JPS6326909A - Overcurrent limiting circuit for dc lamp bulb - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention is applicable to excessive currents such as inrush current and arc discharge current in DC lighting bulbs. Regarding limiting circuits, when using conventional circuits, ζ can limit the total inrush current that occurs when starting a light bulb, but cannot limit the excessive current caused by arc discharge when the filament breaks. .

This arc discharge occurs due to a short circuit. For example, when a 60-watt light bulb is lit at 130 volts DC, an excessive current of up to 200 amperes continues to flow, causing a large amount of damage to circuit components such as rectifying means and switching means. May cause damage.

The present inventor has arrived at the present invention by intensively studying methods for efficiently limiting these arc discharge currents and inrush currents. A light bulb is connected to the output end of the rectifier circuit with current limiting means fully connected, and a switch means having a main current circuit that is conductive only when the light bulb filament is in a heated state is connected in parallel to the current limiting means. An overcurrent limiting circuit for a DC lighting bulb, characterized in that the inrush current at the time of starting the circuit is limited by the inductance and the current limiting means, and the arc discharge current in the event of filament breakage is limited by the inductance. This is a summary.

The present invention will be fully explained below with reference to illustrated embodiments.

FIG. 1 shows a complete example of an overcurrent limiting circuit for a DC lighting lamp according to the present invention.

In this embodiment, the input end of the bridge diode (4) is connected to the AC power supply (1) through the inductance (2), while the output of the bridge diode (4) is connected to the smoothing capacitor (6). The filament resistance of the bulb (7) is approximately 10 ohms at ambient temperature, and the DC current is 130 ohms. 13 when applying bolt gold
A starting current of amperes flows, causing the filament to break. So, 100 ohm resistor (8)? Connected in series to an unheated filament, its combined resistance 'k 1
00 + 10 = 1) If it is 0 ohm, even if the above-mentioned DC is applied, only a starting current of about 1.2 amperes will flow, which greatly reduces the possibility of wire breakage.

A switch means such as a thyristor having a main current conductive only when the filament of the light bulb (7) is in a heated state is connected in parallel to the resistor (8), and the switch means is connected in parallel to the resistor (8) for a predetermined period of time after the power is turned on. After some time passes and the filament transitions to a heated state, the resistor (8) is completely short-circuited and the light bulb (7) is heated.
) is supplied with the full output of the rectifier circuit. In this embodiment, another thyristor 00 is connected in cascade to the thyristor Z (9) to constitute the entire switch means, and the gate of the thyristor α value is made up of a resistor α2 and a capacitor side via a resistor α3. A time constant circuit is connected. By using two thyristors connected in series in this manner, the thyristor (9) can be made conductive with a small current, which is extremely convenient for stabilizing the circuit. Resistance α2 is resistance a
S? Since it is connected in parallel to the limiting resistor (8) through
At the same time as the AC power source (1) is turned on, the voltage generated across the resistor (8) charges the capacitor zero times via the resistor α2. In this embodiment, the voltage drop across the resistor (8) as the current limiting means is used as a power source for driving all the switch means, so a separate power source is required. There is no need to provide one, which is extremely convenient for simplifying and stabilizing the circuit. The capacitor 0 is connected to the resistor (I3f) according to the time constant with the resistor az.
It is discharged to the gate of the thyristor (II) through fi, and the thyristor αli becomes conductive.The voltage generated across the resistor αη simultaneously with the conduction of the thyristor α causes the thyristor (9) to be fully conductive and the resistor (8) to be fully short-circuited. The full voltage of the rectifier circuit will be applied to the light bulb (7).Therefore, by setting the time constant to such an extent that all the filaments of the light bulb (7) can shift to a heated state, the voltage generated when the power is turned on can be reduced. Inrush current can be effectively limited.

In addition, the voltage regulator diode (5) and capacitor (3) connected in parallel to the input terminal of the bridge diode (4) are as follows.
These are used to absorb pulse voltage generated on the alternating current side of the diode, and these are used singly or in combination.

Now, what about the smoothing capacitor (6)? A large inrush current flows into the rectifier circuit having the power supply at the same time as the power is turned on. Although it depends on the capacitance of the smoothing capacitor (6), assuming that the capacitance is sufficiently large, if the power is turned on at the timing when the voltage of the AC power supply (1) reaches its maximum positive value, the inrush current that flows will be equal to that voltage. is divided by the internal resistance of the diode (4) to obtain the value. FIG. 2 shows the moment t when the voltage is at its maximum positive value. When the AC power supply (1) is fully turned on, the capacitor (6
) shows the full state of the inrush current flowing through the circuit. °In the present invention,
In order to limit this inrush current as well as the roaring discharge current when the filament is broken, an inductance (2) is connected in series to the input terminal of the bridge diode (4).

Generally, a large capacity electrolytic capacitor is a smoothing capacitor (6
), the inrush current can reach tens to hundreds of amperes when inductance (2) is not inserted. Now, if we use an inductance (2) t- of 6 millihenry as follows, the inductance shows only 2.26 ohm impedance for AC ω Hertz, but when the AC power supply voltage is positive Since it is at the maximum value of inductance (2)
Is the waveform of the current flowing through harmonics? Assuming that the harmonics have a total frequency of 250 Hz, the impedance of the inductance (2) for the harmonics will be 9.4 ohms, which is shown as a solid line in Figure 2. The inrush current at startup is 140 volts divided by 9.4.
This means that it can be suppressed to about 15 amperes. This current value agrees well with the actually measured value.

Incidentally, even if a 2 ohm constant resistor is used in place of the inductance (2), the starting current will only be reduced to 104 volts ÷ 2 ohms = 70 amperes, as shown by the broken line in Figure 2. It is.

Now, if the light bulb (7) were to break during direct current lighting, an arc discharge current of up to 200 amperes would continuously flow inside the light bulb (7), causing great damage to the rectifying means and switching means. There is. According to the present invention, if the inductance (2) of 6 millihenry is used, the electric current flowing through the bridge diode (4) = 100 volts ÷ 2.26 ohm = 44 amperes, which is approximately 1/4 to 1)5
This eliminates the need to use any rectifying means or switching means with a capacity greater than necessary.

As inductance (2), smoothing capacitor (6)
The present invention applies even if it is an air-core type or has an iron core such as a wound iron core or a laminated iron core as long as it can be connected to the input end of a rectifier circuit having The inductance value is usually
Light bulb that can limit excessive current and is a load (7)
The DC voltage applied to the DC voltage is set within a range that does not drop more than necessary. In particular, the resonant circuit formed by the inductance (2) and the smoothing capacitor (6) is caused by the phase difference between the voltage component and the current component in an excessive current. In other words, to increase the active power of excessive current? It is convenient to set it to be small. Furthermore, by using a low DC resistance inductance (2), the heat generated by the inductance (2) itself is reduced, and excessive current caused by inrush current or arc discharge current can be effectively limited.

Thus, the present invention can not only effectively limit the total inrush current at power-on, but also maintain the arc when the filament breaks. With difficulty, the arc discharge current can be fully and automatically reduced and the destruction of the rectifying means and switching means can be effectively limited.

Even if the arc reoccurs, it will be extinguished by inductance, and the filament breakage interval will increase and the filament will not repeat blinking until it reaches the hole diameter.Also, even if the power switch is closed after the arc extinguishes, Since the wire has already been broken, the arc will not occur again.

Therefore, the overcurrent limiting circuit of the present invention can safely turn on a light bulb with direct current without worrying about overcurrent such as inrush current when the power is turned on or arc discharge current when the filament is disconnected, and the circuit used The practical benefit of significantly extending the lifespan of elements and light bulbs? It is something that you have.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of an inrush current limiting circuit for a DC lighting bulb according to the present invention. Figure 2 shows the inrush current that flows into the smoothing means when the AC power supply is turned on at the timing when its voltage reaches its maximum positive value. The waveform diagram shown.

Claims (7)

[Claims] (1) An inductance is connected to the input end of a rectifier circuit having a smoothing capacitor, a light bulb is connected to the output end of the rectifier circuit via a current limiting means, and the light bulb filament is in a heated state in the current limiting means. consisting of switch means connected in parallel, each having a main circuit that conducts only when
An overcurrent limiting circuit for a DC lighting lamp, characterized in that the inrush current at the time of starting the circuit is limited by the inductance and the current limiting means, and the arc discharge current at the time of filament breakage is limited by the inductance. (2) An overcurrent limiting circuit for a DC lighting lamp as set forth in claim (1), wherein the switch means is a thyristor. (3) An overcurrent limiting circuit for a DC lighting lamp as set forth in claim (1) or (2), wherein the switch means is constructed by cascading two or more thyristors. (4) Excessive current in a DC lighting bulb according to claim 1, 2, or 3, characterized in that a capacitor or a constant voltage diode is connected in parallel to the rectifier circuit. limit circuit. (5) Excessive DC lighting bulb according to claim (1), (2), (3) or (4), characterized in that the current limiting means is a resistor. Current limit circuit. (6) Claims (1), (2), and (3) characterized in that the inductance and smoothing capacitor are set so as to reduce the effective power of excessive current.
), (4) or (5). (7) Claims (1) and (2) characterized in that the inductance is an iron-core inductance.
Paragraph, Paragraph (3), Paragraph (4), Paragraph (5) or Paragraph (6)
Excessive current limiting circuit for DC flashing light bulbs as described in Section 1.