JPH11144887A - Electronic ballast device for high pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering of brightness in a lamp even when a rated operation point is fluctuated by dispersion in manufacturing, change with the lapse of time, or the like by pulse-width-controlling operation of a switching element based on a signal provided from a comparison means. SOLUTION: Information on lamp voltage of a high pressure discharge lamp 9 is supplied to an A/D converter 55a by a voltage dividing circuit 25, and information on lamp current is supplied to an A/D converter 55b by a current detecting resistance 26. A digital multiplier 56 multiplys two kinds of digital signals output from the A/D converters 55a, 55b together to feed the multiplied result to a comparator 58. The comparator 58 compares the result with a power data stored in a data table 57 to feed a signal to a PWM controller 59 so as to realize a prescribed fixed power characteristic. The PWM controller 59 generates a pulse of a duty ratio with response to the signal from the comparator 58 to drive a base of a switching element 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic ballast for lighting a high-pressure discharge lamp such as a metal halide lamp at a constant power.

[0002]

2. Description of the Related Art FIG. 6 shows a circuit configuration of a conventional high pressure discharge lamp lighting device. This device is compatible with
No. 572, which is intended to stabilize the input from the DC power supply 1 by the switching regulator 20 and supply the stabilized power to the high-pressure discharge lamp 9 for constant power lighting.

The switching regulator 20 includes a switching transistor 21 as a switching element for turning on and off a current from the DC power supply 1 and outputting the same, a diode 22 for smoothing an output current of the switching transistor 21, an inductor 23, and a capacitor. 24,
A voltage dividing circuit 250 as lamp voltage detecting means for dividing the lamp voltage VL into 1 / N for detection, a resistor 260 (resistance value r) as lamp current detecting means for detecting lamp current IL, a reference voltage source 27, Output voltage VL of voltage circuit 250
/ N and the sum VL / N + of the voltage r · IL between the terminals of the resistor 260
r · IL is compared with the output voltage Vref of the reference voltage source 27,
Error amplifier 2 as comparison means for outputting the difference voltage
8. A PWM controller 29 that generates a pulse having a duty ratio according to the output of the error amplifier 28 to drive the switching transistor 21 is provided.

The switching transistor 21 has a PWM
Driven by the pulse output of the controller 29, the current from the DC power supply 1 to the high-pressure discharge lamp 9 is turned on / off. When the transistor 21 is on, the inductor 21 supplies the high-pressure discharge lamp 9 while limiting the on-current and stores electromagnetic energy. When the transistor 21 is off, the inductor 23, the high-pressure discharge lamp 9 and the diode Maintain the closed circuit current including 22.

Thus, the high-pressure discharge lamp 9 is supplied with the lamp current IL which is limited by the transistor 21 and the inductor 23 and smoothed by the diode 22, the inductor 23 and the capacitor 24.

The voltage dividing circuit 250 includes voltage dividing resistors 250a,
The lamp voltage VL of the high-pressure discharge lamp 9 is divided into 1 / N and supplied to the non-inverting input terminal of the error amplifier 28. On the other hand, a reference voltage Vref from the reference voltage source 27 is supplied to an inverting input terminal of the error amplifier 28.

The load terminal D of the high-pressure discharge lamp 9
And the reference current C between the reference voltage source 27 and the lamp current IL.
Is connected, the load terminal of the high-pressure discharge lamp 9, that is, the reference point D of the voltage dividing circuit is biased by r · IL with respect to the reference point C of the reference voltage source 27. Become. That is, based on the point C, the voltage VL / N + r · IL is applied to the non-inverting input terminal of the error amplifier 28.
Is applied, and the reference voltage Vref is applied to the inverting input terminal. Therefore, the error amplifier 28 outputs Vref
An error voltage of-(VL / N + r.IL) is output.

[0008] The PWM controller 29 generates a pulse having a duty ratio according to the error voltage, and drives the base of the transistor 21.

[0009] Thus, the VL /
The lamp voltage VL and the lamp current IL satisfying N + r · IL = Vref are supplied, and PL = VL · IL = VL (Vref−VL / N)
/ R is supplied. This operation characteristic is shown by a solid line in FIGS. FIG. 7 shows the lamp current IL vs. lamp voltage VL characteristics, and FIG. 8 shows the lamp power PL vs. lamp voltage VL characteristics.

Here, the voltage dividing ratio N by the voltage dividing circuit 250,
The resistance value r of the current detection resistor 260 and the reference voltage Vref from the reference voltage source 27 are the rated operating points (VL) of the high-pressure discharge lamp 9.
S, ILS) so that the lamp power PL becomes the maximum PLS, that is, VLS is equal to the lamp open voltage Vo (= NVref).
Of the lamp short-circuit current Is (= Vref / r).

However, in such a circuit system, when the rated operating point of the high-pressure discharge lamp 9 fluctuates due to manufacturing variations, aging, etc., the lamp power does not exceed the rating, which is safe. A change (decrease) results in a change (decrease) in lamp brightness.

On the other hand, in the circuit configuration of FIG. 6, a Zener diode 30 as a correction means is connected to the voltage dividing circuit 250, and the voltage when the lamp voltage VL exceeds a predetermined value (the Zener voltage VZ of the Zener diode 30). The pressure ratio N is increased non-linearly.

As can be seen from FIG. 7, the voltage immediately before the start of the high-pressure discharge lamp, that is, the lamp open voltage Vo is equal to the rated voltage of 2 without the zener diode 30.
Since it reaches only twice (approximately 80 V), it is corrected to obtain a desired lamp starting voltage (approximately 400 V).
By this correction, the lamp starting voltage is changed from Vo in FIG.
To be increased.

However, the lamp power characteristic at this time becomes a characteristic shown by a broken line in FIG. 8, and when the lamp impedance becomes large, the power becomes excessively large, which is very dangerous.

Further, in the conventional method, even if the lamps have the same power, if the rated operating points are different, the lamps cannot be used as they are, and the voltage dividing circuit 250, the current detecting resistor 260, the reference The design of the voltage source 27 and the Zener diode 30 as correction means of the voltage dividing circuit 250 must be changed, and the versatility is poor.

[0016]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention reduces the brightness of a high-pressure discharge lamp even if the rated operating point fluctuates due to manufacturing variations or aging. It is another object of the present invention to provide an electronic ballast for a high-pressure discharge lamp that can be used for lamps having significantly different rated operating points without design change if the rated power is the same.

[0017]

An electronic ballast device for a high-pressure discharge lamp according to the present invention is provided between a DC power supply and a high-pressure discharge lamp, and controls the operation of a switching element by pulse width to control the high-pressure discharge lamp. In an electronic ballast device for a high-pressure discharge lamp for lighting at a constant power, a lamp voltage detecting means for detecting a lamp voltage signal according to a lamp voltage of the high-pressure discharge lamp, a means for digitizing the lamp voltage signal, and a lamp for the high-pressure discharge lamp Lamp current detecting means for detecting a lamp current signal corresponding to a current; means for digitizing the lamp current signal; and multiplying means for multiplying the digitized lamp voltage signal and the digitized lamp current signal. And a data table in which data to be compared with the result of the multiplication is recorded. A comparison unit that compares the data recorded in the data table with a pulse width control unit that performs pulse width control on the operation of the switching element based on a signal obtained from the comparison unit. More preferably, in the data table, data to be compared with the digitized lamp voltage signal and the digitized lamp current signal are recorded, and the comparing unit includes the digitized lamp voltage. And a function of comparing the signal and the digitized lamp current signal with data recorded in the data table.

[0018]

FIG. 1 shows a circuit configuration of an electronic ballast device for a high-pressure discharge lamp according to an embodiment of the present invention.

This device stabilizes an input from a DC power supply 1 by a switching regulator 2 and supplies it to a high-pressure discharge lamp 9 so that the high-pressure discharge lamp 9 is turned on at a constant power.

The switching regulator 2 controls the output of the switching transistor 21 based on the data recorded in the data table 57 by pulse width control (PW
M control).

The data recorded in the data table 57 is operating characteristic data as shown in FIG. 2 and FIG. 3, and has a constant power characteristic with an upper limit of voltage and an upper limit of current.

The switching regulator 2 includes a switching transistor 21 as a switching element for turning on and off a current from the DC power supply 1 and outputting the same, a diode 22 for smoothing an output current of the switching transistor 21, an inductor 23, and a capacitor 24. A voltage dividing circuit 25 as a lamp voltage detecting means for detecting the lamp voltage VL by dividing it by 1 / N, a resistor 26 (resistance value r) as a lamp current detecting means for detecting the lamp current IL, and a voltage dividing circuit 25. A / D converters 55a and 55b for converting the obtained lamp voltage signal and the lamp current signal obtained from the current detection resistor 25 into digital signals, respectively, and digital multiplication for multiplying the digitized lamp voltage signal and the lamp current signal. Unit 56, the data to be compared with the result of the multiplication are recorded Tateburu 57, PWM of the pulse width control the operation of the comparator 58, the switching element based on a signal obtained from the comparator 58 for comparing the recorded data on the results and the data table of the multiplication
A controller 59 is provided.

The switching transistor 21 is a PWM
Driven by the pulse output of the controller 59, the current from the DC power supply 1 to the high-pressure discharge lamp 9 is turned on / off. When the transistor 21 is on, the inductor 21 supplies the high-pressure discharge lamp 9 while limiting the on-current and stores electromagnetic energy. When the transistor 21 is off, the inductor 23, the high-pressure discharge lamp 9 and the diode 22 is maintained.

Thus, the current which is limited by the transistor 21 and the inductor 23 and smoothed by the diode 22, the inductor 23 and the capacitor 24 is supplied to the high-pressure discharge lamp 9.

Information on the lamp voltage VL of the high-pressure discharge lamp 9 is divided into 1 / N by a
It is supplied to the D converter 55a. On the other hand, information on the lamp current IL is supplied to the voltage r by the current detection resistor 26 connected between the load terminal B of the high-pressure discharge lamp 9 and the reference point A.
-It is supplied to the A / D converter 55b as IL.

The digital multiplier 28 includes an A / D converter 55
a, and 55 b are multiplied by each other, and the result of the multiplication is supplied to a comparator 58.

The comparator 58 compares the result of the multiplication supplied from the digital multiplier 58 with the power data recorded in the data table 57, and implements a constant power characteristic as shown in FIGS. A signal is sent to the PWM controller 59.

Further, the comparator 58 includes an A / D converter 55a,
The two types of digital signals supplied directly from 55b without passing through the multiplier 58 are compared with the voltage data and the current data recorded in the data table 57, and the upper limit VLM of the lamp voltage VL and the upper limit IVLM of the lamp current IL are compared. Is sent to the PWM controller 59.

The PWM controller 59 generates a pulse having a duty ratio according to the signal from the comparator 58, and drives the base of the transistor 21.

[0030]

According to the present invention, even if the rated operating point of the high-pressure discharge lamp fluctuates due to manufacturing variations, aging, etc., the lamp power is always constant and the brightness of the lamp does not decrease.

Further, according to the present invention, lamps having greatly different rated operating points can be used as they are without design change if the rated power is the same. For example, 250W
Lamps with an operating point of 50 V × 5 A and 1
In the case where there is one of 00V × 2.5A, in the conventional method,
Although two types of electronic ballast devices were required as shown by a solid line and a broken line in FIGS. 9 and 10, according to the present invention, FIG.
5, and can be used with one type of electronic ballast device as indicated by dots.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram illustrating operating characteristics (lamp current vs. lamp voltage characteristics) of an electronic ballast for a high-pressure discharge lamp according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram relating to operating characteristics (lamp power vs. lamp voltage characteristics) of an electronic ballast for a high pressure discharge lamp according to an embodiment of the present invention.

FIG. 4 is an operation characteristic diagram (lamp current vs. lamp voltage characteristic diagram) of the electronic ballast device for a high pressure discharge lamp according to the embodiment of the present invention.

FIG. 5 is an operation characteristic diagram (lamp power vs. lamp voltage characteristic diagram) of the electronic ballast device for a high pressure discharge lamp according to the embodiment of the present invention.

FIG. 6 is a circuit configuration diagram of an electronic ballast device for a high-pressure discharge lamp according to a conventional example.

FIG. 7 is a conceptual diagram relating to operating characteristics (lamp current vs. lamp voltage characteristics) of a conventional high-pressure discharge lamp electronic ballast device.

FIG. 8 is a conceptual diagram relating to an operation characteristic (lamp power vs. lamp voltage characteristic) of an electronic ballast device for a high-pressure discharge lamp according to a conventional example.

FIG. 9 is an operational characteristic diagram (lamp current vs. lamp voltage characteristic diagram) of an electronic ballast device for a high-pressure discharge lamp according to a conventional example.

FIG. 10 is an operation characteristic diagram (lamp power vs. lamp voltage characteristic diagram) of an electronic ballast device for a high-pressure discharge lamp according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Switching regulator 21 Switching element 22 Diode 23 Inductor 24 Capacitor 25 Voltage dividing circuit 26 Current detection resistor 55a A / D converter 55b A / D converter 56 Digital multiplier 57 Data table 58 Comparator 59 PWM controller 9 High pressure discharge lamp

Claims (2)

[Claims] An electronic ballast device for a high-pressure discharge lamp interposed between a DC power supply and a high-pressure discharge lamp and controlling the operation of a switching element with a pulse width to light the high-pressure discharge lamp at a constant power. Lamp voltage detecting means for detecting a lamp voltage signal corresponding to the lamp voltage of the lamp; means for digitizing the lamp voltage signal; lamp current detecting means for detecting a lamp current signal corresponding to the lamp current of the high-pressure discharge lamp; Means for digitizing the lamp current signal; multiplication means for multiplying the digitized lamp voltage signal by the digitized lamp current signal; and data to be compared with the result of the multiplication recorded. A data table, and comparison means for comparing the result of the multiplication with data recorded in the data table; Serial high-pressure discharge lamp electronic ballast, characterized in that it comprises a pulse width control means for controlling pulse width operation of the switching element based on a signal obtained from the comparison means. 2. The data table stores data to be compared with the digitized lamp voltage signal and the digitized lamp current signal, and wherein the comparing means includes the digitized lamp voltage signal. The electronic ballast device for a high-pressure discharge lamp according to claim 1, further comprising a function of comparing a signal and the digitized lamp current signal with data recorded in the data table.