WO2012083686A1

WO2012083686A1 - Current transformer, current detection circuit, and current detection method

Info

Publication number: WO2012083686A1
Application number: PCT/CN2011/077364
Authority: WO
Inventors: 梁永涛
Original assignee: 华为技术有限公司
Priority date: 2011-07-20
Filing date: 2011-07-20
Publication date: 2012-06-28
Also published as: CN102308348A

Abstract

A current transformer, a current detection circuit, and a current detection method are provided. The occupation space of a lay-out board in a print circuit board can be reduced, and the distributed inductance can be decreased at the same time. The current transformer comprises a hollow magnetic core(1).The hollow magnetic core(1) is used for arranging a current carrying conductor(5) to be detected in a loop to be detected(41).A coil(2) is wound on a sidewall of the hollow magnetic core(1) along the direction in parallel with the center axis of the hollow magnetic core(1).The coil(2) have two input terminals(3,4).The two input terminals(3,4) are used for electrically connecting with a detection signal output circuit(43).

Description

Current transformer and current detecting circuit and detecting method

The present invention relates to the field of electrical technology, and in particular, to a current transformer, a current detecting circuit and a detecting method.

Background technique

In the field of electrical technology, in order to control the output current and protect the power device, it is necessary to detect the current on some lines. Commonly used current detection techniques include resistance detection current, current transformer detection current, and the like. The method of detecting current by a resistor is low in cost, simple in circuit, and fast in response, but when detecting a large current, the power loss of the resistor is large. Therefore, in the case where it is required to detect a large current and requires low loss, a current transformer is generally used in combination with a resistor to detect the current.

The conventional current transformer structure is shown in Fig. 1. The primary winding 11 and the secondary winding 12 are respectively wound on the same magnetic core, and the primary winding 11 is serially connected to a circuit that needs to detect current (ie, the circuit to be detected), twice. The winding 12 is connected to an output loop of the detection signal (i.e., the detection signal output circuit), wherein the number of turns of the primary winding 11 is much smaller than the number of turns of the secondary winding 12.匝The number of turns of the primary winding 11 is N1, the number of turns of the secondary winding 12 is N2, and the current of the circuit to be detected is assumed to be II, and the current of the detection signal output circuit is 12, then the formula I1N1=I2N2 is known, the detection signal is output. The ratio of the current 12 of the circuit to the current II of the circuit to be detected is N1: N2. Usually, since N2 is much larger than N1, the current of the circuit to be detected is scaled down to a small current, so that it is convenient to use the resistor to detect the A small current is described without causing large losses.

In the process of realizing the current transformer current detection, the inventors have found that at least the following problems exist in the prior art: The current transformer includes structural components such as a primary winding, a secondary winding, and a magnetic core, and thus occupies a large printed circuit board. The layout area of the PCB, thereby reducing the power density of the electrical device. At the same time, when the current transformer is connected to the high current loop, the distributed inductance of the large current loop is increased, causing some voltage spikes and electromagnetic compatibility (EMC). Interference, affecting the reliable operation of the components on the large current loop.

Summary of the invention

Embodiments of the present invention provide a current transformer, a current detecting circuit, and a detecting method, to reduce d,

The layout of the PCB takes up space while reducing the distributed inductance.

In order to achieve the above object, embodiments of the present invention use the following technical solutions:

An embodiment of the present invention provides a current transformer, the current transformer includes a hollow magnetic core, and the hollow magnetic core is used to set a current-carrying conductor to be detected in a circuit to be detected; The central axis of the hollow magnetic core is parallel to the side wall of the hollow magnetic core, and the coil is led out with two access ends, and the two access ends are used for electrical access. Detection signal output circuit.

Another aspect of the present invention provides a current detecting circuit, including a circuit to be detected, a current transformer, and a detection signal output circuit, wherein the current transformer includes a hollow magnetic core along a core of the hollow The direction parallel to the central axis is wound on the side wall of the hollow core, and the coil is led out with two access ends through which the current-carrying conductor to be detected is to be detected. In the hollow magnetic core, the detection signal output circuit is electrically connected to the two access terminals.

Still another aspect of an embodiment of the present invention provides a current detecting method using the current detecting circuit, the method comprising:

Passing the current-carrying conductor to be detected in the loop to be detected through the hollow core of the current transformer, and electrically connecting one end of the detection signal output circuit to one of the two access terminals of the current transformer The other end of the detection signal output circuit is electrically connected to the other of the two access terminals; measuring the current on the detection signal output circuit;

The current on the current-carrying conductor to be detected in the loop to be detected is determined based on the current on the detection signal output circuit.

The current transformer, the current detecting circuit and the detecting method provided by the embodiments of the present invention, because the current transformer comprises a hollow magnetic core, the current-carrying conductor to be detected in the circuit to be detected can be passed through the hollow magnetic core Further, a coil is wound on a sidewall of the hollow core in a direction parallel to a central axis of the hollow core, the coil having two access ends, the two Access terminal Accessing a detection signal output circuit such that when a current flows through the current-carrying conductor, a magnetic field can be induced in the hollow magnetic core, and the induced magnetic field can generate an induced current in the coil. The current-carrying conductor can be used as a primary winding in a current transformer, and the coil can be used as a secondary winding in a current transformer, such that a current in a detection signal output circuit electrically connected to the coil is obtained by measurement, The current in the current carrying conductor to be detected in the loop to be tested can be determined. In various embodiments of the present invention, since the current-carrying conductor to be detected in the loop to be detected serves as a primary winding, it is not necessary to fabricate a special primary winding in the current transformer, so that a large printed circuit is not occupied. The layout area of the board PCB, thereby increasing the power density of the electrical device. At the same time, when the current transformer is connected to the circuit to be detected, the distributed inductance of the circuit to be detected is not increased, so that the voltage spike is not caused, and EMC interference is not caused, and the circuit to be detected is not affected. Reliable operation of components. DRAWINGS

1 is a schematic structural view of a current transformer in the prior art;

2 is a schematic structural view of a current transformer according to an embodiment of the present invention;

3 is a schematic diagram of a current circuit to be detected connected to a current transformer according to an embodiment of the present invention; FIG. 4a is a schematic diagram of a current detecting circuit according to an embodiment of the present invention;

4b is a schematic diagram of another current detecting circuit according to an embodiment of the present invention;

Figure 5a is a detailed schematic diagram of the current detecting circuit of the embodiment shown in Figure 4a;

FIG. 5b is another detailed schematic diagram of the current detecting circuit in the embodiment shown in FIG. 4a;

FIG. 6 is a schematic diagram of a current detecting method according to an embodiment of the present invention.

Reference mark:

11-primary winding 12-secondary winding 1-hollow core 2-coil

3--access terminal 4-other access terminal 5-current carrying conductor

41-to-be-tested circuit 42-current transformer 43-detection signal output circuit

431-Sense Resistor 432- Ammeter 433-Voltage Meter

detailed description

Current transformer, current detecting circuit and detecting method in embodiment of the present invention with reference to the accompanying drawings Carry out a detailed description.

It should be understood that the described embodiments are only a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

As shown in FIG. 2, it is a specific embodiment of the current transformer of the present invention. In this embodiment, the current transformer includes a hollow magnetic core 1 for arranging a current-carrying conductor to be detected in the circuit to be detected (such as the current-carrying conductor 5 in FIG. 3); A coil 2 is wound on a side wall of the hollow core 1 in a direction parallel to a central axis of the hollow core 1, the coil 2 having two access ends, the two connections The ingress includes an access terminal 3 and another access terminal 4, and the two access terminals 3 and 4 are used to electrically access the detection signal output circuit.

In the current transformer provided by the embodiment of the present invention, since the current transformer includes a hollow magnetic core 1, the current-carrying conductor to be detected in the circuit to be detected can be passed through the hollow magnetic core 1; The hollow magnetic core 1 has a central axis parallel to the side wall of the hollow core 1 wound with a coil 2, and the coil 2 leads to two access ends 3 and 4, the two access ends Electrically detecting the signal output circuit such that when a current flows through the current-carrying conductor, a magnetic field can be induced in the hollow core 1, and the induced magnetic field can generate an induced current in the coil 2, thereby The current-carrying conductor can be used as a primary winding in a current transformer, and the coil 2 can be used as a secondary winding in a current transformer, so that the current in the detection signal output circuit electrically connected to the coil can be obtained by measurement, that is, The current in the current carrying conductor to be detected in the loop to be tested is determined. In various embodiments of the present invention, since the current-carrying conductor to be detected in the loop to be detected serves as a primary winding, it is not necessary to fabricate a power density of the electrical device in the current transformer. At the same time, when the current transformer is connected to the loop to be detected, the distributed inductance of the loop to be detected is not increased, so that the voltage spike is not caused, and EMC interference is not caused, and the loops to be detected are not affected. Reliable operation of components.

After the current-carrying conductor (such as the current-carrying conductor 5 in FIG. 3) to be detected in the hollow magnetic core 1 is sheathed, the hollow magnetic core 1 can be electrically connected in a coupled manner. Detection circuit Medium. In this embodiment, as shown in FIG. 3, the current-carrying conductor 5 in the circuit to be detected is disposed in the hollow core 1, that is, there is no direct contact between the circuit to be detected and the core 1, but There is an electrical connection. When a current flows through the current-carrying conductor 5, a magnetic field can be induced in the hollow core 1, and the induced magnetic field can generate an induced current in the coil 2. In addition, the coil 2 leads to two access terminals 3 and 4, which are connected to a detection signal output circuit, and the current in the detection signal output circuit is the induced current in the coil 2.

Therefore, although the coil used as the primary winding is not provided in the structure of the current transformer itself, the current-carrying conductor 5 which is bored in the hollow core 1 functions as the primary winding in the current transformer. At this time, the number of turns of the primary winding is related to the manner in which the current-carrying conductor 5 is bored in the hollow core 1, and the number of turns of the primary winding will be described in detail below. It is assumed that the number of turns of the primary winding in the current transformer is N1, the current in the primary winding is II (ie, the current in the loop to be detected is II), the number of turns of the secondary winding is N2, and the current in the secondary winding It is 12 (that is, the current in the detection signal output circuit is 12). According to the principle of the current transformer, I1N1=I2N2, so the ratio of the current in the detection signal output circuit to the current in the circuit to be detected is I2: I1= N1 : N2. Normally, since N2 is much larger than N1, the large current II in the loop to be detected is scaled down to a small current 12 in the detection signal output circuit to reduce the loss and facilitate the measurement of the current 12. In a special case, the number of turns of the primary winding may be 1, and the ratio of the current 12 in the detection signal output circuit to the current II in the circuit to be detected may be 1:N2.

Embodiments of the present invention also provide a current detecting circuit using the above current transformer. As shown in FIG. 4 (including FIG. 4a and FIG. 4b), the current detecting circuit includes a circuit to be detected 41, a current transformer 42 and a detection signal output circuit 43, and the current transformer 41 includes a hollow core 1 along which A central axis of the hollow core 1 (the central axis is shown by a broken line in FIGS. 4a and 4b) is wound in a direction parallel to the side wall of the hollow core 1 with a coil 2, and the coil 2 is taken out There are two access terminals, and the two access terminals include an access terminal 3 and another access terminal 4. The current-carrying conductor 5 to be detected in the circuit to be detected 41 is inserted through the hollow core 1 for detection. The signal output circuit 43 is electrically connected to the two access terminals 3 and 4. The current detecting circuit provided by the embodiment of the present invention, because the current transformer 42 includes a hollow magnetic core 1, the current-carrying conductor 5 to be detected in the circuit to be detected 41 can be disposed in the hollow magnetic core 1; A coil 2 is wound on a side wall of the hollow core 1 in a direction parallel to a central axis of the hollow core 1, and the coil 2 leads to two access ends 3 and 4, the two The access terminal electrically accesses the detection signal output circuit 43 such that when a current flows through the current-carrying conductor 5, a magnetic field can be induced in the hollow core 1, and the induced magnetic field can generate an induced current in the coil 2. Therefore, the current-carrying conductor 5 can be used as the primary winding of the current transformer 42, and the coil 2 can be used as the secondary winding in the current transformer 42, so that the current in the detection signal output circuit 43 electrically connected to the coil 2 is obtained by measurement. , to determine the current in the current-carrying conductor to be detected in the loop to be tested. In various embodiments of the present invention, since the current-carrying conductor 5 to be detected in the circuit to be detected 41 serves as a primary winding, it is not necessary to fabricate a special primary winding in the current transformer 42, so that it does not occupy a large printing. The layout area of the board PCB, thereby increasing the power density of the electrical device. At the same time, when the current transformer 42 is serially connected to the circuit to be detected 41, the distributed inductance of the circuit to be detected 41 is not increased, so that voltage spikes are not caused, and EMC interference is not caused, and the to-be-detected is not affected. Reliable operation of the components on circuit 41.

As can be seen from the above description, the current-carrying conductor 5 penetrating in the hollow core 1 can be used as the primary winding of the current transformer 42, and the number of turns of the primary winding and the current-carrying conductor 5 are in the hollow core 1. The way to wear it. Wherein, the current-carrying conductor 5 is disposed in the hollow magnetic core 1 and includes a plurality of laying manners, for example, as shown in FIG. 4a, one of which may be one way of passing one end of the current-carrying conductor 5 from the hollow The magnetic core 1 has an opening at one end and directly protrudes from the opening of the other end; or as shown in FIG. 4b, another way of penetrating may be to take one end of the current-carrying conductor 5 from the hollow The magnetic core 1 protrudes from one end opening, and the hollow magnetic core is wound from the one end opening to the other end opening at least one turn and then protrudes from the other end opening.

When one end of the current-carrying conductor 5 is projected from the one end opening of the hollow core 1 and directly protrudes from the other end opening, the number of turns of the primary winding is 1 at this time, and the current 12 in the signal output circuit 43 is detected. The ratio of the current II to the circuit to be detected 41 is 1: N2; when one end of the current-carrying conductor 5 is inserted from the opening of one end of the hollow core 1, and the hollow is wound from the opening of one end to the opening of the other end. Core 1 at least When extending from the other end opening after one turn, the number of turns of the current-carrying conductor 5 wound around the hollow core is increased by one, which is the number of turns of the primary winding. For example, when the current-carrying conductor 5 protrudes from one end opening of the hollow core 1, and the hollow core N is wound from the one end opening to the other end opening (as shown in FIG. 4b) After extending from the other end opening, the number of turns of the primary winding is N+1. For example, the number of turns of the primary winding in FIG. 4b is 2, and the ratio of the current in the detection signal output circuit 43 to the current in the circuit to be detected is Is (N+1): N2.

The current carrying conductor 5 includes a wire or a switch pin. When the current-carrying conductor 5 is a wire, the manner of the wire in the hollow core 1 can be determined according to the ratio of the current in the desired output circuit to the current in the circuit to be detected. If the ratio is relatively large, then The wire is wound in the hollow core 1 by a larger number of turns. Otherwise, if the ratio is relatively small, the number of turns of the wire wound in the hollow core 1 is less. When the current-carrying conductor 5 is a switch-tube pin, the current-carrying conductor 5 is disposed in the hollow core 1 by inserting the hollow core 1 on the pin of the switch tube. The pin of the switch tube in the hollow core 1 protrudes from the opening of one end of the hollow core 1 and directly protrudes from the opening of the other end, so the number of turns of the primary winding is 1, and the detection signal output circuit 43 The ratio of the current to the current in the loop to be detected 42 is 1:N2.

The current in the detection signal output circuit 43 can be measured by various methods such as detecting the current by the Hall sensor, and since the current in the detection signal output circuit 43 is relatively small, the resistance detection current method can be preferably used. The detection current has a low cost, a simple circuit, and a fast response, and at this time, the current in the detection signal output circuit 43 is relatively small, so that no large loss is generated. The resistance detecting circuit includes a detecting resistor and an ammeter connected in series, and the second resistance detecting circuit includes a detecting resistor and a voltmeter connected in parallel.

As shown in FIG. 5a, the detection signal output circuit 43 includes a detection resistor 431 and an ammeter 432 connected in series, and a detection resistor 431 is connected to one of the two access terminals, the ammeter 432 and the two The other access terminal 4 of the access terminals is connected. Therefore, when the current-carrying conductor 5 is bored in the hollow core 1, an induced current is generated in the coil 2, and is transmitted to the two access terminals 3 and 4 to The detection signal output circuit 43, at this time, the display value on the ammeter 432 is the current value in the detection signal output circuit 43. In addition, in general, a common current transformer is connected in an alternating current system, such as a 50 Hz alternating current provided by a power supply company, so the current meter should be an alternating current meter, and the display value on the alternating current meter is the detection signal output. The rms current in the circuit.

As shown in Fig. 5b, the detection signal output circuit 43 includes a detection resistor 431 and a voltage meter 433 connected in parallel, and both ends of the detection resistor 431 are correspondingly connected to the two access terminals 3 and 4. Therefore, when the current-carrying conductor 5 is bored in the hollow core 1, an induced current is generated in the coil 2, and is transmitted to the detection signal output circuit 43 through the two access terminals 3 and 4, at which time the voltmeter 433 The display value on the upper end is the terminal voltage across the detecting resistor 431. According to Ohm's law, the value displayed by the voltmeter 433 divided by the resistance of the detecting resistor 431 can obtain the current value flowing through the detecting resistor 431, that is, the The current value in the signal output circuit 43 is detected.

As shown in FIG. 6, the embodiment of the present invention further provides a current detecting method using the current detecting circuit, which includes:

5101, the current-carrying conductor 5 to be detected in the circuit to be detected 41 is disposed in the hollow core 1 of the current transformer 42, and one end of the detection signal output circuit 43 and the two access terminals of the current transformer 42 are connected. One of the access terminals 3 is electrically connected, and the other end of the detection signal output circuit 43 is electrically connected to the other of the two access terminals 4;

5102, measuring a current on the detection signal output circuit 43;

5103. Determine a current on the current-carrying conductor 5 to be detected in the circuit to be detected 41 according to the current on the detection signal output circuit 43.

The current detecting method provided by the embodiment of the present invention firstly passes the current-carrying conductor 5 to be detected in the circuit to be detected 41 through the hollow core 1 of the current transformer 42 according to the required primary winding and the second The winding turns ratio can reasonably select the way in which the current-carrying conductor 5 is placed in the hollow core 1 of the current transformer 42. And the detection signal output circuit 43 is connected to the two access terminals 3 and 4 of the current transformer 42 so that the circuit connection of the entire current detecting circuit is completed. Then, the current on the detection signal output circuit 43 is measured, in the embodiment of the present invention, according to the detection signal output circuit 43 The reading of the ammeter 432 or the voltmeter 433 can be directly obtained or converted by Ohm's law to obtain the current on the signal output circuit 43, that is, the induced current generated in the secondary winding. Finally, the current on the current-carrying conductor 5 to be detected in the circuit to be detected 41 can be derived forward by the current on the detection signal output circuit 43.

In step S103, determining the current on the current-carrying conductor 5 to be detected in the circuit to be detected 41 according to the current on the detection signal output circuit 43 is specifically:

First, the ratio of the number of turns of the coil 2 in the access detection signal output circuit 43 to the number of current-carrying conductors in the circuit to be detected 41 is determined;

Then, it is determined that the product of the current on the detection signal output circuit 43 and the ratio is the current on the current-carrying conductor 5 to be detected in the circuit 41 to be detected.

The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. It should be covered by the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the claims.

Claims

Claim

A current transformer, comprising: a hollow magnetic core, the hollow magnetic core is used for sheathing a current-carrying conductor to be detected in a circuit to be detected; along a center of the core with the hollow core The direction parallel to the axis is wound with a coil on the side wall of the hollow core, and the coil leads to two access terminals for electrically connecting the detection signal output circuit.

2. The current transformer according to claim 1, wherein after the current-carrying conductor to be detected in the loop to be detected is placed in the hollow core, the hollow core is electrically coupled Accessing the loop to be detected.

3. A current detecting circuit, comprising: a circuit to be detected, a current transformer and a detection signal output circuit, the current transformer comprising a hollow magnetic core, parallel to a central axis of the hollow core a direction in which a coil is wound on a sidewall of the hollow core, the coil leads to two access ends, and a current-carrying conductor to be detected in the circuit to be detected is passed through the hollow core The detection signal output circuit is electrically connected to the two access terminals.

4. The current detecting circuit according to claim 3, wherein

One end of the current-carrying conductor extends from one end opening of the hollow magnetic core and directly protrudes from the other end opening; or

One end of the current-carrying conductor extends from one end opening of the hollow magnetic core, and the side wall of the hollow magnetic core is wound from the one end opening to the other end opening at least one turn from the other end Extend from the opening.

The current detecting circuit according to claim 3 or 4, wherein the current carrying conductor comprises a wire or a switch pin.

The current detecting circuit according to claim 3 or 4, wherein the detecting signal output circuit comprises a detecting resistor and an ammeter connected in series, and the detecting resistor is connected to one of the two access terminals Connected to the end, the ammeter is connected to the other of the two access terminals; or The detection signal output circuit includes a detection resistor and a voltage meter connected in parallel, and two ends of the detection resistor are correspondingly connected to the two access terminals.

7. The current detecting circuit according to claim 6, wherein the current meter is an alternating current meter.

A current detecting method using the current detecting circuit according to any one of claims 3-7, wherein the method comprises:

The current detecting method according to claim 8, wherein the determining the current on the current-carrying conductor to be detected in the circuit to be detected according to the current on the detecting signal output circuit comprises:

Determining a ratio of the number of turns of the coil in the output signal of the access detection signal to the number of current-carrying conductors in the loop to be detected;

It is determined that the product of the current on the detection signal output circuit and the ratio is the current on the current carrying conductor to be detected in the loop to be detected.