JP2001203089A - Lighting device for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feedback control device of discharge lamp current by which the discharge lamp current is kept constant and jumping, fadeout and flickering of lighting output are prevented, and further to obtain a simplified circuit of the detecting part of discharge lamp enabling to manufacture at low cost. SOLUTION: A detecting resistor 15 is provided in series with a discharge lamp 11, and a series circuit of a reference capacitor 16 corresponding to a resonance capacitor 10 and a reference resistor 17 corresponding to the detecting resistor is provided in parallel with the series circuit of the above discharge lamp 11 and the detecting resistor 15. By the relations of the voltage V1 of both ends of the above detecting resistor 15 and the voltage V2 at both ends of the above reference resistor 17, a control mans to feedback control the above inverter circuit 2 is provide to keep constant the discharge lamp current 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp by high frequency output of an inverter circuit.

[0002]

2. Description of the Related Art For example, in a discharge lamp lighting device, a discharge lamp is lit by a high frequency output of an inverter circuit, and a pair of switch elements of the inverter circuit are controlled to be continuously lit to light. There is something. However, conventional discharge lamp lighting devices have circuit constants and circuit configurations that are unlikely to cause light output jumping, extinction, and flicker during continuous dimming, and so the circuit of the discharge lamp lighting device is complicated. , The design was also difficult.

Further, feedback control is performed so that the discharge lamp current becomes constant, and the above-mentioned jump phenomenon of light output,
There is also a discharge lamp lighting device which prevents the occurrence of flickering and flickering. In this case, in order to detect a discharge lamp current Ila flowing through the discharge lamp 31, as shown in FIG.
The current transformer 32 is used, and the discharge lamp current Ila
Requires a transformer for detecting the discharge current, the circuit configuration of the discharge lamp current detection unit of the discharge lamp lighting device is complicated, and the manufacturing cost is high.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a feedback control of a discharge lamp current to stabilize a discharge lamp current, thereby reducing a light output jump phenomenon.
It is possible to prevent flickering and flickering, and to make the circuit configuration of the discharge lamp current detection unit simple and inexpensive.

[0005]

The technical means of the present invention for solving this technical problem includes an inverter circuit 2 for converting an output on the power supply side to a high frequency, and a resonance capacitor connected in parallel to the discharge lamp 11. 10 and the inverter circuit 2
In the discharge lamp lighting device in which the discharge lamp 11 is lit by the high frequency output of the above, a detection resistor 15 is provided in series with the discharge lamp 11 and a reference capacitor 16 corresponding to the resonance capacitor 10 and a reference capacitor corresponding to the detection resistor 15. A series circuit of a resistor 17 is provided in parallel with a series circuit of the discharge lamp 11 and the detection resistor 15, and a discharge lamp current Ila is obtained from a voltage V1 across the detection resistor 15 and a voltage V2 across the reference resistor 17. Is provided with a control means for performing feedback control of the inverter circuit 2 so that the constant value becomes constant.

Further, another technical means of the present invention includes an inverter circuit 2 for converting an output on the power supply side to a high frequency, and a resonance capacitor 10 connected in parallel to the discharge lamp 11.
In the discharge lamp lighting device in which the discharge lamp 11 is turned on by the high frequency output of the inverter circuit 2, a detection resistor 15 is provided in series with the discharge lamp 11, and a reference capacitor 16 and a detection resistor 15 corresponding to the resonance capacitor 10 are connected. A series circuit with a corresponding reference resistor 17 is connected to the discharge lamp 11.
And a detection resistor 15 are provided in parallel with each other in a series circuit.
Is that a control means for performing feedback control of the inverter circuit 2 so as to make the discharge lamp current Ila constant is provided by utilizing the fact that the voltage obtained by subtracting the above becomes a value corresponding to the discharge lamp current Ila.

Another technical means of the present invention is that the capacitance of the resonance capacitor 10 is C1, the capacitance of the reference capacitor 16 is C2, the resistance of the detection resistor 15 is R1, and the resistance of the reference resistor 1 is 1.
7, the resistance value is set so that the relationship of C1 / C2 = R2 / R1 is satisfied. Another technical means of the present invention is that the voltage V
The point is that the inverter circuit 2 is feedback-controlled so that the subtracted voltage V4 obtained by subtracting the reference voltage E, which is a DC voltage, and the voltage V2 across the reference resistor 17 from 0 becomes zero.

Another technical means of the present invention lies in that the discharge lamp 11 is dimmed by variably setting the voltage of the reference voltage E. According to another technical means of the present invention, the inverter circuit 2 includes a pair of switching elements 3 and 4 that are alternately turned on and off, and controls the on / off period of the switching elements 3 and 4 to dim the discharge lamp 11. In addition, the on-off period of the switching elements 3 and 4 is controlled so that the discharge lamp current Ila becomes constant.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes an electrolytic capacitor serving as a DC power supply. Both ends of the electrolytic capacitor 1 are configured to obtain a predetermined DC voltage by rectifying and smoothing an AC power supply (not shown) with a rectifier circuit or the like. . Reference numeral 2 denotes an inverter circuit, which is constituted by a self-excited and controlled half-bridge circuit, and a pair of switching elements 3 and 4 and switching elements 3 and 4 which are turned on and off alternately.
And a current transformer 6 for driving the current transformer. The pair of switching elements 3 and 4 are constituted by, for example, an insulated gate field effect transistor (MOSFET).
An LC resonance circuit including a ballast choke 9, a resonance capacitor 10, and a discharge lamp 11 connected in parallel to the resonance capacitor 10 is connected to the inverter circuit 2 via a capacitor 7 for cutting a DC component. , 4 perform an on-off operation alternately at a constant frequency. If the on-period of the switching element 4 becomes longer, the on-period of the switching element 3 becomes shorter, and if the on-period of the switching element 4 becomes shorter, the switching element becomes 3
Is longer, and the switching elements 3 and 4 repeat opposing on / off operations. When the switching element 4 is turned on, a current flows through the current transformer 6 via the LC resonance circuit, and a voltage whose polarity changes according to the direction of the resonance current is induced in the current transformer 6, and the induced voltage causes the switching element to change. The inverter 3 is turned on and off alternately to oscillate the inverter circuit 2, and the LC resonance circuit is excited by the inverter circuit 2, so that the discharge lamp 11 is turned on by the high frequency output of the inverter circuit 2.

Reference numeral 14 denotes a discharge lamp current Il flowing through the discharge lamp 11.
a discharge lamp current detection circuit for detecting the discharge lamp 11
The detection resistor 15 connected in series to the
, And a reference resistor 17 corresponding to the detection resistor 15. A series circuit of the reference capacitor 16 and the reference resistor 17 is connected in parallel to a series circuit of the discharge lamp 11 and the detection resistor 15. ing. From the connection point a between the discharge lamp 11 and the detection resistor 15, the voltage V1 across the detection resistor 15 (the potential at the connection point a becomes the voltage V1 across the detection resistor 15).
And the reference capacitor 16
From the connection point b of the reference resistor 17 to the voltage V2 across the reference resistor 17 (the potential at the connection point b is the voltage V2 across the reference resistor 17)
(Corresponding to).

The capacitance of the reference capacitor 16 is desirably set to a value that does not affect the resonance of the LC resonance circuit, for example, to about 1/50 of the capacitance of the resonance capacitor 10. When the capacitance of the resonance capacitor 10 is C1, the capacitance of the reference capacitor 16 is C2, the resistance of the detection resistor 15 is R1, and the resistance of the reference resistor 17 is R2, C1 / C2 = R2
The capacitance of the resonance capacitor 16, the capacitance of the reference capacitor 16, the resistance value of the detection resistor 15, and the resistance value of the reference resistor 17 are set so as to satisfy the relationship of / R1. By setting in this way, it is possible to perform feedback control on the discharge lamp current Ila by the control means described later.

That is, the voltage V1 across the detection resistor 15, the voltage across the reference resistor 17 is V2, the current flowing through the resonance capacitor 16 is I1, and the current flowing through the reference capacitor 16 is I2.
2. If the discharge lamp current is Ila, V1 = (I1 + Ila) × R1 V1-V2 = (I1 + Ila) × R1-I2 × R2 = Ila × R1 + I1 × R1-I2 × R2 where I1 × R1-I2 × R2 In order to reach = 0, the constants may be designed so that the following relationship is satisfied: I1 × R1 = I2 × R2∴C1 / C2 = R2 / R1.

Therefore, if the relation of C1 / C2 = R2 / R1 is established, V1-V2 = Ila × R1.
V1-V2 corresponds to discharge lamp current Ila (proportional)
The obtained value (control amount) can be taken out, and the feedback control can be performed on the discharge lamp current Ila as described above. 21 is a dimming signal conversion circuit,
The dimming signal d shown in FIG. 2 is input, and a dimming conversion signal e having a voltage corresponding to the dimming signal d (for example, proportional to the duty ratio of the dimming signal d shown in FIG. 2) is output. It is supposed to. The dimming signal d is variably set by adjusting the volume. When the dimming of the discharge lamp 11 is not performed (when the discharge lamp 11 is fully lit), the dimming signal d is set as shown in FIG.
As shown in (2), the waveform always becomes 0 V, and by adjusting the volume, the dimming signal d becomes as shown in FIG.
As shown in FIG. 7, the waveform is a rectangular wave of, for example, 1 KHz, and a high-voltage period is sequentially and continuously increased according to the degree of volume adjustment.

Reference numeral 23 denotes a reference voltage generation circuit which receives the dimming conversion signal e from the dimming signal conversion circuit 21 and outputs a reference voltage E having a magnitude proportional to the magnitude of the voltage of the dimming conversion signal e. It is configured as follows. That is, when the light of the discharge lamp 11 is not adjusted (in the case of full lighting), the reference voltage generation circuit 23
Outputs the highest DC voltage (for example, 5 V) as the reference voltage E. Further, when dimming the discharge lamp 11 (in the case of dimming lighting), the reference voltage generation circuit 23 outputs a DC voltage (for example, 3 V lower than 5 V,
4V) is output as the reference voltage E.

Reference numeral 25 denotes a control IC, and a feedback circuit 2
6 and a PWM circuit 27. Feedback circuit 2
6, a voltage V1 across the detection resistor 15 is input from a connection point a between the discharge lamp 11 and the detection resistor 15, and a voltage V2 across the reference resistor 17 is applied to the reference voltage E of the reference voltage generating circuit 23;
Is input, and the subtracted voltage V4 (V) obtained by subtracting the reference voltage E and the voltage V2 across the reference resistor 17 from the voltage V1 across the detection resistor 15 is input to the comparison voltage V3 (V3 = E + V2) on which
1-V2-E), and the subtracted voltage V4 (V1-V
2-E).

The PWM circuit 27 includes a feedback circuit 2
6, a PWM for inputting a subtraction voltage V4 (V1-V2-E) and variably adjusting the ON period of the switching element 4 so that the subtraction voltage V4 (V1-V2-E) becomes zero.
It is configured to output a signal. That is, if the detection voltage V1 and the comparison voltage V3 (E + V2) are equal, the PWM circuit 27 keeps the ON period of the switching element 4 as it is, and the detection voltage V1 changes to the comparison voltage V3 (E + V2).
V2), the on-period of the switching element 4 is shortened to control the discharge lamp current Ila to be small. If the detection voltage V1 is smaller than the comparison voltage (E + V2), the switching element is switched. The on-period 4 is lengthened to control the discharge lamp current Ila to increase, and to control the discharge lamp current Ila to be constant.

Next, the operation will be described. The switching elements 3 and 4 are turned on and off alternately, and the inverter circuit 2 performs an oscillating operation, and a discharge lamp current Ila corresponding to the on-period of the switching element 4 flows through the discharge lamp 11, and the inverter circuit 2
, The discharge lamp 11 is turned on. When the dimming of the discharge lamp 11 is not performed (in the case of full lighting), the reference voltage generating circuit 23 outputs the reference voltage E which is the highest DC voltage.
Is output from the feedback circuit 26 to the detection resistor 15.
Is subtracted from the reference voltage E, which is a DC voltage, and the voltage V2 across the reference resistor 17, and the PWM circuit 27 outputs
And outputs a PWM signal for variably adjusting the ON period of the switching element 4 so that the subtraction voltage V4 (V1-V2-E) becomes zero. The discharge lamp current I flowing through the discharge lamp 11
la is kept at a constant value corresponding to the reference voltage E, and the discharge lamp 11 is fully lit without dimming.

More specifically, if the discharge lamp current Ila does not fluctuate, the voltage V1 across the detection resistor 15 is also held constant, and the voltage V1 across the detection resistor 15 and the comparison voltage V3 are kept in balance. The discharge lamp current Ila is maintained at a constant current without changing the ON period of the switching element 4. If the discharge lamp current Ila rises for some reason, the voltage V1 across the corresponding rises, and the comparison voltage V3 (E + V) is compared with the voltage V1 across the detection resistor 15.
2) becomes smaller, and the subtraction voltage V4 (V1-V2-E) output from the feedback circuit 26 becomes non-zero.
Feedback control is performed such that the on-period of the switching element 4 is shortened to reduce the discharge lamp current Ila to return to a constant current. Further, when the discharge lamp current Ila decreases, the voltage V1 across the detection resistor 15 decreases correspondingly, and the comparison voltage V3 (E + V) is compared with the voltage V1 across the detection resistor 15.
2) increases, and the subtraction voltage V4 (V1-V2-E) output from the feedback circuit 26 is not 0,
Feedback control is performed such that the on-period of the switching element 4 is lengthened to increase the discharge lamp current Ila and return to a constant current.

When dimming the discharge lamp 11 (in the case of dimming lighting), the dimming signal d input to the dimming signal conversion circuit 23 is shown in FIGS. Thus, a 1 KHz rectangular wave signal having an ON period of a length corresponding to the volume setting is obtained. In this case, the reference voltage generation circuit 23
Is a DC voltage (for example, 5
(3V, 4V, etc., lower than V) is output as the reference voltage E, and the feedback circuit 26 subtracts the lower reference voltage E from the voltage V1 across the detection resistor 15 and the voltage V2 across the reference resistor 17 from the feedback voltage 26. V4 (V1-V2-
E) is output, and the PWM circuit 27 receives the subtraction voltage V4 (V1-V2-E) from the feedback circuit 26, and switches the switching element 4 so that the subtraction voltage V4 (V1-V2-E) becomes zero. And outputs a PWM signal for variably adjusting the ON period of. As a result, the discharge lamp current Ila flowing through the discharge lamp 11 is maintained at a constant value corresponding to the reduced reference voltage E, and the discharge lamp 11 is dimmed and turned on, and the discharge lamp current Ila is fully turned on. Similarly, feedback control is performed so that the current becomes constant.

Therefore, the detection section of the discharge lamp current Ila can be constituted by the detection resistor 15 and the series circuit of the reference capacitor 16 and the reference resistor 17, and the discharge lamp current Ila is detected as in the prior art. The need for a transformer
The circuit of the detecting section for the discharge lamp current Ila can be made extremely simple, and the manufacturing cost can be reduced. In addition, the discharge lamp current Ila can be made constant, thereby preventing the jump phenomenon, the disappearance and the flickering of the light output. In the above-described embodiment, the inverter circuit 2 is configured by a self-excited and independent half-bridge circuit including the current transformer 6 that drives the switching elements 3 and 4. However, the inverter circuit 2 has such a configuration. However, the present invention is not limited to this, and may be other types or other types.

In the above embodiment, the inverter circuit 2 is configured to obtain a high-frequency output from a DC power supply. Instead, the inverter circuit 2 is configured to obtain a high-frequency output from a low-frequency AC. Is also good. Further, in the above-described embodiment, the discharge lamp lighting device is configured to be capable of dimming and lighting the discharge lamp, but instead, the discharge lamp lighting device is configured to be unable to dimmably light the discharge lamp. You may.

[0022]

According to the present invention, by performing feedback control of the discharge lamp current Ila, the discharge lamp current Ila is controlled.
, The jump phenomenon, extinction, and flickering of the light output can be prevented, and the circuit of the detecting section for the discharge lamp current Ila can be manufactured at a low cost with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a dimming signal d.

FIG. 3 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 2 Inverter circuit 3 Switching element 4 Switching element 10 Resonant capacitor 11 Discharge lamp 14 Discharge lamp current detection circuit 15 Detection resistor 16 Reference capacitor 17 Reference resistor 21 Dimming signal conversion circuit 25 Control IC

Claims (6)

[Claims] 1. An inverter circuit (2) for converting an output on a power supply side to a high frequency, and a resonance capacitor (10) connected in parallel to a discharge lamp (11), wherein a high frequency output of the inverter circuit (2) is used. In a discharge lamp lighting device for lighting a discharge lamp (11), a detection resistor (15) is provided in series with the discharge lamp (11), and a detection capacitor (16) corresponding to a resonance capacitor (10) is detected. A series circuit of a reference resistor (17) corresponding to the resistor (15) is provided in parallel with a series circuit of the discharge lamp (11) and the detection resistor (15), and a voltage V1 across the detection resistor (15). And a control means for performing feedback control of the inverter circuit (2) so that the discharge lamp current Ila becomes constant from the voltage V2 across the reference resistor (17). Lamp lighting device. 2. An inverter circuit (2) for converting an output on the power supply side to a high frequency, and a resonance capacitor (10) connected in parallel to the discharge lamp (11). In a discharge lamp lighting device for lighting a discharge lamp (11), a detection resistor (15) is provided in series with the discharge lamp (11), and a detection capacitor (16) corresponding to a resonance capacitor (10) is detected. A series circuit of a reference resistor (17) corresponding to the resistor (15) is provided in parallel with a series circuit of the discharge lamp (11) and the detection resistor (15). Reference resistance (17)
Control means for feedback-controlling the inverter circuit (2) so that the discharge lamp current Ila becomes constant by utilizing the fact that the voltage obtained by subtracting the voltage V2 between both ends becomes a value corresponding to the discharge lamp current Ila. A discharge lamp lighting device, comprising: 3. The capacitance of the resonance capacitor (10) is C
1, the capacitance of the reference capacitor (16) is C2, the resistance of the detection resistor (15) is R1, and the resistance of the reference resistor (17) is R
3. The discharge lamp lighting device according to claim 1, wherein, when 2 is set, C1 / C2 = R2 / R1. 4. An inverter so that a subtraction voltage V4 obtained by subtracting a reference voltage E, which is a DC voltage, and a voltage V2 across the reference resistor (17) from a voltage V1 across the detection resistor (15) becomes zero. 3. The discharge lamp lighting device according to claim 1, wherein the circuit (2) is feedback-controlled. 5. The discharge lamp lighting device according to claim 4, wherein the discharge lamp is dimmed by variably setting the reference voltage E. 6. The inverter circuit (2) includes a pair of switching elements (3, 4) that are turned on and off alternately,
Controlling the on / off period of the switching element (3, 4) to dimming the discharge lamp (11) and controlling the on / off period of the switching element (3, 4) so that the discharge lamp current Ila is constant; The discharge lamp lighting device according to any one of claims 1 to 5, wherein