JP3246083B2 - Discharge lamp lighting device - Google Patents

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.

[0002]

2. Description of the Related Art Conventional lighting devices for discharge lamps include:
As shown in FIG. 4, the chopper circuit 4 and the inverter circuit 5
A circuit that shares a switching element is known.
Thus, the input power factor of the voltage input to the discharge lamp 6 is increased, and the harmonic components are reduced.

The circuit configuration of the above-described conventional discharge lamp lighting device will be described. Inverter circuit 5 includes transistors 50 and 51 connected in series and transistor 5
Diodes 50 connected in anti-parallel to 0 and 51, respectively.
a, 51a, a series circuit of capacitors 52, 53, and feedback windings 54ca, 5 for driving the transistors 50, 51.
4cb, the output winding 54b connected to the discharge lamp 6
And the connection point of the transistors 50 and 51 and the capacitor 5
A transformer 54 having a primary winding 54a connected between the connection points 2 and 53, and resistors 55, 56, 57 and 58
It is composed of The chopper circuit 4 is connected to the AC power supply 1 via the noise filter 2 and the rectifier circuit 3, and is connected between the smoothing capacitor 41, the transistor 50, and the output terminal of the transistor 50 and the rectifier circuit 3. And a diode 51a for flowing a charging current from the connection point between the inductance element 42 and the transistor 50 to the smoothing capacitor 41 (JP-A-3-276598).

Next, the operation of the above circuit will be described. When a full-wave rectified DC pulsating voltage is applied to the chopper circuit 4 from the AC power supply 1 via the noise filter 2 and the rectifier circuit 3, the inductance element 42 is added to the smoothing capacitor 41.
Is charged through the diode 51a. For example, resistor 5
A start-up current flows through 6 to turn on the transistor 50. When the transistor 50 is turned on, the smoothing capacitor 4
1 flows through the capacitor 53 and the transformer 54a, and the transformer 54 of the inverter circuit 5 and the capacitor 5a.
The resonance system composed of 2, 53 starts to vibrate. for that reason,
A voltage is generated in the feedback windings 54ca and 54cb of the transformer 54 so that the transistor 50 is turned on and the transistor 51 is turned off, the transistor 50 is kept on, and the transistors 50 and 51 are turned on and off with the vibration of the resonance system. Is alternately repeated. When the transistor 50 is on,
A current limited by the inductance element 42 flows from the AC power supply 1 via the inductance element 42, and this current increases with time. In addition, this current, and
The current flowing from the smoothing capacitor 41 via the resonance system simultaneously flows into the transistor 50, and this current increases with time. Next, when the transistor 50 is turned off, the energy stored in the inductance element 42 immediately before the turn-off is discharged to the smoothing capacitor 41 via the diode 51a. At the same time, when the transistor 50 is turned off, the transistor 51 is turned on, the resonance system continues to oscillate, and continues to supply voltage and energy to the discharge lamp 6. Due to the vibration of the resonance system, the transistor 5
1 turns off and the transistor 50 turns on. Thereafter, the chopper circuit 4 and the inverter circuit 5 repeat the above operation,
The discharge lamp 6 is kept on.

In this operation, when the instantaneous value of the AC power supply 1 is low, the rate of increase of the current flowing through the inductance element 42 is low.
The energy stored in the inductance element 42 at the time of turn-off of 0 is small, and the charging voltage of the smoothing capacitor 41 also decreases. At this time, the input current also decreases according to the instantaneous value of the AC power supply 1. When the instantaneous value of the AC power supply 1 is high, an operation opposite to that when the instantaneous value is low is performed. That is, the increase rate of the current flowing through the inductance element 42 is high,
If the ON time is always the same, the energy stored in the inductance element 42 when the transistor 50 is turned off is large, and the charging voltage of the smoothing capacitor 41 increases. The input current also increases according to the instantaneous value of the AC power supply 1. Therefore, an input current having a substantially similar shape to the waveform of the AC power supply 1 can be obtained, the power input power factor can be increased, and harmonic components of the power supply input current can be reduced.

[0006]

However, in such a conventional discharge lamp lighting device, when the transistor 50 does not operate due to a component failure or a solder failure, the voltage of the smoothing capacitor 41 rises abnormally, There was a risk that it would burst. For this reason, it is conceivable to take measures to improve the performance of components or to provide a protection circuit, but there is a problem that the components are large and expensive.

SUMMARY OF THE INVENTION The present invention provides a compact and simple structure having a high input power factor and a low harmonic component of a power supply input current.
An object of the present invention is to provide a discharge lamp lighting device capable of safely starting and maintaining the discharge lamp.

[0008]

According to a first aspect of the present invention, there is provided a discharge lamp lighting device comprising: a closed circuit including a discharge lamp, a resonance capacitor, a first inductance element, and a first switch element; one end of which is one end of the first switch element. A second switch element connected between the other end of the first switch element and the other end of the smoothing capacitor;
A rectifier connected between a connection point between the first switch element and the second switch element and a connection point between the smoothing capacitor and one end of the first switch element; An AC power supply to be connected via a second inductance element between a connection point with a second switch element and a connection point between the first switch element and the second switch element. Rectifier circuit, and a connection point between the second inductance element and the rectification circuit, and a connection point between the smoothing capacitor and one end of the first switch element to provide a predetermined breakdown characteristic. Semiconductor switch.

[0009]

According to the present invention, a predetermined breakdown characteristic is provided between a connection point between the second inductance element and the rectifier circuit and a connection point between the smoothing capacitor and one end of the first switch element. When the voltage of the smoothing capacitor rises abnormally due to the connection of the semiconductor switch, the semiconductor switch is broken down to serve as a discharge circuit for the smoothing capacitor. Decrease the voltage of the capacitor.

Further, the heat generation of the second switch element is promoted and destroyed, and the fuse is cut off.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the discharge lamp lighting device according to the embodiment has a closed circuit including a discharge lamp 78, a capacitor 76 as a resonance capacitor, a first inductance element 77, and a first switch element 74. The smoothing capacitor 71 connected to one end of the first switch element 74
A second switch element 75 connected between the other end of the switch element 74 and the other end of the smoothing capacitor 71; a connection point between the first switch element 74 and the second switch element 75; Rectifying means 72 connected between the first switching element 74 and a connection point with one end of the first switching element 74; a connection point between the smoothing capacitor 71 and the second switching element 75;
A rectifier circuit 3 to be connected to the AC power supply 1 via the fuse 32 at the connection point between the first switch element 74 and the second switch element 75 via the second inductance element 9
The portions connecting the output terminals of the output terminals 1 are the same as those in the conventional example. What is different from the conventional example is the connection point between the second inductance element 9 and the rectifier circuit 31 and the smoothing capacitor 71.
That is, the semiconductor switch 10 having a predetermined breakdown voltage is connected between the first switch element 74 and a connection point with the first switch element 74.

That is, a rectifier circuit 31 for rectifying an AC power supply voltage is connected to the AC power supply 1 at one of its input terminals via a fuse 32, and one of its output terminals is connected to one end of an inductance element 9 via a filter circuit 2. And the other is connected to the emitter of transistor 75. In the filter circuit 2, an inductance element 21 is connected in series to an output terminal of a rectifier circuit 31, a diode 22 is connected in series to the output terminal in a forward direction, and a connection point between the inductance element 21 and the diode 22 is connected to the rectifier circuit 3. Is connected to the other end of the output terminal. The inverter circuit 7 connected from the filter circuit to the semiconductor switch 10 via the inductance element 9 includes a transistor 74
And a transistor 75, form a series circuit, and a smoothing capacitor 71 is connected in parallel with the series circuit. Diodes 72 and 73 are connected in anti-parallel to a series circuit composed of transistors 74 and 75, respectively. A transistor 74 includes a resonance capacitor 76, a fluorescent lamp 78, an inductance element 77, and a primary winding of a current transformer. 87a are connected in parallel. The capacitor 79 is connected in parallel via a preheating electrode of the fluorescent lamp 78. This inverter circuit 7 has L which is generated by the on / off operation of the transistors 74 and 75.
The DC input from the smoothing capacitor 71 is converted into AC using the C resonance, that is, the resonance generated by the inductance element and the capacitor, and supplied to the fluorescent lamp 78. The drive control means 8 for controlling the driving of the transistors 74 and 75 by the output of the current transformer 87 connected to the transistor 75 of the inverter circuit 7 includes the current transformer 87
Is connected between the output terminal of the secondary winding 87b and the base of the transistor 74 via a resistor 86, and is connected between the output terminal of the secondary winding 87c and the base of the transistor 75 via a resistor 85. are doing. A series circuit including a resistor 81 and a capacitor 84 is connected in parallel with the capacitor 23 of the filter circuit 2, and is connected from the connection point of the series circuit to the base of the transistor 75 via the trigger element 83.

Next, the operation of such a discharge lamp lighting device will be described. When a full-wave rectified DC pulsating voltage is applied from the AC power supply 1 via the rectifier circuit 3 and the noise filter 2, the smoothing capacitor 71 is charged via the diode 10. At the same time, when the capacitor 84 is charged via the resistor 81 and the voltage reaches the breakdown voltage of the trigger element 83, the charge of the capacitor 84 is supplied to the base of the transistor 75, and the transistor 75 is turned on. When the transistor 75 is turned on, current flows from the smoothing capacitor 71 through the capacitor 76, the capacitor 79, the inductance element 77, and the current transformer 87 while increasing, and the resonance system including the transformer 77 and the capacitor 76 of the inverter circuit 7 starts oscillating. . Therefore, the secondary winding 87b of the current transformer 87 is turned on so that the transistor 75 is turned on and the transistor 74 is turned off.
A voltage is generated at 87c, the transistor 75 is kept on, and the transistors 75, 7
No. 4 alternately turns on and off. When the transistor 75 is on, a current limited by the inductance element 9 flows from the AC power supply 1 through the inductance element 9,
This current increases with time. Further, this current and the current flowing from the smoothing capacitor 71 via the resonance system simultaneously flow into the transistor 75, and this current increases with time. Next, when the transistor 75 is turned off, the inductance element 9 is turned on immediately before the turn-off.
Is discharged to the smoothing capacitor 71 via the diode 72. At the same time, when the transistor 75 is turned off, the transistor 74 is turned on, the resonance system continues to oscillate, and continues to supply voltage and energy to the discharge lamp 78. When the transistor 74 is turned off and the transistor 75 is turned on by the vibration of the resonance system, the above operation is repeated thereafter, and the discharge lamp 78 is kept on.

In this operation, when the instantaneous value of the AC power supply 1 is low, the rate of increase of the current flowing through the inductance element 9 is low.
, The energy stored in the inductance element 9 at the time of turn-off is small, and the charging voltage of the smoothing capacitor 71 also decreases. At this time, the input current also decreases according to the instantaneous value of the AC power supply 1. When the instantaneous value of the AC power supply 1 is high, an operation opposite to that when the instantaneous value is low is performed. That is, if the rate of increase of the current flowing through the inductance element 9 is high and the on-time is always the same, the energy stored in the inductance element 9 when the transistor 75 is turned off is large, and the charging voltage of the smoothing capacitor 71 increases. The input current also increases according to the instantaneous value of the AC power supply 1. Therefore, an input current having a substantially similar shape to the waveform of the AC power supply 1 can be obtained, the power input power factor can be increased, and harmonic components of the power supply input current can be reduced.

Next, the operation of the discharge lamp lighting device according to the embodiment when the transistor 74 does not operate due to a component failure or a solder failure will be described.

When a full-wave rectified DC pulsating voltage is applied from the AC power supply 1 through the rectifier circuit 3 and the noise filter 2, the smoothing capacitor 71 is charged via the diode 10. At the same time, when the capacitor 84 is charged via the resistor 81 and its voltage reaches the breakdown voltage of the trigger element 83, the charge of the capacitor 84 is
5, and the transistor 75 is turned on. When the transistor 75 is turned on, a current flows from the smoothing capacitor 71 while increasing through the capacitor 76, the capacitor 79, the inductance element 77, and the current transformer 87. However, even when the transistor 74 does not operate due to a defective solder of the transistor 74, the resistor 86, the current transformer 87, etc., the resonance system including the transformer 77 and the capacitor 76 of the inverter circuit 7 does not operate.
And a transistor 75, an output is generated in the secondary winding 87c of the current transformer, and the base current of the transistor 75 is continuously supplied. As a result, since the transistor 75 is turned on, the power supply from the AC power supply 1 is continued, and the energy stored in the inductance element 9 immediately before the transistor 75 is turned off is charged to the smoothing capacitor 71 via the diode 72. At this time, the transformer 77 of the inverter circuit 7
Although the resonance system including the capacitor 76 and the capacitor 76 resonates, the voltage of the capacitor 79 does not increase and the arc tube 78 does not start discharging because of the high frequency. For this reason, even though the energy is charged in the smoothing capacitor 71, the energy is not consumed by the arc tube 78, so that the voltage of the smoothing capacitor 71 abnormally increases. An electrolytic capacitor generally used as the smoothing capacitor 71 is:
When a voltage more than a predetermined time (usually 1.1 to 1.5 times) of the rated voltage is applied, a leakage current flows and raises the temperature of the electrolyte,
The electrolyte is vaporized, leading to rupture.

Therefore, the discharge lamp lighting device according to the embodiment exceeds the voltage applied to the diode 10 at the time of normal lighting, and when the voltage of the smoothing capacitor 71 becomes about 1.3 times the rated voltage that does not cause explosion in a short time. By connecting the diode 10 that breaks down, the smoothing capacitor 7
When an abnormal voltage is applied to 1, a current flows in the diode 10 in the reverse direction to protect the smoothing capacitor 71. Further, the abnormal operation is prevented from continuing by using the characteristic of breaking in the short circuit mode when a large reverse current flows through the diode 9, and the operation at that time will be described next.

FIG. 2 shows an equivalent circuit when the diode 10 is short-circuited. The smoothing capacitor 71 at this time
Is shown by curve A in FIG. 3, and the voltage waveform of the power supply voltage is shown by curve B in FIG. Since the voltage of the smoothing capacitor 71 does not rise above the rectified voltage of the AC power supply 1,
The smoothing capacitor 71 can be protected. When the transistor 75 is turned on, the inductance element 9 from the smoothing capacitor 71, the capacitors 76 and 79
And a current flows through both the series circuit composed of Even in this state, since the resonance is maintained by the capacitor 76 and the inductance element 77, a current for periodically turning on and off the transistor 75 is supplied from the current transformer. The energy stored in the inductance element 9 at the moment when the transistor 75 is turned off is discharged through the diode 72 in the closed circuit of the inductance element 9 and the diode 72. Further thereafter, since the energy of the resonance system stored in the capacitor 76 and the inductance 77 is discharged through the inductance element 9, a large DC current always flows through the inductance element 9 regardless of whether the transistor is on or off. The inductance element 9 selected so as to limit only the current during normal lighting easily saturates. If the transistor 75 is turned on in this state, a larger current flows from the AC power supply 1 because the current limiting capability of the inductance element 9 is reduced, and the transistor 75 is in a state of extremely generating heat. Transistors are destroyed in short-circuit mode if they generate excessive heat.
As a result, only the inductance element 9 is connected to both ends of the smoothing capacitor, and a large current flows to blow the fuse, so that the lighting circuit can be safely and permanently stopped.

At the time of normal lighting, the diode 10 is not involved in the lighting of the arc tube, so that it is not necessary to use a high-speed diode. Therefore, since it is lower than the smoothing capacitor 71, it is not necessary to select a device having a high breakdown voltage, and an inexpensive element can be used. Further, the smoothing capacitor can be rapidly charged directly without the intervention of the inductance element 9 immediately after the power is turned on, so that the inverter 7 can start oscillating quickly and reliably at the time of starting the circuit, so that the starting performance and the starting performance of the lamp can be improved.

In the above embodiment, the diode 10 having the breakdown characteristic is used as the semiconductor switch.
Those having zener characteristics may be used. In this case, the operation after the short-circuiting is as described above, only slightly increasing the time from the flow of the current in the reverse direction to the short-circuiting in the abnormal state. Further, those having avalanche characteristics can be similarly used.

[0022]

As described above, the discharge lamp lighting device of the present invention is small, inexpensive, simple, and has a high power input power factor, and discharges in a state where the harmonic components of the power input current are small. The lamp has an excellent effect that the lamp can be started and lit, and can be kept safe even in the event of a component failure.

[Brief description of the drawings]

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

FIG. 2 is an equivalent circuit diagram when the protection device is activated.

FIG. 3 is a voltage waveform diagram of a smoothing capacitor in one cycle of the AC power supply 1 when the protection device is activated.

FIG. 4 is a circuit diagram of a conventional discharge lamp lighting device.

[Explanation of symbols]

 3 Rectifier circuit 4 Chopper circuit 5, 7 Inverter circuit 9, 77 Inductance element 41, 71 Smoothing capacitor 50, 51, 74, 75 Transistor 54 Transformer 76 Resonant capacitor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05B 41/282 H02M 7/48 H05B 41/24

Claims (1)

(57) [Claims] 1. A closed circuit including a discharge lamp, a resonance capacitor, a first inductance element, and a first switch element, a smoothing capacitor having one end connected to one end of the first switch element, and the first switch element. A second switch element connected between the other end of the smoothing capacitor and the other end of the smoothing capacitor; a connection point between the first switch element and the second switch element; Rectifying means connected between a connection point with one end of the switch element, a connection point between the smoothing capacitor and the second switch element, and a connection between the first switch element and the second switch element A rectifier circuit connected to an AC power supply to be connected via a second inductance element, and a connection point between the second inductance element and the rectifier circuit, A discharge lamp lighting device comprising a semiconductor switch connected between a smoothing capacitor and a connection point of one end of the first switch element and having a predetermined breakdown characteristic.