JPH01100468A - Electronic load apparatus - Google Patents

Abstract

PURPOSE:To prevent a hunting otherwise caused by an electronic load along with a reduction in man-hour of automatic test, by switching a current value fixed mode over to a resistance value fixed mode immediately before a drooping mode without selecting characteristic of a power source unit. CONSTITUTION:In the initial state of an electronic load 3, a changeover switch 9 is connected to a contact 1 to enter a current value fixed mode and a set value from a personal computer 6 is applied to an amplification circuit 14 through a D/A converter 19. On the other hand, a voltage across a resistance 18 for detecting current is inputted into a division circuit 12 by way of an amplification circuit 15 and an A/D converter 16 to hold a current flowing through the resistance 18 at an indicated value with a transistor 7. At this point, an output value of the division circuit 12 is stored sequentially into a register 20 and when an output of a subtraction circuit 21 is negative as indicating the gradient of a current-voltage characteristic of a power source 2 to be tested, an FF 24 is set to connect the changeover switch 9 to a contact 2. In this case, a voltage as electronic load 3 is applied to an amplification circuit 10 to operate a circuit system in the resistance value fixed mode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic load control device (electronic load) used during automatic power supply testing, and particularly to an electronic load device suitable for overcurrent mode testing of a power supply.

[Conventional technology]

Generally, when testing a power supply unit, for example, when automatically measuring voltage Φ current characteristics, each device is connected as shown in FIG. Apply AC power to the power supply unit under test @2'' and keep it constant during the test (the output terminal (+) of the power supply unit under test 2 is connected to the (+) pole of the electronic load "5", The output terminal (-) of unit 2 is connected to electronic load 1 through ammeter 4.
4" (-) pole.

Further, a voltmeter 5 is connected to the output terminals (+) and (-) of the unit 2 for voltage measurement.

Each device used here has a measurement interface (
For example, a personal combinator 6 is connected to the same bus for controlling each device connected to this bus.

Personal as shown in Figure 5; bus 7 from the ambiator.
The current value of the electronic load 5 is controlled through this.

Here, the output current from the power supply unit is read with an ammeter 4°, and the output voltage of the power supply unit is read with a square meter 5. If the above is considered as one cycle and the current value is increased at regular intervals, the voltage/current customization shown in FIG. 2 can be obtained. Note that related devices of this type include, for example, Japanese Unexamined Patent Publication No. 57-212514.

[Problem that the invention seeks to solve]

The above conventional technology has the following problems, and when the load characteristic is (0) characteristic in FIG.
If the current value flowing into # is constant regardless of the applied voltage value), the current value will reverse when it exceeds the drooping point of the power supply unit (point in Figure 2). Since the current decreases, the control from the personal combinator 6 and the control of the Naruko load 5 itself become impossible, and the output current from the power supply unit 2 is fixed at (, p (from 0 point to 7,
Characteristics up to 1 are not possible. Alternatively, disturbances such as interruption of current reading may occur, making it impossible to obtain accurate measured values. Alternatively, the power supply unit under test could be damaged due to this phenomenon.

This was a serious problem for a power supply unit testing system. In addition, in order to avoid the above problems, the electronic load 3 is operated in constant resistance control mode (electronic load 5 terminals (+) (-
) mode where the resistance value between ) is constant), but since the increment of current is not constant, when analyzing measured values
There is a problem in that the number of analysis steps increases compared to the case of constant current value control. This is a serious problem in measurement systems.

An object of the present invention is to solve the above problems and provide a safe and quick electronic load device as a test system.

Means for Solving Problem c] The above problem can be achieved by operating in constant current value mode up to the drooping point in FIG. 2, and thereafter switching to constant resistance value mode.

That is, the decision to switch is made by comparing the current measured value and the previous measured value using a test procedure that increases at a constant rate, and then storing the difference in memory circuit A, and then storing the difference in memory circuit A. If the current difference value is lower than the previous difference value, it is determined that the power supply under test is close to the drooping point, and switching is performed. Note that when this formula is used, switching is not performed in response to a sudden voltage drop at the point where the current starts to flow from zero output current, which is a general characteristic of a power supply unit, because the rate of change is in the decreasing direction tb.

[Effect]

Since it only requires the addition of a simple logic of storing the immediately preceding data and comparing it with the current data, it is inexpensive and does not impair reliability.

In addition, since switching is determined based on the slope of the characteristics, there is no malfunction even when the voltage changes from no load to load, making it stable and reliable.

〔Example〕

An embodiment of the present invention will be explained in detail below with reference to the drawings. FIG. 4 shows a conventional example, and FIG. 5 shows an example. Here, an explanation of the operation of the test system will be omitted.

The current value from the personal combinator 6 is the pass line 7.
Through this, a large eK input to the electronic load 5 is obtained.

The line C is converted to D-Ai via the D-A converter 19, and is connected to the amplifier circuit 14f) (+) input terminal VC.
Ru. The reference voltage B is applied to the amplifier circuit 10 through the changeover switch 9.
Connect to the (+) input terminal of the A-D converter 11 for output.
The other input is connected to the (+) input terminal of the amplifier circuit 15 from the connection point between the current detection resistor 1B and the emitter of the control transistor 1S, and the output is connected to the input of the divider circuit 12 through the A-D converter. 16 is applied. The output of the divider circuit 1.2 is connected to the (-) input terminal of the amplifier circuit 14 via the DA converter 15. Further, the output of the division circuit 12 is added to the register 20.

Register 2o is divided into four programs, and if they are set to 5.2 and 1.0, input the value mentioned above to 5 of register 0 register 20, and input the value previously stored in 6 of register 20 to register 20. Transfer the CVc of In addition, the outputs of registers 2 and 5 of the register 20 are used as two input signals of the subtraction circuit 25, and the subtraction circuit 23
The difference output is inputted to 1 of the register 20. register 20
The value stored in 1 is moved to 0 in register 20. The outputs of 0 and 1 of the register 20 are used as two input signals of the subtraction circuit 210, the difference output of the subtraction circuit 21 is used as the input of the determination circuit 22, and the output is passed through the flip-flop 24 and used as a drive signal for the changeover switch 9.

When testing the power supply unit, perform the following operations.

In the initial state of electronic load °5", selector switch 9 is always set to ■
(Idl, constant flow mode).

The setting value from the personal combination 6 is applied as an analog quantity to the (+) input terminal of the amplifier circuit 14 from the DA controller 19Vc. The voltage generated across the current detection resistor 18 is transmitted to the amplifier circuit 15. A-D converter 1
6 into a digital amount (this value is referred to as A). Since the current value is constant mode, the input of the amplifier circuit 10 is a constant voltage power supply, and the output digital amount of the A-D converter 11 is constant (this value is referred to as B). ), then the output of the division circuit 12 is =A-B, which is a constant value. This value is converted into an analog quantity by the DA converter 15vc and applied to the (-) input terminal of the amplifier circuit 14. of the amplifier circuit 14 (
The system operates so that the +) and (-) input terminals are the same. For example, when (-) is lower than (+), the output of the amplifier circuit 14 becomes high (and the transistor 17 operates in the on direction. The current value flowing through the current detection resistor 18 is increased (this is continued until the (+) and (-) inputs of the amplifier circuit 14 become the same. In the opposite case, each element operates in the opposite way). That is, the current flowing through the current detection resistor 18 is held at the value instructed by the personal combinator.The output value of the division circuit 12 at this time is stored in 5 of the register 20.This value is designated as E. The value stored in 3 of register 2G is shifted to 2 of register 20 (.This value is referred to as F. 1vc of register 2' stores the value of FE. The stored value is shifted to 0 in the register 20. Since the output of the subtraction circuit 21 is the difference between 0 and 1 in the register 2G, it is a value representing the slope of the current/voltage characteristics of the power supply unit under test. It is.

To explain this using the current/voltage characteristic graph shown in FIG. 6, in area 2, the value is iV at 0 of register 20, the value is JV at 1 of register 20, the value is F at 2 of register 20, and the value is at register 20. E values are stored in 5 of 5, respectively, and as is clear from FIG.
iζ becomes 0, and the output of the subtraction circuit 21 becomes a negative value.

It is determined whether this output is positive or negative, and if it is negative, the clip 70 tab 24 is set and the selector switch 9 is connected to the ■ side. In this case, the voltage of the (+) pole of the electronic load 5 is applied to the (+) input terminal of the amplifier circuit 10. In this mode, the circuit system operates so that the current flowing through the current detection resistor 18 is proportional to the voltage at the (+) pole of the electronic load 5. (Voltage ÷ Current = Resistance - Constant; Constant resistance mode) According to this embodiment, the constant current mode can be switched to the constant resistance mode immediately before the droop mode regardless of the characteristics of the power supply unit, reducing the number of man-hours required for automatic testing. It is effective in shortening the time and preventing disturbances caused by electronic loads.

〔Effect of the invention〕

According to the invention, the characteristics of the power supply unit under test.

Since the test can be performed immediately without a preliminary test of the overcurrent droop value, the test man-hours can be shortened and the power supply unit under test is not damaged (the true characteristics can be measured).

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the system configuration during automatic power supply unit testing, and Figure 2 is a general power supply current/voltage 8.
FIG. 5 is a diagram showing the current change during automatic testing; FIG. 4 is a block diagram showing the circuit configuration of a conventional electronic load device. FIG. 5 is a block diagram showing a circuit configuration of an electronic load device according to an embodiment of the present invention, and FIG. 6 is a diagram showing general characteristics of voltage and current of a power supply. 1... AC voltage, 2... Power supply unit under test, 5.
...Electronic load device, 4...Ammeter, 5...Voltmeter,
6...Personal Combiator, 7...Bath, 8.
... Constant tEE' as source, 9... Selector switch, 10,1
4.15...Amplification circuit, 11.16...A-D converter, 15.19-D-A converter, 17...
Transistor, 18...Resistor, 20...Resistor,
21.25... Subtraction circuit, 22... Judgment circuit, 24
-7 lipflop. Dashi

Claims (1)

[Claims] 1. An electronic load device that has a transistor for controlling current, a resistor for detecting current, a means for detecting a current value and matching it with an instruction value from a host device, and a means for controlling the current value and resistance value by switching them to a constant value. A register for storing current values, two subtraction circuits for calculating the difference between current values, and a determination circuit for determining whether the output signal value is positive or negative are provided, and the flip-flops are set and reset by the signals. An electronic load device characterized in that it is configured to switch between a constant current value mode and a constant resistance value mode.