JP2004362942A - Discharge lamp lighting device and lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of properly restraining rush current generated when a power source is turned on again in a short period. <P>SOLUTION: An inverter control means 20 determines whether an input power source should be turned off or not depending on an output voltage of a direct-current power source detected at a voltage detection means 19, and when it determines to turn off the input power source, an operation of an inverter circuit 23 is stopped before the voltage of smoothing capacitors C2, C3, lowering in compliance with the turn-off of the input power of the direct-current power source, becomes lower than the voltage of the direct-current power source at a normal operation. By the above, the voltage of the smoothing capacitors C2, C3 of a boosting chopper circuit 18 is maintained, and the rush current, generated when the power source is turned on again, is prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device and an illuminating device for lighting a discharge lamp at a high frequency.
[0002]
2. Description of the Related Art Generally, a discharge lamp is operated by a high frequency power supply. This is because, when the discharge lamp is turned on with a high-frequency power supply, flickering can be reduced, the luminous efficiency can be improved, and the time until lighting can be shortened. A discharge lamp lighting device for lighting a discharge lamp at a high frequency converts a DC power supply into a high-frequency AC power supply with an inverter circuit and supplies the discharge lamp with a high-frequency power supply. Then, a discharge lamp lighting device including a boost chopper circuit at a stage preceding the inverter circuit is used to suppress a harmonic component of the input current.
[0003]
In a discharge lamp lighting device including a boost chopper circuit, an inrush current suppression circuit is provided to suppress an inrush current when power is turned on. As the inrush current suppressing circuit, there is a circuit in which a resistor and a switch are connected in parallel and a circuit using a thermistor. When the resistor and the switch are connected in parallel, when the power is turned on, power is input via the resistor to suppress the rush current, and when the discharge lamp is lit, the switch is turned on and the power is supplied by bypassing the resistor. In the case of using a thermistor, the thermistor is connected in series to an input terminal of a power supply, and utilizes the characteristics of a thermistor that has a large resistance value when the temperature is low and a small resistance value when the temperature is high. That is, when the power is turned on, the inrush current is suppressed by a large resistance value because the temperature of the thermistor is low, and the resistance value becomes small because the temperature of the thermistor increases during lighting, and power loss due to the resistance can be reduced.
[0004]
In such an inrush current suppression circuit, if the power is turned on again within a short time after the power is turned off, the inrush current may not be able to be suppressed. That is, in a rush current suppression circuit in which a resistor and a switch are connected in parallel, a control circuit that turns off the switch instantaneously when the power is cut off is necessary. If it is turned on again, the inrush current cannot be suppressed. In addition, in a rush current suppression circuit using a thermistor, if power is turned on again before the temperature of the thermistor decreases, the rush current cannot be suppressed because the resistance value of the thermistor is small.
[0005]
Therefore, there is a configuration in which a series circuit of two thermistors and a switch element is connected in parallel, and the switch element is controlled so that the lower temperature thermistor operates when the power is turned on (for example, Patent Document 1). reference).
[0006]
[Patent Document 1] JP-A-2002-252921 (FIG. 1)
[0007]
However, in such an inrush current suppressing circuit, the detection of the temperature of the thermistor and the control of the switch element are required, so that the circuit configuration tends to be complicated. Therefore, in spite of using a thermistor, a control circuit for turning off the switch is required like a rush current suppressing circuit in which a resistor and a switch are connected in parallel, and there is almost no advantage.
[0008]
An object of the present invention is to provide a discharge lamp lighting device and a lighting device that can appropriately suppress an inrush current even when input power is turned on again in a short time.
[0009]
According to a first aspect of the present invention, there is provided a discharge lamp lighting device comprising: a boost chopper circuit for boosting a DC power supply to a predetermined DC voltage; and a serial connection between the DC power supply and the boost chopper circuit. A thermistor connected to suppress a rush current when the power is turned on; voltage detection means for detecting an output voltage of the DC power supply; and a discharge lamp which converts a DC voltage of a smoothing capacitor of the boost chopper circuit into an alternating current to an alternating current. An inverter circuit for supplying to the load circuit; and determining whether or not the input power is to be cut off based on the voltage detected by the voltage detection means. Inverter control means for stopping the operation of the inverter circuit within a time when the voltage of the decreasing smoothing capacitor does not fall below the DC power supply voltage during normal operation. It is characterized in.
[0010]
In the present invention and the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified. The DC power supply also includes a DC power supply obtained by rectifying an AC power supply. The boost chopper circuit boosts a DC power supply to a predetermined voltage. For example, the reactor and the smoothing capacitor are connected in series via a diode for preventing backflow, and a switch element is connected in parallel to a series circuit of the diode and the smoothing capacitor. Then, by storing the energy stored in the reactor when the switching element is turned on to the smoothing capacitor when the switching element is turned off, an output voltage higher than the input voltage can be obtained. Further, since the input current flows in all phases of the input voltage, input current harmonics are suppressed. The smoothing capacitor is configured by connecting two capacitors of the same capacity in series, and a discharge lamp of a load circuit is connected to a connection point of the two smoothing capacitors.
[0011]
The thermistor is connected in series between the DC power supply and the boost chopper circuit, and suppresses an inrush current when the power is turned on. The thermistor has the characteristic that the resistance is large when the temperature is low and decreases when the temperature is high.When the power is turned on, the temperature of the thermistor is low and the rush current is suppressed with a large resistance value, During lighting, the temperature of the thermistor rises, so that the power is supplied with a small resistance value and little current loss.
[0012]
The voltage detecting means detects an output voltage of the DC power supply. For example, a resistor is connected in parallel to an output terminal of the DC power supply, and the voltage is detected at both ends of the resistor. The voltage detected by the voltage detection means is input to the inverter control means and it is determined whether or not the DC power supply is shut off.
[0013]
The inverter circuit has two switch elements, receives the DC voltage of the smoothing capacitor of the boost chopper circuit as input, and controls the two switch elements to be turned on / off by inverter control means to supply an AC voltage to the output side. A load circuit is connected to the output side of the inverter circuit, and an AC voltage output from the inverter circuit is applied to the discharge lamp.
[0014]
The discharge lamp is a mercury lamp, a metal halide lamp, a high-pressure sodium lamp, or the like, and also includes a ceramic discharge lamp using an alumina tube or the like as an arc tube. The arc tube is filled with at least a rare gas such as neon Ne or argon Ar as a discharge medium.
[0015]
The inverter control means controls on and off of two switch elements of the inverter circuit while the discharge lamp is lit, and supplies an AC voltage to the discharge lamp. Further, it is determined whether or not the input power is cut off based on the voltage detected by the voltage detecting means.
[0016]
When it is determined that the input power supply is cut off, the on / off control of the switch element of the inverter circuit is stopped and the switch element is turned off. This operation is performed within a time period in which the voltage of the smoothing capacitor, which decreases due to the interruption of the input power of the DC power supply, does not become lower than the DC power supply voltage which is the input voltage of the boost chopper circuit in the normal operation. Thus, even if the input power is turned on again before the temperature of the thermistor decreases (before the resistance of the thermistor returns), the rush current is limited because the voltage remains in the smoothing capacitor.
[0017]
According to the present invention, when it is detected that the input power supply has been cut off, the inverter control means stops the operation of the switch element of the inverter circuit. The voltage of the capacitor is maintained at substantially the same voltage as when the discharge lamp is turned on, and the voltage drops very slowly. Therefore, even if the temperature of the thermistor decreases and the input power is turned on again before the resistance value returns to the original value, the rush current is limited because the voltage remains in the smoothing capacitor.
[0018]
A lighting device according to a second aspect of the present invention includes the discharge lamp lighting device according to the first aspect, a discharge lamp that is lit by the discharge lamp lighting device, and a fixture main body to which the discharge lamp is mounted. It is a feature. According to the present invention, it is possible to obtain a lighting device that can prevent an inrush current even when input power is cut off and input power is turned on again within a short time.
[0019]
(First Embodiment) FIG. 1 is a configuration diagram of a discharge lamp lighting device according to a first embodiment of the present invention. The DC power supply 11 is provided with a light on / off switch 14 for turning on / off the discharge lamp 13 of the load circuit 12. When the light on / off switch 14 is turned on, a DC voltage is output from an output terminal of the DC power supply 11. The DC power supply 11 is configured to rectify a commercial AC power supply 15 with a rectifier 16 to obtain a DC voltage. A DC voltage from the DC power supply 11 is applied to a boost chopper circuit 18 via a thermistor 17.
[0020]
The thermistor 17 has a characteristic that the resistance is large when the temperature is low, and the resistance is small when the temperature is high. When the power is turned on, the inrush current is suppressed with a large resistance because the temperature of the thermistor 17 is low. During lighting of the electric lamp 13, the temperature rises due to the DC current, resulting in a small resistance value, and during lighting of the discharge lamp 3, power is supplied with little current loss.
[0021]
A voltage detecting means 19 for detecting an output voltage of the DC power supply 11 is provided at a stage subsequent to the DC power supply 11, and the output voltage of the DC power supply 11 detected by the voltage detecting means 19 is input to the inverter control means 20. The inverter control means 20 monitors the power supply of the DC power supply 11 based on the voltage detected by the voltage detection means 19.
[0022]
The boost chopper circuit 18 boosts the output voltage from the DC power supply 11 to a predetermined voltage, and includes a capacitor C1, a reactor L1, a diode D1, two smoothing capacitors C2 and C3, a switch element 21, and a control unit 22. Is done. The reactor L1 is connected in series to two smoothing capacitors C2 and C3 via a diode D1 for backflow prevention, branches off from the reactor L1, and switches in parallel with a series circuit of the diode D1 and the smoothing capacitors C2 and C3. 21 are connected.
[0023]
Then, the control unit 22 controls the on / off of the switch element 21, stores the electric energy stored in the reactor L1 in the smoothing capacitors C2 and C3, and boosts the DC voltage. The voltage of the smoothing capacitors C2 and C3 becomes the output voltage of the boost chopper circuit 18. The two smoothing capacitors C2 and C3 are capacitors having the same capacity, and the discharge lamp 13 of the load circuit 12 is connected to a connection point between the two smoothing capacitors C2 and C3.
[0024]
The inverter circuit 23 has two switch elements S1 and S2 in which diodes D2 and D3 are connected in parallel, respectively, and inputs the DC voltage of the smoothing capacitors C2 and C3 of the boost chopper circuit 18. The two switch elements S1 and S2 are on / off controlled by the inverter control means 20 to supply an AC voltage to the discharge lamp 13 of the load circuit 12 on the output side. Further, when the voltage detected by the voltage detecting means 19 decreases, the inverter control means 20 determines that the power supply of the DC power supply 11 has been cut off, and stops the operation of the switch elements S1 and S2 of the inverter circuit 23.
[0025]
The load circuit 12 includes a capacitor C4 and a reactor L3 connected in parallel to the discharge lamp 13. The discharge lamp 13 is a mercury lamp, a metal halide lamp, a high-pressure sodium lamp, or the like, and also includes a ceramic discharge lamp using an alumina tube or the like as an arc tube. The arc tube is filled with at least a rare gas such as neon Ne or argon Ar as a discharge medium.
[0026]
Next, the operation will be described. Assuming that the light-on / off switch 14 is turned on and the power is turned on, the rectifier 16 of the DC power supply 11 rectifies the AC voltage to generate a DC voltage, which is input to the boost chopper circuit 18 via the thermistor 17. When the temperature of the thermistor 17 is low, the resistance value is large, and thus the occurrence of an inrush current is prevented by the thermistor 17.
[0027]
The DC voltage boosted by the boost chopper circuit 18 is input to the switching elements S1 and S2 of the inverter circuit 23. The switching elements S1 and S2 are ON / OFF controlled by the inverter control means 20, and supply AC power to the discharge lamp 13 of the load circuit 12. First, the inverter control means 20 controls on / off of the switch element S1 with the switch element S2 turned off, and controls on / off of the switch element S2 with the switch element S1 turned off. This is repeated at a predetermined cycle.
[0028]
FIG. 2 is an explanatory diagram of a circuit formed when the switch element S1 is turned on and off with the switch element S2 turned off. When the switch element S1 is on, a circuit shown by an arrow (1) in FIG. 2A is formed, and when the switch element S1 is off, a circuit shown by an arrow (2) in FIG. 2B is formed. You.
[0029]
FIG. 3 is an explanatory diagram of a circuit formed when the switching element S2 is turned on and off with the switching element S1 turned off. When the switch element S2 is on, a circuit shown by an arrow (3) in FIG. 3A is formed, and when the switch element S2 is off, a circuit shown by an arrow (4) in FIG. 3B is formed. You.
[0030]
FIG. 4 is a characteristic diagram of the currents I1 and I2 flowing through the switch elements S1 and S2 and the load current IL flowing through the discharge lamp 13 as a load. The current I1 flowing through the switch element S1 is a current on the positive side of the load current IL, and the current from the smoothing capacitor C2 shown in FIG. 2A and the reactor shown in FIG. This is the discharge current of the stored energy of L3, and the magnitude of the load current IL can be changed by changing the ratio (duty ratio). Similarly, the current I2 flowing through the switch element S2 is a current on the negative side of the load current IL, and the current from the smoothing capacitor C3 shown in FIG. 3A and the current shown in FIG. And the discharge current of the energy stored in the reactor L3, and the magnitude of the load current IL can be changed by changing the ratio (duty ratio).
[0031]
When a DC voltage is supplied from the DC power supply 11, the discharge lamp 13 is in a lighting state by the above-described operation. During such an operation, the resistance of the thermistor 17 is reduced due to self-heating. In this state, if the input power supply of the DC power supply 11 is cut off, the voltage detected by the voltage detection means 19 decreases, and the inverter control means 20 detects that the input power supply of the DC power supply 11 is cut off. When the inverter control means detects that the input power is turned off, it stops the on / off control of the switch elements S1 and S2 of the inverter circuit 23 and turns off the switch elements S1 and S2. In this case, the inverter control means 20 operates the inverter circuit 23 within a time period in which the voltage of the smoothing capacitors C2 and C3, which decreases due to the cutoff of the input power of the DC power supply 11, does not become lower than the input voltage of the boost chopper circuit 18 in the normal operation. Will be stopped.
[0032]
When the switch elements S1 and S2 are turned off, the inverter circuit 23 stops, so that the electric energy stored in the smoothing capacitors C2 and C3 becomes difficult to be released, and the voltage of the smoothing capacitors C2 and C3 drops very slowly. Become. Therefore, even if the DC power supply 11 is turned on again before the resistance value of the thermistor 17 recovers, a voltage higher than the input voltage of the boost chopper circuit 18 in the normal operation remains in the smoothing capacitors C2 and C3. Is restricted.
[0033]
According to the first embodiment, when the input power supply of the DC power supply 11 is cut off, the switching elements S1 and S2 of the inverter circuit 23 are turned off, so that the voltages of the smoothing capacitors C2 and C3 of the boost chopper circuit 18 are reduced. The input voltage of the step-up chopper circuit 18 during normal operation is maintained at or above the input voltage. Therefore, even if the DC power supply 11 is turned on again until the resistance value of the thermistor 17 recovers, no inrush current flows into the smoothing capacitors C2 and C3 of the boost chopper circuit 18, so that generation of inrush current can be prevented. .
[0034]
(Second Embodiment) FIG. 5 is an explanatory view of a lighting device according to a second embodiment of the present invention. The discharge lamp lighting device 24 according to the first embodiment constitutes an illumination device together with the fixture body 25 to which the discharge lamp 13 is mounted. As shown in FIG. 5, the discharge lamp 13 is mounted on the socket 26 of the appliance body 25 and is turned on by the discharge lamp lighting device 24. The light from the lit discharge lamp 13 is reflected by the reflector 27 on the front side and is emitted through the front glass 28. According to the lighting device of the second embodiment, a lighting device having the effect of the discharge lamp lighting device 24 of the first embodiment can be obtained.
[0035]
According to the first aspect of the present invention, when it is detected that the input power is cut off, the operation of the switch element of the inverter circuit is stopped, so that the electric charge accumulated in the smoothing capacitor is released. As a result, the voltage of the smoothing capacitor is maintained at substantially the same voltage as the voltage when the discharge lamp is turned on, and the voltage decreases very slowly. Therefore, even if the temperature of the thermistor decreases and the input power is turned on again before the resistance value returns to the original value, the rush current can be prevented because the voltage remains in the smoothing capacitor.
[0036]
According to the invention of claim 2, it is possible to obtain a lighting device that can prevent an inrush current even when the input power is cut off and the input power is turned on again within a short time.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a discharge lamp lighting device according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of a circuit formed when the switch element S1 of the inverter circuit according to the first embodiment of the present invention is turned on and off with the switch element S2 turned off.
FIG. 3 is an explanatory diagram of a circuit formed when the switch element S2 of the inverter circuit according to the first embodiment of the present invention is turned off with the switch element S1 turned off.
FIG. 4 is a characteristic diagram of currents I1 and I2 flowing through switch elements S1 and S2 of the inverter circuit and a load current IL flowing through a discharge lamp as a load according to the first embodiment of the present invention.
FIG. 5 is an explanatory diagram of a lighting device according to a second embodiment of the present invention.
[Description of Signs] 11 ... DC power supply, 12 ... Load circuit, 13 ... Discharge lamp, 14 ... Light on / off switch, 15 ... AC power supply, 16 ... Rectifier, 17 ... Thermistor, 18 ... Boost chopper circuit, 19 ... Voltage detecting means , 20 ... Inverter control means, 21 ... Switch element, 22 ... Control means, 23 ... Inverter circuit, 24 ... Discharge lamp lighting device, 25 ... Equipment body, 26 ... Socket, 27 ... Reflector, 28 ... Front glass

Claims (2)

A boost chopper circuit for boosting a DC power supply to a predetermined DC voltage;
A thermistor connected in series between the DC power supply and the boost chopper circuit for suppressing an inrush current when the power is turned on;
Voltage detection means for detecting an output voltage of the DC power supply;
An inverter circuit that converts a DC voltage of a smoothing capacitor of the boost chopper circuit into an AC voltage and supplies the AC voltage to a load circuit including a discharge lamp;
It is determined whether or not the input power is cut off based on the voltage detected by the voltage detection means, and when it is determined that the input power is cut off, the voltage of the smoothing capacitor, which decreases with the input power cut off of the DC power supply, is normally Inverter control means for stopping the operation of the inverter circuit within a time period during which the voltage does not fall below the DC power supply voltage during operation;
A discharge lamp lighting device comprising: A discharge lamp lighting device according to claim 1;
A discharge lamp lit by the discharge lamp lighting device;
An appliance body to which the discharge lamp is attached;
A lighting device comprising:

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