Overcurrent detection circuit, overcurrent protection device, circuit board and air conditioner

Abstract

The present invention discloses an overcurrent detection circuit, an overcurrent protection device, a circuit board and an air conditioner, wherein the overcurrent detection circuit comprises a sampling circuit, a first voltage regulating circuit, a second voltage regulating circuit and a comparison circuit, the comparison circuit comprises a first comparator and a second comparator, the first voltage regulating output terminal is connected to the same-phase input terminal of the first comparator, the sampling output terminal is connected to the inverting input terminal of the first comparator, the second voltage regulating output terminal is connected to the reverse input terminal of the second comparator, the sampling output terminal is connected to the same-phase input terminal of the second comparator, the output terminal of the first comparator and the output terminal of the second comparator are both connected to a controller to output a comparison result; the sampling voltage is compared with a first reference voltage and a second reference voltage respectively through the comparison circuit to detect whether the sampling voltage exceeds an overcurrent threshold, and the first reference voltage and the second reference voltage can be adjusted according to a signal of the controller, so that they can be suitable for different circuit scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to an overcurrent detection circuit, an overcurrent protection device, a circuit board and an air conditioner. Background Art

[0002] Overcurrent protection circuits are widely used in various electrical equipment to protect the working circuits in electrical equipment. When the current at the detection position suddenly increases, the overcurrent protection circuit can be triggered to stop the operation of the working circuit, preventing damage to components in the circuit and playing a protective role.

[0003] At present, the overcurrent protection circuit samples the DC signal and cannot sample the circuit before rectification. For example, in an electrical device with a PFC circuit, the overcurrent protection circuit can only be set at the post-stage output of the PFC circuit. If the PFC circuit is disturbed and the output is abnormal, the overcurrent protection circuit cannot protect the components in the PFC circuit, causing the electrical device to fail to work. In addition, for the situation where the variable frequency electrical device switches the circuit during operation, the current overcurrent protection circuit cannot adjust its own overcurrent threshold and has certain limitations. Therefore, the current overcurrent protection circuit needs to be designed for different electrical devices, which is time-consuming and labor-intensive. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes an overcurrent detection circuit, an overcurrent protection device, a circuit board and an air conditioner, which can sample DC or AC voltage and output an overcurrent protection signal, and can also adjust its own overcurrent threshold according to a control signal, and are suitable for different circuit scenarios.

[0005] An overcurrent detection circuit according to a first aspect of the present invention includes:

[0006] A sampling circuit, comprising a sampling output terminal for outputting a sampling voltage;

[0007] A first voltage regulation circuit comprises a first voltage regulation receiving end and a first voltage regulation output end, wherein the first voltage regulation receiving end is used to receive a first voltage regulation signal sent by a controller, and the first voltage regulation output end is used to output a first reference voltage based on the first voltage regulation signal;

[0008] A second voltage regulation circuit comprises a second voltage regulation receiving end and a second voltage regulation output end, wherein the second voltage regulation receiving end is used to receive a second voltage regulation signal sent by the controller, and the second voltage regulation output end is used to output a second reference voltage based on the second voltage regulation signal;

[0009] The comparison circuit comprises a first comparator and a second comparator, wherein the first voltage regulation output terminal is connected to the non-inverting input terminal of the first comparator, the sampling output terminal is connected to the inverting input terminal of the first comparator, the second voltage regulation output terminal is connected to the inverting input terminal of the second comparator, the sampling output terminal is connected to the non-inverting input terminal of the second comparator, and the output terminal of the first comparator and the output terminal of the second comparator are both connected to a controller to output a comparison result.

[0010] According to the overcurrent detection circuit of the embodiment of the first aspect of the present invention, there are at least the following beneficial effects: the sampling circuit samples and outputs the sampling voltage, and compares the sampling voltage with the first reference voltage and the second reference voltage respectively through the first comparator and the second comparator to detect whether the sampling voltage exceeds the overcurrent threshold; when the sampling voltage is an AC voltage, the first comparator compares the positive voltage of the AC sampling voltage, and the second comparator compares the negative voltage of the AC sampling voltage; when the sampling voltage is a DC voltage, the first comparator directly compares with the sampling voltage; in addition, the first reference voltage and the second reference voltage can be adjusted according to the signal of the controller, and for the situation where some variable frequency electrical equipment switches the circuit during operation, the overcurrent detection circuit can adaptively change the overcurrent threshold; therefore, the overcurrent detection circuit of the embodiment of the present invention is suitable for different circuit scenarios.

[0011] According to some embodiments of the first aspect of the present invention, the first voltage regulating circuit includes a first switching device and a first oscillation circuit, the first switching device includes a first end connected to a DC source, a second end connected to a reference ground, and a third end for controlled opening and closing of the first switching device, the first oscillation circuit is connected in parallel with the first switching device, and a voltage output end of the first oscillation circuit is connected to the first voltage regulating output end.

[0012] According to some embodiments of the first aspect of the present invention, the first voltage regulating circuit further includes a first voltage follower, and the voltage output end of the first oscillation circuit is connected to the first voltage regulating output end through the first voltage follower.

[0013] According to some embodiments of the first aspect of the present invention, the second voltage regulating circuit includes a second switching device and a second oscillation circuit, the second switching device includes a second end connected to a DC source, a second end connected to a reference ground, and a third end for controlled opening and closing of the second switching device, the second oscillation circuit is connected in parallel with the second switching device, and a voltage output end of the second oscillation circuit is connected to the second voltage regulating output end.

[0014] According to some embodiments of the first aspect of the present invention, the second voltage regulating circuit further includes a second voltage follower, and the voltage output end of the second oscillation circuit is connected to the second voltage regulating output end through the second voltage follower.

[0015] According to some embodiments of the first aspect of the present invention, the first voltage regulation signal and the second voltage regulation signal are PWM signals.

[0016] According to some embodiments of the first aspect of the present invention, the first reference voltage is greater than the second reference voltage.

[0017] According to some embodiments of the first aspect of the present invention, the comparison circuit also includes a ninth resistor, a tenth resistor and a constant voltage port for adjusting the voltage of the sampling output terminal, the sampling output terminal is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the ninth resistor, and the constant voltage port is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the tenth resistor.

[0018] According to some embodiments of the first aspect of the present invention, the sampling circuit further includes at least one sampling input terminal, and the sampling input terminal is used to acquire the electrical signal.

[0019] According to some embodiments of the first aspect of the present invention, the number of the sampling input terminals is two, namely a first sampling terminal and a second sampling terminal, a sampling resistor is connected between the first sampling terminal and the second sampling terminal, the sampling resistor is connected in series with the AC line, the sampling circuit also includes a sampling op amp, the first sampling terminal is connected to the non-inverting input terminal of the sampling op amp, the second sampling terminal is connected to the inverting input terminal of the sampling op amp, and the output terminal of the sampling op amp is connected to the sampling output terminal.

[0020] An overcurrent protection device according to an embodiment of a second aspect of the present invention comprises a controller, a PFC circuit and an overcurrent detection circuit as described in any one of the embodiments of the first aspect of the present invention, wherein the controller outputs a PWM signal to the PFC circuit to control the working state of the PFC circuit, the sampling circuit is connected to the AC input of the PFC circuit to sample an electrical signal and output an AC sampling voltage, and the controller maintains or stops the operation of the PFC circuit according to a comparison result output by the comparison circuit.

[0021] The overcurrent protection device according to the embodiment of the second aspect of the present invention has at least the following beneficial effects: an overcurrent detection circuit is applied to a PFC circuit and an AC input signal of the PFC circuit is sampled, and a comparison result of the overcurrent detection circuit is sent to a controller, and the controller controls the working state of the PFC circuit according to the comparison result; when the PFC circuit is disturbed and the current at the AC input end suddenly increases, the overcurrent protection device of the embodiment of the present invention can immediately shut down the output of the PWM signal, thereby effectively protecting the components in the PFC circuit.

[0022] A circuit board according to an embodiment of the third aspect of the present invention comprises an overcurrent detection circuit as described in any one of the embodiments of the first aspect of the present invention;

[0023] or,

[0024] It comprises an overcurrent protection device as described in the embodiment of the second aspect of the present invention.

[0025] According to the circuit board of the embodiment of the third aspect of the present invention, there are at least the following beneficial effects: the overcurrent detection circuit or the overcurrent protection device including the overcurrent detection circuit is integrated into the circuit board, which can be conveniently installed on different electrical equipment; the sampling circuit in the overcurrent detection circuit samples and outputs the sampling voltage, and the sampling voltage is compared with the first reference voltage and the second reference voltage respectively by the first comparator and the second comparator to detect whether the sampling voltage exceeds the overcurrent threshold; when the sampling voltage is an AC voltage, the first comparator compares the positive voltage of the AC sampling voltage, and the second comparator compares the negative voltage of the AC sampling voltage; when the sampling voltage is a DC voltage, the first comparator directly compares with the sampling voltage; in addition, the first reference voltage and the second reference voltage can be adjusted according to the signal of the controller, and for the situation where some variable frequency electrical equipment switches the circuit during operation, the overcurrent detection circuit can adaptively change the overcurrent threshold; therefore, the overcurrent detection circuit of the embodiment of the present invention is suitable for different circuit scenarios.

[0026] An air conditioner according to an embodiment of the fourth aspect of the present invention comprises the circuit board as described in the embodiment of the third aspect of the present invention.

[0027] The air conditioner according to the embodiment of the fourth aspect of the present invention has at least the following beneficial effects: when the overcurrent detection circuit is applied to the air conditioner, the overcurrent detection circuit can adaptively adjust the overcurrent threshold according to the situation where the air conditioner switches the working circuit during operation, so as to adapt to different operating frequencies of the air conditioner.

[0028] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0030] Figure 1 A circuit diagram of a sampling circuit and a PFC circuit of an overcurrent detection circuit provided by an embodiment of the present invention;

[0031] Figure 2 A circuit diagram of a first voltage regulating circuit and a second voltage regulating circuit of an overcurrent detection circuit provided in one embodiment of the present invention;

[0032] Figure 3 A circuit diagram of a comparison circuit of an overcurrent detection circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0034] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0035] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0036] At present, the overcurrent protection circuit is based on DC sampling and compares the sampled DC voltage with the reference voltage to determine whether the circuit of the sampling object has overcurrent. However, this circuit cannot be applied to different electrical equipment. On the one hand, due to the limitation of DC sampling, a rectifier circuit needs to be set in the circuit of the sampling object, and the AC cannot be sampled directly. On the other hand, because frequency conversion equipment is becoming more and more widespread, frequency conversion equipment may switch to different circuit structures at different operating frequencies. Therefore, the overcurrent protection circuit that cannot change the overcurrent threshold cannot adapt to these frequency conversion equipment. The current overcurrent protection circuit needs to be designed separately for different electrical equipment, which requires a lot of time in design and debugging. The production cycle of electrical equipment becomes longer, the cost increases, and it is not conducive to the development of new products. Therefore, the current overcurrent protection circuit needs to be improved.

[0037] Based on this, the present invention proposes an overcurrent detection circuit, an overcurrent protection device, a circuit board and an air conditioner. On the one hand, they can be connected to a DC or AC line for sampling. On the other hand, without replacing circuit components, a control signal can be sent by a controller to change the reference voltage and adjust the overcurrent threshold of the circuit, thereby being suitable for different circuit scenarios.

[0038] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0039] Reference Figures 1 to 3 The overcurrent detection circuit provided by the first aspect of the embodiment of the present invention includes:

[0040] The sampling circuit 100 comprises a sampling output terminal for outputting a sampling voltage;

[0041] The first voltage regulation circuit 200 comprises a first voltage regulation receiving end and a first voltage regulation output end, wherein the first voltage regulation receiving end is used to receive a first voltage regulation signal sent by the controller 400, and the first voltage regulation output end is used to output a first reference voltage VrefA based on the first voltage regulation signal;

[0042] The second voltage regulation circuit 300 comprises a second voltage regulation receiving end and a second voltage regulation output end, wherein the second voltage regulation receiving end is used to receive a second voltage regulation signal sent by the controller 400, and the second voltage regulation output end is used to output a second reference voltage VrefB based on the second voltage regulation signal;

[0043] The comparison circuit includes a first comparator U3 and a second comparator U4, wherein the first voltage regulation output terminal is connected to the non-inverting input terminal of the first comparator U3, the sampling output terminal is connected to the inverting input terminal of the first comparator U3, the second voltage regulation output terminal is connected to the inverting input terminal of the second comparator U4, the sampling output terminal is connected to the non-inverting input terminal of the second comparator U4, and the output terminal of the first comparator U3 and the output terminal of the second comparator U4 are both connected to a controller 400 to output a comparison result.

[0044] The comparison circuit in this embodiment is provided with a first comparator U3 and a second comparator U4, which can be suitable for the case where the sampling output terminal outputs an AC voltage. Since the AC voltage outputs a negative voltage in the negative half cycle and cannot be directly input into the comparator, a constant voltage port V0 is provided to pull up the voltage of the sampling output terminal, so that the voltage input to the inverting input terminal of the first comparator U3 and the non-inverting input terminal of the second comparator U4 is greater than 0, so that the first comparator U3 and the second comparator U4 can compare the positive voltage. Specifically, referring to Figure 3, the comparison circuit also includes a ninth resistor R9, a tenth resistor R10 and a constant voltage port V0 for adjusting the voltage of the sampling output terminal, the sampling output terminal is connected to the inverting input terminal of the first comparator U3 and the non-inverting input terminal of the second comparator U4 through the ninth resistor R9, and the constant voltage port V0 is connected to the inverting input terminal of the first comparator U3 and the non-inverting input terminal of the second comparator U4 through the tenth resistor R10. According to circuit analysis, the resistance value of the ninth resistor R9 and the resistance value of the tenth resistor R10 affect the voltage value input to the inverting input terminal of the first comparator U3 and the non-inverting input terminal of the second comparator U4. For example, when the resistance values ​​of the ninth resistor R9 and the tenth resistor R10 are equal, the voltage value of point P is equal to half of the sum of the voltage of the constant voltage port V0 and the voltage of the sampling output terminal.

[0045] The sampling circuit 100 in this embodiment can sample a DC line or an AC line. The sampling circuit 100 also includes at least one sampling input terminal for acquiring an electrical signal. If the number of the sampling input terminals is one, then the sampling input terminal can be connected to a voltage-dividing DC circuit to acquire a DC voltage, or the sampling input terminal can be connected to an AC circuit to acquire an AC current or an AC voltage. If the number of the sampling input terminals is two, namely a first sampling terminal and a second sampling terminal, the sampling circuit 100 also includes a sampling amplifier U5. The first sampling terminal is connected to the non-inverting input terminal of the sampling amplifier U5, the second sampling terminal is connected to the inverting input terminal of the sampling amplifier U5, and the output terminal of the sampling amplifier U5 is connected to the sampling output terminal. By utilizing the voltage drop between the two ends of the sampling resistor R0, the first sampling terminal and the second sampling terminal provide different voltage inputs for the sampling amplifier U5. Obviously, when there are two sampling input terminals, the DC line or AC line can also be sampled. When sampling the DC line, only the first sampling terminal is connected to the DC line, and the second sampling terminal is left floating. At this time, the sampling amplifier U5 is equivalent to a voltage follower, outputting a DC voltage. When sampling the AC line, the first sampling terminal, the second sampling terminal and the sampling resistor R0 are all connected to the same AC line, so that two different voltages are obtained at the two input terminals of the sampling amplifier U5. Therefore, the sampling circuit 100 can sample the DC line or the AC line and is universal.

[0046] Among them, the sampling amplifier U5 can be a differential operational amplifier, which can linearly scale down the voltage, reduce common-mode signal interference, improve the accuracy of the sampling voltage, and achieve precise control.

[0047] In one embodiment, referring to Figure 1, the in-phase input terminal of the sampling amplifier U5 is connected in series with the eleventh resistor R11, and the inverting input terminal is connected in series with the twelfth resistor R12. The sampling amplifier U5 also includes a thirteenth resistor R13 and a fourteenth resistor R14, wherein one end of the thirteenth resistor R13 is connected to the connection point between the eleventh resistor R11 and the in-phase input terminal of the sampling amplifier U5, the other end of the thirteenth resistor R13 is connected to the reference ground, one end of the fourteenth resistor R14 is connected to the connection point between the twelfth resistor R12 and the inverting input terminal of the sampling amplifier U5, and the other end of the fourteenth resistor R14 is connected to the output terminal of the sampling amplifier U5. By adjusting the resistance values ​​of the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13 and the fourteenth resistor R14, the output voltage of the sampling amplifier U5 can be adjusted, thereby adjusting the voltage output amplitude of the sampling output terminal, so as to match the voltage of the constant voltage port V0.

[0048] In one embodiment, referring to Figure 2 The first voltage regulating circuit 200 includes a first switch device Q1 and a first oscillator circuit. The first switch device Q1 includes a first end connected to a DC source, a second end connected to a reference ground, and a third end for controlling the opening and closing of the first switch device Q1. The first oscillator circuit is connected in parallel with the first switch device Q1, and the voltage output end of the first oscillator circuit is connected to the first voltage regulating output end. The second voltage regulating circuit 300 includes a second switch device Q2 and a second oscillator circuit. The second switch device Q2 includes a second end connected to a DC source, a second end connected to a reference ground, and a third end for controlling the opening and closing of the second switch device Q2. The third end is connected to the second voltage regulating receiving end. The second oscillator circuit is connected in parallel with the second switch device Q2, and the voltage output end of the second oscillator circuit is connected to the second voltage regulating output end.

[0049] The first switch device Q1 and the second switch device Q2 of this embodiment have the function of controlled on and off, and can be selected as switch devices such as triodes and MOS tubes. In order to achieve voltage adjustment, the first voltage regulation signal and the second voltage regulation signal are both PWM signals, and the first reference voltage VrefA and the second reference voltage VrefB are output through the first oscillation circuit and the second oscillation circuit. Obviously, by controlling the duty cycle of the first voltage regulation signal and the second voltage regulation signal, the magnitude of the first reference voltage VrefA and the second reference voltage VrefB can be changed. For example, if the DC source is 3V, then when the duty cycle is 0, the first reference voltage VrefA and the second reference voltage VrefB are both 3V, when the duty cycle is 1, the first reference voltage VrefA and the second reference voltage VrefB are both 0, and when the duty cycle is between 0 and 1, the first reference voltage VrefA and the second reference voltage VrefB are between 3V and 0. It is worth noting that since the comparison circuit needs to compare the positive voltage and the negative voltage, the first reference voltage VrefA is greater than the second reference voltage VrefB, that is, the PWM waveform of the first voltage regulation signal is different from the PWM waveform of the second voltage regulation signal.

[0050] Among them, there are multiple implementations of the first oscillation circuit and the second oscillation circuit. For example, the first oscillation circuit includes a first resistor R1 and a first capacitor C1, the first end of the first switching device Q1, the first resistor R1, the first capacitor C1 and the reference ground are connected in sequence, and the connection point between the first resistor R1 and the first capacitor C1 is connected to the first voltage regulation output terminal, and the second oscillation circuit includes a second resistor R2 and a second capacitor C2, the second end of the second switching device Q2, the second resistor R2, the second capacitor C2 and the reference ground are connected in sequence, and the connection point between the second resistor R2 and the second capacitor C2 is connected to the second voltage regulation output terminal; for another example, the first oscillation circuit and the second oscillation circuit adopt LC circuits, and the voltage regulation function can also be realized based on PWM signals, which will not be elaborated here.

[0051] Although the first voltage regulating circuit 200 and the second voltage regulating circuit 300 of the above embodiment adopt the same circuit connection method, the two are independently set, that is, when the first voltage regulating circuit 200 adopts the above circuit structure, the second voltage regulating circuit 300 can adopt different circuit structures for voltage regulation. For example, the second voltage regulating circuit 300 can adopt an electronic digital variable resistor for voltage regulation. The electronic digital variable resistor has multiple resistors connected in series and a switch is introduced at the connection point between the two resistors. By opening and closing these switches, the total resistance value of the series branch can be adjusted to achieve voltage regulation; similarly, when the second voltage regulating circuit 300 adopts the above circuit structure, the first voltage regulating circuit 200 can adopt different circuit structures for voltage regulation; since there are many ways to achieve voltage regulation, they are not listed here one by one. It can be understood that the use of PWM signals for voltage regulation can achieve continuous adjustment of the reference voltage, which can improve the accuracy of the overcurrent detection circuit compared to the step-by-step adjustable voltage regulation method.

[0052] Based on the above embodiments, refer to Figure 2 , the first voltage regulating circuit 200 also includes a first voltage follower U1, and the connection point of the first resistor R1 and the first capacitor C1 is connected to the first voltage regulating output terminal through the first voltage follower U1. The second voltage regulating circuit 300 also includes a second voltage follower U2, and the connection point of the second resistor R2 and the second capacitor C2 is connected to the second voltage regulating output terminal through the second voltage follower U2. Since the PWM signals used for voltage regulation in the first voltage regulating circuit 200 and the second voltage regulating circuit 300 are irrelevant to the circuit of the protected object, in order to isolate signal interference, a voltage follower is used for isolation, and at the same time, the output values ​​of the first reference voltage VrefA and the second reference voltage VrefB are stabilized.

[0053] The following takes the sampling voltage as a DC voltage as an example to illustrate the working mode of the overcurrent detection circuit under DC sampling: the voltage at the sampling output end is a DC voltage, that is, Vout is always greater than 0, then the sampling output end is simultaneously added to the inverting input end of the first comparator U3 through the ninth resistor R9 and the constant voltage port V0 through the tenth resistor R10. Since the constant voltage port V0 is a constant voltage, the voltage at point P is positively correlated with the voltage at the sampling input end. The first voltage regulation signal is set to adjust the first reference voltage VrefA so that the first reference voltage VrefA is not higher than the maximum voltage allowed at point P under normal working conditions; when the circuit of the protected object is in normal working condition, the voltage at the inverting input end of the first comparator U3 is not higher than the voltage at the non-inverting input end, so the first comparator U3 outputs a high level. When the controller 400 receives the high level signal, it determines that the circuit is working normally. When the circuit of the protected object is abnormal, the voltage at the inverting input end of the first comparator U3 is higher than the voltage at the non-inverting input end, and the first comparator U3 outputs a low level. The controller 400 determines that the circuit is abnormal through the low level and takes protective action.

[0054] It can be understood that since DC sampling only needs to sample a single voltage point in the DC line, the sampling circuit 100 can be connected to the circuit with only one sampling input terminal, and the second comparator U4 in the comparator circuit does not need to perform comparison. The second comparator U4 can be bypassed or the second reference voltage VrefB can be reduced to maintain the second comparator U4 output high level.

[0055] The following takes the sampling voltage as an AC voltage as an example to illustrate the working mode of the overcurrent detection circuit under DC sampling: the sampling resistor R0 is connected in series in the AC line, and the first sampling terminal and the second sampling terminal are respectively connected to the two ends of the sampling resistor R0. At this time, the output end of the sampling amplifier U5 outputs positive voltage and negative voltage following the cycle of the AC power, that is, in the positive half cycle of the AC power, the sampling amplifier U5 outputs a positive voltage, and in the negative half cycle of the AC power, the sampling amplifier U5 outputs a negative voltage. Taking the ninth resistor R9 and the tenth resistor R10 as an example, in order to make the voltage at point P greater than 0, the voltage value of the constant voltage port V0 must be greater than the minimum value of the negative voltage at the sampling output end. For example, the constant voltage port V0 is a 3V constant voltage source, and the resistance around the sampling amplifier U5 is adjusted so that the minimum value of the negative voltage at the sampling output end is higher than -3V. At the same time, the first reference voltage VrefA is set to be greater than the second reference voltage VrefB, and the first reference voltage VrefA is slightly greater than the maximum value of the voltage at point P of the circuit of the protected object under normal working conditions. The second reference voltage VrefB is slightly smaller than the minimum value of the voltage at point P of the circuit of the protected object under normal working conditions. Then, when the circuit of the protected object is in normal working conditions, in the positive half cycle of the alternating current, the voltage at point P is lower than the first reference voltage VrefA and higher than the second reference voltage VrefB, and the first comparator U3 and the second comparator U4 both output a high level. In the negative half cycle of the alternating current, similarly, the voltage at point P is lower than the first reference voltage VrefA and higher than the second reference voltage VrefB, and the first comparator U3 and the second comparator U4 both output a high level. At this time, the controller 400 receives the high level signal and determines that the circuit is operating normally. When an abnormality occurs in the circuit of the protected object, in the positive half cycle of the alternating current, the voltage at point P is higher than the first reference voltage VrefA, and the first comparator U3 outputs a low level, or in the negative half cycle of the alternating current, the voltage at point P is lower than the second reference voltage VrefB, and the second comparator U4 outputs a low level. The controller 400 determines that the circuit is abnormal through the low level and takes protective action.

[0056] The overcurrent detection circuit of the embodiment of the present invention is applicable regardless of whether the sampled voltage is a DC voltage or an AC voltage; on the other hand, since the first reference voltage VrefA and the second reference voltage VrefB can change the voltage value by voltage regulation without replacing components, it has good adaptability to the situation where the overcurrent threshold changes due to the switching of the circuit in the frequency conversion device. For example, when the circuit in the frequency conversion device switches, the controller 400 obtains the corresponding circuit after the switching, and changes the first voltage regulation signal and the second voltage regulation signal for the preset overcurrent threshold of the switched circuit, so that the first reference voltage VrefA and the second reference voltage VrefB change to adapt to the switched circuit. Therefore, the overcurrent detection circuit of the embodiment of the present invention is applicable to different circuit scenarios.

[0057] A second aspect of an embodiment of the present invention provides an overcurrent protection device, comprising a controller 400, a PFC circuit 500, and an overcurrent detection circuit as described in any one of the first aspects above, wherein the controller 400 outputs a PWM signal to the PFC circuit 500 to control the working state of the PFC circuit 500, the sampling circuit 100 is connected to the AC input of the PFC circuit 500 to sample an electrical signal and output an AC sampling voltage, and the controller 400 maintains or stops the operation of the PFC circuit 500 according to a comparison result output by the comparison circuit.

[0058] The PFC circuit 500 in this embodiment is a Vienna rectifier circuit, and the front-stage input is an AC input, wherein the PFC circuit 500 includes a PFC signal input terminal connected to the controller 400, and the PFC signal input terminal is used to control the on and off of the third switch tube Q3 and the fourth switch tube Q4. The controller 400 can stop the operation of the PFC circuit 500 by stopping the PWM signal output, thereby preventing the PFC circuit 500 from being damaged by overcurrent; wherein, the sampling resistor R0 is arranged before the PFC circuit 500 for sampling before rectification. In this embodiment, the sampling resistor R0 is connected in series to the live wire. According to the voltage drop relationship between the two ends of the sampling resistor R0, the sampling amplifier U5 is output in the positive half cycle of the AC power. The controller 400 is set to determine that an overcurrent occurs in the circuit when a low-level signal is received. According to the content about the overcurrent judgment of the AC voltage in the first aspect of the embodiment, when the PFC circuit 500 operates normally, the controller 400 receives the high level output by the comparison circuit, and the controller 400 maintains outputting the PWM signal to the PFC circuit 500. When an abnormality occurs in the PFC circuit 500, for example, the current of the first inductor suddenly rises, the controller 400 receives the low level output by the comparison circuit, and the controller 400 performs a wave blocking action to disconnect the PWM signal to the PFC circuit 500 to prevent the PFC circuit 500 from being damaged.

[0059] The third aspect of the embodiment of the present invention provides a circuit board, including the overcurrent detection circuit of the first aspect of the embodiment, or, including the overcurrent protection device of the second aspect of the embodiment. By integrating the overcurrent detection circuit or the overcurrent protection device including the overcurrent detection circuit into the circuit board, it can be conveniently installed on different electrical equipment. The sampling circuit 100 in the overcurrent detection circuit samples and outputs the sampling voltage, and the sampling voltage is compared with the first reference voltage VrefA and the second reference voltage VrefB respectively by the first comparator U3 and the second comparator U4 to detect whether the sampling voltage exceeds the overcurrent threshold; when the sampling voltage is an AC voltage, the first comparator U3 compares the positive voltage of the AC sampling voltage, and the second comparator U4 compares the negative voltage of the AC sampling voltage. When the sampling voltage is a DC voltage, the first comparator U3 directly compares with the sampling voltage; in addition, the first reference voltage VrefA and the second reference voltage VrefB can be adjusted according to the signal of the controller 400. For the situation that some variable frequency electrical equipment switches the circuit during operation, the overcurrent detection circuit can adaptively change the overcurrent threshold; therefore, the overcurrent detection circuit of the embodiment of the present invention is suitable for different circuit scenarios.

[0060] The fourth aspect of the embodiment of the present invention provides an air conditioner, comprising the circuit board of the third aspect. The overcurrent detection circuit is applied to the air conditioner, and the overcurrent detection circuit can adaptively adjust the overcurrent threshold according to the situation that the air conditioner switches the working circuit during operation, so as to adapt to different working frequencies of the air conditioner.

[0061] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above-mentioned implementation mode. Technical personnel familiar with the field can also make various equivalent deformations or substitutions without violating the spirit of the present invention. These equivalent deformations or substitutions are all included in the scope defined by the claims of the present invention.

Claims

1. An overcurrent detection circuit, characterized in that: The overcurrent detection circuit is provided on a circuit board, and the circuit board is used to be installed on an electrical device; the overcurrent detection circuit comprises: A sampling circuit, comprising a sampling output terminal for outputting a sampling voltage; A first voltage regulation circuit comprises a first voltage regulation receiving end and a first voltage regulation output end, wherein the first voltage regulation receiving end is used to receive a first voltage regulation signal sent by a controller, and the first voltage regulation output end is used to output a first reference voltage based on the first voltage regulation signal; A second voltage regulation circuit comprises a second voltage regulation receiving end and a second voltage regulation output end, wherein the second voltage regulation receiving end is used to receive a second voltage regulation signal sent by the controller, and the second voltage regulation output end is used to output a second reference voltage based on the second voltage regulation signal; A comparison circuit, comprising a first comparator and a second comparator, wherein the first voltage regulation output terminal is connected to a non-inverting input terminal of the first comparator, the sampling output terminal is connected to an inverting input terminal of the first comparator, the second voltage regulation output terminal is connected to an inverting input terminal of the second comparator, the sampling output terminal is connected to a non-inverting input terminal of the second comparator, and the output terminal of the first comparator and the output terminal of the second comparator are both connected to a controller to output a comparison result; Among them, the first voltage regulating circuit includes a first switching device and a first oscillation circuit, the first switching device includes a first end connected to a DC source, a second end connected to a reference ground, and a third end for controlled opening and closing of the first switching device, the first oscillation circuit is connected in parallel with the first switching device, and the voltage output end of the first oscillation circuit is connected to the first voltage regulating output end.

2. The overcurrent detection circuit according to claim 1, characterized in that: The first voltage regulating circuit further includes a first voltage follower, and the voltage output end of the first oscillation circuit is connected to the first voltage regulating output end through the first voltage follower.

3. The overcurrent detection circuit according to claim 1, characterized in that: The second voltage regulating circuit includes a second switching device and a second oscillation circuit, the second switching device includes a second end connected to a DC source, a second end connected to a reference ground, and a third end for controlled opening and closing of the second switching device, the second oscillation circuit is connected in parallel with the second switching device, and a voltage output end of the second oscillation circuit is connected to the second voltage regulating output end.

4. The overcurrent detection circuit according to claim 3, characterized in that: The second voltage regulating circuit further includes a second voltage follower, and the voltage output end of the second oscillation circuit is connected to the second voltage regulating output end through the second voltage follower.

5. The overcurrent detection circuit according to claim 1, characterized in that: The first voltage regulation signal and the second voltage regulation signal are PWM signals.

6. The overcurrent detection circuit according to claim 1, characterized in that: The first reference voltage is greater than the second reference voltage.

7. The overcurrent detection circuit according to claim 1, characterized in that: The comparison circuit also includes a ninth resistor, a tenth resistor and a constant voltage port for adjusting the voltage of the sampling output terminal, the sampling output terminal is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the ninth resistor, and the constant voltage port is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the tenth resistor.

8. The overcurrent detection circuit according to claim 1, characterized in that: The sampling circuit further includes at least one sampling input terminal, and the sampling input terminal is used to acquire an electrical signal.

9. The overcurrent detection circuit according to claim 8, characterized in that: The number of the sampling input terminals is two, namely a first sampling terminal and a second sampling terminal. A sampling resistor is connected between the first sampling terminal and the second sampling terminal, and the sampling resistor is connected in series to the AC line. The sampling circuit also includes a sampling op amp. The first sampling terminal is connected to the non-inverting input terminal of the sampling op amp, the second sampling terminal is connected to the inverting input terminal of the sampling op amp, and the output terminal of the sampling op amp is connected to the sampling output terminal.

10. Overcurrent protection device, characterized in that: The invention comprises a controller, a PFC circuit and an overcurrent detection circuit as claimed in any one of claims 1 to 9, wherein the controller outputs a PWM signal to the PFC circuit to control the working state of the PFC circuit, the sampling circuit is connected to the AC input of the PFC circuit to sample an electrical signal and output an AC sampling voltage, and the controller maintains or stops the operation of the PFC circuit according to a comparison result output by the comparison circuit.

11. A circuit board, characterized in that: comprising an overcurrent detection circuit as claimed in any one of claims 1 to 9; or, Comprising the overcurrent protection device as claimed in claim 10.

12. An air conditioner, characterized in that Comprising the circuit board as claimed in claim 11.

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