An overcurrent protection circuit and air conditioning system

Abstract

The application discloses an overcurrent protection circuit and an air conditioning system. The overcurrent protection circuit comprises a plurality of sampling circuits connected with devices to be protected, a protection circuit for executing overcurrent protection, and a superposition circuit connected with the plurality of sampling circuits. Each sampling circuit is provided with a reference voltage, which matches the power level of the device to be protected. The reference voltages of different sampling circuits are different. When the sampling signal obtained by the sampling circuit from the device to be protected is greater than the reference voltage, a pre-protection voltage is output. The superposition circuit superimposes all the pre-protection voltages and outputs a first protection voltage. The protection circuit can take the first protection voltage as an overcurrent reference voltage to protect the device to be protected. Compared with the prior art, the application can cope with different power levels and operating conditions of the device to be protected, automatically adjust the overcurrent reference voltage, match multiple models through one circuit, realize the general design of one circuit with multiple functions, and belongs to integrated circuit manufacturing.

Description

Technical Field

[0001] This invention relates to the field of overcurrent protection, and in particular to an overcurrent protection circuit and an air conditioning system. Background Technology

[0002] There are many mature technical solutions for overcurrent protection circuits. Their core principle is mostly based on comparing a reference protection voltage with a real-time current sample. When the real-time current exceeds the reference protection voltage, the comparator will quickly pull down the output signal to achieve protection. However, the reference protection voltage used for protection is not flexible. For different models, different reference protection voltage configuration circuits need to be adjusted to adapt to different power levels.

[0003] A prior art hardware overcurrent protection circuit is proposed, which includes an isolation protection circuit that can cut off the connection between the AC power phase line and the neutral line when the sampled voltage exceeds a preset voltage. Its overcurrent protection directly cuts off the main circuit, which can lead to bus backflow and transistor failure if the IGBT power module is not completely shut down.

[0004] In another existing technology, a first current signal is obtained by sampling, and a second current signal is obtained by inverting the first current signal. The two sets of signals are used for protection. This scheme only collects a single current signal and inverts it, and uses a uniform reference voltage for protection, which cannot meet the protection requirements of various operating conditions.

[0005] Another existing technology employs a circuit that automatically tracks the voltage at the current-limiting protection point. Within a wide operating voltage range, the protection point is at its maximum value at low voltage and at its minimum value when the voltage reaches its highest point. While this solution does achieve automatic adjustment, it cannot resolve the issue of a large voltage spike at the moment the rectifier is turned on, leading to overcurrent protection misjudgments during startup.

[0006] Therefore, how to design an overcurrent protection circuit and air conditioning system that can cope with the operating conditions of equipment of different power levels and the equipment to be protected, and automatically adjust the overcurrent protection value, is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0007] In view of the fact that the existing technology uses a fixed reference protection voltage to achieve overcurrent protection, which cannot be adapted to different models of the equipment to be protected, this invention proposes an overcurrent protection circuit and air conditioning system. It aims to output a first protection voltage adapted to different power levels by cooperating with multiple sampling circuits and superposition circuits, and output a second protection voltage in conjunction with a constant voltage circuit. The overcurrent reference voltage is switched by a switching circuit, thereby adapting to the operating conditions of the equipment to be protected for overcurrent protection. This invention belongs to integrated circuit manufacturing.

[0008] The technical solution of the present invention is to propose an overcurrent protection circuit, which includes multiple sampling circuits connected to the device to be protected, a protection circuit for performing overcurrent protection, and a superposition circuit connected to the multiple sampling circuits.

[0009] Each of the sampling circuits is provided with a reference voltage, which is set to match the power level of the device to be protected. The reference voltages set for different sampling circuits are different. When the sampling signal obtained by the sampling circuit from the device to be protected is greater than the reference voltage, a pre-protection voltage is output.

[0010] The superposition circuit is used to superimpose all the pre-protection voltages and output a first protection voltage. The protection circuit can use the first protection voltage as an overcurrent reference voltage to provide overcurrent protection for the device to be protected.

[0011] Based on the above scheme, this invention can provide different first protection voltages at different power levels by superimposing circuits and cooperating with multiple sampling circuits. It can not only dynamically adjust the overcurrent reference voltage used for overcurrent protection during the power rise stage of the device to be protected, but also adapt to devices to be protected at different power levels, realizing a universal design with one circuit for multiple uses.

[0012] Furthermore, the overcurrent protection circuit described in this invention also includes a constant voltage circuit, which at least has a heating resistor that generates heat using the main circuit current of the device to be protected, and a thermistor disposed near the heating resistor.

[0013] The constant voltage circuit is used to output a second protection voltage, and the magnitude of the second protection voltage is controlled by the resistance value of the thermistor. The protection circuit can use the second protection voltage as an overcurrent reference voltage to provide overcurrent protection for the device to be protected.

[0014] Based on the above scheme, the present invention can construct a constant voltage circuit that outputs different second protection voltages according to the resistance value of the thermistor. Moreover, when the protected device is in the power stable stage and the resistance value of the thermistor does not change, the second protection voltage can be maintained within the variation range of 1%, thereby achieving long-term stable overcurrent protection.

[0015] Furthermore, the overcurrent protection circuit of the present invention also includes a switching circuit, which is connected to the superposition circuit and the constant voltage circuit, and is used to switch the output of the first protection voltage or the second protection voltage to the protection circuit. The protection circuit uses the output of the switching circuit as the overcurrent reference voltage.

[0016] Based on the above scheme, the present invention can switch the first protection voltage and the second protection voltage as the overcurrent reference voltage for overcurrent protection. During the power rise phase, the dynamically adjustable first protection voltage can be used as the overcurrent reference voltage, and during the power stabilization phase, the long-term stable second protection voltage can be used as the overcurrent reference voltage, thus achieving reliable protection of the equipment under all operating conditions.

[0017] Furthermore, each of the sampling circuits in this invention includes a first comparator, and a first resistor and a second resistor connected to the first comparator;

[0018] The non-inverting input of the first comparator is connected to the device to be protected to obtain a sampling signal. The inverting input of the first comparator is connected to the reference voltage. The output of the first comparator is connected to the second resistor and outputs the pre-protection voltage. One end of the first resistor is connected between the output of the first comparator and the second resistor, and the other end of the first resistor is connected to a fixed voltage.

[0019] Based on the above-mentioned scheme, this invention can output multiple pre-protection voltages according to different power levels. By superimposing multiple pre-protection voltages with a superposition circuit, different first protection voltages can be generated at different power levels. This not only allows for dynamic adjustment of the overcurrent reference voltage used for overcurrent protection during the power rise phase of the protected device, but also adapts to protected devices of different power levels.

[0020] Furthermore, the superposition circuit described in this invention includes: resistors R7, R8, R9, R10, and R11; capacitors C1, C2, and C3; and amplifier U1.

[0021] The non-inverting input terminal of the amplifier U1 is connected to a fixed voltage, the inverting input terminal of the amplifier U1 is connected to the resistor R10 and then grounded, and the output terminal of the amplifier U1 outputs the first protection voltage.

[0022] One end of capacitor C1 is connected to the non-inverting input terminal of amplifier U1, and the other end of capacitor C1 is connected to the pre-protection voltage output by the first sampling circuit. Resistor R7 is connected in parallel across capacitor C1.

[0023] One end of capacitor C2 is connected to the non-inverting input terminal of amplifier U1, and the other end of capacitor C2 is connected to the pre-protection voltage output by the second sampling circuit. Resistor R8 is connected in parallel across capacitor C1.

[0024] One end of capacitor C3 is connected to the non-inverting input terminal of amplifier U1, and the other end of capacitor C3 is connected to the pre-protection voltage output by the third sampling circuit. Resistor R9 is connected in parallel across capacitor C1.

[0025] The resistor R11 is connected between the inverting input terminal and the output terminal of the amplifier U1, and the capacitor C4 is connected in parallel across the resistor R11.

[0026] Based on the above scheme, the present invention can superimpose multiple pre-protection voltages through a superposition circuit, thereby superimposing the original multiple output pre-protection voltages into a first protection voltage related to the power level. This first protection voltage is used as an overcurrent reference voltage, which can be dynamically adjusted during the power rise stage of the protected device, thereby improving the reliability of the overcurrent protection circuit. It can also be adapted to protected devices of different power levels, realizing a universal design with one circuit for multiple uses.

[0027] The constant voltage circuit described in this invention includes: a current transformer UND1, a heating resistor RW, a thermistor RT, a resistor R14, a resistor R15, a resistor R16, a capacitor C5, and an amplifier U2;

[0028] The current transformer UND1 is used to generate a current proportional to the main circuit current of the device to be protected. The heating resistor RW is connected to the current transformer UND1, and the thermistor RT is placed near the heating resistor RW.

[0029] The non-inverting input terminal of the amplifier U2 is connected to the thermistor RT1 and then a fixed voltage is applied. The output terminal of the amplifier U2 is connected to the resistors R15 and R16 and then grounded. The output terminal of the constant voltage circuit is set between the resistors R15 and R16 to output the second protection voltage. The inverting input terminal of the amplifier U2 is connected between the output terminal of the amplifier U2 and the resistor R15.

[0030] One end of the capacitor C5 is connected between the thermistor RT and the non-inverting input terminal of the amplifier U2, and the other end of the capacitor C5 is grounded. The resistor R14 is connected in parallel across the capacitor C5.

[0031] Based on the above scheme, the present invention can construct a constant voltage circuit that outputs different second protection voltages according to the resistance value of the thermistor. Moreover, when the protected device is in the power stable stage and the resistance value of the thermistor does not change, the second protection voltage can be maintained within the variation range of 1%, thereby achieving long-term stable overcurrent protection.

[0032] Furthermore, the switching circuit in this invention includes a switching switch, the first terminal of the switching switch is connected to the first protection voltage, the second terminal of the switching switch is connected to the second protection voltage, and the third terminal of the switching switch outputs the overcurrent reference voltage;

[0033] The switch can switch the third terminal to be connected to the first terminal or the second terminal.

[0034] Based on the above scheme, the present invention can switch the first protection voltage and the second protection voltage as the overcurrent reference voltage for overcurrent protection. During the power rise phase, the dynamically adjustable first protection voltage can be used as the overcurrent reference voltage, and during the power stabilization phase, the long-term stable second protection voltage can be used as the overcurrent reference voltage, thus achieving reliable protection of the equipment under all operating conditions.

[0035] Furthermore, in this invention, when the device to be protected is in the power boost stage, the third terminal of the switching switch is connected to the first terminal;

[0036] When the device to be protected is in a power stable phase, the third terminal of the switching switch is connected to the second terminal.

[0037] Based on the above-mentioned scheme, this invention can connect the first terminal and the third terminal during the power boosting stage, so that the first protection voltage can be used as the overcurrent reference voltage for overcurrent protection. This allows the overcurrent reference voltage to change with the power boosting, improving the reliability of the overcurrent protection circuit. Furthermore, during the power stabilization stage, the second terminal and the third terminal can be connected, so that the second protection voltage can be used as the overcurrent reference current for overcurrent protection, achieving long-term stable overcurrent protection.

[0038] Furthermore, the protection circuit described in this invention includes a second comparator, resistor R12, and resistor R13;

[0039] The inverting input of the second comparator is connected to the device to be protected to obtain a sampling signal, the non-inverting input of the second comparator is connected to the switching circuit to obtain the overcurrent reference voltage, the output of the second comparator is connected to the resistor R13 and outputs an overcurrent signal for overcurrent protection, one end of the resistor R12 is connected between the output of the second comparator and the resistor R13, and the other end of the resistor R12 is connected to a fixed voltage.

[0040] Based on the above scheme, this invention can determine whether there is an overcurrent abnormality in the device to be protected by comparing the sampled voltage with the overcurrent reference voltage, and can pull the overcurrent signal low to a low level when an overcurrent abnormality occurs, thereby performing overcurrent protection and avoiding device damage caused by the overcurrent abnormality.

[0041] The present invention also proposes an air conditioning system having a drive circuit connected to the aforementioned overcurrent protection circuit.

[0042] This invention pertains to integrated circuit manufacturing and, compared with existing technologies, has at least the following advantages:

[0043] 1. Through the design of multiple sampling circuits and superposition circuits, this invention can provide a first protection voltage that varies with power, can cope with the protected equipment of different power levels, automatically adjust the overcurrent protection value, and can cope with various operating conditions of different power levels of the protected equipment such as low load, rated load, and overload, thus improving the reliability of the overcurrent protection circuit.

[0044] 2. Through the design of a constant voltage circuit, this invention can output different second protection voltages according to the resistance value of the thermistor. Moreover, when the protected device is in a stable power stage and the resistance value of the thermistor does not change, the second protection voltage can be maintained within a 1% variation range to achieve long-term stable overcurrent protection.

[0045] 3. This invention can be adapted to a variety of models without the need to set different reference protection voltage configuration circuits for different models, thus realizing a universal design with one circuit for multiple uses. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the overcurrent protection circuit of the present invention in the first embodiment;

[0048] Figure 2 This is a schematic diagram of the overcurrent protection circuit of the present invention in a second embodiment;

[0049] Figure 3 This is a schematic diagram of the circuit topology of the first sampling circuit in this invention;

[0050] Figure 4 This is a schematic diagram of the circuit topology of the second sampling circuit in this invention;

[0051] Figure 5 This is a schematic diagram of the circuit topology of the third sampling circuit in this invention;

[0052] Figure 6 This is a schematic diagram of the circuit topology of the superimposed circuit in this invention;

[0053] Figure 7 This is a schematic diagram of the circuit topology of the constant voltage circuit in this invention;

[0054] Figure 8 This is a schematic diagram of the circuit topology when the first and third terminals of the switching circuit in this invention are connected;

[0055] Figure 9 This is a schematic diagram of the circuit topology when the second and third terminals of the switching circuit in this invention are connected;

[0056] Figure 10 This is a schematic diagram of the circuit topology of the protection circuit in this invention;

[0057] Figure 11 This is a schematic diagram illustrating the working process of the overcurrent protection circuit in this invention;

[0058] Figure 12 This is a control flowchart of the overcurrent protection circuit in a specific embodiment of the present invention. Detailed Implementation

[0059] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0060] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0061] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0062] The core principle of existing overcurrent protection circuits is to acquire real-time current samples and compare the real-time current with a reference protection voltage. If the real-time current is greater than the reference protection voltage, the comparator quickly pulls down the output signal to achieve overcurrent protection. However, this protection process uses a fixed reference protection voltage, which cannot cope with the devices to be protected at different power levels. Different reference protection voltage configuration circuits need to be adjusted for different power levels.

[0063] To address the aforementioned issues, this invention outputs multiple pre-protection voltages through multiple sampling circuits. These pre-protection voltages are then superimposed using a superposition circuit. This allows for the generation of different first protection voltages at different power levels, enabling the protection of devices with varying power levels and adapting to power changes during power ramp-up phases. The overcurrent reference voltage used for overcurrent protection is dynamically adjusted to ensure the reliability of the overcurrent protection circuit.

[0064] Please see the appendix Figure 1The overcurrent protection circuit proposed in this invention includes: multiple sampling circuits, superposition circuits, and protection circuits;

[0065] Each sampling circuit is equipped with a reference voltage, which is set to match the power level of the device to be protected. Different sampling circuits have different reference voltages. When the sampling voltage obtained by the sampling circuit from the device to be protected is greater than the reference voltage, a pre-protection voltage is output.

[0066] In a preferred embodiment of the present invention, three sampling circuits are provided, each with a reference voltage of U_100, U_200, and U_300, representing power levels of 100kW, 200kW, and 300kW respectively. When the power of the device to be protected is between 100kW and 200kW, the first sampling circuit can output a pre-protection voltage, while the second and third sampling circuits will not output a pre-protection voltage.

[0067] When the power of the device to be protected is between 200kW and 300kW, the first and second sampling circuits can output the pre-protection voltage, while the third sampling circuit will not output the pre-protection voltage.

[0068] When the power of the device to be protected is greater than 300kW, the first sampling circuit, the second sampling circuit, and the third sampling circuit can all output a pre-protection voltage.

[0069] The superposition circuit is used to superimpose all the output pre-protection voltages with the fixed voltage to generate the first protection voltage for output. The pre-protection voltages output by all sampling circuits can be the same, such as 1V.

[0070] When the power level of the device to be protected is between 100kW and 200kW, since only one sampling circuit can output the pre-protection voltage, the superposition circuit will generate the first protection voltage by superimposing the fixed voltage and the 1V voltage.

[0071] When the power of the device to be protected is between 200kW and 300kW, both the first sampling circuit and the second sampling circuit can output a pre-protection voltage. The superposition circuit generates the first protection voltage by superimposing a fixed voltage and a 2V voltage.

[0072] When the power of the device to be protected is greater than 300kW, the first sampling circuit, the second sampling circuit, and the third sampling circuit can all output a pre-protection voltage. The superposition circuit will generate the first protection voltage based on the superposition of the fixed voltage and the 3V voltage.

[0073] Under this design, the present invention can output different first protection voltages based on different power levels. The power of the device to be protected is determined by its model and operating conditions. Therefore, the present invention can dynamically adjust the first protection voltage, i.e., the overcurrent reference voltage, according to the selection and operating conditions of the device to be protected.

[0074] The protection circuit is the execution unit of this invention. It can obtain the sampling signal of the real-time current from the device to be protected and compare it with the overcurrent reference voltage. The overcurrent reference voltage can be the first protection voltage. When the sampling signal of the real-time current is greater than the overcurrent reference voltage, the protection circuit can quickly pull down the overcurrent signal to perform overcurrent protection.

[0075] In other words, based on the above scheme, the present invention can provide different first protection voltages at different power levels by superimposing circuits and cooperating with multiple sampling circuits. It can not only dynamically adjust the overcurrent reference voltage used for overcurrent protection during the power rise stage of the device to be protected, but also adapt to devices to be protected at different power levels, realizing a universal design with one circuit for multiple uses.

[0076] Please see the appendix Figure 2 In another embodiment of the present invention, the overcurrent protection circuit further includes a constant voltage circuit and a switching circuit. The constant voltage circuit is provided to further adapt to the operating conditions of the device to be protected. The cooperation between the sampling circuit and the superposition circuit will cause the first protection voltage to change with the power. It is generally used in the power rise stage of the device to be protected. After the device to be protected is running stably, it will enter the power stabilization stage. The constant voltage circuit is provided to output a stable second protection voltage for overcurrent protection in the power stabilization stage.

[0077] The constant voltage circuit has at least a heating resistor that generates heat using the main circuit current of the device to be protected, and a thermistor placed close to the heating resistor;

[0078] Specifically, the constant voltage circuit can generate a current that is proportionally reduced to the main circuit current in the protected equipment through a current transformer. This proportionally reduced current will flow through the heating resistor. Under the power stability stage, this current will also be relatively stable. The temperature of the heating resistor is positively correlated with the current. When the current is stable, the temperature of the heating resistor will also be relatively stable. The resistance of the thermistor changes with the temperature. After the temperature stabilizes, the resistance of the thermistor will also stabilize.

[0079] This invention obtains a fixed voltage through a thermistor as the input to a constant voltage circuit. After the thermistor's resistance value stabilizes, the constant voltage circuit will be connected to a stable voltage and finally output a stable second protection voltage.

[0080] Repeated tests revealed that, with this design, the second protection voltage changes by no more than 1% within one minute during the power stabilization phase, enabling long-term stable protection.

[0081] The switching circuit is used to switch between the first protection voltage and the second protection voltage. As mentioned earlier, the first protection voltage is mainly used in the power boost stage. Therefore, in this stage, the first protection voltage can be output by the switching circuit as the overcurrent protection voltage. The second protection voltage is mainly used in the power stabilization stage. Therefore, in this stage, the second protection voltage can be output by the switching circuit as the overcurrent protection voltage.

[0082] Based on this design, the present invention can switch between the first protection voltage and the second protection voltage as the overcurrent reference voltage for overcurrent protection. During the power rise phase, the dynamically adjustable first protection voltage can be used as the overcurrent reference voltage, while during the power stabilization phase, the long-term stable second protection voltage can be used as the overcurrent reference voltage, thus achieving reliable protection for the equipment under all operating conditions.

[0083] Specifically, each sampling circuit in this invention includes a first comparator, and a first resistor and a second resistor connected to the first comparator;

[0084] The non-inverting input of the first comparator is connected to the device to be protected to obtain a sampling signal. The inverting input of the first comparator is connected to a reference voltage. The output of the first comparator is connected to a second resistor and outputs a pre-protection voltage. One end of the first resistor is connected between the output of the first comparator and the second resistor, and the other end of the first resistor is connected to a fixed voltage.

[0085] In a preferred embodiment of the present invention, three sampling circuits are provided; please refer to the appendix. Figure 3 The first sampling circuit has a comparator L1, a resistor R1, and a resistor R2;

[0086] The comparator L1 serves as the first comparator, resistor R1 serves as the first resistor, and resistor R2 serves as the second resistor. The inverting input of comparator L1 is connected to U_100, which represents the reference voltage at a power level of 100kW. The non-inverting input of comparator L1 is connected to U_IDC, which represents the sampling signal of the real-time current of the device to be protected. The output of comparator L1 is connected to resistor R2 and outputs OC1, which represents the pre-protection voltage output by the first sampling circuit. One end of resistor R1 is connected between the output of comparator L1 and resistor R2, and the other end of resistor R1 is connected to a 1V voltage, which is also a fixed voltage.

[0087] In this design, resistor R1 is a pull-up resistor and resistor R2 is a current-limiting resistor. When the power level of the device to be protected is greater than 100kW, comparator L1 will output OC1 signal. At the same time, it will be pulled high to 1V under the control of pull-up resistor R1, which means it will output a 1V pre-protection voltage.

[0088] When the power level of the device to be protected is less than 100kW, the comparator L1 outputs a low level and there is no OC1 signal, which can be regarded as a pre-protection voltage of 0V.

[0089] Please see the appendix Figure 4 The second sampling circuit has comparator L2, resistor R3, and resistor R4;

[0090] The comparator L2 serves as the first comparator, resistor R3 serves as the first resistor, and resistor R4 serves as the second resistor. The inverting input of comparator L2 is connected to U_200, which represents the reference voltage at a power level of 200kW. The non-inverting input of comparator L2 is connected to U_IDC, which represents the sampling signal of the real-time current of the device to be protected. The output of comparator L2 is connected to resistor R4 and outputs OC2, which represents the pre-protection voltage output by the second sampling circuit. One end of resistor R3 is connected between the output of comparator L2 and resistor R4, and the other end of resistor R3 is connected to a 1V voltage, which is also a fixed voltage.

[0091] In this design, resistor R3 is a pull-up resistor and resistor R4 is a current-limiting resistor. When the power level of the device to be protected is greater than 200kW, comparator L2 will output OC2 signal, and at the same time, it will be pulled high to 1V under the control of pull-up resistor R3, that is, it will output a 1V pre-protection voltage.

[0092] When the power level of the device to be protected is less than 200kW, the comparator L2 outputs a low level and there is no OC2 signal, which can be regarded as a pre-protection voltage of 0V.

[0093] Please see the appendix Figure 5 The third sampling circuit has comparator L2, resistor R5, and resistor R6;

[0094] The comparator L3 serves as the first comparator, resistor R5 as the first resistor, and resistor R6 as the second resistor. The inverting input of comparator L3 is connected to U_300, which represents the reference voltage at a power level of 300kW. The non-inverting input of comparator L3 is connected to U_IDC, which represents the sampling signal of the real-time current of the device to be protected. The output of comparator L3 is connected to resistor R6 and outputs OC3, which represents the pre-protection voltage output by the third sampling circuit. One end of resistor R5 is connected between the output of comparator L3 and resistor R6, and the other end of resistor R5 is connected to a 1V voltage, which is also a fixed voltage.

[0095] In this design, resistor R5 is a pull-up resistor and resistor R6 is a current-limiting resistor. When the power level of the device to be protected is greater than 300kW, comparator L3 will output OC2 signal, and at the same time, it will be pulled high to 1V under the control of pull-up resistor R5, that is, it will output a 1V pre-protection voltage.

[0096] When the power level of the device to be protected is less than 300kW, the comparator L3 outputs a low level and there is no OC3 signal, which can be regarded as a pre-protection voltage of 0V.

[0097] After designing the above three sampling circuits, if the power level of the device to be protected is less than 100kW, there will be no pre-protection voltage output, and the superposition circuit will output a fixed voltage of 1V.

[0098] If the power level of the device to be protected is between 100kW and 200kW, it will receive a 1V pre-protection voltage. The superposition circuit outputs a fixed voltage and a 2V voltage after superimposing the pre-protection voltage.

[0099] If the power level of the device to be protected is between 200kW and 300kW, it will receive two 1V pre-protection voltages. The superposition circuit outputs a fixed voltage and a 3V voltage after the two pre-protection voltages are superimposed.

[0100] If the power rating of the device to be protected is greater than 300kW, it will receive three 1V pre-protection voltages. The superposition circuit outputs a fixed voltage and a 4V voltage after the three pre-protection voltages are superimposed.

[0101] Accordingly, the present invention can provide a first protection voltage that varies with power through the design of multiple sampling circuits and superposition circuits, which can cope with the protected equipment of different power levels, automatically adjust the overcurrent protection value, and cope with various operating conditions of different power levels of the protected equipment such as low load, rated, and overload, thereby improving the reliability of the overcurrent protection circuit.

[0102] The design of the sampling circuit is mainly based on the power level of the device to be protected. The specific number of sampling circuits is not limited. By adding more sampling circuits and setting the interval of the reference voltage to be smaller, a more accurate first protection voltage corresponding to the power level can be output.

[0103] Please see the appendix Figure 6 The superimposed circuit in this invention includes: resistors R7, R8, R9, R10, and R11; capacitors C1, C2, and C3; and amplifier U1.

[0104] A fixed voltage is applied to the non-inverting input terminal of amplifier U1, and the inverting input terminal of amplifier U1 is connected to ground after being connected to resistor R10. The output terminal of amplifier U1 outputs the first protection voltage.

[0105] One end of capacitor C1 is connected to the non-inverting input of amplifier U1, and the other end of capacitor C1 is connected to the pre-protection voltage output by the first sampling circuit. Resistor R7 is connected in parallel across capacitor C1.

[0106] One end of capacitor C2 is connected to the non-inverting input of amplifier U1, and the other end of capacitor C2 is connected to the pre-protection voltage output by the second sampling circuit. Resistor R8 is connected in parallel across capacitor C1.

[0107] One end of capacitor C3 is connected to the non-inverting input of amplifier U1, and the other end of capacitor C3 is connected to the pre-protection voltage output by the third sampling circuit. Resistor R9 is connected in parallel across capacitor C1.

[0108] Resistor R11 is connected between the inverting input and output terminals of amplifier U1, and capacitor C4 is connected in parallel across resistor R11.

[0109] Here, the pre-protection voltage output by the first sampling circuit is OC1, the pre-protection voltage output by the second sampling circuit is OC2, the pre-protection voltage output by the third sampling circuit is OC3, OC_BK is the first protection voltage output after superposition, 1V is a fixed voltage, and amplifier U1, resistor R11 and capacitor C4 form a voltage follower, whose output corresponds to the voltage at the non-inverting input terminal of amplifier U1.

[0110] If the power rating of the device to be protected is less than 100kW, OC1, OC2, and OC3 are all 0, and the superposition circuit will only output a fixed 1V voltage.

[0111] If the power level of the device to be protected is between 100kW and 200kW, OC1 is 1V, and OC2 and OC3 are 0V. At this time, the superposition circuit will superimpose the fixed 1V voltage with OC1 and output a 2V voltage.

[0112] If the power level of the device to be protected is between 200kW and 300kW, OC1 and OC2 are 1V and OC3 is 0V. At this time, the superposition circuit will superimpose the fixed 1V voltage with OC2 and OC3 to output a 3V voltage.

[0113] If the power rating of the device to be protected is greater than 300kW, and OC1, OC2, and OC3 are all 1V, the superposition circuit will superimpose the fixed 1V voltage with OC1, OC2, and OC3 to output a 4V voltage.

[0114] Accordingly, the present invention can provide a first protection voltage that varies with power through the design of multiple sampling circuits and superposition circuits, which can cope with the protected equipment of different power levels, automatically adjust the overcurrent protection value, and cope with various operating conditions of different power levels of the protected equipment such as low load, rated, and overload, thereby improving the reliability of the overcurrent protection circuit.

[0115] In particular, the voltage values ​​of both the sampling circuit and the superposition circuit can be set according to actual needs and are not limited to 1V.

[0116] Please see the appendix Figure 7 The constant voltage circuit in this invention includes: current transformer UND1, heating resistor RW, thermistor RT, resistor R14, resistor R15, resistor R16, capacitor C5, and amplifier U2.

[0117] The current transformer UND1 is used to generate a current proportional to the main circuit current of the device to be protected. The heating resistor RW is connected to the current transformer UND1, and the thermistor RT is placed near the heating resistor RW.

[0118] The non-inverting input of amplifier U2 is connected to the thermistor RT1 and then a fixed voltage is applied. The output of amplifier U2 is connected to resistors R15 and R16 and then grounded. The output of the constant voltage circuit is set between resistors R15 and R16 to output the second protection voltage. The inverting input of amplifier U2 is connected between the output of amplifier U2 and resistor R15.

[0119] One end of capacitor C5 is connected between the thermistor RT and the non-inverting input of amplifier U2, and the other end of capacitor C5 is grounded. Resistor R14 is connected in parallel across capacitor C5.

[0120] Among them, the current transformer UND1 has the characteristic of being able to convert the current into a smaller current value proportionally (such as converting a 1000A current value into 5A). It is connected in series with the heating resistor RW. The characteristic of the heating resistor is that the larger the current flowing through it, the more severe the heating. When the current is stable, its heating is stable and its temperature is stable. The thermistor RT is set near the heating resistor RW, and its resistance value will change with the temperature.

[0121] Resistor R14 and capacitor C5 form an RC filter circuit for temperature sampling. Resistor R15 and resistor R16 form a voltage divider to adjust the ratio of the second protection voltage to the output of amplifier U2. 5V is the fixed voltage set by this constant voltage circuit, and OC_CT is the output second protection voltage.

[0122] When the power of the device to be protected increases, the current flowing through the current transformer UND1 will increase, and the current flowing through the heating resistor RW will increase proportionally, causing the heating resistor RW to heat up and its temperature to rise. The thermistor RT collects the temperature of the heating resistor RW. The resistance of the thermistor RT changes linearly with the temperature, and the voltage supplied to the amplifier U2 also changes accordingly. After being divided by resistors R15 and R16, the second protection voltage OC_CT is output. During the power stabilization stage, since the temperature change of the heating resistor RW is relatively slow and does not fluctuate easily, it can become a constant voltage.

[0123] Experiments have shown that, through the design of the above constant voltage circuit, the output second protection voltage changes by no more than 1% within one minute, and the voltage is relatively stable.

[0124] Based on the above scheme, this invention can output different second protection voltages according to the resistance value of the thermistor through the design of a constant voltage circuit. Moreover, when the protected device is in the power stable stage and the resistance value of the thermistor does not change, the second protection voltage can be maintained within the variation range of 1%, thereby achieving long-term stable overcurrent protection.

[0125] Please see the appendix Figure 8 and appendix Figure 9 In this invention, the switching circuit includes a switching switch, the first end of the switching switch is connected to a first protection voltage, the second end of the switching switch is connected to a second protection voltage, and the third end of the switching switch outputs an overcurrent reference voltage.

[0126] The switch can switch the connection of the third terminal to the first or second terminal.

[0127] The switch is a relay K1, with the first and second terminals being the moving contacts of the relay K1, and the third terminal being the stationary contact of the relay K1. It can switch the third terminal to be connected to the first terminal or to the second terminal.

[0128] The first terminal of the switch is connected to the first protection voltage OC_BK, the second terminal is connected to the second protection voltage OC_CT, and the third terminal outputs the overcurrent reference voltage I_OC. Figure 8 When the first and third terminals of relay K1 are connected, the overcurrent reference voltage I_OC is the first protection voltage OC_BK. Figure 9 When the second and third terminals of relay K1 are connected, the overcurrent reference voltage I_OC is the second protection voltage OC_CT.

[0129] By setting this switching switch, the present invention can actively select whether to use the first protection voltage or the second protection voltage as the overcurrent reference voltage for overcurrent protection. As mentioned above, the first protection voltage is used for overcurrent protection during the voltage rise phase, and the second protection voltage is used for overcurrent protection during the voltage stabilization phase. Therefore, in the present invention, when the device to be protected is in the power rise phase, the third terminal of the switching switch is connected to the first terminal.

[0130] When the device to be protected is in a stable power phase, the third terminal of the switch is connected to the second terminal.

[0131] In other words, based on the above-mentioned scheme, the present invention can connect the first terminal and the third terminal during the power boosting stage, so that the first protection voltage can be used as the overcurrent reference voltage for overcurrent protection. This allows the overcurrent reference voltage to change with the power boosting, improving the reliability of the overcurrent protection circuit. Furthermore, during the power stabilization stage, the second terminal and the third terminal can be connected, so that the second protection voltage can be used as the overcurrent reference current for overcurrent protection, achieving long-term stable overcurrent protection.

[0132] Please see the appendix Figure 10 The protection circuit in this invention includes a second comparator, resistor R12, and resistor R13;

[0133] The non-inverting input of the second comparator is connected to the device to be protected to obtain a sampling signal. The inverting input of the second comparator is connected to the switching circuit to obtain an overcurrent reference voltage. The output of the second comparator is connected to resistor R13 and outputs an overcurrent signal for overcurrent protection. One end of resistor R12 is connected between the output of the second comparator and resistor R13, and the other end of resistor R12 is connected to a fixed voltage.

[0134] Among them, the second comparator, namely comparator L4, I_OC is the overcurrent reference voltage, which is selected as the first protection voltage or the second protection voltage through the switching circuit. U_IAC is the sampling signal of the real-time current of the device to be protected on the motor side, which corresponds to AC. The sampling circuit is set in the main current loop, and the sampling signal of the real-time current collected corresponds to DC, denoted as U_IDC.

[0135] F0 is the overcurrent signal. When the sampled signal U_IAC is greater than the overcurrent reference voltage I_OC, the comparator L4 will output a low-level signal, which will quickly pull the overcurrent signal F0 low, thereby achieving the protection effect.

[0136] Based on the above scheme, this invention can determine whether there is an overcurrent abnormality in the device to be protected by comparing the sampled voltage with the overcurrent reference voltage, and can pull the overcurrent signal low to a low level when an overcurrent abnormality occurs, thereby performing overcurrent protection and avoiding device damage caused by the overcurrent abnormality.

[0137] Please see the appendix Figure 11 Based on the above design, the workflow of this invention is as follows:

[0138] The sampling circuit samples the voltage and outputs the first protection voltage through the superposition circuit, while the constant voltage circuit outputs the second protection voltage.

[0139] Determine the operating condition of the equipment to be protected;

[0140] If the device to be protected is in the power rise stage, the switching circuit outputs the first protection voltage as the overcurrent reference voltage; if the device to be protected is in the power stability stage, the switching circuit outputs the second protection voltage as the overcurrent reference voltage.

[0141] The protection circuit monitors the real-time current on the motor side of the device under protection. When the real-time current exceeds the overcurrent reference voltage, it quickly pulls the overcurrent signal down to provide overcurrent protection.

[0142] The operating conditions of the protected equipment can be determined based on whether the second protection voltage is stable. If the second protection voltage remains basically unchanged and fluctuates little, it can be determined that the protected equipment is in the power stability stage. If the second protection voltage still fluctuates greatly, it indicates that the protected equipment is in the power increase stage.

[0143] Please see the appendix Figure 12 Based on the above design, in a specific embodiment of the present invention, the control flow is as follows:

[0144] The DC current signal U_IDC is acquired and input to comparators L1, L2, and L3 for comparison.

[0145] Output OC1, OC2, and OC3 respectively based on the comparison results;

[0146] OC1, OC2, and OC3 are applied to amplifier U1 as bias voltages and superimposed to output the first protection voltage OC_BK;

[0147] A proportionally reduced current is generated synchronously through a current transformer and flows through the heating resistor RW;

[0148] The heating resistance RW changes with the main circuit current of the device to be protected;

[0149] The thermistor RT is set near the heating resistor RW. Its resistance changes with the temperature of the heating resistor RW and outputs a second protection voltage OC_CT.

[0150] Then determine whether the second protection voltage OC_CT is constant;

[0151] If not, the first protection voltage OC_BK is connected to the back end as the overcurrent reference voltage I_OC through relay K1 until the second protection voltage OC_CT becomes constant.

[0152] If so, the second protection voltage OC_CT is connected to the back end via relay K1 as the overcurrent reference voltage I_OC;

[0153] The sampling signal U_IAC of the real-time current on the motor side is acquired in real time and compared with the overcurrent reference voltage I_OC. If the sampling signal U_IAC is greater than the overcurrent reference voltage I_OC, the overcurrent signal F0 is pulled low to perform overcurrent protection.

[0154] Based on the above process, the present invention can handle the protection of equipment with different power levels, automatically adjust the overcurrent protection value, and can handle various operating conditions of different power levels such as low load, rated load, and overload of the protected equipment, and is compatible with various models.

[0155] The present invention also proposes an air conditioning system having a drive circuit connected to the aforementioned overcurrent protection circuit.

[0156] Compared with the prior art, the present invention has at least the following beneficial effects:

[0157] 1. Through the design of multiple sampling circuits and superposition circuits, this invention can provide a first protection voltage that varies with power, can cope with the protected equipment of different power levels, automatically adjust the overcurrent protection value, and can cope with various operating conditions of different power levels of the protected equipment such as low load, rated load, and overload, thus improving the reliability of the overcurrent protection circuit.

[0158] 2. Through the design of a constant voltage circuit, this invention can output different second protection voltages according to the resistance value of the thermistor. Moreover, when the protected device is in a stable power stage and the resistance value of the thermistor does not change, the second protection voltage can be maintained within a 1% variation range to achieve long-term stable overcurrent protection.

[0159] 3. This invention can be adapted to a variety of models without the need to set different reference protection voltage configuration circuits for different models, thus realizing a universal design with one circuit for multiple uses.

[0160] It should be noted that the terminology used above is for describing specific embodiments only and is not intended to limit the exemplary embodiments of the present invention. When the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. The order of execution of actions, steps, etc., in the apparatus and methods in the specification and drawings can be implemented in any order unless a specific express order is specified, and as long as the output of a previous process is not used in a subsequent process. Similar sequential terms used for ease of description do not imply that such an order must be followed.

[0161] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as constraints. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0162] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An overcurrent protection circuit, comprising a plurality of sampling circuits connected to the device to be protected, and a protection circuit for performing overcurrent protection, characterized in that, It also includes a superposition circuit connected to the plurality of the sampling circuits; Each of the sampling circuits is provided with a reference voltage, which is set to match the power level of the device to be protected. The reference voltages set for different sampling circuits are different. When the sampling signal obtained by the sampling circuit from the device to be protected is greater than the reference voltage, a pre-protection voltage is output. The superposition circuit is used to superimpose all the pre-protection voltages and output a first protection voltage. The protection circuit can use the first protection voltage as an overcurrent reference voltage to provide overcurrent protection for the device to be protected.

2. The overcurrent protection circuit according to claim 1, characterized in that, The overcurrent protection circuit also includes a constant voltage circuit, which has at least a heating resistor that uses the main circuit current of the device to be protected to generate heat, and a thermistor disposed near the heating resistor. The constant voltage circuit is used to output a second protection voltage, and the magnitude of the second protection voltage is controlled by the resistance value of the thermistor. The protection circuit can use the second protection voltage as an overcurrent reference voltage to provide overcurrent protection for the device to be protected.

3. The overcurrent protection circuit according to claim 2, characterized in that, The overcurrent protection circuit further includes a switching circuit, which is connected to the superposition circuit and the constant voltage circuit. The switching circuit is used to switch the output of the first protection voltage or the second protection voltage to the protection circuit. The protection circuit uses the output of the switching circuit as the overcurrent reference voltage.

4. The overcurrent protection circuit according to claim 1, characterized in that, Each of the sampling circuits includes a first comparator, and a first resistor and a second resistor connected to the first comparator; The non-inverting input of the first comparator is connected to the device to be protected to obtain a sampling signal. The inverting input of the first comparator is connected to the reference voltage. The output of the first comparator is connected to the second resistor and outputs the pre-protection voltage. One end of the first resistor is connected between the output of the first comparator and the second resistor, and the other end of the first resistor is connected to a fixed voltage.

5. The overcurrent protection circuit according to claim 1, characterized in that, The superimposed circuit includes: resistors R7, R8, R9, R10, and R11; capacitors C1, C2, and C3; and amplifier U1. The non-inverting input terminal of the amplifier U1 is connected to a fixed voltage, the inverting input terminal of the amplifier U1 is connected to the resistor R10 and then grounded, and the output terminal of the amplifier U1 outputs the first protection voltage. One end of capacitor C1 is connected to the non-inverting input terminal of amplifier U1, and the other end of capacitor C1 is connected to the pre-protection voltage output by the first sampling circuit. Resistor R7 is connected in parallel across capacitor C1. One end of capacitor C2 is connected to the non-inverting input terminal of amplifier U1, and the other end of capacitor C2 is connected to the pre-protection voltage output by the second sampling circuit. Resistor R8 is connected in parallel across capacitor C1. One end of capacitor C3 is connected to the non-inverting input terminal of amplifier U1, and the other end of capacitor C3 is connected to the pre-protection voltage output by the third sampling circuit. Resistor R9 is connected in parallel across capacitor C1. The resistor R11 is connected between the inverting input terminal and the output terminal of the amplifier U1, and the capacitor C4 is connected in parallel across the resistor R11.

6. The overcurrent protection circuit according to claim 2, characterized in that, The constant voltage circuit includes: current transformer UND1, heating resistor RW, thermistor RT, resistor R14, resistor R15, resistor R16, capacitor C5, and amplifier U2. The current transformer UND1 is used to generate a current proportional to the main circuit current of the device to be protected. The heating resistor RW is connected to the current transformer UND1, and the thermistor RT is placed near the heating resistor RW. The non-inverting input terminal of the amplifier U2 is connected to the thermistor RT1 and then a fixed voltage is applied. The output terminal of the amplifier U2 is connected to the resistors R15 and R16 and then grounded. The output terminal of the constant voltage circuit is set between the resistors R15 and R16 to output the second protection voltage. The inverting input terminal of the amplifier U2 is connected between the output terminal of the amplifier U2 and the resistor R15. One end of the capacitor C5 is connected between the thermistor RT and the non-inverting input terminal of the amplifier U2, and the other end of the capacitor C5 is grounded. The resistor R14 is connected in parallel across the capacitor C5.

7. The overcurrent protection circuit according to claim 3, characterized in that, The switching circuit includes a switching switch, the first terminal of which is connected to the first protection voltage, the second terminal of which is connected to the second protection voltage, and the third terminal of which outputs the overcurrent reference voltage. The switch can switch the third terminal to be connected to the first terminal or the second terminal.

8. The overcurrent protection circuit according to claim 7, characterized in that, When the device to be protected is in the power boost phase, the third terminal of the switching switch is connected to the first terminal; When the device to be protected is in a power stable phase, the third terminal of the switching switch is connected to the second terminal.

9. The overcurrent protection circuit according to claim 7, characterized in that, The protection circuit includes a second comparator, resistor R12, and resistor R13; The inverting input of the second comparator is connected to the device to be protected to obtain a sampling signal, the non-inverting input of the second comparator is connected to the switching circuit to obtain the overcurrent reference voltage, the output of the second comparator is connected to the resistor R13 and outputs an overcurrent signal for overcurrent protection, one end of the resistor R12 is connected between the output of the second comparator and the resistor R13, and the other end of the resistor R12 is connected to a fixed voltage.

10. An air conditioning system, characterized in that, The air conditioning system has a drive circuit, which is connected to an overcurrent protection circuit as described in any one of claims 1 to 9.

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