JPH01167996A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent an abnormal oscillation or an error operation of a circuit by providing a short circuit transistor and a Zener diode parallel to a driving inductance 12. CONSTITUTION:A Zener diode 21 is connected to let a base current flow between the collector bases of a transistor 18 through a Zener voltage. At the base current discontinuous time when a transistor 6 is switched on, the surge voltage generated at an inductance 12 is also increased, and it is applied between base emitters of the transistor 6 in the regular direction being liable to generate an error operation, but the surge voltage is suppressed by a transistor 18 and the diode 21 parallel to the inductance 12 with its Zener voltage. Furthermore, even though the potential at the capacitor 13 side of the inductance 12 is raised when the transistor 6 is turned on, the turning-on is prevented and the error operation of the circuit is avoided since the diode 21 is connected in the regular direction between the collector emitters of the transistor 18.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a discharge lamp lighting device for starting and lighting a discharge lamp at high frequency.

2. Description of the Related Art A conventional discharge lamp lighting device is disclosed in, for example, Japanese Patent Application Laid-open No. 62-20
Publication No. 2494 and National Technlc
al Report Vol., 33 No., 3 p.
296, the circuit was as shown in Figure 2.

That is, in FIG. 2, 4 is a power supply circuit whose output voltage has a constant polarity and is composed of a commercial power supply 1, a rectifier bridge 2, and a smoothing capacitor 3, 5 is a capacitor connected in series to the output, and 6 is a capacitor. 5 and the power supply circuit 4, a series circuit of a fluorescent lamp 7 and an inductance 8 is connected in parallel to the capacitor 5, and a capacitor 9 is connected in parallel to the opposite end of the fluorescent lamp 7 on the source side. An inductance 10 is connected. 11 is capacitor 5
This is a self-excited switching circuit consisting of a transistor 6, a capacitor 9, an inductance 8, and an inductance 10. 12 is an inductance which is a driving inductance with one end connected to the base of the transistor 6, and a series circuit of a secondary winding M8b of inductance 8 and a capacitor 13 which is a driving capacitor is connected between this other end and the emitter. Ru. 17 is a timer circuit consisting of a voltage dividing resistor 14.15 connected to the output end of the power supply circuit 4 and a capacitor 16 with one end connected to the midpoint thereof; 18 is a timer circuit with the other end of the capacitor 16 connected to the base and the collector as an inductance. A transistor 19 is a short-circuiting transistor connected in parallel to 12, and a diode 19 has a cathode connected to the base of the transistor 6 and the other end connected to the emitter of the transistor 6 via a resistor 20.

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 resistor 14, capacitor 16, and transistor 18 of the timer circuit 17
A starting current flows through the base of transistor 18 to conduct, and at the same time, the base current causes transistor 6 to conduct.
conducts.

Initially, the fluorescent lamp 7 is not lit, and current flows from the power supply circuit 4 through the transistor 6 via the inductance 8, the filament electrode of the fluorescent lamp 7, the capacitor 9, and the inductance 10. At this time, the inductance is 8
A positive voltage is generated in the secondary winding 8b of the transistor 6, and the base current of the transistor 6 is supplied through the capacitor 13 and the inductance 12, thereby keeping the transistor 6 on. At this time, the current flowing through the primary winding 8a of the inductance 8 is a resonant current between the capacitor 9 and the inductance 8. Here, 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.
In reality, since the transistor 18 is conductive, the current flows to some extent in the opposite direction from the emitter to the collector of the transistor 18, so the resonance state is weak and the inductance 12 hardly functions, so its oscillation period is close to the charging/discharging time of the capacitor 13. It becomes shorter.

Therefore, when the capacitor 13 is charged to near the voltage generated in the secondary winding 8b and the base current of the transistor 6 stops flowing, the base current of the transistor 6 is slightly pulled in the opposite direction due to the influence of the inductance 12.
is about to turn off, so the inductance 8b
When the voltage generated in the capacitor 13 becomes smaller, the charge accumulated in the capacitor 13 is fed back to the base and emitter of the transistor 6 in the opposite direction, and the transistor 6 is quickly turned off. When the transistor 6 is turned off, the energy stored in the series resonant circuit of the capacitor 9 and inductance 8 and the inductance 25 is released to the capacitor 5, the fluorescent lamp 7, the capacitor 9, the inductance 8, and the inductance 10, causing vibration, and preheating the fluorescent lamp 7. It becomes an electric current. At this time, settings are made so that the fluorescent lamp 7 is not started by the voltage generated in the capacitor 9. The oscillating current flowing through the primary winding 8a of the inductance 80 when the transistor 6 is off generates a negative voltage in the secondary winding 8b of the inductance 8. At this time, the transistor 18 conducts in the forward direction and the inductance 12 does not function at all, so this voltage causes the diode 19 and the resistor 20 to
A reverse voltage is applied between the base and emitter of the transistor 6 through the transistor 6 to keep the transistor 6 off. When the oscillating current passes a negative peak, a positive voltage is gradually generated in the secondary winding 8b of the inductance 8, and the voltage that was charged in the reverse direction in the capacitor 13 during the off period of the transistor 6 is transferred to the base of the transistor 6. The transistor 6 is turned on when the voltage is applied in the direction.

At this time, immediately after turn-on, the current in inductance 8 is still flowing in the opposite direction, so diode 19 and resistor 2
Current flows from the base to the collector through 0. The reverse current in the inductance 8 gradually decreases, and a forward current begins to flow through the transistor 6, and the above operation is repeated thereafter. Due to the above oscillation operation, the temperature of the preheating electrode of the fluorescent lamp 7 increases with the passage of time.

Note that the timer circuit 17 accumulates charge in the capacitor 16 via the resistor 14 after the power is turned on, and the transistor 18
When the capacitor 16 is charged to the voltage of the resistor 14.15 after a predetermined period of time, it is no longer charged, so from this point on, the power is cut off and the charge in the capacitor 16 is released via the resistor 14.15. No current flows to the base of transistor 18 until the current is reached. Therefore, when transistor 18 turns off after a predetermined time, transistor 6
When turned on, a positive voltage is generated in the secondary winding 8b of the inductance 8, and the base current of the transistor 6 is supplied via the capacitor 13 and the inductance 12. This base current is a resonant current of the capacitor 13 and the inductance 12, and around the half cycle, the base current of the transistor 6 changes from positive to negative, and when the accumulated charge of the transistor 6 is released, the transistor 6 is turned off. Before starting the fluorescent lamp 7, the inductance 8 and the capacitor 9 are in a series resonant circuit, and the capacitor 9 has a voltage which is much larger than when the lamp is turned on and larger than during preheating before the timer circuit operates.
Each inductance and capacitor is set to generate sufficient voltage to start the fluorescent lamp 7. Therefore, the fluorescent lamp 7 is started.

After starting, the operation of the circuit is almost the same as after the operation of the timer circuit 17, but since the impedance of the fluorescent lamp 7 is connected in parallel with the impedance of the capacitor 9 and the inductance 10, the current of the capacitor 9 decreases and the fluorescent lamp 7 Current flows. Therefore, the resonance between the inductance 8 and the capacitor 9 is almost eliminated, and the 2nd half of the inductance 8
Positive and negative voltages are generated in the next winding 8b according to the difference between the output voltage of the power supply circuit 4 and the lamp voltage, and the transistor 6 is turned on and off to keep the fluorescent lamp 7 lit. Note that the inductance 10 is for removing the DC component of the current of the fluorescent lamp 7.

Further, when the fluorescent lamp 7 cannot be lit normally, such as at the end of its life, the circuit becomes in the same operating state (resonant state) as when the starting voltage is generated after the timer circuit 17 operates. Furthermore, when the fluorescent lamp 7 is removed, no current flows through the inductance 8, so the transistor 6 is not turned on and does not oscillate.

Problems to be Solved by the Invention However, in the above configuration, when the fluorescent lamp 7 is started or in an abnormal state such as at the end of its life, the impedance of the fluorescent lamp 7 is large and changes rapidly and irregularly. Therefore, not only does the resonance generated between the series resonant circuit of capacitor 9 and inductance 8 and the inductance 5 and capacitor 6 increase, but also changes in the inductance value of inductance 12, changes in the storage time of transistor 6, and malfunction of transistor 18 occur. There were problems such as periodic deviations caused by such factors, causing abnormal oscillation, which could lead to circuit destruction.

Means for Solving the Problems In order to solve the above problems, the present invention provides a power supply whose output voltage has a constant polarity, and at least one main transistor, inductance, and capacitor connected to the output terminal of the power supply. a self-excited switching circuit that starts and lights a discharge lamp connected to an output terminal by turning on and off a forward current from the power source using the main transistor;
a series circuit comprising at least a secondary winding of the inductance, a driving inductance, and a driving capacitor connected between the base and emitter of the main transistor and driving the main transistor; and a collector-emitter connected in parallel to the driving inductance. a Zener diode connected such that a base current flows through a Zener voltage between the collector and base of the short-circuiting transistor, and an output to the base such that the short-circuiting transistor is turned off after a predetermined time. and a connected timer circuit.

Effect of the Invention With the above-described configuration, the present invention uses the Zener diode and the transistor 18 to absorb the surge voltage generated in the inductance 12 when the transistor 6 is switched, and the abnormal voltage generated in the inductance 12 when the resonance condition becomes thick during startup or abnormality. At the same time, the forward characteristics of the Zener diode installed between the collector and base of the transistor 18 are used to prevent the transistor 18 from malfunctioning.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of the discharge lamp lighting device of the present invention. In Figure 1, from commercial power supply 1 to resistor 20
Up to this point, the configuration and operation are the same as the conventional example. The difference from the conventional example is that a Zener diode 21 is connected between the collector and base of the transistor 18 so that the base current flows through the Zener voltage. 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 resistor 14 of the timer circuit 17
A starting current flows through the capacitor 16 and the Zener diode 21 in the forward direction, and the transistor 6 becomes conductive. At this time, the base-emitter voltage of the transistor 18 is suppressed below the forward voltage of the Zener diode 21, so the transistor 18 is almost in an off state. Initially, the fluorescent lamp 7 is not lit, and current flows from the power supply circuit 4 through the transistor 6 via the inductance 8, the filament electrode of the fluorescent lamp 7, the capacitor 9, and the inductance 10. At this time, a positive voltage is generated in the secondary winding 8b of the inductance 8, and the base current of the transistor 6 is supplied via the capacitor 13 and the inductance 12, thereby keeping the transistor 6 on. At this time, the current flowing through the primary winding 8a of the inductance 8 is a resonant current between the capacitor 9 and the inductance 8.

At this time, the base-collector voltage of the transistor 18 is suppressed below the forward voltage of the Zener diode 21, so the transistor 18 can be almost turned off. Therefore, the current flowing due to the positive voltage generated in the secondary winding 8b of the inductance 8 is the inductance 12.
can be ensured to pass through, and can be the initial transient current of the series resonant current at the natural vibration frequency of the inductance 12 and capacitor 18. Therefore, the inductance 1
2, the capacitor 18 is charged to a voltage higher than the voltage generated in the secondary winding 8b, the base current of the transistor 6 stops flowing, and then the base current of the transistor 60 can be made large and reliably drawn in the opposite direction. . Therefore, the transistor 6 is about to turn off, and when the voltage generated in the inductance 8b becomes small, the charge accumulated in the capacitor 13 is fed back in the opposite direction between the base and emitter of the transistor 6, and the transistor 6 is quickly turned off. do. When the transistor 6 is turned off, the energy stored in the series resonant circuit of the capacitor 9 and the inductance 8 and the inductance 25 is released to the capacitor 5, the fluorescent lamp 7, the capacitor 9, the inductance 8, and the inductance 10, causing the fluorescent lamp 7 to vibrate.
The preheating current will be . As described above, activation of the circuit can be ensured. Further, the oscillating current flowing through the primary winding 8a of the inductance 8 when the transistor 6 is off generates a negative voltage in the secondary winding 8b of the inductance 8. At this time, the transistor 18 conducts in the forward direction and the inductance 12 does not function at all, so this voltage applies a reverse voltage between the base and emitter of the transistor 6 via the diode 19 and the resistor 20, turning off the transistor 6. maintain. At the same time, the capacitor 13 is significantly charged in the opposite direction via the transistor 18. When the oscillating current passes the negative peak, the inductance gradually decreases to 2 of 8.
Next, the negative voltage of the winding 8b decreases, and the voltage charged in the reverse direction to the capacitor 13 during the off period of the transistor 6 is applied in the forward direction to the base of the transistor 6 through the inductance 12, and the transistor 6 is turned on. do. At this time, immediately after turn-on, the current in inductance 8 is still flowing in the opposite direction, so diode 19 and resistor 20
Current flows from the base to the collector through.

The reverse current in the inductance 8 gradually decreases, and a forward current begins to flow through the transistor 6, and the above operation is repeated thereafter. In this case, when the negative voltage across the secondary winding 8b decreases, the capacitor 13 is charged in the opposite direction to around the voltage generated across the secondary winding 8b, and the transistor 6
turns on immediately and the turn-on timing becomes faster, so the off-period of the transistor 6 is shortened, and furthermore, during the on-time of the transistor 6 due to the resonance between the inductance 12 and the capacitor 13, the current flows in the forward direction from the collector to the base. Since the period becomes shorter, the energy stored in the inductance 8 when the transistor 6 is turned off decreases, thereby maintaining a small resonance state. Note that at this time, the fluorescent lamp 7 is connected to the capacitor 9.
Set it so that it will not start with the voltage generated.

Due to the above oscillation operation, the temperature of the preheating electrode of the fluorescent lamp 7 increases with the passage of time.

Note that the timer circuit 17 accumulates charge in the capacitor 16 via the resistor 14 after the power is turned on, and the transistor 18
When the capacitor 16 is charged to the voltage of the resistor 14.15 after a predetermined period of time, it is no longer charged, so from this point on, the power is cut off and the charge in the capacitor 16 is released via the resistor 14.15. No current flows to the base of transistor 18 until the current is reached. Therefore, when the transistor 18 is turned off after a predetermined time, a positive voltage is generated in the secondary winding 8b of the inductance 8 when the transistor 6 is turned on, and the base current of the transistor 6 is supplied via the capacitor 13 and the inductance 12. This base current is a resonant current of the capacitor 13 and the inductance 12, and around the half cycle, the base current of the transistor 6 changes from positive to negative, and when the accumulated charge of the transistor 6 is released, the transistor 6 is turned off. Before starting the fluorescent lamp 7, the inductance 8 and the capacitor 9 are in a series resonant state, and the capacitor 9 has a voltage that is much larger than when the lamp is turned on and larger than that during preheating before the timer circuit operates. Set each inductance and capacitor to generate sufficient voltage. Therefore, the fluorescent lamp 7 is started. Note that at this time, since the secondary winding voltage of the inductance 8 increases, the transistor 6
The current in the base circuit also increases. Therefore, when the base current discontinuously occurs during switching of the transistor 6, the surge voltage generated in the inductance 12 also increases, and the surge voltage is applied between the base and emitter of the transistor 6 in the forward direction to cause malfunction. The surge voltage can be suppressed by the Zener voltage of the transistor 18 and the Zener diode 21 which are connected in parallel to the transistor 18 and the Zener diode 21. (The same applies during preheating and lighting.) Furthermore, as the resonance of the base circuit of the transistor 6 increases, the current peak value of the inductance 12 and the voltage peak values of the inductance 12 and the capacitor 13 tend to increase. 6 is off, if the potential on the cociancer 13 side of the inductance 12 becomes abnormally high, the transistor 18 and the Zener diode 21 connected in parallel with the inductance 12 turn on the transistor 18 with the Zener voltage to suppress it, and also blows out the inductance 12. Capacitor 13f: Immediately charges the capacitor 13f and changes the phase of the resonant current so that the turn-on timing of the transistor 6 can be delayed.

Therefore, the current peak value and voltage peak value of the inductance 12 can be reduced by suppressing the resonance of the inductance 8 and the capacitors 5 and 9, so that a small rated inductance can be used for the inductance 12, and the magnetic saturation of the inductance 12 can be reduced. Can prevent circuit oscillation abnormalities. Furthermore, since the base current of the transistor 6 can be prevented from becoming too large, the storage time of the transistor 6 can be prevented from becoming extremely long, and abnormal oscillation of the circuit due to a prolonged on time of the transistor 6 can be prevented. In addition, in this case, the transistor 18
The emitter potential of can be held below a predetermined voltage,
The voltage applied in the opposite direction to the base and emitter of the transistor 18 can be reduced. Therefore, an inexpensive transistor can be used for the transistor 18, and reliability is also improved. Next, when the transistor 6 is on, even if the potential on the capacitor 13 side of the inductance 12 rises, the Zener diode 21 is inserted between the collector and emitter of the transistor 18 in the forward direction, so the accumulation of the transistor 18 is reduced. Since the charge can be quickly discharged to the collector and the lamp can be prevented from turning on, malfunction of the circuit can be prevented.

After starting, the circuit operates in the timer cycle! ! Almost the same as after the operation of 817, the impedance of the fluorescent lamp 7 is connected in parallel with the impedance of the capacitor 9 and the inductance 10, so the current in the capacitor 9 decreases and the current flows through the fluorescent lamp 7. Therefore, the resonance between the inductance 8 and the capacitor 9 is almost eliminated, and the inductance 8
A positive and negative voltage is generated in the secondary winding 8b according to the difference between the output voltage of the power supply circuit 4 and the lamp voltage. The transistor 6 is turned on and off to keep the fluorescent lamp 7 lit.

In addition, in the above, the output voltage of the power supply circuit 4 is obtained by rectifying and smoothing the commercial power supply 1, so it contains some ripples, and the output voltage of the power supply circuit 4 includes some ripples.
In the conventional example, the ripple is supplied as the base current of the transistor 18, causing malfunction of the transistor 18, but in this embodiment, the current passes through the Zener diode 21, so the ripple is supplied as the base current of the transistor 18.
8 malfunctions can be prevented from occurring. Therefore, it is possible to use the power supply circuit 4 and the timer circuit 17 that include output ripples.

In addition, when the fluorescent lamp 7 cannot be lit normally, such as at the end of its life, the circuit becomes in the same operating state (resonant state) as when the starting voltage is generated after the timer circuit 17 operates, or when the fluorescent lamp 7 is removed. In this case, since no current flows through the inductance 8, the transistor 6 is not turned on and does not oscillate.

As described above, in this embodiment, the inductance 1
Transistor 18 and Zener diode 21 in parallel to 2
A simple and inexpensive configuration that only requires an inductance of 1
The voltage applied to capacitor 2 and capacitor 13 can be reduced, and abnormal oscillation of the circuit due to malfunction of transistors 6 and 18 or magnetic saturation of inductance 12 can be prevented. Additionally, the circuit can be started up reliably. Furthermore, in this embodiment, since the timer output ripple caused by the power supply ripple can be absorbed, the power supply circuit 4 and the timer output ripple can be absorbed! 817 that includes an output ripple can be used, and the configuration can be made simple and inexpensive, and stable starting and lighting can be achieved.

In this embodiment, a fluorescent lamp is used as the discharge lamp, but similar effects can be obtained with other lamps such as a high-pressure discharge lamp that does not require preheating. Further, the self-excited switching circuit section may be of the one-stone type or the two-stone type. Further, the timer circuit 17 may be of another type. Further, although the secondary winding 8b with the inductance 8 is used as the power source for driving, the same effect can be obtained even if the power is supplied from another inductance.

As described in detail, the present invention can realize a discharge lamp lighting device that can reliably start a transistor and a circuit with a simple and inexpensive circuit configuration, prevent malfunctions, and prevent abnormal oscillations.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional discharge lamp lighting device. DESCRIPTION OF SYMBOLS 1... Commercial power supply, 4... Power supply circuit, 8... Inductance, 7... Fluorescent lamp, 6... Main transistor, 12... Drive inductance, 13... Drive capacitor, 17...Timer circuit

Claims (1)

[Claims] A power source whose output voltage has a constant polarity, and at least one main transistor, an inductance, and a capacitor connected to the output terminal of the power source, and a forward current to the power source is turned on and off by the main transistor. a self-excited switching circuit that starts and lights a discharge lamp connected to an output terminal; and at least a secondary winding of the inductance and a driving inductance that are connected between the base and emitter of the main transistor and drive the main transistor. A series circuit consisting of a driving capacitor, a shorting transistor whose collector and emitter are connected in parallel to the driving inductance, and a collector and base of the shorting transistor connected so that a base current flows through a Zener voltage. A discharge lamp lighting device comprising a Zener diode and a timer circuit having an output connected to its base so as to turn off the shorting transistor after a predetermined time.