JPS63259997A - Discharge lamp lighter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a discharge lamp lighting device for starting and lighting a discharge lamp using high frequency.

2. Prior Art A conventional discharge lamp lighting device is disclosed in, for example, Japanese Patent Application No. 61-30.
As shown in the specification of No. 4202, the circuit was as shown in FIG.

That is, in FIG. 3, a power supply circuit 4 is constructed by rectifying the AC voltage of a commercial power supply 1 with a rectifier bridge 2 and smoothing it with a smoothing capacitor 3, and a parallel resonant circuit 7 of a resonant inductance 5 and a capacitor 6 is connected to the output of the power supply circuit 4. and transistor 11
are connected in series. Furthermore, an inductance 8 for current limiting and a fluorescent lamp 10 are connected to both ends of the parallel resonant circuit 7.
are connected in series, and a starting capacitor is connected to the reverse source side of the fluorescent lamp 10. Inductance 8/2
The next winding 8b has one end connected to the base of the transistor 11 via the capacitor 13, and the other end connected to the inductance 12.
It is connected to the emitter of transistor 11 via. A series circuit of a diode 14 and a resistor 15 is connected in opposite directions between the base and emitter of the transistor 11, and a starting resistor 16 is connected between the base of the transistor 11 and the opposite end of the parallel resonant circuit 7 to the transistor 11. The operation of the conventional circuit configured as zero or more that constitutes the drive circuit 17 will now be described. When the power is turned on, a voltage is generated in the power supply circuit 4, the transistor 11 is turned on by the starting resistor 16, and a current flows through the parallel resonant circuit 7, the inductance 8, and the capacitor 9. inductance 8
A positive voltage is generated in the secondary winding 8b of the inductance 8, and the capacitor 13 and the inductance 12 are connected to the secondary winding 8b of the inductance 8.
A base current is supplied through the transistor 11 to keep the transistor 11 on. At this time, the positive voltage generated in the secondary winding 8b of the inductance 8 causes series resonance to occur in the inductance 12 and capacitor 13 at their natural oscillation frequency, and the resonant current, that is, the base current changes from positive to negative around half the period. The accumulated charge between the base and emitter of the transistor 11 is rapidly released, and the transistor 11
turns off. When the transistor 11 is turned off, the energy stored in the series resonant circuit of the capacitor 9 and the inductance 21 and the inductance 5 is released to the capacitor 6, the fluorescent lamp 10, the capacitor 9 and the inductance 21, and the inductance 5, thereby increasing the preheating current and starting voltage of the fluorescent lamp 10. becomes.

At this time, the oscillating current flowing through the primary winding 8a of the inductance 8 due to the natural oscillation frequency of these circuits generates a negative voltage in the secondary winding 8b of the inductance 8. Therefore, a reverse voltage is applied between the base and emitter of the transistor 11 via the diode 15 and the resistor 14 to keep the transistor 11 off. When the oscillating current passes a negative peak, a positive voltage is generated in the secondary winding 8b of the inductance 8, turning on the transistor 11 and repeating the above operation.

As time passes, the temperature of the preheating electrode of the fluorescent lamp 10 rises, and the fluorescent lamp 10 turns on.

After starting, the operation of the circuit is almost the same, but fluorescent lamp 1
Since the zero impedance is connected in parallel with the impedance of capacitor 9, the current in capacitor 9 decreases and current flows through the lamp. Therefore, the resonance between the inductance 8 and the capacitor 9 becomes small, and a positive and negative base voltage is generated in the secondary winding 8b of the inductance 8 according to the difference between the output voltage of the power supply circuit 4 and the lamp voltage, and the characteristic of the drive circuit 17 is The transistor 11 is controlled on and off according to the vibration frequency to stably light the fluorescent lamp.

Problems to be Solved by the Invention However, with the above configuration, especially when the discharge lamp is not normally lit, such as when starting or at the end of its life,
If the natural oscillation period of the resonance generated in the power circuit portion of the capacitor 6.9 and inductance 5.8 and the natural oscillation period of the drive circuit 17 consisting of the capacitor 13 and inductance 12 do not match appropriately, the power part and the drive circuit 17 There have been problems such as abnormal oscillation occurring in the circuit, generating excessive voltage or current in the circuit, and loss of the transistor 11 increasing to an extreme level, resulting in damage. Therefore, the variations in each of these components and the transistor 11 and the setting conditions for each component become narrower, and
There is a problem in that setting conditions become even more difficult due to changes in the fluorescent lamp or the surrounding environment. Particularly in the case of fluorescent lamps, due to variations in these parts and the transistor 11 at startup, and the condition of the fluorescent lamp, if the lamp is turned on by cold cathode discharge before sufficient preheating is performed, the lifespan may be shortened due to deviations from the set conditions. There is a problem that
In particular, it has become difficult to set up these parts.

Means for Solving the Problems In order to solve the above problems, the present invention includes a power supply whose output voltage has a constant polarity, and a power supply connected to the output terminal of the power supply to turn on/off a current in the forward direction of the power supply. a switch means with a control terminal, a parallel circuit of a first inductance and a first capacitor connected between the other end of the power source and the switch means, and a parallel circuit connected in parallel to the parallel circuit or the switch means. a series circuit of a second inductance and a discharge lamp; a second capacitor connected in parallel to the discharge lamp; at least a third inductance, a third capacitor and a secondary winding of the second inductance; a closed circuit connected in series with a control terminal of the switch means to control on/off of the switch means; and a voltage detector connected in parallel to detect the voltage of the third capacitor or third inductance. and a cutoff circuit that is connected to the output end of the voltage detection circuit and turns off the switch means with a control terminal in response to an output signal.

According to the above-described configuration, the present invention detects a voltage of the third capacitor or the third inductance which is higher than that during normal lighting at the time of starting the discharge lamp or at an abnormality, and detects the voltage of the third capacitor or the third inductance, and activates the switch means with a control terminal. The ON period of the transistor is appropriately set by turning it off by the cutoff circuit, and after the transition to normal lighting, the transistor is turned on and off using the conventional resonance between the third inductance and the third capacitor.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. FIG. 1C is a circuit diagram showing an embodiment of the discharge lamp lighting device of the present invention. Further, FIG. 2 shows circuit waveforms of the lighting device of the present invention. In FIG. 1, there is a power supply circuit 4 whose output voltage has constant polarity, which is composed of a commercial power supply 1, a rectifying bridge 2, and a smoothing capacitor 8, and a resonant circuit, which is a first inductance, connected in series to its output. A parallel resonant circuit 7 consisting of an inductance 5 and a capacitor 6 which is a first capacitor, a transistor 11 which is a type of switch means with a control terminal, and a current limiting circuit which is a second inductance connected to both ends of the parallel resonant circuit 7. A series circuit of an inductance 8 and a fluorescent lamp 10, a starting capacitor 9 which is a second capacitor connected to the reverse side of the fluorescent lamp 10, and an inductance 12 which is a third inductance to the emitter of a transistor 11. The secondary winding 8b of the inductance 8 is connected in the opposite direction between the base and emitter of the transistor 11 and the secondary winding 8b of the inductance 8 is connected at one end to the base of the transistor 11 through the capacitor 13 which is a third capacitor to the other end. diode 14 and resistor 15
The configuration and operation of the series circuit and the starting resistor 16 connected between the base of the transistor 11 and the end of the parallel resonant circuit 7 opposite to the transistor 11 are the same as in the conventional example. What is different from the conventional example is the series circuit of a resistor 18, a diode 19, a constant voltage diode 20, and a resistor 21, which are connected in parallel to the inductance 12 so that the anti-emitter side end of the inductance 12 is in the forward direction when the potential is positive. A cutoff circuit 24 consists of a certain voltage detection circuit 22 and a transistor 23 whose base is connected to a resistor 21 which is the output terminal of the voltage detection circuit 22 and whose collector and emitter are connected in the forward direction between the base and emitter of the transistor 11. .

The operation of the conventional circuit configured as above will be explained.

When the power is turned on, a voltage is generated in the power supply circuit 4 and the transistor 11 is turned on by the starting resistor 16. When the fluorescent lamp 10 starts immediately after the power is turned on, since the fluorescent lamp 10 is not lit, the current flows through the parallel resonant circuit 7, the inductance 8, the filament electrode of the fluorescent lamp 10, and the capacitor 9.
flows through. At this time, a positive voltage is generated in the secondary winding of the inductance 8, tl18b, and the base current of the transistor 11 is supplied via the capacitor 13 and the inductance 12, thereby keeping the transistor 11 on.

At this time, the current flowing through the primary winding 8a of the inductance 8 is a series resonance current between the capacitor 9 and the inductance 8. Further, the current flowing due to the positive voltage generated in the secondary winding 8b of the inductance 8 is a series resonant current at the natural vibration frequency of the inductance 12 and the capacitor 13, and the magnitude of the current flowing in the primary winding 8a of the inductance 8 is flows in proportion to. At this time, the voltage across the inductance 12 gradually changes and rises from negative to positive as shown in FIG. 2C. When the voltage applied to the constant voltage diode 20 of the voltage detection circuit 22 becomes equal to or higher than the Zener voltage due to this voltage increase, a current flows from the inductance 12 via the resistor 18 and the diode 19, and a voltage is generated in the resistor 21, causing the inductance 12 It is detected that the voltage of the resistor 21 has reached a predetermined value (FIG. 2d), and the voltage of the resistor 21 is applied to the base of the transistor 28 of the connection circuit 29, so that the transistor 23 is turned on and the base of the transistor 11 is turned on.
Short between emitters. Therefore, at the same time that the base current of the transistor 11 stops flowing, the accumulated charge between the base and emitter of the transistor 11 is released through the transistor 28, and the transistor 11 is turned off. When the transistor 11 is turned off, the energy stored in the series resonant circuit of the capacitor 9 and the inductance 8 and the inductance 5 is released to the capacitor 6, the fluorescent lamp 10, the capacitor 9, the inductance 8, and the inductance 5, and vibrates at its natural vibration period. Before starting the fluorescent lamp 10, the inductance 8 and the capacitor 9 are in a series resonance state, and a much larger voltage is generated in the capacitor 9 than when the lamp is turned on, and is applied to the lamp. At this time, the fluorescent lamp 10 does not start immediately after the power is turned on due to the voltage generated in the capacitor 9, but it starts after a while when the electrodes of the fluorescent lamp 10 are heated and the temperature rises and the discharge starting voltage decreases. - Set the Zener voltage of the voltage detection circuit 27 appropriately so that the lamp voltage that can be lit can be generated, and when the transistor 11 is turned off, one large turn of the inductance 8 is used! l
118afi: The flowing oscillating current generates a negative voltage in the secondary winding 8b of the inductance 8. Therefore, a reverse voltage is applied between the base and emitter of the transistor 11 via the diode 15 and the resistor 14 to keep the transistor 11 off. When the oscillating current of a part of the power passes a negative peak, a positive voltage is gradually generated in the secondary winding 4g18b of the inductance 8, turning on the transistor 11, and repeating the above operation. The lamp voltage can be set simply by adjusting the Zener voltage of the voltage detection circuit 22 to such a lamp voltage that the fluorescent lamp 10 will not start until the electrodes of the fluorescent lamp 10 are sufficiently heated. Therefore, capacitor 6.9.13 and inductance 5
, 8.12, etc. can be made larger, and the parts can be easily set. In addition, even if the setting conditions become narrower due to variations in each component or the fluorescent lamp 10 or changes in the surrounding environment, the variations in the generated lamp voltage will be smaller because the variations in the Zener voltage of the voltage detection circuit 22 will be the main cause. This can be absorbed simply by adjusting the Zener voltage, making it easy to set the optimal lamp voltage with an inexpensive configuration. Therefore, shortening of the life of the fluorescent lamp 10 due to cold cathode discharge can be easily prevented. Furthermore, regarding the matching between the natural vibration period of the resonance generated in the power circuit section of the capacitor 6.9 and inductance 5.8 during startup and the natural vibration period of the drive circuit 17, abnormal oscillation occurs and excessive voltage is generated in the circuit. The oscillation voltage is fed back by the secondary winding 8b of the inductance 8, and the voltage of the inductance 12 rises more quickly before the current is generated.
This can be done safely because the ON period of transistor 11 can be shortened and the collector current peak value of transistor 11 can be kept almost constant at all times without damaging the circuit components.

Due to the above-described oscillation operation, the temperature of the preheating electrode of the fluorescent lamp 10 increases over time, and the fluorescent lamp 10 gradually turns on.

Before starting the fluorescent lamp 10, the inductance 8 and the capacitor 9 are in a series resonance state, and the inductance 8 is in a series resonance state.
A voltage larger than that during lighting is generated in the next winding, 1!8b, and therefore a larger voltage is also generated in the inductance 12 than during lighting.

On the other hand, after the fluorescent lamp 10 is turned on, the impedance of the fluorescent lamp 10 is connected in parallel to the capacitor 9, so the current in the capacitor 9 decreases and current flows through the lamp. Therefore, resonance between the inductance 8 and the capacitor 9 is almost eliminated, and a voltage corresponding to the difference between the output voltage of the power supply circuit 4 and the lamp voltage is generated in the secondary winding 8b of the inductance 8. At this time, the voltage generated in the secondary winding 8b of the inductance 8 is small, and therefore the voltage generated in the inductance 12 is also small. Here, the Zener voltage of the voltage detection circuit 22 can be set so that it is lower than the voltage across the inductance 12 at the time of starting and higher than the voltage across the inductance 12 at the time of lighting. Therefore, when the light is turned on, no current flows through the voltage detection circuit 22 and the output signal becomes zero, so that the transistor 28 of the cutoff circuit 29 can reliably maintain the off state. Therefore, when the transistor 11 is turned on, a positive voltage is generated in the secondary winding 4!8b of the inductance 8, and a base current is supplied through the capacitor 13 and the inductance 12. The period is controlled by the series resonance of the inductance 12 and the capacitor 13, and the voltage sensing circuit 22
In other words, when the base current of the transistor 11, which is a resonant current, changes from positive to negative around the half cycle, the accumulated charge between the base and emitter of the transistor 11 is rapidly released, and the transistor 11 is turned off. , the on period of the transistor 110 corresponds to the oscillation period of the base circuit. In addition, when the fluorescent lamp 10 is turned on abnormally (when almost no lamp current flows, such as at the end of its life), the state is the same as when the fluorescent lamp 10 is started, and abnormal oscillations in the circuit can be similarly prevented. .

As described above, in this embodiment, the inductance 1
2 is detected by the voltage detection circuit 22 and the transistor 11 is turned off by the cutoff circuit 24. When the inductance 8 and the capacitor 9 resonate in series, the on-period of the transistor 11 is set to an appropriate period that is shorter than when the light is on. Setting can be done with a simple and inexpensive configuration that only requires setting the Zener voltage of the circuit 22. Therefore, the fluorescent lamp 10 does not start up until the electrodes of the fluorescent lamp 10 are sufficiently heated after the fluorescent lamp 10 is powered on, and current is only allowed to flow through the electrodes, which shortens the life of the fluorescent lamp 10 due to cold cathode discharge. can be easily prevented. Furthermore, after sufficient preheating, the fluorescent lamp 10 can be started quickly and reliably. Furthermore, the circuit can be easily and safely protected against resonance between the capacitor 9 and the inductance 8 when the fluorescent lamp 10 is started or abnormally lit. Further, the resonant voltage of the capacitor 9 and the inductance 8 is fed back and the voltage detection circuit 22 detects that the transistor 11t! is in a predetermined state! : Since it can be turned off, the voltage of the fluorescent lamp 10 at this time is almost determined by the voltage detection circuit 22 and does not depend on the values of each inductance or capacitor. Therefore, variations in each inductance and capacitor may be large, and settings can be made easily and at low cost.

In this embodiment, the fluorescent lamp 10 is used as the discharge lamp, but other lamps such as a high-pressure discharge lamp that does not require preheating can also be used to achieve the same effect, such as safe protection. Further, although the voltage of the inductance 12 is detected, substantially the same effect can be obtained by detecting the voltage of the capacitor 13. Note that when detecting the voltage across the inductance 12, as shown in FIG. Even when the collector current decreases and the voltage across the secondary winding 8b decreases, the voltage across the inductance 12 further increases, so that the transistor 23 can be sufficiently maintained in the on state, and the turn-off loss of the transistor 11 can be reduced. In addition, inductance 12 and capacitors 13 and 2
The next winding 8b may be connected in series, and as long as the voltage of the inductance 12 or capacitor 13 can be detected, the connection order may be any other order, and another constant voltage element or a relatively small impedance element with a positive characteristic may be inserted in between. Further, although the voltage detection circuit 22 uses a constant voltage diode, a resistive voltage divider or other configuration may be used as long as it detects the voltage of the inductance 12 and operates the cutoff circuit 24.

As described in detail, the present invention can safely protect against oscillations when starting or abnormally lighting a discharge lamp even if there are large variations in elements, and can quickly and stably start and light a discharge lamp. A discharge lamp lighting device can be realized.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, Fig. 2 is a waveform diagram showing circuit operation waveforms of the same device, and Fig. 3 is a circuit diagram of a conventional discharge lamp lighting device. . DESCRIPTION OF SYMBOLS 1... Commercial power supply, 4... Power supply circuit, 7... Parallel resonant circuit, 8... Inductance, 10... Fluorescent lamp, 11... Transistor, 17... Drive circuit, 2
2...Name of voltage detection circuit agent Patent attorney Toshio Nakao Figure 1 Base end 2 'aiEa diagram

Claims (1)

[Claims] a power supply whose output voltage has a constant polarity; a switch means with a control terminal connected to the output end of the power supply for turning on and off a forward current to the power supply; and between the other end of the power supply and the switch means. a parallel circuit of a first inductance and a first capacitor connected to said parallel circuit or said switch means and a series circuit of a second inductance and a discharge lamp connected in parallel to said discharge lamp; The connected second capacitor, at least a third inductance, the third capacitor, the secondary winding of the second inductance, and the control terminal of the switch means are connected in series to turn on the switch means. a closed circuit for off-control; a voltage detection circuit connected in parallel to detect the voltage of the third capacitor or the third inductance; A discharge lamp lighting device comprising a cutoff circuit for turning off a switch means with a control terminal.