JPH04102070A - Digital current detection device - Google Patents

Abstract

PURPOSE:To obtain a device which is strong against disturbance and has less adjusted locations by using an up/down (A/D) counter and a digital/analog (D/A) converter. CONSTITUTION:A Hall element 1 generates an output which matches DELTAH which is obtained by adding a magnetic field Hf created by a secondary coil 7 to a magnetic field Hi which is generated by a detection current. This output is amplified b an amplifier 2, its power Ez is input by a zero-cross comparator 3, and an output Ec is set to L or H level according to Ez<0 or Ez>0. An A/D counter 4 where this Ec is input counts up a clock CL of a clock generator 9 when the level is L and counts down when it is H and then takes out as a digital output Od. At the same time, this output is converted into an analog value by a D/A converter 5 and this analog value controls current of the coil 7. Then, the magnetic field Hf cancels out a magnetic field Hi and then feds back signal so that the DELTAH is equal to 0, thus obtaining the digital output Od corresponding to the detecting current from an output of a counter 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current detection device, and more particularly to a current detection device with digital output.

[Conventional technology]

Conventionally, an analog output device as shown in FIG. 4 has been known as a current detection device.

This device detects a magnetic field Hi created by a detection current with a Hall element 40, amplifies it with an amplifier 41, and outputs it as an analog output Oa through a current booster 42.
A current is passed through the secondary coil 43 to generate the magnetic field H1 of the detection current.
There is a feedback type current detector that operates to provide feedback to cancel out the

However, since many devices that use current detectors these days are digital control devices, current detection devices are also required to have digital output. For this reason, the analog output obtained by this device has been converted into an expensive analog/digital converter to obtain a digital output.

[Problem to be solved by the invention]

The conventional device described above requires an expensive analog/digital converter to obtain a digital output, and since the current detection device is analog, it is susceptible to disturbances and requires many adjustments.

An object of the present invention is to obtain a current detection device that is resistant to external disturbances and requires fewer adjustment points because it directly obtains a digital output without using an expensive analog/digital converter.

[Means to solve the problem]

The above purpose is to connect a voltage comparator, up/down counter, and digital/analog converter between the feedback loop amplifier and current booster of a feedback type current detector, and to take out the output of the up/down counter as a digital output. achieved by.

[Operation] The voltage comparator becomes H level or L level depending on the output amplitude of the amplifier. As a result, the up/down counter is
When the input is at H level, the reference signal is counted down,
When the input level is L level, it counts up. This counter output is converted into a digital/analog converter.
Convert to analog. The current in the secondary coil is controlled by this analog value, and feedback control is performed so that the magnetic field applied to the Hall element returns to its original position. Therefore, a digital output corresponding to the current to be detected can be obtained as the output of the counter.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows the circuit configuration of the present invention.

In FIG. 1, Hi is a magnetic field generated by the detection current, and the Hall element 1 detects the magnetic field ΔH, which is the magnetic field H created by the feedback secondary coil 7, which is added to the magnetic field Hi, and the magnetic field ΔH is Generate reasonable output. This output is amplified by an amplifier 2 and input to a zero cross comparator 3. The zero cross comparator 3 has an input voltage Ez of Ez
<O or E z > Determine whether it is O. MoteE
When z < O, output Ec is set to L level, and E z >
When it is O, it is set to H level. This output Ec serves as an up/down switching signal for the up/down counter 4 to count up or down the clock CL from the clock oscillator 9. After converting the digital output Od of the up/down counter 4 into an analog value through a D/A converter 5, a current is passed through a current booth 6 to a secondary coil 7, thereby creating a magnetic field Hf.

This magnetic field Hf operates to exactly cancel the magnetic field Hi created by the detected current i, and is fed back so that the added magnetic field ΔH of both becomes zero. Therefore, a digital output Od that follows the current to be detected is obtained from the output of the up/down counter 4. Further, 8 is a power supply for driving the Hall element.

FIG. 2 shows a specific example of the configuration of the present invention in which the detection mechanism is modeled, and FIG. 3 shows waveforms of various parts for explaining FIG.

The present invention will be specifically explained with reference to FIGS. 2 and 3. Current terminal I, 1. When a detected current i is applied to the magnetic body I
A magnetomotive force is generated by the coil C1 wound around A, and a magnetic field Hi is generated in the gap GP of the magnetic body IA. This gap G
A Hall element 1 driven by a constant current 10 is arranged at P. Output e of Hall element 1. is amplified by amplifier 2,
The output is compared with a reference voltage Er by a voltage comparator 3'.

Output e. When is higher than the reference voltage Er, the output Ec is set to H level, and when it is lower than the reference voltage Er, the output Ec is set to L level. Using this voltage Ec, the up/down counter 4 counts up or down the reference clock CL. The output of this counter 4 is a digital quantity, which can be taken out as a digital output Od, and also can be further digital/analog converted and the output can be taken out as an analog output Oa. moreover,
The output is amplified by an amplifier 10, and its output is connected via a resistor R to a secondary coil 7 wound around a magnetic material IA, and a current is passed through the secondary coil 7 to generate an electromotive force in the opposite direction to the magnetomotive force generated by the detected current l. A magnetic force is generated to generate a magnetic field Hf in the opposite direction to the magnetic field Hi generated by the current to be detected i in the air gap GP, and the feedback circuit as a whole is configured.

FIG. 3 shows an example in which the detected current 1 is a sine wave as shown. As this current l flows, a magnetic field H which is proportional to it is generated, so if there is no feedback, the output e of the Hall element 1. The waveform also appears as shown in the figure. However, due to feedback, the output e0 of the Hall element 1 is shown as e in the figure.

It becomes an almost constant value. Next, voltage comparator 3'
If the reference voltage Er of is set to zero, the output of the Hall element 1 is e. When Ec is larger than zero, the output Ec of the voltage comparator 3' becomes H level, and when it is smaller, it becomes L level, so H and L are repeated as shown in Ec. the result,
Assuming that the reference clock is CL shown in the figure, the magnitude of the digital output Od of the up/down counter CUN4 is expressed as Od shown in the figure (which pseudo-indicates a digital amount), that is, the up/down counter When the voltage Ec is at the H level (A) point, the output is increased by up-counting every clock CL, and the voltage Ec is at the L level (A).
At point b), the output is decreased by counting down every clock CL.

When this digital output Od is applied to the digital/analog converter 5 and the analog output Oa is passed through a filter, it becomes ○a as shown in the figure. When this output Oa is applied to the resistor R and the secondary coil 7 through the amplifier 10, the current ic of the coil 7 is
becomes a sine wave as shown in the figure.

Here, the frequency of the reference clock CL is shown as approximately 60 times the frequency of the detected current i, but if this multiplier is increased, the value of the digital output Od will also become a smooth sine wave and the frequency of the detected current 1 will increase. This increases the response speed for tracking.

Furthermore, in the above embodiment, since the reference voltage Er of the voltage comparator 3 is set to zero, the magnetic fields H4 and 2 generated by the detected current i
The next coil 7 operates so that the magnetic fields Hf generated by the current IC are equal, but when the reference voltage Er has a certain value, it operates so that a predetermined constant difference occurs between the magnetic fields H4 and Hf0. By adjusting the voltage, it is possible to always have a bias magnetic field at the operating point of the Hall element l,
A Hall element 1 having excellent sensitivity and linearity can be selected and used.

〔Effect of the invention〕

As described above, according to the present invention, it has a simple circuit configuration, is strong against disturbances, has few adjustment points, and has a simple circuit configuration that eliminates the need for expensive and complicated analog/
A digital output current sensing device can be obtained using an inexpensive and simple digital/analog converter and a counter without requiring a digital converter. Furthermore, high-precision digital output and easy-to-handle analog output can be output at the same time.

Furthermore, since the operating point of the magnetic field/voltage conversion element can be freely selected, there is an effect that even a conversion element that does not have high characteristics can be used satisfactorily.

[Brief explanation of drawings]

1 to 3 show the configuration of an embodiment of the present invention. FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of an embodiment of the present invention modeling the detection mechanism. FIG. 3 is an explanatory diagram of the operation of FIG. 2, and FIG. 4 is a diagram of a conventional example. Hi: Magnetic field created by the current to be detected, Hf: Magnetic field created by the secondary winding, 1. Hall element, IA: Magnetic material, 2.. Amplifier, 3.. Zero cross comparator, 3'.. Voltage comparator. 4.Up/down counter, 5.Digital/analog converter, 6.Current booster, 7.Secondary coil, 8.Power supply for Hall element, 9.-Clock oscillator, lO..Amplifier, GP. ...Gap in magnetic material, C1...
Primary coil, CL...clock, Er...reference voltage. 1-+, Jbl, S-, 2...Anobu 3-
・Zurirosko/Pareku 4・・Arano Yu'tsu//7 Kushita Ranrozu

Claims (1)

[Claims] 1. In a current detection device, there is a circuit that converts the magnitude of current into voltage, and when the detection voltage detected by this circuit is higher than a predetermined reference voltage Er, the reference clock is increased ( down) and if low then down (up)
An up/down counter for counting is provided, and the output obtained by the up/down counter is taken out as a digital output and converted to an analog value through a D/A converter, and this analog value is set in a direction to cancel the detected voltage. A digital current detection device characterized in that it is configured to add. 2. The digital current detection device according to claim 1, wherein the reference voltage Er is variable. 3. A digital current detection device according to claim 1, characterized in that the digital output is taken out from the output side of the up/down counter and the analog output is taken out from the output side of the D/A converter.