too much and the lamp La will not be able to maintain lighting and will be extinguished.

On the other hand, also in the present embodiment, when the lamp current is recovered as shown in the waveform diagram on the right side of FIG. 24B and the lamp current command value is overshot,
The point that the primary side current command value decreases as in the waveform diagram on the right side of 4 (c) is the same, but in the present embodiment, when the proportional control value change amount of the primary side current command value becomes equal to or greater than a predetermined value, When the proportional control value change amount increases, it increases immediately,
When it becomes smaller, it does not become smaller immediately but decreases by a predetermined value. Therefore, the fluctuation (vibration) of the primary side current command value can be suppressed as shown in the waveform diagram on the right side of FIG. Since the fluctuation of the current can be suppressed, it becomes possible to improve the lighting sustainability and stability when the power supply voltage is momentarily lowered. Note that FIG.
The broken line in (c) shows the change in the primary side current command value when the proportional control is not performed.

[0091]

According to the first aspect of the invention, the output of the DC power source is converted from DC to DC by turning on / off the switching element.
DC-D with C-DC conversion circuit and discharge lamp as load
A load circuit to which power is supplied from the C conversion circuit, a load voltage detection unit that detects a load voltage, a load current detection unit that detects a load current, and a load current based on the load voltage detected by the load voltage detection unit. DC-DC conversion is performed by performing an operation for obtaining a command value, performing an error operation between the load current command value and the load current, and performing feedback control to turn on / off the switching element of the DC-DC conversion circuit according to the operation result of the error operation. A control circuit that adjusts the output of the circuit is provided, and the control circuit performs the error calculation and performs the feedback control more frequently than the calculation that calculates the load current command value. It becomes possible to respond to changes in the load current earlier than before without having to do so, and to keep the cost stable and light the discharge lamp more stably than before. That there is an effect that can be achieved.

According to a second aspect of the present invention, in the first aspect of the present invention, the control circuit changes the frequency of the above-mentioned two types of calculations according to the state of the load. However, there is an effect that the frequency of calculation can be appropriately changed in a stable period when the discharge lamp is relatively stable, and the discharge lamp can be more stably lit.

According to a third aspect of the present invention, in the first or second aspect of the invention, the control circuit performs the error calculation at a substantially constant time interval except at least the time when the load state is unstable. During a period in which the lamp voltage is relatively stable as compared with the current, it becomes possible to quickly respond to changes in the lamp current, and it is possible to more stably turn on the discharge lamp.

According to a fourth aspect of the present invention, in the first to third aspects of the invention, the control circuit performs the proportional / integral control in the error calculation, so that the proportional / integral control can be realized and the quick response to the current error can be realized. This has the effect of enabling precise output adjustment and stable lamp lighting.

According to a fifth aspect of the invention, in the fourth aspect of the invention, the control circuit nonlinearly changes at least one of the proportional gain and the integral gain with respect to the current error value in the proportional-plus-integral calculation. There is an effect that the stability in the stable state can be improved as compared with the case where both and are linearly changed.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the invention, the control circuit is configured such that after the discharge lamp is started, a predetermined time set according to the rising time of the luminous flux elapses. Since the proportional control is not performed, it is possible to prevent the lamp current from overshooting the target value in the state where the lamp current is not stable as when the luminous flux is raised, and it is possible to improve the stability when the luminous flux is raised. .

According to a seventh aspect of the present invention, in the fourth or fifth aspect of the invention, the control circuit is arranged so that after the discharge lamp is started, DC is applied.
When the output power of the DC conversion circuit is equal to or higher than a predetermined value set according to the power at the time of starting the luminous flux, proportional control is not performed. There is an effect that the overshoot of the current can be prevented and the stability at the time of raising the luminous flux can be improved.

According to an eighth aspect of the invention, in the invention of the sixth aspect, the control circuit gradually increases the proportional gain of the proportional control with time when the proportional control is started after a predetermined time has elapsed. There is an effect that the stability at startup can be further improved.

According to a ninth aspect of the present invention, in the fourth or fifth aspect of the invention, the control circuit is provided with a predetermined limit value for the amount of change of the integral control value by the integral gain with respect to the current error value. When the current error value at start-up is relatively large, the amount of change in the integral control value is limited by the limit value, so it is possible to prevent the amount of change in the integral control value from becoming too large and making stable startup difficult. The effect is that you can.

According to a tenth aspect of the present invention, in the invention according to the fourth or fifth aspect, the control circuit determines at least the proportional gain and the integral gain of the proportional-plus-integral calculation according to the fluctuation of the input voltage to the DC-DC conversion circuit. Change one, so
There is an effect that it is possible to improve both stability and transient response.

According to the invention of claim 11, in the invention of claim 4 or claim 5, the control circuit increases the output of the DC-DC conversion circuit with respect to at least one of the proportional gain and the integral gain in the proportional-plus-integral calculation. Since the gain value is set to a large value compared to the gain value to be lowered, it is possible to prevent the lamp current from dropping too much and increase the lighting sustainability and stability when the power supply voltage drops momentarily. The effect is that it can be done.

According to a twelfth aspect of the present invention, in the control circuit according to the fourth or fifth aspect of the present invention, the control circuit is configured so that the change amount of the proportional control value by the proportional gain with respect to the current error value is D
When the output of the C-DC conversion circuit is increased, the amount of change in the proportional control value is held for a predetermined time after the output is increased, so the lamp current settles down during the predetermined time, and the power supply voltage is momentarily increased. There is an effect that it is possible to increase the lighting maintenance ability and stability when it is lowered.

According to a thirteenth aspect of the present invention, in the control circuit according to the fourth or fifth aspect of the present invention, the control circuit is configured so that the change amount of the proportional control value by the proportional gain with respect to the current error value is equal to or more than a predetermined value.
When the output of the C-DC conversion circuit is increased, the amount of change in the proportional control value is decreased with a predetermined time constant, so that the lamp current oscillation can be suppressed, and when the power supply voltage instantaneously decreases. There is an effect that the lighting maintenance ability and stability of can be increased.

According to a fourteenth aspect of the invention, in the invention of the first to thirteenth aspects, since the control circuit is composed of at least a microcomputer, the discharge lamp lighting device as a whole can be downsized and the cost can be reduced. effective.

According to a fifteenth aspect of the present invention, there is provided an inverter circuit according to any one of the first to fourteenth aspects, wherein the output of the DC-DC conversion circuit is used as a power source to apply an alternating voltage to the load circuit, and the control circuit includes the inverter circuit. Since the signal for controlling is output, there is an effect that the accuracy of the timing for controlling the inverter circuit is improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is an operation explanatory diagram of the above.

FIG. 3 is an operation explanatory diagram of the above.

FIG. 4 is an operation explanatory diagram of the second embodiment.

FIG. 5 is an operation explanatory diagram of the above.

FIG. 6 is an operation explanatory diagram of the above.

FIG. 7 is an operation explanatory diagram of the third embodiment.

FIG. 8 is an operation explanatory diagram of the above.

FIG. 9 is an operation explanatory diagram of the fourth embodiment.

FIG. 10 is an explanatory diagram of another operation example of the above.

FIG. 11 is an operation explanatory diagram of the fifth embodiment.

FIG. 12 is an explanatory diagram of an operation of the above.

FIG. 13 is an operation explanatory diagram of the sixth embodiment.

FIG. 14 is an explanatory diagram of an operation of the above.

FIG. 15 is an operation explanatory diagram of the above.

FIG. 16 is an operation explanatory diagram of the seventh embodiment.

FIG. 17 is an explanatory diagram of the same operation as above.

FIG. 18 is an operation explanatory diagram of the above.

FIG. 19 is an operation explanatory diagram of the eighth embodiment.

FIG. 20 is an operation explanatory diagram of the above.

FIG. 21 is an operation explanatory diagram of the above.

FIG. 22 is an operation explanatory diagram of the ninth embodiment.

FIG. 23 is an explanatory diagram of the operation of the above.

FIG. 24 is an explanatory diagram of the operation of the above.

FIG. 25 is a circuit diagram showing a conventional example.

FIG. 26 is an explanatory diagram of an operation of the above.

FIG. 27 is an explanatory diagram of the operation of the above.

FIG. 28 is an explanatory diagram of the operation of the above.

[Explanation of symbols]

1 DC power supply 2 DC-DC conversion circuit 3 inverter circuit 4 Starter 5 drive circuit 6 Lamp voltage detector 7 Lamp current detector 8 control circuit 8a control unit 9 Input voltage detector 11 comparator 12 RS flip-flops La lamp

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miki Otani             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company (72) Inventor Takashi Kambara             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F term (reference) 3K072 AA13 AC01 AC11 BA05 BC05                       DD06 DE02 DE04 DE06 GA03                       GB18 GC04 HA10 HB03

Claims (15)

[Claims] 1. A DC-DC converter circuit for converting the output of a DC power supply into a DC-DC converter by turning on / off a switching element, a load circuit having a discharge lamp as a load and being supplied with power from the DC-DC converter circuit, and a load. Load voltage detection means for detecting the voltage, load current detection means for detecting the load current, and calculation for obtaining the load current command value based on the load voltage detected by the load voltage detection means. And a control circuit that adjusts the output of the DC-DC conversion circuit by performing feedback control of ON / OFF of the switching element of the DC-DC conversion circuit according to the calculation result of the error calculation. Is
A discharge lamp lighting device characterized in that an error calculation is performed and feedback control is performed more frequently than a load current command value is calculated. 2. The control circuit according to the load condition,
The discharge lamp lighting device according to claim 1, wherein the frequency of the type of calculation is changed. 3. The discharge lamp lighting device according to claim 1, wherein the control circuit performs the error calculation at substantially constant time intervals except at least when the load state is unstable. 4. The control circuit performs proportional / integral control in error calculation.
The discharge lamp lighting device according to any one of 1. 5. The discharge lamp lighting device according to claim 4, wherein the control circuit nonlinearly changes at least one of the proportional gain and the integral gain with respect to the current error value in the proportional-plus-integral calculation. 6. The control circuit does not perform proportional control until the predetermined time set according to the rising time of the luminous flux elapses after the discharge lamp is started.
Alternatively, the discharge lamp lighting device according to claim 5. 7. The control circuit, after starting the discharge lamp, DC-D
6. The discharge lamp lighting device according to claim 4, wherein the proportional control is not performed when the output power of the C conversion circuit is equal to or more than a predetermined value set according to the power when the light flux is raised. 8. The discharge lamp lighting device according to claim 6, wherein the control circuit gradually increases the proportional gain of the proportional control with time when the proportional control is started after a predetermined time has elapsed. 9. The discharge lamp lighting device according to claim 4, wherein the control circuit is provided with a predetermined limit value for the amount of change of the integral control value by the integral gain with respect to the current error value. 10. The control circuit changes at least one of a proportional gain and an integral gain of the proportional-plus-integral calculation according to a change in an input voltage to the DC-DC conversion circuit. The discharge lamp lighting device described. 11. The control circuit relates to at least one of a proportional gain and an integral gain in a proportional-plus-integral calculation, D
The discharge lamp lighting device according to claim 4 or 5, wherein a gain value for increasing the output of the C-DC conversion circuit is set to a larger value than a gain value for decreasing the output. 12. The control circuit, when the amount of change in the proportional control value due to the proportional gain with respect to the current error value is a predetermined value or more, DC-
The discharge lamp lighting device according to claim 4 or 5, wherein when the output of the DC conversion circuit is increased, the amount of change in the proportional control value is held for a predetermined time after the output is increased. 13. The control circuit, when the amount of change in the proportional control value due to the proportional gain with respect to the current error value is a predetermined value or more
The discharge lamp lighting device according to claim 4 or 5, wherein when the output of the DC conversion circuit is increased, the amount of change in the proportional control value is decreased with a predetermined time constant. 14. The discharge lamp lighting device according to claim 1, wherein the control circuit includes at least a microcomputer. 15. An inverter circuit for applying an alternating voltage to a load circuit using the output of the DC-DC conversion circuit as a power source,
The discharge lamp lighting device according to any one of claims 1 to 14, wherein the control circuit outputs a signal for controlling the inverter circuit.