Alternating current effective value detection circuit and electronic equipment

Abstract

The utility model discloses an alternating current effective value detection circuit and an electronic device, and the circuit comprises an alternating current input isolation unit which is connected with an alternating current input voltage and isolates and processes an alternating current voltage signal into an alternating current small signal; the rectifying and amplifying unit is used for processing the small alternating current signal into an amplified positive half-cycle sinusoidal signal; the filtering unit is connected to the rectifying and amplifying unit and outputs a direct current signal of which the amplitude is the average voltage of the positive half-cycle sinusoidal signal to the voltage following output unit, the output of the voltage following output unit is connected with the input of a voltage division circuit in the single chip microcomputer detection unit, and the output of the voltage division circuit is connected with an analog quantity interface of an MCU (Microprogrammed Control Unit) microprocessor in the single chip microcomputer detection unit; and the MCU microprocessor processes and outputs an alternating current effective value. The circuit converts a sinusoidal signal into a positive half cycle sinusoidal signal, and then obtains a direct current signal with the amplitude being an average value through RC filtering, the direct current signal is sampled by a single chip microcomputer, localization is achieved, and cost is reduced at the same time.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of power electronics, specifically relates to a detection circuit of the effective value of alternating current and electronic equipment. BACKGROUND

[0002] Switching power supply has the demand of input alternating voltage detection and display, generally adopts mutual inductor to isolate and convert alternating input voltage into low voltage alternating signal, then converts alternating signal into direct current effective value through root mean square value chip for single-chip microcomputer detection. With the improvement of localization demand, the root mean square value chip has no localization substitution at present, and the prior art generally adopts functional circuit substitution to realize localization and reduce cost. SUMMARY

[0003] To meet the above requirements, the utility model provides a detection circuit of the effective value of alternating current and electronic equipment, adopts function substitution, realizes localization and reduces cost.

[0004] To achieve the above object, the utility model provides a detection circuit of the effective value of alternating current on one hand, and the technical scheme is:

[0005] A detection circuit of the effective value of alternating current, characterized in that, comprising:

[0006] Alternating input isolation unit, with the alternating current is connected, and the voltage signal of the alternating current is isolated and handled into alternating voltage small signal;

[0007] Rectification amplification unit, the output signal of alternating input isolation unit is connected, and is handled into amplified positive half cycle sinusoidal signal and is exported;

[0008] Filter unit, to smooth the positive half cycle sinusoidal signal of rectification amplification unit output, and the output amplitude is the direct current signal of the average voltage of the positive half cycle sinusoidal signal, and the input end is connected with the output end of rectification amplification unit, and the output end is connected into voltage follower circuit;

[0009] Voltage follower output unit, including operational operational amplifier U2B, the same phase input end of operational amplifier U2B is connected with the output of filter unit;The output of operational operational amplifier U2B is connected to the input end of single-chip microcomputer detection unit;

[0010] Single-chip microcomputer detection unit, including voltage dividing circuit and MCU microprocessor, and the voltage dividing circuit is composed of resistance R12 and resistance R13, one end of resistance R12 is connected with the output of voltage follower output unit, the other end is connected with resistance R13, and the node connected with resistance R12 and resistance R13 is connected with the analog interface of MCU microprocessor, and the other end of resistance R13 is connected with ground.

[0011] Further, the AC input isolation unit comprises a current transformer, resistors R1 and R2, and capacitor C1. The two ends of the primary side of the current transformer are connected to the two ends of the AC signal through resistors R1 and R2, respectively. One end of the secondary side of the current transformer is grounded, and the other end is coupled to the rectification and amplification unit through capacitor C1.

[0012] Further, the rectification and amplification unit comprises:

[0013] a two-stage operational amplifier circuit;

[0014] The first-stage operational amplifier circuit comprises resistors R5, R6, and R7, diodes V1 and V2, and operational amplifier N1A. The non-inverting input terminal of the operational amplifier N1A is grounded. The inverting input terminal of the operational amplifier N1A is connected to capacitor C1 in the AC input isolation unit through resistor R5. The output of the operational amplifier N1A is connected to the cathode of diode V1 and the anode of diode V2, respectively. The anode of diode V1 is connected to the inverting input terminal of the operational amplifier N1A through resistor R6. The cathode of diode V2 is connected to the inverting input terminal of the operational amplifier N1A through resistor R7.

[0015] The second-stage operational amplifier circuit comprises resistors R8 and R9, and operational amplifier N1B.

[0016] One end of resistor R8 is connected to the anode of diode V1 in the first-stage operational amplifier circuit, and the other end is connected to the inverting input terminal of operational amplifier N1B. The non-inverting input terminal of operational amplifier N1B is connected to the cathode of diode V2 in the first-stage operational amplifier circuit. Resistor R9 is connected between the inverting input terminal and the output terminal of operational amplifier N1B.

[0017] Further, the rectification and amplification unit further comprises capacitors C2, C4, C6, and C7.

[0018] Capacitor C2 is connected between the inverting input terminal and the non-inverting input terminal of operational amplifier N1A. Capacitor C2 is also connected between the inverting input terminal and the output terminal of operational amplifier N1A. Capacitor C6 is connected between the inverting input terminal and the non-inverting input terminal of operational amplifier N1B. Capacitor C7 is connected between the inverting input terminal and the output terminal of operational amplifier N1B.

[0019] Further, the filter unit comprises at least one resistor and one capacitor. One end of the resistor is connected to the output terminal of the rectification and amplification unit, and the capacitor is connected between the output terminal of the resistor and the ground.

[0020] Further, there is a filter capacitor C12 connected in parallel across resistor R13 in the voltage dividing circuit of the single-chip microcomputer detection unit.

[0021] The utility model discloses still provide a kind of electronic equipment on the other hand, including the detection circuit of effective value of alternating current of any one described above.

[0022] The utility model has the beneficial effects

[0023] The technical scheme of the utility model mainly adopts operational amplifier processing circuit to rectify and amplify alternating sampling signal, rectifies and converts alternating sinusoidal signal into positive half-cycle sinusoidal signal, then obtains direct current signal with average voltage amplitude through RC filter circuit, for single-chip microcomputer sampling, realizes localization, and reduces cost simultaneously. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is the circuit schematic diagram of the embodiment of the utility model. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantage of the utility model more clearly, the following is combined with drawing and embodiment, and the utility model is further explained in detail. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not used to limit the utility model. In addition, the technical features involved in each embodiment of the utility model described below can be combined with each other as long as they do not conflict with each other.

[0026] The working principle of the utility model is explained as follows in combination with the embodiment shown in the drawing: Figure 1

[0027] In the embodiment of the utility model's detection circuit of effective value of alternating current,

[0028] The alternating current input isolation unit includes a current transformer, resistors R1 and R2, and a capacitor C1. The two ends of the primary side of the current transformer are connected to the two ends of the alternating current signal through resistors R1 and R2, respectively. One end of the secondary side of the current transformer is grounded, and the other end is coupled to the rectification and amplification unit circuit through the capacitor C1, i.e. the alternating voltage signal is isolated and processed as an alternating voltage small signal input to the rectification and amplification unit circuit.

[0029] The rectification and amplification unit contains two-stage operational amplifier circuit.

[0030] The first-stage operational amplifier circuit includes resistors R5, R6 and R7, diodes V1 and V2, and an operational amplifier N1A. The non-inverting input terminal of the operational amplifier N1A is grounded, and the inverting input terminal is connected to the capacitor C1 in the alternating current input isolation unit through the resistor R5. The output of the operational amplifier N1A is connected to the cathode of the diode V1 and the anode of the diode V2, respectively. The anode of the diode V1 is connected to the inverting input terminal of the operational amplifier N1A through the resistor R6. The cathode of the diode V2 is connected to the inverting input terminal of the operational amplifier N1A through the resistor R7.​

[0031] The second stage operational amplifier circuit comprises a resistor R8, a resistor R9, an operational amplifier N1B, one end of the resistor R8 being connected to the anode of the diode V1 in the operational amplifier N1A of the first stage operational amplifier circuit, the other end being connected to the inverting input terminal of the operational amplifier N1B; the non-inverting input terminal of the operational amplifier N1B being connected to the cathode of the diode V2 in the first stage operational amplifier circuit; the resistor R9 being connected between the inverting input terminal and the output terminal of the operational amplifier N1B.

[0032] The filter unit is a second order RC low-pass filter circuit, which comprises a first stage RC low-pass filter circuit composed of a resistor R10 and a capacitor C8, and another stage RC low-pass filter circuit composed of a resistor R11 and a capacitor C9, the output terminal of the operational amplifier N1B being connected to the input terminal of the resistor R10, and the output terminal of the resistor R11 being connected to the voltage follower circuit.

[0033] The voltage follower output unit comprises an operational amplifier U2B, the output of the operational amplifier U2B being connected to the output of the filter circuit, i.e. the output of the resistor R11; the output of the operational amplifier U2B being connected to the input terminal of the single-chip microcomputer detection unit.

[0034] The single-chip microcomputer detection unit comprises a voltage dividing circuit and a MCU microprocessor, the voltage dividing circuit being composed of a resistor R12 and a resistor R13, one end of the resistor R12 being connected to the output of the voltage follower circuit, i.e. the output terminal of the operational amplifier U2B, the other end being connected to the resistor R13, the node connected to the resistor R12 and the resistor R13 being connected to the analog quantity interface of the MCU microprocessor, and the other end of the resistor R13 being connected to the ground.

[0035] In the actual example, the small signal of the output AC voltage of the AC input isolation unit circuit is input to the inverting input terminal of the operational amplifier N1A of the rectification and amplification unit through the resistor R5;

[0036] When the AC signal is in the positive half cycle, the branch composed of the resistor R6 and the diode V1 between the inverting input terminal and the output terminal of the operational amplifier N1A is turned on, and the output negative half wave signal is input to the inverting input terminal of the operational amplifier N1B through the resistor R8, and the output of the operational amplifier N1B is a positive half wave signal after being inverted and amplified;

[0037] When the AC signal is in the negative half cycle, the branch composed of the resistor R7 and the diode V2 between the inverting input terminal and the output terminal of the operational amplifier N1A is turned on, and the output positive half wave signal is input to the non-inverting input terminal of the operational amplifier N1B; after the non-inverting amplification, the output terminal of the operational amplifier N1B is also a positive half wave signal;

[0038] That is, the small signal of the output AC voltage of the AC input isolation unit circuit is input to the rectification and amplification unit through the resistor R5, and then processed to become an amplified positive half cycle sine signal output.

[0039] The second-order RC low-pass filter circuit filters the positive half-cycle sinusoidal signal output by the rectifier amplifier unit circuit, outputting a smooth DC voltage signal with an amplitude equal to the average AC voltage. This signal is then isolated by the voltage follower output unit and connected to the voltage divider circuit of the microcontroller detection unit. The output of the voltage divider circuit is then connected to the analog interface of the MCU microprocessor.

[0040] In this embodiment, taking the AC input voltage Vac as an example, in the circuit, if R1 = R2, R6 = R7 = R8 = R9, the AC voltage Vac outputs a sinusoidal current signal after passing through the AC input isolation circuit, and its effective current value is:

[0041] I = Vac / (R1 + R2) (1)

[0042] After passing through the rectifier and amplifier circuit, the positive half-cycle sinusoidal signal, i.e., the sinusoidal half-wave voltage signal V, is obtained. 半波 At a frequency of 100Hz, the peak value of the half-wave voltage signal is:

[0043] V 半波 =I*R6 (2)

[0044] After two stages of filtering, the DC voltage V is obtained. dc， Its average value is:

[0045] V dc =V 半波 ÷(π / 2) (3)

[0046] After impedance isolation by a voltage follower, the voltage is further divided by a voltage divider circuit to obtain the final input voltage V to the microprocessor MCU analog interface. test, Its value is:

[0047] V test =Vdc*R13 / (R12+R13) (4)

[0048] Substituting formulas (1), (2), and (3) into formula (4), we get:

[0049] V test =Vac*R6*R13 / ((π / 2)(R1+R2)(R12+R13)), since R1, R2, R6, R12, and R13 are all known values, that is, V test The analog input V of the microprocessor (MCU) is linearly related to the AC input Vac. test After obtaining the value, multiplying it by the correlation coefficient corresponding to the linear relationship yields the effective value of the AC input voltage Vac.

[0050] Optionally, in the embodiment, the rectifier amplifier circuit further includes capacitors C2, C4, C6, and C7. Capacitor C2 is connected between the inverting input and non-inverting input of operational amplifier N1A; capacitor C2 is connected between the inverting input and output of operational amplifier N1A; capacitor C6 is connected between the inverting input and non-inverting input of operational amplifier N1B; and capacitor C7 is connected between the inverting input and output of operational amplifier N1B. A filter capacitor C12 is connected in parallel across resistor R13 in the voltage divider circuit. These capacitors reduce local high-frequency amplification, prevent circuit self-oscillation, or remove high-frequency interference, thus stabilizing the circuit operation.

[0051] The above description is only a preferred embodiment of this utility model. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principle of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the concept and technical solution of the utility model to other occasions without modification, should all be considered within the protection scope of this utility model.

Claims

1. A circuit for detecting the effective value of alternating current, characterized in that, include: An AC input isolation unit is connected to the AC power supply and isolates the AC voltage signal into a small AC voltage signal. The rectifier and amplifier unit receives the output signal from the AC input isolation unit, processes it into an amplified positive half-cycle sine wave signal, and then outputs it. The filtering unit smooths the positive half-cycle sinusoidal signal output by the rectifier amplifier unit and outputs a DC signal with an amplitude equal to the average voltage of the positive half-cycle sinusoidal signal. Its input terminal is connected to the output terminal of the rectifier amplifier unit, and its output terminal is connected to the voltage follower output unit. The voltage follower output unit includes an operational amplifier U2B, the non-inverting input of which is connected to the output of the filter unit; the output of the operational amplifier U2B is connected to the input of the microcontroller detection unit. The microcontroller detection unit includes a voltage divider circuit and an MCU microprocessor. The voltage divider circuit consists of resistors R12 and R13. One end of resistor R12 is connected to the output of the voltage follower output unit, and the other end is connected to resistor R13. The node where resistors R12 and R13 are connected is connected to the analog interface of the MCU microprocessor, and the other end of resistor R13 is grounded.

2. The detection circuit according to claim 1, characterized in that, The AC input isolation unit includes a current transformer, resistors R1 and R2, and capacitor C1. The two ends of the primary side of the current transformer are connected to the two ends of the AC signal through resistors R1 and R2, respectively. One end of the secondary side of the current transformer is grounded, and the other end is coupled to the rectifier and amplifier unit through capacitor C1.

3. The detection circuit according to claim 1, characterized in that, The rectifier amplification unit includes: a two-stage operational amplifier circuit; The first-stage operational amplifier circuit includes resistors R5, R6, and R7, diodes V1 and V2, and operational amplifier N1A. The non-inverting input of operational amplifier N1A is grounded, and its inverting input is connected to capacitor C1 in the AC input isolation unit through resistor R5. The output of operational amplifier N1A is connected to the cathode of diode V1 and the anode of diode V2, respectively. The anode of diode V1 is connected to the inverting input of operational amplifier N1A through resistor R6; the cathode of diode V2 is connected to the inverting input of operational amplifier N1A through resistor R7. The second-stage operational amplifier circuit includes resistors R8 and R9, and operational amplifier N1B. One end of resistor R8 is connected to the anode of diode V1 in the first-stage operational amplifier circuit, and the other end is connected to the inverting input terminal of N1B of the operational amplifier; the non-inverting input terminal of N1B of the operational amplifier is connected to the cathode of diode V2 in the first-stage operational amplifier circuit; resistor R9 is connected between the inverting input terminal and the output terminal of N1B of the operational amplifier.

4. The detection circuit according to claim 3, characterized in that, The rectifier amplification unit also includes: capacitor C2, capacitor C4, capacitor C6, and capacitor C7; Capacitor C2 is connected between the inverting input and non-inverting input of operational amplifier N1A; capacitor C2 is connected between the inverting input and output of operational amplifier N1A; capacitor C6 is connected between the inverting input and non-inverting input of operational amplifier N1B; capacitor C7 is connected between the inverting input and output of operational amplifier N1B.

5. The detection circuit according to claim 1, characterized in that, The filter unit contains at least one resistor and one capacitor: one end of the resistor is connected to the output terminal of the rectifier amplifier unit, and the capacitor is connected between the output terminal of the resistor and ground.

6. The detection circuit according to claim 1, characterized in that, In the voltage divider circuit of the microcontroller detection unit, a filter capacitor C12 is connected in parallel across the two ends of resistor R13.

7. An electronic device, characterized in that, It includes the AC effective value detection circuit as described in any one of claims 1-6.

Images