Current limiting device

Abstract

The embodiment of the invention relates to the technical field of current limiting, in particular to a current limiting device which comprises a first transistor, a second transistor, a compensation element and a voltage balance circuit. A drain electrode of the first transistor and a drain electrode of the second transistor are connected with a power supply, a source electrode of the first transistor is connected with a load, a source electrode of the second transistor is connected with a first end of the compensation element, and a grid electrode of the first transistor is connected with a grid electrode of the second transistor. The voltage balancing circuit is connected between the second end of the compensation element and the source electrode of the first transistor. Therefore, the maximum current actually passing through the first transistor is the drain current corresponding to the drain-source voltage for converting the first transistor from the linear region to the saturation region under the action of the preset maximum gate voltage, and the power supply and the load which can normally work under the action of the maximum current are selected to be matched with the current limiting device for use. The situation that current passing through the first transistor is too large can be reduced, and the possibility that a power supply and a load are damaged is reduced.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of current limiting technology, and in particular, to a current limiting device. Background Art

[0002] Overcurrent Protection (OCP) technology protects the circuit by setting an appropriate current limit, which can effectively improve the situation where the circuit is damaged due to circuit overload.

[0003] A current limiting device is a device designed based on overcurrent protection technology. Current current limiting devices generally include a current limiting element and a current limiting adjustment circuit. When using the current limiting device, the current limiting element will be connected between the power supply and the grounded load so that a power-on circuit can be formed between the power supply, the current limiting element, the load and the ground. The current limiting adjustment circuit is connected to the current limiting element. The current limiting adjustment circuit is used to adjust the working state of the current limiting element when the current of the current limiting element is greater than the current limiting value so that the current passing through the current limiting element is less than or equal to the current limiting value.

[0004] During the operation of the current limiting device, the current passing through the current limiting device may still exceed the current limiting value. Even when the set current limiting value is too large, even if it does not exceed the current limiting value, the current passing through the current limiting device may be large, so as to damage the power supply or load. In order to avoid damage to the power supply and load as much as possible, transistors are usually used as current limiting devices. Correspondingly, the current passing through the current limiting device is the drain current of the transistor. Ideally, the transistor is in a linear region when the drain-source voltage is small, and the drain current of the transistor in the linear region is proportional to the drain-source voltage. In addition, the transistor is in a saturation region when the drain-source voltage is large. The drain current of the transistor in the zone does not change with the change of the drain-source voltage. Therefore, in an ideal case, based on the current limiting device being a transistor, if the gate voltage of the current limiting device is constant, even if the load change causes the drain-source voltage of the current limiting device to change, the current passing through the current limiting device will not exceed the drain current corresponding to the drain-source voltage that causes the current limiting device to change from the linear zone to the saturation zone. Furthermore, the maximum current passing through the current limiting device is the drain current corresponding to the drain-source voltage that causes the current limiting device to change from the linear zone to the saturation zone under the action of a preset maximum gate voltage. Therefore, a power supply and a load that can work normally under the action of the maximum current can be selected for use in conjunction with the current limiting device.

[0005] However, during the actual use of transistors, if the transistor is in the saturation region and its drain-source voltage is low, its drain current will still increase significantly with the increase of the drain-source voltage, so that the above-mentioned maximum current is not the actual maximum current passing through the current limiting device. As a result, using a transistor as a current limiting device will still result in excessive current passing through the current limiting device, which can easily cause damage to the power supply or load. Summary of the invention

[0006] In view of this, an embodiment of the present application provides a current limiting device to at least partially solve the above-mentioned problem.

[0007] The current limiting device provided in an embodiment of the present application includes a first transistor, a second transistor, a compensation element and a voltage balancing circuit; the first transistor and the second transistor have the same structure, the drain of the first transistor and the drain of the second transistor are both used to connect to a power supply, the source of the first transistor is used to connect to a load, the source of the second transistor is connected to the first end of the compensation element, and the gate of the first transistor is connected to the gate of the second transistor; the voltage balancing circuit is connected between the second end of the compensation element and the source of the first transistor.

[0008] In a possible implementation, the compensation element includes a compensation transistor; a drain of the compensation transistor is connected to a source of the second transistor, a source of the compensation transistor is connected to the voltage balancing circuit, and a gate of the compensation transistor is connected to a voltage supply component.

[0009] In a possible implementation manner, the compensation transistor operates in a linear region.

[0010] In one possible implementation, the voltage supply element includes a charge pump; the charge pump is connected between the source of the first transistor and the gate of the compensation transistor, or between the source of the compensation transistor and the gate of the compensation transistor, and is used to pressurize the voltage of the source of the first transistor and input it to the gate of the compensation transistor, so that the compensation transistor operates in a linear region.

[0011] In one possible implementation, the charge pump is used to pressurize the voltage of the source of the first transistor by 5 to 10 volts and then input it to the gate of the compensation transistor, or to pressurize the voltage of the source of the compensation transistor by 5 to 10 volts and then input it to the gate of the compensation transistor, so that the compensation transistor operates in a linear region.

[0012] In a possible implementation manner, the compensation transistor has the same structure as the first transistor and the second transistor.

[0013] In a possible implementation manner, the compensation transistor, the first transistor, and the second transistor are all N-channel transistors.

[0014] In one possible implementation, the voltage balancing circuit includes a first amplifier and a balancing transistor, the balancing transistor being a P-channel transistor; two input terminals of the first amplifier are respectively connected to the source of the first transistor and the source of the compensation transistor, and the output terminal of the first amplifier is connected to the gate of the balancing transistor; the source of the balancing transistor is connected to the source of the compensation transistor, and the drain of the balancing transistor is connected to the voltage regulation circuit.

[0015] In one possible implementation, the current limiting device also includes a voltage regulating circuit; the voltage regulating circuit is connected to the gate of the second transistor, and is used to adjust the gate voltages of the first transistor and the second transistor when the drain current of the second transistor is greater than a first current threshold, so that the drain current of the second transistor is less than or equal to the first current threshold, and the drain current of the first transistor is less than or equal to the second current threshold, and the drain of the balancing transistor is connected to the voltage regulating circuit.

[0016] In a possible implementation, the voltage regulation circuit includes a resistor, a second amplifier and a gate voltage regulation unit; one end of the resistor is connected to the drain of the balancing transistor, and the other end of the resistor is grounded; the first input end of the second amplifier is connected between the resistor and the drain of the balancing transistor, the input voltage of the second input end of the second amplifier is a voltage threshold, and the voltage threshold is the product of the resistance value of the resistor and the first current threshold; one end of the gate voltage regulation unit is connected to the output end of the second amplifier, and the other end of the gate voltage regulation unit is connected to the gate of the second transistor.

[0017] In a possible implementation manner, a gate width of the first transistor is greater than a gate width of the second transistor.

[0018] According to the current limiting device provided in the embodiment of the present application, since the current limiting device includes a compensation element, the voltage of the source of the first transistor in the current limiting device is less than the voltage of the source of the second transistor. Specifically, if the gate-source voltage of the first transistor is VGS1, the drain-source voltage of the first transistor is VDS1, the gate-source voltage of the second transistor is VGS2, the drain-source voltage of the second transistor is VDS2, and the voltage difference between the first end and the second end of the compensation element is V0, then VGS1=VGS2+V0, VDS1=VDS2+V0 can be obtained, and then the change of VGS1 relative to VGS2 and the change of VDS1 relative to VDS2 are relatively synchronized, so that the working state switching of the first transistor and the second transistor is relatively synchronized.

[0019] When the first transistor and the second transistor are in the linear region, VDS2 is small, so that the change of VDS1 relative to VDS2 is more obvious, and the influence of V0 on VDS1 cannot be ignored. Therefore, when the voltage of the gate of the first transistor is constant, compared with the solution without compensation elements, the drain-source voltage of the first transistor in the embodiment of the present application is larger when the first transistor is transformed from the linear region to the saturation region, and the drain current corresponding to the drain-source voltage is larger. Therefore, the compensation element in the current limiting device of the embodiment of the present application can extend the linear region of the first transistor. When the first transistor and the second transistor are in the saturation region and the drain-source voltages of the two are large, VDS2 is large so that the change of VDS1 relative to VDS2 is not obvious, and the influence of V0 on VDS1 can be ignored. Therefore, when the voltage of the gate of the first transistor is constant, compared with the solution without compensation elements, the drain current of the first transistor in the saturation region in the embodiment of the present application is almost unchanged.

[0020] Based on this, when the gate voltage of the first transistor is constant, even if the load changes and causes the drain-source voltage of the first transistor to change, the current passing through the first transistor (i.e., the drain current of the first transistor) will hardly exceed the drain current corresponding to the drain-source voltage that causes the first transistor to transition from the linear region to the saturation region. Furthermore, the maximum current actually passing through the first transistor is the drain current corresponding to the drain-source voltage that causes the first transistor to transition from the linear region to the saturation region under the action of a preset maximum gate voltage. Selecting a power supply and a load that can operate normally under the action of the maximum current in conjunction with a current limiting device can reduce the situation where the current passing through the first transistor is too large, thereby reducing the possibility of damage to the power supply and the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0022] Figure 1 is a schematic diagram of a current limiting device according to an embodiment of the present application;

[0023] Figure 2 is a schematic diagram of a current limiting device according to another embodiment of the present application;

[0024] Figure 3 is a performance schematic diagram of a first transistor in a related technology of the present application;

[0025] Figure 4 is a performance diagram of a first transistor in one embodiment of the present application;

[0026] Figure 5 It is a schematic diagram comparing the performance of a first transistor in an embodiment of the present application and another related technology.

[0027] Description of reference numerals:

[0028] 1. Voltage balancing circuit; 2. Voltage regulation circuit. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the embodiments of the present application should fall within the scope of protection of the embodiments of the present application.

[0030] As mentioned in the background technology, current current limiting devices generally include a current limiting element and a current limiting adjustment circuit. When using the current limiting device, the current limiting element will be connected between the power supply and the grounded load so that a power-on circuit can be formed between the power supply, the current limiting element, the load and the ground. The current limiting adjustment circuit is connected to the current limiting element. The current limiting adjustment circuit is used to adjust the working state of the current limiting element when the current of the current limiting element is greater than the current limiting value so that the current passing through the current limiting element is less than or equal to the current limiting value.

[0031] During the operation of the current limiting device, the current passing through the current limiting device may still exceed the current limiting value. Even when the set current limiting value is too large, even if it does not exceed the current limiting value, the current passing through the current limiting device may be large, so as to damage the power supply or load. In order to avoid damage to the power supply and load as much as possible, transistors are usually used as current limiting devices. Correspondingly, the current passing through the current limiting device is the drain current of the transistor. Ideally, the transistor is in a linear region when the drain-source voltage is small, and the drain current of the transistor in the linear region is proportional to the drain-source voltage. In addition, the transistor is in a saturation region when the drain-source voltage is large. The drain current of the transistor in the zone does not change with the change of the drain-source voltage. Therefore, in an ideal case, based on the current limiting device being a transistor, if the gate voltage of the current limiting device is constant, even if the load change causes the drain-source voltage of the current limiting device to change, the current passing through the current limiting device will not exceed the drain current corresponding to the drain-source voltage that causes the current limiting device to change from the linear zone to the saturation zone. Furthermore, the maximum current passing through the current limiting device is the drain current corresponding to the drain-source voltage that causes the current limiting device to change from the linear zone to the saturation zone under the action of a preset maximum gate voltage. Therefore, a power supply and a load that can work normally under the action of the maximum current can be selected for use in conjunction with the current limiting device.

[0032] However, during the actual use of transistors, if the transistor is in the saturation region and its drain-source voltage is low, its drain current will still increase significantly with the increase of the drain-source voltage, so that the above-mentioned maximum current is not the actual maximum current passing through the current limiting device. As a result, using a transistor as a current limiting device will still result in excessive current passing through the current limiting device, which can easily cause damage to the power supply or load.

[0033] In view of the above problems, an embodiment of the present application provides a current limiting device, which is described in detail below with reference to the accompanying drawings.

[0034] Figure 1 Schematic diagram of a current limiting device according to an embodiment of the present application. Figure 1 As shown, the current limiting device provided in the embodiment of the present application includes: a first transistor Mpass, a second transistor Msense, a compensation element and a voltage balancing circuit 1.

[0035] The first transistor Mpass and the second transistor Msense have the same structure, and the sizes of the first transistor Mpass and the second transistor Msense may be the same or different. The drain of the first transistor Mpass and the drain of the second transistor Msense are used to be connected to the same power supply VIN, and the source of the first transistor Mpass is used to connect to the load Rout. For example, the source of the first transistor Mpass is connected to the output port OUT, and the load Rout is used to be connected to the output port OUT. The load Rout is a grounded load Rout. The source of the second transistor Msense is connected to the first end of the compensation element, and the resistance between the first end and the second end of the compensation element is greater than 0, so that the source voltage of the first transistor Mpass is less than the source voltage of the second transistor Msense. The gate of the first transistor Mpass is connected to the gate of the second transistor Msense, and the compensation element may be a resistor or a transistor, etc.

[0036] The voltage balancing circuit 1 is connected between the second end of the compensation element and the source of the first transistor Mpass, and is used to control the voltage of the source of the first transistor Mpass to be equal to the voltage of the second end of the compensation element.

[0037] In a specific embodiment, Figure 1 and Figure 2As shown, a voltage regulating circuit is connected between a connection node between the gate of the first transistor Mpass and the gate of the second transistor Msense and the voltage balancing circuit 1, and the voltage regulating circuit is used to adjust the voltage of the gate of the first transistor Mpass and the gate of the second transistor Msense. For example, the gate of the first transistor Mpass and the gate of the second transistor Msense are both connected to the first port a1, the voltage balancing circuit 1 is connected to the second port a2, and a voltage regulating circuit 2 is connected between the first port a1 and the second port a2. The voltage regulating circuit 2 is connected to the gate of the second transistor Msense and is used to adjust the gate voltage of the first transistor Mpass and the second transistor Msense when the drain current of the second transistor Msense is greater than the first current threshold, so that the drain current of the second transistor Msense is less than or equal to the first current threshold, and the drain current of the first transistor Mpass is less than or equal to the second current threshold. The first current threshold is preset according to the actual current limiting situation, and the embodiment of the present application is not limited to this. The second current threshold changes with the first current threshold, and the second current threshold is the product of the current proportional factor and the first current threshold, wherein the specific determination method of the current proportional factor is as follows:

[0038] Under ideal circumstances, the voltage of the drain of the first transistor Mpass is equal to the voltage of the drain of the second transistor Msense, and the voltage of the source of the first transistor Mpass is equal to the voltage of the source of the second transistor Msense, and the voltage of the gate of the first transistor Mpass is equal to the voltage of the gate of the second transistor Msense. Then, the ratio of the drain current of the first transistor Mpass to the drain current of the second transistor Msense is fixed, and this ratio is the current proportional factor. Furthermore, based on the current proportional factor, the drain current of the first transistor Mpass can be determined by the drain current of the second transistor Msense.

[0039] In the embodiment of the present application, since the drain of the first transistor Mpass and the drain of the second transistor Msense are connected to the same power supply VIN, the voltage of the drain of the first transistor Mpass is equal to the voltage of the drain of the second transistor Msense, and since the gate of the first transistor Mpass is connected to the gate of the second transistor Msense, the voltage of the gate of the first transistor Mpass is equal to the voltage of the gate of the second transistor Msense, and since the compensation element is connected to the source of the second transistor Msense, and the voltage balancing circuit 1 is connected between the source of the first transistor Mpass and the compensation element, the voltage of the source of the first transistor Mpass is actually smaller than the voltage of the source of the second transistor Msense. Based on this, due to the difference between the voltage of the source of the first transistor Mpass and the voltage of the source of the second transistor Msense, the actual value of the current proportional factor deviates from the theoretical value. To address this problem, the deviation can be reduced by selecting a compensation element with a smaller resistance, etc., so that the deviation can be ignored. The theoretical value of the current proportional factor can also be adjusted according to the difference between the voltage of the source of the first transistor Mpass and the voltage of the source of the second transistor Msense, so that the theoretical value of the current proportional factor is closer to the actual value. The embodiments of the present application are not limited to this.

[0040] It should be noted that during the actual operation of the current limiting device in the embodiment of the present application, specifically in the process of detecting the drain current of the first transistor Mpass through the second transistor Msense in the current limiting device, there may be a situation where the current proportional factor changes slightly due to changes in the working states of the first transistor Mpass and the second transistor Msense, and this slight change can be ignored.

[0041] During the operation of the current limiting device, when the drain current of the second transistor Msense is too large, the drain current of the second transistor Msense can be adjusted to not exceed the first current threshold, thereby achieving the purpose of limiting the drain current of the first transistor Mpass when the drain current of the first transistor Mpass is too large.

[0042] In the embodiment of the present application, due to the setting of the compensation element, the voltage of the source of the first transistor Mpass in the current limiting device is less than the voltage of the source of the second transistor Msense. Specifically, if the gate-source voltage of the first transistor Mpass is VGS1, the drain-source voltage of the first transistor Mpass is VDS1, the gate-source voltage of the second transistor Msense is VGS2, the drain-source voltage of the second transistor Msense is VDS2, and the voltage difference between the first end and the second end of the compensation element is V0, then VGS1=VGS2+V0, VDS1=VDS2+V0 can be obtained, and then the change of VGS1 relative to VGS2 and the change of VDS1 relative to VDS2 are relatively synchronized, so that the working state switching of the first transistor Mpass and the second transistor Msense is relatively synchronized.

[0043] [AW20230154ICN1][HS2410208CCN]

[0044] When the first transistor Mpass and the second transistor Msense are in the linear region, VDS2 is small, so that the change of VDS1 relative to VDS2 is more obvious, and the influence of V0 on VDS1 cannot be ignored. Therefore, when the voltage of the gate of the first transistor Mpass is constant, compared with the scheme without a compensation element (that is, the compensation element is deleted in the current limiting device of the embodiment of the present application, and the voltage balancing circuit 1 is connected between the source of the first transistor Mpass and the source of the second transistor Msense), the drain-source voltage of the first transistor Mpass that is transformed from the linear region to the saturation region is larger in the embodiment of the present application, and the drain current corresponding to the drain-source voltage is larger. Therefore, the compensation element in the current limiting device of the embodiment of the present application can extend the linear region of the first transistor Mpass.

[0045] When the first transistor Mpass and the second transistor Msense are in the saturation region and their drain-source voltages are large, VDS2 is large so that the change of VDS1 relative to VDS2 is not obvious, and the influence of V0 on VDS1 can be ignored. Therefore, when the gate voltage of the first transistor Mpass is constant, compared with the solution without a compensation element, the drain current of the first transistor Mpass in the saturation region in the embodiment of the present application is almost unchanged.

[0046] Exemplarily, when the gate voltage of the first transistor Mpass is constant, for a solution without a compensation element, a schematic diagram of the change of the drain current of the first transistor Mpass with its drain-source voltage is as follows: Figure 3 As shown, for the current limiting device of the embodiment of the present application, a schematic diagram of the change of the drain current of the first transistor Mpass with its drain-source voltage is shown in FIG. Figure 4 shown.

[0047] Based on this, when the gate voltage of the first transistor Mpass is constant, even if the load Rout changes and causes the drain-source voltage of the first transistor Mpass to change, the current passing through the first transistor Mpass (i.e., the drain current of the first transistor Mpass) will hardly exceed the drain current corresponding to the drain-source voltage that causes the first transistor Mpass to change from the linear region to the saturation region (e.g. Figure 4 The maximum current actually passing through the first transistor Mpass is the drain current corresponding to the drain-source voltage that causes the first transistor Mpass to transition from a linear region to a saturation region under the action of a preset maximum gate voltage. The power supply VIN and the load Rout that can work normally under the action of the maximum current are selected for use in conjunction with the current limiting device, which can reduce the situation where the current passing through the first transistor Mpass is too large, thereby reducing the possibility of damage to the power supply VIN and the load Rout.

[0048] In addition, the compensation element in the current limiting device of the embodiment of the present application can extend the linear region of the first transistor Mpass, and then the saturation region of the first transistor Mpass can be compressed, so that the change of the drain current of the first transistor Mpass with the drain-source voltage is improved, thereby optimizing the current limiting effect of the current limiting device.

[0049] In one possible implementation, Figure 2 As shown, the compensation element comprises a compensation transistor Mcomp, a drain of the compensation transistor Mcomp is connected to the source of the second transistor Msense, a source of the compensation transistor Mcomp is connected to the voltage balancing circuit 1, and a gate of the compensation transistor Mcomp is connected to a voltage supply.

[0050] In the embodiment of the present application, the compensation element uses a compensation transistor Mcomp so that the element types of the first transistor Mpass, the second transistor Msense and the compensation transistor Mcomp are the same, thereby reducing the influence of the compensation transistor Mcomp on the current relationship between the first transistor Mpass and the second transistor Msense, reducing the difference between the theoretical value and the actual value of the current proportional factor, and improving the current limiting accuracy of the current limiting device.

[0051] In a possible implementation, the compensation transistor Mcomp operates in a linear region, and the compensation transistor Mcomp can be controlled to operate in the linear region by controlling a gate voltage provided to the compensation transistor Mcomp by a control voltage supply component.

[0052] In the embodiment of the present application, the resistance value of the compensation transistor Mcomp operating in the linear region is relatively stable, so that the drain-source voltage of the compensation transistor Mcomp is positively correlated with the drain current of the compensation transistor Mcomp, and then the drain-source voltage of the compensation transistor Mcomp is positively correlated with the drain current of the second transistor Msense, which can avoid as much as possible the situation where the drain current of the second transistor Msense is small and the drain-source voltage of the compensation transistor Mcomp is large, so as to reduce the possibility that when the first transistor Mpass and the second transistor Msense are in the saturation region and the drain-source voltages of the two are large, the change of VDS1 relative to VDS2 is still relatively obvious, thereby reducing the possibility that the current passing through the first transistor Mpass exceeds the drain current of the first transistor Mpass when it changes from the linear region to the saturation region when the gate voltage remains unchanged, and further reducing the possibility of damage to the power supply VIN and the load Rout.

[0053] In one possible implementation, Figure 2 As shown, the voltage supply unit includes a charge pump CP, and the charge pump CP can be connected in any of the following two specific connection modes: Figure 2 The first specific connection mode is shown in the figure), in the first specific connection mode, the charge pump CP is connected between the source of the first transistor Mpass and the gate of the compensation transistor Mcomp, that is, the input end of the charge pump CP is connected to the source of the first transistor Mpass, and the output end of the charge pump CP is connected to the gate of the compensation transistor Mcomp. In the second specific connection mode, the charge pump CP is connected between the source of the compensation transistor Mcomp and the gate of the compensation transistor Mcomp, that is, the input end of the charge pump CP is connected to the source of the compensation transistor Mcomp, and the output end of the charge pump CP is connected to the gate of the compensation transistor Mcomp. Based on any of the above specific connection modes adopted by the charge pump CP, the charge pump CP is used to pressurize the voltage of the source of the first transistor Mpass and input it to the gate of the compensation transistor Mcomp, so that the compensation transistor Mcomp operates in the linear region.

[0054] In the embodiment of the present application, by providing a charge pump CP between the source of the first transistor Mpass and the gate of the compensation transistor Mcomp, or between the source of the compensation transistor Mcomp and the gate of the compensation transistor Mcomp, the voltage of the compensation transistor Mcomp can be changed as the voltage of the source of the first transistor Mpass changes. When the load Rout changes, causing the voltage of the source of the first transistor Mpass to increase, and thus causing the voltage of the source of the second transistor Msense to increase, the voltage of the gate of the compensation transistor Mcomp will also increase, so that the gate-source voltage of the compensation transistor Mcomp is still much larger than the drain-source voltage, and the compensation transistor Mcomp can be operated more stably in the linear region.

[0055] In one possible implementation, the charge pump CP is used to pressurize the voltage of the source of the first transistor Mpass by 5 to 10 volts and then input it to the gate of the compensation transistor Mcomp, or to pressurize the voltage of the source of the compensation transistor Mcomp by 5 to 10 volts and then input it to the gate of the compensation transistor Mcomp, so that the compensation transistor Mcomp operates in the linear region.

[0056] In a specific embodiment, when the charge pump CP is connected between the source of the first transistor Mpass and the gate of the compensation transistor Mcomp, the charge pump CP is used to increase the voltage of the source of the first transistor Mpass by 5 to 10 volts and then input it to the gate of the compensation transistor Mcomp.

[0057] In another specific embodiment, the charge pump CP is connected between the source of the first transistor Mpass and the gate of the compensation transistor Mcomp, and the charge pump CP is used to increase the voltage of the source of the compensation transistor Mcomp by 5 to 10 volts and then input it to the gate of the compensation transistor Mcomp.

[0058] In the embodiment of the present application, by setting the voltage value of the charge pump CP to 5 to 10 volts, the gate voltage of the compensation transistor Mcomp can be made 5 to 10 volts higher than the source voltage of the first transistor Mpass, or the gate voltage of the compensation transistor Mcomp can be made 5 to 10 volts higher than the source voltage of the compensation transistor Mcomp. Therefore, not only can the gate-source voltage of the compensation transistor Mcomp be made much larger than the drain-source voltage so as to operate in the linear region, but also the situation in which the gate voltage of the compensation transistor Mcomp is too large and affects the normal operation of the compensation transistor Mcomp can be reduced.

[0059] [AW20230154ICN1][HS2410208CCN]

[0060] In one possible implementation, the compensation transistor Mcomp has the same structure as the first transistor Mpass and the second transistor Msense, so that the first transistor Mpass, the second transistor Msense and the compensation transistor Mcomp are more consistent in properties such as withstand voltage, thereby reducing the influence of the compensation transistor Mcomp on the current relationship between the first transistor Mpass and the second transistor Msense, reducing the difference between the theoretical value and the actual value of the current proportional factor, and improving the current limiting accuracy of the current limiting device.

[0061] In a possible implementation manner, the compensation transistor Mcomp, the first transistor Mpass, and the second transistor Msense are all N-channel transistors.

[0062] In one possible implementation, Figure 2 As shown, the voltage balancing circuit 1 includes a first amplifier Opam1 and a balancing transistor Mreg, and the balancing transistor Mreg is a P-channel transistor; the two input terminals of the first amplifier Opam1 are respectively connected to the source of the first transistor Mpass and the source of the compensation transistor Mcomp, and the output terminal of the first amplifier Opam1 is connected to the gate of the balancing transistor Mreg; the source of the balancing transistor Mreg is connected to the source of the compensation transistor Mcomp, and the drain of the balancing transistor Mreg is connected to the voltage regulating circuit 2.

[0063] In an embodiment of the present application, the first amplifier Opam1 can compare the voltage of the source of the first transistor Mpass and the voltage of the source of the compensation transistor Mcomp. If there is a difference, the first amplifier Opam1 adjusts the voltage of the source of the compensation transistor Mcomp by outputting a signal to the gate of the balancing transistor Mreg until the voltage of the source of the first transistor Mpass is equal to the voltage of the source of the compensation transistor Mcomp, so as to keep the voltages of the sources of the first transistor Mpass and the compensation transistor Mcomp as equal as possible.

[0064] In one possible implementation, Figure 2 As shown, the current limiting device also includes a voltage regulating circuit 2; the voltage regulating circuit 2 is connected to the gate of the second transistor Msense, and is used to adjust the gate voltages of the first transistor Mpass and the second transistor Msense when the drain current of the second transistor Msense is greater than the first current threshold, so that the drain current of the second transistor Msense is less than or equal to the first current threshold, and the drain current of the first transistor Mpass is less than or equal to the second current threshold, and the drain of the balancing transistor Mreg is connected to the voltage regulating circuit 2.

[0065] The voltage regulating circuit 2 has been partially introduced above, and will not be described in detail in the embodiment of the present application.

[0066] In one possible implementation, Figure 2 As shown, the voltage regulating circuit 2 includes a resistor r, a second amplifier Opam2 and a gate voltage regulating unit Q; one end of the resistor r is connected to the drain of the balancing transistor Mreg, and the other end of the resistor r is grounded; the first input end of the second amplifier Opam2 is connected between the resistor r and the drain of the balancing transistor Mreg, and the input voltage of the second input end of the second amplifier Opam2 is a voltage threshold v, which is the product of the resistance value of the resistor r and the first current threshold; one end of the gate voltage regulating unit Q is connected to the output end of the second amplifier Opam2, and the other end of the gate voltage regulating unit Q is connected to the gate of the second transistor Msense.

[0067] In an embodiment of the present application, the second amplifier Opam2 can compare the voltage of the non-grounded end of the resistor r (i.e., the end point where the resistor r is connected to the drain of the balancing transistor Mreg) with the voltage threshold v. If the voltage of the non-grounded end exceeds the voltage threshold v, it means that the drain current of the second transistor Msense exceeds the first current threshold. The amplifier will output a control signal to the gate voltage adjustment unit Q. The control signal is used to control the gate voltage adjustment unit Q to adjust the voltages of the gates of the first transistor Mpass and the second transistor Msense until the voltage of the non-grounded end does not exceed the voltage threshold v, so that the drain current of the second transistor Msense does not exceed the first current threshold, and then the drain current of the first transistor Mpass does not exceed the second current threshold, thereby realizing the current limiting function of the current limiting device.

[0068] Optionally, the gate voltage regulating unit Q may include a target charge pump. Exemplarily, the target charge pump is connected between the first port a1 and the second amplifier Opam2. After the voltage at the non-grounded end of the resistor r exceeds the voltage threshold v, and the gate voltage regulating unit Q receives a control signal, the control signal can control the target charge pump so that the voltages at the gates of the first transistor Mpass and the second transistor Msense are adjusted so that the voltages at the non-grounded end of the resistor r do not exceed the voltage threshold v, thereby making the drain current of the second transistor Msense not exceed the first current threshold, and also making the drain current of the first transistor Mpass not exceed the second current threshold.

[0069] In a possible implementation, the gate width of the first transistor Mpass is greater than the gate width of the second transistor Msense, so that the current proportionality factor is greater than 1, and the drain current of the second transistor Msense is smaller than the drain current of the first transistor Mpass, thereby realizing the detection of large current by small current and saving energy.

[0070] In addition, compared with the related art that the drain of the second transistor Msense is connected with a compensation element, the embodiment of the present application is to connect the compensation element to the source of the second transistor Msense, such as Figure 5 As shown, RES1 is used to indicate how the drain current of the first transistor Mpass changes with the drain-source voltage under the action of the first gate voltage in the related art, NLDMOS1 is used to indicate how the drain current of the first transistor Mpass changes with the drain-source voltage under the action of the first gate voltage in the embodiment of the present application, RES2 is used to indicate how the drain current of the first transistor Mpass changes with the drain-source voltage under the action of the second gate voltage in the related art, NLDMOS2 is used to indicate how the drain current of the first transistor Mpass changes with the drain-source voltage under the action of the first gate voltage in the embodiment of the present application, and the first gate voltage is greater than the second gate voltage.

[0071] Therefore, compared with the related technology, the scheme of connecting the compensation element to the source of the second transistor Msense in the embodiment of the present application can make the difference between the maximum and minimum values ​​of the drain current when the first transistor Mpass operates in the saturation region smaller, that is, the current consistency of the first transistor Mpass when operating in the saturation region is higher, thereby improving the working quality of the first transistor Mpass, and thereby making the current limiting accuracy of the current limiting device higher.

[0072] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the existence of other identical factors in the process, method, article or device including the elements.

[0073] Not all steps and modules in the above-mentioned processes and system structure diagrams are necessary, and some steps or modules can be ignored according to actual needs. The execution order of each step is not fixed and can be adjusted as needed. The system structure described in the above-mentioned embodiments can be a physical structure or a logical structure, that is, some modules may be implemented by the same physical entity, or some modules may be implemented by multiple physical entities, or some components in multiple independent devices may be implemented together.

[0074] In the above embodiments, the hardware module can be implemented mechanically or electrically. For example, a hardware module can include permanent dedicated circuits or logic (such as a dedicated processor, FPGA or ASIC) to complete the corresponding operation. The hardware module can also include programmable logic or circuits (such as a general-purpose processor or other programmable processor), which can be temporarily set by software to complete the corresponding operation. The specific implementation method (mechanical method, or dedicated permanent circuit, or temporary

[0075] [AW20230154ICN1][HS2410208CCN] circuit settings) can be determined based on cost and time considerations.

Claims

1. A current limiting device, characterized in that: comprising a first transistor, a second transistor, a compensation element and a voltage balancing circuit; The first transistor and the second transistor have the same structure, the drain of the first transistor and the drain of the second transistor are both used to connect to a power supply, the source of the first transistor is used to connect to a load, the source of the second transistor is connected to the first end of the compensation element, and the gate of the first transistor is connected to the gate of the second transistor; The voltage balancing circuit is connected between the second end of the compensation element and the source of the first transistor.

2. The device according to claim 1, characterized in that The compensation element includes a compensation transistor; The drain of the compensation transistor is connected to the source of the second transistor, the source of the compensation transistor is connected to the voltage balancing circuit, and the gate of the compensation transistor is connected to a voltage supplying member.

3. The device according to claim 2, characterized in that The compensation transistor operates in a linear region.

4. The device according to claim 3, characterized in that The voltage supply element includes a charge pump; The charge pump is connected between the source of the first transistor and the gate of the compensation transistor, or between the source of the compensation transistor and the gate of the compensation transistor, and is used to pressurize the voltage of the source of the first transistor and input it to the gate of the compensation transistor, so that the compensation transistor operates in a linear region.

5. The device according to claim 4, characterized in that The charge pump is used to pressurize the voltage of the source of the first transistor by 5 to 10 volts and then input it to the gate of the compensation transistor, or to pressurize the voltage of the source of the compensation transistor by 5 to 10 volts and then input it to the gate of the compensation transistor, so that the compensation transistor operates in a linear region.

6. The device according to claim 2, characterized in that The compensation transistor has the same structure as the first transistor and the second transistor.

7. The device according to claim 2, characterized in that The compensation transistor, the first transistor and the second transistor are all N-channel transistors.

8. The device according to claim 2, characterized in that The voltage balancing circuit includes a first amplifier and a balancing transistor, wherein the balancing transistor is a P-channel transistor; Two input terminals of the first amplifier are connected to the source of the first transistor and the source of the compensation transistor respectively, and an output terminal of the first amplifier is connected to the gate of the balancing transistor; The source of the balancing transistor is connected to the source of the compensating transistor.

9. The device according to claim 8, characterized in that The current limiting device also includes a voltage regulating circuit; The voltage regulating circuit is connected to the gate of the second transistor and is used to adjust the gate voltages of the first transistor and the second transistor when the drain current of the second transistor is greater than a first current threshold, so that the drain current of the second transistor is less than or equal to the first current threshold, and the drain current of the first transistor is less than or equal to the second current threshold, and the drain of the balancing transistor is connected to the voltage regulating circuit.

10. The device according to claim 9, characterized in that The voltage regulating circuit comprises a resistor, a second amplifier and a gate voltage regulating unit; One end of the resistor is connected to the drain of the balancing transistor, and the other end of the resistor is grounded; The first input terminal of the second amplifier is connected between the resistor and the drain of the balancing transistor, the input voltage of the second input terminal of the second amplifier is a voltage threshold, and the voltage threshold is the product of the resistance value of the resistor and the first current threshold; One end of the gate voltage regulating unit is connected to the output end of the second amplifier, and the other end of the gate voltage regulating unit is connected to the gate of the second transistor.

11. The device according to claim 1, characterized in that A gate width of the first transistor is greater than a gate width of the second transistor.

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