Wide range isolated current transformer

Abstract

The utility model discloses a wide range isolated current transformer sets up the current sampling circuit who includes voltage sampling module, and the parallel first section current sampling module, second section current sampling module and third section current sampling module, through magnetic ring, induction coil and voltage sampling module to the primary side main voltage carries out the proportional voltage reduction, then is input to the current detection circuit and handles, and the corresponding current grade of output, and the control circuit is according to the further switching current sampling circuit's sampling mode of specific current grade, through the combination parallel of first section current sampling module, second section current sampling module and third section current sampling module each other, thereby provided the great current measurement range, and need not increase the winding turns and switching coil and measure, satisfy the full range measurement demand of charging pile to small current to big current charging.

Description

Technical Field

[0001] This utility model relates to the field of current transformer technology, and in particular to a wide-range isolated current transformer. Background Technology

[0002] To address the current measurement needs of new energy vehicle charging piles, existing isolated current transformers suffer from a single measurement range: high-range models can meet the requirements of large current measurement, but have no response to small current; low-range models can only detect small current and are not compatible with large current scenarios.

[0003] In actual charging, when the power battery is at a low charge level, the charging pile needs to output a large current to achieve rapid energy replenishment. As the charging process progresses and the battery charge continues to increase, the charging current will gradually decrease. In this dynamic scenario, the range limitation of traditional current transformers becomes apparent. They not only struggle to cover the current at all stages, but also cannot effectively measure small currents below 500mA. Utility Model Content

[0004] To address the aforementioned problems, this utility model proposes a wide-range isolated current transformer, which mainly solves the problems in the background technology.

[0005] To solve the above-mentioned technical problems, the technical solution of this utility model is as follows:

[0006] A wide-range isolated current transformer, comprising:

[0007] A magnetic ring, and an induction coil wound around the magnetic ring;

[0008] The current sampling circuit includes a voltage sampling module connected to an induction coil, and a first current sampling module, a second current sampling module, and a third current sampling module connected in parallel. The controlled terminals of the second current sampling module and the third current sampling module are respectively provided with a first field-effect transistor and a second field-effect transistor.

[0009] A current detection circuit, whose voltage signal input terminal is connected to the output terminal of the voltage sampling module, is used to receive the voltage signal transmitted by the voltage sampling module and generate a first current signal;

[0010] The control circuit has its input terminal connected to the voltage output terminal of the current detection circuit. It generates a control signal based on the first current signal to control the on / off state of the first field-effect transistor and the second field-effect transistor. It switches the operating mode of the current sampling circuit to either the first current sampling module operating alone, or the first current sampling module and the second current sampling module operating in parallel, or the first current sampling module and the third current sampling module operating in parallel. The second current signal output by the current sampling circuit is processed by the current detection circuit and then enters the control circuit.

[0011] A communication circuit, the signal input terminal of which is connected to the current signal output terminal of the control circuit, is used to output the current signal to an external device.

[0012] In some implementations, the current detection circuit is a BL094 current measurement chip.

[0013] In some implementations, the control circuit is a CX32L003F9Q6 microcontroller.

[0014] In some embodiments, the communication circuit is an RS485 communication circuit.

[0015] In some embodiments, a power supply module is also included for supplying power to the control circuit and the communication circuit.

[0016] In some embodiments, the input terminal of the current sampling circuit includes the induction coil and the transient suppression tube connected in parallel. One end of the induction coil is grounded, and the other end is connected in sequence to the voltage signal input terminal of the voltage sampling module and the current detection circuit. The transient suppression tube is followed by the first current sampling module, the second current sampling module and the third current sampling module connected in parallel, as well as a positive output terminal and a reverse output terminal.

[0017] In some implementations, the voltage sampling module further includes a fourth resistor and a first capacitor connected in sequence.

[0018] In some embodiments, the first current sampling module includes a first resistor, the second current sampling module includes a second resistor, and the third current sampling module includes a third resistor. The first resistor, the second resistor, and the third resistor are connected in parallel. The non-inverting terminals share a fifth resistor and a second capacitor, and the inverting terminals share a sixth resistor and a third capacitor. One end of the second resistor is connected to the first field-effect transistor, the gate of the first field-effect transistor is connected to the control circuit via a seventh resistor, one end of the third resistor is connected to the second field-effect transistor, and the gate of the second field-effect transistor is connected to the control circuit via an eighth resistor.

[0019] In some embodiments, the resistance values ​​of the first resistor, the second resistor, and the third resistor are 200R, 33R, and 0.3R, respectively.

[0020] The beneficial effects of this utility model are as follows: A current sampling circuit is set up, which includes a voltage sampling module and a first-stage current sampling module, a second-stage current sampling module, and a third-stage current sampling module connected in parallel. The primary main voltage is proportionally stepped down by a magnetic ring, an induction coil, and a voltage sampling module, and then input to a current detection circuit for processing, outputting the corresponding current level. The control circuit further switches the sampling mode of the current sampling circuit according to the specific current level. By combining the first-stage current sampling module, the second-stage current sampling module, and the third-stage current sampling module in parallel, a very large current measurement range is provided, and there is no need to increase the number of winding turns or switch coils for measurement, which meets the full-range metering requirements of charging piles for charging from small current to large current. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the architecture of a wide-range isolated current transformer disclosed in an embodiment of the present utility model;

[0022] Figure 2 This is a schematic diagram of the current sampling circuit disclosed in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this utility model clearer and more explicit, the content of this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining this utility model and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts related to this utility model are shown in the accompanying drawings, not all of them.

[0024] This embodiment proposes a wide-range isolated current transformer, such as... Figure 1 As shown, it includes:

[0025] Magnetic ring 100, and induction coil wound on magnetic ring 100;

[0026] The current sampling circuit 200 includes a voltage sampling module connected to an induction coil, and a first current sampling module, a second current sampling module, and a third current sampling module connected in parallel. The controlled terminals of the second current sampling module and the third current sampling module are respectively provided with a first field-effect transistor and a second field-effect transistor.

[0027] The current detection circuit 300 has its voltage signal input terminal connected to the output terminal of the voltage sampling module. It is used to receive the voltage signal transmitted by the voltage sampling module and generate a first current signal. It should be noted that current detection is usually achieved by measuring the voltage signal related to the current. The relevant prior art will not be explained further.

[0028] The control circuit 400 has its input terminal connected to the voltage output terminal of the current detection circuit 300. It generates a control signal based on the first current signal to control the on / off state of the first field-effect transistor and the second field-effect transistor. It switches the working mode of the current sampling circuit 200 to either the first current sampling module operating alone, or the first current sampling module and the second current sampling module operating in parallel, or the first current sampling module and the third current sampling module operating in parallel. The second current signal output by the current sampling circuit 200 is processed by the current detection circuit 300 and then enters the control circuit 400.

[0029] The communication circuit 500 has its signal input terminal connected to the current signal output terminal of the control circuit 400, and is used to output the current signal to external devices.

[0030] In this scheme, a current sampling circuit 200 is set up, which includes a voltage sampling module and three parallel current sampling modules: a first current sampling module, a second current sampling module, and a third current sampling module. The voltage is proportionally stepped down by the magnetic ring 100, the induction coil, and the primary voltage of the voltage sampling module, and then input to the current detection circuit 300 for processing, outputting the corresponding current level. The control circuit 400 further switches the sampling mode of the current sampling circuit 200 according to the specific current level. By combining the first current sampling module, the second current sampling module, and the third current sampling module in parallel, a very large current measurement range is provided, and there is no need to increase the number of winding turns or switch coils for measurement, which meets the full-range metering requirements of the charging pile for charging from small current to large current.

[0031] Optionally, the current detection circuit 300 uses the BL094 current measurement chip.

[0032] Optionally, the control circuit 400 is a CX32L003F9Q6 microcontroller.

[0033] Optionally, the communication circuit 500 is an RS485 communication circuit 500.

[0034] Optionally, a power supply module 600 is also included to power the control circuit 400 and the communication circuit 500.

[0035] In one example, such as Figure 2 As shown, the input of the current sampling circuit 200 includes a parallel induction coil L1 and a transient suppression transistor D10. The transient suppression transistor D10 prevents the surge voltage generated on the primary side from damaging the subsequent stage. One end of the induction coil L1 is grounded, and the other end is connected sequentially to the voltage signal input terminals of the voltage sampling module and the current detection circuit 300. Specifically, the voltage sampling module formed by the induction coil L1 uses resistor R4 to perform a voltage reduction function; the voltage across the induction coil L1 is sent to the BL094 chip in the subsequent stage via R4. The stage following the transient suppression transistor D10 is connected to a first-stage current sampling module, a second-stage current sampling module, and a third-stage current sampling module connected in parallel, as well as a non-inverting output terminal IP_A and an inverting output terminal IN_A.

[0036] The voltage sampling module also includes a fourth resistor R4 and a first capacitor C5 connected in sequence. The fourth resistor R4 and the first capacitor C5 form an RC low-pass filter circuit to remove high-frequency interference signals.

[0037] The first current sampling module includes a first resistor R56. Specifically, the first resistor R56 is a first current sampling resistor 200R 0603, used to sample currents in the range of 5mA to 150mA.

[0038] The second current sampling module includes a second resistor R1, one end of which is connected to the first field-effect transistor Q2. The gate of the first field-effect transistor Q2 is connected to the control circuit 400 via a seventh resistor R55. Specifically, the second resistor R1 is a second-stage current sampling resistor 33R 0603, used to sample currents in the range of 150mA to 1000mA. The first field-effect transistor Q2 is an N-channel MOSFET used to turn on the second-stage current sampling resistor. The seventh resistor R55 is the drive resistor for the gate (G) of Q2.

[0039] The third-stage current sampling module includes a third resistor R52, one end of which is connected to the second field-effect transistor Q1. The gate of the second field-effect transistor Q1 is connected to the control circuit 400 via an eighth resistor R53. The third resistor R52 is a 0.3R 2512 current sampling resistor used to sample currents in the range of 1000mA to 100A. The second field-effect transistor Q1 is an N-channel MOSFET used to turn on the third-stage current sampling resistor. The eighth resistor R53 is the drive resistor for the gate (G) of Q1.

[0040] The first resistor R5, the second resistor R1, and the third resistor R52 are connected in parallel. The non-inverting input shares the fifth resistor R2 and the second capacitor C3, while the inverting input shares the sixth resistor R3 and the third capacitor C4. The fifth resistor R2 and the second capacitor C3 form an RC low-pass filter to low-pass filter the voltage at the magnetic ring induction coil terminal. The filtered signal is then sent to the subsequent BL094 for positive current detection. The sixth resistor R3 and the third capacitor C4 form an RC low-pass filter to low-pass filter the voltage at the magnetic ring induction coil terminal. The filtered signal is then sent to the subsequent BL094 for negative current detection.

[0041] The following example illustrates the working principle of the current sampling circuit 200:

[0042] First segment of current sampling:

[0043] When the primary current is less than 150mA, the control circuit 400 determines this and causes CH1 and CH2 to output low levels, which in turn turn off the first field-effect transistor Q2 and the second field-effect transistor Q1 via the seventh resistor R55 and the eighth resistor R53, respectively. The second resistor R1 and the third resistor R52 are disconnected from one end of the induction coil L1, preventing current from flowing through them. At this time, the voltage across the induction coil L1 passes entirely through the first resistor R56. The voltage across the first resistor R56 reflects the magnitude of the secondary induced current. This voltage is then low-pass filtered by the fifth resistor R2 and the second capacitor C3 before being sent to the subsequent BL094 chip for current detection.

[0044] Second segment current sampling:

[0045] When the primary current is greater than 150mA and less than 1000mA, the control circuit 400 determines this and sets CH1 to output a high level. This high level drives the first field-effect transistor Q2 to turn on via resistor R55 (the seventh resistor). This causes CH2 to output a low level, which then drives the second field-effect transistor Q1 to turn off via resistor R53 (the eighth resistor). At this time, the second resistor R1 and the first resistor R56 are connected in parallel across the induction coil L1. The third resistor R52 is disconnected from one end of the induction coil L1, preventing current from flowing through it. The voltage across the induction coil L1 then flows entirely through the second resistor R1 and the first resistor R56. The voltage across these two resistors reflects the magnitude of the secondary induced current. This voltage is low-pass filtered by resistor R2 (the fifth resistor) and capacitor C3 and then sent to the subsequent BL094 chip for current detection. Because the resistance of the second resistor R1 is 33Ω and the resistance of the first resistor R56 is 200Ω, most of the current flows through the first resistor R56. Therefore, the current measured in this operating mode is larger than the current measured in the first stage.

[0046] Third segment current sampling:

[0047] When the primary current is greater than 1000mA but less than 100A, the control circuit 400 determines this and causes CH1 to output a low level. This, through the seventh resistor R55, drives the first field-effect transistor Q2 to turn off, causing CH2 to output a high level. This, through the eighth resistor R53, drives Q1 to turn on. At this time, the third resistor R52 and the first resistor R56 are connected in parallel across the induction coil. Resistor R1 is disconnected from one end of the induction coil L1, preventing current from flowing through the second resistor R1. The voltage across the induction coil L1 then flows entirely through the third resistor R52 and the first resistor R56. The voltage generated across the third resistor R52 and the first resistor R56 reflects the magnitude of the secondary induced current. This voltage is low-pass filtered by the fifth resistor R2 and the second capacitor C3 and then sent to the subsequent BL094 chip for current detection. Because the resistance of the third resistor R52 is 0.3Ω and the resistance of the first resistor R56 is 200Ω, most of the current flows through the third resistor R52. Therefore, the current measured in this operating mode is much larger than the current measured in the second stage.

[0048] In summary, this solution achieves different levels of current measurement by controlling the parallel connection of the first resistor R5, the second resistor R1, and the third resistor R52 through the control circuit 400.

[0049] The above embodiments are merely illustrative of the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All equivalent changes or modifications made based on the substance of the content of this utility model should be covered within the scope of protection of this utility model.

Claims

1. A wide-range isolated current transformer, characterized in that, include: A magnetic ring, and an induction coil wound around the magnetic ring; The current sampling circuit includes a voltage sampling module connected to an induction coil, and a first current sampling module, a second current sampling module, and a third current sampling module connected in parallel. The controlled terminals of the second current sampling module and the third current sampling module are respectively provided with a first field-effect transistor and a second field-effect transistor. A current detection circuit, whose voltage signal input terminal is connected to the output terminal of the voltage sampling module, is used to receive the voltage signal transmitted by the voltage sampling module and generate a first current signal; The control circuit has its input terminal connected to the voltage output terminal of the current detection circuit. It generates a control signal based on the first current signal to control the on / off state of the first field-effect transistor and the second field-effect transistor. It switches the operating mode of the current sampling circuit to either the first current sampling module operating alone, or the first current sampling module and the second current sampling module operating in parallel, or the first current sampling module and the third current sampling module operating in parallel. The second current signal output by the current sampling circuit is processed by the current detection circuit and then enters the control circuit. A communication circuit, the signal input terminal of which is connected to the current signal output terminal of the control circuit, is used to output the current signal to an external device.

2. The wide-range isolated current transformer as described in claim 1, characterized in that, The current detection circuit is a BL094 current measurement chip.

3. The wide-range isolated current transformer as described in claim 1, characterized in that, The control circuit is a CX32L003F9Q6 microcontroller.

4. The wide-range isolated current transformer as described in claim 1, characterized in that, The communication circuit is an RS485 communication circuit.

5. The wide-range isolated current transformer as described in claim 1, characterized in that, It also includes a power module for supplying power to the control circuit and the communication circuit.

6. The wide-range isolated current transformer as described in claim 1, characterized in that, The input terminal of the current sampling circuit includes the induction coil and the transient suppression tube connected in parallel. One end of the induction coil is grounded, and the other end is connected in sequence to the voltage signal input terminal of the voltage sampling module and the current detection circuit. The transient suppression tube is followed by the first current sampling module, the second current sampling module and the third current sampling module connected in parallel, as well as a positive output terminal and a reverse output terminal.

7. The wide-range isolated current transformer as described in claim 6, characterized in that, The voltage sampling module also includes a fourth resistor and a first capacitor connected in sequence.

8. The wide-range isolated current transformer as described in claim 7, characterized in that, The first current sampling module includes a first resistor, the second current sampling module includes a second resistor, and the third current sampling module includes a third resistor. The first resistor, the second resistor, and the third resistor are connected in parallel. The non-inverting terminals share a fifth resistor and a second capacitor, and the inverting terminals share a sixth resistor and a third capacitor. One end of the second resistor is connected to the first field-effect transistor, and the gate of the first field-effect transistor is connected to the control circuit via a seventh resistor. One end of the third resistor is connected to the second field-effect transistor, and the gate of the second field-effect transistor is connected to the control circuit via an eighth resistor.

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