JPH0817572B2 - High pressure discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a high pressure discharge lamp lighting device for lighting a high pressure discharge lamp at a constant power.

(Prior art) Conventionally, when a constant power supply is configured using a switching regulator that stabilizes the output amount (voltage, current, power, etc.) by controlling the pulse width of the output current (PWM control), the load voltage And the current are detected, these are input to the multiplier and the voltage proportional to the power is obtained.
It was performing PWM control. For this reason, the circuit becomes complicated, and an expensive multiplier (for example, an IC) must be used, and the device becomes expensive.

In order to solve the above-mentioned inconvenience, as shown in FIG. 3, Japanese Patent Publication No. 62-2343 discloses a high-pressure discharge lamp lighting device for lighting a high-voltage discharge lamp 31 by an alternating current output of an alternating-current power supply 30. Transformer from the AC circuit
The lamp voltage and the lamp current converted into a voltage are detected by the voltage dividing circuits 32 and 33 and the voltage dividing circuits 34 and 35, and those values are input to the comparison circuit 36, respectively, and the input current value becomes the input voltage value. Control the triac 37 to be proportional,
A technique for controlling the high-pressure discharge lamp 31 at a constant power is disclosed.

(Problems to be Solved by the Invention) However, according to the technique of Japanese Patent Publication No. 62-2343, the comparison circuit inputs the current value and the voltage value, respectively, and compares the input current value with the input voltage value. Since the control signal is generated so that the input current value is proportional to the input voltage value, the configuration of the comparison circuit becomes complicated. Also, since the lamp voltage and the lamp current converted into the voltage are detected from the AC circuit of the lighting device, a special transformer such as a transformer or a rectifier is required, which complicates the circuit configuration and is unnecessary. There is a problem of large size. Also,
Generally, a high voltage is required at the time of starting the high pressure discharge high pressure discharge lamp. With this, the output to the high pressure discharge lamp is constantly controlled based on the lamp voltage of the high pressure discharge lamp and the lamp voltage. Therefore, at the time of starting the high-pressure discharge lamp, the lamp voltage does not flow to the high-pressure discharge lamp, so the lamp voltage becomes maximum.Therefore, based on this high lamp voltage, a low voltage output is made from the lighting circuit. Since it is controlled, there is a problem that it is difficult to obtain a predetermined high output voltage.

The present invention has been made in view of the above problems, and can simplify the configuration of a constant power control system such as a comparison unit, and can maintain a constant power with respect to both a change over time of a high-pressure discharge lamp and a change in input voltage. An object of the present invention is to provide a high pressure discharge lamp lighting device capable of obtaining output characteristics.

[Structure of the Invention] (Means for Solving the Problems) A high-pressure discharge lamp lighting device of the present invention includes a DC power supply; a switching element and a P that performs PWM control of the switching element.
A switching regulator including WM control means;
A high-pressure discharge lamp that is energized based on the output of the switching regulator; a lamp voltage detection means that detects a signal corresponding to the lamp voltage of the high-pressure discharge lamp; a signal obtained from the lamp voltage detection means immediately before starting the high-pressure discharge lamp A lamp current detection means for detecting a signal corresponding to the lamp current of the high-pressure discharge lamp; a PWM control means according to a superposed value of the detection signal of the lamp voltage detection means and the detection signal of the lamp current detection means To increase the output voltage immediately before starting the high pressure discharge lamp,
And a comparison means for controlling the high-pressure discharge lamp at a constant power after the high-pressure discharge lamp is started.

A transistor, for example, can be used as the switching element of the switching regulator. Also
As the PWM control means, for example, one that generates a pulse having a duty ratio according to the output of the error amplifier and drives the switching element can be used.

(Operation) According to the present invention, the lamp voltage of the high pressure discharge lamp is V0,
If the lamp current is I0 and the reference voltage of the comparison means is Vref, the detection signal of the lamp voltage detection means is determined by the voltage division circuit of the lamp voltage detection means. The voltage is, for example, 1 / N of the lamp voltage.

Further, the detection signal of the lamp current detecting means is such that, when the lamp current detecting means is composed of, for example, a resistor and the resistance value of the resistance is r, a voltage corresponding to the lamp current by the resistance,
It becomes rI0.

The comparison means inputs a value obtained by superimposing the detection signal of the lamp current detection means on the detection signal of the lamp voltage detection means, and outputs a signal by detecting a difference from a preset reference value, for example, and PWM control of the switching regulator. Since the means controls the on / off frequency or duty ratio of the switching element based on the signal output from the comparison means, the lamp characteristic at the time of lighting is V0 / N + rI0 = Vref.
It looks like the solid line in the figure. Further, the lamp power P0 is P0 = V0I0 = V0 (NVref-V0) / Nr, which is shown by the broken line in FIG.
That is, the lamp power P0 becomes maximum when V20 / 2 (however, the open circuit voltage V20 = NVref) and the slope becomes zero. Therefore, even if the lamp voltage V0 and the lamp current I0 fluctuate in the vicinity, the lamp power P0 P0 hardly changes.
That is, the lamp power P0 is stabilized.

Further, in the high pressure discharge lamp lighting device of the present invention,
The lamp characteristic is substantially constant even if the input voltage changes, and the lamp power P0 is stable with respect to the input voltage.

Therefore, the present invention can be constant power control, the constant power control means, depending on the value obtained by superimposing the detection signal of the lamp current detection means on the detection signal of the lamp voltage detection means, the PWM control means of the switching regulator. Since the configuration is controlled, comparison with the reference voltage, for example, by the comparison unit becomes easy.

Further, in the present invention, the switching regulator is a DC circuit. Therefore, the lamp voltage detecting means and the lamp current detecting means can be configured so as to easily detect the DC voltage. Therefore, the special means for transforming the alternating current for the voltage detection and the special means for converting the alternating current to the direct current for the voltage detection. It can be configured without any means.

Further, since the correction means for correcting the detection signal of the lamp voltage detection means is provided immediately before the start of the high pressure discharge lamp, the correction means changes the detection signal value of the lamp voltage detection means immediately before the start of the high pressure discharge lamp. The PWM control means of the switching regulator controls the ON / OFF frequency or duty ratio of the switching element so as to energize the high-pressure discharge lamp with a high voltage at which a lamp current flows through the high-pressure discharge lamp.

(Examples) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a high pressure discharge lamp device according to an embodiment of the present invention. In this device, an input from a DC power supply 1 is stabilized at a high voltage by a switching regulator 2 and supplied to a high pressure discharge lamp 3 as a high pressure discharge lamp, and the high pressure discharge lamp 3 is lit at a constant power.

The switching regulator 2 has a basic configuration in which the output current is pulse-width controlled (PWM control) so as to keep a predetermined amount of electricity constant, whereas a single voltage such as voltage or current is used as the predetermined amount of electricity. The function of voltage and current was set instead of the quantity of electricity. That is, the switching regulator 2 includes, for example, a switching transistor 21, a diode 22 and an inductor 23 that smooth the output current of the switching transistor 21, and a lamp voltage VL as switching elements that turn on and off the current from the DC power supply 1 and output the current. The lamp resistance value as a lamp voltage detecting means composed of a voltage dividing circuit for dividing the voltage to 1 / N, a voltage dividing circuit 24 as a lamp voltage detecting means of the lamp voltage detecting means composed of a resistor for detecting the lamp current IL is r. Resistor 25, reference voltage source
26, output voltage VL / N of voltage divider circuit 24 and terminal voltage r of resistor 25
Output voltage of reference voltage source 26 is VL / N + rIL
A PWM control circuit configured to drive the transistor 21 by generating a pulse having a duty ratio corresponding to the output of the error amplifier 27 and the error amplifier 27 as a comparison means for comparing the difference voltage with Vref and outputting the difference voltage as an error voltage. Means 28 are provided.

 Next, the operation of the embodiment of the present invention will be described.

The switching transistor 21 is driven by the pulse output of the PWM control means 28 to turn on / off the current from the DC power supply 1 to the high pressure discharge lamp 3. The inductor 23 supplies this to the high-pressure discharge lamp 3 while limiting the on-current when the transistor 21 is on, stores electromagnetic energy, and when the transistor 21 is off, the inductor 23, the high-pressure discharge lamp 3, and the accumulated electromagnetic energy. The current of the closed circuit composed of the diode 22 and the inductor 23 is maintained. As a result, the high pressure discharge lamp 3 is current-limited by the transistor 21 and the inductor 23, and
A smoothed current is supplied by 23 and the diode 22.

The voltage dividing circuit 24 is the lamp voltage VL of the high pressure discharge lamp 3.
Is divided into 1 / N and supplied to the non-inverting input terminal of the error amplifier 27. On the other hand, the inverting input terminal of the error amplifier 27 is connected to the reference voltage source.
The 25 output voltage (reference voltage) Vref is supplied. By the way, since the resistor 26 through which the lamp current IL flows is connected between the negative side terminal b of the high pressure discharge lamp 3 and the reference point a of the reference voltage source 25, the negative side terminal of the high pressure discharge lamp 3, that is, The reference point b of the voltage dividing circuit is the reference point a of the reference voltage source 25.
Is biased by rIL. That is, with reference to the point a, the voltage VL / N + rIL is applied to the non-inverting input terminal of the error amplifier 27, and the voltage Vr is applied to the inverting input terminal.
ef is being applied. Therefore, the error voltage of Vref- (VL / N + rIL) is output from the error amplifier 27. The PWM control means 28 generates a pulse width having a duty ratio according to this error voltage and drives the base of the transistor 21. As a result, the high pressure discharge lamp 3 has a VL / N
The current IL and the voltage VL such that + rIL = Vref are supplied, and PL
The lamp electric power PL which is VL = VL (Vref-VL / N) / r is supplied.

This operating characteristic is shown in FIG. In the figure, the solid line shows the lamp voltage-lamp current characteristic, and the broken line shows the lamp voltage-lamp power characteristic.

Here, the rated operating point (VLS, IL
S) is set to 1/2 of the lamp open-circuit voltage V20 (= Vref / N), and therefore 1/2 of the lamp short circuit current I2S (= Vref / r). As is apparent from FIG. 2, the rated operating point in the case of such setting is a point where the lamp power PLS has a maximum and the inclination is zero, so that the rating of the high-pressure discharge lamp 3 varies or changes with time. Even if it changes a little due to, the change in the lamp power PLS is slight and stabilized. Further, since the control is performed so that VL / N + rIL = Vref, the lamp voltage and the lamp current do not depend on the power supply voltage in the ideal state. Therefore, the lamp power is sufficiently stabilized against fluctuations in the power supply voltage.

In this embodiment, for example, a Zener diode 29 is connected to the voltage dividing circuit 24 as a correction means, and the voltage division ratio N when the lamp voltage VL exceeds a predetermined value (Zener voltage VZ of the Zener diode 29) is set. It is designed to increase non-linearly. As a result, the voltage immediately before starting the high pressure discharge lamp,
That is, the lamp open-circuit voltage can be increased from V20 without the Zener diode 29 to V20 ', as shown in FIG. As a result, the starting voltage of the lamp (= lamp open voltage) can be set to a high value without impairing the constant power property, the design constraint is eliminated, and the design becomes easy.

If the above device is arranged in the light source device body configured to output the output light from the high pressure discharge lamp of the known high pressure discharge lamp lighting device, it becomes a light source device.

The present invention is not limited to the above-described embodiments, and can be modified and implemented as appropriate. For example, in the above-described embodiment, an example has been described in which the DC output of the switching regulator 2 directly illuminates the high-pressure discharge lamp 3, but the DC output from the DC circuit including the voltage detection means is converted to a bridge inverter or a pair regulator. Low frequency (eg 50, 60 or 400Hz) or high frequency (eg 20) depending on the inverter or high frequency generator
The high-voltage discharge lamp may be lit by alternating current or high frequency by the output converted to 100 kHz).

EFFECTS OF THE INVENTION According to the present invention, the PWM control means of the switching regulator is controlled according to the value obtained by superimposing the detection signal of the lamp current detection means on the detection signal of the lamp voltage detection means. This makes it easy to compare with a reference voltage, for example, by the comparison means. Further, since the switching regulator is a DC circuit, the lamp voltage detecting means and the lamp current detecting means can be configured to easily detect a DC voltage. Therefore, a special means for transforming AC for voltage detection and a voltage detecting means. It can be configured without requiring any special means for converting alternating current into direct current. Further, the correction means corrects the detection signal of the lamp voltage detection means immediately before the start of the high-pressure discharge lamp to change the on / off control of the switching element, and the high voltage is discharged to a high voltage immediately before the high-pressure discharge lamp is started. It becomes possible to energize the lamp.

[Brief description of drawings]

FIG. 1 is a schematic circuit configuration diagram of a high pressure discharge lamp lighting device according to an embodiment of the present invention, FIG. 2 is a lamp voltage detecting means, an operation characteristic diagram of the high pressure discharge lamp lighting device shown in FIG. FIG. 4 is a schematic circuit configuration diagram of a conventional high pressure discharge lamp lighting device. 1 ... DC power supply, switching regulators 2, 3 ...
High-voltage discharge lamp, 21 ... switching element, 24 ... lamp voltage detection means, 26 ... lamp current detection means, 27 ... comparison means, 28 ... PWM control means, 29 ... correction means.

Claims (1)

[Claims] 1. A DC power supply; a switching regulator including a switching element and PWM control means for PWM controlling the switching element; a high-pressure discharge lamp that is energized based on the output of the switching regulator; and a lamp of a high-pressure discharge lamp. A lamp voltage detecting means for detecting a signal according to the voltage; a correcting means for correcting the signal obtained from the lamp voltage detecting means immediately before the start of the high pressure discharge lamp; a lamp for detecting a signal according to the lamp current of the high pressure discharge lamp Current detection means; controlling the PWM control means in accordance with the superposed value of the detection signal of the lamp voltage detection means and the detection signal of the lamp current detection means to increase the output voltage immediately before starting the high pressure discharge lamp and And a comparison means for controlling the high-pressure discharge lamp at a constant power after the discharge lamp is started. High pressure discharge lamp lighting device.