An ac-dc input detection device

Abstract

This invention discloses an AC / DC input detection device, comprising an AC / DC input conditioning circuit, an AC phase-locked loop (PLL) circuit, a PLL dead-time control circuit, an AC / DC signal filtering circuit, and an AC / DC signal output circuit, sequentially connected and respectively connected to an auxiliary power supply circuit. The AC / DC input conditioning circuit modulates the voltage at the power supply output terminal, converting the AC sinusoidal signal into a square wave signal with the same phase. The AC PLL circuit performs filtering and locking. The PLL dead-time control circuit adds the square wave signal generated by the previous PLL to the dead time. The AC / DC signal output circuit compares the filtered AC / DC input signal with a threshold, ultimately outputting a 0V or 5V level as the criterion for AC / DC input. This device can judge and filter AC / DC signals, while simultaneously achieving phase-locking and dead-time control functions for AC signals. It features simple circuitry, low cost, high reliability, and a low false positive rate.

Description

Technical Field

[0001] This invention relates to a detection technology for a power source with bidirectional energy flow, and more particularly to an AC / DC input detection device. Background Technology

[0002] With the development of green and low-carbon technologies, the market demand for power supplies with bidirectional energy flow is increasing. In the process of grid-connected energy feedback, there are two types of input: DC and AC. Currently, most detection methods use microcontrollers for voltage readback and digital phase-locked loop (PLL) to determine the AC / DC input. However, the sampling process involves multiple stages such as microcontroller power supply, signal conditioning, and analog-to-digital conversion, which leads to complex current. At the same time, the signal is easy to judge when the input voltage is relatively pure, but when the DC component is large, misjudgment is likely to occur. In addition, due to the differences in the level of different PLL algorithms, abnormal problems can easily occur within a wide range of input operating ranges.

[0003] Existing technologies for AC / DC detection using digital acquisition:

[0004] After the input voltage is stepped down and impedance matched by the operational amplifier, the high-voltage AC / DC input voltage is converted into an analog-to-digital converter, which converts it into a digital signal. The microcontroller then performs data acquisition to obtain the digital voltage waveform, and performs AC / DC judgment and AC phase-locking judgment.

[0005] The disadvantages of existing technologies are: the circuits are relatively complex, involving digital-to-analog converters, microcontrollers, and other components, resulting in higher costs. Because the relevant circuits are not isolated from the AC power grid, poor-quality inputs such as high harmonics from the grid can easily affect the microcontroller. Furthermore, the requirements for data acquisition and processing algorithms are relatively high.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide an AC / DC input detection device to solve the aforementioned technical problems existing in the prior art.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] The AC / DC input detection device of the present invention includes an AC / DC input conditioning circuit, an AC phase-locked circuit, a phase-locked dead-zone control circuit, an AC / DC signal filtering circuit, and an AC / DC signal output circuit, which are sequentially connected to and respectively connected to an auxiliary power supply circuit.

[0010] The AC / DC input conditioning circuit modulates the voltage at the power supply output terminal to convert the AC sinusoidal signal into a square wave signal of the same phase, or to convert the DC signal into a level signal of the same phase, thereby converting the high voltage signal into a low voltage signal that can be processed.

[0011] The AC phase-locked loop circuit filters and locks the AC and DC phase signals modulated by the previous stage to ensure phase correctness under poor power grid quality conditions.

[0012] The phase-locked dead-time control circuit adds the square wave signal generated by the previous phase-locked circuit to the dead time to drive the low-frequency bridge arm of the bidirectional energy flow power supply, preventing it from being shot-through and causing damage. When the input is a DC voltage, the phase-locked signal level does not change.

[0013] The AC / DC signal filtering circuit will filter AC signals into potential signals that are lower than the AC / DC input judgment threshold and DC signals into potential signals that are higher than the AC / DC input judgment threshold, depending on the input signal.

[0014] The AC / DC signal output circuit compares the filtered AC / DC input signals with the threshold, and finally outputs 0V or 5V as the criterion for AC / DC input.

[0015] Compared with the prior art, the AC / DC input detection device provided by the present invention can judge and filter AC / DC signals, and at the same time realize the functions of phase-locking and dead-time control of AC signals. It has the characteristics of simple circuit, low cost, high reliability and low false judgment rate. Attached Figure Description

[0016] Figure 1 This is a block diagram of an AC / DC input detection device provided in an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of the AC / DC input conditioning circuit in an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of an AC phase-locked loop circuit in an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of the phase-locked dead-time control circuit in an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of the AC / DC signal filtering circuit in an embodiment of the present invention;

[0021] Figure 6 This is a schematic diagram of the AC / DC signal output circuit in an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them, and do not constitute a limitation on the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0023] First, the following explanations are provided for the terms that may be used in this article:

[0024] The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0025] The terms “including,” “comprising,” “containing,” “having,” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, “including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.)” should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0026] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0027] Unless otherwise explicitly specified or limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this document according to the specific circumstances.

[0028] The terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” and “counterclockwise” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience and simplification of description and do not imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this document.

[0029] The contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments used in the embodiments of this invention are not specified, they are all conventional products that can be purchased commercially.

[0030] The AC / DC input detection device of the present invention includes an AC / DC input conditioning circuit, an AC phase-locked circuit, a phase-locked dead-zone control circuit, an AC / DC signal filtering circuit, and an AC / DC signal output circuit, which are sequentially connected to and respectively connected to an auxiliary power supply circuit.

[0031] The AC / DC input conditioning circuit modulates the voltage at the power supply output terminal to convert the AC sinusoidal signal into a square wave signal of the same phase, or to convert the DC signal into a level signal of the same phase, thereby converting the high voltage signal into a low voltage signal that can be processed.

[0032] The AC phase-locked loop circuit filters and locks the AC and DC phase signals modulated by the previous stage to ensure phase correctness under poor power grid quality conditions.

[0033] The phase-locked dead-time control circuit adds the square wave signal generated by the previous phase-locked circuit to the dead time to drive the low-frequency bridge arm of the bidirectional energy flow power supply, preventing it from being shot-through and causing damage. When the input is a DC voltage, the phase-locked signal level does not change.

[0034] The AC / DC signal filtering circuit will filter AC signals into potential signals that are lower than the AC / DC input judgment threshold and DC signals into potential signals that are higher than the AC / DC input judgment threshold, depending on the input signal.

[0035] The AC / DC signal output circuit compares the filtered AC / DC input signals with the threshold, and finally outputs 0V or 5V as the criterion for AC / DC input.

[0036] The AC / DC input conditioning circuit includes:

[0037] The input voltage is current-limited by multiple resistors R2, R3, and R4 connected in series, which reduces the power consumption of the resistors when the high voltage is input.

[0038] When the input voltage is positive, it is regulated by the first Zener diode ZD1 after passing through the first diode D1, thus achieving the purpose of voltage reduction. At the same time, it is connected to the positive power supply VCC through the first resistor R1 to clamp the highest positive voltage.

[0039] When the input voltage is negative, it is regulated by the second Zener diode ZD2 after passing through the second diode D2 to achieve the purpose of voltage reduction. At the same time, it is connected to the negative power supply VEE through the fifth resistor R5 to clamp the lowest negative voltage.

[0040] When the input is AC, the output voltage Vout waveform is a square wave signal with the same phase as the AC input. The maximum value of the positive phase is the voltage value regulated by the first Zener diode ZD1, and the minimum value of the negative phase is the voltage value regulated by the second Zener diode ZD2.

[0041] When the input is a positive DC signal, the output voltage Vout is a positive level with an amplitude equal to the voltage regulated by the first Zener diode ZD1.

[0042] When the input is a negative phase DC signal, the output voltage Vout is the negative phase level of the voltage regulated by the second Zener diode ZD2.

[0043] The AC phase-locked circuit includes:

[0044] The output voltage Vin of the AC input conditioning circuit is compared with the positive phase signal after voltage division by the positive power supply VCC and the reference point by a comparator, and a first output voltage Vout1 with the same phase as the AC input signal is generated.

[0045] The output voltage Vin of the AC input conditioning circuit is compared with the negative phase signal after the negative power supply VEE and the reference point voltage division by a comparator to generate a second output voltage Vout2 that is opposite to the phase of the AC input signal.

[0046] Specifically, the voltage signal amplitude of the positive power supply VCC divided by resistors R68 and R69 should be lower than the voltage regulation value of the first Zener diode ZD1 in the AC input conditioning circuit; the voltage signal amplitude of the negative power supply VEE divided by resistors R37 and R38 should be higher than the voltage regulation value of the second Zener diode ZD2 in the AC input conditioning circuit, in order to filter out AC zero-crossing oscillation problems.

[0047] The phase-locked dead-time control circuit includes:

[0048] The first input voltage Vin1, after passing through the forty-fifth resistor R45, charges the twenty-eighth capacitor C28. When the voltage reaches the threshold for the eighth NAND gate U8 to switch from low to high level, Vout1 outputs a high level. When the input voltage reaches the threshold for the U8 to switch from high to low level, Vout1 outputs a low level.

[0049] The second input voltage Vin2, after phase-locked loop, charges the twenty-ninth capacitor C29 after passing through the forty-sixth resistor R46. When the voltage reaches the threshold for the eighth NAND gate U8 to switch from low to high level, Vout2 outputs a high level. When the input voltage reaches the threshold for the eighth NAND gate U8 to switch from high to low level, Vout2 outputs a low level.

[0050] The time it takes to reach the conversion threshold during the high-low level transition is called the dead time. Control without dead time can be achieved by adjusting the specifications of the forty-fifth resistor R45 and the twenty-eighth capacitor C28, and the forty-sixth resistor R46 and the twenty-ninth capacitor C29.

[0051] At the same time, the output of the eighth NAND gate U8 is introduced into the input terminal to enable the first output voltage Vout1 and the second output voltage Vout2 to achieve level mutual exclusion in the event of a single-sided circuit fault, thereby preventing the low-frequency bridge arm of the grid from experiencing a shoot-through short circuit and causing the machine to explode.

[0052] The AC / DC signal filtering circuit includes:

[0053] When the input is AC, the AC / DC filtering circuit inputs the first input voltage Vin1 and the second input voltage Vin2 as TTL level signals with the same and opposite phases as the AC input. When the level of the first input voltage Vin1 or the second input voltage Vin2 changes from low to high, positive voltages are generated through the 114th capacitor C114 and the 119th capacitor C119, respectively. This causes the output voltage Vout to be connected to the reference point through the 222nd resistor R222, discharging the 113th capacitor C113. The maximum value of the output voltage Vout within the AC input frequency range is adjusted by adjusting the capacitance of the 113th capacitor C113 and the resistance of the 222nd resistor R222.

[0054] When the input is DC, the levels of the first input voltage Vin1 and the second input voltage Vin2 of the AC / DC screening circuit do not change. Therefore, the seventh transistor Q7 and the ninth transistor Q9 will not conduct, and the output voltage Vout remains constant at 4V.

[0055] This enables the filtering of AC and DC signals.

[0056] The AC / DC signal output circuit includes:

[0057] When the output is AC, by selecting the resistance values ​​of the 218th resistor R218 and the 219th resistor R219, the input voltage at the inverting input terminal of the 25th op-amp U25 is made greater than the input voltage Vin signal output by the AC / DC signal filtering circuit, so that the output terminal of the 25th op-amp U25 outputs a low level.

[0058] When the output is DC, the input voltage Vin is 4V, which is greater than the input voltage of the inverting input terminal of the 25th op-amp U25, causing the output terminal of the 25th op-amp U25 to output a high level, thereby realizing the input AC / DC judgment;

[0059] The eleventh NAND gate U11 converts the high and low level signals of the operational amplifier's power supply voltage into TTL levels for convenient use in subsequent circuits.

[0060] The function of diode D29 (the twenty-ninth diode) is to prevent AC / DC input switching failures during power supply operation and improve circuit reliability.

[0061] In summary, the AC / DC input detection device of this invention can accurately determine the AC voltage and output a TTL level for subsequent control and judgment; it uses analog circuits to judge relevant signals, improving reliability; and it reduces circuit cost and the development difficulty of using digital filtering phase-locked loop algorithms.

[0062] To more clearly demonstrate the technical solution and its effects provided by the present invention, the embodiments of the present invention will be described in detail below with reference to specific examples.

[0063] Example 1

[0064] like Figure 1 As shown:

[0065] The AC / DC input detection device includes an AC / DC input conditioning circuit, an AC phase-locked loop circuit, a phase-locked dead-time control circuit, an AC / DC signal filtering circuit, an AC / DC signal logic output circuit, and an auxiliary power supply circuit.

[0066] The AC / DC input conditioning circuit modulates the voltage at the power supply output terminal to convert an AC sinusoidal signal into a square wave signal of the same phase, or to convert a DC signal into a level signal of the same phase. The main function of this part is to convert high-voltage signals into low-voltage signals that can be processed.

[0067] The AC phase-locked circuit filters and locks the AC and DC phase signals modulated by the previous stage to ensure phase accuracy under poor power grid quality conditions.

[0068] The phase-locked dead-time control circuit adds the square wave signal generated by the previous phase-locked circuit to the dead time to drive the low-frequency bridge arm of the bidirectional energy flow power supply, preventing it from being shot-through and causing damage. When the input is a DC voltage, the phase-locked signal level does not change.

[0069] The AC / DC signal filtering circuit will filter AC signals into potential signals that are below the AC / DC input judgment threshold and DC signals into potential signals that are above the AC / DC input judgment threshold, based on the different input signals.

[0070] The AC / DC signal output circuit compares the filtered AC / DC input signals with the threshold and finally outputs a TTL level as the criterion for AC / DC input.

[0071] The specific implementation of the AC / DC input conditioning circuit is as follows: Figure 2 As shown, the input voltage is current-limited by resistors R2, R3, and R4. Multiple resistors are connected in series to reduce power consumption during high-voltage input. When the input voltage is positive, it is regulated by diode D1 and then by ZD1, achieving voltage reduction. Simultaneously, R1 is connected to the positive power supply VCC to clamp the highest positive voltage. When the input voltage is negative, it is regulated by diode D2 and then by ZD2, achieving voltage reduction. Simultaneously, R5 is connected to the negative power supply VEE to clamp the lowest negative voltage. When the input is AC, the Vout waveform is a square wave signal with a positive phase maximum value equal to the ZD1 regulated voltage and a negative phase minimum value equal to the ZD2 regulated voltage, with the same phase as the AC input. When the input is a positive DC signal, the Vout output amplitude is the positive phase level of the ZD1 regulated voltage; when the input is a negative DC signal, the Vout output amplitude is the negative phase level of the ZD2 regulated voltage. This achieves signal conditioning.

[0072] The specific implementation of the AC phase-locked loop circuit is as follows: Figure 3 As shown, the output voltage Vin of the AC input conditioning circuit is compared with the positive phase signal (after voltage division by VCC and the reference point) and the negative phase signal (after voltage division by VEE and the reference point) by a comparator, generating Vout1, which is in phase with the AC input signal, and Vout2, which is in phase with the AC input signal. The amplitude of the VCC voltage divided by R68 and R69 should be lower than the regulated voltage ZD1 in the AC input conditioning circuit, and the amplitude of the VEE voltage divided by R37 and R38 should be higher than the regulated voltage ZD2 in the AC input conditioning circuit, used to filter out AC zero-crossing oscillation problems.

[0073] The specific implementation of the phase-locked dead-time control circuit is as follows: Figure 4As shown, the signal after phase-locked loop (PLL) charges C28 after passing through R45. When the voltage reaches the threshold for the U8 low-to-high level transition, Vout1 outputs a high level; when the input voltage reaches the threshold for the U8 high-to-low level transition, Vout1 outputs a low level. The time it takes to reach the transition threshold during the high-to-low level transition is called the dead time. By adjusting the specifications of R45 and C28, and R46 and C29, control without dead time can be achieved. Connecting pin 6 of U8 to pin 2 and pin 3 of U8 to pin 4 ensures that in the event of a single-sided circuit fault, Vout1 and Vout2 are mutually exclusive, preventing shoot-through short circuits and generator failures in the grid-connected low-frequency bridge arm.

[0074] The AC / DC signal filtering circuit is specifically implemented as follows: Figure 5 As shown, when the input is AC, the AC / DC filtering circuit inputs Vin1 and Vin2 are TTL level signals with the same and opposite phases as the AC input, respectively. When Vin1 or Vin2 transitions from low to high, it generates a positive voltage through capacitors C114 and C119, respectively, thus connecting the Vout voltage to the reference point through R222 and discharging C113. By adjusting the capacitance of C113 and the resistance of R222, the maximum value of Vout within the AC input frequency range can be adjusted. When the input is DC, the input levels Vin1 and Vin2 of the AC / DC filtering circuit do not change, so Q7 and Q9 will not conduct, and the Vout voltage output is constant at 4V. This achieves AC / DC signal filtering.

[0075] The specific implementation of the AC / DC signal output circuit is as follows: Figure 6 As shown, when the output is AC, the values ​​of resistors R218 and R219 are selected to ensure that the input voltage at pin 6 of op-amp U25 is greater than the Vin signal output by the AC / DC signal filtering circuit, causing the output at pin 7 of op-amp U25 to be low. When the output is DC, Vin is 4V, which is greater than the input voltage at pin 6 of U25, causing the output at pin 7 of op-amp U25 to be high, thus achieving AC / DC input judgment. U11 converts the high / low level signal of the op-amp supply voltage into TTL level for convenient use in subsequent circuits. D29 prevents AC / DC input switching failures during power supply operation, improving circuit reliability.

[0076] like Figure 6 The diagram shown is a schematic of an AC / DC signal output circuit.

[0077] The AC / DC input detection device of this invention detects AC / DC input signals using simple analog circuits, improving detection accuracy and speed. By changing the circuit parameters of each part, it can detect a wide range of inputs and low-quality power inputs, improving adaptability. While performing AC / DC input judgment, it can also output a drive signal for driving a bidirectional energy flow power supply, reducing cost and improving versatility.

[0078] In practice, each part can be replaced with the same or similar scheme. For example, an integrated comparator can be used to condition the input voltage in the AC / DC input conditioning circuit.

[0079] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. An AC / DC input detection device, characterized in that, It includes an AC / DC input conditioning circuit, an AC phase-locked loop circuit, a phase-locked dead-zone control circuit, an AC / DC signal filtering circuit, and an AC / DC signal output circuit, which are connected in sequence and respectively to the auxiliary power supply circuit. The AC / DC input conditioning circuit modulates the voltage at the power supply output terminal to convert the AC sinusoidal signal into a square wave signal of the same phase, or to convert the DC signal into a level signal of the same phase, thereby converting the high voltage signal into a low voltage signal that can be processed. The AC phase-locked loop circuit filters and locks the AC and DC phase signals modulated by the previous stage to ensure phase correctness under poor power grid quality conditions. The phase-locked dead-time control circuit adds the square wave signal generated by the previous phase-locked circuit to the dead time to drive the low-frequency bridge arm of the bidirectional energy flow power supply, preventing it from being shot-through and causing damage. When the input is a DC voltage, the phase-locked signal level does not change. The AC / DC signal filtering circuit will filter AC signals into potential signals that are lower than the AC / DC input judgment threshold and DC signals into potential signals that are higher than the AC / DC input judgment threshold, depending on the input signal. The AC / DC signal output circuit compares the filtered AC / DC input signals with the threshold, and finally outputs 0V or 5V as the criterion for AC / DC input.

2. The AC / DC input detection device according to claim 1, characterized in that, The AC / DC input conditioning circuit includes: The input voltage is current-limited by multiple resistors connected in series, reducing resistor power consumption when high voltage is input. When the input voltage is positive, it is regulated by the first Zener diode (ZD1) after passing through the first diode (D1) to achieve the purpose of voltage reduction. At the same time, it is connected to the positive power supply (VCC) through the first resistor (R1) to clamp the highest positive voltage. When the input voltage is negative, it is regulated by the second Zener diode (ZD2) after passing through the second diode (D2) to achieve the purpose of voltage reduction. At the same time, it is connected to the negative power supply (VEE) through the fifth resistor (R5) to clamp the lowest negative voltage. When the input is AC, the output voltage (Vout) waveform is a square wave signal with the same phase as the AC input. The maximum value of the positive phase is the voltage regulated by the first Zener diode (ZD1), and the minimum value of the negative phase is the voltage regulated by the second Zener diode (ZD2). When the input is a positive DC signal, the output voltage (Vout) has an amplitude equal to the positive phase level of the voltage regulated by the first Zener diode (ZD1). When the input is a negative DC signal, the output voltage (Vout) has an amplitude that is the negative phase level of the voltage regulated by the second Zener diode (ZD2).

3. The AC / DC input detection device according to claim 2, characterized in that, The AC phase-locked circuit includes: The output voltage (Vin) of the AC / DC input conditioning circuit is compared with the positive phase signal after voltage division by the positive power supply (VCC) and the reference point by a comparator, and a first output voltage (Vout1) with the same phase as the AC input signal is generated. The output voltage (Vin) of the AC / DC input conditioning circuit is compared with the negative phase signal after the negative power supply (VEE) and the reference point are divided by a comparator to generate a second output voltage (Vout2) that is opposite in phase to the AC input signal. Specifically, the voltage amplitude of the positive power supply (VCC) through the voltage divider between resistors 68 (R68) and 69 (R69) should be lower than the voltage regulation value of the first Zener diode (ZD1) in the AC / DC input conditioning circuit; the voltage amplitude of the negative power supply (VEE) through the voltage divider between resistors 37 (R37) and 38 (R38) should be higher than the voltage regulation value of the second Zener diode (ZD2) in the AC / DC input conditioning circuit, in order to filter out AC zero-crossing oscillation problems.

4. The AC / DC input detection device according to claim 3, characterized in that, The phase-locked dead-time control circuit includes: The first input voltage (Vin1) after phase-locked loop passes through the forty-fifth resistor (R45) and charges the twenty-eighth capacitor (C28). When the first input voltage (Vin1) reaches the threshold for the low-to-high level transition of the eighth NAND gate (U8), the first output voltage (Vout1) outputs a high level. When the first input voltage (Vin1) reaches the threshold for the high-to-low level transition of U8, the first output voltage (Vout1) outputs a low level. The second input voltage (Vin2) after phase-locked loop charges the twenty-ninth capacitor (C29) after passing through the forty-sixth resistor (R46). When the second input voltage (Vin2) reaches the threshold of the eighth NAND gate (U8) from low to high level, the second output voltage (Vout2) outputs a high level. When the second input voltage (Vin2) reaches the threshold of the eighth NAND gate (U8) from high to low level, the second output voltage (Vout2) outputs a low level. The time it takes to reach the switching threshold during the high-low level transition is called the dead time. Different dead times can be controlled by adjusting the specifications of the 45th resistor (R45) and the 28th capacitor (C28), and the 46th resistor (R46) and the 29th capacitor (C29). Meanwhile, the outputs of the two eighth NAND gates (U8) are respectively introduced into the input of the other eighth NAND gate (U8) to achieve level mutual exclusion between the first output voltage (Vout1) and the second output voltage (Vout2) in the event of a single-sided circuit fault, thereby preventing the grid-connected low-frequency bridge arm from experiencing a short circuit and causing a blowout.

5. The AC / DC input detection device according to claim 4, characterized in that, The AC / DC signal filtering circuit includes: When the input is AC, the AC / DC filtering circuit inputs a first input voltage (Vin1) and a second input voltage (Vin2) that are TTL level signals with the same and opposite phases as the AC input, respectively. When the output level of the first input voltage (Vin1) or the second input voltage (Vin2) changes from low to high, positive voltages are generated through the 114th capacitor (C114) and the 119th capacitor (C119), respectively. These voltages then pass through the 7th transistor (Q7) and the 9th transistor (Q9) to collect the output voltage (Vout). The output voltage (Vout) is connected to the reference point through the 222nd resistor (R222) to discharge the 113th capacitor (C113). The maximum value of the output voltage (Vout) within the AC input frequency range is adjusted by adjusting the capacitance of the 113th capacitor (C113) and the resistance of the 222nd resistor (R222). When the input is DC, the levels of the first input voltage (Vin1) and the second input voltage (Vin2) of the AC / DC filtering circuit do not change. Therefore, the seventh transistor (Q7) and the ninth transistor (Q9) will not conduct, and the output voltage (Vout) is constant at 4V. This enables the filtering of AC and DC signals.

6. The AC / DC input detection device according to claim 5, characterized in that, The AC / DC signal output circuit includes: When the output is AC, by selecting the resistance values ​​of the 218th resistor (R218) and the 219th resistor (R219), the input voltage at the inverting input terminal of the 25th op-amp (U25) is made greater than the input voltage (Vin) signal output by the AC / DC signal filtering circuit, so that the output terminal of the 25th op-amp (U25) outputs a low level. When the output is DC, the input voltage (Vin) is 4V, which is greater than the input voltage of the inverting input terminal of the 25th op-amp (U25), causing the output terminal of the 25th op-amp (U25) to output a high level, thereby realizing the input AC / DC judgment; The output of the 25th operational amplifier (U25) is connected to the 11th NAND gate (U11), which converts the high and low level signals of the operational amplifier's power supply voltage into TTL levels. The twenty-ninth diode (D29) is connected between the non-inverting input and output terminals of the twenty-fifth operational amplifier (U25). The function of the twenty-ninth diode (D29) is to prevent AC / DC input switching faults during operation.

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