CN211266785U - Current transformer circuit - Google Patents

Abstract

The present application relates to a power taking circuit of a current transformer, belonging to the technical field of current acquisition of a current transformer, including: a rectifier circuit, the AC side of which is used to connect the output end of the current transformer; an energy conversion circuit, including an isolation transformer, a switch A power supply chip, in which the primary side of the isolation transformer, the input and output terminals of the switching power supply chip, and the DC side of the rectifier circuit are connected in series to form a series loop, and the secondary side of the isolation transformer is connected to a power-taking capacitor after rectification; an output protection circuit, the output protection The circuit sampling is connected to the power-taking capacitor. When the voltage of the power-taking capacitor exceeds the limit, the enabling end of the switching power supply chip is blocked; the constant current source circuit, the input end of the constant current source circuit is connected to the DC side of the rectifier circuit, and the constant current source circuit The output terminal of the capacitor is connected to the startup capacitor for charging the startup capacitor. The power taking circuit of the utility model makes the power taking of the output end of the current transformer more stable and reliable, the circuit is simple, the use is convenient, and the manufacturing cost is low.

Description

Current transformer circuit

technical field

The present application relates to a power taking circuit of a current transformer, and belongs to the technical field of current acquisition of a current transformer.

Background technique

The current transformer to take power is mainly to convert the current source output by the current transformer into a stable voltage source to provide the required stable power supply for the work of various devices in the power system. In the realization of this power conversion technology, the usual problem is: due to the large current change of the primary side of the current transformer, the current change range of the secondary side output of the current transformer is wide, and the output current is unstable. Therefore, This type of power supply circuit should be able to withstand a wide input range at the input end.

Utility model content

The purpose of the present application is to provide a power taking circuit of a current transformer, which is used to solve the problem of unstable output voltage of the power taking circuit of a current transformer in the prior art.

The power taking circuit of a current transformer of the present application adopts the following technical solutions:

Rectifier circuit, the AC side of the rectifier circuit is used to connect the output end of the current transformer;

The energy conversion circuit includes an isolation transformer and a switching power supply chip, wherein the primary side of the isolation transformer, the input and output terminals of the switching power supply chip, and the DC side of the rectifier circuit are connected in series to form a series loop, and the secondary side of the isolation transformer is connected to obtain electricity after rectification capacitance;

an output protection circuit, the output protection circuit is sampled and connected to a power-taking capacitor, and when the voltage of the power-taking capacitor exceeds the limit, the enabling terminal of the switching power supply chip is blocked, and the power supply terminal of the switching power supply is connected with a starting capacitor;

A constant current source circuit, the input end of the constant current source circuit is connected to the DC side of the rectifier circuit, and the output end of the constant current source circuit is connected to the starting capacitor for charging the starting capacitor.

The beneficial effects of the above technical solutions are:

The power taking circuit of the utility model rectifies the alternating current at the output end of the current transformer into direct current through the rectification circuit, and converts the current source (ie direct current) with a wide variation range into voltage through the switching power supply chip and the isolation transformer in the energy conversion circuit Since the output protection circuit is sampling and connected to the power-taking capacitor, when the output current of the current transformer is too large, the output protection circuit detects that the voltage of the power-taking capacitor exceeds the limit, and can block the enable terminal of the switching power supply chip, so that the switching power supply chip does not work. , so as to prevent the voltage of the capacitor from being too large and play a role in stabilizing the output voltage source.

In addition, the constant current source in the power taking circuit takes power from the DC side of the rectifier circuit to charge the startup capacitor of the switching power supply chip, which ensures the reliable operation of the switching power supply chip and avoids causing the current transformer output current to be small. The switching power supply chip does not work. Compared with the prior art, the power taking circuit of the utility model makes the power taking of the output end of the current transformer more stable and reliable, and has the advantages of simple circuit, convenient use and low manufacturing cost.

In order to realize the protection function of the output protection circuit, the output protection circuit includes an optocoupler, the input of the optocoupler is connected in parallel with the power taking capacitor through a voltage divider circuit, and the output end of the optocoupler is connected to the enabling end of the switching power supply chip. Since the primary side of the optocoupler is connected to the output end of the isolation transformer through a voltage dividing resistor, when the output voltage of the isolation transformer is too large, the voltage of the primary side of the optocoupler is too large, and the secondary side of the optocoupler is turned on, enabling the switching power supply. The terminal is enabled, and then the switching power supply is turned off. Therefore, the optocoupler and the voltage divider circuit cooperate to stabilize the output voltage source.

Preferably, the voltage divider circuit includes a voltage regulator tube and a voltage divider resistor.

In order to provide a stable power supply for the startup capacitor, the constant current source circuit includes:

A first-stage amplifying switch tube and a second-stage amplifying switch tube, wherein a first voltage dividing resistor is arranged in series between the base and the collector of the first-stage amplifying switch tube, and a first voltage divider is arranged in series between the base and the emitter of the second-stage amplifying switch tube A second voltage dividing resistor is provided, the first voltage dividing resistor and the second voltage dividing resistor are connected in series, and the second voltage dividing resistor is used for connecting the DC side of the rectifier circuit;

The emitter of the first-stage amplifying switch tube is connected to the startup capacitor through a third resistor, and the emitter of the first-stage amplifying switch tube is connected in parallel with the collector of the second-stage amplifying switch tube.

In order to prevent inrush current, the above-mentioned power taking circuit also includes:

An anti-surge circuit, which is provided with a transient suppression diode and a varistor in series, the anti-surge circuit is used to connect in parallel with the output end of the current transformer, and the AC side of the anti-surge circuit and the rectifier circuit in parallel.

In order to realize the energy discharge when the current transformer outputs excessive current, the above-mentioned power taking circuit also includes:

The bleeder circuit includes a bleeder switch tube and a discharge element, the bleeder switch tube is connected in parallel with the DC side of the rectifier circuit, and a discharge element is arranged in series between the control end of the bleeder switch tube and the cathode, and the discharge element passes through the stabilizing circuit. A storage capacitor is connected in series with the pressure tube.

Preferably, the discharge element includes a discharge resistor and a discharge capacitor, and the discharge resistor and the discharge capacitor are connected in parallel.

In order to provide a high-voltage freewheeling path when the switching power supply chip is turned off, further, a freewheeling branch is connected in parallel with the secondary side of the isolation transformer, and a freewheeling element is connected in series on the freewheeling branch.

Preferably, the freewheeling element includes a freewheeling diode and a freewheeling resistor, and the freewheeling diode and the freewheeling resistor are connected in series.

In order to ensure a stable power supply for the startup capacitor, the above-mentioned power taking circuit further includes an energy storage capacitor, which is connected in parallel with the DC side of the rectifier circuit, so that the constant current source circuit can take electricity through the energy storage capacitor to charge the startup capacitor .

Description of drawings

FIG. 1 is a circuit diagram of a current transformer of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application, that is, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the application as claimed, but is merely representative of selected embodiments of the application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

It should be noted that relational terms such as the terms "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

The features and properties of the present application will be described in further detail below with reference to the embodiments.

As shown in Figure 1, the power taking circuit of the current transformer includes an anti-surge circuit, a rectifier circuit, a discharge circuit, an energy storage capacitor, an energy conversion circuit, a constant current source circuit and a power taking capacitor. Among them, the anti-surge circuit includes a transient suppression diode TVS1 and a varistor MR1 connected in series, the anti-surge circuit is used to connect in parallel with the output end of the current transformer, and the anti-surge circuit is connected to the rectifier circuit ZL1. The AC side (ie, input port 1 and input port 3 of ZL1) are connected in parallel. An embodiment of the rectifier circuit ZL1 is shown in FIG. 1 , which is a rectifier bridge. As another embodiment, a full-wave rectifier circuit with other topological structures may also be used.

The AC side of the rectifier circuit ZL1 is used to connect the output end of the current transformer CT, and the DC side of the rectifier circuit (ie, the output port 2 and output port 4 of ZL1) is provided with an anti-reverse diode D1 in series, which plays a reverse role. Prevent the backflow of stored energy. The energy storage capacitor C1 is connected in parallel with the DC side of the rectifier circuit ZL1 through the anti-reverse diode D1, and the energy storage capacitor is used to store the amount of DC current, which can meet the DC power demand required by the operation of the subsequent circuit.

The bleeder circuit includes a bleeder switch tube Q3 (preferably a MOSFET tube in this embodiment) and a discharge element. The bleeder switch tube Q3 is connected in parallel with the DC side of the rectifier circuit ZL1, and the control terminal of the bleeder switch tube Q3 is connected in series with the cathode. There is a discharge element, the discharge element includes a discharge resistor R11 and a discharge capacitor C6, the discharge resistor R11 and the discharge capacitor C6 are connected in parallel, and the discharge element is connected in series with the energy storage capacitor C1 through a voltage regulator tube V1.

In the above discharge circuit, when the electrical load is large, the current transformer CT outputs a large current, and when the conduction threshold formed by the voltage regulator tube V1 and the resistor R11 is reached, the voltage regulator tube V1 breaks down and further controls the switch. The tube Q3 is turned on, and the excess energy is discharged by the turned-on switch tube Q3, which protects the voltage of the energy storage capacitor C1 from increasing indefinitely, thereby avoiding the damage of the post-stage circuit by overvoltage. In the bleeder circuit, the start value and return value of the bleeder circuit can be determined by setting the parameter values of the voltage regulator tube V1, the resistor R11 and the capacitor C6.

The energy conversion circuit includes an isolation transformer T1 and a switching power supply chip U1, wherein the primary side of the isolation transformer T1, the input and output terminals of the switching power supply chip U1 (ie, ports 4 and 5 of U1), and the DC side of the rectifier circuit ZL1 are connected in series A series loop is formed, and the secondary side of the isolation transformer T1 is connected in parallel with a power taking capacitor C4, and the stable voltage source Uo is output to the electrical load of the subsequent stage through the power taking capacitor C4.

The output protection circuit includes optocoupler U3, voltage regulator tube V2 and voltage divider resistors R5 and R6 (wherein voltage regulator tube V2 and voltage divider resistor R6 form a voltage divider circuit, and voltage divider resistor R5 forms another voltage divider circuit). The input end of the coupling U3 is connected in parallel with the power taking capacitor C4 through the voltage regulator tube V2 and the resistors R5 and R6 arranged in series. The terminal EN, the power supply terminal BP of the switching power supply chip U1 is connected with a startup capacitor C2.

In the above energy conversion circuit, when the voltage (current) across the energy storage capacitor C1 has a wide variation range, the switching power supply chip U1 and the isolation transformer T1 are used as the main parts of the current source to convert the voltage source, the optocoupler U3, the resistor R6 and the voltage regulator. Tube V2 forms a power supply voltage value feedback loop, which is used to adjust the output stable DC voltage value with isolation.

In Figure 1, the input end of the constant current source circuit is connected to the DC side of the rectifier circuit ZL1, and the output end of the constant current source circuit is connected to the startup capacitor C2. Specifically, the constant current source circuit includes:

The first-stage amplifying switch tube Q1 and the second-stage amplifying switch tube Q2, wherein a first voltage divider resistor R2 is arranged in series between the base and the collector of the first-stage amplifying switch tube Q1, and the base and the second-stage amplifying switch tube Q2 are connected in series. A second voltage dividing resistor R3 is arranged in series between the emitters, the first voltage dividing resistor R2 and the second voltage dividing resistor R3 are connected in series, and the second voltage dividing resistor R3 is used to connect the DC side of the rectifier circuit ZL1. In addition, the emitter of the first-stage amplifying switch Q1 is connected to the startup capacitor C2 through the resistor R4 and the directional diode D5, and the emitter of the first-stage amplifying switch Q1 is connected in parallel with the collector of the second-stage amplifying switch Q2.

The constant current source circuit in Figure 1 charges the startup capacitor C2 through the directional diode D5 to provide a stable startup power for the switching power supply chip U1, ensuring that the switching power supply chip U1 can work reliably in a wide range. The switching power supply chip U1 in this embodiment is a switching power supply chip with a built-in MOSFET tube. The input end of the switching power supply chip U1 is connected to the input end of the constant current source circuit through the freewheeling branch, and the freewheeling branch is provided with a freewheeling element in series. The freewheeling element includes a freewheeling diode D3 and a freewheeling resistor R1, and the freewheeling diode D3 and the freewheeling resistor R1 are connected in series. The freewheeling branch provides a high-voltage freewheeling path when the switching power supply chip U1 is turned off, and further ensures the stability of the switching power supply chip U1.

The overall working principle of the above-mentioned power taking circuit is as follows:

The current transformer CT outputs current. If there is a surge current, the anti-surge circuit will automatically start to protect the subsequent circuit. If there is no surge current, the alternating current output by the current transformer CT will be converted into direct current by the rectifier circuit ZL1. If it is too large, the bleeder circuit starts; if the DC does not exceed the limit, charge the energy storage capacitor C1, which is used to charge the startup capacitor C2 of the switching power supply chip U1, so that the switching power supply chip U1 works, and the switching power supply chip After U1 is started, the voltage conversion is performed by the isolation transformer T1. If the converted voltage value is too high, the optocoupler U3 is turned on, enabling the enable terminal EN of the switching power supply chip U1, thereby controlling the switching power supply chip U1 to turn off, and the The current branch provides a high-voltage freewheeling path; if the converted voltage value is in the normal range, the output voltage is supplied to the electrical load through the power-taking capacitor C4.

On the other hand, when the DC output from the rectifier circuit ZL1 suddenly becomes small, the constant current source circuit is used to amplify the signal and continue to charge the startup capacitor C2 to ensure that the switching power supply chip U1 can operate in a wide range (to the current source with a wide variation range). ) works reliably.

The power taking circuit of the utility model uses a wide range of switching power supply chips and isolation transformers to convert the secondary current (that is, the current source) output by the current transformer into a stable voltage source (used as a working power supply), which can effectively reduce power supply equipment. Operating costs, such as PT cabinets, UPS and DC panels, etc., and can increase the scope of application of power smart devices. In addition, through the optocoupler and the voltage divider circuit, the startup threshold is set for the switching power supply chip, and the hysteresis comparison function is provided to prevent the jitter of the load power supply.

In addition, discharge current, anti-surge circuit and freewheeling branch are applied in the power taking circuit of the present invention as safety protection measures. Among them, the discharge circuit works when the current of the current transformer is relatively large, which can effectively prevent the secondary side of the current transformer from generating high voltage and open circuit, avoid damage to the equipment or cause personal casualties, and further ensure the safety of the site and equipment. The power taking circuit of the utility model has the advantages of low cost, stable working performance and convenient use, and can provide users with a stable, economical and reliable power taking circuit.

The power consumption of the power-consuming part of the power-taking circuit in this embodiment is basically constant, or varies within a small range, so the power-taking circuit of the present invention can achieve the maximum conversion efficiency when the power supply current is small, and When the current is large, the excess power is consumed, thereby ensuring the efficiency and stability of the power taking circuit at the same time.

The above descriptions are only preferred embodiments of the present application and are not intended to limit the present application. The scope of patent protection of the present application is subject to the claims. The same shall be included in the protection scope of this application. For example, the switching power supply chip in this embodiment is a switching power supply chip U1 with a built-in MOSFET, as another implementation manner, a flyback switching power supply with other topologies may be used instead. For another example, the input end of the optocoupler U3 is provided with two voltage divider circuits in series, wherein one voltage divider circuit includes a voltage regulator tube V2 and a resistor R6 connected in series. Zener tube; as another implementation manner, only one voltage divider circuit may be provided, for example, only a voltage regulator tube V2 and a voltage divider resistor R6 are included, and another voltage divider circuit is not provided.

For another example, in this embodiment, in order to realize that the output protection circuit can block the enable terminal of the switching power supply chip when the voltage of the power-taking capacitor exceeds the limit, this can be realized by an optocoupler and a voltage divider circuit. The data acquisition interface of the sampling control chip is connected to the electric capacitor for sampling, and the control interface of the sampling control chip is controlled and connected to the enabling terminal of the switching power supply chip.

Claims (10)

1. A current transformer gets electric circuit, its characterized in that should get electric circuit and include:

the alternating current side of the rectifying circuit is used for being connected with the output end of the current transformer;

the energy conversion circuit comprises an isolation transformer and a switching power supply chip, wherein the primary side of the isolation transformer, the input end and the output end of the switching power supply chip and the direct current side of the rectifying circuit are connected in series to form a series loop, and the secondary side of the isolation transformer is connected with a power taking capacitor after rectification;

the output protection circuit is connected with the power taking capacitor in a sampling mode, when the voltage of the power taking capacitor exceeds the limit, the enabling end of the switching power supply chip is locked, and the power supply end of the switching power supply is connected with the starting capacitor;

and the input end of the constant current source circuit is connected with the direct current side of the rectifying circuit, and the output end of the constant current source circuit is connected with the starting capacitor and used for charging the starting capacitor.

2. The current transformer power-taking circuit according to claim 1, wherein the output protection circuit comprises an optical coupler, an input of the optical coupler is connected in parallel with the power-taking capacitor through a voltage division circuit, and an output end of the optical coupler is connected with an enabling end of the switching power supply chip.

3. The current transformer power-taking circuit according to claim 2, wherein the voltage dividing circuit comprises a voltage regulator tube and a voltage dividing resistor.

4. The current transformer power-taking circuit according to claim 1, wherein the constant current source circuit comprises:

the primary amplification switching tube and the secondary amplification switching tube are connected in series, wherein a first voltage-dividing resistor is arranged between a base electrode and a collector electrode of the primary amplification switching tube in series, a second voltage-dividing resistor is arranged between a base electrode and an emitter electrode of the secondary amplification switching tube in series, the first voltage-dividing resistor and the second voltage-dividing resistor are connected in series, and the second voltage-dividing resistor is used for being connected with a direct current side of the rectifying circuit;

and the emitter of the first-stage amplification switching tube is connected with the starting capacitor through a third resistor, and the emitter of the first-stage amplification switching tube is connected with the collector of the second-stage amplification switching tube in parallel.

5. The current transformer power-taking circuit according to claim 1, further comprising:

the surge protection circuit is connected with the output end of the current transformer in parallel, and is connected with the alternating current side of the rectification circuit in parallel.

6. The current transformer power-taking circuit according to claim 1, further comprising:

the discharge circuit comprises a discharge switch tube and a discharge element, the discharge switch tube is connected with the direct current side of the rectification circuit in parallel, the discharge element is connected between the control end of the discharge switch tube and the cathode in series, and the discharge element is connected with an energy storage capacitor in series through a voltage stabilizing tube.

7. The current transformer power-taking circuit according to claim 6, wherein the discharge element comprises a discharge resistor and a discharge capacitor, and the discharge resistor and the discharge capacitor are connected in parallel.

8. The current transformer power-taking circuit according to claim 1, wherein a freewheeling branch is connected in parallel to the secondary side of the isolation transformer, and a freewheeling element is connected in series to the freewheeling branch.

9. The current transformer getting circuit according to claim 8, wherein the freewheeling element comprises a freewheeling diode and a freewheeling resistor, and the freewheeling diode and the freewheeling resistor are connected in series.

10. The current transformer power-taking circuit according to claim 1, further comprising an energy storage capacitor connected in parallel with the dc side of the rectifying circuit.

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