JP2007066628A - Discharge lamp lighting device and luminaire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device having a simple structure and capable of properly carrying out light control and extinction of a cold-cathode discharge lamp according to duty of a PWM light control signal; and to provide a luminaire with the discharge lamp lighting device installed therein. <P>SOLUTION: This discharge lamp lighting device 1 is provided with: a lighting detection circuit 6 for detecting the lighting of the cold-cathode discharge lamp 5; and a lighting control circuit 7 which is so structured as to intermittently operate self-oscillation of an inverter circuit 4 in response to an on/off signal of the PWM light control signal and to stop the self-oscillation when the lighting detection circuit 6 does not detect the lighting of the cold-cathode discharge lamp 5 before a predetermined time longer than the cycle of the PWM light control signal elapses after the self-oscillation is started. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device for dimming and lighting a cold cathode discharge lamp at a high frequency, and a lighting fixture provided with the discharge lamp lighting device.

  Since the cold cathode fluorescent lamp has an outer diameter reduced to 10 mm or less, the lighting fixture can be made thinner. In addition, the cold cathode fluorescent lamp has an average life of, for example, 50000 hours, compared to an average life of 12000 hours for general fluorescent lamps. It can be attached to a lighting fixture disposed in a place where it is necessary.

  The cold cathode fluorescent lamp is dimmed in the same manner as a general fluorescent lamp. For example, a discharge lamp lighting device has been proposed in which a cold cathode fluorescent lamp is dimmed by intermittently operating a drive circuit in accordance with the duty of a PWM dimming signal (see Patent Document 1). In this discharge lamp lighting device, a cold cathode fluorescent lamp is connected to an output terminal of a piezoelectric transformer driven by a drive circuit, and an intermittent oscillation control circuit is connected to the drive circuit. The drive circuit receives the duty control signal from the intermittent oscillation control circuit, drives the piezoelectric transformer during the on-duty period, and stops driving the piezoelectric transformer during the off-duty period. As a result, the cold cathode fluorescent lamp can obtain a stable output until dimming with a low luminous flux.

In addition, a fluorescent lamp driving circuit has been proposed in which the inverter circuit includes a piezoelectric transformer using a piezoelectric ceramic, and includes a switching circuit that intermittently feeds back a feedback signal in the feedback circuit of the inverter circuit so that the cold cathode fluorescent lamp can be dimmed. (See Patent Document 2). In this fluorescent lamp driving circuit, a control signal whose pulse width is modulated is input to the base of the transistor of the switching circuit, whereby the feedback signal is interrupted and the cold cathode fluorescent lamp is dimmed.
JP 2000-58286 A (page 4, FIG. 1) JP-A-9-82485 (page 4-5, FIG. 3)

  In the discharge lamp lighting device of Patent Document 1, the frequency of the intermittent operation of the drive circuit is determined by an intermittent oscillation control circuit provided separately from the dimming signal generation circuit. Since the intermittent oscillation control circuit is formed with a circuit configuration such as a timer circuit for determining an intermittent period for intermittently operating the drive circuit, it has a drawback of increasing the size of the discharge lamp lighting device.

  In addition, the fluorescent lamp driving circuit of Patent Document 2 has a simple configuration that can interrupt the feedback circuit in accordance with a PWM dimming signal input from the outside, but when the frequency of the PWM dimming signal is high, an inverter There is a problem that the operation of the circuit cannot follow the interruption of the feedback circuit, and the cold cathode fluorescent lamp cannot be completely turned off, or the dimming degree of the cold cathode fluorescent lamp may vary.

  The present invention provides a discharge lamp lighting device having a simple configuration and capable of satisfactorily dimming and extinguishing a cold cathode discharge lamp according to the duty of a PWM dimming signal, and a lighting fixture provided with the discharge lamp lighting device. The purpose is to provide.

  The invention of the discharge lamp lighting device according to claim 1 is a DC power supply; an inverter circuit that self-oscillates when a DC voltage of the DC power supply is input, converts the DC voltage into a high-frequency voltage, and outputs the high-frequency voltage; A cold-cathode discharge lamp that is lit by the high-frequency voltage; a lighting detection circuit that detects lighting of the cold-cathode discharge lamp; and intermittent operation of self-oscillation of the inverter circuit in accordance with an on / off signal of the PWM dimming signal; The self-excited oscillation is stopped when the lighting detection circuit does not detect the lighting of the cold cathode discharge lamp before the elapse of a predetermined time longer than the period of the PWM dimming signal after the self-excited oscillation. And a lighting control circuit.

  In the present invention and each of the following inventions, each configuration is as follows unless otherwise specified.

  The DC power supply may be any of a battery, a rectified or rectified and smoothed AC voltage, or a chopper circuit connected thereto.

  When the inverter circuit continuously self-oscillates, the cold cathode discharge lamp is turned on all the time, and when the self-excited oscillation stops, the cold cathode discharge lamp is turned off. Since the cold cathode discharge lamp is lit at a high frequency by an inverter circuit, as the intermittent period of the self-excited oscillation increases, the emitted light flux decreases and the light is adjusted deeply.

  According to the present invention, the self-oscillation of the inverter circuit is intermittently operated according to the on / off signal of the PWM dimming signal. And since the self-excited oscillation is stopped when the lighting detection circuit does not detect the lighting of the cold cathode discharge lamp before the elapse of a predetermined time longer than the period of the PWM dimming signal after the self-excited oscillation, The self-oscillation of the inverter circuit is controlled by the PWM dimming signal at least within the predetermined time. That is, it is possible to prevent the inverter circuit from self-oscillating when the PWM dimming signal is changed so that the cold cathode discharge lamp is lit when the lighting detection circuit does not detect lighting of the cold cathode discharge lamp. Is done. Thereby, the cold cathode discharge lamp is dimmed and extinguished according to the PWM dimming signal.

  The discharge lamp lighting device according to claim 2 is the discharge lamp lighting device according to claim 1, wherein the lighting control circuit includes a time constant circuit of a resistor and a capacitor connected in series between the outputs of the DC power supply. The capacitor is charged by a current from a DC power source when the cold cathode discharge lamp is inconsequential and is discharged when the cold cathode discharge lamp is lit, and the voltage across the capacitor after the start of charging is a PWM dimming signal. The self-excited oscillation can be stopped when the predetermined voltage takes a predetermined time longer than the period of time and becomes a predetermined voltage, and the voltage across the capacitor exceeds the predetermined voltage after the inverter circuit self-oscillates. It is comprised by these.

  According to the present invention, the time required from when the inverter circuit self-oscillates until the voltage across the capacitor reaches the predetermined voltage is the same as the predetermined time longer than the period of the PWM dimming signal. A predetermined time is measured by a time constant circuit of resistors and capacitors.

  The discharge lamp lighting device according to claim 3 is the discharge lamp lighting device according to claim 1 or 2, wherein the lighting control circuit is a turn-off signal in which the PWM dimming signal continuously turns off the cold cathode discharge lamp. In some cases, stopping the self-excited oscillation of the inverter circuit based on the detection of the defect of the cold cathode discharge lamp of the lighting detection circuit is reset.

  When the PWM dimming signal is an extinguished signal, the self-excited oscillation of the inverter circuit is stopped, so that the cold cathode discharge lamp is extinguished, and the lighting detection circuit detects a defect of the cold cathode discharge lamp. At this time, the lighting control circuit resets the stop of the self-excited oscillation of the inverter circuit according to the detection of the cold spot of the cold cathode discharge lamp by the lighting detection circuit. That is, it is possible to prevent the self-excited oscillation of the inverter circuit from being reactivated by the fact that the lighting detection circuit detects the inconvenience of the cold cathode discharge lamp.

  According to the present invention, when the PWM dimming signal is a turn-off signal for continuously turning off the cold cathode discharge lamp, it is reset that the self-oscillation of the inverter circuit is stopped according to the disadvantage of the cold cathode discharge lamp. Therefore, when the extinction signal is changed to the PWM dimming signal for turning on the cold cathode discharge lamp, the inverter circuit self-oscillates, and the self-oscillation of the inverter circuit is intermittently operated according to the PWM dimming signal. .

  The invention of the lighting fixture according to claim 4 comprises: the discharge lamp lighting device according to any one of claims 1 to 3; and a fixture body in which the discharge lamp lighting device is disposed. Features.

  According to this invention, the lighting fixture which comprises the discharge lamp lighting device as described in any one of Claim 1 thru | or 3 is provided.

  According to the first aspect of the present invention, the self-oscillation of the inverter circuit is intermittently operated according to the PWM dimming signal, and when the PWM dimming signal is transmitted, the predetermined period is at least longer than the period of the PWM dimming signal. Since the inverter circuit self-oscillates within the time, the cold cathode discharge lamp can be dimmed and extinguished well in accordance with the PWM dimming signal. Since the self-oscillation of the inverter circuit is stopped when the cold cathode discharge lamp is not lit, a high voltage may be generated across the cold cathode discharge lamp when the cold cathode discharge lamp is defective. It is prevented and the electric shock to a person can be prevented.

  According to the second aspect of the present invention, a predetermined time longer than the period of the PWM dimming signal is measured by the time constant circuit of the resistor and the capacitor, so that the lighting control circuit (discharge lamp lighting device) can be simply configured. Can do.

  According to the invention of claim 3, when the PWM dimming signal is a turn-off signal for continuously turning off the cold cathode discharge lamp, the self-excited oscillation of the inverter circuit is stopped according to the disadvantage of the cold cathode discharge lamp. Therefore, when changing from the extinction signal to the PWM dimming signal for turning on the cold cathode discharge lamp, the inverter circuit can self-oscillate in accordance with the PWM dimming signal, and the cold cathode discharge lamp Can be lit.

  According to invention of Claim 4, the lighting fixture which comprises the discharge lamp lighting device as described in any one of Claim 1 thru | or 3 can be provided.

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

  1 to 3 show a first embodiment of the present invention, FIG. 1 is a circuit diagram of a discharge lamp lighting device, FIG. 2 shows a change in an electric waveform during lighting of a cold cathode discharge lamp, and FIG. (B) is a waveform diagram of the lamp current, (c) is a waveform diagram of the PWM dimming signal, and FIG. 3 is a diagram showing changes in the electrical waveform in the cold cathode discharge lamp, a) is a waveform diagram of the voltage across the capacitor, and (b) is a waveform diagram of the PWM dimming signal.

  In FIG. 1, a discharge lamp lighting device 1 includes a DC power source 2, a starting circuit 3, an inverter circuit 4, a cold cathode fluorescent lamp 5 as a cold cathode discharge lamp, a lighting detection circuit 6, and a lighting control circuit 7. ing.

  The DC power supply 2 includes a rectifier 8 and a smoothing capacitor C1 connected between the output terminals of the rectifier 8 via an inductor L1 for noise prevention, and converts the AC voltage of the commercial AC power supply Vs into a DC voltage. The DC voltage is output across the smoothing capacitor C1. The input side of the rectifier 8 is connected to a commercial AC power supply Vs via a noise preventing capacitor C2 and a fuse F1.

  The starting circuit 3 is formed by a series circuit of a resistor R1, a resistor R2, and a resistor R3 connected between both ends of the smoothing capacitor C1. The starting circuit 3 detects the DC voltage output between both ends of the smoothing capacitor C1.

  The inverter circuit 4 includes an inverter transformer T1, an inductor L2, a resonance capacitor C3, a field effect transistor FET1, and a field effect transistor FET2.

  The intermediate point a of the primary winding T1a of the inverter transformer T1 is connected to the positive side of the smoothing capacitor C1 of the DC power supply 2 via the inductor L2, and one end and the other end of the primary winding T1a are respectively connected to the field effect transistor FET1. The resonance capacitor C3 is connected between one end and the other end (both ends) of the primary winding T1a, and is connected to the negative electrode side of the smoothing capacitor C1 via the field effect transistor FET2. The source side (the negative side of the smoothing capacitor C1) of each of the field effect transistor FET1 and the field effect transistor FET2 is connected to the other end of the secondary winding T1b of the inverter transformer T1.

  The gate of the field effect transistor FET1 is connected to the middle point b of the resistors R2 and R3, and the gate of the field effect transistor FET2 is connected to the middle point b via the tertiary winding T1c of the inverter transformer T1. Yes.

  The inverter circuit 4 receives the DC voltage of the DC power supply 2 output between both ends of the smoothing capacitor C1. When the DC voltage is applied across the start circuit 3 and a DC voltage is generated across the resistor R3, the DC voltage is directly applied to the gate of the field effect transistor FET1, and the field effect transistor FET2 The voltage is applied to the gate via the tertiary winding T1c of the inverter transformer T1. Thereby, the field effect transistor FET1 and the field effect transistor FET2 are turned on alternately.

  When the field effect transistors FET1 and FET2 are alternately turned on, the inductor L2, the resonance capacitor C3, and the primary winding T1a of the inverter transformer T1 resonate, and the DC voltage output between both ends of the smoothing capacitor C1 has a predetermined frequency. Chopping and converting to high frequency voltage. As a result, a high-frequency voltage is output between both ends (one end and the other end) of the secondary winding T1b of the inverter transformer T1. Thus, the inverter circuit 4 self-oscillates by alternately turning on the field effect transistors FET1 and FET2 based on the detection of the DC voltage by the starting circuit 3, and both ends of the secondary winding T1b of the inverter transformer T1. A high frequency voltage is output between them.

  The cold cathode fluorescent lamp 5 is connected between both ends of the secondary winding T1b of the inverter transformer T1 via a ballast capacitor C4 and a lighting detection circuit 6, and lights up when the high-frequency voltage is applied between the electrodes 5a and 5b. . The cold cathode fluorescent lamp 5 has, for example, a rated lamp power of 6 W, a lamp current of 0.007 A, a total luminous flux of 320 lumens, and an average life of 50000 hours. In the drawing, one cold cathode fluorescent lamp 5 is connected, but a plurality of the ballast capacitor C4 and the cold cathode fluorescent lamp 5 connected in series are connected between both ends of the secondary winding T1b of the inverter transformer T1. Multiple lights can be lit by connecting in parallel.

  The lighting detection circuit 6 is connected between the electrode 5b of the cold cathode fluorescent lamp 5 and the other end of the secondary winding T1b of the inverter transformer T1 (the negative side of the smoothing capacitor C1). That is, a diode D1 is connected between the electrode 5b of the cold cathode fluorescent lamp 5 and the other end of the secondary winding T1b with the cathode as the electrode 5b side, and an anode is connected to the cathode of the diode D1 between both ends of the diode D1. A connected diode D2, a parallel circuit of a capacitor C5 and a resistor R4 are connected in series.

  A Zener diode ZD1 and a parallel circuit of the resistor R5 and the capacitor C6 are connected in series between both ends of the resistor R4. A base and an emitter of an NPN transistor Tr1 are connected between both ends of the capacitor C6. Here, the emitter of the NPN transistor Tr1 is connected to the negative electrode side of the smoothing capacitor C1. The collector of the NPN transistor Tr1 is connected to the lighting control circuit 7. The parallel circuit of the capacitor C5 and the resistor R4 and the parallel circuit of the resistor R5 and the capacitor C6 form an averaging circuit (stabilization circuit).

  The lamp current flowing between the electrodes 5a and 5b of the cold cathode fluorescent lamp 5 is alternately switched between the diode D1 or the diode D2 and the capacitor C5 according to the high-frequency voltage output across the secondary winding T1b of the inverter transformer T1. It flows in the parallel circuit of the resistor R4. When the voltage across the capacitor C5 rises and the Zener diode ZD1 becomes conductive, the capacitor C6 is charged and the NPN transistor Tr1 is turned on. That is, when the cold cathode fluorescent lamp 5 is turned on, the NPN transistor Tr1 is turned on, and the collector side of the NPN transistor Tr1 is connected to the negative electrode side of the smoothing capacitor C1. On the other hand, if the cold cathode fluorescent lamp 5 is not lit, the NPN transistor Tr1 is not turned on, and the collector side of the NPN transistor Tr1 is not connected to the negative electrode side of the smoothing capacitor C1. In this way, the lighting detection circuit 6 detects the lighting (non-pointing) of the cold cathode fluorescent lamp 5.

  The lighting control circuit 7 includes a series circuit of a backflow prevention diode D3 and a field effect transistor FET3 connected between the connection point c of the resistors R1 and R2 of the starting circuit 3 and the negative side of the smoothing capacitor C1. The time constant circuit 9 is provided. The time constant circuit 9 is formed by a resistor R6, a Zener diode ZD2 and a smoothing capacitor C7 connected in series between both ends of the smoothing capacitor C1, and a resistor R7 connected in parallel to the smoothing capacitor C7.

  The smoothing capacitor C7 is connected between the gate and the source of the field effect transistor FET3 so that the positive electrode side of the smoothing capacitor C7 is connected to the gate of the field effect transistor FET3 via the backflow preventing diode D4. Yes. The collector of the NPN transistor Tr1 of the lighting detection circuit 6 is connected to the positive side of the smoothing capacitor C7, and is connected to the gate of the field effect transistor FET3 via the diode D4. A gate resistor R8 is connected between the gate and source of the field effect transistor FET3.

  If the lighting detection circuit 6 does not detect the lighting of the cold cathode fluorescent lamp 5, the NPN transistor Tr1 is turned off, so that the smoothing capacitor C7 of the time constant circuit 9 is supplied from the DC power source 2 (smoothing capacitor C1). Charged by current. When the lighting detection circuit 6 detects the lighting of the cold cathode fluorescent lamp 5, the NPN transistor Tr1 is turned on, so that both ends of the smoothing capacitor C7 are short-circuited and the smoothing capacitor C7 is discharged. That is, the smoothing capacitor C7 is charged by the current from the DC power source 2 when the cold cathode fluorescent lamp 5 is not lit, and is discharged when the cold cathode fluorescent lamp 5 is turned on.

  Then, the smoothing capacitor C7 is set so that the voltage between both ends rises to a predetermined voltage (for example, 4V) after a predetermined time determined by the time constant of the resistor R6 and the smoothing capacitor C7 after the start of charging. ing. Here, the time constant is set so that the predetermined time is longer than a period of a PWM dimming signal described later. The voltage across the smoothing capacitor C7 is applied between the gate and the source of the field effect transistor FET3 via the diode D4 when the cold cathode fluorescent lamp 5 is not lit. When the voltage across the smoothing capacitor C7 rises above a predetermined voltage, the field effect transistor FET3 is turned on.

  A dimming signal input circuit 10 is connected between the gate and source of the field effect transistor FET3. The dimming signal input circuit 10 includes a rectifier 12 to which a PWM dimming signal is input from an external dimming device 11 at an input terminal, and a resistor R9 connected between the output terminals of the rectifier 12. The output terminal of the rectifier 12 is connected between the gate and source of the field effect transistor FET3 so that the output terminal on the positive electrode side is connected to the gate of the field effect transistor FET3 via the diode D5 for preventing backflow. ing.

  The PWM dimming signal output from the dimming device 11 has a frequency of, for example, 100 Hz, and is input between the gate and source of the field effect transistor FET3 via the dimming signal input circuit 10. The field effect transistor FET3 is turned on when the PWM dimming signal is on, and is turned off when the PWM dimming signal is off.

  When the field effect transistor FET3 is off, a voltage across the smoothing capacitor C1 of the DC power supply 2 (DC voltage of the DC power supply 2) is applied across the start circuit 3, and a DC voltage is applied across the resistor R3. Occurs. That is, the lighting control circuit 7 enables the detection of the DC voltage output from the DC power supply 2 by the starting circuit 3. Then, a DC voltage generated across the resistor R3 is applied between the gates and sources of the field effect transistors FET1 and FET2, and the field effect transistors FET1 and FET2 are alternately turned on and off, thereby causing the inverter circuit 4 to self-activate. Excited oscillation. Then, a high frequency voltage is output between both ends of the secondary winding T1b of the inverter transformer T1, and the cold cathode fluorescent lamp 5 is lit by this high frequency voltage.

  Further, when the field effect transistor FET3 is turned on, the resistor R2 and the resistor R3 of the starting circuit 3 are short-circuited, and no DC voltage is generated between both ends of the resistor R3. That is, the lighting control circuit 7 invalidates the detection of the DC voltage output from the DC power source 2 by the starting circuit 3. Then, when the field effect transistors FET1 and FET2 do not perform the on / off operation, the inverter circuit 4 does not self-oscillate. And since a high frequency voltage is no longer output between the both ends of the secondary winding T1b of inverter transformer T1, the cold cathode fluorescent lamp 5 is light-extinguished.

  Thus, the lighting control circuit 7 enables and disables the detection of the DC voltage output from the DC power source 2 by the start circuit 3 in accordance with the ON / OFF signal of the PWM dimming signal, and intermittently operates the self-excited oscillation of the inverter circuit 4. Let Then, as the intermittent period of the self-excited oscillation increases, the cold cathode fluorescent lamp 5 is deeply dimmed. Further, when the PWM dimming signal is only an off signal, the cold cathode fluorescent lamp 5 is lit in all light.

  Even if the inverter circuit 4 self-oscillates, if the cold cathode fluorescent lamp 5 is not lit, the NPN transistor Tr1 of the lighting detection circuit 6 is turned off. Therefore, the smoothing capacitor C7 of the time constant circuit 9 has a DC power supply. 2 is charged by the current from 2. When the voltage across the smoothing capacitor C7 becomes equal to or higher than a predetermined voltage, the field effect transistor FET3 is turned on and the self-excited oscillation of the inverter circuit 4 is stopped.

  In this way, the lighting control circuit 7 has the direct current output from the direct current power supply 2 by the starting circuit 3 when the voltage across the smoothing capacitor C7 becomes equal to or higher than the predetermined voltage after the inverter circuit 4 self-oscillates. The detection of the voltage is invalidated and the self-excited oscillation of the inverter circuit 4 is stopped. In other words, the self-excited oscillation of the inverter circuit 4 is intermittently operated according to the on / off signal of the PWM dimming signal until a predetermined time elapses after the inverter circuit 4 self-oscillates. When the lighting detection circuit 6 does not detect the lighting of the cold cathode discharge lamp 5, the detection of the DC voltage by the starting circuit 3 is invalidated and the self-oscillation of the inverter circuit 4 is stopped.

  A reset circuit 13 is formed in the dimming signal input circuit 10. The reset circuit 13 includes a series circuit of a resistor R10 and a capacitor C8 connected between output terminals of the rectifier 12, a discharge path diode D6 connected in parallel to the resistor R10, a positive side of the capacitor C8, and a lighting detection circuit 6. The back-flow preventing diode D7 is connected between the bases of the NPN transistor Tr1. The series circuit of the resistor R10 and the capacitor C8 is formed as a time constant circuit. The reset circuit 13 applies the voltage across the capacitor C8 (charging voltage) between the base and emitter of the NPN transistor Tr1 to turn on the NPN transistor Tr1.

  The capacitor C8 is charged when the PWM dimming signal is on, and is discharged through the path of the diode D6 and the resistor R9 when the PWM dimming signal is off. That is, when the PWM dimming signal is an on / off signal for dimming the cold cathode fluorescent lamp 5, even if the voltage across the capacitor C8 is applied between the base and emitter of the NPN transistor Tr1, the NPN transistor Tr1 Does not turn on.

  When the PWM dimming signal consists only of an ON signal and is an extinguishing signal for continuously turning off the cold cathode fluorescent lamp 5, the capacitor C8 is fully charged, and the NPN transistor Tr1 is turned on by the voltage between both ends thereof. When the NPN transistor Tr1 is turned on, the smoothing capacitor C7 of the time constant circuit 9 is discharged. Thereby, in the lighting control circuit 7, when the voltage across the smoothing capacitor C7 becomes equal to or higher than a predetermined voltage after the inverter circuit 4 self-oscillates, or after the inverter circuit 4 self-oscillates. When the lighting detection circuit 6 does not detect the lighting of the cold cathode discharge lamp 5 before the time elapses, the detection of the DC voltage output from the DC power source 2 by the starting circuit 3 is invalidated, and the inverter circuit 4 itself is detected. Stopping the excitation oscillation is reset.

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

  When an on / off signal of a PWM dimming signal having a frequency of 100 Hz shown in FIG. 2C is input from the external dimming device 11 to the dimming signal input circuit 10 and the DC power source 2 is turned on, the output from the DC power source 2 is output. The activated DC voltage is detected by the starting circuit 3. The inverter circuit 4 self-oscillates by alternately turning on and off the field effect transistors FET1 and FET2 based on the detection of the DC voltage by the starting circuit 3, and a high frequency is generated between both ends of the secondary winding T1b of the inverter transformer T1. Output voltage. Thereby, the cold cathode fluorescent lamp 5 is turned on.

  Then, the field effect transistor FET3 of the lighting control circuit 7 is turned on / off according to the on / off signal of the PWM dimming signal, whereby the self-excited oscillation of the inverter circuit 4 is intermittently operated. That is, when the PWM dimming signal is an off signal, the field effect transistor FET3 is turned off, the detection of the DC voltage by the starting circuit 3 is enabled, and the inverter circuit 4 is self-oscillated. When the PWM dimming signal is the on signal, the field effect transistor FET3 is turned on, the detection of the DC voltage by the starting circuit 3 is invalidated, and the self-excited oscillation of the inverter circuit 4 is stopped.

  Then, as shown in FIG. 2B, a lamp current (high-frequency current) flows between the electrodes 5a and 5b of the cold cathode fluorescent lamp 5 during the self-excited oscillation, and the self-excited oscillation stops. The lamp current stops flowing when Thus, the cold cathode fluorescent lamp 5 is dimmed according to the on / off signal of the PWM dimming signal. As the duty ratio (on period) of the PWM dimming signal increases, the intermittent period of the lamp current flowing between the electrodes 5a and 5b becomes longer and the light is dimmed deeply.

  Immediately after the DC power supply 2 is turned on, or when the cold cathode fluorescent lamp 5 is turned off, or immediately after the cold cathode fluorescent lamp 5 is turned on, the NPN transistor Tr1 of the lighting detection circuit 6 is turned off. The smoothing capacitor C7 of the time constant circuit 9 is charged by the current from the DC power supply 2, and the voltage between both ends thereof increases. When the lighting detection circuit 6 detects lighting of the cold cathode fluorescent lamp 5 and the NPN transistor Tr1 is turned on before the voltage across the smoothing capacitor C7 reaches the predetermined voltage (4 V), FIG. As shown, the smoothing capacitor C7 is discharged. In FIG. 2A, the charging / discharging period of the smoothing capacitor C7 is not synchronized with the on / off signal of the PWM dimming signal because the parallel circuit of the capacitor C5 and the resistor R4 and the parallel of the resistor R5 and the capacitor C6. This is because the voltage between both terminals is stabilized in the circuit.

  The time constant of the time constant circuit 9 is set so that the smoothing capacitor C7 is charged to a predetermined voltage (4V) after the start of charging so that the predetermined time is longer than the period (10 ms) of the PWM dimming signal. It is set to be 25 ms. Until the predetermined time elapses, the field effect transistor FET3 is turned on / off according to the on / off signal of the PWM dimming signal. That is, at least within the predetermined time, the lighting detection circuit 6 does not detect the lighting of the cold cathode fluorescent lamp (detects an inconvenience), so that the field effect transistor FET3 is turned on and the inverter circuit 4 is automatically turned on. It is possible to prevent the excitation oscillation from occurring, and the cold cathode fluorescent lamp 5 can be lit or re-lit by the PWM dimming signal.

  Then, after the inverter circuit 4 self-oscillates in response to the on / off signal of the PWM dimming signal, the lighting detection circuit 6 does not detect the lighting of the cold cathode fluorescent lamp 5 and the NPN transistor Tr1 is off. As shown in FIG. 3A, the voltage across the smoothing capacitor C7 increases. The voltage across the smoothing capacitor C7 becomes a predetermined voltage (4V) after a lapse of a predetermined time (25 ms) after the inverter circuit 4 self-oscillates. This predetermined voltage is applied between the gate and source of the field effect transistor FET3, and the field effect transistor FET3 is turned on. As a result, no DC voltage is generated across the resistor R3 of the starting circuit 3, and the self-excited oscillation of the inverter circuit 4 is stopped.

  In this way, after the inverter circuit 4 is self-excited, the cold cathode fluorescent light is emitted until the voltage across the smoothing capacitor C7 rises to the predetermined voltage (4 V) (until the predetermined time (25 ms) elapses). When the lamp 5 is not lit, the lighting control circuit 7 stops the self-excited oscillation of the inverter circuit 4. Therefore, when the cold cathode fluorescent lamp 5 is inconspicuous, it is possible to prevent a high voltage from being continuously generated between the electrodes 5a and 5b of the cold cathode fluorescent lamp 5, and to prevent electric shock to people in the cold cathode fluorescent lamp 5. be able to.

  A predetermined time (25 ms) until the voltage across the smoothing capacitor C7 rises to the predetermined voltage (4V) is set by the time constant circuit 9, so that a timer circuit or CPU (central processing) is set in the lighting control circuit 7. The lighting control circuit 7 can be formed easily and inexpensively.

  When the extinction signal for turning off the cold cathode fluorescent lamp 5 is input from the external dimming device 11 to the dimming signal input circuit 10 and the PWM dimming signal consists of only the ON signal, The field effect transistor FET3 of the lighting control circuit 7 is turned on. Then, the self-excited oscillation of the inverter circuit 4 is continuously stopped, and the cold cathode fluorescent lamp 5 is continuously turned off.

  When the cold cathode fluorescent lamp 5 is turned off, the lighting detection circuit 6 does not detect the lighting of the cold cathode fluorescent lamp 5 and turns off the NPN transistor Tr1. At this time, the voltage across the capacitor C8 of the reset circuit 13 formed in the dimming signal input circuit 10 is applied between the base and emitter of the NPN transistor Tr1, and the NPN transistor Tr1 is turned on.

  When the NPN transistor Tr1 is turned on, the smoothing capacitor C7 of the time constant circuit 9 is discharged, and the field effect transistor FET3 of the lighting control circuit 7 is turned on only by the extinction signal of the PWM dimming signal.

  When the PWM dimming signal is changed from the extinction signal to the on / off signal for turning on the cold cathode fluorescent lamp 5, the field effect transistor FET3 is turned on / off in response to the on / off signal, and the self-excited oscillation of the inverter circuit 4 is intermittently operated. The The cold cathode fluorescent lamp 5 is dimmed according to the intermittent operation of the self-excited oscillation.

  The capacitor C8 of the reset circuit 13 is discharged when the PWM dimming signal is an off signal. As a result, the NPN transistor Tr1 is turned off. The lighting detection circuit 6 operates so as to detect lighting of the cold cathode fluorescent lamp 5.

  As described above, the reset circuit 13 turns on the NPN transistor Tr1 of the lighting detection circuit 6 to discharge the smoothing capacitor C7 of the time constant circuit 9 when the cold-cathode fluorescent lamp 5 is in a fault. Reset to stop self-excited oscillation. Accordingly, when the PWM dimming signal is changed from the turn-off signal for continuously turning off the cold cathode fluorescent lamp 5 to the on / off signal for dimming the cold cathode fluorescent lamp 5, the PWM dimming signal is changed according to the on / off signal of the PWM dimming signal. Thus, the self-excited oscillation of the inverter circuit 4 can be intermittently operated, and the cold cathode fluorescent lamp 5 can be dimmed.

  As described above, the discharge lamp lighting device 1 can appropriately dim and extinguish the cold cathode fluorescent lamp 5 in accordance with the PWM dimming signal input from the external dimming device 11.

  Next, a second embodiment of the present invention will be described.

  FIG. 4 is a circuit diagram of a discharge lamp lighting device showing a second embodiment of the present invention. Note that the same parts as those in FIG.

  The discharge lamp lighting device 14 shown in FIG. 4 is configured by removing the reset circuit 13 of the dimming signal input circuit 10 from the discharge lamp lighting device 1 shown in FIG. The dimming signal input circuit 10 receives an on / off signal of a PWM dimming signal for dimming and lighting the cold cathode fluorescent lamp 5 from the external dimming device 11 and turns off the cold cathode fluorescent lamp 5 continuously. Is not entered.

  The discharge lamp lighting device 14 dimly lights the cold cathode fluorescent lamp 5 satisfactorily according to the PWM dimming signal input from the external dimming device 11.

  Next, a third embodiment of the present invention will be described.

  FIG. 5 is a schematic cross-sectional view of a luminaire showing a third embodiment of the present invention. Note that the same parts as those in FIG.

  A lighting fixture 15 shown in FIG. 5 is a direct-mounted lighting fixture installed on a construction such as a ceiling, and a box-shaped fixture body 16 is attached to the construction. The instrument main body 16 has a flange portion 16a extending inwardly at a lower end portion, and a translucent cover 17 is detachably attached to an opening surrounded by the flange portion 16a.

  Inside the instrument body 16, a reflector 18 having first and second curved portions 18a, 18b that are curved is disposed so that the respective end portions are placed on the flange portion 16a. In addition, a discharge lamp lighting device 19 is disposed in the central portion of the space between the inner surface of the fixture body 16 and the reflector 18. The discharge lamp lighting device 19 is obtained by removing the cold cathode fluorescent lamp 5 from the discharge lamp lighting device 1 shown in FIG. In the cold cathode fluorescent lamps 5, 5, base caps 20, 20 are fixed to the reflection plate 18 and face the inner surface of the reflection plate 18.

  Since the lighting fixture 15 is provided with the discharge lamp lighting device 1 shown in FIG. 1, the cold cathode fluorescent lamps 5 and 5 are dimmed or turned on in accordance with the PWM dimming signal from the external dimming device 11. Can be turned off. And since the average lifetime of the cold cathode fluorescent lamps 5 and 5 is 50000 hours, the maintenance work of lamp replacement can be saved.

The circuit diagram of the discharge lamp lighting device which shows the 1st Embodiment of this invention. Similarly, changes in the electrical waveform when the cold cathode discharge lamp is turned on are shown, (a) is a waveform diagram of the voltage across the capacitor, (b) is a waveform diagram of the lamp current, and (c) is a waveform diagram of the PWM dimming signal. . Similarly, the change of the electric waveform in the point of the cold cathode discharge lamp is shown, (a) is a waveform diagram of the voltage across the capacitor, (b) is a waveform diagram of the PWM dimming signal. The circuit diagram of the discharge lamp lighting device which shows the 2nd Embodiment of this invention. The schematic sectional drawing of the lighting fixture which shows the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,14 ... Discharge lamp lighting device 2 ... DC power supply 4 ... Inverter circuit 5 ... Cold cathode fluorescent lamp 6 as cold cathode discharge lamp ... Lighting detection circuit 7 ... Lighting control circuit 9 ... Time constant circuit 15 ... Lighting fixture 16 ... Appliance Body

Claims (4)

DC power supply;
An inverter circuit that self-oscillates when a DC voltage of a DC power supply is input, converts the DC voltage into a high-frequency voltage, and outputs it;
A cold cathode discharge lamp lit by the high frequency voltage;
A lighting detection circuit for detecting the lighting of the cold cathode discharge lamp;
The self-excited oscillation of the inverter circuit is intermittently operated in accordance with the on / off signal of the PWM dimming signal, and the lighting detection circuit is operated as a cold cathode before the elapse of a predetermined time longer than the period of the PWM dimming signal after the self-excited oscillation. A lighting control circuit configured to stop the self-excited oscillation when the lighting of the discharge lamp is not detected;
A discharge lamp lighting device comprising:   The lighting control circuit has a time constant circuit of a resistor and a capacitor connected in series between the outputs of the DC power source, and the capacitor is charged by the current from the DC power source when the cold cathode discharge lamp is in a fault, and is cooled. The capacitor is discharged when the cathode discharge lamp is turned on, and the voltage between both ends of the capacitor after starting charging becomes a predetermined voltage that takes a predetermined time longer than the period of the PWM dimming signal. The discharge lamp lighting device according to claim 1, wherein the self-excited oscillation can be stopped when a voltage between both ends of the power supply becomes equal to or higher than the predetermined voltage.   The lighting control circuit stops the self-excited oscillation of the inverter circuit based on the detection of the cold cathode discharge lamp inconsistency in the lighting detection circuit when the PWM dimming signal is a turn-off signal for continuously turning off the cold cathode discharge lamp. 3. The discharge lamp lighting device according to claim 1, wherein the resetting is reset. A discharge lamp lighting device according to any one of claims 1 to 3;
An appliance main body provided with the discharge lamp lighting device;
The lighting fixture characterized by comprising.

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