EP1773104A1

EP1773104A1 - Discharge lamp lighting device and illumination apparatus

Info

Publication number: EP1773104A1
Application number: EP06255050A
Authority: EP
Inventors: Hiroshi c/o Toshiba Lighting & Tech Co. Terasaka; Tomokazu c/o Toshiba Lighting & Tech Co. Usami; Hideo c/o Toshiba Lighting & Tech Co. Kozuka; Kazuyuki c/o Toshiba Lighting & Tech Co. Uratani
Original assignee: Toshiba Lighting and Technology Corp
Current assignee: Toshiba Lighting and Technology Corp
Priority date: 2005-09-29
Filing date: 2006-09-29
Publication date: 2007-04-11
Also published as: JP2007173204A; JP4923852B2

Abstract

A discharge lamp lighting device includes a microcomputer (18) which outputs a reference voltage value V_S2 corresponding to lamp power at the full-lighting time which corresponds to lamp voltage at the input time of a full-lighting signal and outputs a reference voltage value V_S2 corresponding to lamp power at the dimming time based on values "a" and "b" corresponding to a dimming light amount, lamp voltage and lamp power at the full-lighting time when a dimming signal is input, output means (30) for detecting voltage corresponding to lamp voltage by use of resistors (10, 11), detecting voltage corresponding to a lamp current by use of a resistor (9) to output a voltage value V_S1, and a controller (15) which controls a voltage step-down chopper circuit (4) based on the voltage value V_S1 and reference voltage value V_S2.

Description

This invention relates to a discharge lamp lighting device and illumination apparatus which perform a dimming lighting operation by using control means such as a microcomputer or the like.
Conventionally, as a discharge lamp lighting device using a microcomputer, a device described in Jpn. Pat. Appln. KOKAI Publication No. 2005-25995 is known. In the above Publication, a lighting device including a chopper circuit which adjusts power supplied to a discharge lamp, a chopper current detecting circuit, a lamp voltage detecting circuit, a control circuit which is supplied with detection outputs of both of the detecting circuits and controls the switching element of the chopper circuit to control power of the discharge lamp and a microcomputer which determines a control value used when the control circuit controls the power is disclosed. Further, in the above Publication, the technique for determining a power control amount based on a linear expression corresponding to a lamp voltage value by use of the microcomputer is also disclosed.
However, in Jpn. Pat. Appln. KOKAI Publication No. 2005-25995 , there is no description about the way of controlling the lamp power by use of the microcomputer and control circuit in the dimming control operation and the lamp power control operation at the dimming time cannot be adequately performed.
This invention is to provide a discharge lamp lighting device and illumination apparatus which can adequately perform the lamp power control operation at the full-lighting time and even at the dimming time, derive target lamp power in a short period of time at the dimming time and rapidly perform the lamp power control operation.
According to one aspect of this invention, there is provided a discharge lamp lighting device including a control circuit which controls a power control operation of a discharge lamp by controlling an output of a chopper circuit according to a dimming signal and lamp voltage, wherein the control circuit includes means for setting a reference voltage value according to lamp voltage detected by a lamp voltage detecting circuit and a full-lighting signal or dimming signal from a dimming signal inputting section, a first detecting section which is connected in parallel with the discharge lamp to detect voltage corresponding to the lamp voltage, a second detecting section which is connected in series with the discharge lamp to detect voltage corresponding to a lamp current, outputting means for detecting voltage corresponding to the sum of voltages detected by both of the detecting sections, and output control means for controlling an output of the chopper circuit to set the sum voltage value output from the outputting means equal to the reference voltage value and the discharge lamp is set to have a stable lighting region in which rated lamp powers at the full-lighting time and at the dimming time are ensured in a lamp voltage region with preset width.
In this invention, the definitions and technical meanings of terms are as follows if not specifically stated.
The dimming signal is, for example, a PWM (Pulse Width Modulation) signal. It is input to the discharge lamp lighting device from, for example, a switch provided outside the discharge lamp lighting device. The chopper circuit may include a voltage step-up chopper, voltage step-down chopper and a combination thereof. The chopper circuit has at least one switching element and controls power output by ON/OFF-controlling the switching element. Detection of lamp voltage is to divide voltage generated across the discharge lamp and detect the divided voltage and to detect output voltage from the chopper circuit as voltage approximately equal to lamp voltage.
For example, the control circuit includes a microcomputer or the like. The microcomputer or the like includes a microcomputer, microprocessor, CPU, DSP, arithmetic operation device and other similar devices. Further, means such as a polarity inverting circuit, inverter circuit and the like may be connected or may not be connected between the chopper circuit and the discharge lamp.
In another aspect of this invention, the means for setting the reference voltage value of the control circuit sets a reference voltage value by providing a table in which values "a" corresponding to lamp voltages which correspond to dimming light amounts and values "b" corresponding to lamp currents which correspond to the dimming light amounts are set and using lamp voltage detected by the lamp voltage detecting circuit and the corresponding values "a" and "b" of the table based on an input dimming signal.
Further, in still another aspect of this invention, the control circuit includes switching means for setting an output mode to a rated output mode in which the starting operation is performed in a rated starting condition at the dimming start time and switching the output mode from the rated output mode to a dimming output mode in which the starting operation is performed in a dimming start condition while the power characteristic corresponding to the dimming light amount of the dimming signal is maintained when the lamp voltage of the discharge lamp has reached preset voltage.
In another aspect of this invention, there is provided an illumination apparatus which includes a discharge lamp, a discharge lamp lighting device described in one of claims 1 to 3, and an illumination apparatus main body having the discharge lamp and discharge lamp lighting device mounted thereon.
In this invention, the lamp power control operation can be adequately performed at the full-lighting time and even at the dimming time. Further, target lamp power can be derived in a short period of time at the dimming time and the rapid lamp power control operation can be performed. Further, in this invention, the reference voltage value can be easily set. Also, in this invention, a possibility that the lamp will be extinguished can be suppressed without delaying the rise operation.
The invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram showing the circuit configuration of a discharge lamp lighting device according to a first embodiment of this invention.
FIG. 2 shows two load power curves in the embodiment of FIG. 1, i.e., a curve showing the relation the lamp power W_L(F) and lamp voltage V_L(F) have during full lighting, and a curve showing the relation the lamp power W_L(d) and lamp voltage V_L(d) have during 50%-dimming.
FIG. 3 is a diagram showing a table in which values "a" and "b" corresponding to dimming light amounts in the above embodiment are set.
FIG. 4A is a diagram showing a rise characteristic of lamp voltage at the start lighting time when the lamp is lighted in the full-lighting mode.
FIG. 4B is a diagram showing a rise characteristic of lamp voltage at the start lighting time when the lamp is lighted in the dimming lighting mode.
FIG. 4C is a diagram showing a comparison example and showing a rise characteristic when the start lighting control operation is not performed while the lamp is lighted in the dimming lighting mode.
FIG. 5 is a diagram showing the circuit configuration of a discharge lamp lighting device according to a second embodiment of this invention.
FIG. 6 is a diagram showing the circuit configuration of a discharge lamp lighting device according to a third embodiment of this invention.
FIG. 7 is a diagram showing the circuit configuration of a discharge lamp lighting device according to a fourth embodiment of this invention.
FIG. 8 is a diagram showing the circuit configuration of a discharge lamp lighting device according to a fifth embodiment of this invention.
FIG. 9 is a diagram showing the configuration of an illumination apparatus according to a sixth embodiment of this invention.
There will now be described embodiments of this invention with reference to the accompanying drawings.

(First Embodiment)

As shown in FIG. 1, a DC power supply is formed by connecting an input terminal of a full-wave rectifier circuit 2 to an AC power supply 1 and connecting a smoothing capacitor 3 to an output terminal of the full-wave rectifier circuit 2.
A voltage step-down chopper circuit 4 used as a chopper circuit is connected to the DC power supply. The voltage step-down chopper circuit 4 includes a switching element 5, inductor 6 and diode 7.
The switching element 5 is connected at one end to the positive terminal of the DC power supply and connected at the other end to one end of the inductor 6 and the cathode terminal of the diode 7. The anode terminal of the diode 7 is connected to the negative terminal of the DC power supply.
The positive output terminal of the voltage step-down chopper circuit 4 is used as the other end of the inductor 6 and the negative output terminal thereof is used as the anode of the diode 7. One electrode of a discharge lamp 8 is connected to the other end of the inductor 6 and the other electrode thereof is connected to the anode terminal of the diode 7 via a resistor 9 used as a second detecting section.
A series circuit of resistors 10 and 11 which configure a first detecting circuit and a capacitor 12 are connected in parallel between the electrodes of the discharge lamp 8. A lamp current I_L flows through the resistor 9 to generate voltage r·I_L across the resistor 9. In this case, r indicates the resistance of the resistor 9.
The lamp voltage V_L is generated across the series circuit of the resistors 10 and 11. The lamp voltage V_L is divided by, for example, 1/N by use of the resistors 10 and 11. That is, voltage generated across the resistor 11 is set to V_L/N.
Therefore, a voltage value V_S1 of the voltage generated at the connection node of the resistors 10 and 11 is set to (V_L/N + r·I_L) obtained by superimposing the lamp voltage V_L/N divided by the resistors 10 and 11 on the voltage r·I_L generated by the lamp current I_L flowing through the resistor 9.
The voltage value V_S1 contains factors of the lamp voltage and lamp current and can be set to correspond to lamp power W_L supplied to the discharge lamp 8.
A lamp voltage detecting circuit configured by a series circuit of resistors 13 and 14 is connected in parallel with the discharge lamp 8. The detected value V_L of voltage obtained by dividing the lamp voltage is output from a connection node of the series circuit of the resistors 13 and 14. The lamp voltage detecting circuit may be configured by using the resistors 10, 11 instead of the resistors 13, 14.
The voltage sep-down chopper circuit 4 switches the switching element 5 according to a signal from a controller 15. The voltage value V_S1 generated at the connection node of the resistors 10 and 11 is input to an operational amplifier 21 of the controller 15 via an output line 30 used as output means.
A dimming signal input section 16 is supplied with a remote control signal of full lighting from the exterior to output a full-lighting signal and is supplied with a remote control signal of dimming light to output a dimming signal. The full-lighting signal and dimming signal output from the dimming signal input section 16 are PWM (pulse width modulation) signals, converted into DC voltage by a filter 17 and then input to a dimming input terminal of a microcomputer 18.
The detected value V_L of voltage obtained by dividing the lamp voltage output from the lamp voltage detecting circuit (resistors 13 and 14) is input to the V_L input terminal of the microcomputer 18. The dimming input terminal and V_L input terminal each have an A/D converter to convert the input voltage value into a digital value and supply the same.
The microcomputer 18 has a table 19. In the table 19, the characteristic of a load power curve of lamp power W_L(F) with respect to lamp voltage V_L(F) at the full-lighting time indicated by a graph g1 in FIG. 2 is set as data. For example, when a 100W type ceramic metal halide lamp (neocera MT100 CHE) made by TOSHIBA LIGHTING & TECHNOLOGY CO. is used as the discharge lamp 8, the load power curve g1 has a stable lighting region (flat region of the graph g1) which ensures that the rated lamp power W_L is set at 100W in a range before and after the lamp voltage of 100V, that is, in a range of the lamp voltage V_L of approximately 90V to 110V. In the table 19, values "a" and "b" which respectively correspond to the lamp voltage and lamp current and vary according to a dimming light amount of a dimming signal are set. The values "a" and "b" can be attained based on actual measurements when the discharge lamp 8 is lighted in a dimming mode.
The controller 15 and microcomputer 18 configure a control circuit. The controller 15 compares the voltage value V_S1 with a reference voltage value V_S2 output from the microcomputer 18 in the operational amplifier 21 and controls the switching duty of the switching element 5 of the voltage step-down chopper circuit 4 to set the compared voltage values equal to each other. By controlling the voltage step-down chopper circuit 4 by use of the controller 15, the voltage step-down chopper circuit 4 performs the power control operation for the discharge lamp 8.
When an input signal to the dimming signal input section 16 is a full-lighting signal and if the microcomputer 18 is supplied with a detected value V_L(F) of the lamp voltage from the lamp voltage detecting circuit (resistors 13, 14), the microcomputer 18 reads out lamp power W_L(F) corresponding to the lamp voltage V_L(F) from the table 19. Then, it outputs an output corresponding to the lamp power W_L(F) from the output terminal thereof.
The output corresponding to the lamp power W_L(F) output from the output terminal of the microcomputer 18 is supplied to the operational amplifier 21 of the controller 15 via the filter circuit 20 as the reference voltage value V_S2.
Next, the operation of the discharge lamp lighting device when a dimming signal with the dimming light amount of 50% is input to the dimming input terminal of the microcomputer 18 is explained. In this case, the dimming light amount of 50% indicates that power is adjusted to set the light output to 50% of the light output at the full-lighting time.
For example, a graph g2 of FIG. 2 shows the characteristic of a load power curve of the lamp power W_L(d) with respect to lamp voltage V_L(d) when the dimming light amount of the discharge lamp 8 is set to 50%. When the dimming light amount is 50%, light flux from the discharge lamp 8 becomes 50% of the light flux at the full-lighting time. At this time, the lamp power W_L(d) of the discharge lamp 8 is set to 60W.
The range of the lamp voltage V_L(d) in the stable lighting region (flat region of the graph g2) in which the lamp power of the discharge lamp 8 is maintained at 60W varies in a range higher and lower than 88V, that is, in a range of approximately 80V and 96V. Thus, the lamp voltage of the discharge lamp 8 varies with a variation in the lamp power according to the dimming light amount and, as a result, the stable lighting region and lamp current also vary.
Voltage value V_S1 (= V_L/N + r·I_L) is generated at the connection node of the resistors 10 and 11 that constitute a series circuit, jointly with the resistor 9. Note that the voltage value V_S1 has been obtained by adding voltage r·I_L generated from the current I_L flowing in the resistor 9 to the lamp voltage V_L/N that is a voltage obtained by dividing V_L by N by virtue of the resistors 10 and 11. The voltage value V_S1 is applied to the operational amplifier 21 of the controller 15.
When a dimming signal is input in a state where the full-lighting signal is input, the microcomputer 18 reads out values "a" and "b" corresponding to the dimming light amount of the dimming signal from the table 19 and lights the discharge lamp 8 in the dimming mode.
Next, the microcomputer 18 derives lamp power W_L(d) at the dimming time based on the lamp voltage V_L(F) obtained at this time, lamp power W_L(F) at the full-lighting time read out from the table 19 and the values "a" and "b" read out from the table 19.
As described before, since the lamp power W_L(F) is the sum of the lamp voltage factor and lamp current factor, the lamp current at the full-lighting time is derived by calculating the expression of (lamp power W_L(F) at full-lighting time - (lamp voltage V_L(d) at dimming time)/(value "b")). Then, the lamp voltage V_L(F) at the full-lighting time is also calculated.
Therefore, the lamp power W_L(d) at the dimming time is obtained by calculating the expression of (value "a" × lamp voltage V_L(F) at full-lighting time + value "b" × lamp current at full-lighting time).
At this time, the lamp power W_L(d) corresponding to the dimming light amount can be derived by calculation to set the relation between the lamp voltage V_L and the lamp power W_L(d) at the dimming time to the characteristic of a load power curve approximately similar to the load power curve g1 at the full-lighting time.
By considering a case where the discharge lamp 8 is inadvertently extinguished and re-started, the microcomputer 18 may derive the lamp power W_L(d) of the discharge lamp 8 to jump from the load power curve g1 to the load power curve g2 when the lamp voltage V_L has exceeded a preset value. Then, an output corresponding to the thus derived lamp power W_L(d) is supplied from the output terminal of the microcomputer 18 to the operational amplifier 21 of the controller 15 via the filter circuit 20 as the reference voltage value V_S2.
Further, when a dimming light amount is changed while a dimming signal with a certain dimming light amount is being input, the microcomputer 18 temporarily derives a lamp voltage value V_L(F) at the full-lighting time by use of a detected value V_L(d1) of the lamp voltage which is so far supplied thereto from the lamp voltage detecting circuit (resistors R13, R14) and values "a1" and "b1" based on the dimming light amount obtained up to now. Then, it reads out corresponding lamp power W_L(F) at the full-lighting time from the table 19 by use of the lamp voltage value V_L(F) at the full-lighting time.
Further, the microcomputer 18 reads out values "a2" and "b2" corresponding to a new changed dimming light amount from the table 19 and derives lamp power W_L(d) corresponding to the new dimming light amount based on the readout values "a2" and "b2".
Also, at this time, the lamp power W_L(d) corresponding to the dimming light amount is derived by calculation to set the relation between the lamp voltage V_L and the lamp power W_L(d) at the dimming time to the characteristic of a load power curve which is approximately similar to the load power curve g1 at the full-lighting time. Then, an output corresponding to the thus derived lamp power W_L(d) is supplied from the output terminal of the microcomputer 18 to the operational amplifier 21 of the controller 15 via the filter circuit 20 as the reference voltage value V_S2.
Next, for example, a case wherein the discharge lamp 8 which is lighted in the full-lighting mode with the lamp power W_L(F) set at 100W, the lamp voltage V_L(F) set at 100V and the lamp current I_L(F) set 1A at the full-lighting time is changed into a dimming mode with the dimming light amount 50% is explained.
In this example, a table 19a in which values "a" and "b" corresponding to the dimming light amount are set as shown in FIG. 3 is used as part of the table 19. In the discharge lamp lighting device used in this example, the maximum dimming light amount is set to 50% and the control operation for the dimming light amount exceeding 50% is not performed. Therefore, data set in the table 19a is set in a range of the dimming light amount of 0% to 50%.
When a dimming signal with the dimming light amount 50% is input, the microcomputer 18 acquires a value "a" = 0.89 and a value "b" = 0.67 corresponding to the dimming light amount from the table 19a. Then, it derives the lamp power W_L(d) at the 50%-dimming time which is approximately equal to 60W based on the lamp power W_L(F) = 100W at the full-lighting time, the lamp voltage V_L(F) = 100V at the full-lighting time, the value "a" = 0.89 and the value "b" = 0.67.
With the above configuration, the microcomputer 18 reads out lamp power W_L(F) corresponding to the lamp voltage V_L(F) from the table 19 while a full-lighting signal is being input from the dimming signal input section 16 to the microcomputer 18 via the filter 17. Then, it supplies an output corresponding to the lamp power W_L(F) from the output terminal thereof to the operational amplifier 21 of the controller 15 via the filter circuit 20 as the reference voltage value V_S2.
The voltage value V_S1 of (V_L/N + r·I_L) obtained by superimposing the voltage V_L/N on the voltage r·I_L generated by the lamp current I_L flowing through the resistor 9 is input from the connection node of the resistors 10 and 11 to the operational amplifier 21 of the controller 15.
The controller 15 compares the voltage value V_S1 with the reference voltage value V_S2 in the operational amplifier 21 and controls the switching duty of the switching element 5 of the voltage step-down chopper circuit 4 to set the voltage value V_S1 equal to the reference voltage value V_S2.
As a result, power supplied from the voltage step-down chopper circuit 4 to the discharge lamp 8 is controlled and set to power of, for example, W_L(F) = 100W in the stable lighting region of the load power curve g1 at the full-lighting time.
In this state, if a dimming signal is input from the dimming signal input section 16 to the microcomputer 18 via the filter 17, the microcomputer 18 reads out lamp power W_L(F) corresponding to the lamp voltage V_L(F) from the table 19 and reads out values "a" and "b" corresponding to the dimming light amount of the dimming signal from the table 19a. Then, it derives lamp power W_L(d) according to a load power curve similar to the load power curve g1 at the full-lighting time by using the lamp voltage V_L(F), lamp power W_L(F) and values "a" and "b".
The microcomputer 18 supplies an output corresponding to the thus derived lamp power W_L(d) from the output terminal thereof to the operational amplifier 21 of the controller 15 via the filter circuit 20 as the reference voltage value V_S2.
The voltage value V_S1 of (V_L/N + r·I_L) obtained by superimposing the lamp voltage V_L/N on the voltage r·I_L generated by the lamp current I_L flowing through the resistor 9 is input from the connection node of the resistors 10 and 11 to the operational amplifier 21 of the controller 15.
The controller 15 compares the voltage value V_S1 with the reference voltage value V_S2 in the operational amplifier 21 and controls the switching duty of the switching element 5 of the voltage step-down chopper circuit 4 to set the voltage value V_S1 equal to the reference voltage value V_S2.
As a result, power supplied from the voltage step-down chopper circuit 4 to the discharge lamp 8 is controlled and set to power in the stable lighting region which corresponds to the dimming light amount of the dimming signal. For example, if the dimming signal has a dimming light amount of 50%, the lighting state of the discharge lamp 8 is controlled so that the discharge lamp will be lighted with the lamp power W_L(d) set at approximately equal to 60W in a range of the lamp voltage V_L(d) of approximately 80V to 96V according to the load power curve g2 similar to the load power curve g1. The brightness of the discharge lamp 8 at this time becomes 50% of the brightness at the full-lighting time.
Thus, power supplied to the discharge lamp 8 can be, of course, controlled according to power in the stable lighting region at the full-lighting time and can also be controlled according to power in the stable lighting region corresponding to a dimming light amount by adequately controlling the lamp voltage V_L at the dimming time.
The lighting device of the present embodiment can adequately perform the lamp power control operation according to a dimming signal. In addition, it is possible to derive target lamp power W_L(d) at the dimming time in a short period of time by using values "a" and "b" corresponding to a dimming light amount read out from the table 19. Therefore, the lighting device of the present embodiment can rapidly perform the lamp power control operation at the dimming time.
Further, in the lighting device of the present embodiment, the start lighting control operation of the discharge lamp 8 at the dimming time is performed by using the rated values like the start lighting control operation at the full-lighting time. That is, the controller 15 has switching means 22 for changing the output mode of the discharge lamp 8 in a period from the starting time thereof to the lighting start time from a rated output mode to a dimming output mode.
The switching means 22 sets the output mode into a rated output mode in which the discharge lamp 8 is started in a rated starting condition at the dimming start time to control the switching duty of the switching element 5 of the voltage step-down chopper circuit 4. The rated starting condition is a condition that the discharge lamp 8 is started to start the lighting operation with the rated value.
Then, when the lamp voltage of the discharge lamp 8 has reached preset voltage, the switching means 22 switches the output mode from the rated output mode to a dimming output mode in which it starts in the dimming start condition while the power characteristic of the dimming ratio corresponding to the dimming signal is maintained.
As a result, the controller 15 controls the switching duty of the switching element 5 of the voltage step-down chopper circuit 4 in the dimming output mode. The dimming start condition is a condition in which the discharge lamp 8 is started according to a dimming light amount and controlled to start the lighting operation.
That is, the controller 15 controls the voltage step-down chopper circuit 4 to start the discharge lamp 8 with the rated voltage and perform the lighting operation at the full-lighting time. Thus, as shown in FIG. 4A, the lamp voltage V_L satisfactorily rises. The lamp voltage V_L(F) shown in FIG. 4A indicates rated lamp voltage.
Further, the controller 15 controls the voltage step-down chopper circuit 4 by use of the switching means 22 at the dimming lighting time. The switching means 22 first sets the output mode to the rated output mode in which the discharge lamp is started in the rated starting condition to start the lighting operation of the discharge lamp 8. Then, when the lamp voltage V_L has reached preset voltage V_L1, it switches the output mode from the rated output mode to the dimming output mode in which the discharge lamp is started in the dimming start condition while the power characteristic according to the dimming light amount of the dimming signal is maintained.
As a result, as shown in FIG. 4B, the discharge lamp 8 is first controlled to be lighted with the rated voltage like the case of the full-lighting operation. Then, when the lamp voltage V_L has reached preset voltage V_L1, the dimming lighting operation is controlled according to the load power curve corresponding to the dimming light amount of the dimming signal from the dimming signal input section 16.
That is, the lighting operation of the discharge lamp 8 is controlled with lamp voltage V_L2 corresponding to the dimming light amount. As a result, the lighting device of the present embodiment can perform the control operation without delaying the rise time of the lamp voltage at the dimming lighting time. Therefore, there occurs no possibility that the discharge lamp is extinguished due to delay in the rise time of the lamp voltage.
On the other hand, as shown in FIG. 4C, when the discharge lamp 8 is not lighted with the rated voltage at the dimming lighting time, the rise characteristic of the lamp voltage becomes smooth and there occurs a possibility that the discharge lamp is extinguished due to delay in the rise time of the lamp voltage.
Further, since the lighting device of the present embodiment switches the output mode from the rated output mode to the dimming output mode with the preset voltage V_L1 lower than the lamp voltage V_L2 at the dimming time, there is no possibility that excessively high lamp power is applied to the discharge lamp 8 at the rise time of the lamp voltage.
As a result, the discharge lamp 8 can suppress damage given to the electrode to the lowest limit and suppress a variation in the brightness at the switching time from the rated output mode to the dimming output mode to the minimum.
Further, in the lighting device of the present embodiment, the controller 15 switches the control operation of the voltage step-down chopper circuit 4 from the dimming lighting control operation to the full lighting control operation when the discharge lamp 8 is extinguished in a state where the discharge lamp 8 is lighted in the dimming mode. Thus, the lighting device of the present embodiment can improve the condition of starting faults due to insufficient open voltage generated at the extinguishing time and suppress damage to the lamp electrode.
In the present embodiment, a case wherein the values "a" and "b" corresponding to the dimming light amount are previously set in the table 19 is explained, but this is not limitative. For example, the values can be derived by calculation based on the dimming light amount of a dimming signal.

(Second Embodiment)

In this embodiment, portions which are the same as those of the first embodiment are denoted by the same reference symbols and the detail explanation thereof is omitted.
As shown in FIG. 5, a discharge lamp lighting device of the present embodiment directly inputs a dimming signal of a PWM (pulse width modulation) signal from a dimming signal input section 16 to the dimming light input terminal of a microcomputer 181 without using the filter 17.
The microcomputer 181 converts an input dimming signal to DC voltage in the internal portion. The other functions of the microcomputer 181 are the same as those of the microcomputer 18 of the first embodiment.
Also, in the discharge lamp lighting device, the microcomputer 181 supplies a reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(F) which is power in the stable lighting region of a load power curve g1 at the input time of a full-lighting signal from the output terminal thereof to a controller 15 via a filter circuit 20.
Further, the microcomputer 181 supplies a reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(d) which is power in the stable lighting region of a load power curve which is similar to the load power curve g1 and derived according to values "a" and "b" corresponding to a dimming light amount at the input time of a dimming signal from the output terminal thereof to the controller 15 via the filter circuit 20.
Therefore, in the present embodiment, the controller 15 controls a voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(F) in the stable lighting region of the load power curve g1 at the full-lighting time. Further, at the dimming time, it controls the voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(d) in the stable lighting region of the load power curve which is similar to the load power curve g1 and derived according to the dimming light amount.
Thus, in the present embodiment, the same effect and operation as those of the first embodiment can be attained.

(Third Embodiment)

In this embodiment, portions which are the same as those of the former embodiments are denoted by the same reference symbols and the detail explanation thereof is omitted.
As shown in FIG. 6, a discharge lamp lighting device of the present embodiment adds a voltage value V_S1 of (V_L/N + r·I_L) obtained by superimposing lamp voltage V_L/N on voltage r·I_L generated by a lamp current I_L flowing through a resistor 9 and output from a connection node of resistors 10 and 11 with a reference voltage value V_S2 output from a microcomputer 18 via a filter circuit 20 and supplies the thus added voltage to a controller 151.
The controller 151 controls the switching duty of a switching element 5 of a voltage step-down chopper circuit 4 to set the added voltage of the voltage value V_S1 and reference voltage value V_S2 to preset constant voltage. The constant voltage set in the controller 151 is different at the full-lighting time and at the dimming time and varies according to the dimming degree at the dimming time. The other functions of the controller 15 are the same as those of the controller 15 explained in the first embodiment.
Also, in the discharge lamp lighting device, the microcomputer 18 supplies the reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(F) which is power in the stable lighting region of the load power curve g1 at the input time of a full-lighting signal from the output terminal thereof.
Further, the microcomputer 18 supplies the reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(d) which is power in the stable lighting region of a load power curve which is similar to the load power curve g1 and derived according to values "a" and "b" corresponding to a dimming light amount at the input time of a dimming signal from the output terminal thereof.
The reference voltage value V_S2 output from the output terminal of the microcomputer 18 is output via the filter circuit 20 and added with the voltage value V_S1 supplied from the connection node of the resistors 10 and 11. Then, the added voltage is supplied to the controller 151. The controller 151 controls the switching duty of the switching element 5 of a voltage step-down chopper circuit 4 to set the added voltage of the voltage value V_S1 and reference voltage value V_S2 to preset constant voltage.
Also, in the discharge lamp lighting device, the controller 151 controls the voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(F) in the stable lighting region of the load power curve g1 at the full-lighting time. Further, at the dimming time, it controls the voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(d) in the stable lighting region of the load power curve which is similar to the load power curve g1 and derived according to the dimming light amount.
Thus, in the present embodiment, the same effect and operation as those of the first embodiment can be attained.

(Fourth Embodiment)

In this embodiment, portions which are the same as those of the former embodiments are denoted by the same reference symbols and the detail explanation thereof is omitted.
As shown in FIG. 7, a discharge lamp lighting device of the present embodiment directly inputs a dimming signal of a PWM (pulse width modulation) signal from a dimming signal input section 16 to the dimming light input terminal of a microcomputer 181 without using the filter 17.
Like the second embodiment, the microcomputer 181 converts an input dimming signal to DC voltage in the internal portion.
Further, the discharge lamp lighting device of the present embodiment adds a voltage value V_S1 of (V_L/N + r·I_L) obtained by superimposing lamp voltage V_L/N on voltage r·I_L generated by a lamp current I_L flowing through a resistor 9 and output from a connection node of resistors 10 and 11 with a reference voltage value V_S2 output from the microcomputer 181 via a filter circuit 20 and supplies the thus added voltage to a controller 151.
Like the case of the third embodiment, the controller 151 controls the switching duty of a switching element 5 of a voltage step-down chopper circuit 4 to set the added voltage of the voltage value V_S1 and reference voltage value V_S2 to preset constant voltage.
Also, in the discharge lamp lighting device, the microcomputer 181 supplies the reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(F) which is power in the stable lighting region of a load power curve g1 at the input time of a full-lighting signal from the output terminal thereof.
Further, the microcomputer 181 supplies the reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(d) which is power in the stable lighting region of a load power curve which is similar to the load power curve g1 and derived according to values "a" and "b" corresponding to a dimming light amount at the input time of a dimming signal from the output terminal thereof.
The reference voltage value V_S2 output from the output terminal of the microcomputer 181 is output via the filter circuit 20 and added with the voltage value V_S1 from the connection node of the resistors 10 and 11. Then, the added voltage is supplied to the controller 151. The controller 151 controls the switching duty of the switching element 5 of the voltage step-down chopper circuit 4 to set the added voltage of the voltage value V_S1 and reference voltage value V_S2 to preset constant voltage.
Also, in the discharge lamp lighting device, the controller 151 controls the voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(F) in the stable lighting region of the load power curve g1 at the full-lighting time. Further, at the dimming time, it controls the voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(d) in the stable lighting region of the load power curve which is similar to the load power curve g1 and derived according to the dimming light amount.
Thus, in the present embodiment, the same effect and operation as those of the first embodiment can be attained.

(Fifth Embodiment)

In the present embodiment, a discharge lamp lighting device which AC-lights a discharge lamp 8 by using a polarity inverting circuit is explained. Portions which are the same as those of the former embodiments are denoted by the same reference symbols and the detail explanation thereof is omitted.
As shown in FIG. 8, the discharge lamp lighting device of the present embodiment includes a diode 7 having a cathode terminal connected to one end of an inductor 6 and an anode terminal connected to one end of a resistor 9. A series circuit of resistors 10, 11 and a capacitor 12 are connected between the other end of the inductor 6 and the other end of the resistor 9.
The discharge lamp lighting device of the present embodiment has a polarity inverting circuit 23 connected to the series circuit of the resistors 10, 11. The polarity inverting circuit 23 includes a series circuit of a pair of switching elements 24, 25 which are each configured by an FET (field effect transistor) and a series circuit of a pair of switching elements 26, 27 which are each configured by an FET and the above two series circuits are connected in parallel with each other.
The polarity inverting circuit 23 has a series circuit of an igniter 28 which generates a high-voltage pulse at the starting time and the discharge lamp 8 connected between a connection node of the pair of switching elements 24, 25 and a connection node of the pair of switching elements 26, 27.
A voltage value V_S1 generated from the connection node of the resistors 10, 11 is supplied to an operational amplifier 21 of a controller 15 via an output line 30 and a V_L input terminal of a microcomputer 18. The microcomputer 18 derives a detected value V_L of lamp voltage from the voltage value V_S1 input to the V_L input terminal and performs the same process as described in the former embodiments by using the detected value V_L.
The switching elements 24, 25, 26, 27 of the polarity inverting circuit 23 are switching-driven by a drive circuit 29. At the lighting time, the polarity inverting circuit 23 sets the switching elements 24, 27 in the ON state in a half cycle by use of the drive circuit 29 and sets the switching elements 25, 26 in the OFF state to pass a lamp current through the discharge lamp 8 in a direction indicated by an arrow A of solid lines in FIG. 8. Then, in a next half cycle, it sets the switching elements 25, 26 in the ON state by use of the drive circuit 29 and sets the switching elements 24, 27 in the OFF state to pass a lamp current through the discharge lamp 8 in a direction indicated by an arrow B of dotted lines in FIG. 8. Thus, the lighting device of the present embodiment AC-lights the discharge lamp 8.
Also, in the discharge lamp lighting device, the microcomputer 18 supplies a reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(F) which is power in the stable lighting region of a load power curve g1 from the output terminal thereof to the controller via a filter circuit 20 at the input time of a full-lighting signal.
Further, at the input time of a dimming signal, the microcomputer 18 supplies a reference voltage value V_S2 used to control the lighting operation of the discharge lamp 8 with lamp power W_L(d) which is power in the stable lighting region of a load power curve which is similar to the load power curve g1 and derived by using values "a" and "b" corresponding to a dimming light amount from the output terminal thereof to the controller 15 via the filter circuit 20.
Therefore, also, in the present embodiment, the controller 15 controls a voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(F) in the stable lighting region of the load power curve g1 at the full-lighting time. Further, at the dimming time, it controls the voltage step-down chopper circuit 4 to light the discharge lamp 8 with the lamp power W_L(d) in the stable lighting region of the load power curve which is similar to the load power curve g1 and derived according to the dimming light amount.
Thus, in the present embodiment, the same effect and operation as those of the first embodiment can be attained.

(Sixth Embodiment)

In the present embodiment, an illumination apparatus using one of the discharge lamp lighting devices which are explained in the first to fifth embodiments is explained.
As shown in FIG. 9, the illumination apparatus has a discharge lamp lighting device 100 and illumination apparatus main body 101 which are separately arranged. The illumination apparatus main body 101 includes a concave-shaped shade portion 101a having an inner surface formed of a reflection surface and a discharge lamp 102 is loaded on the central portion of the shade portion 101a. The discharge lamp lighting device 100 has the same configuration as that of one of the discharge lamp lighting devices described in the first to fourth embodiments.
The discharge lamp lighting device 100 used in the above illumination apparatus lights the discharge lamp 102 with lamp power W_L(F) in the stable lighting region of a load power curve g1 at the full-lighting time. Further, at the dimming time, it lights the discharge lamp 102 with lamp power W_L(d) in the stable lighting region of a load power curve which is similar to the load power curve g1 and derived according to the dimming light amount.
Thus, power supplied to the discharge lamp 102 is controlled by use of power in the stable lighting region at the full-lighting time and is also controlled by use of power in the stable lighting region corresponding to the dimming light amount by adequately controlling lamp voltage V_L at the dimming time. Further, at the dimming time, target lamp power can be derived by use of values "a" and "b" corresponding to the dimming light amount read out from a table in a short period of time and, as a result, the lamp power control operation can be rapidly performed.

Claims

A discharge lamp lighting device having a dimming signal input section (16) to which a full-lighting signal and dimming signal are input, a chopper circuit (4) which adjusts power supplied to a discharge lamp (8) and a lamp voltage detecting circuit (13, 14) which detects lamp voltage applied to the discharge lamp (8), characterized by comprising:
a control circuit (15, 18) which controls an output of the chopper circuit (4) according to a dimming signal and lamp voltage to control power of the discharge lamp (8),
wherein the control circuit (15, 18) includes means (18) for setting a reference voltage value according to one of a full-lighting signal and dimming signal from the dimming signal input section (16) and lamp voltage detected by the lamp voltage detecting circuit (13, 14), a first detecting section (10, 11) which is connected in parallel with the discharge lamp (8) and detects voltage corresponding to lamp voltage, a second detecting section (9) which is connected in series with the discharge lamp (8) and detects voltage corresponding to a lamp current, output means (30) for outputting voltage equal to the sum of voltages detected by the detecting sections (9; 10, 11) and output control means (15) for controlling an output of the chopper circuit (4) to set the sum voltage value output from the output means (30) equal to the reference voltage value, and the discharge lamp is set to have a stable lighting region in which rated lamp power at each of full-light lighting time and dimming lighting time is ensured according to a lamp voltage region of preset width at each of full-lighting time and dimming time.
The discharge lamp lighting device according to claim 1, characterized in that the control circuit (15, 18) is previously set to have a load power curve having a stable lighting region with respect to the discharge lamp (8) based on the lamp voltage at the full-lighting time detected by the lamp voltage detecting circuit (13, 14), and means (18) for setting the reference voltage value is set to have a table (19) in which values "a" corresponding to lamp voltages which correspond to dimming light amounts and values "b" corresponding to lamp currents which correspond to dimming light amounts are set, sets a reference voltage value by use of lamp voltage detected by the lamp voltage detecting circuit (13, 14) and corresponding ones of the values "a" and "b" in the table (19) based on inputting of a dimming signal and sets a load power curve similar to the load power curve at the full-lighting time in a dimming mode.
The discharge lamp lighting device according to one of claims 1 and 2, characterized in that the control circuit (15, 18) includes switching means (22) for setting an output mode to a rated output mode in which the discharge lamp is started in a rated starting condition at dimming start time and switching the output mode from the rated output mode to a dimming output mode in which the discharge lamp is started in a dimming start condition while a power characteristic corresponding to a dimming light amount of the dimming signal is maintained when the lamp voltage of the discharge lamp (8) has reached preset voltage.
An illumination apparatus having a discharge lamp, characterized by comprising:
a discharge lamp lighting device (100) described in one of claims 1 to 3, and

an illumination main body (101) having the discharge lamp (102) mounted thereon.