Bias current detection circuit of single-phase industrial frequency transformer
By designing a sampling transformer and current sampling circuit to directly detect the bias current of a single-phase power frequency transformer, the problems of high cost and low accuracy in the existing technology are solved, and low-cost and high-precision bias current detection is realized.
Patent Information
- Application Number
- CN202423049743.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-11
- Publication Date
- 2026-02-03
- Estimated Expiration
- 2034-12-11
AI Technical Summary
In the existing technology, the detection of bias current of single-phase power frequency transformers relies on high-cost Hall current sensors and software algorithms, resulting in low detection accuracy and high cost.
The sampling transformer, current sampling circuit, and amplification circuit are used to directly obtain the bias current by detecting the induced current of the sampling winding. The design of the sampling transformer windings with opposite directions makes the magnetic flux cancel each other when there is no bias, and forms an induced current when there is bias. The bias current signal is obtained through current sampling and amplification circuits.
It achieves low-cost and high-precision bias current detection, avoids dependence on Hall current sensors, and improves detection accuracy.
Smart Images
Figure CN223870729U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of power frequency transformers, and in particular to a bias current detection circuit for a single-phase power frequency transformer. Background Technology
[0002] Single-phase power frequency transformers are core components widely used in power conversion equipment. Besides voltage conversion and energy transfer, single-phase power frequency transformers also offer advantages such as fault isolation and resistance to load surges, making them essential components in inverters, uninterruptible power supplies (UPS), and converters.
[0003] Products with single-phase power frequency transformers (such as inverters) inevitably experience magnetization issues in practical use. Currently, the main method for detecting the magnetization current of a single-phase power frequency transformer is to collect the primary and secondary currents of the transformer and then calculate the current magnitude using software algorithms. However, in high-power inverters, the primary current of the single-phase power frequency transformer can reach several hundred amperes. This necessitates high-specification and expensive Hall current sensors for collecting the primary current. Furthermore, the magnetization current is calculated using software algorithms within the MCU processor, leading to a discrepancy between the calculated and actual magnetization current. Consequently, even with subsequent software adjustments, it is difficult to completely eliminate the magnetization current.
[0004] In view of the above problems, it is necessary to study a single-phase power frequency transformer bias current detection circuit that is low in cost and can accurately detect bias current. Utility Model Content
[0005] The purpose of this invention is to provide a single-phase power frequency transformer bias current detection circuit that is low in cost and can accurately detect bias current.
[0006] To achieve the above objectives, the solution of this utility model is:
[0007] A single-phase power frequency transformer bias current detection circuit is disclosed, which is used to detect the bias current of a single-phase power frequency transformer. The single-phase power frequency transformer bias current detection circuit includes a sampling transformer, a current sampling circuit, and an amplification circuit connected in sequence. The sampling transformer has a first winding Np, a second winding Ns, and a sampling winding N1. The first winding Np and the second winding Ns are wound in opposite directions, while the first winding Np and the sampling winding N1 are wound in the same direction. The first winding Np is connected in series in the primary circuit of the single-phase power frequency transformer, and the second winding Ns is connected in series in the secondary circuit of the single-phase power frequency transformer. The current sampling circuit is connected to both ends of the sampling winding N1.
[0008] The current sampling circuit includes a resistor R1, with its two ends connected to the first and second connection terminals of the current sampling circuit, which are respectively connected to the two ends of the sampling winding N1. The amplifier circuit is a differential amplifier circuit, with its non-inverting input terminal and inverting input terminal connected to the first and second connection terminals of the current sampling circuit, respectively.
[0009] The current sampling circuit also includes a resistor R2, the two ends of which are respectively connected to the first connection terminal and the second connection terminal of the current sampling circuit.
[0010] The single-phase power frequency transformer bias current detection circuit also includes a DC bias circuit, which is connected to the output of the amplifier circuit.
[0011] The DC bias circuit includes a resistor R8 and a capacitor C4. The first end of the resistor R8 and the first end of the capacitor C4 are connected to the output of the amplifier circuit. The second end of the resistor R8 is connected to the bias power supply VREF. The second end of the capacitor C4 is grounded.
[0012] The amplifier circuit includes resistors R3, R4, R5, R6, and R7, and operational amplifier U1. The first end of resistor R3 is connected to the non-inverting input of the amplifier circuit. The second end of resistor R3 and the first end of resistor R5 are connected to the non-inverting input of operational amplifier U1. The first end of resistor R4 is connected to the inverting input of the amplifier circuit. The second end of resistor R4 and the first end of resistor R6 are connected to the inverting input of operational amplifier U1. The second end of resistor R5 and the output end of operational amplifier U1 are connected to the output end of the amplifier circuit. The power supply terminal of operational amplifier U1 is connected to the positive power supply VCC+. The ground terminal of operational amplifier U1 and the second end of resistor R6 are grounded.
[0013] The amplifier circuit also includes a capacitor C2 connected in parallel with resistor R5.
[0014] The amplifier circuit also includes capacitors C1 and C3. The two ends of capacitor C1 are connected to the non-inverting input and the inverting input of operational amplifier U1, respectively. The first end of capacitor C3 is connected to the inverting input of operational amplifier U1, and the second end of capacitor C3 is grounded.
[0015] The single-phase power frequency transformer bias current detection circuit further includes a first clamping circuit and a second clamping circuit. The first clamping circuit is connected to the non-inverting input terminal of the operational amplifier U1, and the second clamping circuit is connected to the inverting input terminal of the operational amplifier U1.
[0016] The first clamping circuit includes diodes D1 and D2. The anode of diode D1 is connected to the negative power supply VCC-, and the cathode of diode D2 is connected to the positive power supply VCC+. The anodes of diode D2 and D1 are connected to the non-inverting input of operational amplifier U1. The second clamping circuit includes diodes D3 and D4. The anode of diode D3 is connected to the negative power supply VCC-, and the cathode of diode D4 is connected to the positive power supply VCC+. The anodes of diode D4 and D3 are connected to the non-inverting input of operational amplifier U1. The voltages of the positive power supply VCC+ and the negative power supply VCC- are opposite.
[0017] After adopting the above solution, the working principle of this utility model is as follows:
[0018] Since the first winding Np and the second winding Ns of the sampling transformer are wound in opposite directions, the current direction of the first winding Np and the current direction of the second winding Ns are opposite, which in turn makes the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns have opposite directions.
[0019] When a single-phase power frequency transformer has no bias magnetism, the current magnitude of the first winding Np is the same as that of the second winding Ns (i.e., the primary circuit current and the secondary circuit current of the single-phase power frequency transformer are the same). At this time, the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns have the characteristics of the same magnetic flux magnitude and opposite magnetic flux direction, so that the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns cancel each other out. At this time, there is no induced magnetic flux in the sampling winding N1, so the current in the sampling winding N1 is zero.
[0020] When a single-phase power frequency transformer has a bias magnetization, the current magnitude of the first winding Np is different from that of the second winding Ns (i.e., the primary circuit current and the secondary circuit current of the single-phase power frequency transformer are different). At this time, the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns have different magnitudes and opposite directions. After the magnetic flux that does not belong to the bias magnetization cancels out, the remaining magnetic flux causes the sampling winding N1 to form an induced current. The magnitude of this induced current is the magnitude of the bias magnetization current to be detected. Thus, the single-phase power frequency transformer bias magnetization current detection circuit of this invention samples and amplifies the induced current of the sampling winding N1 through the current sampling circuit and the amplification circuit to obtain the bias magnetization current detection signal corresponding to the induced current of the sampling winding N1. The bias magnetization current detection signal is input into the MCU processor so that the MCU processor can obtain the magnitude of the bias magnetization current to be detected.
[0021] As can be seen from the above, the present invention does not require the use of a Hall current sensor for detecting the bias current, thus reducing costs; moreover, the present invention directly collects an induced current of the same magnitude as the bias current, which allows for more accurate detection of the bias current. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the present invention. Detailed Implementation
[0023] To further explain the technical solution of this utility model, the following detailed description is provided through specific embodiments.
[0024] like Figure 1 As shown, this utility model discloses a bias current detection circuit for a single-phase power frequency transformer, which is used to detect the bias current of a single-phase power frequency transformer. The bias current detection circuit includes a sampling transformer, a current sampling circuit, and an amplification circuit connected in sequence. The sampling transformer has a first winding Np, a second winding Ns, and a sampling winding N1. The winding directions of the first winding Np and the second winding Ns are opposite, while the winding directions of the first winding Np and the sampling winding N1 are the same. The first winding Np is connected in series in the primary circuit of the single-phase power frequency transformer, and the second winding Ns is connected in series in the secondary circuit of the single-phase power frequency transformer. The current sampling circuit is connected to both ends of the sampling winding N1.
[0025] The working principle of this utility model is as follows:
[0026] Since the first winding Np and the second winding Ns of the sampling transformer are wound in opposite directions, the current direction of the first winding Np and the current direction of the second winding Ns are opposite, which in turn makes the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns have opposite directions.
[0027] When a single-phase power frequency transformer has no bias magnetism, the current magnitude of the first winding Np is the same as that of the second winding Ns (i.e., the primary circuit current and the secondary circuit current of the single-phase power frequency transformer are the same). At this time, the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns have the characteristics of the same magnetic flux magnitude and opposite magnetic flux direction, so that the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns cancel each other out. At this time, there is no induced magnetic flux in the sampling winding N1, so the current in the sampling winding N1 is zero.
[0028] When a single-phase power frequency transformer has a bias magnetization, the current magnitude of the first winding Np is different from that of the second winding Ns (i.e., the primary circuit current and the secondary circuit current of the single-phase power frequency transformer are different). At this time, the magnetic flux of the magnetic field generated by the first winding Np and the magnetic flux of the magnetic field generated by the second winding Ns have different magnitudes and opposite directions. After the magnetic flux that does not belong to the bias magnetization cancels out, the remaining magnetic flux causes the sampling winding N1 to form an induced current. The magnitude of this induced current is the magnitude of the bias magnetization current to be detected. Thus, the single-phase power frequency transformer bias magnetization current detection circuit of this invention samples and amplifies the induced current of the sampling winding N1 through the current sampling circuit and the amplification circuit to obtain the bias magnetization current detection signal corresponding to the induced current of the sampling winding N1. The bias magnetization current detection signal is input into the MCU processor so that the MCU processor can obtain the magnitude of the bias magnetization current to be detected.
[0029] As can be seen from the above, the present invention does not require the use of a Hall current sensor for detecting the bias current, thus reducing costs; moreover, the present invention directly collects an induced current of the same magnitude as the bias current, which allows for more accurate detection of the bias current.
[0030] In an embodiment of this utility model, the current sampling circuit includes a resistor R1, with its two ends connected to a first connection terminal and a second connection terminal, respectively. The first and second connection terminals of the current sampling circuit are also connected to the two ends of a sampling winding N1. This current sampling circuit forms a loop with the sampling winding N1, enabling the sampling winding N1 to generate an induced current. The amplifier circuit is a differential amplifier circuit, with its non-inverting and inverting input terminals connected to the first and second connection terminals of the current sampling circuit, respectively. Furthermore, the current sampling circuit also includes a resistor R2, with its two ends connected to the first and second connection terminals of the current sampling circuit, respectively. Resistor R2 and resistor R1 are connected in parallel, which prevents the sampling winding N1 from opening if either resistor R2 or R1 fails.
[0031] In an embodiment of this utility model, the amplification circuit includes resistors R3, R4, R5, R6, and R7, and operational amplifier U1. The first end of resistor R3 is connected to the non-inverting input of the amplification circuit; the second end of resistor R3 and the first end of resistor R5 are connected to the non-inverting input of operational amplifier U1; the first end of resistor R4 is connected to the inverting input of the amplification circuit; the second end of resistor R4 and the first end of resistor R6 are connected to the inverting input of operational amplifier U1; the second end of resistor R5 and the output terminal of operational amplifier U1 are connected to the output terminal of the amplification circuit; the power supply terminal of operational amplifier U1 is connected to the positive power supply VCC+; and the ground terminal of operational amplifier U1 and the second end of resistor R6 are grounded.
[0032] In an embodiment of this utility model, the amplification circuit further includes a capacitor C2 connected in parallel with the resistor R5, which can improve the stability of the amplification circuit.
[0033] In an embodiment of this utility model, the amplifier circuit further includes capacitors C1 and C3. The two ends of capacitor C1 are connected to the non-inverting input terminal and the inverting input terminal of operational amplifier U1, respectively. The first end of capacitor C3 is connected to the inverting input terminal of operational amplifier U1, and the second end of capacitor C3 is grounded. Capacitors C1 and C3 can also improve the stability of the amplifier circuit.
[0034] In an embodiment of this utility model, the single-phase power frequency transformer bias current detection circuit of this utility model further includes a first clamping circuit and a second clamping circuit. The first clamping circuit is connected to the non-inverting input terminal of the operational amplifier U1, and the second clamping circuit is connected to the inverting input terminal of the operational amplifier U1. The first clamping circuit and the second clamping circuit can clamp the voltage of the non-inverting input terminal and the inverting input terminal of the operational amplifier U1 respectively, so as to avoid the voltage of the non-inverting input terminal and the inverting input terminal of the operational amplifier U1 being too large and causing damage to the operational amplifier U1. Specifically, the first clamping circuit includes diodes D1 and D2. The anode of diode D1 is connected to the negative power supply VCC-, and the cathode of diode D2 is connected to the positive power supply VCC+. The anodes of diode D2 and the cathode of diode D1 are connected to the non-inverting input of operational amplifier U1. The second clamping circuit includes diodes D3 and D4. The anode of diode D3 is connected to the negative power supply VCC-, and the cathode of diode D4 is connected to the positive power supply VCC+. The anodes of diode D4 and the cathode of diode D3 are connected to the non-inverting input of operational amplifier U1. The voltages of the positive power supply VCC+ and the negative power supply VCC- are opposite.
[0035] In an embodiment of this utility model, the single-phase power frequency transformer bias current detection circuit further includes a DC bias circuit. The DC bias circuit is connected to the output terminal of the amplifier circuit, and the output terminal of the amplifier circuit is connected to the MCU processor. The DC bias circuit ensures that the output signal of the amplifier circuit is a positive voltage signal to meet the signal reception requirements of the MCU processor. Specifically, the DC bias circuit includes a resistor R8 and a capacitor C4. The resistor R8 acts as a pull-up resistor. The first end of the resistor R8 and the first end of the capacitor C4 are connected to the output terminal of the amplifier circuit. The second end of the resistor R8 is connected to the bias power supply VREF, and the second end of the capacitor C4 is grounded.
[0036] The above embodiments and figures are not intended to limit the product form and style of this utility model. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of this utility model.
Claims
1. A bias current detection circuit for a single-phase power frequency transformer, used to detect the bias current of a single-phase power frequency transformer, characterized in that: The bias current detection circuit of the single-phase power frequency transformer includes a sampling transformer, a current sampling circuit and an amplification circuit connected in sequence. The sampling transformer has a first winding Np, a second winding Ns and a sampling winding N1. The winding directions of the first winding Np and the second winding Ns are opposite, and the winding directions of the first winding Np and the sampling winding N1 are the same. The first winding Np is connected in series in the primary circuit of the single-phase power frequency transformer, and the second winding Ns is connected in series in the secondary circuit of the single-phase power frequency transformer. The current sampling circuit is connected to both ends of the sampling winding N1.
2. The single-phase power frequency transformer bias current detection circuit as described in claim 1, characterized in that: The current sampling circuit includes a resistor R1, with the two ends of the resistor R1 connected to the first connection terminal and the second connection terminal of the current sampling circuit, which are respectively connected to the two ends of the sampling winding N1. The amplifier circuit is a differential amplifier circuit, and the non-inverting input terminal and the inverting input terminal of the amplifier circuit are respectively connected to the first connection terminal and the second connection terminal of the current sampling circuit.
3. The single-phase power frequency transformer bias current detection circuit as described in claim 2, characterized in that: The current sampling circuit also includes a resistor R2, the two ends of which are respectively connected to the first connection terminal and the second connection terminal of the current sampling circuit.
4. The single-phase power frequency transformer bias current detection circuit as described in claim 2, characterized in that: It also includes a DC bias circuit, which is connected to the output of the amplifier circuit.
5. The single-phase power frequency transformer bias current detection circuit as described in claim 4, characterized in that: The DC bias circuit includes a resistor R8 and a capacitor C4. The first end of the resistor R8 and the first end of the capacitor C4 are connected to the output of the amplifier circuit. The second end of the resistor R8 is connected to the bias power supply VREF. The second end of the capacitor C4 is grounded.
6. The single-phase power frequency transformer bias current detection circuit as described in claim 2 or 4, characterized in that: The amplifier circuit includes resistors R3, R4, R5, R6, R7 and operational amplifier U1; The first end of resistor R3 is connected to the non-inverting input of the amplifier circuit. The second end of resistor R3 and the first end of resistor R5 are connected to the non-inverting input of op-amp U1. The first end of resistor R4 is connected to the inverting input of the amplifier circuit. The second end of resistor R4 and the first end of resistor R6 are connected to the inverting input of op-amp U1. The second end of resistor R5 and the output end of op-amp U1 are connected to the output end of the amplifier circuit. The power supply terminal of op-amp U1 is connected to the positive power supply VCC+. The ground terminal of op-amp U1 and the second end of resistor R6 are grounded.
7. The single-phase power frequency transformer bias current detection circuit as described in claim 6, characterized in that: The amplifier circuit also includes a capacitor C2 connected in parallel with resistor R5.
8. The single-phase power frequency transformer bias current detection circuit as described in claim 6, characterized in that: The amplifier circuit also includes capacitors C1 and C3. The two ends of capacitor C1 are connected to the non-inverting input and the inverting input of operational amplifier U1, respectively. The first end of capacitor C3 is connected to the inverting input of operational amplifier U1, and the second end of capacitor C3 is grounded.
9. The single-phase power frequency transformer bias current detection circuit as described in claim 6, characterized in that: It also includes a first clamping circuit and a second clamping circuit. The first clamping circuit is connected to the non-inverting input terminal of the operational amplifier U1, and the second clamping circuit is connected to the inverting input terminal of the operational amplifier U1.
10. The single-phase power frequency transformer bias current detection circuit as described in claim 9, characterized in that: The first clamping circuit includes diodes D1 and D2. The anode of diode D1 is connected to the negative power supply VCC-, the cathode of diode D2 is connected to the positive power supply VCC+, and the anodes of diode D2 and D1 are connected to the non-inverting input of operational amplifier U1. The second clamping circuit includes diodes D3 and D4. The anode of diode D3 is connected to the negative power supply VCC-, and the cathode of diode D4 is connected to the positive power supply VCC+. The anodes of diode D4 and the cathodes of diode D3 are connected to the non-inverting input of operational amplifier U1. The voltages of the positive power supply VCC+ and the negative power supply VCC- are opposite.