JPH0368617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an inrush current limit switch circuit, particularly,
The present invention relates to an inrush current limiting switch circuit for limiting inrush current when lighting a light bulb.

[Prior Art] It is said that the filament resistance for electric current when it is cold is usually about 1/10 of that when it is incandescent. 100W
Taking a light bulb as an example, the filament resistance when it is incandescent is about 100Ω, and when a voltage of 100V is applied, a current of about 1A flows. On the other hand, the filament resistance when cold is about 10Ω, and when a voltage of 100V is applied in this state, it is about 10A, which is about 10Ω of the rated value.
The inrush current, which is twice as large as that, will flow, significantly shortening the lighting life of the bulb.

In order to limit such inrush current, for example, in Japanese Patent Application Laid-Open No. 59-230298, an inrush current limiting resistor corresponding to the difference in resistance between the filament resistance when it is incandescent and the filament resistance when it is cold is connected in series with the light bulb. At the same time, the application of the rated voltage to the bulb is delayed for a certain period of time after the power is turned on by an inrush current limiting switch circuit, which is made by connecting a bidirectional conduction element whose conduction is controlled by a timing circuit to an inrush current limiting resistor. It is described that shortening of lighting life caused by inrush current can be prevented.

This kind of inrush current limit switch circuit is effective in limiting inrush current, but if a failure occurs in the timing circuit for some reason, the bidirectional conduction element will not conduct, so it will not work until a certain period of time has passed after the power is turned on. However, the inrush current limiting resistor is not bypassed. For example, if a 100Ω resistor is connected in series to prevent inrush current from a 100W light bulb, approximately 0.9A (= 100V/10Ω +
100Ω) current flows, and the power consumption of the resistor is approximately 81W.
(=0.9A ² × 100Ω). If this state continues for a long time, the inrush current limiting resistor will burn out or become disconnected.
The heat also causes significant damage to surrounding components.

[Problems to be Solved by the Invention] In view of the above circumstances, the inventors of the present invention have conducted intensive studies on means to eliminate such drawbacks of conventional inrush current limit switch circuits.

[Means for solving the problem] As a result, at least one pair of diodes connected in antiparallel to each other is inserted into the circuit including the light bulb, and one end of the diode pair is connected to the light bulb to prevent the temperature rise of the inrush current limiting resistor. By connecting the gate of the bidirectional conduction element through a negative resistance such as a thermistor that can detect the overheating of the inrush current limiting resistor, the negative resistance detects the overheating of the inrush current limiting resistor, turns on the bidirectional conduction element, and reduces the inrush current. It has been found that by bypassing the limiting resistor, it is possible to effectively prevent burnout or disconnection of the inrush current limiting resistor, as well as damage to surrounding components due to heat generation.

That is, the present invention includes an inrush current limiting resistor connected in series to the light bulb, a bidirectional conduction element having a main current path connected in parallel to the inrush current limiting resistor, and a timing circuit connected to the gate of the bidirectional conduction element. In an inrush current limiting switch circuit that limits the inrush current to a light bulb by controlling the conduction of a bidirectional conduction element by a timing circuit, at least one pair of diodes connected in antiparallel to each other is inserted in the electric circuit including the light bulb. At the same time, by connecting one end of the diode pair to the gate of the bidirectional conduction element via a negative resistor that can detect the temperature rise of the inrush current limiting resistor, overheating of the inrush current limiting resistor can be detected by connecting it to the gate of the bidirectional conduction element. The gist of the present invention is an inrush current limiting switch circuit, which is characterized in that the inrush current limiting switch circuit is configured such that the inrush current limiting resistor is bypassed by detecting the current and making the bidirectional conduction element conductive.

The present invention will be explained below with reference to Examples.

[Embodiment] Fig. 1 shows a circuit according to an embodiment of the present invention, in which an AC power source AC includes a power switch S, an inrush current limiting resistor _R1 , and four pairs of inrush current limiting resistors R1 and 4 pairs connected in antiparallel to each other. A light bulb L is connected through a diode group D _o consisting of a diode pair. The resistor _R1 is used to limit the rush current that flows into the light bulb L when the power switch S is turned on.
For example, if the rated power of the light bulb L is 100W, the resistance difference between the filament resistance when it is incandescent and the filament resistance when it is cold is set to be approximately equal to or slightly higher than that. Since the filament resistances are about 100Ω and about 10Ω, respectively,
The inrush current limiting resistor _R1 should be set to approximately 100Ω.

A diode D ₁ is connected between both ends EF of the diode group D _o.
A time constant circuit consisting of a resistor R ₂ and a capacitor C is connected through a light emitting diode D ₂ connected to both ends of the capacitor C.
and is connected to the gate G of the bidirectional conduction element BCR via a photocoupler consisting of a photosensitive resistor CDS such as a CdS cell. This time constant circuit and photocoupler constitute a timing circuit. Th is a negative resistance such as a thermistor, and is an inrush current limiting resistance.
It is formed integrally with R ₁ or is attached closely to inrush current limiting resistor R ₁ , and is electrically a bidirectional conducting element.
It is connected to the gate G of BCR and the F terminal of the diode D _o .

To explain the operation of this example, when the power switch S is turned on, an alternating current voltage from an alternating current power source AC is applied to both ends of an electric path consisting of an inrush current limiting resistor R ₁ , a group of diodes D _o and a light bulb L. Light bulb L
If the rating of the bulb is 100W, the filament resistance when cold is about 10Ω, and if there is no inrush current limiting resistor _R1 , an inrush current of about 10A (= 100V/10A), which is about 10 times the rating, will flow, and the light bulb will This will significantly shorten the lighting life of the L. However, in this example, the inrush current limiting resistor _R1 is connected in series with the light bulb L, so the total load resistance when the power is turned on is approximately 110Ω (=10Ω + 100Ω), and an AC voltage of 100V is applied. Even if it is about 0.9A (=
Only a current of 100V/110Ω) flows. Therefore, there is virtually no inrush current when the bulb is turned on, and shortening of the lighting life of the bulb L due to the inrush current can be effectively prevented.

At the same time as the power switch S is turned on, the diode group
A voltage drop of about 0.7V occurs for each diode pair in D _o , resulting in a voltage drop of about 2.8V for the entire diode group D _o . This voltage drop does not depend on the current flowing through the diode pair, so it is a bidirectional conducting element.
Suitable as a gate trigger power supply for BCR.
The voltage drop across the diode group D _o is
It is rectified by D ₁ and charges the capacitor C via resistor R ₂ . The resistor _R1 and the capacitor C constitute a time constant circuit, and the capacitor C shows a charging curve as shown in FIG. Since the light emitting diode _D2 in the photocoupler is connected in parallel to the capacitor C, the voltage across it increases according to the time constant of the resistor _R2 and the capacitor C. Along with this, the amount of light from the light emitting diode _D2 also increases, so the resistance of the photosensitive resistor CDS in the photocoupler becomes the third
As shown in the figure, it decreases from several kΩ to several Ω.
The voltage at the F end of the diode group D _o is applied to the gate G of the bidirectional conduction element BCR, making the bidirectional conduction element BCR conductive. Thus, the inrush current limiting resistor _R1 is bypassed, and substantially the entire voltage from the alternating current power supply AC is applied to the light bulb L.
At this point, the filament of the light bulb L has been sufficiently preheated and has reached a resistance value close to that of incandescence, and no inrush current will occur even if the rated voltage is applied in this way. Figure 4 shows the voltage of the main circuit PK in the bidirectional conduction element BCR over time.
For about 0.15 seconds after the power is turned on, based on the time constant of resistor _R2 and capacitor C, the filament resistance of light bulb L is low, so a relatively large current flows and the voltage drop is somewhat large, but after that it drops rapidly and becomes an internal drop. Only voltage is required.

By the way, due to some reason the timing circuit breaks down and the bidirectional conduction element BCR does not conduct even after a predetermined period of time has passed since the power was turned on, and the inrush current limiting resistor
If _R1 is not bypassed, a large current may continue to flow through the inrush current limiting resistor _R1 , causing burnout or disconnection, and furthermore, the heat may cause significant damage to surrounding components.

In this example, a diode group D _o consisting of four diode pairs connected in antiparallel to each other is inserted into the electric circuit including the light bulb L, and the diode group D _o
The F end of the inrush current limiting resistor R1 is connected to the gate of the bidirectional conduction element BCR via a negative resistor Th such as a thermistor, which can detect the temperature rise of the inrush current limiting resistor _R1 , so there is no need to worry about anything during use. For some reason, the timing circuit does not operate, and the inrush current limiting resistor _R1
starts to overheat, the resistance of the negative resistance Th decreases to several tens of Ω.
The voltage at the terminal of the diode group D _o F is applied to the gate of the bidirectional conduction element BCR, which makes the bidirectional conduction element BCR conductive and bypasses the inrush current limiting resistor _R1 , thereby limiting the inrush current based on overheating. resistance
Burnout or disconnection of _R1 can be prevented.

Furthermore, since the switch circuit in this example is a two-terminal circuit, the entire switch circuit can be housed in a lighting-related component such as a light bulb socket, plug, rosette, or small indoor switch, or as a detachable adapter. For example, it can be extremely advantageously used in general indoor and outdoor lighting devices such as desk lamps, table lamps, floor lamps, wall lights, ceiling lights, wall lights, pendants, gate lights, and light control devices.

[Effects of the Invention] Since the present invention is configured in this manner, even if the timing circuit does not operate for some reason, the inrush current limiting resistor will not burn out or be disconnected, or the surrounding components will be damaged due to heat generation. Never.

Therefore, the inrush current limiting switch circuit of the present invention is extremely safe for use in general indoor and outdoor lighting devices and dimmer devices, and moreover, it is reliably bypassed when the inrush current limiting resistor starts to overheat. There is no need to use a resistor with a rating higher than necessary, and the switch circuit itself can be made extremely compact.

Furthermore, when the switch circuit of the present invention is made into a two-terminal circuit, it is extremely easy to accommodate it in existing lighting-related components or to make it into a detachable adapter.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention. Second
The figure shows the capacitor C in the embodiment shown in FIG.
This is the charging curve of FIG. 3 is a resistance change curve of the photosensitive resistor CDS shown in FIG. Figure 4 shows
2 shows a voltage waveform across the main circuit PK in the bidirectional conduction element BCR shown in FIG. 1. To explain the symbols in the diagram, BCR is a bidirectional conduction element, AC is an alternating current power supply, D is a diode,
R is a resistance, C is a capacitor, L is a light bulb, CDS is a photosensitive resistance, and Th is a negative resistance.

Claims (1)

[Claims] 1. From an inrush current limiting resistor connected in series to the light bulb, a bidirectional conduction element having a main current path connected in parallel to the inrush current limiting resistor, and a timing circuit connected to the gate of the bidirectional conduction element. In an inrush current limiting switch circuit that limits the inrush current to a light bulb by controlling the conduction of a bidirectional conduction element by a timing circuit, at least one pair of diodes connected in antiparallel to each other is installed in the electric circuit including the light bulb. At the same time, by connecting one end of the diode pair to the gate of the bidirectional conduction element via a negative resistor that can detect the temperature rise of the inrush current limiting resistor, overheating of the inrush current limiting resistor can be detected as a negative resistor. An inrush current limiting switch circuit characterized in that a resistor detects and conducts a bidirectional conduction element to bypass an inrush current limiting resistor. 2. The inrush current limiting switch circuit according to claim 1, wherein the timing circuit comprises a time constant circuit connected to a diode pair and a photocoupler connected to a gate of a bidirectional conduction element. 3. The inrush current limiting switch circuit according to claim 1 or 2, wherein the bidirectional conduction element is a bidirectional conduction three-terminal thyristor. 4. The inrush current limit switch circuit according to claim 1, 2, or 3, wherein the negative resistance is a thermistor. 5 Claims 1 and 2, characterized in that the inrush current limit switch circuit is a two-terminal circuit.
The inrush current limit switch circuit according to item 1, 3 or 4.