JPH02162700A - Power supply device - Google Patents

Abstract

PURPOSE:To obtain a power supply device with high safety by providing a temperature fuse, which thermally connects to a switching element and stops operation of an oscillation circuit by fusing. CONSTITUTION:DC power supply is supplied to an inverter circuit 7, while a both directional switch 25 becomes conductive with charging voltage of the capacity 24, and FET 8 and 9 mutually perform a switching action. At the life end of a fluorescent lamp 15 or at the time of the lighting circuit operation abnormality, a big current flows especially to the FET 8 and 9, while large heat is emitted to radiation plates 8a and 9a to fuse a temperature fuse 11 in a short time. At this time, even when a warm-up rate of the FET 9 is bad, large heat is surely given from the FET 8 so as to fuse the fuse 11 in a short time so that the operation of the inverter circuit 7 stops and a lamp 15 is extinguished.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides an oscillation circuit having a plurality of switching elements such as an inverter circuit, and supplies power to a load by the switching operation of each of the switching elements. The present invention relates to a power supply device that performs.

(Prior Art) Conventionally, as this type of power supply device, for example, a discharge lamp lighting device using an inverter circuit is known. In a discharge lamp lighting device, when the load discharge lamp reaches the end of its life or the inverter circuit malfunctions, the circuit elements that make up the inverter circuit generate abnormal heat, and in some cases, the circuit elements emit smoke. Therefore, conventionally, a current fuse is provided in the power supply input section, and the current fuse is blown by an increase in the input current in the event of an abnormality.

(Problem 8 to be solved by the invention) However, when using a current fuse, depending on the operating mode of the circuit, it may take a long time for overcurrent to flow after an abnormality occurs. There is a risk that the temperature of the circuit element will become abnormally high before the fuse is fused, causing the circuit element to emit smoke, which is insufficient from a safety point of view.

Therefore, it is possible to provide a temperature fuse in the inverter circuit and thermally couple the temperature fuse to a switching element that generates a large amount of heat in the inverter circuit.
If a temperature fuse is thermally coupled to one of the switching elements in an inverter circuit that uses multiple switching elements, the temperature rise of each switching element will differ due to variations in the characteristics of the switching elements, and this will result in a poor temperature rise rate. When thermally coupled to a switching element, it takes time for the temperature fuse to blow out after an abnormal operation occurs, resulting in insufficient safety as in the case of a current fuse.

Therefore, in an oscillation circuit that supplies power to a load by switching a plurality of switching elements in the oscillation circuit, if the oscillation circuit performs abnormal operation regardless of variations in the characteristics of the switching elements, the temperature fuse will be generated within a short period of time. can be fused to stop the operation of the oscillation circuit,
The present invention aims to provide a power supply device that can improve safety.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an oscillation circuit having a plurality of switching elements, and operates the oscillation circuit by the switching operation of each switching element to supply power to a load. The supply device is provided with a temperature fuse that is thermally coupled to each switching element and stops the oscillation function of the oscillation circuit by blowing out the fuse.

(Function) In the present invention having such a configuration, when the oscillation circuit operates abnormally, each switching element generates abnormal heat, and the heat of each switching element is transmitted to the temperature fuse, respectively.

Therefore, the temperature fuse always receives heat from the switching element with the highest temperature rise among the switching elements, and is blown out in a short time. When the temperature fuse is blown, the operation of the oscillation circuit is stopped.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. In this embodiment, the present invention will be described in which the present invention is applied to a compact fluorescent lamp in which a fluorescent lamp and an electronic lighting circuit including an inverter circuit serving as an oscillation circuit are integrated into a compact casing.

Figure 1 is a diagram showing an electronic lighting circuit, in which a noise prevention capacitor 2, a surge absorption element 3, and an input terminal of an aftereffect rectifier circuit 4 are connected via a current fuse 1 between input terminals a and b of an AC power source. There is.

A smoothing capacitor 6 is connected between the output terminals of the rectifier circuit 4 via a resistor 5 to form a DC power supply circuit.

For example, a self-excited series inverter circuit 7 is connected as an oscillation circuit between the output end of the DC power supply circuit, that is, both ends of the smoothing capacitor 6.

The inverter circuit 7 is a two-stone inverter circuit equipped with two MOS FETs (field effect transistors) 8 and 9 as switching elements and a feedback transformer 10.
8 and 9 series circuits are connected in parallel via a temperature fuse 11.

That is, the temperature fuse 11 is connected between the drain of the MOS type FET 8 and the positive terminal of the smoothing capacitor 6.

The feedback transformer 10 includes a winding 10a through which a high-frequency output current flows and windings 10b and 10 for feeding back the current to the gates of the MOS FETs 8 and 9.
It is composed of c.

The winding 10a1, the inductance coil 12, the capacitor 13.
14 series circuits are connected.

The capacitor 13 is connected to a fluorescent lamp 1 which is a discharge lamp.
A series circuit consisting of one filament electrode 15a1 and a capacitor 16 and the other filament electrode 15b of No. 5 is connected in parallel. Note that the capacitor 14 has, for example, an SS
A series circuit including a constant voltage conducting element 17 such as S and the thermistor 18 is connected in parallel.

The inverter circuit 7 also includes the winding 10b and the resistor 1.
A drive circuit for the MOS type FET 8 is formed by connecting a constant voltage diode 20 in parallel to the series circuit with the winding 10c and the resistor 21, and a constant voltage diode 2 is connected in series with the winding 10c and the resistor 21.
A drive circuit for the MOS type FET 9 is provided by connecting two MOS FETs 9 in parallel.

The inverter circuit 7 further includes the smoothing capacitor 6.
A starting circuit consisting of a series circuit of a resistor 23 and a capacitor 24 connected in parallel, and a bidirectional switch 25 connected between the connection point of the resistor 23 and the capacitor 24 and the gate of the MOS type FET 9. is provided.

Note that a resistor 26 and a capacitor 2 are connected via the temperature fuse 11 between the drain and source of the MOS type FET 8.
7 are connected in parallel, and a diode 28 is connected between the connection point between the resistor 23 and the capacitor 24 and the connection point between the MOS FETs 8 and 9 with the polarity shown.

As shown in FIG. 2, each of the circuit components constituting the electronic lighting circuit includes a circuit board 33 mounted inside a light bulb-shaped casing 32 having a base 31 at one end and an open end at the other end.
It is arranged above the .

A fixing member 34 for suspending and fixing the U-shaped fluorescent lamp 15 is attached to the opening of the light bulb-shaped casing 32.

Among the circuit components arranged on the circuit board 33, the temperature fuse 11 is a MOS type FET8 as shown in FIG.
It is insulated and sandwiched between the heat sink 8a of the MO3 type FET 9 and the heat sink 9a of the MO3 type FET 9, and is thermally coupled to both the FETs 8 and 9.

In this case, MOS type FET 8.9 and temperature fuse 1
In order to improve the thermal connection with 1, the entire body may be covered with a heat shrink tube.

The inductance coil 12 is a coil 4 which is divided into two parts and wound around a coil bobbin 41 as shown in FIG.
2.43 are connected in parallel to the circuit board 33 as shown in FIG. 5(a). Incidentally, as shown in FIG. 5(b), the coils 42 and 43 may be connected to the circuit board 33 separately and connected in parallel on the circuit board 33.

Among the capacitors used in the inverter circuit 7, as for film capacitors, for example, two capacitors 51 and 52 are buried in the exterior resin 53, and the lead terminals of each capacitor 51 and 52 are connected as shown in FIG. It is inserted into a hole in the circuit board 33 and soldered. In this case, as shown in FIG. 7, the lead terminals of each capacitor may be bent and soldered directly to the circuit pattern on the circuit board 33. Also, the number of buried film capacitors is 3.
It may be more than one.

In this embodiment with such a configuration, when the power is turned on, DC power is supplied to the inverter circuit 7, and the resistor 2
A charging current flows to the capacitor 24 via the capacitor 3. Then, depending on the charging voltage of the capacitor 24, the bidirectional switch 2
5 becomes conductive, current flows to the gate of MO3 type FET9, and MO3 type FET9 performs a switching operation. Thereafter, the inverter circuit 7 alternately switches the MOS type FETs 8 and 9 to connect the filament electrode 15 of the fluorescent lamp 15.
A preheating current is passed through the filament electrodes 15a and 15b, and a high voltage is applied between the filament electrodes 15a and 15b to start and light the fluorescent lamp 15.

When the fluorescent lamp 15 is lit normally and there is no abnormality in the lighting circuit, the lamp current is well within the rated range, so the lighting circuit does not generate a large amount of heat. Therefore, the heat trapped inside the casing 32 does not become large.

However, when the fluorescent lamp 15 reaches the end of its life or an abnormality occurs in the operation of the lighting circuit and the lamp current increases, the circuit components of the lighting circuit begin to generate abnormal heat. In particular, since a large lamp current flows through the MOS type FETs 8 and 9, the heat generated by them becomes extremely large.

Therefore, the heat sink 8a of the MOS type FET 8.9.

A large amount of heat will be released to 9a, and as a result, the temperature fuse 11 will be blown out in a short time. At this time, for example, even if the temperature rise rate of the MOS type FET 9 is low, the temperature fuse 11 will surely receive a large amount of heat from the MOS type FET 8, so that even in this case, it will surely be blown out within a short time. When the temperature fuse 11 is blown, the operation of the inverter circuit 7 is stopped and the fluorescent lamp 15 is turned off.

When the lighting circuit abnormally heats up like this, the MOS type F
Since the heat from the ETs 8 and 9 is directly received by the temperature fuse 11, the circuit operation can be stopped in a short time, and therefore the circuit components do not emit smoke, improving safety.

Further, the inductance coil 12 includes two coils 42.
Since it is composed of 43 parallel circuits, the wire diameter of each coil can be made thinner, similar to when a litz wire is used, and the loss at high frequencies can be reduced. However, there is no need to twist the wire as in the case of wire, and it is sufficient to simply wind the two coils 42 and 43 around the coil bobbin 41, so it can be easily produced using an automatic winding device.

Furthermore, when attaching the film capacitors used in the inverter circuit 7 to the circuit board, two film capacitors 51 and 52 are embedded in the exterior resin 53 and molded. 33 becomes easy, and the film capacitor can be stably fixed to the circuit board 33.

In the above embodiment, the MO8 type FETs 8 and 9 and the temperature fuse 11 were thermally coupled by sandwiching the temperature fuse 11 between the heat sinks 8a and 9a of each FET 8 and 9, but the present invention is not necessarily limited to this. For example, as shown in FIG. 8, a temperature fuse 11 may be sandwiched between the heat sink 8a of FET 8 and the surface of FET 9 opposite to the heat sink 9a, or as shown in FIG. Like FET8,9
A temperature fuse 1 is installed between the surfaces opposite to the heat sinks 8a and 9a.
1 may be sandwiched, and as shown in FIG.
A temperature fuse 11 may be sandwiched between the sides of the ET8.9. Furthermore, as shown in FIG. 11, a separate common heat sink 61 may be used, and each FET 8, 9 and temperature fuse 11 may be tightly fixed to this heat sink 61 to achieve thermal coupling. good.

In addition, in the above embodiment, the oscillation circuit is made of MO3O3.
Although we have described a series inverter circuit using two T-type transistors, the invention is not limited to this, the oscillation circuit is not limited to an inverter circuit, and the switching element used can also be a MOS. Of course, the present invention is not limited to type FETs, and furthermore, the number of switching elements used is not limited to two.

In addition, although the above-mentioned embodiment described the present invention applied to a light bulb-shaped fluorescent lamp in which a fluorescent lamp and an electronic lighting circuit including an inverter circuit, which is an oscillation circuit, are integrated into a light-bulb-shaped casing, the present invention is not necessarily limited to this. It can be applied to ordinary fluorescent lamp lighting devices, and can also be applied to devices that use discharge lamps other than fluorescent lamps as a load, and can also be applied to devices that use loads other than discharge lamps. It is something.

τ [Effects of the Invention] As detailed above, according to the present invention, in an oscillation circuit that supplies power to a load by switching a plurality of switching elements of an oscillation circuit, the oscillation circuit If the oscillator malfunctions, the temperature fuse can be blown out in a short time to stop the operation of the oscillation circuit, thereby providing a power supply device that can improve safety.

[Brief explanation of the drawing]

1 to 7 show one embodiment of the present invention, FIG. 1 is a circuit diagram, FIG. 2 is a partial sectional view showing the overall configuration, and FIG. A diagram showing the coupling state, FIG. 4 is a diagram showing the configuration of the inductance coil,
Figure 5 is a diagram showing an example of the circuit configuration of an inductance coil.
Figures 6 and 7 are diagrams showing examples of fixing a film capacitor to a circuit board, and Figures 8 to 11 are MOS type F
FIG. 7 is a diagram showing another example of thermal coupling between an ET and a temperature fuse. 7...Self-excited series inverter circuit (oscillation circuit)
, 8.9...MO8 type FET (switching element)
, 11... Temperature fuse, 15... Fluorescent lamp (load)

Claims (1)

[Claims] In a power supply device that includes an oscillation circuit having a plurality of switching elements, and operates the oscillation circuit by the switching operation of each of the switching elements to supply power to a load, the power supply apparatus is thermally coupled to each of the switching elements, and A power supply device comprising a thermal fuse that stops the oscillation function of the oscillation circuit by blowing the oscillation circuit.