JPH06111977A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent erroneous detection by detecting the lamp service life terminal stage from a logical product of a H signal outputted from a preheating timer or a light dimmer signal a certain time later and a H detecting signal of the voltage across a lamp. CONSTITUTION:When a switching element 6 or 7 of an inverter circuit 5 is started, the element is switched automatically at a prescribed oscillation frequency by alternate input from a base coil 4b. Input electric power is controlled by a control element 2, and light dimming is carried out on a lamp 12 at the light dimming ratio according to a light dimming signal S1. High voltage of the lamp gives a detecting signal S2 of an H signal to one input terminal of AND gates 18. When this is a high voltage pulse when the lamp is started and light dimming is carried out, the light dimming signal is inputted to the gates 18 through a preheating timer and a delay circuit 17, but output S4 is not generated from the gates 18. When it is the high voltage except when the lamp is started or the light dimming is carried out, both two input of the gates 18 becomes H, and H output can be obtained, and a lamp service life terminal stage signal S4 is issued, and a latch circuit 19 opens a switch SW1, and cuts off DC electric power supply 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a fluorescent lamp, and more particularly to a lighting device capable of detecting the end of life of the lamp without malfunction.

[0002]

2. Description of the Related Art FIG. 2 shows a block diagram of a conventionally known discharge lamp lighting device. In this figure, a DC power source 1 is connected to an inverter circuit 5 through a series circuit of a switch SW1, a dimming control transistor 2 and a current limiting inductor 3 which are cut off when the end of life is detected. The inverter circuit 5 includes an oscillating transformer 4 and switching transistors 6 and 7 connected to the transformer primary side. The switching transistors 6 and 7 are self-excited to switch the secondary side of the oscillating transformer 4. High frequency power is output to. As a result, the fluorescent lamp 12 connected to the secondary side of the oscillation transformer 4 via the capacitor 11 is lit at high frequency. A dimming signal S1 of PWM (pulse width modulation) is output from the dimming signal generation circuit 15 to the dimming control transistor 2, and the dimming signal S1 turns on and off the control transistor 2 to cause the lamp 12 to operate. Is dimmed. Further, the preheating timer circuit 16 outputs a signal for determining the preheating time at the time of starting the lamp to the dimming signal generating circuit 15. As a result, the dimming state is maintained for a certain time when the lamp is started, and the filament of the lamp 12 can be preheated. A diode bridge 13 that rectifies the voltage across the lamp is connected to both ends of the fluorescent lamp 12. The rectified output is divided by the voltage dividing resistors R1 and R2 and then input to the integrating circuit 20. The integrating circuit 20 is connected to the latch circuit 19 via the constant voltage diode 21, and the switch SW1 is opened / closed by the output of the latch circuit 19. As a result, when the voltage across the lamp rises at the end of the life and the voltage across the capacitor C1 exceeds the Zener voltage of the constant voltage diode 14, the switch SW1 is turned off by the output signal of the latch circuit 19 and is supplied to the inverter circuit 5. The DC power supply 1 is cut off.

[0003]

In the above-mentioned conventional lighting device, the voltage dividing resistor R is used to cancel the pulsed high voltage generated at both ends of the lamp at the time of starting the lamp or dimming.
An integrating circuit 20 whose time constant is determined by the resistor R3 and the capacitor C1 is provided between the R1, R2 and the constant voltage diode 14, but the lamp voltage is not affected by the ambient temperature, heat generated by the lamp itself, variations in manufacturing, and aging. In addition to the fluctuation due to the change, the end of life detection is performed regardless of the preheat timer circuit 16 and the dimming signal S1, so it is difficult to determine the constant of the integrating circuit 20, and the lamp is started or dimmed at the time of dimming. There has been a problem that the high voltage generated at both ends is easily erroneously detected as the end of life.

The present invention has been proposed in order to solve the problems of the prior art, and an object thereof is to provide a discharge lamp lighting device capable of detecting the end of life of the lamp without malfunction.

[0005]

In order to achieve this object, a discharge lamp lighting device according to the present invention comprises a DC power supply, an inverter circuit for converting the DC power supply into a high frequency power supply by using an oscillation transformer and a switching element, A discharge lamp that is connected to the secondary winding of the oscillation transformer of this inverter circuit and that is lit by a high frequency power supply; and a switch that is inserted in the power supply line between the DC power supply and the inverter circuit and that is cut off by the end of life detection signal. , A control circuit that outputs a dimming signal of pulse width modulation to the dimming control transistor inserted in this power supply line, and a timer signal that determines the preheating time when preheating the lamp filament as a dimming state at the time of lamp starting. A preheat timer circuit that outputs to the control circuit, a lamp voltage detection circuit that detects the voltage across the discharge lamp,
A delay circuit that delays the timer signal and the dimming signal for a certain period of time, and a logical product gate that performs a logical product of the lamp end voltage detection signal and the output signal of the delay circuit are provided. The detection signal is input to the switch.

[0006]

According to the above-mentioned structure, the high-level signal (H signal) and the detection signal (H signal) of the voltage across the lamp are output after the preheat timer signal or the dimming signal is output and after a certain time delay. And the logical product signal is used as the lamp end-of-life detection signal, so the pulsed high voltage at both ends of the lamp that occurs during lamp start-up or dimming will not be erroneously detected as the end-of-life. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the discharge lamp lighting device according to the present invention will be described in detail below with reference to the drawings. An example of this lighting device is shown in the block diagram of FIG. In this figure, the positive terminal of the DC power source 1 is an intermediate tap of the primary winding 4a of the oscillation transformer T1 via a series circuit of a switch SW1, which is cut off at the end of the lamp life, a dimming control transistor 2, and a current limiting inductor 3. It is connected to the. The oscillation transformer 4 constitutes a part of the inverter circuit 5. Switching transistors 6 and 7 are connected to one end and the other end of the primary winding 4a of the oscillation transformer 4, and the emitters of these transistors 6 and 7 are connected to the negative terminal of the DC power supply 1. Further, one ends and the other ends of the base windings 4b are connected to the bases of the switching transistors 6 and 7, respectively, and the positive side of the DC power source 1 via the current limiting inductor 3 is connected to the starting resistor 9,
It is connected via 10. The capacitors 8 connected to both ends of the primary winding 4a are capacitors for oscillation. A capacitor 1 is attached to the secondary winding 4c of the oscillation transformer 4.
For example, a hot cathode fluorescent lamp 12 is connected via 1. Further, a timer signal for preheating for a certain time at the time of starting the lamp is input from the preheating timer circuit 16 to a dimming signal generating circuit 15 forming a control circuit, and the dimming signal generating circuit 15 dims the lamp at the time of starting. The lamp filament can be preheated by outputting the control signal for setting the state to the dimming control transistor 2.

A diode bridge 13 for full-wave rectifying the voltage across the lamp is connected to both ends of the fluorescent lamp 12, and voltage dividing resistors R1 and R2 are connected between the rectified output terminals of the diode bridge 13. . The voltage dividing points of the voltage dividing resistors R1 and R2 are connected to one input terminal of the AND gate 18 via the constant voltage diode 14. As a result, when the voltage across the lamp rises and the divided voltage exceeds the Zener voltage of the constant voltage diode 14, a high level (H level) is applied to one input terminal of the AND gate 18.
The lamp voltage detection signal S2 is input. here,
The diode bridge 13, the voltage dividing resistors R1 and R2, and the constant voltage diode 14 constitute a lamp voltage detection circuit. Further, the dimming signal output from the dimming signal generation circuit 15 and the timer signal output from the preheat timer circuit 16 are sent to the delay circuit 17 and, after being delayed for a predetermined time, the other input terminal of the AND gate 18 Entered in. The dimming signal and the timer signal are both positive logic signals.
The delay time of the delay circuit 17 is longer than the pulse width of the pulsed high voltage generated at both ends of the lamp at the time of starting the lamp or dimming the lamp, and is set to a time that can sufficiently avoid this pulse.

Next, the operation of the discharge lamp lighting device configured as described above will be described. In this lighting device, when one of the switching transistors 6 or 7 of the inverter circuit 5 is activated, thereafter, the base current is alternately input to the transistors 6 and 7 from the base winding 4b, so that these transistors 6 and 7 can be supplied. Are self-excited at a predetermined oscillation frequency. As a result, the DC power supply 1 is converted into a high frequency power supply by the inverter circuit 5, and the fluorescent lamp 12 connected to the secondary side of the oscillation transformer 4 is lit at a high frequency. The input power to the inverter circuit 5 is turned on / off by the PWM dimming signal S1.
The fluorescent lamp 12 is dimmed at a dimming ratio (on-duty ratio) based on the dimming signal S1.

Next, the operation of detecting the end of the lamp life will be described. Now, for some reason, if a high voltage is detected across the lamp, H will be applied to one input terminal of the AND gate 18.
The lamp voltage detection signal S2 is input. If this high voltage is a pulsed high voltage generated at the time of starting the lamp or dimming, the other input terminal of the AND gate 18 is the delay signal S3 obtained by passing the preheat timer signal and the dimming signal through the delay circuit 17. At this time, the end-of-life detection signal S4 of the H signal does not appear at the output terminal of the AND gate 18, and the latch circuit 19 does not switch the switch SW1. As described above, by providing the delay circuit 17, it is possible to prevent erroneous detection of the pulsed high voltage generated at the time of starting or dimming as the end of life. On the other hand, when a high voltage is detected at both ends of the lamp except when the lamp is started or when dimming, the H signal is input to both input terminals of the AND gate 18, so that the H signal is output to the output terminal of the AND gate 18. Is output. Accordingly, the lamp life end detection signal S4 of the H signal is input to the latch circuit 19, and the latch circuit 1
The switch SW1 is opened by the output signal of 9 and the input of the DC power supply 1 to the inverter circuit 5 is cut off.

[0011]

As described above, according to the present invention, the logical product signal of the signal obtained by delaying the preheat timer signal or the dimming signal and the detection signals at both ends of the lamp is used as the lamp end-of-life detection signal. The pulsed high voltage generated at both ends of the lamp at the time of starting or dimming is not erroneously detected as the end of life, and the end of life of the lamp can be detected normally. Moreover, by adopting such a detection method, an integrating circuit that directly processes an extremely unstable lamp voltage waveform that is affected by environmental temperature etc. Since it is not necessary to provide it between them, the reliability of the detection operation can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a discharge lamp lighting device according to the present invention.

FIG. 2 is a block diagram showing a conventional discharge lamp lighting device.

[Explanation of symbols]

 1 DC power supply 2 Dimming control transistor 3 Current limiting inductor 4 Oscillation transformer 4a Primary winding 4b Base winding 4c Secondary winding 5 Inverter circuit 6,7 Switching transistor 8 Oscillation capacitor 9,10 Startup resistance 12 Fluorescent lamp 13 Diode Bridge 14 Constant Voltage Diode 15 Dimming Signal Generation Circuit 16 Preheat Timer Circuit 17 Delay Circuit 18 AND Gate 19 Latch Circuit SW1 Switch for Power Off

Claims (1)

[Claims] 1. A DC power supply, an inverter circuit for converting the DC power supply into a high frequency power supply using an oscillation transformer and a switching element, and a high frequency wave from the inverter circuit connected to a secondary winding of the oscillation transformer of the inverter circuit. A discharge lamp that is turned on by a power supply, a switch that is inserted into the power supply line between the DC power supply and the inverter circuit, and is cut off by the end-of-life detection signal, and a power supply line between the DC power supply and the inverter circuit. A control circuit that outputs a pulse-width-modulated dimming signal to the dimming control transistor that is inserted in the control circuit, and a timer signal that determines the preheating time for preheating the lamp filament in the dimming state when the lamp is started. A preheat timer circuit that outputs, a lamp voltage detection circuit that detects the voltage across the discharge lamp, the timer signal and The AND gate includes a delay circuit that delays the dimming signal for a certain period of time, and an AND gate that logically ANDs the lamp voltage detection signal output from the lamp voltage detection circuit and the output signal of the delay circuit. The discharge lamp lighting device is characterized in that the output signal of the above is input to the switch as the end of life detection signal.