JPS6225822A - Surge absorption circuit - Google Patents

Abstract

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

Description

[Detailed description of the invention] Industrial applications The present invention relates to a surge absorption circuit.

Conventional technology Generally, when an external surge such as a lightning surge or a ringing surge occurs in an electronic ballast, a high voltage is generated in the switching transistor of the electronic ballast and it is destroyed, so a surge absorption circuit is used. Is required. In particular, in factories and the like, it is commonly used as a 200V power distribution system for motors, etc., and ringing surges are likely to occur due to resonance in the power distribution system. Varistors are generally used to absorb such surges.

Here, TNR (product name), a typical varistor, has voltage-current characteristics as shown in Figure 9, and has a 1 m
The current A is regulated by the voltage at which it flows. In this figure, the 200V system is 270V.

The case of 1 mA TNR is shown. According to this TNR, 40
It can be seen that a current of about 30 A flows at about 0 V and surges can be absorbed. However, there are variations in TNR, and at 110% voltage (310V), the currents of O and IA are TN
This results in a loss of several percent.

Therefore, as shown in Fig. 10(a), a varistor (TNR)
) 1, the varistor 1 with a high operating voltage (varistor voltage) is used to reduce the loss during normal operation and to perform abnormal voltage tests during process inspection.
is used. In the case of such a varistor 1, the limiting voltage becomes high, so the surge protection characteristics deteriorate and the ringing surge absorption effect becomes low.

On the other hand, as shown in (b), there is also a circuit in which a surge absorbing capacitor 3 is connected between the output terminals of the full-wave rectifier circuit 2, and a resistor 4 is connected in parallel to this capacitor 3. However, in this method, the capacitor 3 is large in size because it uses a capacitor 3 having a capacity of about several hundred μF, and the loss of the resistor for discharging the surge energy is large, so that a loss always occurs.

In addition, as shown in the same figure (c), the resistor 5 and the varistor (TN
There is also one in which R)6 is connected in series. However, in the case of such a system, the loss during normal operation is large and the heat generation of both the resistor 5 and the varistor 6 is large, so components with high ratings must be used.

However, as shown in Japanese Patent Publication No. 58-20123, there is also a device in which a second metal oxide varistor 9 is connected in parallel to a series circuit of a first metal oxide varistor 7 and a gap 8 (see Fig. 11). reference).

As a result, when a relatively small surge voltage is applied, the surge voltage is limited only by the varistor 9, and when a large surge voltage is applied, the surge is suppressed by discharging in the gap part with the varistor 7 connected in parallel. It is about absorption.

The problem that the invention aims to solve However, even with the method shown in FIG.

This requires two varistors 7.9. Although control is performed based on the magnitude of the surge voltage, it is actually assumed that the surge voltage is quite high, such as 500 to 600V.

SUMMARY OF THE INVENTION The present invention has been devised in view of these points, and has an extremely simple and inexpensive structure that can reliably absorb ringing surges caused by resonance in the power distribution system, as well as reduce losses during normal operation. The purpose is to obtain a surge absorption circuit that can reduce heat generation.

Means for Solving the Problems In order to solve the above problems, the present invention provides a voltage that is not less than the peak value of the rated voltage and not more than twice the peak value in series with the ceramic varistor 12 connected to the power supply line. This configuration employs a configuration in which a switch element 13 (or 16) that is turned on is connected.

Since the switching element 13 (or 16) that turns on at a predetermined voltage is connected in series with the ceramic varistor 12, when a ringing surge occurs, this switching element 1
3 (or 16) is turned on, and the ceramic varistor 12 exhibits a surge absorption effect, but in normal conditions when no surge is applied, this switch element 13 (or 16) is not turned on, so the ceramic varistor 12 is not connected to the power supply. Therefore, no loss or heat generation occurs during normal operation.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 4. First, the aftereffect rectifier circuit 1 is connected to the AC power input terminal T.
1 is connected, and a ceramic varistor (TNR) 12 is connected between the output terminals of this full-wave rectifier circuit 11.

The ceramic varistor 12 used has the characteristics shown in FIG. 9, for example. A thyristor 13 as a switching element is connected in series to such a varistor 12. And this thyristor 13
A midpoint of a series circuit of a Zener diode 14 and a resistor 15, which are connected between the output terminals of the full-wave rectifier circuit 11 to detect voltage, is connected to the gate of the full-wave rectifier circuit 11.

Here, if the peak value of the rated voltage applied to the power supply input terminal T is VPP as shown in FIG. 2, the peak voltage when a ringing surge occurs is equal to the peak value VPP.
(2Vpp).

For example, in a 200V power distribution system, even if 110% voltage is considered, the maximum value VM^X of the ringing surge voltage due to the resonance of the power distribution system is 200x1.1x, /Wx2 = 622V.

In this embodiment, taking such points into consideration, the voltage at which the thyristor 13 is turned on, that is, the threshold level V
The TH is set to be greater than or equal to the peak value Vpp and less than or equal to 2VPP.

In such a configuration, as a specific example, the varistor 12 has TNR23G271, and the thyristor 13 has 5F3.
G41. IZ390 for Zener diode 14. resistance 15
4J4B41 is used for the full-wave rectifier circuit 11. Consider the case where a ringing surge as shown in FIG. 2 occurs. The peak value of the ringing surge voltage in this case is 560v.

If you zoom in on a part of such a ringing surge,
The result is as shown in FIG. 3(a). The threshold level VTH=420V of the thyristor 13 for such a ringing surge voltage is also shown. As a result, this voltage of 420 V is detected by the Zener diode 14 at timing t1 shown in FIG. 3(b), and the thyristor 13 is gate-triggered and turned on. When the thyristor 13 is turned on, the varistor 12 is connected to the power source, and exhibits a surge absorption effect as shown in FIG. 2(b). Here, at timing t2, the current of the varistor 12 becomes lower than the holding current of the thyristor 13, and the thyristor 13
Indicates when to turn off.

In this way, even if a ringing surge with a peak value of 560V occurs, it can be suppressed to 420V or less. At this time, the full wave rectifier circuit 11. Barista 12. The waveform of the current flowing through the circuit of the thyristor 13 is as shown in FIG. 3(c). Here, the period between t□ and t2 is 0.511 sec,
Between t2 and t□, Q is about 6m5ec.

Here, if we consider the normal state when no surge occurs, the thyristor 13 is not turned on and the varistor 12 is not connected to the power supply, so when the power supply is 110% and the power supply is normal, the O,
It does not cause the kind of loss that would occur if a current comparable to LA flows. As a result, it does not generate heat during normal operation. Even when a surge is applied (for example, 1
Even if a ringing surge voltage of 590V was applied continuously), the temperature rise of the varistor 12 was about 10''.Furthermore, when measuring the general ringing surge absorption characteristics according to this example, The characteristics shown in Figure 4 were obtained. That is, one surge absorption circuit using one varistor 12 was able to suppress the ringing surge of 420 to 960 V to approximately 420 V. .

Since such a simple configuration is sufficient, the cost is significantly reduced, and even if it is incorporated into the device, it does not take up space.

Note that the Zener voltage of the Zener diode 14 may be set lower than that shown in FIG. 3(b). FIG. 5 shows operating waveforms when a ZD-IZ330 is used as the Zener diode 14 and the Zener voltage is set low.

Further, as a switching element connected in series to the varistor 12, a triac (bidirectional thyristor) 16 may be used as shown in FIG. and.

Two Zener diodes 14a are placed on the gate side.

By using 14b, it can be used directly for an AC power source. In any case, by using the thyristor 13 or 16 in series with the varistor 12, the trigger circuit is simplified and a surge current of several tens of amperes can be handled with a small element.

By the way, examples of application of the surge absorption circuit according to this embodiment to specific equipment are shown in FIGS. 7 and 8.

First, FIG. 7 shows a case where the discharge lamp 17 is incorporated into an electronic ballast for lighting. That is, a surge absorption circuit is installed between the inverter lighting circuit 18 including switching transistors and the like and the gold wave rectifier circuit 11. According to this, the varistor conventionally used on the power supply side for absorbing lightning surges can be omitted, so the components that must pass through are the thyristor 13, Zener diode 14, . Only the resistor IS is required. FIG. 8 shows an example in which the surge absorption circuit shown in FIG. 6 is incorporated into a dimmer. Although this dimmer is shown very schematically, the light is dimmed by controlling the supplied power by controlling a triac 19 connected to a power supply line with a trigger circuit 20.

In addition, in the circuit shown in FIG. 1, the input side.

That is, if a capacitor is connected between the terminals T, even if a high surge voltage such as a lightning surge is applied, the current is shunted to this capacitor, so that the surge can be absorbed.

Effects of the Invention As described above, the present invention connects a switching element that turns on at a predetermined voltage in series with the ceramic varistor, so that the ceramic varistor is connected to the power supply only when a ringing surge voltage caused by resonance in the power distribution system is applied. Therefore, since the ceramic varistor does not operate at all during normal operation, loss and heat generation can be extremely minimized, and the circuit is inexpensive as it only requires one ceramic varistor. It is something that can be done.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a voltage waveform diagram including a ringing surge, and Figs. 3 (a) to (c).
are voltage and current waveform diagrams showing operation, Figure 4 is a characteristic diagram showing ringing surge absorption characteristics, Figure 5 is a voltage waveform diagram,
Figure 6 is a circuit diagram showing a modified example, Figure 7 is a circuit diagram showing an example of application to an electronic ballast, Figure 8 is a circuit diagram showing an example of application to a dimmer, and Figure 9 is a circuit diagram of a ceramic varistor. Characteristic diagrams showing the characteristics, FIGS. 10(a) to 10(c) are circuit diagrams showing various conventional examples, and FIG. 11 is a circuit diagram showing a different conventional example. 12... Ceramic varistor, 13... Thyristor (switch element), 16... Triac (switch element)

Claims (1)

[Claims] A surge absorption circuit characterized in that a switching element that is turned on at a voltage above the peak value of the rated voltage and below twice the peak value is connected in series to a ceramic varistor connected to a power supply line.