Overcurrent protection circuit, system and device for MOS tube high-side output

Abstract

The present application discloses an overcurrent protection circuit, system and device for high-side output of MOS tube. The overcurrent protection circuit comprises: a gate drive circuit, a voltage detection circuit, a protection control circuit, a time delay power supply circuit, an overcurrent protection resistor and a MOS tube. The voltage detection circuit is provided with a comparator. The overcurrent protection resistor is respectively connected to a load and the MOS tube. The protection control circuit is respectively connected to a control signal end, a gate drive circuit and an output end of the comparator. The gate drive circuit is connected to the gate of the MOS tube. The time delay power supply circuit is respectively connected to the comparator and the control signal end. The negative end of the comparator is connected to the load. When the MOS output voltage is overcurrent or short-circuited, the overcurrent protection circuit can protect the MOS tube from being damaged by the short circuit in real time and lock the protection until the control signal changes. The short-circuit overcurrent state and the MOS tube non-output state are distinguished, so that when the voltage drop at both ends of the MOS tube is large, the comparator will not output a protection signal.

Description

Technical Field

[0001] The present application relates to the field of electronic circuit technology, and in particular, to an overcurrent protection circuit, system and device for high-side output of a MOS tube. Background Art

[0002] With the control of various lights on the car, the control of various electrical appliances, and the protection of various current outputs in the power control box, etc.

[0003] The output mode of MOS tube as a switch is divided into low-side output and high-side output. Low-side output means that the power supply is connected to the load first, and the load is grounded through the MOS tube. High-side output means that the power supply passes through the MOS tube first and then connects to the load, and then the load is grounded. Before turning on the MOS tube output, due to the large voltage difference of the MOS tube, the comparator outputs a protection signal, causing the MOS tube to fail to conduct normally. Summary of the invention

[0004] The purpose of the present application is to provide an overcurrent protection circuit, system and device for the high-side output of a MOS tube, so as to solve the problem that when there is a large voltage difference between the MOS tubes, the comparator outputs a control signal causing the MOS tubes to fail to conduct normally.

[0005] In order to solve the above problems, the present application adopts the following technical solutions:

[0006] The first aspect of the present application provides an overcurrent protection circuit for the high-side output of a MOS tube, comprising: a gate drive circuit, a voltage detection circuit, a protection control circuit, a time delay power supply circuit, an overcurrent protection resistor and a MOS tube, wherein the voltage detection circuit is provided with a comparator, the overcurrent protection resistor is respectively connected to a load and the MOS tube, the protection control circuit is respectively connected to a control signal end, the gate drive circuit and an output end of the comparator, the gate drive circuit is connected to the gate of the MOS tube, the time delay power supply circuit is respectively connected to the comparator and the control signal end, and the negative end of the comparator is connected to the load.

[0007] Further, the voltage detection circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a second capacitor and a third capacitor, the two ends of the first resistor are respectively connected to the load and the negative terminal of the comparator, one end of the second resistor and one end of the second capacitor are both connected to the negative terminal of the comparator, the other end of the second resistor and the other end of the second capacitor are both grounded, the third resistor, one end of the fourth resistor, and one end of the third capacitor are all connected to the positive terminal of the comparator, and the other end of the fourth resistor and the other end of the third capacitor are both grounded.

[0008] Furthermore, the voltage detection circuit further includes a diode, one end of the diode is connected to the voltage, and the other end of the diode is connected to the third resistor.

[0009] Furthermore, the delayed power supply circuit includes a fifth resistor and a first capacitor, one end of the fifth resistor is connected to the control signal end, the other end of the fifth resistor is respectively connected to the comparator and one end of the first capacitor, and the other end of the first capacitor is grounded.

[0010] Furthermore, the protection control circuit includes a transistor, a seventh resistor and an eighth resistor, the control signal end is connected to the collector of the transistor via the sixth resistor, the eighth resistor is respectively connected to the base and emitter of the transistor, and the two ends of the seventh resistor are respectively connected to the base of the transistor and the output end of the comparator.

[0011] Furthermore, the MOS tube is a PMOS tube, the gate of the PMOS tube is connected to the gate driving circuit, and the overcurrent protection resistor is connected to the drain of the PMOS tube.

[0012] Furthermore, the MOS tube is an NMOS tube, the gate of the NMOS tube is connected to the gate driving circuit, and the overcurrent protection resistor is connected to the source of the NMOS tube.

[0013] Furthermore, the overcurrent protection circuit for the high-side output of the MOS tube includes a voltage follower circuit, the number of the voltage detection circuits is multiple, and the positive terminals of the multiple comparators are all connected to the voltage follower circuit.

[0014] A second aspect of the present application provides an overcurrent protection system for a MOS tube high-side output, comprising: a shell having a receiving cavity formed therein, and an overcurrent protection circuit for a MOS tube high-side output as described in any one of the above items, arranged in the shell.

[0015] A third aspect of the present application provides an overcurrent protection device for a high-side output of a MOS tube, and the overcurrent protection device for a high-side output of a MOS tube includes the above-mentioned system.

[0016] Compared with the prior art, the beneficial effects of the present application are as follows: since the overcurrent protection circuit is provided with a gate drive circuit, a voltage detection circuit, a protection control circuit, a time delay power supply circuit, an overcurrent protection resistor and a MOS tube, and the voltage detection circuit is provided with a comparator, when the MOS output voltage is overcurrent or short-circuited, the overcurrent protection circuit can protect the MOS tube from being damaged by a short circuit in real time, and lock the protection until the control signal changes, and at the same time, the voltage difference between the two ends of the MOS tube is detected by the comparator, the reference voltage value of the positive end of the comparator changes with the change of VC, and the output end of the comparator outputs a high level only in association with the voltage difference between the two ends of the MOS tube. The power supply of the comparator is provided by the control signal of the control signal end, which effectively distinguishes the short-circuit overcurrent state and the MOS tube non-output state, so that the voltage drop at the two ends of the MOS tube is very large, and since the comparator does not work, the comparator will not output a protection signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the circuit diagram of overcurrent protection for the high-side output of a single PMOS tube;

[0018] Figure 2 A circuit diagram of an overcurrent protection circuit for a single NMOS tube high-side output; and

[0019] Figure 3 This is the circuit diagram of a voltage follower circuit.

[0020] Description of reference numerals:

[0021] 1. Gate drive circuit; 2. Voltage detection circuit; 3. Protection control circuit; 4. Delay power supply circuit; 5. Control signal terminal; 6. Voltage follower circuit;

[0022] K1, switch; VC, power supply voltage; Vout, output voltage of MOS tube; R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; R7, seventh resistor; R8, eighth resistor; R9, ninth resistor; R10, tenth resistor; C1, first capacitor; C2, second capacitor; C3, third capacitor; U1, comparator; D1, diode; Q1, transistor; CON0, control signal terminal; RL, overcurrent protection resistor; T1, MOS tube. DETAILED DESCRIPTION

[0023] The specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0024] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0025] It should be understood that the orientation or position relationship is based on the orientation or position relationship shown in the drawings. These orientation terms are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply 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 application.

[0026] The body controller on the car is now used to control various lights, various electrical appliances, or digital distribution boxes and various current control outputs of the body domain controller. All of them use the high-side output of multiple MOS tubes to output power, or use MOS to replace traditional fuses. When the MOS tube is overcurrent, it needs to be protected in time to make the MOS tube work in a safe area to prevent the MOS tube from being damaged. Especially in the application of MOS tubes in automobiles, short-circuit overcurrent protection is the most core key. It is related to the safety of the vehicle and is also the core of designing ordinary MOS into intelligent MOS tubes. In current technical means, comparators are often combined with MOS tubes. A comparison threshold voltage is set at the positive input end of the comparator. When the reverse input end of the comparator exceeds the threshold voltage, the comparator outputs a protection voltage signal. The comparator is used to detect the change of the voltage difference between the input and output ends of the MOS tube. When the voltage difference between the two ends reaches a certain value, the comparator outputs a voltage signal.

[0027] However, the commonly used comparator circuit cannot solve the overcurrent protection of MOS tubes. When MOS turns off the output, the voltage at the input end of the MOS tube is higher than the voltage at the output end. This difference voltage will also trigger the comparator output, and the short-circuit overcurrent state will also trigger the comparator output. In vehicles, the working range of the vehicle is wide. For example, in a 24V system, 16V to 32V are required to work normally, and the comparator cannot use a fixed comparison voltage. At the same time, before turning on the MOS tube output, due to the large voltage difference of the MOS tube, the comparator outputs a protection signal, causing the MOS tube to be unable to conduct normally; after the comparator outputs the protection signal, even if the MOS tube overcurrent short circuit state is released at this time, the protection output must be locked, and the MOS tube can no longer output.

[0028] In view of this, an embodiment of the present application provides an overcurrent protection circuit for a high-side output of a MOS tube, which uses the characteristics of a comparator to protect the high-side output of the MOS tube from short-circuit overcurrent, thereby solving the above-mentioned problems.

[0029] Figure 1 This is the circuit diagram of overcurrent protection for the high-side output of a single PMOS tube. Figure 2 This is the circuit diagram of the overcurrent protection circuit for the high-side output of a single NMOS tube. Figure 3 This is the circuit diagram of the voltage follower circuit. Figures 1 to 3As shown, an embodiment of the present application provides an overcurrent protection circuit for a high-side output of a MOS tube, comprising: a gate drive circuit 1, a voltage detection circuit 2, a protection control circuit 3, a time delay power supply circuit 4, an overcurrent protection resistor RL and a MOS tube T1, wherein the voltage detection circuit 2 is provided with a comparator U1, the overcurrent protection resistor RL is respectively connected to a load and the MOS tube T1, the protection control circuit 3 is respectively connected to a control signal terminal CON0, a gate drive circuit 1 and an output terminal of the comparator U1, the gate drive circuit 1 is connected to the gate of the MOS tube T1, the time delay power supply circuit 4 is respectively connected to the comparator U1 and the control signal terminal CON0, and the negative terminal of the comparator U1 is connected to the load.

[0030] Specifically, the high-side output of the MOS tube T1 is connected to the load, and the overcurrent protection resistor RL is connected between the load and the MOS tube T1. When the MOS tube is an NMOS tube, the overcurrent protection resistor RL is connected to the source of the MOS tube T1, and when the MOS tube is a PMOS tube, the overcurrent protection resistor RL is connected to the drain of the MOS tube T1. The comparator U1 in the voltage detection circuit 2 is connected to the load. For example, the load is represented by Vout. At this time, Vout is connected to the negative terminal of the comparator U1, and the overcurrent protection resistor RL is connected to Vout. The protection control circuit 3 is connected to the control signal terminal CON0, the gate drive circuit 1 and the output terminal of the comparator U1. The gate drive circuit 1 is connected to the gate of the MOS tube T1 to control the conduction and shutdown of the MOS tube T1. The delay power supply circuit 4 is connected to the comparator U1 and the control signal terminal CON0 to ensure that after the control signal terminal CON0 receives the protection signal, it can provide power to the comparator U1 in time so that it can work normally.

[0031] Since the overcurrent protection circuit is provided with a gate drive circuit 1, a voltage detection circuit 2, a protection control circuit 3, a time delay power supply circuit 4, an overcurrent protection resistor RL and a MOS tube T1, and the voltage detection circuit 2 is provided with a comparator U1, when the output voltage of the MOS tube is overcurrent or short-circuited, the overcurrent protection circuit can protect the MOS tube from being damaged by a short circuit in real time, and lock the protection until the control signal changes. At the same time, the voltage difference between the two ends of the MOS tube is detected by the comparator, and the reference voltage value of the positive terminal of the comparator U1 changes with the change of VC, and the output of the comparator U1 outputs a high level only in association with the voltage difference between the two ends of the MOS tube. The power supply of the comparator U1 is provided by the control signal of the control signal end, which effectively distinguishes the short-circuit overcurrent state and the MOS tube non-output state, so that the voltage drop at the two ends of the MOS tube is very large. Since the comparator does not work, the comparator will not output a protection signal.

[0032] It should be understood that in the gate drive circuit 1, K1 represents a switch, and K1 can be various electronic switches. The gate drive circuit 1 controls the gate of the MOS tube through CON0 to control the on and off of the MOS. In the voltage detection circuit 2, the voltage at both ends of the MOS is detected through the positive input terminal and the negative input terminal of the comparator U1. When the voltage drop at the output end of the MOS tube reaches a certain difference voltage, the output end of the comparator U1 outputs a high-level signal. At the same time, when the output end of the voltage comparator outputs a high-level signal, the protection control circuit 3 pulls down the control signal of the MCU (microprocessor), and turns off the output of the MOS tube under the control of the gate drive circuit 1. The power supply of the delay power supply circuit 4 comes from the CON0 control signal, which is delayed by the RC circuit to supply power to the working power supply VCC of the comparator U1.

[0033] In some embodiments, the voltage detection circuit 2 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a second capacitor C2 and a third capacitor C3, the two ends of the first resistor R1 are respectively connected to the load and the negative terminal of the comparator U1, one end of the second resistor R2 and one end of the second capacitor C2 are both connected to the negative terminal of the comparator U1, the other end of the second resistor R2 and the other end of the second capacitor C2 are both grounded, the third resistor R3, one end of the fourth resistor R4, and one end of the third capacitor C3 are all connected to the positive terminal of the comparator U1, and the other end of the fourth resistor R4 and the other end of the third capacitor C3 are both grounded.

[0034] Specifically, the first resistor R1 is connected between the load and the negative terminal of the comparator U1, and the second resistor R2 and the second capacitor C2 are connected in parallel to the negative terminal of the comparator U1 to filter out noise and interference. The third capacitor C3 and the fourth resistor R4 are connected in parallel to the positive terminal of the comparator U1, the third resistor R3 is connected to the positive terminal of the comparator U1, and the other end of the third resistor R3 is connected to VC (power supply voltage).

[0035] In some embodiments, the voltage detection circuit 2 further includes a diode D1 , one end of the diode D1 is connected to a voltage, and the other end of the diode D1 is connected to a third resistor R3 .

[0036] Optionally, the diode D1 is connected to the voltage detection circuit 2. Specifically, one end of the diode D1 is connected to VC, and the other end is connected to the third resistor R3, so that the flow can only flow from the power supply voltage VC through the diode D1 and the third resistor R3 into the positive terminal of U1.

[0037] In some embodiments, the delayed power supply circuit 4 includes a fifth resistor R5 and a first capacitor C1, one end of the fifth resistor R5 is connected to the control signal end, the other end of the fifth resistor R5 is respectively connected to the comparator U1 and one end of the first capacitor C1, and the other end of the first capacitor C1 is grounded.

[0038] Specifically, when CON0 of the control signal terminal 5 is at a high level, the delay power supply circuit 4 delays supplying power to the VCC terminal of the comparator U1, and the output voltage of the MOS tube rises to a steady state of a normal output voltage, so that the MOS tube can output normally and avoid triggering protection. The delay time of the RC (fifth resistor R5 and first capacitor C1) delay power supply circuit is called the RC delay time.

[0039] In some embodiments, the protection control circuit 3 includes a transistor Q1, a seventh resistor R7 and an eighth resistor R8, the control signal terminal 5 is connected to the collector of the transistor Q1 via the sixth resistor R6, the eighth resistor R8 is respectively connected to the base and emitter of the transistor Q1, and the two ends of the seventh resistor R7 are respectively connected to the base of the transistor Q1 and the output end of the comparator U1.

[0040] Specifically, the control signal terminal 5 is connected to the collector of the transistor Q1 through the sixth resistor R6, the eighth resistor R8 is connected to the base and emitter of the transistor Q1 respectively, and the two ends of the seventh resistor R7 are connected to the base of the transistor Q1 and the output end of the comparator U1 respectively. The control signal terminal 5 receives an external control signal, and limits the current through the sixth resistor R6 to protect the transistor Q1 from being damaged by excessive current. The transistor Q1 is used as a switching element, and its collector is connected to the control signal terminal 5 through the sixth resistor R6, the base is connected to the control signal terminal CON5 through the eighth resistor R8, and the emitter is connected to other parts of the circuit. The working state of the transistor Q1 is controlled by the signal of the control signal terminal 5 to realize the switching function of the circuit.

[0041] The control signal of CON0 after passing through the current limiting resistor R1, the control signal and the Q1 control tube (transistor) jointly control the switch of the gate drive circuit 1 to control the on and off of the MOS tube.

[0042] In some embodiments, the MOS tube is a PMOS tube, a gate of the PMOS tube is connected to the gate driving circuit 1 , and an overcurrent protection resistor RL is connected to a drain of the PMOS tube.

[0043] Specifically, the MOS tube is a PMOS tube, and its gate is connected to the gate drive circuit 1 to control the conduction state of the PMOS tube. The resistor RL is connected to the drain of the PMOS tube and is used to adjust the voltage drop between VC and VOUT. The gate drive circuit 1 provides a drive signal to the gate of the PMOS tube to control the conduction and cutoff of the PMOS tube. Under normal working conditions, the gate drive circuit 1 will provide an appropriate control voltage to the gate of the PMOS tube according to the change of the control signal, so that the PMOS tube is turned on when needed and cut off when not needed. The overcurrent protection resistor RL is connected between the drain of the PMOS tube and the power supply to limit the current flowing through the PMOS tube.

[0044] In some embodiments, the MOS tube is an NMOS tube, a gate of the NMOS tube is connected to a gate driving circuit, and an overcurrent protection resistor RL is connected to a source of the NMOS tube.

[0045] Specifically, the gate of the NMOS tube is connected to the gate drive circuit 1 to control the conduction state of the NMOS tube. The overcurrent protection resistor RL is connected to the source of the NMOS tube to limit the current flowing through the NMOS tube to prevent the NMOS tube from being damaged due to overcurrent. The gate drive circuit 1 provides a drive signal for the gate of the NMOS tube to control the conduction and cutoff of the NMOS tube.

[0046] In some embodiments, the overcurrent protection circuit for the high-side output of the MOS tube includes a voltage follower circuit 6 , there are multiple voltage detection circuits 4 , and the positive terminals of multiple comparators U1 are all connected to the voltage follower circuit 6 .

[0047] Specifically, see Figure 2 and Figure 3 As shown, the overcurrent protection circuit for the high-side output of the MOS tube includes a voltage follower circuit 6 and multiple gate drive circuits 1, multiple voltage detection circuits 2, multiple protection control circuits 3, multiple delay power supply circuits 4 and multiple control signal terminals 5, and the positive terminal of each comparator U1 is connected to the voltage follower circuit 6 (that is, the overcurrent protection circuit for the high-side output of the MOS tube includes a voltage follower circuit 6 and multiple Figure 2 The voltage follower circuit 6 is used to follow the change of the power supply voltage and provide a stable reference voltage for the voltage detection circuit 4 and the comparator U1. The voltage follower circuit 6 includes an operational amplifier and related resistor elements, which can provide a stable voltage output and maintain good following performance even in high-frequency applications. The comparator U1 compares the reference voltage provided by the voltage follower circuit 6 and the voltage detected by the voltage detection circuit 4. If the detected voltage exceeds the reference voltage, the comparator U1 will generate a high-level output signal to trigger the overcurrent protection action.

[0048] A second aspect of the present application provides an overcurrent protection system for a MOS tube high-side output, comprising: a shell having a receiving cavity formed therein, and any of the above-mentioned overcurrent protection circuits for a MOS tube high-side output, arranged in the shell.

[0049] A third aspect of the present application provides an overcurrent protection device for a high-side output of a MOS tube. The overcurrent protection device for a high-side output of a MOS tube includes the above-mentioned system.

[0050] In order to better understand the overcurrent protection circuit for the high-side output of the MOS tube in the embodiment of the present application, the protection process of the high-side output of a single-channel PMOS and a single-channel NMOS tube and the short-circuit overcurrent protection process of multiple MOS high-side outputs are specifically described below.

[0051] like Figure 2 As shown, when CON0 is at a high level, the gate drive circuit 1 works, the VG voltage is turned on, and the T1 tube (MOS tube) works. When CON0 is at a low level, the VG voltage is disconnected, and T1 turns off the output. Among them, the power supply voltage VC can be a 12V system, a 24V system, or a 48V system, etc. The signal of CON0 after passing through the current limiting resistor R1, this signal and the Q1 control tube (transistor) jointly control the switch of the gate drive circuit 1 to control the on and off of the MOS tube. VG is the driving voltage of NMOS. The VG voltage is the VC voltage plus the NMOS turn-on voltage. When NMOS is fully turned on, VG is generally 8V-12V higher than VC. U1 represents a comparator, where + is its positive input terminal, - is its positive input terminal, GND is the ground terminal of the chip, and VCC is the positive terminal of the chip working power supply;

[0052] In the overcurrent protection of the high-side output of the PMOS tube, the difference between it and the overcurrent protection of the high-side output of the NMOS tube is as follows: the gate drive control of the PMOS is different. To control the NMOS to turn on, the gate voltage must be controlled to be higher than the input voltage VC, so that the NMOS conduction threshold is within a reasonable range. To control the PMOS to turn on, the gate voltage must be controlled to be lower than the input voltage VC, so that the PMOS conduction threshold is within a reasonable range. Figure 1 In the circuit, R10 is used as a pull-up resistor and R9 is used as a current limiting resistor.

[0053] The principle of short-circuit overcurrent protection for the high-side outputs of multiple PMOS and multiple NOMS is similar. When the high-side outputs of multiple MOS are the same, a positive-end divided voltage (provided by a voltage follower circuit) can be shared, and then the divided voltage signal after the voltage division can be followed to increase the load capacity of the signal, and then a voltage signal is given to the positive input terminal of the comparator of the voltage detection circuit of each MOS tube, thereby saving space for components and circuit boards.

[0054] The working process of NMOS is as follows:

[0055] (1) When the positive input voltage of comparator U1 is higher than the negative input voltage, the output of the comparator will output a high voltage signal; U1ra = R1 / R2 is the positive voltage divider coefficient, and U2ra = R3 / R4 is the negative voltage divider coefficient. The Vout voltage value is lower than the difference between the VC voltage values ​​and the comparator triggers the output high level at this time. This difference voltage is called the trigger difference voltage. When R1=R3, R2=R4, the voltage divider coefficients at both ends of the comparator are the same, and the VC voltage signal is connected in series with diode D1 to enter the positive input of the comparator. At this time, the trigger difference voltage is the voltage drop of D1. Two or more diodes can be connected in series to change the trigger difference voltage, or the voltage divider coefficient can be changed to change the trigger difference voltage.

[0056] (2) When the MOS tube has no control output, that is, CON0 has no control signal, although the trigger difference voltage is reached at this time, CON0 is at a low level, the VCC operating voltage of the comparator U1 is low, the comparator U1 is in a non-working state, and the protection control circuit does not work.

[0057] (3) When the MCU issues a control command, CON0 is at a high level, and the RC delay power supply circuit (delay power supply circuit 4) delays the supply of power to the VCC terminal of the comparator U1. During this period, the output voltage of the MOS tube rises to the steady state of the normal output voltage, allowing the MOS tube to output normally and avoid triggering protection. The delay time of the RC delay power supply circuit is called the RC delay time.

[0058] (4) When the MCU controls the MOS to turn on and power on, and the load of the MOS tube is too heavy or the load is short-circuited, the steady-state time of the MOS tube output is greater than the RC delay time, and the comparator U1 outputs a high level. The protection control circuit starts the protection function, pulls the CON0 signal low, and controls the gate drive circuit 1 to turn off the MOS tube. This process is called protection control. This is the short-circuit overcurrent protection process when power is on, and the protection control will be locked until CON0 changes back to a low level and then to a high level again. The protection control process protection circuit needs to be re-detected and controlled again. The change process of CON0 from a high level to a low level and then to a high level is called a control signal change.

[0059] It should be noted that the combination of software and hardware can also be used. The MCU detects the output state of the MOS tube. Through logical judgment, CON0 is high and the MOS tube output is low. The MCU knows that the protection circuit is in the protection control state. The MCU no longer outputs CON0 high level, and the protection circuit is kept in the protection lock state until the MCU system is powered on again.

[0060] (5) When the MOS tube output reaches a steady state, the load of the MOS tube is too heavy or short-circuited. Due to the increase in the voltage drop between the MOS tube and the overcurrent protection resistor RL, when the trigger difference voltage is reached, the protection control will be started and locked. This is the short-circuit overcurrent protection during the MOS operation process.

[0061] It should be noted that in the overcurrent protection circuit for the high-side output of the MOS tube in the embodiment of the present application, the comparator U1 detects the voltage difference between the two ends of the MOS tube, and the reference voltage value of the positive end of the comparator U1 is not a fixed value, but a value that changes with the change of VC. The condition for the output end of the comparator U1 to output a high level is only related to the voltage difference between the two ends of the MOS tube. The power supply of the comparator U1 is supplied by the control signal CON0, which effectively distinguishes the short-circuit overcurrent state and the MOS non-output state. The voltage difference between the input and output ends of the MOS tube in these two states will be greater than the trigger difference voltage. Since the working voltage of the comparator U1 is controlled by CON0, in the MOS non-output state, although the voltage drop between the two tubes of the MOS tube is large, the comparator will not output a protection signal because the comparator does not work.

[0062] At the same time, RC delay (delay power supply circuit 1) is adopted, and the control signal CON0 delays the power supply to the working pin of the comparator U1, so that the MOS tube can start normally. The overcurrent protection circuit is a hardware short-circuit overcurrent protection circuit. When the MOS output is overcurrent or short-circuited, the short-circuit overcurrent protection circuit can protect the MOS from damage due to short circuit in real time, and lock the protection until the control signal changes. Therefore, it can effectively protect the MOS tube from short circuit or overload before it is turned on and started, or short circuit or overload after the MOS tube works normally. The size of the current limiting protection current can be changed by adjusting the size of the overcurrent protection resistor RL or not RL, or changing the size of the internal resistance of the MOS tube T1; the size of the current limiting protection current can also be changed by adjusting the voltage divider coefficient between the positive and negative ends of the comparator U1. At this time, the diode can also be used to change the size of the protection current.

[0063] When the voltage division coefficients of the positive terminal and the negative terminal of the comparator U1 are the same, the size of the current limiting protection current can be changed by changing the silicon material diode and the germanium diode; by using a device with a high-side power output controlled by the control terminal, the overcurrent protection circuit of the embodiment of the present application can be used for short-circuit overcurrent protection, such as relay output, etc. Detect the voltage changes at both ends of the power device and the overcurrent protection resistor RL, and control the control signal in combination with the logic circuit to achieve the purpose of short-circuit overcurrent protection. When there are multiple MOS tube outputs, the reference voltage of the positive end of the comparator U1 can be shared and the voltage follower circuit 6 can be used to reduce the space of electronic devices and circuit boards.

[0064] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the same. Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present application.

Claims

1. An overcurrent protection circuit for high-side output of a MOS tube, characterized in that: include: A gate drive circuit, a voltage detection circuit, a protection control circuit, a time-delay power supply circuit, an overcurrent protection resistor and a MOS tube, wherein the voltage detection circuit is provided with a comparator, the overcurrent protection resistor is respectively connected to a load and the MOS tube, the protection control circuit is respectively connected to a control signal terminal, the gate drive circuit and an output terminal of the comparator, the gate drive circuit is connected to the gate of the MOS tube, the time-delay power supply circuit is respectively connected to the comparator and the control signal terminal, and the negative terminal of the comparator is connected to the load; The voltage detection circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a second capacitor and a third capacitor, the two ends of the first resistor are respectively connected to the load and the negative terminal of the comparator, one end of the second resistor and one end of the second capacitor are both connected to the negative terminal of the comparator, the other end of the second resistor and the other end of the second capacitor are both grounded, the third resistor, one end of the fourth resistor, and one end of the third capacitor are all connected to the positive terminal of the comparator, and the other end of the fourth resistor and the other end of the third capacitor are both grounded.

2. An overcurrent protection circuit for high-side output of a MOS tube according to claim 1, characterized in that: The voltage detection circuit further comprises a diode, one end of the diode is connected to a voltage, and the other end of the diode is connected to the third resistor.

3. The overcurrent protection circuit for high-side output of a MOS tube according to claim 1, characterized in that: The delayed power supply circuit includes a fifth resistor and a first capacitor, one end of the fifth resistor is connected to the control signal end, the other end of the fifth resistor is respectively connected to the comparator and one end of the first capacitor, and the other end of the first capacitor is grounded.

4. The overcurrent protection circuit for high-side output of a MOS tube according to claim 1, characterized in that: The protection control circuit includes a transistor, a seventh resistor and an eighth resistor. The control signal end is connected to the collector of the transistor via the sixth resistor. The eighth resistor is respectively connected to the base and emitter of the transistor. The two ends of the seventh resistor are respectively connected to the base of the transistor and the output end of the comparator.

5. The overcurrent protection circuit for high-side output of a MOS tube according to claim 1, characterized in that: The MOS tube is a PMOS tube, a gate of the PMOS tube is connected to the gate driving circuit, and the overcurrent protection resistor is connected to the drain of the PMOS tube.

6. The overcurrent protection circuit for high-side output of a MOS tube according to claim 1, characterized in that: The MOS tube is an NMOS tube, the gate of the NMOS tube is connected to the gate driving circuit, and the overcurrent protection resistor is connected to the source of the NMOS tube.

7. The overcurrent protection circuit for high-side output of a MOS tube according to claim 1, characterized in that: The overcurrent protection circuit for the high-side output of the MOS tube includes a voltage follower circuit. The number of the voltage detection circuits is multiple, and the positive terminals of the multiple comparators are all connected to the voltage follower circuit.

8. An overcurrent protection system for high-side output of a MOS tube, characterized in that: include: A shell having a receiving cavity formed therein, and an overcurrent protection circuit for high-side output of a MOS tube according to any one of claims 1 to 7 are arranged in the shell.

9. An overcurrent protection device for high-side output of a MOS tube, characterized in that: The overcurrent protection device for the high-side output of the MOS tube includes the system described in claim 8.

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