Circuit for converting AC weak signal into DC signal and signal conversion device

Abstract

The utility model discloses a circuit for converting an alternating current weak signal into a direct current signal and a signal conversion device.The circuit comprises a signal amplification module, a frequency gating module, a waveform conversion module and an emitter following module, and the signal amplification module is used for amplifying the input alternating current weak signal to obtain an alternating current amplification signal; the frequency gating module is used for filtering harmonic waves in the alternating-current amplified signals to output frequency gating signals, the waveform conversion module is used for converting the frequency gating signals into direct-current signals, and the emitter following module is used for enabling the direct-current signals to have load capacity so as to buffer and output the direct-current signals. The circuit provided by the utility model can convert an AC weak signal into a DC signal with a relatively high voltage, so as to facilitate direct reading of a DC voltage value by using an ADC (Analog to Digital Converter).

Description

Technical Field

[0001] The present application relates to the field of electronic information technology, and in particular to a circuit for converting weak alternating current signals into direct current signals and a signal conversion device. Background Art

[0002] When measuring AC signals, strong electricity is usually measured, which needs to be converted into DC after voltage reduction, rectification, and filtering. When measuring weak AC signals, the following problems arise:

[0003] 1. The measurement of weak AC signals cannot be reduced in voltage or directly rectified, and cannot be carried out using existing measurement methods.

[0004] 2. Weak AC signals are easily interfered with due to their extremely low voltage, resulting in inaccurate measurements.

[0005] 3. The voltage of weak AC signal is too low (such as microvolt (uV) level or millivolt (mV) level), which exceeds the general AC effective measurement range.

[0006] Therefore, there is an urgent need for a circuit for converting weak AC signals into DC signals to overcome the above problems. Utility Model Content

[0007] The purpose of the present application is to provide a circuit for converting weak AC signals into DC signals and a signal conversion device, which can solve at least one technical problem existing in the above-mentioned background technology.

[0008] To achieve the above purpose, the present application provides a circuit for converting weak AC signals into DC signals, comprising:

[0009] A signal amplification module, the signal amplification module is used to amplify the input AC weak signal to obtain an AC amplified signal;

[0010] A frequency gating module, wherein the input end of the frequency gating module is connected to the output end of the signal amplifying module to receive the amplified AC signal, and the frequency gating module is used to filter out harmonics in the amplified AC signal to output a frequency gating signal;

[0011] A waveform conversion module, wherein the input end of the waveform conversion module is connected to the output end of the frequency gating module to receive the frequency gating signal, and the waveform conversion module is used to convert the frequency gating signal into a DC signal;

[0012] An emitter follower module, wherein the input end of the emitter follower module is connected to the output end of the waveform conversion module to receive the DC signal, and the emitter follower module is used to buffer and output the DC signal.

[0013] Optionally, the signal amplification module includes a first-stage amplification circuit and a second-stage amplification circuit, the first-stage amplification circuit includes an operational amplifier U1, an operational amplifier U2, an adjustable resistor R1, a resistor R2 and a resistor R3, the second-stage amplification circuit includes an operational amplifier U3, a resistor R4, a resistor R5, a resistor R6 and a resistor R7, the in-phase input terminal of the operational amplifier U1 is used to input the weak AC signal, the adjustable resistor R1 is connected in series between the inverting input terminal of the operational amplifier U1 and the inverting input terminal of the operational amplifier U2, and the resistor R2 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U1. The non-inverting input terminal of the operational amplifier U2 is grounded, the resistor R3 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U2, the resistor R4 is connected in series between the inverting input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U1, the resistor R5 is connected in series between the non-inverting input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U2, the non-inverting input terminal of the operational amplifier U3 is connected in series with the resistor R6 and then grounded, the resistor R7 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U3, and the output terminal of the operational amplifier U3 is connected to the input terminal of the frequency gating module.

[0014] Optionally, the frequency gating module includes a second-order active bandpass filter circuit, which includes a low-pass filter, a high-pass filter, a resistor R9, a resistor R10, a resistor 12, a capacitor C3 and an operational amplifier U4, the input end of the low-pass filter is connected to the output end of the signal amplification module to receive the AC amplified signal, the output end of the low-pass filter is connected to the input end of the high-pass filter, the output end of the high-pass filter is connected to the in-phase input end of the operational amplifier U4, the inverting input end of the operational amplifier U4 is connected in series with the resistor R9 and then grounded, the resistor R12 is connected in series between the inverting input end and the output end of the operational amplifier U4, the capacitor C3 and the resistor R10 are connected in series between the output end of the operational amplifier U4 and the input end of the high-pass filter, and the output end of the operational amplifier U4 is connected to the input end of the waveform conversion module.

[0015] Optionally, the low-pass filter includes a resistor R8 and a capacitor C1, and the high-pass filter includes a resistor R11 and a capacitor C2, the input end of the resistor R8 is connected to the output end of the signal amplification module, the output end of the resistor R8 is connected to the input end of the capacitor C1 and the input end of the capacitor C2, the output end of the capacitor C1 is grounded, the output end of the capacitor C2 is connected to the in-phase input end of the operational amplifier U4 and the input end of the resistor R11, and the output end of the resistor R11 is grounded.

[0016] Optionally, the waveform transformation module includes an operational amplifier U5, a resistor R13, a resistor R14, a polarity capacitor C5, a diode D1 and a diode D2, the non-inverting input terminal of the operational amplifier U5 is connected to the output terminal of the frequency selection module to receive the frequency selection signal, the resistor R13 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U5, the inverting input terminal of the operational amplifier U5 is connected in series with the resistor R14 and then grounded, the output terminal of the operational amplifier U5 is connected to the cathode of the diode D1 and the anode of the diode D2, the anode of the diode D1 is grounded, the cathode of the diode D2 is connected in series with the polarity capacitor C5, the series branch formed by the diode D2 and the polarity capacitor C5 is connected in parallel with the diode D1, and the cathode of the diode D2 is connected to the input terminal of the emitter follower module.

[0017] Optionally, the diode D1 and the diode D2 are Schottky diodes.

[0018] Optionally, the emitter follower module includes an operational amplifier U6, the in-phase input terminal of the operational amplifier U6 is connected to the output terminal of the waveform conversion module to receive the DC signal, the inverting input terminal of the operational amplifier U6 is connected to the output terminal, and the output terminal of the operational amplifier U6 outputs the DC signal.

[0019] Optionally, the emitter follower module also includes a resistor R15, a resistor R16, a capacitor C6, a capacitor C7 and a capacitor C8, the input end of the resistor R15 and the input end of the capacitor C6 are connected to the output end of the waveform transformation module, the resistor R15 is connected in series with the capacitor C7 and then grounded, the output end of the capacitor C6 is grounded, the output end of the resistor R15 is connected to the in-phase input end of the operational amplifier U6, the output end of the operational amplifier U6 is connected to the input end of the resistor R16, the output end of the resistor R16 is connected to the input end of the capacitor C8, the output end of the capacitor C8 is grounded, and the output end of the resistor R16 outputs the buffered DC signal.

[0020] To achieve the above-mentioned purpose, the present application also provides a signal conversion device, including the aforementioned AC weak signal conversion DC signal circuit.

[0021] In the AC weak signal conversion DC signal circuit of the present application, the AC weak signal is first amplified by a signal amplification module, and then the frequency gating module is used to filter out the harmonics in the AC amplified signal to output a frequency gating signal, thereby obtaining a frequency gating signal within the desired frequency range, and then the waveform conversion module is used to convert the AC frequency gating signal into a smooth DC signal, and then the DC signal is buffered and output through the emitter follower module. The AC weak signal conversion DC signal circuit of the present application can convert an AC weak signal into a DC signal with a higher voltage and no polarity to facilitate measurement. In addition, the present application solves the problem that the AC weak signal has a low voltage and is easily interfered with, exceeds the effective measurement range of the AC, and makes measurement difficult by converting the AC weak signal into a DC signal with a higher voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic block diagram of a circuit for converting weak AC signals into DC signals according to an embodiment of the present application.

[0023] Figure 2 It is a schematic diagram of a circuit for converting weak AC signals into DC signals according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to explain the technical content, structural features, achieved objectives and effects of the present application in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0025] like Figure 1 and Figure 2 As shown, the present application discloses a circuit for converting weak AC signals into DC signals, including a signal amplification module 10 , a frequency selection module 11 , a waveform conversion module 12 and an emitter follower module 13 .

[0026] Among them, the signal amplification module 10 is used to amplify the input weak AC signal to obtain an AC amplified signal; the input end of the frequency selection module 11 is connected to the output end of the signal amplification module 10 to receive the AC amplified signal, and the frequency selection module 11 is used to filter out the harmonics in the AC amplified signal to output a frequency selection signal; the input end of the waveform conversion module 12 is connected to the output end of the frequency selection module 11 to receive the frequency selection signal, and the waveform conversion module 12 is used to convert the frequency selection signal into a DC signal; the input end of the emitter follower module 13 is connected to the output end of the waveform conversion module 12 to receive the DC signal, and the emitter follower module 13 is used to buffer the DC signal output.

[0027] In the AC weak signal conversion DC signal circuit of the present application, the signal amplification module 10 is first used to amplify the AC weak signal, and then the frequency gating module 11 is used to filter out the harmonics in the AC amplified signal to output the frequency gating signal, thereby obtaining the frequency gating signal within the desired frequency range, and then the waveform conversion module 12 is used to convert the AC frequency gating signal into a smooth DC signal, and then the DC signal is buffered and output through the emitter follower module 13. The AC weak signal conversion DC signal circuit of the present application can convert the AC weak signal into a DC signal with a higher voltage and no polarity to facilitate measurement. In addition, the present application solves the problem that the AC weak signal has a low voltage and is easily interfered and exceeds the effective measurement range of the AC, which makes the measurement difficult.

[0028] Specifically, the signal amplification module 10 includes a first-stage amplification circuit 101 and a second-stage amplification circuit 102. The first-stage amplification circuit 101 includes an operational amplifier U1, an operational amplifier U2, an adjustable resistor R1, a resistor R2 and a resistor R3. The second-stage amplification circuit 102 includes an operational amplifier U3, a resistor R4, a resistor R5, a resistor R6 and a resistor R7. The in-phase input terminal of the operational amplifier U1 is used to input a weak AC signal. An adjustable resistor R1 is connected in series between the inverting input terminal of the operational amplifier U1 and the inverting input terminal of the operational amplifier U2. The inverting input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U2. A resistor R2 is connected in series between the terminals, the non-inverting input terminal of the operational amplifier U2 is grounded, a resistor R3 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U2, a resistor R4 is connected in series between the inverting input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U1, a resistor R5 is connected in series between the non-inverting input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U2, the non-inverting input terminal of the operational amplifier U3 is connected in series with a resistor R6 and then grounded, a resistor R7 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U3, and the output terminal of the operational amplifier U3 is connected to the input terminal of the frequency selection module 11.

[0029] By setting the adjustable resistor R1 in the first-stage amplifying circuit 101 , the adjustable resistor R1 can be adjusted to achieve the purpose of adjusting the amplification factor of the signal amplifying module 10 .

[0030] Specifically, the frequency gating module 11 includes a second-order active bandpass filter circuit, which includes a low-pass filter 11a, a high-pass filter 11b, a resistor R9, a resistor R10, a resistor 12, a capacitor C3 and an operational amplifier U4. The input end of the low-pass filter 11a is connected to the output end of the signal amplification module 10 to receive the AC amplified signal, the output end of the low-pass filter 11a is connected to the input end of the high-pass filter 11b, the output end of the high-pass filter 11b is connected to the in-phase input end of the operational amplifier U4, the inverting input end of the operational amplifier U4 is connected in series with the resistor R9 and then grounded, a resistor R12 is connected in series between the inverting input end and the output end of the operational amplifier U4, a capacitor C3 and a resistor R10 are connected in series between the output end of the operational amplifier U4 and the input end of the high-pass filter, and the output end of the operational amplifier U4 is connected to the input end of the waveform conversion module 12.

[0031] The second-order active bandpass filter circuit filters out the harmonics in the AC amplified signal and obtains the required frequency-selected signal of a specific frequency.

[0032] Specifically, the low-pass filter 11a includes a resistor R8 and a capacitor C1, and the high-pass filter 11b includes a resistor R11 and a capacitor C2. The input end of the resistor R8 is connected to the output end of the signal amplification module 10, the output end of the resistor R8 is connected to the input end of the capacitor C1 and the input end of the capacitor C2, the output end of the capacitor C1 is grounded, the output end of the capacitor C2 is connected to the in-phase input end of the operational amplifier U4 and the input end of the resistor R11, and the output end of the resistor R11 is grounded.

[0033] Specifically, the waveform transformation module 12 includes an operational amplifier U5, a resistor R13, a resistor R14, a polarity capacitor C5, a diode D1 and a diode D2. The non-inverting input terminal of the operational amplifier U5 is connected to the output terminal of the frequency selection module 11 to receive the frequency selection signal. The resistor R13 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U5. The inverting input terminal of the operational amplifier U5 is connected in series with the resistor R14 and then grounded. The output terminal of the operational amplifier U5 is connected to the cathode of the diode D1 and the anode of the diode D2. The anode of the diode D1 is grounded. The cathode of the diode D2 is connected in series with the polarity capacitor C5. The series branch formed by the diode D2 and the polarity capacitor C5 is connected in parallel with the diode D1. The cathode of the diode D2 is connected to the input terminal of the emitter follower module 13.

[0034] The diode D1 and the diode D2 rectify the frequency-selected signal, convert the AC signal into a DC signal, and filter it through the polarity capacitor C5 to obtain a DC signal with a smoother waveform.

[0035] Specifically, the diode D1 and the diode D2 are Schottky diodes, which have a lower forward voltage drop, resulting in a better rectification effect.

[0036] Specifically, the emitter follower module 13 includes an operational amplifier U6, the in-phase input terminal of the operational amplifier U6 is connected to the output terminal of the waveform conversion module 12 to receive a DC signal, the inverting input terminal of the operational amplifier U6 is connected to the output terminal, and the output terminal of the operational amplifier U6 outputs a DC signal.

[0037] The operational amplifier U6 is equivalent to a voltage follower, and the output DC signal is substantially equivalent to the input DC signal, but the load carrying capacity of the DC signal is improved, thus playing a buffering role on the output of the DC signal.

[0038] Specifically, the emitter follower module 13 also includes a resistor R15, a resistor R16, a capacitor C6, a capacitor C7 and a capacitor C8. The input end of the resistor R15 and the input end of the capacitor C6 are connected to the output end of the waveform transformation module 12. The resistor R15 and the capacitor C7 are connected in series and then grounded. The output end of the capacitor C6 is grounded. The output end of the resistor R15 is connected to the in-phase input end of the operational amplifier U6. The output end of the operational amplifier U6 is connected to the input end of the resistor R16. The output end of the resistor R16 is connected to the input end of the capacitor C8. The output end of the capacitor C8 is grounded. The output end of the resistor R16 outputs a buffered DC signal.

[0039] The DC signal after output buffering can be directly read by ADC.

[0040] By connecting two groups of RC circuits in the emitter follower module 13, better filtering can be performed, thereby effectively filtering out clutter in the DC signal, making the waveform of the DC signal smoother, which is conducive to better measurement of the DC signal.

[0041] In addition, the present application also provides a signal conversion device, including the aforementioned AC weak signal conversion DC signal circuit.

[0042] The above disclosure is only the preferred embodiment of the present application, which certainly cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the patent scope of the present application are still within the scope covered by the present application.

Claims

1. A circuit for converting weak AC signals into DC signals, characterized in that: include: A signal amplification module, the signal amplification module is used to amplify the input AC weak signal to obtain an AC amplified signal; A frequency gating module, wherein the input end of the frequency gating module is connected to the output end of the signal amplifying module to receive the amplified AC signal, and the frequency gating module is used to filter out harmonics in the amplified AC signal to output a frequency gating signal; A waveform conversion module, wherein the input end of the waveform conversion module is connected to the output end of the frequency gating module to receive the frequency gating signal, and the waveform conversion module is used to convert the frequency gating signal into a DC signal; An emitter follower module, wherein the input end of the emitter follower module is connected to the output end of the waveform conversion module to receive the DC signal, and the emitter follower module is used to buffer and output the DC signal.

2. The AC weak signal conversion DC signal circuit according to claim 1, characterized in that: The signal amplification module includes a first-stage amplification circuit and a second-stage amplification circuit. The first-stage amplification circuit includes an operational amplifier U1, an operational amplifier U2, an adjustable resistor R1, a resistor R2 and a resistor R3. The second-stage amplification circuit includes an operational amplifier U3, a resistor R4, a resistor R5, a resistor R6 and a resistor R7. The in-phase input terminal of the operational amplifier U1 is used to input the weak AC signal. The adjustable resistor R1 is connected in series between the inverting input terminal of the operational amplifier U1 and the inverting input terminal of the operational amplifier U2. The resistor R2 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U1. The non-inverting input terminal of the operational amplifier U2 is grounded, the resistor R3 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U2, the resistor R4 is connected in series between the inverting input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U1, the resistor R5 is connected in series between the non-inverting input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U2, the non-inverting input terminal of the operational amplifier U3 is connected in series with the resistor R6 and then grounded, the resistor R7 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U3, and the output terminal of the operational amplifier U3 is connected to the input terminal of the frequency gating module.

3. The AC weak signal conversion DC signal circuit according to claim 1, characterized in that: The frequency gating module includes a second-order active bandpass filter circuit, which includes a low-pass filter, a high-pass filter, a resistor R9, a resistor R10, a resistor 12, a capacitor C3 and an operational amplifier U4. The input end of the low-pass filter is connected to the output end of the signal amplification module to receive the AC amplified signal, the output end of the low-pass filter is connected to the input end of the high-pass filter, the output end of the high-pass filter is connected to the in-phase input end of the operational amplifier U4, the inverting input end of the operational amplifier U4 is connected in series with the resistor R9 and then grounded, the resistor R12 is connected in series between the inverting input end and the output end of the operational amplifier U4, the capacitor C3 and the resistor R10 are connected in series between the output end of the operational amplifier U4 and the input end of the high-pass filter, and the output end of the operational amplifier U4 is connected to the input end of the waveform conversion module.

4. The AC weak signal conversion DC signal circuit according to claim 3, characterized in that: The low-pass filter includes a resistor R8 and a capacitor C1, and the high-pass filter includes a resistor R11 and a capacitor C2. The input end of the resistor R8 is connected to the output end of the signal amplification module, the output end of the resistor R8 is connected to the input end of the capacitor C1 and the input end of the capacitor C2, the output end of the capacitor C1 is grounded, the output end of the capacitor C2 is connected to the in-phase input end of the operational amplifier U4 and the input end of the resistor R11, and the output end of the resistor R11 is grounded.

5. The AC weak signal conversion DC signal circuit according to claim 1, characterized in that: The waveform conversion module includes an operational amplifier U5, a resistor R13, a resistor R14, a polarity capacitor C5, a diode D1 and a diode D2. The non-inverting input terminal of the operational amplifier U5 is connected to the output terminal of the frequency gating module to receive the frequency gating signal. The resistor R13 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U5. The inverting input terminal of the operational amplifier U5 is connected in series with the resistor R14 and then grounded. The output terminal of the operational amplifier U5 is connected to the cathode of the diode D1 and the anode of the diode D2. The anode of the diode D1 is grounded. The cathode of the diode D2 is connected in series with the polarity capacitor C5. The series branch formed by the diode D2 and the polarity capacitor C5 is connected in parallel with the diode D1. The cathode of the diode D2 is connected to the input terminal of the emitter follower module.

6. The circuit for converting weak AC signals into DC signals as claimed in claim 5, characterized in that: The diode D1 and the diode D2 are Schottky diodes.

7. The circuit for converting weak AC signals into DC signals as claimed in claim 1, characterized in that: The emitter follower module includes an operational amplifier U6, the in-phase input terminal of the operational amplifier U6 is connected to the output terminal of the waveform conversion module to receive the DC signal, the inverting input terminal of the operational amplifier U6 is connected to the output terminal, and the output terminal of the operational amplifier U6 outputs the DC signal.

8. The circuit for converting weak AC signals into DC signals as claimed in claim 6, characterized in that: The emitter follower module also includes a resistor R15, a resistor R16, a capacitor C6, a capacitor C7 and a capacitor C8, the input end of the resistor R15 and the input end of the capacitor C6 are connected to the output end of the waveform conversion module, the resistor R15 is connected in series with the capacitor C7 and then grounded, the output end of the capacitor C6 is grounded, the output end of the resistor R15 is connected to the in-phase input end of the operational amplifier U6, the output end of the operational amplifier U6 is connected to the input end of the resistor R16, the output end of the resistor R16 is connected to the input end of the capacitor C8, the output end of the capacitor C8 is grounded, and the output end of the resistor R16 outputs the buffered DC signal.

9. A signal conversion device, characterized in that: It comprises the circuit for converting weak AC signals into DC signals as claimed in any one of claims 1 to 7.

Images