JPS6389912A - Electronic loading device - Google Patents

Abstract

PURPOSE:To realize desired load by single device by making calculation by a microcomputer on the basis of input voltage as sampling data and a set value corresponding to load characteristic and converting to analog signals. CONSTITUTION:Input voltage Va from an AC power source 2 to a loading device 1 is sampled and made to digital signals by an A/D converter 3, and calculation of load current Iai is made by a microcomputer 4. Current Iai is made to analog signals by a D/A converter 5 and made a load current set value of a current source 6. Then, input impedance Za=R, and becomes a fixed value. When obtaining inductive load, by making Iai obtained from Iai=[(Vai-Iai-1XR)XT]/L, where R, L are load characteristics set values, the loading device 1 having inductance L can be realized. Similarly, a loading device 1 having a fixed capacitance C can be realized simply.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is capable of handling resistive loads, inductive loads, capacitive loads, constant power loads, etc. in a single device connected to various power sources such as AC and DC. This invention relates to an electronic load device that can be realized with high accuracy.

(Prior Art) Conventionally, load devices as shown in FIGS. 8 and 9 are known. Of these, 21 in Figure 8
Reference numeral 22 indicates an AC power source, variable impedance devices such as variable resistors, variable inductances, variable capacitors, etc. In FIG. 9, 23 indicates a DC power source, and 24 indicates a constant current source.

In the circuit of FIG. 8, the variable impedance device 22
constitutes the load device [25, and if the voltage of the AC power supply 21 is V and the impedance of the variable impedance device 22 is Shi, then by setting this impedance to a predetermined value, any load current i=*/ You can get shi. On the other hand, in the circuit of FIG. 8, the constant current source 24 is connected to the load device 26.
If the voltage of the DC power source 23 is V and the current of the constant current source 24 is I, such a load device [26 can be said to be a load of impedance Z when viewed from the power source side.

(Problem to be Solved by the Invention) However, in the example shown in Fig. 8, it is generally difficult to realize a variable inductive load or capacitive load for an AC circuit as a constant impedance load, and in practice Since the values of inductance and capacitance are not ideal, there is a problem in that a load device having an impedance as set as the set value cannot be realized.

Furthermore, the load device shown in FIG. 9 is usually put into practical use only for DC circuits, and all of these conventional examples have the disadvantage that they cannot be made into constant power loads regardless of fluctuations in the power supply voltage. there were.

The present invention was proposed to solve the above problems, and its purpose is to
A resistive load of the desired value regardless of the power supply (including harmonic components, etc.),
An object of the present invention is to provide an electronic load device that can easily implement an inductive load, a capacitive load, a constant power load, etc. with a single device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an A/D converter that converts an input voltage from a power supply device sampled at a constant cycle into a digital signal;
and a microcomputer that calculates a load current setting value based on a load characteristic setting value that is set according to a constant power load, an inductive load, a capacitive load, etc., and a D that converts the load current setting value into an analog signal. /A converter, and a current source connected to the power supply device and generating a load current based on the analog signal.

In the present invention, a constant power load device is realized by using a constant power consumption value as the load characteristic setting value, and a constant power load device is realized by using a constant inductance or capacitance value as the load characteristic setting value. An inductive load device or a capacitive load device can be implemented.

(Function) In a microcomputer, load characteristic setting values (resistance value, Power consumption value, inductance value,
(capacitance value, etc.), performs a predetermined calculation, converts the result into an analog signal, and sends it to the current source as a load current setting value. The current source is connected to the power supply device applying the input voltage, and the above load characteristics are satisfied by supplying current according to the load current setting value.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an electronic load device 1 (hereinafter simply referred to as load device 1) according to the present invention, and this load device 1 is connected to both ends of an AC power source 2. As shown in FIG. That is, the load device 1 includes an A/D converter 3 connected to both ends of an AC power supply 2, a microcomputer 4 connected to its output side, a D/A converter 5 connected to its output side, and its output. A current source 6 is connected to the side of the AC power source 2, and a current source 6 is connected to both ends of the AC power source 2.

Next, the operation for obtaining a resistive load using this load device 1 will be explained. First, the set value of the load resistance as the load characteristic set value is assumed to be R [Ω]. If the input voltage from the AC power supply 2 to the load device 1 is *a, then this voltage *a has a period T
When sampling at , the instantaneous value V as shown in Figure 2
al + V a2+*a3f・・・・・・・・・
*an is obtained. These instantaneous values are converted into digital signals by the A/D converter 3, and the next-stage microcomputer 4 calculates the load current IaI for each sampling data using the equation 0.

IaI=Val/R・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・ ■Here, I al and Ω81 are t at each sampling time in Fig. 2.
The load current and input voltage at I (=t1.t2...+tn) are shown.

The load current Ia1 thus obtained is transferred to the D/A converter 5.
If it is converted into an analog signal by Regardless, it is always a constant value.

Next, the operation when obtaining a constant power load using this embodiment will be described. Here, the constant power load refers to a load that always consumes constant power regardless of fluctuations in input voltage. Now, if the set power consumption value as the load characteristic setting value is M, the input impedance a of the load device 1 is as follows: Za=vr”7M・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・■(
(r: effective value of input voltage Va)) Therefore, Za is controlled to follow Vr.

On the other hand, the load current Iai can be calculated as Ia+''=
Va+/Za=(M/Vr") If the set value is set, the load device 1 will always consume a constant amount of power M.

Note that the effective value *r is calculated by assuming that the input voltage *a is sampled nine times within one cycle as shown in Figure 3, and the instantaneous value of the voltage at each sampling time is calculated as V a I (= ÷ 819 * 82
1Ω839..., *an), it can be found from. In this embodiment, every time one sampling period elapses, Vr is determined using data sampled n times before that period.

Further, the operation when obtaining an inductive load using this embodiment is as follows. Now, as shown in Fig. 4, when operating as a series load with a resistance R and an inductance L, let each load characteristic set value be R [Ω) and L (H), respectively.
From the principle of L:LXdi/dt (VL is the terminal voltage of inductance L), Ial=((Val-Iai-1X
R) XT)/L...-■. Here, Ial
-1 indicates the calculated value of the load current one sampling period (=T) before.

Therefore, by setting Ial obtained by the calculation of Equation 0 as the load current setting value of the current source 6, it is possible to realize the load device 1 having a constant inductance L.

Furthermore, when obtaining a capacitive load, as shown in Figure 5, each load characteristic setting value is set to R (Ω) and C (F) (voltage across C) as a series load operation of resistor R and capacitor C. From the principle, it becomes as follows, and if the load current IaI obtained from these equations is set as the set value, the load device 1 having a constant capacitance C can be realized. Here, *zl is microcomputer 4
Data corresponding to the terminal voltage of the virtual capacitor C used in internal calculations, *Zi-4 indicates the data one sampling cycle (two T) before the data.

In any of the cases described above, if the operating speed of the A/D converter 3 or the microcomputer 4 is slow, the actual input voltage *a is delayed by At as shown in FIG. Therefore, in the calculation currently being performed, the input voltage at that time is not Va, but the voltage *a' that includes an error.
This results in a situation where the Furthermore, even if <74t=O as shown in FIG. 7, there is a delay equivalent to T/2 at maximum.

Therefore, in the actual calculation, the value of *a is changed to Δt+(
It is necessary to advance the calculation by T/2).

Specifically, the input voltage V after at + (T/2) time
The value of a is predicted and obtained, and the above-mentioned calculations for each load characteristic are performed using this voltage Va''' (see FIG. 7).

How to find this VaII is: ■ Find it by linear approximation using the previous value of Va. ■ Find it by quadratic approximation using up to the previous Va value. ■ When the input voltage is a sine wave. For this purpose, methods such as obtaining by sin approximation can be considered.

(Effects of the Invention) As detailed above, according to the present invention, not only resistive loads but also ideal inductive loads, capacitive loads, constant power loads, etc., which were previously unrealizable, can be adjusted to desired values. This can be achieved with high precision and with a single device.

Furthermore, even when the power source types are different, such as AC and DC, this can be easily handled by changing the software of the microcomputer, resulting in extremely high versatility.

[Brief explanation of the drawing]

1 to 7 show an embodiment of the present invention,
Figure 1 is a schematic block diagram, Figure 2 is a waveform diagram showing the relationship between input voltage and load current, Figure 3 is an explanatory diagram for determining the effective value of input voltage, and Figure 4 is an inductive load. circuit diagram,
Figure 5 is a circuit diagram of a capacitive load, Figures 6 and 7 are illustrations of errors between the actual input voltage and data used for calculation, and Figures 8 and 9 are diagrams of conventional examples. FIG. 1...Electronic load device 2...Power supply 3...A
/D converter 4...Microcomputer 5...D/A converter 6...Current source R...
Resistance L...Inductance C...
Capacitor Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (3)

[Claims] (1) an A/D converter that converts the input voltage from the power supply device sampled at a constant cycle into a digital signal; a microcomputer that calculates a load current setting value based on the digital signal and the load characteristic setting value; An electronic load device comprising: a D/A converter that converts a load current setting value into an analog signal; and a current source that is connected to the power supply device and generates a load current based on the analog signal. . (2) Claim 1 in which a load current setting value is calculated based on a constant power consumption value as a load characteristic setting value.
Electronic load device as described in section. (3) The electronic load device according to claim 1, wherein the load current setting value is calculated based on a constant inductance or capacitance value as the load characteristic setting value.