High-frequency transformer common-mode noise test circuit and electronic equipment
By using a voltage follower circuit to isolate and follow the excitation signal in the high-frequency transformer common-mode noise test circuit, the problem of transformer inductance interfering with the test results is solved, thereby improving test accuracy and signal-to-noise ratio.
Patent Information
- Application Number
- CN202520255951.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-17
- Publication Date
- 2025-12-26
- Estimated Expiration
- 2035-02-17
AI Technical Summary
In the common-mode noise test of a single high-frequency transformer, the inductance of the transformer's primary winding will affect the voltage connected to the primary winding, thereby interfering with the test results.
A voltage follower circuit is used to isolate and follow the excitation signal. By utilizing the high input impedance and low output impedance characteristics of the voltage follower circuit, the excitation signal after isolation and following remains consistent, reducing the impact of transformer inductance on the primary winding.
This improved the accuracy and signal-to-noise ratio of the test results and reduced the impact of space radiation on the test results.
Smart Images
Figure CN223727919U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of common mode noise testing, and particularly relates to a high-frequency transformer common mode noise testing circuit and electronic equipment. BACKGROUND
[0002] The high-frequency transformer single-body common mode noise testing provides a testing method and means for the front end of the final testing of the power supply common mode noise, and has important significance for the control of the power supply quality.
[0003] The related high-frequency transformer single-body common mode noise testing usually uses a signal generator as a testing signal source, but the use of the signal generator involves output impedance matching, and most signal generators are low-resistance output (default 50Ω), that is, can be equivalent to a voltage source in series with a 50Ω circuit. When the high-frequency transformer is tested, the low-resistance output of the signal generator and the primary winding in the transformer form a voltage divider, the larger the inductance of the primary winding, the higher the voltage divided, and the measured common mode noise value of the transformer will also be larger.
[0004] However, the related high-frequency transformer single-body common mode noise testing has the following situations: first, the transformer inductance has a tolerance, resulting in inaccurate test results; second, when the transformer inductance is small, the voltage divided at both ends of the primary winding will also be small, and the measured common mode noise will also be small, reducing the signal-to-noise ratio and making the test results more susceptible to interference. That is, the transformer inductance will affect the voltage connected to the primary winding, and then interfere with the test results. CONTENT OF THE INVENTION
[0005] The application aims to provide a high-frequency transformer common mode noise testing circuit and electronic equipment, and aims to solve the problem that in the related high-frequency transformer single-body common mode noise testing, the inductance of the primary winding of the transformer will affect the voltage connected to the primary winding, and then interfere with the test results.
[0006] The application embodiment provides a high-frequency transformer common mode noise testing circuit, comprising:
[0007] A signal generating circuit is configured to output an excitation signal.
[0008] A voltage follower circuit is connected to the signal generating circuit and configured to isolate and follow the excitation signal to output the isolated and followed excitation signal.
[0009] A transformer is provided, and the primary winding with the least number of turns generates a displacement current between the primary winding and the secondary winding under the excitation of the isolated and followed excitation signal. The displacement current is the current between the primary static point and the secondary static point after the primary static point is short-circuited, and the primary static point and the secondary static point are both points with constant voltage.
[0010] a detection circuit connected between the primary quiescent point and the secondary quiescent point, configured to sample the displacement current to output a detection voltage.
[0011] In one of the embodiments, the high-frequency transformer common-mode noise test circuit further comprises:
[0012] a display circuit connected with the secondary winding and the detection circuit, configured to perform analog-digital conversion on the detection voltage, and display the detection voltage after the analog-digital conversion.
[0013] In one of the embodiments, the display circuit of the high-frequency transformer common-mode noise test circuit comprises:
[0014] a rectification module connected with the detection circuit, configured to rectify the detection voltage to output an analog voltage;
[0015] an analog-digital conversion module connected with the rectification module, configured to perform analog-digital conversion on the analog voltage to output a digital signal;
[0016] a display module configured to display according to the digital signal.
[0017] In one of the embodiments, the high-frequency transformer common-mode noise test circuit further comprises:
[0018] a signal amplification circuit connected with the detection circuit and the display circuit, configured to amplify the detection voltage to output the amplified detection voltage;
[0019] the display circuit is specifically configured to display according to the amplified detection voltage.
[0020] In one of the embodiments, the signal amplification circuit comprises a second triode, a seventh resistor, an eighth resistor, a ninth resistor, a fourth capacitor and a fifth capacitor.
[0021] The first end of the seventh resistor is connected with the secondary winding and the detection circuit, the emitter of the second transistor is connected with the power supply ground, and the first end of the seventh resistor and the emitter of the second transistor are used as the detection voltage input end of the signal amplification circuit together to input the detection voltage; the second end of the seventh resistor and the first end of the fourth capacitor are connected, the second end of the fourth capacitor, the first end of the eighth resistor and the base of the second transistor are connected, the collector of the second transistor, the first end of the fifth capacitor and the first end of the ninth resistor are connected, and the second end of the fifth capacitor and the emitter of the second transistor are used as the amplified detection voltage output end of the signal amplification circuit together and are connected with the display circuit to output the amplified detection voltage; and the second end of the eighth resistor and the second end of the ninth resistor are connected with the second power supply.
[0022] In one of the embodiments, the high-frequency transformer common-mode noise test circuit further comprises:
[0023] A filter circuit is connected with the detection circuit and the display circuit, and is used for band-pass filtering the detection voltage to output the band-pass filtered detection voltage.
[0024] The display circuit is specifically used for displaying according to the band-pass filtered detection voltage.
[0025] In one of the embodiments, the signal generation circuit is a sine wave generation circuit.
[0026] In one of the embodiments, the voltage follower circuit comprises a first operational amplifier.
[0027] The non-inverting input end of the first operational amplifier is used as the excitation signal input end of the voltage follower circuit, is connected with the signal generation circuit to access the excitation signal, and the inverting input end of the first operational amplifier and the output end of the first operational amplifier are used as the isolated and followed excitation signal output end of the voltage follower circuit together and are connected with the transformer to output the isolated and followed excitation signal.
[0028] In one of the embodiments, the signal generation circuit comprises a first transistor, an inductor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, a third capacitor, a tenth capacitor and an eleventh capacitor.
[0029] The first end of the first resistor and the first end of the third resistor are connected with a first power supply, the second end of the first resistor, the first end of the second capacitor, the base of the first triode and the first end of the second resistor are connected, the second end of the third resistor, the collector of the first triode, the first end of the third capacitor and the first end of the inductor are connected with the voltage follower circuit, the second end of the second resistor, the second end of the fourth resistor, the first end of the first capacitor, the second end of the second capacitor, the second end of the tenth capacitor and the second end of the eleventh capacitor are connected with a power supply ground, the second end of the third resistor, the collector of the first triode, the first end of the third capacitor, the first end of the inductor, the second end of the second resistor, the second end of the fourth resistor, the second end of the first capacitor, the second end of the second capacitor, the second end of the tenth capacitor and the second end of the eleventh capacitor are collectively used as an excitation signal output end of the signal generating circuit to output the excitation signal; the emitter of the first triode, the first end of the fourth resistor, the first end of the first capacitor, the second end of the third capacitor and the first end of the tenth capacitor are connected, and the second end of the inductor and the first end of the eleventh capacitor are connected.
[0030] The embodiment of the present application also provides an electronic device comprising the high-frequency transformer common-mode noise test circuit.
[0031] Compared with the prior art, the embodiment of the present application has the beneficial effects that: the voltage follower circuit is used to isolate and follow the excitation signal, because the voltage follower circuit has high input impedance and low output impedance characteristics and also has an isolation effect, so that the excitation signal after isolation and following remains consistent in the case of testing different transformer inductances, thereby reducing the possibility of interference of the excitation signal of the primary winding with the least number of turns caused by the transformer inductance, and further improving the accuracy of the test result; compared with the excitation signal after isolation and following of other primary windings with more turns, the excitation signal after isolation and following of the primary winding with the least number of turns is equivalent to improving the detection voltage value (voltage is proportional to the number of turns) under the premise that the peak value of the excitation signal after isolation and following remains unchanged, thereby improving the signal-to-noise ratio and reducing the influence of space radiation on the test result. BRIEF DESCRIPTION OF DRAWINGS
[0032] In order to more clearly illustrate the technical application in the embodiment of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0033] Figure 1 A structural schematic diagram of a high-frequency transformer common-mode noise test circuit provided by an embodiment of the present application is shown in FIG. 1.
[0034] Figure 2 Another structural schematic diagram of a high-frequency transformer common-mode noise test circuit provided by an embodiment of the present application is shown in FIG. 2.
[0035] Figure 3 Another structural schematic diagram of a high-frequency transformer common-mode noise test circuit provided by an embodiment of the present application is shown in FIG. 3.
[0036] Figure 4 Another structural schematic diagram of a high-frequency transformer common-mode noise test circuit provided by an embodiment of the present application is shown in FIG. 4.
[0037] Figure 5 Another structural schematic diagram of a high-frequency transformer common-mode noise test circuit provided by an embodiment of the present application is shown in FIG. 5.
[0038] Figure 6 A partial example circuit schematic diagram of a high-frequency transformer common-mode noise test circuit provided by an embodiment of the present application is shown in FIG. 6. DETAILED DESCRIPTION
[0039] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.
[0040] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.
[0041] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.
[0042] In addition, the terms "first", "second", etc. are used only for descriptive purposes and should not be construed as implying or suggesting relative importance or an indicated number of technical features. Thus, the features defined as "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality" is two or more, unless otherwise explicitly and specifically limited.
[0043] Figure 1 The structure diagram of the high-frequency transformer common-mode noise test circuit provided by an embodiment of the present application is shown, only the parts related to the embodiment are shown for the convenience of description, and the details are described as follows:
[0044] The high-frequency transformer common-mode noise test circuit includes a signal generating circuit 10, a voltage follower circuit 20, a transformer T1, and a detection circuit 30.
[0045] The signal generating circuit 10 is configured to output an excitation signal.
[0046] The voltage follower circuit 20 is connected to the signal generating circuit 10 and configured to isolate and follow the excitation signal to output the isolated and followed excitation signal.
[0047] The transformer T1 has a primary winding with the least number of turns, under the excitation of the isolated and followed excitation signal, displacement current is generated between the primary winding and a secondary winding; wherein the displacement current is the current between the primary static point and the secondary static point, and the primary static point and the secondary static point are points with constant voltage.
[0048] The detection circuit 30 is connected between the primary static point and the secondary static point and configured to sample the displacement current to output a detection voltage.
[0049] It should be noted that the signal generating circuit 10 can be a signal generator or built by discrete components, the excitation signal can be a common waveform such as a square wave or a sine wave, and the voltage peak value and frequency of the excitation signal can be set according to the actual tested transformer T1.
[0050] In a specific implementation, taking the sine wave as an example, the voltage values at both ends of the primary winding with the least number of turns corresponding to different transformer T1 inductances before and after setting the voltage follower circuit 20 are measured, and the following data are obtained:
[0051]
[0052]
[0053] The measured results further prove that the voltage follower circuit 20 arranged between the signal generating circuit 10 and the transformer T1 winding can reduce the possibility that the input voltage at the primary winding with the least number of turns is affected by the inductance of the transformer T1, thereby ensuring the consistency of the input voltage at the primary winding with the least number of turns when testing different inductances of the transformer T1.
[0054] It should be noted that when the primary winding with the least number of turns of the transformer T1 is connected to the voltage, the primary winding and the secondary winding will generate induced voltage, thereby generating displacement current. The detection circuit 30 arranged between the primary static point and the secondary static point can sample the voltage of the displacement current to obtain the detection voltage. The value of the detection voltage is positively correlated with the value of the displacement current, so that the size of the displacement current can be judged by the detection voltage, and the size of the common-mode noise can be further judged.
[0055] In the related high-frequency transformer single common-mode noise test, the frequency of the excitation signal is usually 100 kHz. The following table of sine wave frequency and corresponding detection voltage is obtained by continuing to test the sine wave as an example.
[0056] Sine wave frequency / kHz Detection voltage / mV 100 229.96 200 384.53 300 518.87 400 621.17 500 695.33
[0057] From the measured values in the above table and the theory, it can be known that when the sine wave frequency is less than the preset value, the transformer T1 single common-mode noise test result is positively correlated with the frequency of the input signal source, so that the test result can be amplified by increasing the working frequency of the excitation signal, and the signal-to-noise ratio can be increased.
[0058] It should be noted that the preset value can be the frequency corresponding to the turning point at which the inductance of the transformer T1 starts to decrease as the sine wave frequency rises. When setting the sine wave frequency, the working frequency of the excitation signal should be as high as possible under the condition of being less than the preset value, so as to improve the reliability of the test result.
[0059] The voltage follower circuit 20 isolates and follows the excitation signal, avoiding the influence of the inductance of the transformer T1 on the excitation signal, and ensuring the stability of the signal generating circuit 10.
[0060] As an example but not limitation, as shown in Figure 2 The high-frequency transformer common-mode noise test circuit further includes a display circuit 40.
[0061] The display circuit 40 is connected with the secondary winding and the detection circuit 30, and is used for analog-to-digital conversion of the detection voltage, and display of the detection voltage after digital-to-analog conversion.
[0062] The value of the detection voltage is displayed through the display circuit 40, and the test result is more intuitive, improving the convenience of use.
[0063] As an example but not limitation, as shown in Figure 3 The display circuit 40 includes a rectification module 41, an analog-digital conversion module 42 and a display module 43.
[0064] The rectification module 41 is connected with the detection circuit 30, and is configured to rectify the detection voltage to output an analog voltage.
[0065] The analog-digital conversion module 42 is connected with the rectification module 41, and is configured to analog-digital convert the analog voltage to output a digital signal.
[0066] The display module 43 is configured to display according to the digital signal.
[0067] In specific implementation, the analog-digital conversion module 42 can include a microprocessor, and the display module 43 can include a digital tube.
[0068] The digital tube directly displays the digital signal, and the test result can be read without an oscilloscope, which simplifies the test process and reduces the test cost.
[0069] As an example but not limitation, as shown in Figure 4 The high-frequency transformer common-mode noise test circuit further includes a signal amplification circuit 50.
[0070] The signal amplification circuit 50 is connected with the detection circuit 30 and the display circuit 40, and is configured to amplify the detection voltage to output an amplified detection voltage.
[0071] The display circuit 40 is specifically configured to display according to the amplified detection voltage.
[0072] In actual use, the detection voltage value is small and is easily affected by radiation of other devices in space. Therefore, the signal amplification circuit 50 is arranged to amplify the detection voltage to enhance the anti-interference ability of the detection voltage.
[0073] As an example but not limitation, as shown in Figure 5 The high-frequency transformer common-mode noise test circuit further includes a filter circuit 60.
[0074] The filter circuit 60 is connected with the detection circuit 30 and the display circuit 40, and is configured to filter the detection voltage to output a filtered detection voltage.
[0075] The display circuit 40 is specifically configured to display according to the filtered detection voltage.
[0076] In specific implementation, the filter circuit 60 can be a band-pass filter circuit 60.
[0077] The filter circuit 60 removes the peak voltage in the detection voltage, and improves the stability of the high-frequency transformer common-mode noise test circuit.
[0078] As an example but not limitation, the transformer T1 includes at least two primary windings.
[0079] In the embodiment, the voltage follower circuit 20 is connected to the primary winding with the least number of turns, which is equivalent to increasing the value of the detected voltage (voltage is proportional to the number of turns) under the premise that the peak value of the isolated and followed excitation signal remains unchanged, thereby improving the signal-to-noise ratio and reducing the influence of space radiation on the test results. It can be understood that due to the voltage follower circuit 20, even if the inductance of the primary winding with the least number of turns is small (inductance is proportional to the square of the number of turns), the stability of the isolated and followed excitation signal can be ensured. Taking the transformer T1 including two primary windings as an example for testing, the following results can be obtained:
[0080]
[0081] The signal generating circuit 10 is connected to the primary winding with the least number of turns, and the amplification factor of the common-mode noise of the transformer T1 is approximately proportional to the ratio of the number of turns of the second primary winding and the primary winding with the least number of turns, that is, compared with the second primary winding with more turns, the detection voltage will be amplified by a certain ratio according to the ratio of the number of turns when the primary winding with the least number of turns is connected.
[0082] As an example but not limitation, the signal generating circuit 10 is a sine wave generating circuit.
[0083] It can be understood that the peak-to-peak voltage and frequency of the sine wave can be set according to different transformers T1.
[0084] The sine wave has a smooth waveform, low noise, and small interference to precision equipment, and as an excitation signal, it can reduce the interference to the test results, thereby improving the accuracy of the test results.
[0085] Figure 6 A part of the circuit structure of the high-frequency transformer common-mode noise test circuit provided by the embodiment of the application is shown, only the part related to the embodiment of the application is shown for the convenience of description, and the details are as follows:
[0086] The signal amplification circuit 50 includes a second triode Q2, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a fourth capacitor C4, and a fifth capacitor C5.
[0087] The first end of the seventh resistor R7 is connected with the secondary winding and the detection circuit 30, the emitter of the second triode Q2 is connected with the power supply ground, the first end of the seventh resistor R7 and the emitter of the second triode Q2 are connected together as the detection voltage input end of the signal amplification circuit 50, so as to input the detection voltage; the second end of the seventh resistor R7 and the first end of the fourth capacitor C4 are connected, the second end of the fourth capacitor C4, the first end of the eighth resistor R8 and the base of the second triode Q2 are connected, the collector of the second triode Q2, the first end of the fifth capacitor C5 and the first end of the ninth resistor R9 are connected, the second end of the fifth capacitor C5 and the emitter of the second triode Q2 are connected together as the amplified detection voltage output end of the signal amplification circuit 50, and are connected with the display circuit 40, so as to output the amplified detection voltage; the second end of the eighth resistor R8 and the second end of the ninth resistor R9 are connected with the second power supply.
[0088] The circuit is simple, low in cost, and can enhance the anti-interference ability of the test result.
[0089] The voltage follower circuit 20 comprises a first operational amplifier M1.
[0090] The non-inverting input end of the first operational amplifier M1 is connected with the signal generation circuit 10 as the excitation signal input end of the voltage follower circuit 20, so as to input the excitation signal; the inverting input end of the first operational amplifier M1 and the output end of the first operational amplifier M1 are connected together as the isolated and followed excitation signal output end of the voltage follower circuit 20, and are connected with the transformer T1, so as to output the isolated and followed excitation signal.
[0091] In the embodiment, the voltage follower circuit 20 can further comprise resistors and capacitors.
[0092] The first operational amplifier M1 has high input impedance and low output impedance characteristics, and has an isolation effect, so that the influence of the transformer T1 inductance on the input voltage and the test result is solved.
[0093] The multiple primary static points of the transformer T1 are connected with the power supply ground. The first end of the first primary winding of the transformer T1 is connected with the voltage follower circuit 20, so as to input the isolated and followed excitation signal.
[0094] The signal generation circuit 10 comprises a first triode Q1, an inductor L1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, a second capacitor C2, a third capacitor C3, a tenth capacitor C10 and an eleventh capacitor C11.
[0095] The first end of the first resistor R1 and the first end of the third resistor R3 are connected to the first power supply, the second end of the first resistor R1, the first end of the second capacitor C2, the base of the first transistor Q1 and the first end of the second resistor R2 are connected, the second end of the third resistor R3, the collector of the first transistor Q1, the first end of the third capacitor C3 and the first end of the inductor L1 are connected to the voltage follower circuit 20, the second end of the second resistor R2, the second end of the fourth resistor R4, the second end of the first capacitor C1, the second end of the second capacitor C2, the second end of the tenth capacitor C10 and the second end of the eleventh capacitor C11 are connected to the power supply ground, the second end of the third resistor R3, the collector of the first transistor Q1, the first end of the third capacitor C3, the first end of the inductor L1, the second end of the second resistor R2, the second end of the fourth resistor R4, the second end of the first capacitor C1, the second end of the second capacitor C2, the second end of the tenth capacitor C10 and the second end of the eleventh capacitor C11 are collectively used as the excitation signal output end of the signal generating circuit 10 to output the excitation signal; the emitter of the first transistor Q1, the first end of the fourth resistor R4, the first end of the first capacitor C1, the second end of the third capacitor C3 and the first end of the tenth capacitor C10 are connected, and the second end of the inductor L1 and the first end of the eleventh capacitor C11 are connected.
[0096] The signal generating circuit 10 is specifically a capacitive three-point oscillation circuit. Wherein, adjusting the capacitive reactance ratio of the third capacitor C3 and the tenth capacitor C10 can change the oscillation amplitude; changing the capacitance value of the eleventh capacitor C11 can change the oscillation frequency, because the voltage feedback coefficient is fixed, so it is not easy to stop oscillation when adjusting the oscillation frequency; the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 are the direct current bias resistors of the first transistor Q1, which ensures that the first transistor Q1 works in the amplification zone; the second capacitor C2 is a bypass capacitor.
[0097] The filter circuit 60 includes a second operational amplifier M2, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a sixth capacitor C6 and a seventh capacitor C7.
[0098] The first end of the tenth resistor R10 is connected with the signal amplification circuit 50, the second end of the eleventh resistor R11 and the non-inverting input end of the second operational amplifier M2 are connected with the power supply ground, the first end of the tenth resistor R10, the second end of the eleventh resistor R11 and the non-inverting input end of the second operational amplifier M2 are collectively used as the amplified detection voltage input end of the filter circuit 60, so as to input the amplified detection voltage; the second end of the tenth resistor R10, the first end of the eleventh resistor R11, the first end of the sixth capacitor C6 and the first end of the seventh capacitor C7 are connected, the inverting input end of the second operational amplifier M2, the second end of the sixth capacitor C6 and the first end of the twelfth resistor R12 are connected, the second end of the seventh capacitor C7, the second end of the twelfth resistor R12 and the output end of the second operational amplifier M2 are collectively used as the filtered detection voltage output end of the filter circuit 60, and are connected with the display circuit 40, so as to output the filtered detection voltage.
[0099] The rectification module 41 comprises a diode D1, a fifth resistor R5, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, an eighth capacitor C8 and a ninth capacitor C9.
[0100] The anode of the diode D1 is connected with the filter circuit 60, the second end of the thirteenth resistor R13, the second end of the eighth capacitor C8 and the second end of the ninth capacitor C9 are connected with the power supply ground, the anode of the diode D1, the second end of the thirteenth resistor R13, the second end of the eighth capacitor C8 and the second end of the ninth capacitor C9 are collectively used as the filtered detection voltage input end of the rectification module 41, so as to input the filtered detection voltage; the cathode of the diode D1 is connected with the first end of the fifteenth resistor R15, the second end of the fifteenth resistor R15, the first end of the thirteenth resistor R13, the first end of the fourteenth resistor R14 and the first end of the eighth capacitor C8 are connected, the second end of the fourteenth resistor R14, the first end of the ninth capacitor C9 and the first end of the fifth resistor R5 are connected, and the second end of the fifth resistor R5 is used as the analog voltage output end of the rectification module 41, and is connected with the analog-digital conversion module 42, so as to output the analog voltage.
[0101] The circuit is simple and low in cost.
[0102] The detection circuit 30 comprises a sixth resistor R6.
[0103] The first end of the sixth resistor R6 is connected with the secondary winding, the second end of the sixth resistor R6 is connected with the power supply ground, and the first end of the sixth resistor R6 is used as the displacement current input end of the detection circuit 30, so as to input the displacement current; and the first end of the sixth resistor R6 and the second end of the sixth resistor R6 are collectively used as the detection voltage output end of the detection circuit 30, so as to output the detection voltage.
[0104] The circuit is simple and reliable.
[0105] The following is further described in conjunction with the working principle shown in Figure 6
[0106] The signal generating circuit 10 outputs the excitation signal to the non-inverting input terminal of the first operational amplifier M1, the operational amplifier U1 follows the excitation signal, and outputs the isolated and followed excitation signal from the output terminal of the first operational amplifier M1 to the first end of the primary winding with the least number of turns of the transformer T1. Under the excitation of the isolated and followed excitation signal, the transformer T1 outputs the displacement current to the first end of the sixth resistor R6. The first end of the sixth resistor R6 and the second end of the sixth resistor R6 jointly output the detection voltage to the first end of the seventh resistor R7 and the emitter of the second transistor Q2. The second transistor Q2 amplifies the detection voltage and outputs the amplified detection voltage from the second end of the fifth capacitor C5 and the emitter of the second transistor Q2. The first end of the tenth resistor R10, the second end of the eleventh resistor R11, and the non-inverting input terminal of the second operational amplifier M2 input the amplified detection voltage. After being band-pass filtered by the second operational amplifier M2, the tenth resistor R10, the eleventh resistor R11, the twelfth resistor R12, the sixth capacitor C6, and the seventh capacitor C7, the second end of the seventh capacitor C7, the second end of the twelfth resistor R12, and the output terminal of the second operational amplifier M2 output the filtered detection voltage. The diode D1 unidirectionally conducts the filtered detection voltage. The thirteenth resistor R13 and the fifteenth resistor R15 divide the voltage of the unidirectionally conducted detection voltage, and output the analog voltage from the second end of the fifth resistor R5 to the analog-digital conversion module 42. The analog-digital conversion module 42 converts the analog voltage into digital voltage and outputs the digital voltage to the display module 43 for display.
[0107] The embodiment of the present application also provides an electronic device, which comprises the high-frequency transformer common-mode noise test circuit.
[0108] It should be understood that the size of the serial number of each step in the above-mentioned embodiment does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.
[0109] The above-described embodiments are only used to illustrate the technical solutions of the present application, but not limit them; although the foregoing embodiments of the present application have been described in detail, those skilled in the art should understand: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.
Claims
1. A high frequency transformer common mode noise test circuit, characterized by, The signal generation circuit is used for outputting an excitation signal. The voltage follower circuit is connected with the signal generation circuit, and is used for isolating and following the excitation signal to output the isolated and followed excitation signal. The transformer has a primary winding with the least number of turns, and a displacement current is generated between the primary winding and a secondary winding under the excitation of the isolated and followed excitation signal; wherein the displacement current is a current between a primary static point and a secondary static point, and the primary static point and the secondary static point are both points with constant voltage. The detection circuit is connected between the primary static point and the secondary static point, and is used for sampling the displacement current to output a detection voltage. Further comprising:
2. The high frequency transformer common mode noise test circuit of claim 1, wherein, The display circuit is connected with the secondary winding and the detection circuit, and is used for analog-digital converting the detection voltage, and displaying the analog-digital converted detection voltage. The display circuit comprises:
3. The high frequency transformer common mode noise test circuit of claim 2, wherein, The rectification module is connected with the detection circuit, and is used for rectifying the detection voltage to output an analog voltage; The analog-digital conversion module is connected with the rectification module, and is used for analog-digital converting the analog voltage to output a digital signal; The display module is used for displaying according to the digital signal. Further comprising:
4. The high frequency transformer common mode noise test circuit of claim 2, wherein, The signal amplification circuit is connected with the detection circuit and the display circuit, and is used for amplifying the detection voltage to output the amplified detection voltage; The display circuit is specifically used for displaying according to the amplified detection voltage. The signal amplification circuit comprises a second triode, a seventh resistor, an eighth resistor, a ninth resistor, a fourth capacitor and a fifth capacitor; 5. The high frequency transformer common mode noise test circuit of claim 4, wherein, The first end of the seventh resistor is connected with the secondary winding and the detection circuit, the emitter of the second triode is connected with a power supply ground, the first end of the seventh resistor and the emitter of the second triode are used as a detection voltage input end of the signal amplification circuit to input the detection voltage; the second end of the seventh resistor and the first end of the fourth capacitor are connected, the second end of the fourth capacitor, the first end of the eighth resistor and the base of the second triode are connected, the collector of the second triode, the first end of the fifth capacitor and the first end of the ninth resistor are connected, the second end of the fifth capacitor and the emitter of the second triode are used as an amplified detection voltage output end of the signal amplification circuit to output the amplified detection voltage, and are connected with the display circuit to output the amplified detection voltage; the second end of the eighth resistor and the second end of the ninth resistor are connected with a second power supply. Further comprising:
6. The high frequency transformer common mode noise test circuit of claim 2, wherein, The filter circuit is connected with the detection circuit and the display circuit, and is used for band-pass filtering the detection voltage to output the band-pass filtered detection voltage; The display circuit is specifically used for displaying according to the band-pass filtered detection voltage. The signal generation circuit is a sine wave generation circuit.
7. The high frequency transformer common mode noise test circuit of claim 1, wherein, The voltage follower circuit comprises a first operational amplifier; 8. The high frequency transformer common mode noise test circuit of any one of claims 1 to 7, wherein, The noninverted input end of the first operational amplifier is connected with the signal generating circuit as the excitation signal input end of the voltage follower circuit to access the excitation signal; and the inverted input end of the first operational amplifier and the output end of the first operational amplifier are connected with the transformer as the excitation signal output end after isolation and following to output the excitation signal after isolation and following.
9. The high frequency transformer common mode noise test circuit of any one of claims 1 to 7, wherein, The signal generating circuit comprises a first triode, an inductor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, a third capacitor, a tenth capacitor and an eleventh capacitor. The first end of the first resistor and the first end of the third resistor are connected with a first power supply, the second end of the first resistor, the first end of the second capacitor, the base of the first triode and the first end of the second resistor are connected, the second end of the third resistor, the collector of the first triode, the first end of the third capacitor and the first end of the inductor are connected with the voltage follower circuit, the second end of the second resistor, the second end of the fourth resistor, the first end of the first capacitor, the second end of the second capacitor, the second end of the tenth capacitor and the second end of the eleventh capacitor are connected with a power supply ground, the second end of the third resistor, the collector of the first triode, the first end of the third capacitor, the first end of the inductor, the second end of the second resistor, the second end of the fourth resistor, the second end of the first capacitor, the second end of the second capacitor, the second end of the tenth capacitor and the second end of the eleventh capacitor are connected as the excitation signal output end of the signal generating circuit to output the excitation signal, the emitter of the first triode, the first end of the fourth resistor, the first end of the first capacitor, the second end of the third capacitor and the first end of the tenth capacitor are connected, and the second end of the inductor and the first end of the eleventh capacitor are connected.
10. An electronic device, comprising: The high-frequency transformer common-mode noise test circuit comprises the high-frequency transformer common-mode noise test circuit according to any one of claims 1 to 9.