JPH0211996B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a discharge lamp lighting device, and its purpose is to prevent a large current from flowing into the main circuit during the glow period immediately after starting, and to prevent a large current from flowing into the main circuit. The purpose is to improve the reliability of parts and prevent deterioration of lamp life.

Fig. 1 is a circuit diagram showing a conventional discharge lamp lighting device, in which a series circuit of an AC control element S ₁ , a current limiting inductance CH 2 , and a discharge lamp L is connected to an AC power source E, and a series circuit of an AC control element S 1 , a current limiting inductance CH ₂ and a discharge lamp L is connected to both ends of the AC control element S ₁ . Connect the series circuit of capacitor C ₇ and resistor R ₁₇ and auxiliary choke CH ₁ . 1 is a reference voltage generation circuit, in which a series circuit of a resistor R ₁ and a capacitor C ₁ is connected to an AC power supply E, and a series circuit of a resistor R ₂ and a capacitor C ₂ is connected across the capacitor C ₁ .
A series circuit of resistor R ₃ and capacitor C ₃ is connected across capacitor C ₂ , and both ends of capacitor C ₃ are connected to the input terminal of full-wave rectifier circuit DB ₁ . full wave rectifier circuit
A resistor _{R 4} is connected to the output terminal of DB ₁ , and a reference voltage whose phase is advanced from the voltage waveform of the AC power supply E shown in FIG. 2 e is obtained across the resistor R 4 as shown in FIG. 2 a.
2 is a lamp voltage detection circuit, which detects the voltage across the discharge lamp L and generates _a DC voltage corresponding to the average value.
Connect the secondary winding, connect the secondary winding to the input terminal of the full-wave rectifier circuit DB ₂ , connect the series circuit of resistors R ₁₂ and R ₁₃ to the output terminal of the full-wave rectifier circuit DB ₂ , and connect the secondary winding to the input terminal of the full-wave rectifier circuit DB 2. A smoothing capacitor _C5 is connected in parallel to obtain the DC voltage _V1 shown in Fig. 2b. 3 is a comparator circuit that generates a pulse by comparing the reference voltage obtained by the reference voltage generation circuit ₁ and the DC voltage obtained by the lamp voltage detection circuit ₂ . Connect this connection point and the full wave rectifier circuit
Connect a resistor R ₁₁ between the negative output terminal of DB ₂ (hereinafter referred to as the ground line). The anode of diode D ₁ is connected to the positive output terminal of lamp voltage detection circuit 2, and the anode of diode D ₂ is connected to transistor Tr ₁
Connect the series circuit of resistors R ₉ and R ₁₀ between the collector of transistor Tr ₁ and the earth line. The emitter of transistor Tr ₁ is connected to the positive output terminal of full-wave rectifier circuit DB ₁ . transistor
Connect resistor _R8 between the emitter and vane of Tr ₁ .
The base of transistor Tr ₂ is connected to the connection point of resistors R ₉ and R ₁₀ , the emitter of transistor Tr ₂ is connected to the ground line, and the capacitor C ₄ and the primary winding of pulse transformer T ₈ are connected between the collector and the ground line. The secondary windings of the pulse transformer T ₃ are connected to the gate and cathode of the AC control element S ₁ via a diode D ₃ and a resistor R ₁₆ , respectively. Programmable to collector of transistor Tr ₂ . Connect the anode of the unidirectional transistor S ₂ (hereinafter referred to as PUT) and connect the cathode to the ground line. PUT (S ₂ ) to the connection point of resistors R ₅ and R ₆
Connect the gate of , connect the other end of the resistor R ₆ to the ground line, and connect the ground line to the negative output end of the full-wave rectifier circuit DB ₁ . 4 is a power supply circuit, in which the primary winding of transformer T ₂ is connected to both ends of current limiting inductance CH ₂ , the input end of full-wave rectifier circuit DB ₃ is connected to the secondary winding, and full-wave rectifier circuit DB ₃ is connected to the secondary winding. Connect the resistor _R14 to the positive output end of the resistor R14, and connect the capacitor to the other end of the resistor _R14 .
C ₆ and resistor R ₁₅ are connected, and the other end of capacitor C ₆ is connected to the negative output of full-wave rectifier circuit DB ₃ . Resistance R ₁₅
Connect the cathode of the Zener diode ZD to the other end, connect the anode to the negative output end of the full-wave rectifier circuit DB ₃ , and connect the connection point to the earth line. Resistor from cathode of Zener diode ZD
It is connected to the collector of transistor Tr ₂ via R ₇ , and the connection point of resistors R ₁₄ and R ₁₅ is connected to resistor R ₅ .

Now, when the discharge lamp L is lit, the reference voltage generated by the reference voltage generation circuit ₁ as shown in FIG. D ₁ , D ₂ , transistor
Comparing the circuit of Tr ₁ , at the point where the reference voltage is lower than the DC voltage V ₁ (hereinafter referred to as the intersection point), the transistor
Tr ₁ is turned off, and at the same time, transistor Tr ₂ is also turned off. From that point on, the capacitor C ₄ is charged with a constant voltage from the power supply circuit 4 via the resistor R ₇ as shown in FIG. 2c. On the other hand, the voltage supplied from the power supply circuit 4 is divided by resistors R ₅ and R ₆ , and the voltage of resistor R ₆ , i.e.
When the gate voltage of PUT (S ₂ ) and the charging voltage of capacitor C ₄ , that is, the anode voltage of PUT (S ₂ ) become equal, PUT (S ₂ ) turns on and the charge of capacitor C ₄ decreases.
PUT (S ₂ ), discharged through the pulse transformer T ₃ ,
A pulse as shown in FIG. 2d is generated on the secondary side of the pulse transformer _T3 to make the AC control element _S1 conductive.

Immediately after the discharge lamp L is started, it passes through an unstable period called a glow period and then transitions to arc discharge, but this glow period lasts for several seconds, and at this time the state of the discharge lamp L is unstable. The lamp voltage changes greatly, and when it enters a half-wave lighting state in which only one half wave is conductive and the second half is non-conductive, it becomes a so-called direct current, and the impedance of current limiting inductance CH ₂ decreases, causing a large amount of damage to the main circuit. Current flows. At this time, since the lamp voltage is unstable, the point of intersection of the conduction phase angle of the AC control element _S1 with the aforementioned reference voltage fluctuates, and the fluctuation does not work to narrow down the lamp current.

If a large current flows in the half-wave lighting state during the glow period, even for a few seconds, the overcurrent may flow through the AC control element S ₁ and current limiting inductance CH ₂ that make up the main circuit, causing thermal damage. Yes, also
This had the disadvantage that it adversely affected the life of the discharge lamp L.

The present invention has been made in view of these points,
Hereinafter, it will be explained in detail using examples.

FIG. 3 is a circuit diagram showing an embodiment of the present invention, in which the reference voltage generation circuit 1, comparison circuit 3, and power supply circuit 4 are the same as those in FIG. 1, and the lamp voltage detection circuit is similar to that in FIG. A series circuit of a resistor R ₂₂ and the collector-emitter of a transistor Tr ₃ is connected to both ends of the capacitor C ₅ , which is the output terminal of the lamp voltage detection circuit 2, and the base and emitter of the transistor Tr ₃ are connected via a resistor R ₂₁ . do. The anode of thyristor S ₃ is connected to the base of transistor Tr ₃ , the cathode of thyristor S ₃ is connected to the emitter of transistor Tr ₃ , and the gate of thyristor S ₃ is connected to resistor R _19.
Connect to the ground line via. And the power supply circuit 4 is a resistor R ₂₀ across the Zener diode ZD.
and capacitor C ₈ are connected in series, and the connection point of resistor R ₂₀ and capacitor C ₈ is connected to the gate of thyristor S ₃ via diagonal S ₄ , and the cathode of Zener diode ZD is connected to the transistor Tr via resistor R ₁₈ . Connect to the base of ₃ . The other configurations are the same as the conventional example.

Next, the operation will be explained. When the discharge lamp L starts after the power is turned on, a voltage is generated across the current limiting inductance CH ₂ , so a base current flows from the output terminal of the power supply circuit 4 to the transistor Tr ₃ of the lamp voltage detection circuit through the resistor R ₁₈ , and the transistor Tr Make ₃ conductive. Therefore, the output voltage of the lamp voltage detection circuit becomes zero, and the point of intersection with the reference voltage is point b in Figure 2b, and the conduction phase angle of AC control element _S1 is fixed with a delay, so the lamp current is narrowed down. work like that. On the other hand, capacitor _C8 is charged with a constant voltage through resistor _R20 from the start-up, and when the charging voltage exceeds the breakover voltage of diac _S4 , diac _S4 becomes conductive and triggers the gate of thyristor _S3 . This trigger causes thyristor _S3 to conduct, turning off transistor _Tr3 .
After that, the thyristor _S3 remains conductive, so the transistor _Tr3 remains off, and the lamp voltage detection circuit outputs a DC voltage corresponding to the lamp voltage, as in the conventional circuit.

Therefore, by appropriately setting the values of capacitor C ₈ and resistor R ₂₀ , the output terminal of the lamp voltage detection circuit is short-circuited for several seconds after startup, the lamp current is throttled, and then the lamp voltage detection circuit detects the lamp voltage. generates a DC voltage corresponding to In other words, the lamp current is reduced during the glow period that lasts for several seconds after the lamp is started, and a large current no longer flows through the main circuit even in the half-wave lighting state that occurs during this period.

Next, FIG. 4 is a circuit diagram showing a different embodiment of the present invention, in which the main circuit, reference voltage generation circuit 1, comparison circuit 3
is equivalent to that in FIG. Silicon _. Symmetrical. Connect one end of switch (hereinafter referred to as SSS) _S5 , and connect the other end to the ground line via capacitor _C9 . Resistor R ₂₅ across capacitor C ₉
Connect the series circuit of resistor R ₂₃ with resistor R ₂₅ and resistor
Connect the base of transistor Tr ₄ to the connection point of R ₂₃ . and the collector of resistor R ₂₄ and transistor Tr ₄ . A series circuit of emitters is connected to the output terminal of the lamp voltage detection circuit 2. The other configurations are the same as the conventional example.

To explain the operation of such a lighting device, as described above, during the glow period, the discharge lamp L is in an unstable state, the lamp voltage changes irregularly, and the lamp current also changes. When the lamp current tries to commutate, the lamp conductance decreases rapidly when the current becomes small, and the reason why the lamp current changes suddenly as shown in Figure 5a is during the glow period, as in half-wave lighting. This is one of its characteristics.

Due to the sudden change in the lamp current, a high voltage Ldi/dt is generated across the current limiting inductance CH ₂ , and a transformer is generated at the output end of the full-wave rectifier circuit DB ₃ .
A voltage with a full-wave rectified waveform as shown in FIG. 5b, which is stepped down by T ₂ , is output. Since this output voltage is lower in the arc discharge state than in the glow discharge state, the breakover voltage of SSS (S ₅ ) is determined by the peak value of the output voltage of the full-wave rectifier circuit DB ₃ during the arc state, V _DB3 peak. By setting it larger than the peak value V _DB3 peak during glow discharge, the current limiting inductance during glow discharge can be reduced.
When high voltage occurs on CH ₂ , SSS (S ₅ ) turns on,
The capacitor C ₉ is charged with an electric charge, which is discharged through the resistor R ₂₅ and causes the base current of the transistor Tr ₄ to flow, turning the transistor Tr ₄ on. Therefore, the output terminal of the lamp voltage detection circuit 2 is short-circuited, and as described above, the intersection point with the reference voltage is b in FIG. 2b.
Since the conduction phase angle of the AC control element _S1 is fixed with a delay, it works to narrow down the lamp current. Then, after the glow period has passed, the output voltage V _DB3 peak of the full-wave rectifier circuit DB ₃ becomes smaller than the breakover voltage of SSS (S ₅ ), so this circuit stops operating. Therefore, as in the previous embodiment, no large current flows through the main circuit during the glow period.

As described above, the discharge lamp lighting device of the present invention is a reference voltage generation circuit that connects an AC control element, a current limiting inductance, and a series circuit of a discharge lamp to an AC power source, and generates a reference voltage that is a certain phase ahead of the AC power source. a lamp voltage detection circuit that detects the voltage across the discharge lamp and generates a DC voltage corresponding to the average value; and a lamp voltage detection circuit that generates a pulse by comparing the reference voltage and the output voltage of the lamp voltage detection circuit and generates a pulse. In a discharge lamp lighting device comprising a comparison circuit that triggers a control element and a power supply circuit that detects the voltage across the current limiting inductance and supplies power to the comparison circuit, the lamp voltage is controlled for a certain period of time after the discharge lamp is started. By providing means for short-circuiting the output terminal of the detection circuit, the output terminal of the lamp voltage detection circuit is short-circuited and the lamp current is narrowed down during the glow period immediately after the discharge lamp is started. Therefore, even in the half-wave lighting state that occurs during the glow period, a large current will not flow through the main circuit, and there will be no thermal damage to the AC control element and current limiting inductance that constitute the main circuit. Furthermore, it was possible to provide a discharge lamp lighting device with significantly improved reliability, such as no adverse effect on the life of the discharge lamp.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional discharge lamp lighting device.
Fig. 2 is a waveform diagram of each part of the above device, Fig. 3 is a circuit diagram showing one embodiment of the present invention, Fig. 4 is a circuit diagram showing a different embodiment of the present invention, and Fig. 5 is a start-up diagram in the same device. lamp current and full wave rectifier circuit
FIG. 3 is a waveform diagram of the output voltage of DB ₃ .

Claims (1)

[Scope of Claims] 1. A reference voltage generation circuit that connects an AC control element, a current limiting inductance, and a series circuit of a discharge lamp to an AC power source, and generates a reference voltage that is a certain phase ahead of the AC power source; A lamp voltage detection circuit that detects the voltage at both ends and generates a DC voltage corresponding to the average value thereof, and a comparison that generates a pulse by comparing the reference voltage and the output voltage of the lamp voltage detection circuit to trigger the AC control element. In a discharge lamp lighting device comprising a circuit and a power supply circuit that detects the voltage across the current limiting inductance and supplies power to the comparison circuit, the output end of the lamp voltage detection circuit is switched off for a certain period of time after the discharge lamp is started. A discharge lamp lighting device characterized by being provided with means for short-circuiting. 2. The discharge lamp lighting device according to claim 1, characterized in that a timer circuit is provided at the output end of the power supply circuit to short-circuit the output end of the lamp voltage detection circuit for a certain period of time after the discharge lamp starts. . 3. The discharge lamp according to claim 1, wherein the output end of the lamp voltage detection circuit is short-circuited for a certain period of time after the discharge lamp starts by detecting the absolute value of the voltage across the current-limiting inductance. lighting device.