JPH0547414Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electronic load device used for output short-circuit testing of constant voltage (CV)/constant current (CC) power supplies.

[Prior Art] FIGS. 3 to 5 show circuits used in conventional CV/CC power supply output short-circuit tests. That is, Figure 3 is
The output terminals of the CV/CC power supply 1 are short-circuited using the switch S1 (or the contact of an electromagnetic relay), the short-circuit current value during the short-circuit is read, and the presence or absence of an abnormality is confirmed and recorded. In FIG. 4, a circuit consisting of a control element 2, a CC control device 3, a CV control device 4, a capacitor C1, etc. is used as the CV/CC power supply 1.
In the figure, a circuit including a control device 5, a CC control device 6, a CV control device 7, a transformer 8, a capacitor C1, etc. is used as the CV/CC power supply 1. Fourth
In the figure and FIG. 5, I1 is the discharge current of the capacitor C1, and I2 is the output current from the CV/CC power supply 1.

The CV/CC power supply 1 includes a large-capacity capacitor C1 between the output terminals. Therefore, when the output terminals are short-circuited, the first operation that occurs as shown in FIG. 6 is the discharging current I1 of the large capacity capacitor C1.
flows. This discharge current I1 has a very large peak value, although it is for a short time. Also, CV/CC
The output current I2 of the power supply 1 begins to flow, continues to increase as time passes, and is temporarily not limited until the current limiting circuit completes its response, so there is a period in which the output current exceeds the rated output current value.

[Problem to be solved by the invention] As mentioned above, in the output short-circuit test of a CV/CC power supply, a current much larger than the rated output of the CV/CC power supply temporarily flows. Relays are uneconomical because they must have contacts with a large current capacity. Furthermore, since the large-capacity capacitor built in between the output terminals of the CV/CC power supply is rapidly discharged, there is a possibility that this large-capacity capacitor will deteriorate.

This idea was made in view of the above circumstances.
It is an object of the present invention to provide an electronic load device that can prevent the deterioration of a large-capacity capacitor by preventing the discharge current of the large-capacity capacitor from becoming sudden, and that can also make short-circuit switches or electromagnetic relays economical. do.

[Means and effects for solving the problem] In order to achieve the above object, the present invention uses a constant voltage/
an electronic load consisting of a current control element connected between the output terminals of a constant current power supply, an error amplifier connected to the control terminal of the current control element, and a reference voltage generation circuit connected to the error amplifier; It is characterized by comprising an electromagnetic relay that is connected in parallel with the current control element and operates in the saturation voltage region of the current control element, and by using the electronic load and the electromagnetic relay together, the discharge current does not become sudden. In this way, control is performed on the short-circuit side, and the short-circuit can be sufficiently performed.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which the positive output terminal 10 of the CV/CC power supply 1 is connected to the input terminals 13 and 14 of the electronic load 12, and the negative output terminal 11 of the CV/CC power supply 1 is connected to the input terminals 13 and 14 of the electronic load 12. It is connected to the input terminal 15 of the electronic load 12. The input terminal 13 is connected to the collector of a current control element such as a transistor Q1, and the emitter of this transistor Q1 is connected to the terminal 15 through a resistor 16 and an ammeter 17 in parallel. The base of the transistor Q1 is connected to the output terminal of the error amplifier U1, the output terminal of the reference voltage generation circuit V1 is connected to the non-inverting input terminal of the error amplifier U1, and the inverting input terminal of the error amplifier U1 is connected to the output terminal of the transistor Q1. It is connected to the emitter. The input terminal of the reference voltage generating circuit V1 is connected to a power source via a reference power source starting switch S1b. The input terminal 14 is connected to the non-inverting input terminal of a comparator (also serving as a relay driver) U2 for detecting the output voltage of the CV/CC power supply, and the inverting input terminal of this comparator U2 is connected to the positive voltage of the reference power supply V2, such as 1 to 2V. The sides are connected. The output terminal of this comparator U2 is connected to the electromagnetic winding of electromagnetic relay RL1 via electromagnetic relay starting switch S1a, and this electromagnetic relay
The contact of RL1 is connected between the collector and emitter of the transistor Q1. The electromagnetic relay starting switch S1a and the reference power source starting switch S
1b are interlocked to constitute a short-circuit starting switch S1.

That is, until the short-circuit starting switch S1 is closed, the electromagnetic relay RL1 and the transistor Q1 are in an open state. Next, when the switch S1 is closed, the reference voltage generating circuit V1 is activated and sends the reference voltage to the error amplifier U1. By appropriately setting the rise time of this reference voltage, the slope of the current I3 flowing through the transistor Q1 (rate of increase in the current I3) can be made gentle, and the capacitor C1 between the output terminals of the CV/CC power supply 1 can be rapidly discharged. It can be controlled so that it does not occur.

That is, as shown in FIG. 2, when switch S1 is closed, current I3 starts to increase from point A in the CV region. As the current I3 increases, the current in the CV/CC power supply body also begins to increase, and eventually exceeds the rated output current and enters the current limit region, where the output voltage E1 begins to drop (CC region). The output voltage E1 continues to drop,
Eventually, the output voltage value approaches the saturation region of transistor Q1. If it continues as it is, the saturation voltage between the collector and emitter of transistor Q1 (point B
= 1~2V), and the short circuit becomes insufficient. In order to compensate for this insufficient short circuit, the saturation region section (between points B and C) of transistor Q1 is connected to electromagnetic relay RL1.
Cover with. Therefore, the electromagnetic relay RL1 is automatically driven by the comparator U2 for detecting the output voltage E1 of the CC/CV power supply 1 at the time B when the voltage E1 starts to drop to, for example, 1 to 2V. Incidentally, since the voltage E1 of the current I4 flowing through the electromagnetic relay RL1 has decreased to 1 to 2 V, the current capacity of the contacts of the electromagnetic relay RL1 is practically sufficient as long as it can cover the CV/CC power supply output current limit value.

As described above, when the short circuit start switch S1 of the electronic load 12 is closed, the output of the CV/CC power supply 1 completes the cycle from open to short circuit in the following order.

From point A to point B in Figure 2 is the transistor Q.
1, the short circuit current I3 flows. The time required to move from point A to point B is appropriately set by the reference voltage generation circuit V1.

Electromagnetic relay RL from point B to point C in Figure 2
1, the short circuit current I4 flows. The start of operation of electromagnetic relay RL1 is automated when the voltage value at point B is detected by comparator U2.

[Effects of the invention] As described above, according to the invention, by using an electronic load and an electromagnetic relay together in the output short circuit test of the CV/CC power supply, the discharge of the capacitor connected to the output terminal of the CV/CC power supply is It is possible to control the current so that it does not become sudden, and by using an electromagnetic relay to compensate for insufficient short circuits due to the saturation region of the electronic load, it is possible to prevent insufficient short circuits. It is economical because the current capacity of the switch or electromagnetic relay can be reduced.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a characteristic diagram showing an example of the output short-circuit operation of the CV/CC power supply according to the present invention, and Figures 3 to 6 are characteristic diagrams of the conventional
FIG. 3 is a diagram for explaining an output short-circuit test of a CV/CC power supply. 1...CV/CC power supply, 12...Electronic load, Q1
...Transistor, U1...Error amplifier, V1...
...Reference voltage generation circuit, U2...Comparator,
RL1... Electromagnetic relay, S1... Short circuit start switch.

Claims (1)

[Claims for Utility Model Registration] A current control element connected between the output terminals of a constant voltage/constant current power source, an error amplifier connected to the control terminal of this current control element, and a reference connected to this error amplifier. An electronic load device comprising: an electronic load including a voltage generating circuit; and an electromagnetic relay connected in parallel with the current control element and operating in a saturation voltage region of the current control element.