CN109030937B - Power frequency detection circuit, air conditioner and grid-connected system - Google Patents
Power frequency detection circuit, air conditioner and grid-connected system Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The application relates to a power frequency detection circuit, an air conditioner and a grid-connected system, which comprises a differential anti-interference circuit, a hysteresis calibration circuit and a processor which are sequentially connected, wherein the differential anti-interference circuit is used for accessing mains supply, the differential anti-interference circuit is used for carrying out isolation processing on accessed sinusoidal voltage signals, and converting the sinusoidal voltage signals after the isolation processing into square wave voltage signals and sending the square wave voltage signals to the hysteresis calibration circuit; the hysteresis calibration circuit is used for calibrating the frequency of the received square wave voltage signal and controlling the frequency within a preset precision range and then sending the frequency to the processor; the processor obtains the power frequency according to the received processed square wave voltage signal. The differential immunity circuit is used for carrying out differential operation on the accessed mains supply to eliminate interference, accurate conversion from a voltage sine wave to a square wave is realized, the frequency of the square wave signal is calibrated through the hysteresis calibration circuit, the frequency is enabled to be within a preset precision range and is sent to the processor to be detected, the accuracy of power frequency detection is improved, and the normal operation of an object to be controlled is ensured.
Description
Technical Field
The application relates to the technical field of power frequency detection, in particular to a power frequency detection circuit, an air conditioner and a grid-connected system.
Background
When the power frequency exceeds the specified frequency range, the working state of the corresponding controlled device can also change correspondingly, for example, when the power frequency is within the range A, the corresponding controlled device can normally operate, and when the frequency exceeds the range A, the corresponding controlled device stops working.
The conventional power frequency detection circuit is extremely easy to interfere in the sampling process due to the influence of various external factors, so that the sampled power frequency is inaccurate, and the phenomenon of shutdown protection of correspondingly controlled devices is easy to influence the normal operation of an object to be controlled due to the external interference, so that the detection precision of the conventional power frequency detection circuit is low.
Disclosure of Invention
In view of the above, it is necessary to provide a power frequency detection circuit, an air conditioner, and a grid-connected system with high detection accuracy.
The power supply frequency detection circuit comprises a differential immunity circuit, a hysteresis calibration circuit and a processor which are connected in sequence, wherein the differential immunity circuit is used for accessing mains supply,
the differential immunity circuit is used for carrying out isolation processing on the accessed sinusoidal voltage signals, converting the sinusoidal voltage signals after the isolation processing into square wave voltage signals, and sending the square wave voltage signals to the hysteresis calibration circuit;
the hysteresis calibration circuit is used for receiving the square wave voltage signal, calibrating the frequency of the square wave voltage signal and controlling the frequency within a preset precision range, and sending the processed square wave voltage signal to the processor;
and the processor obtains the power supply frequency according to the received processed square wave voltage signal.
An air conditioner comprises an air conditioning unit and the power frequency detection circuit.
A grid-connected system comprises a power grid, an air conditioning unit and the power frequency detection circuit.
The power frequency detection circuit, the air conditioner and the grid-connected system are characterized in that the differential immunity circuit is used for conducting isolation processing on the accessed sinusoidal voltage signals, converting the sinusoidal voltage signals after the isolation processing into square wave voltage signals, and sending the square wave voltage signals to the hysteresis calibration circuit; the hysteresis calibration circuit is used for receiving the square wave voltage signal, calibrating the frequency of the square wave voltage signal and controlling the frequency within a preset precision range, and sending the processed square wave voltage signal to the processor; the processor obtains the power frequency according to the received processed square wave voltage signal. The differential immunity circuit is used for carrying out differential operation on the accessed mains supply to eliminate interference, accurate conversion from a voltage sine wave to a square wave is realized, the frequency of the square wave signal is calibrated through the hysteresis calibration circuit, the frequency is enabled to be within a preset precision range and is sent to the processor to be detected, the accuracy of power frequency detection is improved, and the normal operation of an object to be controlled is ensured.
Drawings
FIG. 1 is a block diagram of a power frequency detection circuit in one embodiment;
FIG. 2 is a block diagram of a power frequency detection circuit according to another embodiment;
FIG. 3 is a schematic diagram of a differential operational amplifier circuit in one embodiment;
FIG. 4 is a schematic diagram of a differential operational amplifier circuit according to another embodiment;
FIG. 5 is a schematic diagram of a differential operational amplifier circuit according to another embodiment;
FIG. 6 is a schematic diagram of a sine wave conversion square wave circuit in one embodiment;
FIG. 7 is a schematic diagram of a sine wave conversion square wave circuit in another embodiment;
FIG. 8 is a schematic diagram of a sine wave conversion square wave circuit in yet another embodiment;
FIG. 9 is a schematic diagram of a hysteresis calibration circuit in one embodiment;
FIG. 10 is a frequency accuracy bandwidth diagram in one embodiment;
FIG. 11 is a schematic diagram of a hysteresis calibration circuit in another embodiment;
FIG. 12 is a schematic diagram of a sine wave translation square wave circuit and hysteresis calibration circuit configuration in one embodiment.
Detailed Description
An application scenario of the present application is: when the frequency of the photovoltaic air conditioner power supply exceeds the frequency range specified by GB/T15945, the working state of the unit can meet the requirements of Table 1. When the inverter cuts out the grid due to the problem of frequency response, the inverter can restart the operation when the grid frequency is restored to the grid frequency at which the operation is permitted.
TABLE 1
| Frequency range | Inverter response |
| Below 48Hz | Stop running within 0.2s |
| 48～49.5Hz | Stopping the operation after 10min |
| 49.5～50.2Hz | Normal operation |
| 50.2～50.5Hz | Stopping operation after 2min, and stopping operation at the moment, and not allowing grid connection |
| Above 50.5Hz | Stopping supplying power to the power grid within 0.2s, and stopping running at the moment, and not allowing grid connection |
According to the standard requirements, after the photovoltaic air conditioner is electrified, the system enters an initialization mode, and can initially enter a power grid frequency detection task, and when the frequency exceeds the range of 49.5-50.2 Hz, the system stops working. Therefore, a high-precision power frequency detection circuit design is critical.
In one embodiment, as shown in fig. 1, a power frequency detection circuit includes a differential immunity circuit 110, a hysteresis calibration circuit 120 and a processor 130, which are sequentially connected, wherein the differential immunity circuit 110 is used for accessing to the mains, the differential immunity circuit 110 is used for performing isolation processing on an accessed sinusoidal voltage signal, converting the sinusoidal voltage signal after the isolation processing into a square wave voltage signal, and transmitting the square wave voltage signal to the hysteresis calibration circuit 120; the hysteresis calibration circuit 120 is configured to receive a square wave voltage signal, calibrate the frequency of the square wave voltage signal and control the frequency within a preset precision range, and send the processed square wave voltage signal to the processor 130; the processor 130 derives a power supply frequency from the received processed square wave voltage signal.
Specifically, in this embodiment, a photovoltaic air conditioner power supply is taken as an example for explanation, the preset precision range is 0.01Hz, and the power frequency detection circuit realizes high-precision detection, and mainly comprises two parts: the differential immunity circuit realizes accurate conversion from a voltage sine wave to a square wave under the condition of a strong coupling electric field, the hysteresis calibration circuit realizes automatic calibration of power frequency, so that the frequency is in a preset precision range and is sent to a processor for detection, the accurate response of the power frequency of the photovoltaic air conditioner can be realized, the detection range of 49.5-50.2 Hz of the photovoltaic air conditioner is met, the frequency error protection of the photovoltaic air conditioner due to inaccurate frequency detection is avoided, the frequency precision is up to 0.01Hz, and the precision is improved by 10 times compared with that of a traditional power frequency detection circuit.
The power supply frequency detection circuit is used for carrying out isolation processing on the accessed sinusoidal voltage signals, converting the sinusoidal voltage signals subjected to the isolation processing into square wave voltage signals and sending the square wave voltage signals to the hysteresis calibration circuit; the hysteresis calibration circuit is used for receiving the square wave voltage signal, calibrating the frequency of the square wave voltage signal and controlling the frequency within a preset precision range, and sending the processed square wave voltage signal to the processor; the processor obtains the power frequency according to the received processed square wave voltage signal. The differential immunity circuit is used for carrying out differential operation on the accessed mains supply, eliminating interference, realizing accurate conversion from a voltage sine wave to a square wave, calibrating the frequency of the square wave signal by the hysteresis calibration circuit, enabling the frequency to be in a preset precision range and sending the frequency to the processor for detection, improving the accuracy of power frequency detection, realizing accurate response of the power frequency of an object to be controlled, avoiding error protection of the frequency due to inaccurate frequency detection of the object to be controlled, and guaranteeing normal operation of the object to be controlled.
In one embodiment, as shown in fig. 2, the differential immunity circuit includes a differential operational amplification circuit 112 and a sine wave conversion square wave circuit 114, the differential operational amplification circuit 112 is connected with the sine wave conversion square wave circuit 114, the sine wave conversion square wave circuit 114 is connected with a hysteresis calibration circuit, and the differential operational amplification circuit 112 is used for performing isolation processing on an accessed sine voltage signal and transmitting the sine voltage signal after the isolation processing to the sine wave conversion square wave circuit 114; the sine wave conversion square wave circuit 114 is configured to receive the isolated sine voltage signal, convert the isolated sine voltage signal into a square wave voltage signal, and send the square wave voltage signal to the hysteresis calibration circuit.
Specifically, the differential immunity circuit is composed of two-stage negative feedback operation circuits, the differential operation amplification circuit carries out differential operation on the accessed sinusoidal voltage signals, interference is eliminated, isolation and conditioning effects of 220V sinusoidal voltage signals are achieved, high voltage is decoupled, electric signals are enhanced, and immunity of the differential immunity circuit is enhanced. The sine wave conversion square wave circuit realizes 220V sine voltage signal conversion function, and is convenient for frequency detection of a subsequent processor.
In one embodiment, the differential operational amplification circuit comprises a first operational amplifier, a first resistor, a second resistor, a third resistor and a first negative feedback resistor, wherein the first resistor, the second resistor and the third resistor are connected in series to be connected with a mains power zero line, the in-phase input end of the first operational amplifier is connected with a mains power live wire and a first bias power supply, the first end of the first negative feedback resistor is connected with the inverting input end of the first operational amplifier, the second end of the first negative feedback resistor is connected with the output end of the first operational amplifier, the output end of the first operational amplifier is connected with a sine wave conversion square wave circuit, and the third resistor is connected with the first end of the first negative feedback resistor.
Specifically, as shown in fig. 3, the differential operational amplifier circuit, which is a first-stage negative feedback operational circuit, is composed of a first operational amplifier U1, a first resistor R51, a second resistor R50, a third resistor R49, a first negative feedback resistor R28, and a first bias power supply 1.5V, wherein a first end of the first resistor R51 is connected to a mains supply zero line V N Pin 10 of the first operational amplifier is a non-inverting input end, pin 9 is an inverting input end, pin 8 is an output end, and the non-inverting input end pin 10 of the first operational amplifier is connected with a commercial power fire wire V L And a first bias power supply V1.5V, in this embodiment, the model number of the first operational amplifier is U2-C, and the transfer function of the differential operational amplifier circuit is:
the differential operation of the zero line voltage and the live line voltage is realized through the transfer function, the interference is eliminated, and the voltage coefficient is calculatedPower supply V LN ＝V PP sin (ωt+θ), where V PP Peak voltage of sinusoidal voltage, V AD_V_RB ＝1.5+KV PP sin (ωt+θ), realizes isolation and conditioning of 220V sinusoidal voltage signals, decouples high voltage, enhances electrical signals and enhances immunity.
In one embodiment, the differential operational amplifier circuit further comprises a first balance resistor, a second balance resistor and a third balance resistor which are connected in series, wherein the other end of the first balance resistor is connected with a mains supply fire wire, and the other end of the third balance resistor is connected with the non-inverting input end of the first operational amplifier.
Specifically, as shown in fig. 4, the first balancing resistor is R96, the second balancing resistor is R95, and the third balancing resistor is R94, where the first balancing resistor, the second balancing resistor and the third balancing resistor are used to make the loads at two ends of the first operational amplifier symmetrical, reduce errors such as zero drift, and improve signal output accuracy.
In one embodiment, the differential operational amplifier circuit further comprises a first pull-up resistor and a first capacitor, wherein the first pull-up resistor and the first capacitor are connected in parallel, one end of the first pull-up resistor and one end of the first capacitor are commonly connected with the non-inverting input end of the first operational amplifier, and the other end of the first pull-up resistor and the first capacitor are connected with the first bias power supply.
Specifically, as shown in fig. 5, the non-inverting input end of the first operational amplifier is connected to the first bias power supply, so that the output voltage is positive voltage, the electric signal is enhanced, the first pull-up resistor R27 and the first capacitor C33 are connected in parallel and used for filtering clutter in the first bias power supply, so that external interference is further eliminated, and the stability of the input signal is ensured.
In one embodiment, the differential operational amplifier circuit further comprises a second capacitor connected in parallel with the first negative feedback resistor. Specifically, a second capacitor C34 connected in parallel with the first negative feedback resistor R28 is added as lead compensation, so that self-oscillation can be eliminated.
In one embodiment, as shown in fig. 6, the sine wave conversion square wave circuit includes a second operational amplifier, a second negative feedback resistor and a fourth resistor, wherein a first end of the second negative feedback resistor is connected to an inverting input end of the second operational amplifier, a second end of the second negative feedback resistor is connected to an output end of the second operational amplifier, an output end of the second operational amplifier is connected to a hysteresis calibration circuit, a first end of the fourth resistor is grounded, a second end of the fourth resistor is connected to an inverting input end of the second operational amplifier, and a non-inverting input end of the second operational amplifier is connected to a differential operational amplifier circuit.
Specifically, the non-inverting input end of the second operational amplifier is connected to the output end of the first operational amplifier circuit, the second-stage negative feedback operational circuit, that is, the sine wave conversion square wave circuit, is composed of a second operational amplifier U2, a second negative feedback resistor R60 and a fourth resistor R47, pin 1 of the second operational amplifier U15 is an output end, pin 2 is an inverting input end, pin 3 is a non-inverting input end, pin 8 is used for accessing an external power supply, pin 4 is grounded, in this embodiment, the model of the second operational amplifier is U15-a, and the transfer function of the sine wave conversion square wave circuit is:
the 220V sinusoidal voltage signal is converted into square wave voltage signal through the sinusoidal wave conversion square wave circuit, so that the frequency detection of the processor is facilitated.
In one embodiment, as shown in fig. 7, the sine wave conversion square wave circuit further includes a second pull-up resistor and a third capacitor, where the second pull-up resistor and the third capacitor are connected in parallel, and one end of the second pull-up resistor is connected to the non-inverting input terminal of the second operational amplifier, and the other end of the second pull-up resistor is grounded.
Specifically, the second pull-up resistor R52 and the third capacitor C50 are connected in parallel and are used for filtering clutter in the output voltage of the differential operational amplifier circuit, so that interference is further eliminated, and stability of an input signal is guaranteed.
Further, as shown in fig. 8, the sine wave conversion square wave circuit further includes a first current limiting resistor R48, a first end of the first current limiting resistor R48 is connected to the differential operational amplification circuit, a second end of the first current limiting resistor R48 is connected to the non-inverting input end of the second operational amplifier, and the first current limiting resistor R48 is used for limiting the current of the branch circuit, so as to prevent the components connected in series from being burnt out due to excessive current, and improve the safety of the sine wave conversion square wave circuit.
In one embodiment, as shown in fig. 8, the sine wave conversion square wave circuit further includes a fourth capacitor, which is connected in parallel with the second negative feedback resistor. Specifically, adding a fourth capacitor C41 in parallel with the second negative feedback resistor R60 as the lead compensation can eliminate self-oscillation.
In one embodiment, as shown in fig. 9, the hysteresis calibration circuit includes a third operational amplifier, a fifth resistor, and a positive feedback resistor, wherein a first end of the fifth resistor is connected to the sine wave conversion square wave circuit, a second end of the fifth resistor is connected to a non-inverting input end of the third operational amplifier, an inverting input end of the third operational amplifier is connected to the second bias power supply, a first end of the positive feedback resistor is connected to the non-inverting input end of the third operational amplifier, a second end of the positive feedback resistor is connected to an output end of the third operational amplifier, and an output end of the third operational amplifier is connected to the processor.
Specifically, the first end of the fifth resistor is connected with the output end of the second operational amplifier of the sine wave conversion square wave circuit, the hysteresis calibration circuit adopts a positive-phase input positive feedback hysteresis upper and lower threshold comparison design, and the frequency deviation and waveform shaping of square wave voltage signals are calibrated in real time, so that the frequency accuracy is calibrated within 0.01 Hz. The hysteresis calibration circuit is composed of a third operational amplifier U3, a fifth resistor R65 and a positive feedback resistor R14, wherein a pin 5 of the third operational amplifier U503 is a non-inverting input end, a pin 6 is an inverting input end, and a pin 7 is an output end, in this embodiment, the model of the third operational amplifier is U503-B, and the transfer function is:
according to the output voltage V OUT Can be used to determine the upper threshold voltage V respectively T+ And a lower threshold voltage V T- The method comprises the following steps of:
the frequency accuracy is determined by the hysteresis bandwidth as in fig. 10, when the frequency f 0 Greater than (f) 0 +0.005) Hz, the op-amp U503-B outputs a high level at a frequency f 0 Less than (f) 0 -0.005) Hz, the operational amplifier U503-B outputs a low level, and the frequency precision of the shaped square wave is automatically adjusted within 0.01Hz, so that the high precision requirement is met. And the third operational amplifier is connected with a second bias power supply, so that the amplitude of the high level and the low level of the square wave is biased by 1.5V, the amplitude is in the range of 0-3V, and the voltage input range of the processor is met.
Further, as shown in fig. 11, the hysteresis calibration circuit further includes a second current limiting resistor R61, a first end of the second current limiting resistor R61 is connected to a second bias power supply, a second end of the second current limiting resistor R61 is connected to an inverting input end of the third operational amplifier, and the second current limiting resistor R61 is used for limiting the current of the branch circuit, so as to prevent the components connected in series from being burnt out due to excessive current, and improve the safety of the hysteresis calibration circuit.
Further, as shown in fig. 11, the hysteresis calibration circuit further includes a third pull-up resistor R16, where a first end of the third pull-up resistor R16 is connected to an output end of the third operational amplifier, and a second end of the third pull-up resistor R16 is connected to an external power supply, and the pull-up clamps an uncertain signal at a high level through a resistor, and the resistor plays a role of current limiting.
In a detailed embodiment, as shown in fig. 12, a schematic structure of the connection between the sine wave conversion square wave circuit and the hysteresis calibration circuit is shown, and the specific components and connection relationships are already described in the above description, and are not described herein.
The power frequency detection circuit can realize that the frequency of the photovoltaic air conditioner is in the range of 49.5-50.2 Hz, calibrate and detect in real time, control the precision at 0.01Hz, and improve the precision by 10 times compared with the traditional power frequency detection circuit, thereby meeting the standard requirement of the photovoltaic air conditioner.
In one embodiment, an air conditioner comprises an air conditioning unit and the power frequency detection circuit.
Specifically, the output end of the power frequency detection circuit is connected with an air conditioning unit, the air conditioning unit responds correspondingly according to the power frequency-unit response corresponding relation and the power frequency obtained by the power frequency detection circuit, in this embodiment, the air conditioner is taken as a photovoltaic air conditioner for illustration, and the power frequency-unit response corresponding relation is shown in the table 1 above, so that the standard requirement of the photovoltaic air conditioner is met.
According to the air conditioner, the differential operation is carried out on the accessed commercial power through the differential immunity circuit, interference is eliminated, accurate conversion from a voltage sine wave to a square wave is achieved, the frequency of the square wave signal is calibrated through the hysteresis calibration circuit, the frequency is enabled to be within the range of preset precision and is sent to the processor for detection, the accuracy of power frequency detection is improved, accurate response of an air conditioning unit can be achieved, frequency error protection caused by inaccurate frequency detection of the air conditioner is avoided, and normal operation of the air conditioner is guaranteed.
In one embodiment, a grid-connected system includes a power grid, an air conditioning unit, and the power frequency detection circuit.
Specifically, the output end of the power frequency detection circuit is connected with an air conditioning unit, the air conditioning unit is connected with a power grid, the air conditioning unit responds correspondingly according to the power frequency-unit response corresponding relation and the power frequency obtained by the power frequency detection circuit, and the power grid is correspondingly integrated or cut out according to the response condition.
According to the grid-connected system, the differential operation is carried out on the accessed commercial power through the differential anti-interference circuit, interference is eliminated, accurate conversion from a voltage sine wave to a square wave is achieved, the frequency of the square wave signal is calibrated through the hysteresis calibration circuit, the frequency is enabled to be within a preset precision range and transmitted to the processor for detection, the accuracy of power frequency detection is improved, accurate response of an air conditioning unit can be achieved, frequency error protection caused by inaccurate frequency detection of the air conditioner is avoided, normal operation of the air conditioner is guaranteed, and the air conditioner can be correspondingly incorporated into or cut out of a power grid according to the operation condition of the air conditioner.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples represent only a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.
Claims (11)
1. The power supply frequency detection circuit is characterized by comprising a differential anti-interference circuit, a hysteresis calibration circuit and a processor which are connected in sequence, wherein the differential anti-interference circuit is used for accessing mains supply,
the differential immunity circuit is used for carrying out isolation processing on the accessed sinusoidal voltage signals, converting the sinusoidal voltage signals after the isolation processing into square wave voltage signals, and sending the square wave voltage signals to the hysteresis calibration circuit;
the hysteresis calibration circuit is used for receiving the square wave voltage signal, calibrating the frequency of the square wave voltage signal and controlling the frequency within a preset precision range, wherein the frequency precision of the square wave voltage signal is determined by the frequency precision of the hysteresis calibration circuit, and the processed square wave voltage signal is sent to the processor; the hysteresis calibration circuit comprises a third operational amplifier, a fifth resistor and a positive feedback resistor, wherein a first end of the fifth resistor is connected with a sine wave conversion square wave circuit, a second end of the fifth resistor is connected with a non-inverting input end of the third operational amplifier, an inverting input end of the third operational amplifier is connected with a second bias power supply, a first end of the positive feedback resistor is connected with the non-inverting input end of the third operational amplifier, a second end of the positive feedback resistor is connected with an output end of the third operational amplifier, and an output end of the third operational amplifier is connected with the processor;
and the processor obtains the power supply frequency according to the received processed square wave voltage signal.
2. The power frequency detection circuit of claim 1, wherein the differential immunity circuit comprises a differential operational amplifier circuit and a sine wave conversion square wave circuit, the differential operational amplifier circuit is connected to the sine wave conversion square wave circuit, the sine wave conversion square wave circuit is connected to the hysteresis calibration circuit,
the differential operational amplification circuit is used for carrying out isolation processing on the accessed sine voltage signal and sending the sine voltage signal after the isolation processing to the sine wave conversion square wave circuit;
the sine wave conversion square wave circuit is used for receiving the sine voltage signal after the isolation processing, converting the sine voltage signal after the isolation processing into a square wave voltage signal and sending the square wave voltage signal to the hysteresis calibration circuit.
3. The power frequency detection circuit according to claim 2, wherein the differential operational amplifier circuit comprises a first operational amplifier, a first resistor, a second resistor, a third resistor and a first negative feedback resistor, the first resistor, the second resistor and the third resistor are connected in series to a mains zero line, a non-inverting input end of the first operational amplifier is connected with a mains fire wire and a first bias power supply, a first end of the first negative feedback resistor is connected with an inverting input end of the first operational amplifier, a second end of the first negative feedback resistor is connected with an output end of the first operational amplifier, an output end of the first operational amplifier is connected with the sine wave conversion square wave circuit, and the third resistor is connected with a first end of the first negative feedback resistor.
4. The power frequency detection circuit according to claim 3, wherein the differential operational amplifier circuit further comprises a first balancing resistor, a second balancing resistor and a third balancing resistor connected in series, the other end of the first balancing resistor is connected to a live wire, and the other end of the third balancing resistor is connected to the non-inverting input end of the first operational amplifier.
5. The power frequency detection circuit according to claim 3 or 4, wherein the differential operational amplification circuit further comprises a first pull-up resistor and a first capacitor, the first pull-up resistor and the first capacitor are connected in parallel, one end of the first pull-up resistor is connected to the non-inverting input terminal of the first operational amplifier, and the other end of the first pull-up resistor is connected to the first bias power supply.
6. The power frequency detection circuit of claim 3, wherein the differential operational amplifier circuit further comprises a second capacitor, the second capacitor being in parallel with the first negative feedback resistor.
7. The power frequency detection circuit according to claim 2, wherein the sine wave conversion square wave circuit comprises a second operational amplifier, a second negative feedback resistor and a fourth resistor, a first end of the second negative feedback resistor is connected with an inverting input end of the second operational amplifier, a second end of the second negative feedback resistor is connected with an output end of the second operational amplifier, an output end of the second operational amplifier is connected with the hysteresis calibration circuit, a first end of the fourth resistor is grounded, a second end of the fourth resistor is connected with an inverting input end of the second operational amplifier, and a non-inverting input end of the second operational amplifier is connected with the differential operational amplifier circuit.
8. The power frequency detection circuit of claim 7, wherein the sine wave converted square wave circuit further comprises a second pull-up resistor and a third capacitor, wherein the second pull-up resistor and the third capacitor are connected in parallel, one end of the second pull-up resistor is connected with the non-inverting input end of the second operational amplifier, and the other end of the second pull-up resistor is grounded.
9. The power frequency detection circuit of claim 8, wherein the sine wave converted square wave circuit further comprises a fourth capacitor connected in parallel with the second negative feedback resistor.
10. An air conditioner comprising an air conditioning unit and a power frequency detection circuit as claimed in any one of claims 1 to 9.
11. A grid-tie system comprising a power grid, an air conditioning unit and a power frequency detection circuit as claimed in any one of claims 1 to 9.
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| CN107589298A (en) * | 2017-09-04 | 2018-01-16 | 珠海格力电器股份有限公司 | Mains frequency detection circuit, method, storage medium and processor |
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| CN109030937A (en) | 2018-12-18 |
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