Overcurrent protection circuit and power supply circuit

Abstract

The utility model relates to the technical field of power electronics, and discloses an overcurrent protection circuit and a power supply circuit, the overcurrent protection circuit comprises a voltage sampling circuit, a current sampling circuit, a voltage threshold determination circuit and a current threshold determination circuit, the second input end inputs reference voltage, and the output end is connected with the first input end of the current threshold judgment circuit; the second input end of the current threshold judgment circuit inputs the output current of the to-be-protected equipment, and the output end of the current threshold judgment circuit is connected with the control end of the to-be-protected equipment; when the voltage threshold judgment circuit judges that the bus voltage is smaller than or larger than the reference voltage, the absolute value of an overcurrent protection point in the current threshold judgment circuit is a first current value or a second current value, and the first current value is larger than the second current value. According to the utility model, when the bus voltage is higher than a threshold value, an over-current protection point is lowered, so that the device stress and turn-off loss of equipment to be protected are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronics, in particular to an overcurrent protection circuit and a power supply circuit. Background Art

[0002] The inverter side of the existing photovoltaic grid-connected inverter basically adopts one hardware overcurrent protection point within the full voltage operating range. Considering the limitations of the safe working area of ​​the inverter power device, it is necessary to ensure that the shutdown stress of the corresponding power device does not exceed the standard limit of the dynamic stress of the power device when the hardware overcurrent protection is triggered at the highest voltage point. Therefore, the selection of the shutdown drive resistor is generally larger, which further increases the shutdown loss, increases the total loss, increases the heat generation of the module, and reduces the efficiency of the whole machine. At the same time, it also increases the volume and weight of the radiator and chassis accordingly, further increasing the cost of the whole machine. Utility Model Content

[0003] Therefore, the technical problem to be solved by the utility model is to solve the problem in the prior art that when the inverter bus voltage is higher than the threshold, the overcurrent protection point of the overcurrent protection circuit is high, resulting in high inverter shutdown loss, thereby providing an overcurrent protection circuit and a power supply circuit.

[0004] In order to achieve the above object, the utility model provides the following technical solutions:

[0005] In a first aspect, the utility model provides an overcurrent protection circuit, comprising: a voltage sampling circuit, a current sampling circuit, a voltage threshold determination circuit and a current threshold determination circuit, wherein the voltage sampling circuit, its input end inputs the bus voltage of the device to be protected, and its output end is connected to the first input end of the voltage threshold determination circuit; the voltage threshold determination circuit, its second input end inputs the reference voltage, and its output end is connected to the first input end of the current threshold determination circuit, and is used to compare the bus voltage with the reference voltage and output the comparison result; the current sampling circuit, its input end is connected to the output end of the device to be protected, and its output end is connected to the second input end of the current threshold determination circuit, and is used to collect the output current of the device to be protected; the current threshold determination circuit, its output end is connected to the control end of the device to be protected, and is used to switch the switch state according to the comparison result, so that when the bus voltage is greater than the reference voltage, the absolute value of the overcurrent protection point inside it is less than the absolute value of the overcurrent protection point inside it when the bus voltage is less than the reference voltage; when the current threshold determination circuit determines that the absolute value of the output current is greater than the absolute value of the overcurrent protection point, the current threshold determination circuit controls the device to be protected to stop working.

[0006] The overcurrent protection circuit provided by the utility model can adjust the size of the overcurrent protection point according to the bus voltage of the device to be protected. When the voltage threshold determination circuit determines that the bus voltage of the device to be protected is greater than the reference voltage, the bus of the device to be protected is in a high voltage state, and by switching the switch state of the current threshold determination circuit, the voltage division state in the current threshold determination circuit is made, so that the absolute value of the overcurrent point in the current threshold determination circuit is reduced, so that when the current threshold determination circuit determines that the device to be protected is overcurrent, the output current of the device to be protected is in a lower state, the shutdown loss of the device to be protected is reduced, the heating of components in the device to be protected caused by large current is avoided, and the service life of the device to be protected is increased. At the same time, due to the reduction in heat generation, the volume of the radiator of the device to be protected can be reduced, and the cost of the whole machine is further reduced.

[0007] In an optional embodiment, the voltage sampling circuit includes: an input signal processing circuit and a first differential operational amplifier circuit, wherein the input signal processing circuit has a first input terminal that inputs the positive bus voltage of the device to be protected, a second input terminal that inputs the negative bus voltage of the device to be protected, a first output terminal that is connected to the first input terminal of the first differential operational amplifier circuit, and a second output terminal that is connected to the second input terminal of the first differential operational amplifier circuit, and is used to limit the magnitude of the current flowing from the bus into the first differential operational amplifier circuit; the first differential operational amplifier circuit has an output terminal that is connected to the first input terminal of the voltage threshold determination circuit, and is used to amplify the voltage difference between the positive and negative ends of the bus and output it.

[0008] In an optional embodiment, the current sampling circuit includes: a current sensor and a second differential operational amplifier circuit, wherein the current sensor has an input end connected to the output end of the device to be protected, a first output end connected to the first input end of the second differential operational amplifier circuit, and a second output end connected to the second input end of the second differential operational amplifier circuit, and converts the sampled current of the device to be protected into a voltage signal and a reference signal and then inputs them into the second differential operational amplifier circuit; the second differential operational amplifier circuit has an output end connected to the second input end of the current threshold determination circuit, and is used to amplify the voltage difference between the voltage signal and the reference signal and output it as the output current of the device to be protected.

[0009] In an optional embodiment, the voltage threshold determination circuit includes: a first comparison circuit and a filter circuit, wherein the first comparison circuit has a first input terminal connected to the first power supply, a second input terminal inputting the bus voltage, and an output terminal connected to the first terminal of the filter circuit, which obtains a reference voltage based on the first power supply voltage division, and outputs a comparison result after comparing the bus voltage with the reference voltage; a filter circuit has a second terminal connected to the first power supply, a third terminal connected to ground, and a fourth terminal connected to the first input terminal of the current threshold determination circuit, and is used to filter out interference signals in the comparison result; when the first comparison circuit determines that the bus voltage is less than the reference voltage, the first comparison circuit outputs a first level signal; when the first comparison circuit determines that the bus voltage is greater than the reference voltage, the first comparison circuit outputs a second level signal; the first level signal and the second level signal have different high and low states.

[0010] In an optional embodiment, the current threshold determination circuit includes: a first current threshold determination branch and a second current threshold determination branch, wherein the first current threshold determination branch, whose first input end is connected to the first input end of the second current threshold determination branch and then inputs a first level signal or a second level signal, whose second input end is connected to the second input end of the second current threshold determination branch and then inputs an output current, whose output end is connected to the output end of the second current threshold determination branch and the control end of the device to be protected, whose first end is connected to the first power supply, and whose second end is connected to the first end of the second current threshold determination branch; the second current threshold determination branch, whose second end is connected to the first A power supply connection; when the current threshold determination circuit receives a first level signal, the first current threshold determination branch and the second current threshold determination branch switch the switch state, so that the absolute values ​​of the positive overcurrent protection point in the first current threshold determination branch and the negative overcurrent point in the second current threshold determination branch are both the first current value; when the current threshold determination circuit receives a second level signal, the first current threshold determination branch and the second current threshold determination branch switch the switch state, so that the absolute values ​​of the positive overcurrent protection point in the first current threshold determination branch and the negative overcurrent point in the second current threshold determination branch are both the second current value; the first current value is greater than the second current value.

[0011] The overcurrent protection circuit provided by the utility model has a first current threshold determination branch and a second current threshold determination branch that respectively provide a positive overcurrent point and a negative overcurrent point, so that the overcurrent protection function can be achieved regardless of whether the output current of the device to be protected is positive or negative, and has a wide range of applications.

[0012] In an optional embodiment, the first current threshold determination branch includes: a first switching circuit and a second comparison circuit, wherein the first switching circuit, whose control end is connected to the first input end of the second current threshold determination branch and then inputs a first level signal or a second level signal, whose first end is connected to the first input end of the second comparison circuit, and whose second end is connected to the first end of the second current threshold determination branch, and which is used to switch the switch state based on the first level signal and the second level signal, so that the absolute value of the voltage at the first input end of the second comparison circuit is the first current value; the second comparison circuit, whose second input end is connected to the second input end of the second current threshold determination branch and then inputs an output current, and whose output end is connected to the control end of the device to be protected; if the second comparison circuit determines that the absolute value of the output current is greater than the first current value, the second comparison circuit controls the device to be protected to stop working.

[0013] In an optional embodiment, the first switching circuit includes: a first switch, a first diode, a first resistor, a second resistor and a third resistor, wherein the first switch, whose control end is connected to the first end of the first resistor and the first end of the second resistor, whose first end is connected to the second end of the second resistor and the first input end of the second comparison circuit, and whose second end is connected to the first end of the third resistor; the first resistor, whose second end is connected to the anode of the first diode; the first diode, whose cathode is connected to the first input end of the second current threshold determination branch and then inputs the first level signal or the second level signal; the third resistor, whose second end is connected to the first end of the second current threshold determination branch; when the cathode of the first diode receives the first level signal, the first diode is turned off and the first switch is turned off; when the cathode of the first diode receives the second level signal, the first diode is turned on and the first switch is turned on.

[0014] In an optional embodiment, the second current threshold determination branch includes: a second switching circuit and a third comparison circuit, wherein the second switching circuit, whose control end is connected to the control end of the first switching circuit and then inputs a first level signal or a second level signal, whose first end is connected to the first input end of the third comparison circuit, and whose second end is connected to the first power supply and the first end of the third comparison circuit, and is used to switch the switch state based on the first level signal and the second level signal, so that the absolute value of the voltage at the first input end of the third comparison circuit is the second current value; the third comparison circuit, whose second input end is connected to the second input end of the second comparison circuit and then inputs an output current, whose output end is connected to the control end of the device to be protected, and whose second end is connected to the second end of the first switching circuit; if the third comparison circuit determines that the absolute value of the output current is greater than the second current value, the third comparison circuit controls the device to be protected to stop working.

[0015] In an optional embodiment, the second switching circuit includes: a second switch, a second diode, a fourth resistor, a fifth resistor and a sixth resistor, wherein the second switch, whose control end is connected to the first end of the fourth resistor and the first end of the fifth resistor, whose first end is connected to the first end of the sixth resistor, and whose second end is connected to the second end of the fifth resistor and the first end of the third comparison circuit; the fourth resistor, whose second end is connected to the anode of the second diode; the second diode, whose cathode is connected to the cathode of the first diode and then inputs the first level signal or the second level signal; the sixth resistor, whose second end is connected to the first input end of the third comparison circuit; when the cathode of the second diode receives the first level signal, the second diode is turned off and the second switch is turned off; when the cathode of the second diode receives the second level signal, the second diode is turned on and the second switch is turned on.

[0016] The overcurrent protection circuit provided by the utility model uses the on-off state of the first switch and the second switch to adjust the voltage division state in the current threshold determination circuit, so that the switch cost is low, the response speed is fast, and the efficiency of the overcurrent protection is improved.

[0017] In a second aspect, the utility model provides a power supply circuit, comprising: an inverter and the overcurrent protection circuit of the first aspect, wherein a voltage sampling circuit, whose input end collects the positive bus voltage and the negative bus voltage of the inverter and then outputs the processed bus voltage; a current sampling circuit, whose input end collects the current at the output end of the inverter and then outputs the output current; when the voltage threshold determination circuit determines that the bus voltage is less than a reference voltage, the current threshold determination circuit switches the switch state so that the absolute value of the overcurrent protection point in the current threshold determination circuit is a first current value; when the voltage threshold determination circuit determines that the bus voltage is greater than the reference voltage, the current threshold determination circuit switches the switch state so that the absolute value of the overcurrent protection point in the current threshold determination circuit is a second current value; when the current threshold determination circuit determines that the absolute value of the output current is greater than the first current value or the second current value, the current threshold determination circuit controls the inverter to seal.

[0018] The power supply circuit provided by the utility model can adjust the size of the overcurrent protection point according to the bus voltage of the inverter. When the voltage threshold determination circuit determines that the bus voltage of the inverter is greater than the reference voltage, the bus of the inverter is in a high voltage state, and by switching the switch state of the current threshold determination circuit, the voltage division state in the current threshold determination circuit is made, so that the absolute value of the overcurrent point in the current threshold determination circuit is reduced, so that when the current threshold determination circuit determines that the inverter is overcurrent and needs to shut down the output for wave blocking, the output current of the inverter is in a lower state, thereby reducing the device stress and shutdown loss of the inverter, avoiding the heating of the components in the inverter caused by the large current, and increasing the service life of the inverter. At the same time, due to the reduction in heat generation, the volume of the inverter's heat sink can be reduced, further reducing the cost of the whole machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a composition diagram of a specific example of an overcurrent protection circuit according to an embodiment of the utility model;

[0021] Figure 2 is a structural diagram of a specific circuit of a voltage sampling circuit according to an embodiment of the utility model;

[0022] Figure 3 is a structural diagram of a specific circuit of a current sampling circuit according to an embodiment of the utility model;

[0023] Figure 4 is a structural diagram of a specific circuit of a voltage threshold determination circuit according to an embodiment of the utility model;

[0024] Figure 5 is a structural diagram of a specific circuit of a current threshold determination circuit according to an embodiment of the utility model;

[0025] Figure 6 is a composition diagram of a specific example of a power supply circuit according to an embodiment of the utility model;

[0026] Figure 7 It is a flow chart of inverter overcurrent protection according to an embodiment of the utility model. DETAILED DESCRIPTION

[0027] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0028] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0030] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The overcurrent protection point of the overcurrent protection circuit is generally a fixed value. It is necessary to ensure that the protection action of the overcurrent protection circuit is triggered at the highest point of the bus voltage or output voltage of the device to be protected. At the same time, the shutdown stress of the power device of the device to be protected cannot exceed the standard limit of the dynamic stress of the power device. Therefore, in the case of overvoltage, a large-resistance shutdown drive resistor is generally set in the device to be protected to reduce the impact of high current on circuit components during the overcurrent protection shutdown process. The large-resistance resistor will increase the heat generated under the action of high current, thereby increasing the shutdown loss of the circuit and reducing the shutdown efficiency of the device to be protected.

[0032] To overcome the above defects, this embodiment provides an overcurrent protection circuit, such as Figure 1 As shown, it includes: a voltage sampling circuit 1, a current sampling circuit 2, a voltage threshold determination circuit 3 and a current threshold determination circuit 4.

[0033] like Figure 1 As shown, the voltage sampling circuit 1 has its input terminal inputting the bus voltage BUS+_COM of the device to be protected, and its output terminal connected to the first input terminal of the voltage threshold determination circuit 3 .

[0034] like Figure 1As shown, the current sampling circuit 2 has its input end connected to the output end of the device to be protected, and its output end connected to the second input end of the current threshold determination circuit 4, which is used to collect the output current R_LIMT of the device to be protected.

[0035] For example, Figure 1 In the embodiment, the device to be protected can be an inverter, the voltage sampling circuit 1 can collect the bus voltage, input voltage, output voltage, etc. of the inverter, and the current sampling circuit 2 can collect the bus current, input current, output current, etc. of the inverter, so that the overcurrent protection circuit can monitor the voltage and current of the inverter and perform overcurrent protection.

[0036] like Figure 1 As shown, the voltage threshold determination circuit 3 has a second input terminal inputting a reference voltage REF0, and an output terminal connected to a first input terminal of a current threshold determination circuit 4, which is used to compare the bus voltage BUS+_COM with the reference voltage REF0 and output a comparison result.

[0037] Specifically, Figure 1 In the example, the voltage threshold determination circuit 3 obtains the bus voltage BUS+_COM of the device to be protected through the voltage sampling circuit 1, and compares the bus voltage BUS+_COM with the reference voltage REF0 to obtain the following three output results:

[0038] (1) If the bus voltage BUS+_COM is less than the reference voltage REF0, it indicates that the bus voltage BUS+_COM of the device to be protected is in the low voltage area, and the voltage threshold determination circuit 3 outputs a first level signal;

[0039] (2) If the bus voltage BUS+_COM is greater than the reference voltage REF0, it indicates that the bus voltage BUS+_COM of the device to be protected is in the high voltage region, and the voltage threshold determination circuit 3 outputs a second level signal, wherein the second level signal is different from the first level signal in level voltage;

[0040] (3) If the bus voltage BUS+_COM is equal to the reference voltage REF0, the voltage threshold determination circuit 3 does not output any signal.

[0041] like Figure 1 As shown, the output end of the current threshold determination circuit 4 is connected to the control end of the device to be protected.

[0042] Figure 1 In the figure, the current threshold determination circuit 4 is used to switch the switch state according to the comparison result, so that when the bus voltage BUS+_COM is greater than the reference voltage REF0, the absolute value of the internal overcurrent protection point is smaller than the absolute value of the internal overcurrent protection point when the bus voltage BUS+_COM is less than the reference voltage REF0.

[0043] Figure 1 In the embodiment, when the current threshold determination circuit 4 determines that the absolute value of the output current R_LIMT is greater than the absolute value of the overcurrent protection point, the current threshold determination circuit 4 controls the device to be protected to stop working.

[0044] Specifically, Figure 1 In the embodiment, the current threshold determination circuit 4 has the following three response states based on the determination result of the voltage threshold determination circuit 3 and the magnitude of the output current R_LIMT:

[0045] (1) When the first input terminal of the current threshold determination circuit 4 receives a first voltage signal, the current threshold determination circuit 4 switches its own switch state based on the first voltage signal to adjust the voltage division state of the internal circuit, so that the absolute value of the internal overcurrent protection point is the first current value. If the current threshold determination circuit 4 determines that the absolute value of the output current R_LIMT is greater than the first current value, the current threshold determination circuit 4 outputs a drive signal to shut down the device to be protected, thereby realizing overcurrent protection for the device to be protected.

[0046] (2) When the first input terminal of the current threshold determination circuit 4 receives the second voltage signal, the current threshold determination circuit 4 switches its own switch state based on the second voltage signal to adjust the voltage division state of the internal circuit, so that the absolute value of the internal overcurrent protection point is the second current value. After that, the current threshold determination circuit 4 compares the output current R_LIMT with the second current value. If the current threshold determination circuit 4 determines that the absolute value of the output current R_LIMT is greater than the second current value, the current threshold determination circuit 4 outputs a drive signal to shut down the device to be protected, so as to achieve overcurrent protection for the device to be protected.

[0047] (3) If the current threshold determination circuit 4 determines that the absolute value of the output current R_LIMT is not greater than the first current value or not greater than the second current value, the current threshold determination circuit 4 does not output the driving signal.

[0048] Specifically, Figure 1 In the embodiment, since the overcurrent protection point of the corresponding current threshold judgment circuit 4 is the first current value when the bus voltage BUS+_COM of the device to be protected is in the low voltage area, and the overcurrent protection point of the corresponding current threshold judgment circuit 4 is the second current value when it is in the high voltage area, and the first current value is greater than the second current value, the corresponding overcurrent protection point is lowered at high voltage, so that the shutdown current and stress borne by the internal switch during the shutdown process of the circuit to be protected are greatly reduced, thereby reducing the device stress and shutdown loss of the device to be protected, improving the shutdown efficiency, reducing the heat generation of the device to be protected, and increasing the service life of the device to be protected.

[0049] The overcurrent protection circuit provided in this embodiment can adjust the size of the overcurrent protection point according to the bus voltage of the device to be protected. When the voltage threshold determination circuit determines that the bus voltage of the device to be protected is greater than the reference voltage, the bus of the device to be protected is in a high voltage state, and by switching the switch state of the current threshold determination circuit, the voltage division state in the current threshold determination circuit is made, so that the absolute value of the overcurrent point in the current threshold determination circuit is reduced, so that when the current threshold determination circuit determines that the device to be protected is overcurrent, the output current of the device to be protected is in a lower state, reducing the shutdown loss of the device to be protected, avoiding the heating of components in the device to be protected caused by large current, and increasing the service life of the device to be protected. At the same time, due to the reduction in heat generation, the volume of the heat sink of the device to be protected can be reduced, further reducing the cost of the whole machine.

[0050] In some optional embodiments, such as Figure 2 As shown, the voltage sampling circuit 1 includes: an input signal processing circuit 11 and a first differential operational amplifier circuit 12, wherein the input signal processing circuit 11, its first input terminal inputs the positive bus voltage BUS+ of the device to be protected, its second input terminal inputs the negative bus voltage BUS- of the device to be protected, its first output terminal is connected to the first input terminal of the first differential operational amplifier circuit 12, and its second output terminal is connected to the second input terminal of the first differential operational amplifier circuit 12; the first differential operational amplifier circuit 12, its output terminal (i.e., one end outputting the bus voltage BUS+_COM) is connected to the first input terminal (i.e., one end receiving the bus voltage BUS+_COM) of the voltage threshold determination circuit 3.

[0051] Specifically, Figure 2 In the embodiment, the input signal processing circuit 11 uses a resistor to limit the current of the input signal, and then inputs the positive bus voltage BUS+ and the negative bus voltage BUS- of the device to be protected into the positive input terminal and the negative input terminal of the first differential operational amplifier circuit 12 respectively. The first differential operational amplifier circuit 12 amplifies the difference between the positive bus voltage BUS+ and the negative bus voltage BUS- and outputs the sampled bus voltage BUS+_COM.

[0052] Optionally, the voltage sampling circuit 1 may include devices such as a single chip microcomputer and a current Hall sensor, and the specific circuit structure of the voltage sampling circuit is not limited here.

[0053] In some optional embodiments, such as Figure 3As shown, the current sampling circuit 2 includes: a current sensor 21 and a second differential operational amplifier circuit 22, wherein the current sensor 21, its input end (i.e., IN end) is connected to the output end of the device to be protected, the first output end is connected to the first input end of the second differential operational amplifier circuit 22, and the second output end is connected to the second input end of the second differential operational amplifier circuit 22; the second differential operational amplifier circuit 22, its output end (i.e., one end outputting the output current R_LIMT) is connected to the second input end of the current threshold determination circuit 3 (i.e., one end receiving the output current R_LIMT).

[0054] Specifically, Figure 3 In the embodiment, after the current sensor 21 converts the sampled current of the device to be protected into a voltage signal Vout and generates a reference signal Vref, the voltage signal Vout and the reference signal Vref are input to the second differential operational amplifier circuit 22. The second differential operational amplifier circuit 22 amplifies the voltage difference between the voltage signal Vout and the reference signal Vref and outputs it as the output current R_LIMT of the device to be protected.

[0055] Optionally, the current sensor 21 may be an electromagnetic sensor, a Hall sensor, etc., which is not limited here.

[0056] In some optional embodiments, such as Figure 4 As shown, the voltage threshold determination circuit 3 includes: a first comparison circuit 31 and a filter circuit 32, wherein the first comparison circuit 31 has a first input terminal connected to the first power supply +3.3V, a second input terminal inputting the bus voltage BUS+_COM, and an output terminal connected to the first terminal of the filter circuit 32, which obtains a reference voltage REF0 after voltage division based on the first power supply +3.3V, and compares the bus voltage BUS+_COM with the reference voltage REF0 and outputs a comparison result BUS_OV_PRO.

[0057] like Figure 4 As shown, the filtering circuit 32 has a second end connected to the first power supply +3.3V, a third end grounded, and a fourth end (i.e., an end outputting the comparison result BUS_OV_PRO) connected to the first input end of the current threshold determination circuit 4 (i.e., an end receiving the comparison result BUS_OV_PRO), and is used to filter out interference signals in the comparison result.

[0058] Specifically, Figure 4In the embodiment, when the first comparison circuit 31 determines that the bus voltage BUS+_COM is less than the reference voltage REF0, the first comparison circuit 31 outputs the comparison result BUS_OV_PRO with a voltage of 3.3V, and inputs 3.3V as the first level signal to the current threshold determination circuit 4 through the filter circuit 32; when the first comparison circuit 31 determines that the bus voltage BUS+_COM is greater than the reference voltage REF0, the first comparison circuit 31 outputs the comparison result BUS_OV_PRO with a voltage of 0V, and inputs 0V as the second level signal to the current threshold determination circuit 4 through the filter circuit 32.

[0059] In some optional embodiments, such as Figure 5 As shown, the current threshold determination circuit 4 includes: a first current threshold determination branch 41 and a second current threshold determination branch 42, wherein the first current threshold determination branch 41, whose first input end is connected to the first input end of the second current threshold determination branch 42 and then inputs the first level signal or the second level signal, whose second input end is connected to the second input end of the second current threshold determination branch 42 and then inputs the output current R_LIMT, whose output end is connected to the output end of the second current threshold determination branch 42 and the control end of the device to be protected, whose first end is connected to the first power supply 3.3V, and whose second end is connected to the first end of the second current threshold determination branch 42; the second current threshold determination branch 42, whose second end is connected to the first power supply 3.3V.

[0060] Specifically, Figure 5 In the figure, the first current threshold determination branch 41 and the second current threshold determination branch 42 are respectively used to perform overcurrent detection on the output current R_LIMT greater than 0V and the output current R_LIMT less than 0V, that is, no matter the output current R_LIMT of the protected device is greater than 0V or less than 0V, the current threshold determination circuit 4 can determine whether there is overcurrent, with high adaptability and wide application scenarios.

[0061] Specifically, Figure 5 In the embodiment, when the current threshold determination circuit 4 receives the first level signal, the first current threshold determination branch 41 and the second current threshold determination branch 42 switch the switch state, so that the absolute values ​​of the positive overcurrent protection point in the first current threshold determination branch 41 and the negative overcurrent point in the second current threshold determination branch are both the first current value. If the first current threshold determination branch 41 or the second current threshold determination branch 42 determines that the absolute value of the output current R_LIMT is greater than the first current value, the first current threshold determination branch 41 outputs the first drive signal RINV_LIMT_D+, or the second current threshold determination branch 42 outputs the second drive signal RINV_LIMT_D-, thereby controlling the device to be protected to stop working.

[0062] Specifically, Figure 5In the embodiment, when the current threshold determination circuit 4 receives the second level signal, the first current threshold determination branch 41 and the second current threshold determination branch 42 switch the switch state, so that the absolute values ​​of the positive overcurrent protection point 41 in the first current threshold determination branch and the negative overcurrent point in the second current threshold determination branch 42 are both the second current value. If the first current threshold determination branch 41 or the second current threshold determination branch 42 determines that the absolute value of the output current R_LIMT is greater than the second current value, the first current threshold determination branch 41 outputs the first drive signal RINV_LIMT_D+, or the second current threshold determination branch 42 outputs the second drive signal RINV_LIMT_D-, thereby controlling the device to be protected to stop working.

[0063] In some optional embodiments, such as Figure 5 As shown, the first current threshold determination branch 41 includes: a first switch circuit 411 and a second comparison circuit 412, wherein the first switch circuit 411, whose control end is connected to the first input end of the second current threshold determination branch 42 and then inputs the first level signal or the second level signal, whose first end is connected to the first input end of the second comparison circuit 412, and whose second end is connected to the first end of the second current threshold determination branch 42; the second comparison circuit 412, whose second input end is connected to the second input end of the second current threshold determination branch 42 and then inputs the output current R_LIMT, and whose output end is connected to the control end of the device to be protected.

[0064] Specifically, Figure 5 In the embodiment, the first switch circuit 411 is used to switch the switch state based on the first level signal and the second level signal, so that the absolute value of the voltage at the first input terminal REF1 of the second comparison circuit 412 is the first current value; if the second comparison circuit 412 determines that the absolute value of the output current R_LIMT is greater than the first current value, the second comparison circuit 412 controls the protected device to stop working.

[0065] Specifically, Figure 5 In the embodiment, the first switch circuit 411 includes: a first switch Q1, a first diode D1, a first resistor R18, a second resistor R19 and a third resistor R20, wherein the first switch Q1, whose control end is connected to the first end of the first resistor R18 and the first end of the second resistor R19, whose first end is connected to the second end of the second resistor R19 and the first input end of the second comparison circuit 412, and whose second end is connected to the first end of the third resistor R20; the first resistor R18, whose second end is connected to the anode of the first diode D1; the first diode D1, whose cathode is connected to the first input end of the second current threshold determination branch 42 and then inputs the first level signal or the second level signal; the third resistor R20, whose second end is connected to the first end of the second current threshold determination branch 42.

[0066] Specifically, Figure 5 When the cathode of the first diode D1 receives the first level signal, the first diode D1 is turned off and the first switch Q1 is turned off, so that the voltage of the first input terminal REF1 of the second comparison circuit 412 is 2.8125V, and the corresponding forward overcurrent protection point is 364A; when the cathode of the first diode D1 receives the second level signal, the first diode D1 is turned on and the first switch Q1 is turned on, so that the voltage of the first input terminal REF1 of the second comparison circuit 412 is 2.402V, and the corresponding forward overcurrent protection point is 250A.

[0067] In some optional embodiments, such as Figure 5 As shown, the second current threshold determination branch 42 includes: a second switch circuit 421 and a third comparison circuit 422, wherein the second switch circuit 421, whose control end is connected to the control end of the first switch circuit 411 and then inputs the first level signal or the second level signal, whose first end is connected to the first input end of the third comparison circuit 422, and whose second end is connected to the first power supply 3.3V and the first end of the third comparison circuit 422; the third comparison circuit 422, whose second input end is connected to the second input end of the second comparison circuit 412 and then inputs the output current R_LIMT, whose output end is connected to the control end of the device to be protected, and whose second end is connected to the second end of the first switch circuit 411.

[0068] Specifically, Figure 5 In the embodiment, the first switch circuit 411 is used to switch the switch state based on the first level signal and the second level signal, so that the absolute value of the voltage at the first input terminal REF2 of the third comparison circuit 422 is the second current value; if the third comparison circuit 422 determines that the absolute value of the output current R_LIMT is greater than the second current value, the third comparison circuit controls the protected device to stop working.

[0069] Optionally, Figure 5 In the embodiment, the second switch circuit 421 includes: a second switch Q2, a second diode D2, a fourth resistor R26, a fifth resistor R27 and a sixth resistor R28, wherein the second switch Q2, whose control end is connected to the first end of the fourth resistor R26 and the first end of the fifth resistor R27, whose first end is connected to the first end of the sixth resistor R28, and whose second end is connected to the second end of the fifth resistor R27 and the first end of the third comparison circuit 422; the fourth resistor R26, whose second end is connected to the anode of the second diode D2; the second diode D2, whose cathode is connected to the cathode of the first diode D1 and then inputs the first level signal or the second level signal; the sixth resistor R28, whose second end is connected to the first input end of the third comparison circuit 422.

[0070] Specifically, Figure 5When the cathode of the second diode D2 receives the first level signal, the second diode D2 is turned off and the second switch Q2 is turned off, so that the voltage of the first input terminal REF2 of the third comparison circuit 422 is 0.1875V, and the corresponding negative overcurrent protection point is -364A; when the cathode of the second diode D2 receives the second level signal, the second diode D2 is turned on and the second switch Q2 is turned on, so that the voltage of the first input terminal REF2 of the third comparison circuit 422 is 0.598V, and the corresponding negative overcurrent protection point is -250A.

[0071] Specifically, refer to Figure 1 and Figure 5 When the bus voltage BUS+_COM of the device to be protected is lower than the reference voltage REF0, the overcurrent point is ±360A, and when it is higher than the reference voltage REF0, the overcurrent point is ±250A. That is, when the bus voltage BUS+_COM is in the high voltage area, the overcurrent point is 110A lower than that in the low voltage area. When the bus voltage BUS+_COM is in the high voltage area, the stress on the devices of the device to be protected that need to be shut down due to overcurrent is greatly reduced.

[0072] This embodiment provides a power supply circuit, such as Figure 6 As shown, it includes: an inverter 5 and the overcurrent protection circuit of the above embodiments and any optional implementation manner thereof, wherein a voltage sampling circuit 1, whose input end collects the positive bus voltage BUS+ and the negative BUS- of the inverter 5 and then outputs the processed bus voltage BUS+_COM; a current sampling circuit 2, whose input end collects the output current of the inverter and then outputs the output current R_LIMT.

[0073] Figure 6 When the voltage threshold determination circuit 3 determines that the bus voltage BUS+_COM is less than the reference voltage REF0, the current threshold determination circuit 4 switches the switch state so that the absolute value of the overcurrent protection point in the current threshold determination circuit 4 is the first current value.

[0074] Figure 6 When the voltage threshold determination circuit 3 determines that the bus voltage BUS+_COM is greater than the reference voltage REF0, the current threshold determination circuit 4 switches the switch state so that the absolute value of the overcurrent protection point in the current threshold determination circuit 4 is the second current value.

[0075] Figure 6 In the embodiment, when the current threshold determination circuit 4 determines that the absolute value of the output current R_LIMT is greater than the first current value or the second current value, the current threshold determination circuit 4 controls the inverter 5 to block the wave.

[0076] Specifically, refer to Figure 6 and Figure 7 , the overcurrent protection process for the inverter 5 includes:

[0077] (1) Sample the BUS voltage of the inverter bus and compare it with the reference voltage.

[0078] (2) If the BUS voltage exceeds the reference voltage, the voltage threshold determination circuit outputs the comparison result BUS_OV_PRO as a low level, and the overcurrent reference voltages of the current threshold determination circuit are Ref1-1 and Ref2-1, which correspond to a lower overcurrent point.

[0079] (3) If the BUS voltage does not exceed the reference voltage, the voltage threshold determination circuit outputs the comparison result BUS_OV_PRO as a high level, and the overcurrent reference voltage of the current threshold determination circuit is Ref1-2 and Ref2-2, which corresponds to a higher overcurrent point.

[0080] (4) Compare the inverter current sampling signal with the overcurrent point.

[0081] (5) If the inverter current sampling signal exceeds the overcurrent point, the drive signal RINV_LIMT_D- or RINV_LIMT_D+ output by the current threshold judgment circuit is flipped, and the complex programmable logic device (CPLD) in the inverter controls the inverter to block the wave after receiving the signal.

[0082] (6) If the inverter current sampling signal does not exceed the overcurrent point, return to step (1).

[0083] It should be noted that the structure and control principle are consistent with the above embodiment and any optional implementation manner, and will not be repeated here.

[0084] The power supply circuit provided in this embodiment can adjust the size of the overcurrent protection point according to the bus voltage of the inverter. When the voltage threshold determination circuit determines that the bus voltage of the inverter is greater than the reference voltage, the bus of the inverter is in a high voltage state, and by switching the switch state of the current threshold determination circuit, the voltage division state in the current threshold determination circuit is made, so that the absolute value of the overcurrent point in the current threshold determination circuit is reduced, so that when the current threshold determination circuit determines that the inverter is overcurrent and needs to shut down the output for wave blocking, the output current of the inverter is in a lower state, thereby reducing the device stress and shutdown loss of the inverter, avoiding the heating of the components in the inverter caused by the large current, and increasing the service life of the inverter. At the same time, due to the reduction in heat generation, the volume of the inverter heat sink can be reduced, further reducing the cost of the whole machine.

[0085] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An overcurrent protection circuit, characterized in that: include: A voltage sampling circuit, a current sampling circuit, a voltage threshold determination circuit and a current threshold determination circuit, wherein: A voltage sampling circuit, whose input terminal is input with the bus voltage of the device to be protected, and whose output terminal is connected with the first input terminal of the voltage threshold determination circuit; A voltage threshold determination circuit, whose second input terminal inputs a reference voltage, whose output terminal is connected to the first input terminal of the current threshold determination circuit, and is used to compare the bus voltage with the reference voltage and output a comparison result; A current sampling circuit, whose input end is connected to the output end of the device to be protected, and whose output end is connected to the second input end of the current threshold determination circuit, and is used to collect the output current of the device to be protected; A current threshold determination circuit, whose output terminal is connected to the control terminal of the device to be protected, and which is used to switch the switch state according to the comparison result, so that when the bus voltage is greater than the reference voltage, the absolute value of the overcurrent protection point inside it is smaller than the absolute value of the overcurrent protection point inside it when the bus voltage is less than the reference voltage; When the current threshold determination circuit determines that the absolute value of the output current is greater than the absolute value of the overcurrent protection point, the current threshold determination circuit controls the device to be protected to stop working.

2. The overcurrent protection circuit according to claim 1, characterized in that: The voltage sampling circuit comprises: an input signal processing circuit and a first differential operational amplifier circuit, wherein: An input signal processing circuit, wherein the positive bus voltage of the device to be protected is input at the first input terminal, the negative bus voltage of the device to be protected is input at the second input terminal, the first output terminal is connected to the first input terminal of the first differential operational amplifier circuit, and the second output terminal is connected to the second input terminal of the first differential operational amplifier circuit, and the circuit is used to limit the magnitude of the current flowing from the bus into the first differential operational amplifier circuit; The first differential operational amplifier circuit has an output end connected to the first input end of the voltage threshold determination circuit and is used to amplify the voltage difference between the positive end and the negative end of the busbar and then output it.

3. The overcurrent protection circuit according to claim 1, characterized in that: The current sampling circuit includes: a current sensor and a second differential operational amplifier circuit, wherein: A current sensor, wherein the input end is connected to the output end of the device to be protected, the first output end is connected to the first input end of the second differential operational amplifier circuit, and the second output end is connected to the second input end of the second differential operational amplifier circuit, and the sampled current of the device to be protected is converted into a voltage signal and a reference signal and then input into the second differential operational amplifier circuit; The second differential operational amplifier circuit has an output end connected to the second input end of the current threshold determination circuit and is used to amplify the voltage difference between the voltage signal and the reference signal and output it as the output current of the device to be protected.

4. The overcurrent protection circuit according to claim 1, characterized in that: The voltage threshold determination circuit comprises: a first comparison circuit and a filter circuit, wherein: A first comparison circuit, wherein a first input terminal is connected to the first power supply, a second input terminal is input with the bus voltage, an output terminal is connected to the first terminal of the filter circuit, the comparison circuit obtains the reference voltage based on the voltage division of the first power supply, compares the bus voltage with the reference voltage, and outputs a comparison result; a filter circuit, a second end of which is connected to the first power supply, a third end of which is grounded, and a fourth end of which is connected to the first input end of the current threshold determination circuit, and is used to filter out interference signals in the comparison result; When the first comparison circuit determines that the bus voltage is less than the reference voltage, the first comparison circuit outputs a first level signal; When the first comparison circuit determines that the bus voltage is greater than the reference voltage, the first comparison circuit outputs a second level signal; The first level signal and the second level signal have different high and low states.

5. The overcurrent protection circuit according to claim 1, characterized in that: The current threshold determination circuit comprises: a first current threshold determination branch and a second current threshold determination branch, wherein: a first current threshold determination branch, wherein a first input end of the first current threshold determination branch is connected to the first input end of the second current threshold determination branch and then inputs a first level signal or a second level signal, a second input end of the first current threshold determination branch is connected to the second input end of the second current threshold determination branch and then inputs the output current, an output end of the first current threshold determination branch is connected to the output end of the second current threshold determination branch and the control end of the device to be protected, a first end of the first current threshold determination branch is connected to the first power supply, and a second end of the first current threshold determination branch is connected to the first end of the second current threshold determination branch; a second current threshold determination branch, a second end of which is connected to the first power supply; when the current threshold determination circuit receives the first level signal, the first current threshold determination branch and the second current threshold determination branch switch switch states, so that the absolute values ​​of the positive overcurrent protection point in the first current threshold determination branch and the negative overcurrent point in the second current threshold determination branch are both the first current value; When the current threshold determination circuit receives the second level signal, the first current threshold determination branch and the second current threshold determination branch switch the switch state so that the absolute values ​​of the positive overcurrent protection point in the first current threshold determination branch and the negative overcurrent point in the second current threshold determination branch are both the second current value; The first current value is greater than the second current value.

6. The overcurrent protection circuit according to claim 5, characterized in that: The first current threshold determination branch includes: a first switch circuit and a second comparison circuit, wherein: a first switch circuit, wherein a control end of the first switch circuit is connected to the first input end of the second current threshold determination branch and then inputs a first level signal or a second level signal, a first end of the first switch circuit is connected to the first input end of the second comparison circuit, and a second end of the first switch circuit is connected to the first end of the second current threshold determination branch, and the switch circuit is used to switch a switch state based on the first level signal and the second level signal, so that the absolute value of the voltage at the first input end of the second comparison circuit is the first current value; A second comparison circuit, a second input end of which is connected to the second input end of the second current threshold determination branch and then inputs the output current, and an output end of which is connected to the control end of the device to be protected; If the second comparison circuit determines that the absolute value of the output current is greater than the first current value, the second comparison circuit controls the device to be protected to stop working.

7. The overcurrent protection circuit according to claim 6, characterized in that: The first switch circuit includes: a first switch, a first diode, a first resistor, a second resistor and a third resistor, wherein: a first switch, whose control end is connected to the first end of the first resistor and the first end of the second resistor, whose first end is connected to the second end of the second resistor and the first input end of the second comparison circuit, and whose second end is connected to the first end of the third resistor; a first resistor, a second end of which is connected to the anode of the first diode; A first diode, a cathode of which is connected to the first input end of the second current threshold determination branch and inputs a first level signal or a second level signal; a third resistor, a second end of which is connected to the first end of the second current threshold determination branch; When the cathode of the first diode receives a first level signal, the first diode is turned off and the first switch is turned off; When the cathode of the first diode receives a second level signal, the first diode is turned on and the first switch is turned on.

8. The overcurrent protection circuit according to claim 7, characterized in that: The second current threshold determination branch includes: a second switch circuit and a third comparison circuit, wherein: a second switch circuit, a control end of which is connected to the control end of the first switch circuit and inputs a first level signal or a second level signal, a first end of which is connected to the first input end of the third comparison circuit, and a second end of which is connected to the first power supply and the first end of the third comparison circuit, and is used to switch a switch state based on the first level signal and the second level signal, so that the absolute value of the voltage at the first input end of the third comparison circuit is a second current value; a third comparison circuit, wherein a second input terminal of the third comparison circuit is connected to the second input terminal of the second comparison circuit and then inputs the output current, an output terminal of the third comparison circuit is connected to the control terminal of the device to be protected, and a second terminal of the third comparison circuit is connected to the second terminal of the first switch circuit; If the third comparison circuit determines that the absolute value of the output current is greater than the second current value, the third comparison circuit controls the device to be protected to stop working.

9. The overcurrent protection circuit according to claim 8, characterized in that: The second switch circuit includes: a second switch, a second diode, a fourth resistor, a fifth resistor and a sixth resistor, wherein: a second switch, a control end of which is connected to the first end of the fourth resistor and the first end of the fifth resistor, a first end of which is connected to the first end of the sixth resistor, and a second end of which is connected to the second end of the fifth resistor and the first end of the third comparison circuit; a fourth resistor, a second end of which is connected to the anode of the second diode; a second diode, a cathode of which is connected to the cathode of the first diode and inputs a first level signal or a second level signal; a sixth resistor, a second end of which is connected to the first input end of the third comparison circuit; When the cathode of the second diode receives a first level signal, the second diode is turned off and the second switch is turned off; When the cathode of the second diode receives a second level signal, the second diode is turned on and the second switch is turned on.

10. A power supply circuit, characterized in that: include: An inverter and an overcurrent protection circuit according to any one of claims 1 to 9, wherein: A voltage sampling circuit, whose input end collects the positive bus voltage and the negative bus voltage of the inverter and then outputs the processed bus voltage; A current sampling circuit, whose input end samples the current at the output end of the inverter and then outputs the output current; When the voltage threshold determination circuit determines that the bus voltage is less than the reference voltage, the current threshold determination circuit switches the switch state so that the absolute value of the overcurrent protection point in the current threshold determination circuit is the first current value; When the voltage threshold determination circuit determines that the bus voltage is greater than the reference voltage, the current threshold determination circuit switches the switch state so that the absolute value of the overcurrent protection point in the current threshold determination circuit is a second current value; When the current threshold determination circuit determines that the absolute value of the output current is greater than the first current value or the second current value, the current threshold determination circuit controls the inverter to block the wave.

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