JPS61251422A - Constant current apparatus - 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 Field of Application The present invention relates to a constant current device, and particularly to a constant current device in which a plurality of constant current sources are connected in series and overvoltage when the load is released is absorbed by a varistor or the like. Related to constant current device.

Summary of the Invention The constant current device of the present invention comprises a constant current circuit in which a plurality of constant current sources are connected in series to a load, each of which has a voltage equalizing resistor and a bypass diode connected in parallel to the output terminal; In a constant current device equipped with an overvoltage protection element for preventing the output voltage applied to the load from increasing more than necessary when the output voltage is It is connected to.

When selecting the number of constant current sources to be used according to the load voltage, the operating voltage of the overvoltage protection element can also be automatically set, eliminating the need for tap switching operations to set the operating voltage of the overvoltage protection element. Furthermore, there is an effect that deterioration or destruction of the overvoltage protection element due to erroneous operation can be prevented.

Prior Art FIG. 2 is a circuit diagram showing an example of a conventional constant current device of this type. That is, a plurality of overvoltage protection elements 6 ( For example, connect a barista),
The number of overvoltage protection elements 6 to be used is switched and set by tapping. The output voltage is monitored by the alarm detection circuit 7, and when the output voltage exceeds a certain value, the operation of each constant current source 2 is stopped, thereby preventing abnormal voltage from being applied to the load.

As shown in FIG. 3, the alarm detection circuit 7 divides the output voltage with voltage dividing resistors 11 and 12, inputs the divided voltage to the comparator 14, and compares it with the reference voltage 13 in the comparator 14, so that the output voltage is kept constant. When the value exceeds the value, the output of the comparator 14 causes the relay 15 to operate, and the relay contact 18 causes the constant current sources 2 to stop operating.

The detection voltage of the alarm detection circuit 7 can be set to any voltage by adjusting the reference voltage 13 or the voltage dividing resistors 11, 12, etc. On the other hand, the (total) operating voltage of the plurality of overvoltage protection elements 6 is set to an appropriate value by tap switching. Of course, when the load voltage is normal v0, the current of the overvoltage protection element 6 is extremely small, and the alarm detection circuit 7 is inactive.If the output voltage rises abnormally, for example when the load is released, the overvoltage protection element 6 will first be activated. Constant current■. As a result, the output voltage is suppressed to the operating voltage of the overvoltage protection element 6, and when the alarm detection circuit 7 detects the overvoltage and the relay 15 operates to stop the constant current fR, the output voltage becomes O. This prevents overvoltage from being applied to the load.

By the way, the efficiency of a constant current circuit is as shown in Figure 4.
The higher the output voltage, the better; the lower the output voltage, the worse. This is because the higher the output voltage, the lower the fixed loss (control section loss, etc.) of the constant current source 2 becomes. Therefore, when the load voltage is low, it is necessary to reduce the number of constant current sources 2 used to increase efficiency. For example, let the rated output voltage of the constant current source 2 be vl, and the load voltage be V, Then, in the case of 2 V 1 < Vo < 3 V l, three constant current sources 2 are used, and in the case of V□<V, <2V□, two constant current sources 2 are used, and V, <V.

In this case, one constant current source 2 is used to improve efficiency. In this case, depending on the number of constant current sources 2 used,
Overvoltage protection element 6 is activated by manually switching taps.
It goes without saying that the number of relays to be used can be selected to prevent the voltage applied to the load, such as a relay device, from increasing more than necessary when the load is released. Therefore, in the conventional constant current device described above, it is necessary to set the taps to switch according to the load voltage, and if the number of overvoltage protection elements 6 than the required number is connected by mistake, the overvoltage will be reduced when the load is released. There is a drawback that when an excessive voltage is applied to the protection element 6, the characteristics of the overvoltage protection element 6 may deteriorate or be destroyed until the alarm detection circuit 7 stops the constant current source 2.

Problems to be Solved by the Invention The present invention solves the above-mentioned conventional drawbacks, and when selecting the number of constant current sources 2 to be used according to the load voltage, the number of overvoltage protection elements 6, and therefore, Overvoltage protection element (overall)
To provide a constant current device in which an operating voltage is also automatically determined, thereby preventing deterioration and destruction of an overvoltage protection element due to the complexity of tap switching operations and erroneous settings.

Composition of the Invention The constant radio wave device of the present invention includes a constant current circuit in which a plurality of constant current sources each having an output terminal connected in parallel with a resistor for voltage equalization and a bypass diode are connected in series with respect to a load, and In the constant current device, the overvoltage protection element is provided in parallel with the output of each of the plurality of constant current sources. characterized by being connected.

Embodiments of the Invention Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. That is, the voltage equalization sharing resistor 3 and the bypass diode 5
A plurality of constant current sources 2, each of which is connected in parallel to the output terminal, are connected in series to the load 8.The output voltage is monitored by the alarm detection circuit 7, and when the output voltage exceeds a certain value, each constant current source 2 is connected in series to the load 8.
As is the case with the conventional method, abnormal voltage is prevented from being applied to the load by stopping the operation.

However, in this embodiment, overvoltage protection elements 6 are connected in parallel to each output of the plurality of constant current sources 2, respectively. Therefore, when the number of constant current sources 2 used is reduced in accordance with the load voltage, the number of overvoltage protection elements 6 used is also reduced accordingly.

In other words, by suppressing the output voltage of each constant current source 2 by the overvoltage protection element 6 connected to each output, the overall output voltage is prevented from exceeding a certain value. In other words, the (total) operating voltage of the overvoltage protection element is determined according to the number of constant current sources 2, and the conventional tap switching operation for setting the operating voltage of the overvoltage protection element is eliminated. , it is possible to prevent deterioration or destruction of the overvoltage protection element due to erroneous operation.

Effects of the Invention As described above, in the present invention, in a constant current device in which a plurality of constant current sources are connected in series, an overvoltage protection element is connected in parallel to the output of each constant current source. When selecting the number of constant current sources to be used according to the above, it becomes possible to automatically set the operating voltage of the overvoltage protection element. That is, there is an effect that unlike the conventional method, a tap switching operation is not required to set the operating voltage of the overvoltage protection element, and deterioration or destruction of the overvoltage protection element due to erroneous operation can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an example of a conventional constant current device, Fig. 3 is a detailed circuit diagram of the above-mentioned conventional alarm detection circuit, and Fig. 4 is a diagram showing the relationship between output voltage and efficiency of a constant current circuit. In the figure, 2 constant current sources, 3: resistance for equal voltage sharing,
5: /Hypass diode, 6: Overvoltage protection element, 7
: Alarm detection circuit, 8: Load, 11゜12: Voltage dividing resistor, 1
3: Reference voltage, 14: Comparator, 15: Relay, 1
6: Relay contact.

Claims (1)

[Claims] A constant current circuit in which a plurality of constant current sources each having a voltage equalizing resistor and a bypass diode connected in parallel to the output terminal are connected in series to a load, and In the constant current device equipped with an overvoltage protection element for preventing the output voltage applied to the output voltage from increasing more than necessary, the overvoltage protection element is connected in parallel to the output of each of the plurality of constant current sources. Characteristic constant current device.