JP2011028919A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of protecting a circuit by preventing excessive power supply when a low impedance component is connected to the output side of a power conversion circuit and capable of protecting the circuit also from an overvoltage after the start of a starting mode. <P>SOLUTION: A determining section 26 determines whether a detected voltage detected by a voltage detecting means 21 from an optional point of a preheating mode of the power conversion circuit 15 is lower than a predetermined first threshold voltage. The determining section 26 determines whether the detected voltage detected by the voltage detecting means 21 from an optional point after the start of the starting mode of the power conversion circuit 15 exceeds a predetermined second threshold voltage. When determining section determines that the detected voltage is lower than the first threshold voltage and the detected voltage exceeds the predetermined second threshold voltage, an oscillation control section 25 stops the power conversion circuit 15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device including a power conversion circuit that converts a DC voltage and supplies it to a discharge lamp.

  Conventionally, for example, a discharge lamp lighting device for lighting a discharge lamp rectifies a commercial AC power supply, and then converts the rectified input voltage into a DC voltage boosted by a power factor correction circuit such as a boost chopper circuit, An inverter circuit that turns on a discharge lamp by converting a DC voltage output from a DC power source into a high-frequency voltage, and a resonance circuit (main circuit) such as an LC resonance circuit that controls electric power supplied from the inverter circuit ing. The inverter circuit includes, for example, a half-bridge type having a pair of switching elements, and performs switching operation by controlling the switching elements by a drive circuit, and discharges a high-frequency voltage of a predetermined frequency via the LC resonance circuit. It can be applied to the lamp.

  In such a discharge lamp lighting device, for example, the discharge lamp voltage may become an overvoltage in an abnormal state such as the end of life or non-lighting of the discharge lamp, and if such an overvoltage continues, there is a possibility of adversely affecting the circuit. There is. Therefore, when the discharge lamp voltage is detected and the detected voltage exceeds a predetermined threshold voltage, the operation of the inverter circuit is stopped by stopping the switching operation of the switching element by the drive circuit. A configuration for protection is known (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2004-273430 (page 5-9, FIG. 1)

  In the discharge lamp, tracking may occasionally occur when the impedance in the output terminal decreases.

  However, the above-described discharge lamp lighting device has a problem that even if an overvoltage can be detected, it is not easy to prevent excessive power supply when the discharge lamp voltage is low.

  The present invention has been made in view of such points, and prevents excessive power supply when a low-impedance component is connected to the output side of the power conversion circuit, thereby enabling circuit protection and starting mode. An object of the present invention is to provide a discharge lamp lighting device capable of circuit protection against overvoltage after starting.

  A discharge lamp lighting device according to claim 1; a DC power source that outputs a DC voltage; a preheating mode for preheating the discharge lamp, a starting mode for starting the discharge lamp, and a lighting mode for controlling lighting of the discharge lamp A power conversion circuit that has at least one switching element, converts a DC voltage from a DC power source into a high-frequency voltage and supplies it to a discharge lamp; detects a detection voltage corresponding to the discharge lamp voltage Voltage detection means; determining whether the detection voltage detected by the voltage detection means from an arbitrary point in the preheating mode of the power conversion circuit is lower than a predetermined first threshold voltage; and optionally after starting the start mode of the power conversion circuit The detection voltage detected by the voltage detection means from the point exceeds a predetermined second threshold voltage that is greater than the predetermined first threshold voltage. Determining means for determining whether or not; the driving of the power conversion circuit is controlled, and the determination means determines that the detected voltage is lower than a predetermined first threshold voltage; Control means for stopping the power conversion circuit when it is determined that the threshold voltage is exceeded.

  The DC power supply may be, for example, one that obtains a DC voltage by a power factor correction circuit such as a boost chopper circuit after rectifying the AC voltage, or may be a battery power supply or a capacitor.

  The power conversion circuit includes, for example, an inverter circuit having a pair of switching elements and a resonance circuit.

  The voltage detection means corresponds to the discharge lamp voltage by connecting, for example, a series circuit of a plurality of resistors in parallel with the discharge lamp on the power conversion circuit side, for example, a configuration for detecting a proportional detection voltage is used. It is not limited to this.

  For example, a comparator (comparator) that inputs the set first threshold voltage or the second threshold voltage and the detection voltage detected by the voltage detection unit is used as the determination unit.

  The control means can stop the operation of the power conversion circuit, for example, by stopping the switching of the switching element of the inverter circuit of the power conversion circuit.

  In the discharge lamp lighting device according to the second aspect, the voltage detection means detects the detection voltage by a resistance voltage division in which a voltage division ratio is reduced as the electric potential increases.

  To reduce the voltage division ratio as the potential is higher means to set the resistance value of the resistor on the high potential side smaller than the resistance value of the resistor on the low potential side.

  According to the discharge lamp lighting device of the first aspect, it is determined whether or not the detected voltage corresponding to the discharge lamp voltage detected by the voltage detecting means from an arbitrary point in the preheating mode of the power conversion circuit is lower than the predetermined first threshold voltage. Whether the detection voltage determined by the determination means and detected by the voltage detection means from an arbitrary point after the start mode of the power conversion circuit has started exceeds a predetermined second threshold voltage larger than the predetermined first threshold voltage. When the determination means determines that the detection voltage is lower than the predetermined first threshold voltage and when it is determined that the detection voltage exceeds the predetermined second threshold voltage, the control means Stopping the power conversion circuit prevents excessive power supply from the preheating mode when a low impedance component is connected to the output side of the power conversion circuit Together allowing circuit protection Te, after the start of the start mode is enabled even circuit protection against overvoltages.

  According to the discharge lamp lighting device of the second aspect, in addition to the effect of the discharge lamp lighting device of the first aspect, the voltage detecting means detects the detected voltage by the resistance voltage division with a smaller voltage dividing ratio as the potential is higher. By doing so, the voltage dividing ratio of the discharge lamp voltage can be optimized, the voltage detecting means can be downsized, and the influence of noise from the surroundings when downsized can be reduced.

It is a circuit diagram of a discharge lamp lighting device showing an embodiment of the present invention. (a) is a graph showing the discharge lamp voltage from preheating of the discharge lamp lighting device to after starting, and (b) is an explanatory diagram showing the timing of start of judgment by the judging means of the same discharge lamp lighting device. It is a graph which shows the relationship between the detection voltage and threshold voltage of a discharge lamp lighting device same as the above. It is a perspective view of the lighting fixture provided with the discharge lamp lighting device same as the above.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  Fig. 1 is a circuit diagram of the discharge lamp lighting device, Fig. 2 (a) is a graph showing the discharge lamp voltage from preheating to after starting of the discharge lamp lighting device, and Fig. 2 (b) is a determination means of the discharge lamp lighting device. FIG. 3 is a graph showing the relationship between the detection voltage of the discharge lamp lighting device and the threshold voltage, and FIG. 4 is a perspective view of a lighting fixture equipped with the discharge lamp lighting device.

  As shown in FIG. 1, a discharge lamp lighting device 10 which is a hot cathode type discharge lamp lighting device as an electronic ballast has a DC output (DC voltage) from the DC power source 11 at a high frequency on the output side of the DC power source 11. A power conversion circuit 15 including an inverter circuit 13 that converts and outputs an AC voltage and a resonance circuit 14 that outputs a voltage corresponding to the output frequency of the inverter circuit 13 is electrically connected, and the output of the power conversion circuit 15 A discharge lamp FL such as a hot cathode fluorescent lamp as a load is detachably mounted on the side. The discharge lamp lighting device 10 includes a control element 16 that controls the inverter circuit 13 and the like. The control element 16 includes a drive element 17 that is a driver unit for driving the inverter circuit 13 of the power conversion circuit 15. Electrically connected.

  The DC power supply 11 rectifies commercial AC power supply such as 100V to 242V by a full-wave rectifier such as a bridge diode, and then boosts and smoothes it by a power factor improvement circuit (not shown) such as a boost chopper circuit to output a DC voltage. To do.

  The inverter circuit 13 is a so-called half-bridge type in which field effect transistors Q1 and Q2 as switching elements are connected in series.

  The field effect transistors Q1 and Q2 have their gate terminals, which are control terminals, electrically connected to the drive element 17, and are turned on and off by signals supplied from the drive element 17.

  The resonance circuit 14 includes a series circuit of a DC cut capacitor C1 electrically connected to both ends of the field effect transistor Q2 and a primary winding of a resonance inductance L, which is a ballast choke as an inductor, and this resonance. A resonance capacitor C2, which is a capacitor in parallel with the discharge lamp FL, is electrically connected to the output side of the primary winding of the inductance L. Further, on the output side of the resonance circuit 14, voltage detection means 21 for detecting, for example, a proportional detection voltage VCL corresponding to the discharge lamp voltage VL is electrically connected in parallel with the discharge lamp FL.

  The voltage detection means 21 includes a series circuit of resistors R1, R2, R3, and R4. A capacitor C3 is electrically connected to a connection point between the resistors R3 and R4, and a diode D1 is connected to the capacitor C3. , D2 and a series circuit of resistors R5 and R6 are electrically connected to the cathode side of the diode D2. The connection points of these resistors R5 and R6 are electrically connected to the control element 16 side.

  The resistors R1 to R3 are set so that the resistance value of the resistor R1 is the smallest and the resistance value of the resistor R3 is the largest. That is, in the voltage detecting means 21, the resistance values of the resistors R1 to R3 are set so that the voltage dividing ratio of the discharge lamp voltage VL becomes smaller as the electric potential becomes higher. The resistor R2 may have a resistance value equal to that of the resistor R3 or a resistance value smaller than that of the resistor R3 as long as the resistance value is larger than that of the resistor R1.

  In the discharge lamp FL, a preheating circuit (not shown) is connected to each filament FLa, FLb.

  The control element 16 is, for example, an IC (integrated circuit), a power factor improvement control unit (not shown) connected to the power factor improvement circuit of the DC power supply 11, and an inverter circuit based on the operation (lighting) state of the discharge lamp FL. An oscillation control unit 25 as a control means for generating and outputting to the drive element 17 a frequency signal P for controlling the operation of the 13 field effect transistors Q1, Q2, and a detected voltage VCL detected via the voltage detection means 21 Is compared with a predetermined first threshold voltage VTH1 and a second threshold voltage VTH2 (FIG. 3), and a determination unit 26 as a state detection unit as a determination unit for determining which is larger (smaller) It is prepared as one.

  Note that that the control element 16 integrally includes the power factor correction control unit, the oscillation control unit 25, the determination unit 26, and the like means that these are integrated in the control element 16.

  For example, the power factor improvement control unit generates a chopping frequency signal that is a switching pulse of the switching element based on a predetermined signal such as an input voltage on the power source side and a switching current flowing in the switching element of the power factor improvement circuit. It has a function to generate and output.

  The oscillation control unit 25 controls the power conversion circuit 15 to continuously control the discharge lamp FL so that it is lit from the preheating state before starting through the starting state. That is, the oscillation control unit 25 puts the discharge lamp FL in a preheating state by operating the power conversion circuit 15 in the preheating mode (before starting), and starts the discharge lamp FL in the starting mode by operating the power conversion circuit 15 in the starting mode. The lighting control of the discharge lamp FL can be performed by operating the power conversion circuit 15 in the lighting mode.

  The oscillation control unit 25 has a function of generating a frequency signal P having a predetermined frequency based on the lighting state of the discharge lamp FL determined by the determination unit 26. Specifically, the oscillation control unit 25 stops the inverter circuit 13 when the detection voltage VCL is lower than the first threshold voltage VTH1 or when the detection voltage VCL exceeds the second threshold voltage VTH2. In other cases, the frequency signal P is generated according to the lighting state of the discharge lamp FL.

  In addition, the determination unit 26 shown in FIG. 1 includes a detection voltage VCL output from the voltage detection means 21, a first threshold voltage VTH1 such as 0.5V, and a first threshold voltage 4TH that is greater than the first threshold voltage VTH1. Two threshold voltages VTH2 are compared and determined, and the comparison determination result is output to the oscillation control unit 25 side. Further, as shown in FIG. 2 (a), FIG. 2 (b) and FIG. 3, the determination unit 26 calculates the first threshold voltage VTH1 from the detection voltage VCL from any point in the preheating mode of the power conversion circuit 15. The comparison of the magnitude is started, and the magnitude comparison of the second threshold voltage VTH2 with the detected voltage VCL is started after the start mode of the power conversion circuit 15.

  Further, as shown in FIG. 1, the drive element 17 has a frequency of about several tens of kHz to 200 kHz, for example, 50 kHz or more, according to the frequency signal P for dimming supplied from the oscillation control unit 25 of the control element 16. By turning on / off the field effect transistors Q1 and Q2 alternately (switching driving), a predetermined high-frequency alternating current is generated between the drain and source of the field effect transistor Q2.

  The discharge lamp lighting device 10 configured as described above can be applied to a lighting fixture as an electric device as shown in FIG. This lighting fixture includes a fixture main body 41 in which the discharge lamp lighting device 10 is disposed, sockets 42 on which both ends of the fixture main body 41 are mounted with straight tube-type discharge lamps FL, and the like.

  Next, the operation of the above embodiment will be described.

  When the discharge lamp lighting device 10 shown in FIG. 1 is started, power is supplied from the power factor correction circuit to the control element 16, and the control element 16 operates (preheating mode).

  In the control element 16, the switching element of the power factor correction circuit is switching driven by the chopping frequency signal generated by the power factor correction control unit, and the phase of the input voltage rectified by the power source is changed by the power factor correction circuit. The power factor is improved in accordance with the phase, and the drive element 17 is driven by the frequency signal P generated by the oscillation control unit 25, so that the field effect transistors Q1 and Q2 are turned on and off at a predetermined frequency such as 50 kHz. In order to operate, a DC voltage obtained by smoothing the output voltage output from the power factor correction circuit is converted into a high-frequency AC voltage, and this high-frequency AC voltage causes the resonance circuit 14 to resonate and a resonance current flows, and a preheating circuit As a result, the filaments FLa and FLb of the discharge lamp FL are preheated.

  When the inverter circuit 13 is driven, power is supplied to the control element 16 from the inverter circuit 13 side.

  Further, the detection voltage VCL detected by the voltage detection means 21 is input to the determination unit 26 of the control element 16 from the start of the preheating mode. Only when the detection voltage VCL is lower than the first threshold voltage VTH1 (VCL <VTH1), the signal output from the determination unit 26 to the oscillation control unit 25 is used to generate an electric field by the frequency signal P in the oscillation control unit 25. The switching operation of the effect transistors Q1 and Q2 is stopped, and the inverter circuit 13 is stopped.

  Thereafter, when a predetermined time elapses, the preheating mode is ended, and a predetermined starting voltage is applied between the filaments FLa and FLb by the preheating of the filaments FLa and FLb in the preheating mode, so that the discharge lamp FL is started.

  Then, after the start mode is started, the start voltage is supplied to the discharge lamp FL by the power conversion circuit 15, and when the discharge lamp FL is started and lit, the start mode is ended and the mode is changed to the lighting mode.

  Even after the start of the start mode, the detection voltage VCL detected by the voltage detection means 21 is input to the determination unit 26 of the control element 16 via the resistor R11. When the detection voltage VCL falls below the first threshold voltage VTH1 (VCL <VTH1), or when the detection voltage VCL exceeds the second threshold voltage VTH2 (VCL> VTH2), the determination unit 26 controls the oscillation control unit. In response to this signal, the oscillation control unit 25 stops the switching operation of the field effect transistors Q1 and Q2 by the frequency signal P and stops the inverter circuit 13.

  Then, after the discharge lamp FL is turned on, the frequency signal P supplied from the oscillation control unit 25 to the drive element 17 is generated on the basis of the detection voltage VCL detected by the voltage detection means 21, so that the inverter circuit 13 Feedback control is performed such that the drive frequency is varied and the discharge lamp current (discharge lamp voltage, discharge lamp power) becomes a predetermined target value.

  As described above, the determination unit 26 determines whether or not the detection voltage VCL detected by the voltage detection means 21 from an arbitrary point in the preheating mode of the power conversion circuit 15 is lower than the predetermined first threshold voltage VTH1, and the power conversion The determination unit 26 determines whether or not the detected voltage VCL detected by the voltage detecting means 21 from an arbitrary point after the start mode of the circuit 15 exceeds the predetermined second threshold voltage VTH2, and the detected voltage VCL is equal to the predetermined first voltage. When it is determined that the voltage is lower than the threshold voltage VTH1, and when it is determined that the detected voltage VCL exceeds the predetermined second threshold voltage VTH2, the oscillation control unit 25 is connected to the inverter circuit 13 of the power conversion circuit 15, respectively. By stopping the circuit, it is possible to prevent excessive power supply when a low impedance component is connected from the preheating mode to the output side of the power conversion circuit 15, thereby protecting the circuit, and After de start becomes possible even circuit protection against overvoltages.

  In other words, for use as a lighting fixture, between the output terminals of the resonance circuit 14 of the power conversion circuit 15 to which the discharge lamp FL is connected, the discharge lamp FL is rarely tracked as the impedance in the output terminal of the discharge lamp FL decreases. May occur. Therefore, by providing the first threshold voltage VTH1 so as to detect the low discharge lamp voltage VL, it is possible to reliably prevent damage to the circuit due to excessive power supply when tracking or the like occurs.

  Moreover, in the normal operation, the control sequence of the discharge lamp lighting device 10 elapses in the order of the preheating mode, the start mode, and the lighting mode of the power conversion circuit 15. Since the low discharge lamp voltage VL may be generated from the preheating mode, the determination unit 26 compares the detection voltage VCL with the first threshold voltage VTH1 from the preheating mode, thereby reducing the low discharge lamp voltage VL in the preheating mode. Excessive power supply due to can be reliably prevented. Further, since overvoltage may occur from the start mode, the determination unit 26 compares the detected voltage VCL with the second threshold voltage VTH2 after the start mode is started. Can reliably protect the circuit.

  Further, based on the detection voltage VCL detected by the voltage detection means 21 from an arbitrary point in the preheating mode of the power conversion circuit 15, the determination unit 26 determines whether the voltage is lower than the predetermined first threshold voltage VTH1, whereby the circuit The determination unit 26 can easily avoid the determination based on the whole and the detection voltage VCL in an unstable state when the control element 16 rises, and the determination by the determination unit 26 is ensured.

  Further, the determination unit 26 determines whether or not the predetermined second threshold voltage VTH2 is exceeded based on the detection voltage VCL detected by the voltage detection means 21 from an arbitrary point after the start mode of the power conversion circuit 15 is started. Thus, it is possible to set a suitable start mode time corresponding to the breakdown voltage of the components constituting the circuit and the characteristics of the discharge lamp FL. That is, since a high voltage is applied to the circuit during the start mode time, if the start mode time is too long, the breakdown voltage of the component must be increased, and the life of the circuit may be shortened. On the other hand, it is preferable that the discharge lamp FL has a long start mode time in order to ensure start characteristics. In addition, if the start mode time is too short, it is preferable for the part, but the start characteristics of the discharge lamp FL deteriorate. Therefore, detection (determination) is performed by determining whether or not the predetermined second threshold voltage VTH2 is exceeded based on the detection voltage VCL detected by the voltage detection means 21 from an arbitrary point after the start mode is started. The start mode time can be set according to the start timing, and it becomes easy to secure a suitable start time in consideration of the characteristics of the components and the discharge lamp FL.

  Further, by integrating the determination unit 26 together with the oscillation control unit 25 and the like, the circuit as a whole can be reduced in size.

  Further, the voltage detection means 21 can detect the detection voltage VCL by a resistance voltage division with a smaller voltage division ratio of the discharge lamp voltage VL as the electric potential becomes higher, thereby optimizing the voltage division ratio of the discharge lamp voltage VL. 21 can be miniaturized. In addition, when the voltage detection means 21 is downsized in this way, there is an increased possibility that noise from the periphery will be placed on the detection voltage VCL, but in this embodiment, the voltage division ratio on the high potential side that is more susceptible to noise. Therefore, the influence of noise from the surroundings can be reduced even when downsizing.

  In the above embodiment, the detection voltage VCL detected by the voltage detection means 21 is a value that can indirectly detect the discharge lamp voltage VL, that is, has a predetermined relationship with the discharge lamp voltage VL ( Any value may be used as long as it is a value (corresponding to the discharge lamp voltage VL).

  The detailed configurations of the DC power supply 11 and the power conversion circuit 15 are not limited to the above configuration and control.

10 Discharge lamp lighting device
11 DC power supply
15 Power conversion circuit
21 Voltage detection means
25 Oscillation control unit as control means
26 Judgment part as judgment means
FL discharge lamp
Q1, Q2 Field effect transistors as switching elements

Claims (2)

A DC power source that outputs a DC voltage;
Each of the control modes includes a preheating mode for preheating the discharge lamp, a starting mode for starting the discharge lamp, and a lighting mode for controlling the lighting of the discharge lamp. A power conversion circuit that converts a DC voltage into a high-frequency voltage and supplies it to a discharge lamp;
Voltage detection means for detecting a detection voltage corresponding to the discharge lamp voltage;
It is determined whether or not the detection voltage detected by the voltage detection means from an arbitrary point in the preheating mode of the power conversion circuit is lower than a predetermined first threshold voltage, and the voltage detection means from an arbitrary point after starting the start mode of the power conversion circuit Determining means for determining whether or not the detected voltage detected by the step exceeds a predetermined second threshold voltage larger than a predetermined first threshold voltage;
While controlling the drive of the power conversion circuit, the determination means determines that the detected voltage is lower than the predetermined first threshold voltage, and determines that the detected voltage exceeds the predetermined second threshold voltage And control means for stopping the power conversion circuit respectively when
A discharge lamp lighting device comprising: The discharge lamp lighting device according to claim 1, wherein the voltage detection means detects the detection voltage by a resistance voltage division in which a voltage division ratio is reduced as the electric potential increases.

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