JPH0547417Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electronic load device equipped with an electronic load with external control that is used as a load for the power supply under test in a power supply test equipment, and in particular, the present invention relates to an electronic load device equipped with an electronic load with external control, which is used as a load for the power supply under test in a power supply test equipment. The present invention relates to an electronic load device that prevents the output current of a power supply under test from overshooting when switching from mode to constant current mode.

[Prior Art] Conventionally, there has been an electronic load device that operates by being switched to a constant resistance mode or a constant current mode based on an external control signal. In the constant resistance mode, the electronic load acts as a constant resistance value, and in the constant current mode, the output current of the electronic load is constant.

On the other hand, there have conventionally been power supply test devices that test the characteristics of a power supply under test. When testing the output characteristics of a power supply using this test device, an electronic load device is used as the load.

In a power supply characteristic test, if the power supply under test does not start up if the electronic load is used in constant current mode, the electronic load device is initially started up in constant resistance mode, as shown in FIG. After an appropriate amount of time has elapsed, the electronic load device is switched to constant current mode (switched by an external signal), and the output current of the power supply under test is measured in a state where the current is constant.

The above sequence is adopted because testing in constant resistance mode may result in poor current setting accuracy and may cause problems in tests where data changes depending on the load value.

Note that for tests where the load setting value does not directly affect the test, the test may be performed in constant resistance mode.

[Problem to be solved by the invention] By the way, when switching to the constant current mode as described above and setting the control signal given from the outside as shown in Figure 3B, the electronic load does not operate within the operating range of the Figure 3. Overshoot appears as shown in d. The power supply under test may automatically shut down when such an overshoot occurs, which has the disadvantage that the intended test cannot be performed.

There is also a method to slow down the rise by attaching an RC filter to the current setting terminal, but this method cannot be used because it is not possible to perform tests in which the load changes rapidly.

The purpose of this invention was to prevent overshoot from occurring in the output current of the power supply under test when switching from constant resistance mode to constant current mode, and to perform stable measurement tests. The aim is to realize an electronic load device that can perform the following steps.

[Means for Solving the Problems] In order to achieve these objectives, the present invention provides a power supply that is connected as a load to the power supply under test and that operates in either constant resistance mode or constant current mode. , an electronic load whose constant current value is determined according to an externally applied control voltage in constant current mode, a control voltage output circuit that provides a control voltage to this electronic load, and a control circuit that controls this control voltage output circuit. The control voltage applied when the electronic load is switched from the constant resistance mode to the constant current mode is raised stepwise to the rated value under the control of the control circuit.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of essential parts of an embodiment of an electronic load device according to the present invention. In the figure, 1
is the power supply under test, 2 is connected as a load of the power supply under test, and operates in either constant resistance mode or constant current mode (mode switching is by an external signal). 3 is a control voltage output circuit that provides a control voltage to the electronic load 2; for example, a digital-to-analog converter (hereinafter referred to as a DA converter) is used.

4 is a control circuit that controls the control voltage output circuit 3;

The control circuit 4 generates a digital signal for applying a voltage signal as shown in FIG. 2B to the electronic load 2.
It is now possible to output to the DA converter 3.

According to such a configuration, the control circuit 4
As shown in Fig. 2, a voltage V _CR (control voltage at rated current value) is applied to the electronic load 2 in constant resistance mode, and immediately after switching to constant current mode, a stepwise pattern ( In the figure, increasing voltage is applied in five stages. The final value is the voltage V _CC at the rated current value.

The power supply under test 1 is set to constant resistance mode as shown in Figure 2 C, and then the primary input voltage is applied, and the output voltage V and output current I are as shown in Figure 2 D and E, respectively. stand up.

In order to switch from constant resistance mode to constant current mode, the control voltage is once set to OV, but at this time the output current of the power supply falls to 0 as shown in the figure.

After switching to the constant current mode, the control voltage is increased stepwise as shown in FIG. Correspondingly, the output current of the power supply under test rises in a stepwise manner as shown in E of the figure. No overshoot occurs at the rise of each step. Of course, no overshoot occurs when the rated current level is reached from the last step.

After switching to constant current mode in this way, the output current of the power supply under test can be prevented from overshooting by raising the control voltage stepwise to the rating instead of raising it all at once. The current increases to the rated current without any The rise time in this case is extremely short compared to the case where a CR filter as described in the prior art is used.

[Effects of the invention] As explained in detail above, according to the invention,
When switching from constant resistance mode to constant current mode,
It is possible to carry up to the rated current of the power supply under test without overshooting the output current.

[Brief explanation of the drawing]

Fig. 1 is a main part configuration diagram showing one embodiment of an electronic load device according to the present invention, Fig. 2 is an operation waveform diagram of each part,
FIG. 3 is an operation waveform diagram for explaining the operation of the conventional system. 1... Power supply under test, 2... Electronic load, 3... Control voltage output circuit, 4... Control circuit.

Claims (1)

[Claims for Utility Model Registration] It is connected as a load to the power supply under test, and operates in either constant resistance mode or constant current mode, and in constant current mode, it Equipped with an electronic load that determines a constant current value, a control voltage output circuit that applies a control voltage to this electronic load, and a control circuit that controls this control voltage output circuit, the electronic load can be switched from constant resistance mode to constant current mode. 1. An electronic load device characterized in that a control voltage applied when the load is applied is increased stepwise to a rated value by control of a control circuit.