JP3085023B2 - 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, and more particularly to a bulb-type discharge lamp in which the lighting device is integrated with a discharge lamp.

[0002]

2. Description of the Related Art Conventional lighting devices for discharge lamps include:
The one shown in FIG. 4 is known (JP-A-63-1).
93495).

In FIG. 4, a smoothing capacitor 3 is connected to a rectifier 2 connected to a commercial power source 1 and a capacitor 15 is connected to the rectifier 2.
A switching transistor 9 is connected in series with a parallel body of the oscillation transformer 4 and the primary winding 4A. The current limiting inductance element 6 and the pair of electrodes 5A, 5B
Are connected in series, and a starting circuit composed of a series body of a diode element 7 and a bidirectional semiconductor control element 8 is connected between both electrodes. One end of the secondary winding 4B of the oscillation transformer 4 is connected to the base of the transistor 9 via the base current limiting capacitor 10 and the inductance element 11, and the other end is connected to the negative terminal of the smoothing capacitor. Further, a resistor 14 is connected in series with a resistor 12 as a reset circuit for the base current limiting capacitor 10 and a diode 13 as a starting resistor of the transistor 9.

Next, the circuit operation of the above-described conventional discharge lamp lighting device will be described. When the commercial power supply 1 is turned on, the AC voltage is rectified and smoothed by the rectifier 2 and the smoothing capacitor 3, and the transistor 9 is turned on via the resistor 14. At this time, the collector current is the positive electrode of the smoothing capacitor 3 → the primary winding 4A of the oscillation transformer 4 → the collector of the transistor 9 → the emitter of the transistor 9 → the smoothing capacitor 3.
To the negative electrode. Then, a current flows from the secondary winding 4B of the oscillation transformer 4 to the base of the transistor 9 in the forward direction, and the transistor 9 is kept on. Next, when the collector current of the transistor 9 increases and becomes unsaturated, the electromotive force of the secondary winding 4B is inverted and the transistor 9 is turned off. Then, the charge that has been charged in the direction of making the base potential of the base current limiting capacitor 10 negative is discharged through the reset circuit, and when the base potential rises again, the transistor 9 is turned on. The above operation is repeated. As a result, a high-frequency voltage is generated in the primary winding 4A of the oscillating transformer 4, the bidirectional semiconductor control element 8 breaks over, and the preheating current is reduced to the smoothing capacitor 3 → the current limiting inductance element 6 → the electrode 5A of the fluorescent lamp 5. → Diode element 7 → Bidirectional semiconductor control element 8 → Fluorescent lamp 5
5B → the collector of the transistor 9. When the high frequency voltage of the oscillating transformer 4 is in a reverse cycle, the preheating current is blocked by the diode element 7 and the high frequency voltage is applied to the fluorescent lamp 5.
The fluorescent lamp 5 is started, and thereafter, the high-frequency current flows through the fluorescent lamp 5 to maintain lighting. When the transistor 9 is turned on, the base current is limited by the series body of the base current limiting capacitor 10 and the inductance element 11.

Next, when the temperature of the circuit becomes high or the commercial power supply voltage rises, the collector current increases and the voltage of the secondary winding 4B of the oscillation transformer 4 also rises. Since a resistor having a characteristic that decreases with an increase in temperature is used, the resistance component (= (1 / ωC) −ωL) of the resonance series circuit increases, so that the base current is reduced and the on-time of the transistor 9 is reduced.
As a result, the loss of the transistor 9 is reduced, and thermal runaway can be prevented.

[0006]

In recent years, it has been desired to reduce the size of a lighting circuit in order to reduce the size of an appliance. In addition, a compact fluorescent lamp in which a discharge lamp and a lighting circuit are integrated,
There is a need for smaller lighting circuits and for installing the lighting circuits in very high temperature environments. However, since the semiconductor switch element is used, if it is used near its temperature limit, there is a problem that the semiconductor switch element is easily thermally destroyed and the lighting circuit is destroyed depending on an increase in ambient temperature or a use condition. In order to prevent this, if a special element and a base circuit are provided as in a conventional discharge lamp lighting device,
There was a problem that the shape became large or expensive.

An object of the present invention is to provide a discharge lamp lighting device which has a small, simple and inexpensive configuration and can start and light a discharge lamp safely even in a high temperature environment.

[0008]

A discharge lamp lighting device according to the present invention comprises a closed circuit including a discharge lamp, an inductance element, a capacitor, and a semiconductor switch element, and starts the discharge lamp by turning on and off the semiconductor switch element. And a current transformer for driving the semiconductor switching element by a secondary winding output with a primary winding current as a discharge lamp current, and a saturation magnetic flux density of a core of the current transformer as Bms (mT). ,
When the temperature of the core is Tcore (° C.), and the temperature equal to or higher than the core temperature when the temperature reaches the thermal breakdown start temperature of the semiconductor switch element is Th (° C.), the saturation magnetic flux density Bms (mT) of the core is The core temperature Tcore (° C.) is as follows: Bms = −a · Tcore + b (where a> 0 (constant when Tcore ≦ Th), b =
Constant).

[0009]

The peak output voltage V _{CT2 (peak)} of the secondary winding of the current transformer of the lighting circuit is almost proportional to the saturation magnetic flux density Bms of the current transformer core, and V _{CT2 (peak)} is the same as the drive signal value of the semiconductor switch element. It is almost proportional to the ON time of the semiconductor switching element, and the drive signal peak value of the semiconductor switching element and the ON time of the semiconductor switching element are almost proportional to the power consumption of the lighting circuit and the current of the semiconductor switching element. The current of the switch element is approximately proportional to the heat generated by the semiconductor switch element and the operating temperature. Therefore, even if the operating temperature of the semiconductor switch element rises for some reason from the normal operating range, the rise in temperature raises the temperature Tcore of the current transformer core, and accordingly, the saturation magnetic flux density Bms of the core decreases, and V _{CT2 (peak)} decreases, the drive current peak value of the semiconductor switch element and the ON time of the semiconductor switch element decrease, and the power consumption of the lighting circuit and the current of the semiconductor switch element decrease. Therefore, the heat generation of the semiconductor switch element and the rise in the operating temperature are suppressed. further,
In the present invention, the core saturation magnetic flux density Bms and the core temperature Tco
As described above, since the relationship with re is constant up to a temperature Th that is equal to or higher than the current transformer core temperature when the thermal switching start temperature of the semiconductor switch element is reached, the normal operating temperature range of the semiconductor switch element is limited to the operating limit temperature. You will be able to climb to the vicinity.

[0010]

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 of the present invention includes a fluorescent lamp 25 as a discharge lamp, a capacitor 24, a choke coil 27, a primary winding of a current transformer 28, and a semiconductor switching element. A closed circuit including a collector and an emitter of the transistor 29; a transistor 30 which is a semiconductor switch element having a collector connected to the emitter of the transistor 29;
9 and 30, a smoothing capacitor 3 connected in parallel to the smoothing capacitor 3, a rectifier circuit 2 for rectifying an AC power supply 1 having an output terminal connected to the smoothing capacitor 3, and a resistor 3 connected in parallel to the smoothing capacitor 3.
1 and a capacitor 32, a trigger element 33 connected between the midpoint of the series circuit and the base of the transistor 30, and a capacitor 26 connected to the other end of the fluorescent lamp 25. One of the secondary windings of the current transformer 28 is connected to a transistor 29 via a resistor 34.
And the other one of the secondary windings is connected through a resistor 35 between the base and the emitter of the transistor 30. Such a lighting circuit is a bulb-type fluorescent lamp 36 integrated with the fluorescent lamp 25.

FIG. 2A shows the temperature characteristics of the core of the current transformer 28, and FIG.
5 shows the temperature characteristics of the secondary winding output voltage V _CT2 . The relationship between the saturation magnetic flux density Bms and the core temperature Tcore of the core of the current transformer 28 is shown by a curve A in FIG. This curve A is represented by the following equation.

Bms = −a · Tcore + b (1) (where a> 0 (constant when Tcore ≦ Th), b =
(Th is a temperature equal to or higher than the core temperature of the current transformer 28 when the thermal breakdown starting temperature 160 to 175 ° C. when the bipolar transistors 29 and 30 are operated is about 185)
A) is a constant depending on the core material itself,
Use a ferrite core of 1-2. Above Th, a becomes smaller as a general property of the core. Also, in FIGS. 2A and 2B, the curve A
Shows the characteristics of the core of the present invention, and curve B shows the characteristics of the conventional core. Temperature T ₃ normal operating temperature at the time of rated lighting, T ₁ is the operating temperature of the bad times of use conditions such as a power supply voltage and ambient temperature,
Bms ₃ is the effective saturation magnetic flux density of the core at the core temperature T ₃ ,
ms ₂ is the effective saturation magnetic flux density when the core temperature T ₁ of, effective saturation magnetic flux density when the BMS ₁ is a core temperature T ₁ of the conventional core, V
_CT23 secondary winding output voltage peak value of the current transformer 28 when the T _3, V _CT22 secondary winding output voltage peak value at T _1, V _CT21 is 2 when the T ₁ of the conventional core This is the peak output voltage of the next winding. In addition, 1 of the current transformer 28
The number of secondary windings and the number of secondary windings are set so that transistors 29 and 30 perform a saturation operation until the current transformer 28 saturates on the base circuit formed by the resistors 34 and 35, and the input power, oscillation frequency and starting voltage are changed. Set to be appropriate.

Next, the operation of such a discharge lamp lighting device will be described. Before the fluorescent lamp 25 is started, the AC voltage is rectified from the AC power supply 1 via the rectifier circuit 2 to charge the smoothing capacitor 3, and at the same time, the capacitor 32 is charged via the resistor 31.
, The charge of the capacitor 32 is supplied to the base of the transistor 30, and the transistor 30 is turned on. When the transistor 30 is turned on, current flows from the AC power supply 1 to the capacitor 24, the preheating electrode of the fluorescent lamp 25, the capacitor 26, the choke coil 27, the current transformer 28, and the transistor 30 via the rectifier circuit 2 while increasing. Next, the current transformer 28
The current flowing through the primary winding of the current transformer 28
When the core is magnetically saturated, the output of the secondary winding disappears,
Since the base current supplied to the transistor 30 cannot be supplied, the transistor 30 is turned off. At the same time, the current due to the energy stored in the choke coil 27 flowing to the capacitor 24 via the current transformer 28 and the transistor 29 is a current that decreases with time, so that the output polarity of the secondary winding is inverted, and the transistor 29 is turned on and the transistor 30 is turned off. This current resonates in the choke coil 27 and the capacitors 24 and 26, and when this current is reversed and the core of the current transformer 28 is magnetically saturated, the output of the secondary winding disappears and is supplied to the transistor 29. Since the base current cannot be supplied, the transistor 29 is turned off, and then the transistor 30 is turned on again.
Thereafter, this operation is repeated.

The above current flows through the preheating electrode of the fluorescent lamp 25 to heat the electrode. At the same time, a large voltage is applied to the fluorescent lamp 25 due to resonance, and the fluorescent lamp 25 is turned on when the electrode temperature increases.

Next, the circuit operation when the fluorescent lamp 25 is on will be described. When the transistor 30 is turned on,
At this time, from the smoothing capacitor 3 and the rectifier circuit 2, the capacitor 24, the preheating electrode of the fluorescent lamp 25, the capacitor 26, the preheating electrode of the fluorescent lamp 25, the choke coil 27, the primary winding of the current transformer 28, and the transistor 30. Electric current flows. This current forms a resonance current between the capacitor 24 and the choke coil 27. The capacitor 24 is charged by this current, and a voltage V _CT2 is generated in the secondary winding of the current transformer 28, and the resistance 3
5, the base current of the transistor 30 (Ib = (V
_CT2 -Vbe) / R ₃₅₎ (provided that, R ₃₅ is the resistance value of the resistor 35) is turned on keeping transistor 30 flows. Also,
At the same time, the output of the secondary winding is applied in the reverse direction between the base and the emitter of the transistor 29 to keep the transistor 29 off. Here, V _CT2 changes in proportion to the resonance state, and is a voltage that is reduced by the magnetic flux of the core due to the secondary winding output current from the divided voltage with the inductance of the choke coil 27, and increases with time. . A voltage V _CT23 corresponding to a predetermined effective saturation density Bms ₃ at the temperature T ₃
When the current transformer 2
8 is magnetic saturation, the output voltage of the secondary winding becomes zero,
The transistor 30 is turned off at a predetermined ON time.

Next, when the magnetic saturation of the current transformer 28 is eliminated, the transistor 29 is turned on by the choke coil 27 and the current which continues to decrease while flowing from the base / emitter of the transistor 29 to the collector. 30 remains off. This current is supplied to the choke coil 27 and the capacitor 24,
When this current is reversed and the core of the current transformer 28 is magnetically saturated again, the output of the secondary winding is lost and the base current supplied to the transistor 29 cannot be supplied, so that the transistor 29 is turned off. Then, the transistor 30 is turned on again. Thereafter, this operation is repeated. At this time, the input power Ws is mainly determined by the ON period of the transistor 30. Immediately after the start, the temperature of the lighting device is generally low, and the temperature of each part rises due to heat generated by the fluorescent lamp 25 and other components, and eventually equilibrates at the set temperature at the rated lighting. At this time, the input power is as shown in a temperature characteristic diagram of the input power in FIG. 3 (a), a predetermined input power Ws _3. At this time, the current transformer 2
Core temperature Tcore of 8 to equilibrium at a temperature T ₃ is heated by the transistors 29 and 30 and other components.

By the above operation, the discharge of the fluorescent lamp 25 can be maintained. By repeating such an operation, the fluorescent lamp 25 can be kept on at a constant level.

Next, when the operating point moves due to power supply voltage fluctuations or deterioration of the lighting environment and the temperature of the entire lighting device rises, the core temperature Tcore of the current transformer 28 also rises,
As shown by a curve A in FIG. 2A, the effective saturation density Bms decreases. Therefore, as shown by a curve A in FIG. 2B, the secondary winding voltage peak value V _{CT2 (pe
ak)} also decreases. Along with this, the ON period of the transistor 30 decreases and the peak value of the collector current also decreases, and accordingly the oscillation frequency increases, the impedance of the resonance system increases, and the lamp current of the fluorescent lamp 25 decreases. Therefore, the input power Ws also decreases as shown by the curve A in FIG. As a result, the heat generation amount of the entire lighting device is reduced, and the temperature of the transistors 29 and 30 can be reduced at the rate of increase in temperature as shown by the curve A in FIG.

In the present embodiment, the relationship between the saturation magnetic flux density Bms and the core temperature Tcore is expressed by the above equation (1) for the core of the current transformer 28. At the core temperature T ₁ , the input power and the collector current can be sufficiently reduced with respect to a temperature rise by the turns ratio of the current transformer and the values of the resistors 34 and 35. Can be set to be equal to or lower than the thermal runaway start temperature.

The thermal runaway onset temperature of the transistors 29 and 30 generally fluctuates due to the operating state and structural variation of the transistors. The thermal runaway occurs at a lower temperature as the transistor loss increases and the turn-off current increases. In the case of a silicon bipolar transistor, the temperature varies from 150 to 220C. FIG. 3B shows the temperature characteristics of the transistors 29 and 30. In the present embodiment, the collector current of the transistors 29 and 30 is configured to decrease as the temperature rises. Since the core characteristics are kept constant up to this point, the thermal runaway starting point can be set to a higher temperature side, and the transistor 2 can be turned off as shown by the curve A in FIG.
Even if the ambient temperature rises abnormally, the temperatures 9 and 30 can be set such that the thermal runaway does not occur unless the ambient temperature of the lighting device itself exceeds the thermal runaway start point.

In the discharge lamp lighting device according to the present embodiment, the current transformer 28 is used for driving the transistors 29 and 30, and the core material thereof has a simple, inexpensive and small-sized circuit configuration in which only those having predetermined conditions are used. Since the transistors 29 and 30 can be used in a higher temperature region, a smaller and safer lighting device and a compact fluorescent lamp 36 can be realized.

For example, in the circuit configuration shown in FIG. 1, the inductance of the choke coil 27 is 1.2 m.
H, the capacitor 24 is 0.068 μF, the capacitor 26
Is a constant of 15000 pF, the smoothing capacitor 3 is 47 μF, and the AC power supply voltage is 120 V. The 25W bulb-type fluorescent lamp used was manufactured and tested.
As shown by the curve A in FIG. 3 (a), the fluorescent lamp could be safely kept on, and good results were obtained.

The curve B in FIG. 3A is a temperature characteristic diagram of a 25 W light bulb-shaped fluorescent lamp using a current transformer of a core material having the conventional characteristics shown in the curve B in FIG. 2A. This did not satisfy the above equation (1), so that the transistor was thermally destroyed.

In the above embodiment, the bipolar transistors 29 and 30 are used as the semiconductor switch elements.
Etc. may be used. In this case, the secondary winding output current of the current transformer 28 hardly flows, and is controlled by the secondary winding output voltage, but the operation as the semiconductor switch element is the same. At this time, the FET is basically an element that does not run away from the heat, but thermal destruction occurs, and the same effect can be obtained by setting the same for this phenomenon. Further, in this embodiment, a series inverter is used as the lighting circuit, but the same effect can be obtained by using another single inverter.

In this embodiment, the fluorescent lamp and the lighting circuit are integrated to facilitate heating of the current transformer 28. However, even if the lighting circuit is separated from the lamp, if the lighting circuit itself is small, Similar effects can be obtained.

[0027]

As described above, the discharge lamp lighting device of the present invention can use the semiconductor switch element in a higher temperature region by driving the semiconductor switch element with the current transformer having a predetermined temperature characteristic, and can reduce the size and size of the device. With a low-cost and simple configuration, the discharge lamp can be started and lit safely.

[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. 2A shows a temperature characteristic diagram of a core of a current transformer 28. FIG. 2B shows a secondary winding output voltage V _{CT2 of the} current transformer 28.
Temperature characteristic diagram

FIG. 3 (a) Temperature characteristic diagram of input power (b) Temperature characteristic diagram of transistors 29 and 30

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

[Explanation of symbols]

 9, 29, 30 Transistor 24, 26 Capacitor 25 Discharge lamp 27 Choke coil 28 Current transformer

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-86394 (JP, A) JP-A-2-216796 (JP, A) JP-A-61-221581 (JP, A) JP-A-63-86 86395 (JP, A) JP-A-63-193495 (JP, A) JP-A-63-218197 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 41/24 H05B 41 / 02

Claims (1)

(57) [Claims] 1. A discharge lamp lighting device in which a discharge lamp, an inductance element, a capacitor, and a semiconductor switch element constitute a closed circuit, and the discharge lamp lighting device starts the discharge lamp by turning on and off the semiconductor switch element. A current transformer for driving the semiconductor switching element by a secondary winding output as a discharge lamp current, wherein a saturation magnetic flux density of a core of the current transformer is represented by Bms (mT).
When the temperature of the core is Tcore (° C.), and the temperature equal to or higher than the core temperature when the temperature reaches the thermal destruction start temperature of the semiconductor switching element is Th (° C.), the saturation magnetic flux density Bms (mT ) And the core temperature Tcore (° C.), Bms = −a · Tcore + b (where a> 0 (constant when Tcore ≦ Th), b =
A discharge lamp lighting device satisfying the following relationship: