A current detection method and system for MOS transistors

Abstract

The present invention discloses a current detection method and system for a MOS transistor. The method includes the following steps: after voltage division sampling of the voltages of the D and S poles of the MOS transistor, perform voltage follower for the divided voltages; differentially amplify the voltage after following and convert it into a corresponding current value; based on the converted current value, determine whether the MOS transistor is overcurrent or short-circuited, and according to the determination result, perform protection control on the MOS transistor; The system includes: a voltage division sampling module for performing voltage division sampling on the voltages of the D and S poles of the MOS transistor and performing voltage follower for the divided voltages; an AD conversion module for differentially amplifying the voltage after following and converting it into a current value; a detection module for performing overcurrent or short-circuit protection control on the MOS transistor based on the converted current value; The current detection method mentioned in the present invention is particularly suitable for current detection applied in overcurrent and short-circuit protection, providing a new technical idea for the current detection of MOS transistors.

Description

Technical Field

[0001] The present invention relates to the technical field of MOS transistor current detection, and more particularly, to a current detection method and system for MOS transistors. Background Art

[0002] Currently, for various lighting controls in automobiles, controls of various electrical appliances, and protection of various current outputs in the power control box, the commonly adopted solutions are generally intelligent MOS transistor solutions. However, such solutions have disadvantages such as poor selectivity of intelligent MOS transistors, high prices, and limited output power; or traditional control methods, such as relays plus fuses, which have problems such as short switch operation life and untimely protection.

[0003] If a MOS control plus output protection solution is adopted, it has the advantages of intelligent MOS transistors, and at the same time can output large currents and has low costs.

[0004] MOS transistors can also be applied to various lighting controls in automobiles, controls of various electrical appliances, and protection of various current outputs in the power control box. Therefore, the current detection of automotive MOS transistors is also an important guarantee for the normal operation of automobiles.

[0005] Commonly used MOS current detection methods include:

[0006] As Figure 1 shown, the low-side output current detection method of a commonly used NMOS transistor: For the low-side output of the NMOS transistor, a resistor RT is used to detect the current magnitude, and the magnitude of the NMOS output current is calculated through the voltage drop across RT. (Vck is the MCU sampling voltage value)

[0007] As Figure 2 shown, the high-side output current detection method of a commonly used NMOS transistor: For the high-side output of the NMOS transistor, a dedicated current detection chip is used to detect the current at the front end of the NMOS. Vck is the voltage value output by the current detection chip, and there is a proportional relationship between the voltage output by Vck and the flowing current. The MCU collects the Vck voltage to obtain the current value.

[0008] As Figure 3 shown, the high-side output current detection method of a commonly used PMOS transistor: For the high-side output of the PMOS transistor, a dedicated current detection chip is used to detect the current at the front end of the PMOS.

[0009] In addition, intelligent MOS transistors can also be used, which have a built-in current detection function. However, intelligent MOS transistors are basically monopolized by Infineon. One is the poor selectivity, and the other is that the power that intelligent MOS transistors can output is not very large, which cannot meet the requirements of large current output;

[0010] The existing MOS transistor current detection solutions are as follows: 1. Either a detection chip needs to be added or an intelligent MOS transistor is used. The power of the intelligent MOS transistor is limited and the selectivity is poor. 2. The cost is high. If there are multiple high-side power outputs in a product, the cost is even higher and the product volume is large.

[0011] Therefore, there is an urgent need for a current detection method and system for MOS transistors to solve the problems existing in the existing MOS transistor current detection process. Summary of the Invention

[0012] To solve the above problems, the present invention provides a current detection method for MOS transistors, including the following steps:

[0013] After voltage division sampling of the voltages at the D and S poles of the MOS transistor, voltage division voltage following is performed.

[0014] The voltage after following is differentially amplified and converted into a corresponding current value.

[0015] Based on the converted current value, it is judged whether the MOS transistor is overcurrent or short-circuited, and according to the judgment result, protection control is performed on the MOS transistor.

[0016] Preferably, during the voltage division sampling of the MOS transistor, the MOS transistor includes an NMOS transistor and a PMOS transistor;

[0017] The current detection method is used for high-side output current detection of NMOS transistors and PMOS transistors.

[0018] Preferably, during the voltage division sampling of the MOS transistor, based on the on-resistance of the MOS transistor, the voltage difference generated at both ends of the D and S poles of the MOS transistor is collected, and voltage division voltage following is performed.

[0019] Preferably, during the voltage division voltage following process, when detecting the currents of multiple MOS transistors simultaneously, each MOS transistor shares a following and amplifying circuit, specifically including:

[0020] The voltage division voltages at the S poles of each MOS transistor and the voltage division voltage of VC are followed and amplified;

[0021] The voltage division voltage at the S pole of each MOS transistor is followed and amplified through a multiplexer.

[0022] Preferably, during the process of obtaining the current value, the AD value of the detection circuit of each MOS transistor is obtained to generate the current value.

[0023] Preferably, during the process of judging whether the MOS transistor is overcurrent or short-circuited, a first NMOS threshold conduction voltage, a second NMOS threshold conduction voltage, a first AD threshold, and a second AD threshold are set;

[0024] Obtain a first relationship between the divided voltage and the threshold conduction voltage of the first NMOS, and a second relationship with the threshold conduction voltage of the second NMOS, where the threshold conduction voltage of the first NMOS is less than that of the second NMOS;

[0025] Obtain a third relationship between the AD value and the first AD threshold, and a fourth relationship with the second AD threshold, where the first AD threshold is less than the second AD threshold;

[0026] Judge whether the MOS transistor is overcurrent or short-circuited according to the first relationship, the second relationship, the third relationship, and the fourth relationship.

[0027] Preferably, during the process of judging whether the MOS transistor is overcurrent or short-circuited, when the collected divided voltage is greater than the threshold conduction voltage of the first NMOS and the AD value is greater than the first AD threshold, and when the divided voltage is less than the threshold conduction voltage of the second NMOS and the AD value is less than the second AD threshold, the MOS transistor is overcurrent;

[0028] When the divided voltage is greater than the threshold conduction voltage of the second NMOS and the AD value is greater than the second AD threshold, the MOS transistor is short-circuited.

[0029] Preferably, during the process of detecting that the MOS transistor is short-circuited, the MCU is used to collect the voltage difference of the MOS transistor and perform divided voltage following;

[0030] After differentially amplifying the voltage difference, by setting a short-circuit protection reference voltage and comparing it with the amplified voltage difference, an INSH signal for judging the short-circuit state is generated;

[0031] The MCU is used to detect the INSH signal;

[0032] According to the detection result, the MCU controls the protection output to start the protection control signal.

[0033] Preferably, during the process of generating the INSH signal for judging the short-circuit state, the MCU collects the voltage difference after divided voltage amplification, and through AD conversion, generates a current value;

[0034] The MCU is used to detect the current value, judge whether the MOS transistor is short-circuited, and when the judgment result is short-circuited, control the MCU to start the protection control signal.

[0035] The present invention also provides a current detection system for a MOS transistor, including:

[0036] A divided voltage sampling module, which is used to perform divided voltage sampling on the voltages of the D pole and the S pole of the MOS transistor and then perform divided voltage following;

[0037] The AD conversion module is used to perform differential voltage amplification on the subsequent voltage and convert it into a corresponding current value;

[0038] The detection module is used to determine whether the MOS transistor is overcurrent or short-circuited based on the converted current value, and perform protection control on the MOS transistor according to the judgment result.

[0039] The present invention discloses the following technical effects:

[0040] The current detection method mentioned in the present invention is particularly suitable for current detection applied in overcurrent and short-circuit protection, providing a new technical idea for the current detection of MOS transistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0042] Figure 1 It is a schematic diagram of the low-side output current detection method of a common NMOS transistor described in the background art of the present invention;

[0043] Figure 2 It is a schematic diagram of the high-side output current detection method of a common NMOS transistor described in the background art of the present invention;

[0044] Figure 3 It is a schematic diagram of the high-side output current detection method of a common PMOS transistor described in the background art of the present invention;

[0045] Figure 4 It is a schematic diagram of the high-side output current detection method of the NMOS transistor described in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all of them. Usually, the components of the embodiments of the present application described and illustrated herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0047] Such asFigures 1-4 As shown in Figures 1-4 , the present invention provides a current detection method for a MOS transistor, comprising the following steps:

[0048] After voltage division sampling of the voltages at the D and S terminals of the MOS transistor, voltage following of the divided voltages is performed.

[0049] The followed voltage is differentially amplified and converted into a corresponding current value.

[0050] Based on the converted current value, it is determined whether the MOS transistor is overcurrent or short-circuited, and according to the determination result, protection control is performed on the MOS transistor.

[0051] Further preferably, in the process of voltage division sampling of the MOS transistor, the MOS transistor includes an NMOS transistor and a PMOS transistor;

[0052] The current detection method is used for high-side output current detection of NMOS transistors and PMOS transistors.

[0053] Further preferably, in the process of voltage division sampling of the MOS transistor, based on the on-resistance of the MOS transistor, the voltage difference generated at both ends of the D and S terminals of the MOS transistor is collected, and voltage following of the divided voltages is performed.

[0054] Further preferably, in the process of voltage following of the divided voltages, when detecting the currents of multiple MOS transistors simultaneously, each MOS transistor shares a following and amplifying circuit, specifically including:

[0055] The divided voltage at the S terminal of each MOS transistor and the divided voltage of VC are followed and amplified;

[0056] The divided voltage at the S terminal of each MOS transistor is followed and amplified through a multiplexer.

[0057] Further preferably, in the process of obtaining the current value, the present invention generates the current value by obtaining the AD value of the detection circuit of each MOS transistor.

[0058] Further preferably, in the process of determining whether the MOS transistor is overcurrent or short-circuited, the present invention sets a first NMOS threshold conduction voltage, a second NMOS threshold conduction voltage, a first AD threshold, and a second AD threshold;

[0059] Obtain a first relationship between the divided voltage and the first NMOS threshold conduction voltage, and a second relationship with the second NMOS threshold conduction voltage, wherein the first NMOS threshold conduction voltage is less than the second NMOS threshold conduction voltage;

[0060] Obtain a third relationship between the AD value and the first AD threshold, and a fourth relationship with the second AD threshold, wherein the first AD threshold is less than the second AD threshold;

[0061] Based on the first relationship, the second relationship, the third relationship, and the fourth relationship, determine whether the MOS transistor is overcurrent or short-circuited.

[0062] Further preferably, in the process of determining whether the MOS transistor is overcurrent or short-circuited in the present invention, when the divided voltage is greater than the first NMOS threshold conduction voltage and the AD value is greater than the first AD threshold, and when the divided voltage is less than the second NMOS threshold conduction voltage and the AD value is less than the second AD threshold, the MOS transistor is overcurrent;

[0063] When the divided voltage is greater than the second NMOS threshold conduction voltage and the AD value is greater than the second AD threshold, the MOS transistor is short-circuited.

[0064] Further preferably, in the process of detecting that the MOS transistor is short-circuited in the present invention, the present invention collects the voltage difference of the MOS transistor through the MCU and performs divided voltage tracking;

[0065] After differentially amplifying the voltage difference, by setting the short-circuit protection reference voltage and comparing it with the amplified voltage difference, an INSH signal for judging the short-circuit state is generated;

[0066] The INSH signal is detected through the MCU;

[0067] According to the detection result, the MCU controls the protection output to start the protection control signal.

[0068] Further preferably, in the process of generating the INSH signal for judging the short-circuit state in the present invention, the present invention collects the voltage difference after divided voltage amplification through the MCU and generates a current value through AD conversion;

[0069] Through the MCU, the current value is detected to judge whether the MOS transistor is short-circuited. When the judgment result is short-circuited, the MCU is controlled to start the protection control signal.

[0070] The present invention also provides a current detection system for a MOS transistor, including:

[0071] A divided voltage sampling module, which is used to perform divided voltage sampling on the voltages of the D pole and the S pole of the MOS transistor and then perform divided voltage tracking;

[0072] An AD conversion module, which is used to differentially amplify the followed voltage and convert it into a corresponding current value;

[0073] A detection module, which is used to judge whether the MOS transistor is overcurrent or short-circuited based on the converted current value, and perform protection control on the MOS transistor according to the judgment result.

[0074] The present invention also discloses a removable storage device for performing a current detection method for MOS transistors;

[0075] The present invention also discloses a computer program, which is implemented in the form of a current detection system through a computer program according to the method logic of the current detection method for MOS transistors.

[0076] As Figure 4 shown: Taking the high-side output of NMOS as an example. The PMOS output current detection method is the same, except for the output control and protection control circuits. The low-side output current detection method of NMOS is simpler. For the low-side output of NMOS, its S terminal is grounded. By using the internal resistance characteristic of MOS conduction, the voltage at the D terminal when MOS is conducting is directly detected, amplified, and AD converted to obtain the corresponding current relationship:

[0077] 1: Since MOS has an on-resistance, a voltage difference will be generated across the D and S terminals of the MOS transistor when current flows through it.

[0078] 2: Voltage division sampling of the voltage across the D and S terminals of the MOS transistor.

[0079] 3: Voltage follower for the voltage division across the D and S terminals of the MOS transistor.

[0080] 4: Differential amplification of the followed voltage.

[0081] 5; For the amplified voltage, the MCU performs AD conversion to obtain the corresponding current value.

[0082] 6: Determine and analyze whether there is overcurrent or short circuit, and whether to perform corresponding protection control.

[0083] 7: Logical relationship: As shown in Table 1:

[0084] Table 1

[0085] MCU control status MOS status VDS voltage difference V AD value of MCU Action to be performed by MCU N No output current = VC > VAD2 ------ Y Normal output <Vth0 <VAD0 ------- Y Normal output ～＝0 ～＝0 Open circuit, no load Y Overcurrent output > Vth1 > VAD1 Overcurrent protection Y Short circuit > Vth2 > VAD2 Short circuit protection

[0086] ~=0<VAD0<VAD1<VAD2

[0087] ~=0<Vth0<Vth1<Vth2<=VC

[0088] Circuit description:

[0089] 1. 0R1 and 0R2 are voltage division resistors for VC;

[0090] 2. 1T1 and nT1 are NMOS;

[0091] 3. 0D1 and nD1 are freewheeling diodes of NMOS;

[0092] 4. U1 and U2 are operational amplifier chips;

[0093] 5. U3 is a multiplexer. When there are many output channels, multiple multiplexers can be used.

[0094] 6. OUT0 and OUTn are the output voltages of MOS transistors.

[0095] 7. VC is the system voltage of the product, generally 12V, or 24V, or 48V, etc.

[0096] 8. VCC is the operating voltage of the MCU, generally 3.3V or 5V.

[0097] 9. CH0 and CHn are the drive signals that can be controlled by the MCU of NMOS. The voltage of CH0 ≥ VC + Vth (Vth is the threshold conduction voltage of NMOS).

[0098] 10. CL0 and CLn are the signals that can be controlled by the MCU. When abnormal conditions such as MOS overcurrent, short circuit, or overheating are detected, the CH0 signal and the CL0 signal are controlled to quickly turn off the output of the MOS transistor.

[0099] 11. Vch0 and Vchn are the divided voltages of the output voltage of the MOS transistor.

[0100] 12. CSA, CSB, and CSC are the multiplexing control signals of the multiplexer, and INH is the operating enable signal of the multiplexer.

[0101] 13. COMS is the common output terminal of the multiplexer.

[0102] 14. The MCU controls the multiplexer, collects the XFAD voltage, obtains the AD value of each channel, and thus obtains the corresponding current value of each MOS.

[0103] 15. When overcurrent and short circuit are detected, the MCU turns off the control output and starts the protection control.

[0104] 16. The MCU is a microprocessor or a single-chip microcomputer.

[0105] When detecting multiple currents, a single follower and amplifier circuit is shared:

[0106] 1. The divided voltage of the S pole of each MOS transistor and the divided voltage of VC are followed and amplified.

[0107] 2. The divided voltage of the S pole of each MOS transistor is voltage-followed and amplified through the multiplexer.

[0108] 3. The follower amplification of the divided voltage of the S pole of each MOS transistor shares a single follower amplification.

[0109] The method of short-circuit protection through voltage comparison is shown in Table 2:

[0110] 1: The first method of short - circuit protection: The MCU collects the XFAD voltage, calculates the current value after AD conversion, and analyzes whether to perform short - circuit protection;

[0111] 2: The second method of short - circuit protection: After differentially amplifying the voltage difference across the MOS transistor, the voltage signal SXF is obtained. Then, the SXF voltage is compared with the set short - circuit protection reference voltage VHZ. When the MCU detects that this signal is at a high level (in the case of MOS controlled output), it is in a short - circuit state. The MCU controls the protection output, closes the CH0 signal output control signal, and activates the CL0 protection control signal;

[0112] 3: VHZ - the short - circuit protection reference setting voltage, obtained by dividing the MCU system voltage VCC;

[0113] 4: R6, R7 and the operational amplifier form a voltage comparison circuit;

[0114] Table 2

[0115] MCU control status MOS status INSH status Action to be performed by MCU N No output current H / Y Normal output L / Y Short circuit status H Start protection

[0116] The current detection mentioned in the present invention is particularly suitable for current detection applied in over - current and short - circuit protection.

[0117] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general - purpose computer, a special - purpose computer, an embedded processor, or other programmable data - processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data - processing devices generate means for implementing the specified functions in one process Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0118] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0119] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A current detection method for MOS transistors, characterized in that, Including the following steps: After voltage division sampling of the voltages at the D and S poles of the MOS transistor, perform voltage follower for the divided voltages; Differentially amplify the voltage after following and convert it into a corresponding current value; Based on the converted current value, determine whether the MOS transistor is overcurrent or short-circuited, and according to the determination result, perform protection control on the MOS transistor; During the process of voltage division sampling of the MOS transistor, the MOS transistor includes an NMOS transistor and a PMOS transistor; The current detection method is used for the high-side output current detection of the NMOS transistor and the PMOS transistor; During the process of voltage division sampling of the MOS transistor, based on the on-resistance of the MOS transistor, collect the voltage difference generated at both ends of the D and S poles of the MOS transistor, and perform the voltage follower for the divided voltages; During the process of performing voltage follower for the divided voltages, when detecting the currents of multiple MOS transistors simultaneously, each MOS transistor shares a following and amplifying circuit, specifically including: Perform voltage follower amplification on the divided voltage of the S pole of each MOS transistor and the divided voltage of VC; Perform voltage follower amplification on the divided voltage of the S pole of each MOS transistor through a multiplexer; During the process of obtaining the current value, obtain the AD value of the detection circuit of each MOS transistor and generate the current value; During the process of determining whether the MOS transistor is overcurrent or short-circuited, set the first NMOS threshold conduction voltage, the second NMOS threshold conduction voltage, the first AD threshold, and the second AD threshold; Obtain the first relationship between the VDS voltage difference and the first NMOS threshold conduction voltage, and the second relationship with the second NMOS threshold conduction voltage, where the first NMOS threshold conduction voltage is less than the second NMOS threshold conduction voltage; Obtain the third relationship between the AD value and the first AD threshold, and the fourth relationship with the second AD threshold, where the first AD threshold is less than the second AD threshold; According to the first relationship, the second relationship, the third relationship, and the fourth relationship, determine whether the MOS transistor is overcurrent or short-circuited.

2. The method for detecting current of a MOS transistor according to claim 1, wherein: During the process of determining whether the MOS transistor is overcurrent or short-circuited, when it is collected that the VDS voltage difference is greater than the first NMOS threshold conduction voltage and less than the second NMOS threshold conduction voltage, and the AD value is greater than the first AD threshold and less than the second AD threshold, the MOS transistor is overcurrent; When the VDS voltage difference is greater than the second NMOS threshold conduction voltage and the AD value is greater than the second AD threshold, the MOS transistor is short-circuited.

3. The method for detecting current of a MOS transistor according to claim 2, wherein During the process of detecting that the MOS transistor is short-circuited, through the MCU, collect the voltage difference of the MOS transistor and perform voltage follower for the divided voltages; After differentially amplifying the voltage difference, by setting a short-circuit protection reference voltage, compare it with the amplified voltage difference to generate an INSH signal for judging the short-circuit state; Detect the INSH signal through the MCU; According to the detection result, the MCU controls the protection output to start the protection control signal. Alternatively, during the process of generating the INSH signal for judging the short - circuit state, the MCU samples the voltage difference after voltage division and amplification, and generates a current value through AD conversion. The MCU detects the current value to judge whether the MOS transistor is short - circuited. When the judgment result is short - circuited, the MCU is controlled to start the protection control signal.

4. A current detection system for a MOS transistor, characterized in that, It includes: A voltage - division sampling module for performing voltage - division sampling on the voltages of the D - pole and S - pole of the MOS transistor and then performing voltage - division voltage following. An AD conversion module for differentially amplifying the followed voltage and converting it into a corresponding current value. A detection module for judging whether the MOS transistor is over - current or short - circuited based on the converted current value, and performing protection control on the MOS transistor according to the judgment result; the MOS transistor includes an NMOS transistor and a PMOS transistor; the detection module is also used for detecting the high - side output current of the NMOS transistor and the PMOS transistor. During the process of performing voltage - division sampling on the MOS transistor, the voltage - division sampling module is used to collect the voltage difference generated at both ends of the D - pole and S - pole of the MOS transistor based on the on - resistance of the MOS transistor and perform the voltage - division voltage following; during the process of performing voltage - division voltage following, when detecting the currents of multiple MOS transistors simultaneously, each MOS transistor shares a following and amplifying circuit, specifically including: the voltage - division voltage of the S - pole of each MOS transistor and the voltage - division voltage of VC are followed and amplified; the voltage - division voltage of the S - pole of each MOS transistor is followed and amplified through a multiplexer. During the process of the detection module obtaining the current value, it obtains the AD value of the detection circuit of each MOS transistor and generates the current value. During the process of judging whether the MOS transistor is over - current or short - circuited, a first NMOS threshold conduction voltage, a second NMOS threshold conduction voltage, a first AD threshold, and a second AD threshold are set. Obtain a first relationship between the VDS voltage difference and the first NMOS threshold conduction voltage, and a second relationship with the second NMOS threshold conduction voltage, where the first NMOS threshold conduction voltage is less than the second NMOS threshold conduction voltage. Obtain a third relationship between the AD value and the first AD threshold, and a fourth relationship with the second AD threshold, where the first AD threshold is less than the second AD threshold. Judge whether the MOS transistor is over - current or short - circuited according to the first relationship, the second relationship, the third relationship, and the fourth relationship.

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