JP2995373B2 - Control method of power supply for metal halide lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a power supply device used for lighting a metal halide lamp.

[0002]

2. Description of the Related Art Conventionally, a metal halide lamp is formed by enclosing a metal halide in a lamp tube, and is characterized in that when the enclosed metal is vaporized, the pressure in the tube increases to emit light of high brightness. However, since a light color close to daylight can be obtained by adjusting the encapsulation metal, it is used as various light sources such as a projection light source of an overhead projector (OHP).

In this type of metal halide lamp, when the lamp is turned on by DC power supply, the vaporized metal in the tube is ionized positively (+) and attracted to the negative electrode, and halogen is ionized negatively (-) to the positive electrode. Attracted to. If used in this state for several tens to several hundred hours, the metal ions adhere only to the negative electrode, deteriorating the light color and accuracy, and furthermore, the positive electrode is consumed by halogen and the lamp life is shortened.

Therefore, a power supply device for a metal halide lamp is conventionally formed by an AC power supply type power supply device as shown in FIG. AC power is received at an input terminal 1, rectified by a diode rectifier 2, converted to a DC power by a smoothing capacitor 3, and then converted to a DC power.
High frequency switching is performed by a chopper 31 composed of a switching element 32 such as an ET and a transistor, and is smoothed by a free wheel diode 45 and a smoothing reactor 43, and is supplied to an inverter circuit 34 of switching elements 35 to 38 such as a transistor, a MOSFET, and an IGBT. Is done.

The inverter circuit 34 includes a pair of switching elements 35, 38 and 36 by a low frequency driving circuit 51.
And 37 are reversely driven at about 50 to 250 Hz to perform switching driving to generate a rectangular wave AC for lighting connection between a connection point of the switching elements 35 and 37 and a connection point of the switching elements 36 and 38. It is supplied to the lamp 15 via the harmonic bypass capacitor 44 and the starter 21.

When the lamp 15 is discharged by the high frequency and high voltage of the starter 21, a current flows through a current detector 46 provided on the input side of the inverter circuit 34, and a detection signal detected by the current detector 46 is sent to an error amplifier 48. Is entered. The detection signal detected by the voltage detector 47 provided on the input side of the inverter 34 is input to the error amplifier 48.

The output control function of the error amplifier 48 adds and combines the voltage detection signal and the current detection signal to form a power detection signal, and an error signal between the detector and the reference signal of the reference power supply 49 is formed. This error signal is input to the chopper drive circuit 50 as an output control signal, the chopper operation of the switching element 32 is controlled, and the power supplied to the lamp 15 is controlled to a constant power based on the reference signal.

At this time, the DC current of the lamp 15 is a rectangular wave AC, and the change in the absolute value of the DC power supply is reduced in the rectangular wave AC, and lighting with little light ripple is obtained.

After the lamp 15 is turned on, the starter 21
To stop.

However, in the power supply device shown in FIG. 4, the chopper 31 for high-frequency switching and output control and the low-frequency inverter circuit 34 must be provided.

In order to simplify the configuration, there is a power supply device for performing high-frequency control and low-frequency control on an inverter circuit having a full bridge configuration of switching elements as shown in FIG. That is, an AC power supply is received at an input terminal 1, rectified by a rectifier 2 of a diode, converted to a DC power supply by smoothing a smoothing capacitor 3, and then converted to an IGBT, a MOSF.
It is supplied to an inverter circuit 4 composed of switching elements 5 to 8 such as ETs and transistors, and diodes 9 to 12 connected in antiparallel with the switching elements 5 to 8.

The inverter circuit 4 is PWM-controlled by an inverter drive circuit 20. That is, the switching elements 5, 8, 6, and 7 are respectively provided in FIGS.
Are input to drive the switching elements 5 to 8 for switching. The output of the inverter circuit 4 is smoothed by the smoothing reactor 13, and a rectangular wave AC is supplied to the lamp 15 via the harmonic bypass capacitor 14 and the starter 21.

[0013] When the lamp 15 is discharged with a high frequency high voltage of the starter 21, the inverter circuit current flows through the current detector 16 provided on the output side of the 4, the current detector 16 detects the signal error amplifier 18 detected by Is input to
Further, the output voltage is detected by the voltage detector 17, and the detected signal is input to the error amplifier 18.

The output control function of the error amplifier 18 adds and combines the voltage detection signal and the current detection signal to form a power detection signal, and an error signal between the detection signal and the reference signal of the reference power supply 19 is formed. The switching signals 5 to 8 are PWM-controlled by the inverter driving circuit 20 using the error signal as an output control signal, and the power supplied to the lamp 15 is controlled to a constant power based on the reference signal.

After the lamp 15 is turned on, the starter 21 is stopped.

[0016]

The switching elements 5, 8, 6, and 7 of the inverter circuit 4 are respectively provided in FIG.
Drive signals as shown in (a) to (d) are input. That is, the switching elements 7 and 8 have 50 to 250 Hz.
While the switching is performed at a low frequency, the switching elements 5 and 6 are switched at a high frequency of, for example, 10 kHz or more. Therefore, the switching elements 5, 6
The loss at the time of switching becomes large, the deterioration of the switching elements 5 and 6 is accelerated, and the switching elements 5 and 6 are damaged.
Therefore, the switching frequency of the switching elements 5 and 6 cannot be made higher than expected, and there is a limit in reducing the size of the power supply device.

[0017]

According to the present invention, a DC power supply in which an AC power supply is rectified is input, and a series circuit of a first switching element 5 and a second switching element 7;
And a series circuit of a fourth switching element 8 and a series circuit of the fourth switching element 8 are provided in parallel, and a connection point between the first switching element 5 and the second switching element 7 and a third switching element 6 and a fourth switching element The inverter circuit 4 outputs a high-frequency AC output from a connection point with the switching element 8 and outputs a high-frequency AC, a smoothing reactor 13 for smoothing the high-frequency AC, and drives the first to fourth switching elements. A method for controlling a metal halide lamp power supply device comprising an inverter drive circuit 20 comprising : a first switching element 5 and a fourth switching element 8 which face each other every half cycle of a low frequency; Third switching element 6 and second switching element 7
During the ON period of one of the first or third switching elements 5 or 6, the other fourth or second switching element 8 or 7 is turned on, off, or on, and the other fourth or second switching element 8 or 7 is controlled. During the ON period of the switching element 8 or 7, the first or third switching element 5 or 6 is controlled to be turned on, off, or on.

[0018]

According to the present invention, an inverter circuit which forms a full bridge by the first to fourth switching elements has a low frequency.
During the ON period of one of the first and fourth switching elements, or one of the third and second switching elements, which faces each other every half cycle of the wave , the other fourth element Alternatively, the second switching element is on, off, and on controlled, and the first or third switching element is on, off, and on during the on period of the other fourth or second switching element. In addition, switching is performed in which the opposing switching elements are balanced.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. One of the power supply devices used in the control method of the power supply device for a metal halide lamp according to the present invention is a power supply device shown in FIG. The difference from the power supply device shown in FIG. 2 is that the first switching element 5 and the fourth switch
Switching element 8, the third switching element 6, and the second switching element.
The difference lies in that the drive signal input to the chin element 7 is changed to the drive signal shown in FIG.

That is, at time t1, the first and fourth switching elements 5 and 8 of the inverter circuit 4 are opposed to each other.
Input the drive signals shown in FIGS. 1A and 1B, respectively.
When both the switching elements 5 and 8 are turned on, current flows through the first switching element 5, the reactor 13, the starter 21, the lamp 15, the current detector 16, and the fourth switching element 8. At this time, the electromagnetic energy is stored in the reactor 13.

Next, at time t2, the drive signal for the fourth switching element 8 is turned off. The electromagnetic energy of the reactor 13 is released via the reactor 13, the starter 21, the lamp 15, the voltage detector 16, the die auto 10, and the first switching element 5, and the current continuously flows through this route.

At time t3, when the drive signal for the fourth switching element 8 is input and turned on as shown in FIG. 1B, the first switching element 5, the reactor 13, the starter 21, A current flows through the lamp 15, the voltage detector 16, and the fourth switching element 8. At this time, electromagnetic energy is stored in the reactor 13.

At time t4, the drive signal for the first switching element 5 is turned off as shown in FIG.
Thereby, the electromagnetic energy of the reactor 13 is changed to the reactor 13, the starter 21, the lamp 15, the voltage detector 16,
The light is emitted through the fourth switching element 8 and the diode 11, and the current continuously flows through this route.

[0024] In the next time t5, enter the drive signal of the first switching element 5 as shown in FIG. 1 (a),
Turn on. Hereinafter, the control is sequentially repeated with times t1 to t5 as one cycle T1. Then, an output voltage shown in FIG. 1E is generated at the output of the inverter circuit 4.

Then, at time t6, the drive signals of the first and fourth switching elements 5 and 8 are turned off, and after providing a slight pause, the third and second switching elements 6 and 8 are turned off.
7 are input to the driving signals shown in FIGS. 1C and 1D, respectively , and the operations of the third and second switchings 6 and 7 are described above .
Operations similar to those of the first and fourth switching elements 5 and 8 are performed. Then, after turning off the third and second switching elements 6 and 7 from the time t1 , the period T2 from the time t7 when the first and fourth switching elements 5 and 8 are turned off is set to a low frequency of 50 to 50.
The inverter 4 is driven as one cycle of 250 Hz.

The power detection signal is formed by adding and combining the current detection signal detected by the current detector 16 and the current detection signal detected by the voltage detector 17, and the detected signal and the reference signal are converted by the error amplifier 18. The error is amplified by the switching elements 5 to 8 via the inverter drive circuit 20.
At this time, constant power is controlled by controlling the period in charge from time t2 to t3 and the period in charge from time t4 to t5.

[0027]

According to the present invention, as described above, the low frequency
Since the opposing switching elements are switched in a balanced manner every half cycle, the switching loss of each switching element is balanced. Compared with the conventional control method in which only one switching element performs high-frequency switching, the control frequency is halved, the frequency of the power supply device can be increased, and the power supply device can be downsized.

[Brief description of the drawings]

FIG. 1 is a timing chart for explaining an operation according to a control method of a metal halide power supply device of the present invention.

FIG. 2 is a wiring diagram of a power supply device for a metal halide lamp applied to the control method of the power supply device for a metal halide according to the present invention.

3 (a) to 3 (d) are timing charts for explaining an operation according to a conventional control method of a metal halide power supply device.

FIG. 4 is a connection diagram of a conventional power supply device for a metal halide lamp.

[Description of Signs] 4 Inverter circuit 5 (First) switching element 6 (Third) switching element 7 (Second) switching element 8 (Fourth) switching element 9 to 12 Diode 13 Smoothing reactor 15 Metal halide Lamp 16 Current detector 17 Voltage detector 18 Error amplifier 19 Reference power supply 20 Inverter drive circuit 21 Starter

──────────────────────────────────────────────────続 き Continued on the front page Examiner Nobuyuki Seki (56) References JP-A-4-138694 (JP, A) JP-A 2-79396 (JP, A) (58) Fields investigated (Int. Cl. ⁶⁾ , DB name) H05B 41/14-41/29 H02M 7/48 H02M 7/5387

Claims (1)

(57) [Claims] An AC power supply receives a rectified DC power supply, and supplies a series circuit of a first switching element and a second switching element, a third switching element and a fourth switching element.
And a series circuit with the switching element 8 is provided in parallel, and a connection point between the first switching element 5 and the second switching element 7 and a connection between the third switching element 6 and the fourth switching element 8 are provided. An inverter circuit 4 configured to output a high-frequency alternating current, which is output from a point and is a full bridge, a smoothing reactor 13 for smoothing the high-frequency alternating current,
In the control method of the power supply device for a metal halide lamp constituted by the inverter driving circuit 20 for driving the first to fourth switching elements, the low-frequency half power supply device may be used.
A first switching element 5 facing each cycle 4
Switching element 8 or third switching element 6
During the ON period of one of the first or third switching elements 5 or 6 of the second switching element 7, the other fourth or second switching element 8 or 7 is controlled to be on, off, or on, and the other A method for controlling a power supply device for a metal halide lamp in which the first or third switching element 5 or 6 is controlled to be turned on, off and on during the on period of the fourth or second switching element 8 or 7.