CN115800975A - High-side power switch driving circuit with overcurrent protection - Google Patents

Abstract

The invention discloses a high-side power switch driving circuit with overcurrent protection, which belongs to the technical field of power MOSFET driving and comprises a NAND gate, a delay circuit, an AND gate, a driving circuit, a resistor R1, a P-channel MOSFET and an overcurrent detection circuit. The MOSFET driving circuit can determine whether the MOSFET chip is in an overcurrent condition by detecting the size of the VDS (ON), but the overcurrent detection based ON the VDS (ON) is affected by whether the load is open and whether the MOSFET is ON. The overcurrent detection function of the P-channel MOSFET is realized by monitoring the magnitude of VDS (ON), and the output can be recovered only when the control signal EN is enabled again. Through verification, the electromagnetic valve can ensure the normal work of the electromagnetic valve, the reliability of the product is improved, and the requirement of the domestic development of aviation equipment is met.

Description

High side power switch drive circuit with overcurrent protection

technical field

The invention belongs to the technical field of power MOSFET driving, and in particular relates to a high-side power switch driving circuit with overcurrent protection.

Background technique

In the full-authority electronic controller of aero-engines, the high-side power switch circuit is widely used in the control of solenoid valves. In the aircraft engine control system, the solenoid valve is an important control element, which directly affects the on-off or reversing of the engine fuel and lubricating oil pipelines. Whether the solenoid valve can work normally will directly affect the work and safety of the engine. Therefore, the high-side power switch circuit is directly related to the working performance and operation safety of the entire engine control system.

Traditional high-side power switch circuits are all implemented based on intelligent power switch chips, and can realize functions such as overcurrent protection, but there is no high-side power switch integrated chip that meets the needs of aviation equipment in China. Switching circuits can only be realized based on power MOSFETs. However, the MOSFET tube has a weak ability to withstand overload, so its practical use is greatly limited. How to design a reliable and reasonable over-current protection circuit plays a vital role in giving full play to the advantages of MOSFET power tubes and avoiding their weaknesses, and is also an important prerequisite for reliable operation of high-side power switches.

Contents of the invention

In view of this, the present invention provides a high-side power switch drive circuit with overcurrent protection to realize a reliable drive scheme for P-channel MOSFETs. When the external load finds a fault such as a short circuit, it will automatically disconnect the high-side power switch, and It will always remain disconnected to avoid irreversible damage to the P-channel MOSFET caused by multiple outputs. Whether the high-side power switch is turned on again after overcurrent is controlled by software, which is more flexible and improves system reliability.

A high-side power switch drive circuit with overcurrent protection, including a NAND gate circuit, a delay circuit, an AND gate circuit, a drive circuit, a resistor R1, a P-channel MOS tube and an overcurrent detection circuit, and an external software control signal The EN output terminal is electrically connected to one input terminal of the AND gate circuit and the NAND gate circuit respectively, and the output terminal of the overcurrent detection circuit is connected to the other input terminal of the NAND gate circuit;

The input terminal of the delay circuit is connected to the output terminal of the NAND circuit, and the output terminal is connected to the other input terminal of the AND circuit;

The output terminal of the AND gate circuit is connected to the input terminal of the drive circuit, and the two ends of the resistor R1 are respectively connected to the output terminal of the drive circuit and the gate of the P-channel MOS transistor;

The two input ends of the overcurrent detection circuit are respectively connected to the output end of the driving circuit and the drain of the P-channel MOS transistor, and the source of the P-channel MOS transistor is connected to the power supply VDD.

Technical beneficial effect of the present invention:

The MOSFET drive circuit can judge whether the MOSFET chip is in an overcurrent situation by detecting the size of the device VDS(ON), but the overcurrent detection based on VDS(ON) will be affected by whether the load is open or the MOSFET is turned on. The present invention realizes the overcurrent detection function of the P-channel MOSFET by monitoring the magnitude of VDS(ON), and the output is restored only when the control signal EN is re-enabled, and at the same time, the irreversible situation of the MOSFET is avoided. It has been verified that the invention can ensure the normal operation of the electromagnetic valve, increase the reliability of the product, and meet the research and development requirements of the localization of aviation equipment. The high-side power switch circuit with over-current protection function is realized only by common components such as optocoupler, conventional gate circuit, RC, and FET. The structure is simple, easy to use, and low cost; and it can realize national production design , and the circuit parameters are adjustable and have a wide range of applications. It is used in the full-authority digital electronic controller products of multi-type aero-engines. It has passed various engine system test verifications and aircraft installation verifications, and the system runs stably and reliably.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure. Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is a functional block diagram of a high-side power switch circuit with an overcurrent protection function in the present invention;

FIG. 2 is a hardware schematic diagram of a high-side power switch circuit with an overcurrent protection function according to the present invention.

Detailed ways

Embodiments of the present disclosure will be described in detail below in conjunction with the accompanying drawings.

Embodiments of the present disclosure are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Apparently, the described embodiments are only some of the embodiments of the present disclosure, not all of them. The present disclosure can also be implemented or applied through different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, in the case of no conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in the present disclosure, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present disclosure.

It is noted that the following describes various aspects of the embodiments that are within the scope of the appended claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is illustrative only. Based on the present disclosure one skilled in the art should appreciate that an aspect described herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, any number of the aspects set forth herein can be used to implement an apparatus and/or practice a method. In addition, such an apparatus may be implemented and/or such a method practiced using other structure and/or functionality than one or more of the aspects set forth herein.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. A certain type of engine fuel solenoid valve has a driving voltage of not less than 25V and a driving current of not less than 2A, and the function of realizing overcurrent protection is described.

Referring to Figure 1, the schematic diagram of the circuit hardware is shown in Figure 2, which includes a NAND circuit, a delay circuit, an AND circuit, a drive circuit, a resistor R1, a P-channel MOSFET and an overcurrent detection circuit; the software control signal EN simultaneously Connected to the input end of the AND gate circuit and the NAND gate circuit, the other input end of the NAND gate circuit is connected to the output end of the overcurrent detection circuit, the input end of the delay circuit is connected to the output end of the NAND gate circuit, and the output end of the delay circuit is connected to the output end of the NAND gate circuit. The other input terminal of the AND gate circuit is connected, the output terminal of the AND gate circuit is connected with the input terminal of the drive circuit, the two ends of the resistor R1 are respectively connected with the output terminal of the drive circuit and the gate of the P-channel MOSFET, and the two input terminals of the overcurrent detection circuit are The output terminal of the drive circuit is connected with the drain of the P-channel MOSFET. The source of the P-channel MOSFET is connected to the power supply VDD. The VDD voltage of the power supply is 28V, and the resistance value of the resistor R1 is 10Ω. The P-channel MOSFET is SQD40P10-40L-GE3 from VISHAY Company, and the drain current ID can reach 38A, which meets the requirements.

As shown in FIG. 2, the delay circuit includes a resistor R2, a capacitor C1 and a diode Q3. One end of the resistor R2 is connected to the output end of the NAND circuit and the positive end of the diode Q3 at the same time, the other end of the resistor R2 is connected to the negative end of the diode Q3 and one end of the capacitor C1, and the other end of the capacitor C1 is connected to the ground. The selected NAND gate circuit is MC74HC00ADG of ON SEMI Company, and the AND gate circuit is MC74HC08ADG of ONSEMI Company, both of which are powered by +5VDC. According to the device manual, the output high level voltage of MC74HC00ADG is 4.9V, and the input high level threshold of MC74HC08ADG is 3.5V. The resistance value of the resistor R2 is 10KΩ, and the capacitance value of the capacitor C1 is 4.7nF. According to the capacitor discharge model, it can be known that the delay time τ=0.33*R2*C1=15.5uS.

The relationship between the delay time τ of the above-mentioned time delay circuit and R2 and C1 is: the resistance value of τ=K*resistance R2*the capacitance of capacitor C1, wherein the constant K value is output high-level voltage by the NAND gate and the Determined by the ratio of the high-level voltage input to the AND gate.

The driving circuit includes a resistor R6, a resistor R7, a resistor R8 and an NPN transistor Q4. The two ends of the resistor R8 are respectively connected to the base of the NPN transistor Q4 and the output terminal of the AND gate circuit, the collector of the NPN transistor Q4 is connected to one end of the resistor R7, the other end of the resistor R7 is connected to the one end of the resistor R6 and the left end of the resistor R1, and the other end of the resistor R6 It is connected with VDD power supply, and the emitter of NPN transistor Q4 is connected with ground. The resistance value of the resistor R8 is 1KΩ, the resistance value of the resistor R7 is 20KΩ, the resistance value of the resistor R6 is 10KΩ, and the NPN transistor Q4 is MMBT2222ALT1G of ON SEMI Company. When the output terminal of the AND gate circuit is at a high level, Q4 is in a saturated state, and the P-channel gate voltage is 21V, which is lower than the VDD supply voltage of 28V, and the P-channel MOSFET is turned on.

As shown in Figure 2, the overcurrent detection circuit includes an optocoupler U3, a pull-up resistor R4, a current limiting resistor R3, an acceleration capacitor C2, a current limiting resistor R5 and a protection diode Q2. One end of the current-limiting resistor R3 is connected to the drain of the P-channel MOSFET, the other end of the current-limiting resistor R3 is connected to the positive end of the light-emitting diode of the optocoupler U3, and the negative end of the light-emitting diode of the optocoupler U3 is connected to the end of the accelerating capacitor C2 and the current-limiting One end of the resistor R5 is connected, the other end of the acceleration capacitor C2 is connected to the negative end of the protection diode Q2 and the left end of the resistor R1 at the same time, the other end of the current limiting resistor R5 is connected to the positive end of the protection diode Q2, and the output collector of the optocoupler U3 is simultaneously connected to the pull-up resistor One end of R4 is connected to the input end of the NAND gate, the other end of the pull-up resistor R4 is connected to the power supply VCC, and the output emitter of the optocoupler U3 is connected to the ground. The selected optocoupler is TCET1100 from VISHAY company, the maximum response time is 10us, the resistance of pull-up resistor R4 is 4.7KΩ, the resistance of current limiting resistors R3 and R5 is 5KΩ, the capacitance of acceleration capacitor C2 is 0.1uF, and the protection diode Q2 is BAS21HT1G of ON-SEMI Company. Among them, the accelerating capacitor C2 mainly plays an accelerating role. When the driving circuit is turned on for a moment, the gate voltage of the P-channel MOSFET drops to 18.7V instantly, and the voltage of the G terminal drops from 28V to 18V instantly. Since the voltage at both ends of the capacitor cannot be changed suddenly , the voltage at the input terminal of the optocoupler diode drops to 18V instantaneously, and the optocoupler is quickly turned on. Overcurrent detection is realized based on the working characteristics of MOSFET. The specific principle is that the MOSFET chip works in the constant current region under normal conditions, and the VDS(ON) voltage is small; but when an overcurrent fault occurs, the MOSFET chip will exit the constant current region and enter In the variable resistance area, the VDS(ON) voltage increases with the increase of the current, and when the MOSFET chip is turned on, the VGS voltage remains basically unchanged, and then the VDS(ON) voltage can be converted into the characteristic of VDG with the increase of the current Voltage changes, and then realize the over-current detection function. The response time of the overcurrent detection circuit is mainly affected by the optocoupler U3, and the longest time of the optocoupler is 10uS, which is less than the delay time τ of the delay circuit.

The working process of the high-side power switch circuit with over-current protection function includes the following steps:

Step 1: When the software control signal EN is at low level, the AND gate circuit U2 outputs low level, and the NAND gate circuit U1 outputs high level, then the NPN transistor Q4 is in the cut-off state, and the collector voltage of the NPN transistor is the same as the VDD power supply. The P-channel MOSFET is in the cut-off state, and the optocoupler U3 is in the cut-off state, then the overcurrent detection result ERROR is high level.

Step 2: When the overcurrent fault does not occur, the software control signal EN changes from low level to high level at T0. Due to the existence of the delay circuit, the output signal of the delay circuit will change after T0+15.5uS If it becomes low level, the AND gate circuit U2 outputs a high level at T0, the NPN transistor Q4 is in a saturated conduction state, and the collector voltage of the NPN transistor is grounded, and the gate voltage of the P-channel MOSFET is lower than the power supply voltage VDD, then The P-channel MOSFET is in the conduction state, and then the optocoupler U3 is in the conduction state, the response time of the overcurrent detection circuit is 10uS, which is less than the delay time τ of the delay circuit, and the overcurrent occurs within the time period of T0～T0+15.5uS The detection result ERROR will become low level, the output of the NAND gate circuit will become high level, the diode Q3 will be turned on, and the charging time will be negligible, which can ensure that the output of the delay circuit will quickly change from low level to high level. When there is no over-current fault and the software enable signal EN is high, the P-channel MOSFET is always in the conduction state.

Step 3: If the P-channel MOSFET is in the conduction process and an overcurrent fault occurs, the drain voltage of the P-channel MOSFET will decrease. When the voltage difference between the drain and the gate decreases to the point where the optocoupler U3 cannot be turned on , the overcurrent detection result ERROR becomes high level, then the delay circuit outputs low level after 15.5us, then the P-channel MOSFET can be turned off; when the software enable signal EN changes from low level to high level again Normally, the P-channel MOSFET is turned on again.

In actual work, the invention has been used in a certain type of engine full-authority digital electronic controller. After various system test verifications and installation verifications, the system runs stably and reliably, and can realize solenoid valve drive and over-current protection functions, greatly improving electronic control. The reliability of controller products.

The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present disclosure should be within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be determined by the protection scope of the claims.

Claims (8)

1. A high-side power switch drive circuit with overcurrent protection is characterized in that it comprises a NAND gate circuit, a delay circuit, an AND gate circuit, a drive circuit, a resistor R1, a P channel MOS tube and an overcurrent detection circuit, where: The output terminal of the external software control signal EN is electrically connected to one input terminal of the AND gate circuit and the NAND gate circuit respectively, and the output terminal of the overcurrent detection circuit is connected to the other input terminal of the NAND gate circuit; The input terminal of the delay circuit is connected to the output terminal of the NAND circuit, and the output terminal is connected to the other input terminal of the AND circuit; The output terminal of the AND gate circuit is connected to the input terminal of the drive circuit, and the two ends of the resistor R1 are respectively connected to the output terminal of the drive circuit and the gate of the P-channel MOS transistor; The two input ends of the overcurrent detection circuit are respectively connected to the output end of the driving circuit and the drain of the P-channel MOS transistor, and the source of the P-channel MOS transistor is connected to the power supply VDD. 2. The high-side power switch driving circuit according to claim 1, wherein the time delay circuit comprises a resistor R2, a capacitor C1 and a diode Q3, wherein: The input end of the resistor R2 is connected to the output end of the NAND gate circuit and the anode of the diode Q3, and the output end is connected to the cathode of the diode Q3 and the input end of the capacitor C1, and serves as the AND gate circuit an input terminal of The output end of the capacitor C1 is grounded. 3. The high-side power switch driving circuit with overcurrent protection according to claim 2, wherein the delay time τ of the time delay circuit is related to R2, C1 as follows: τ=K*resistor R2 The resistance value*capacitance value of the capacitor C1, wherein the value of the constant K is determined by the ratio of the high level output by the NAND gate to the high level input by the AND gate. 4. The high-side power switch driving circuit according to claim 1, wherein the driving circuit comprises a resistor R6, a resistor R7, a resistor R8 and an NPN-type transistor Q4, wherein: The two ends of the resistor R8 are respectively connected to the base of the NPN transistor Q4 and the output terminal of the AND gate circuit, the collector of the NPN transistor Q4 is connected to one end of the resistor R7, and the other end of the resistor R7 is connected to the resistor R7 respectively. One end of R6 is connected to the input end of the resistor R1, the other end of the resistor R6 is connected to the VDD power supply, and the emitter of the transistor Q4 is grounded. 5. The high-side power switch drive circuit according to claim 1, wherein the overcurrent detection circuit comprises an optocoupler U3, a pull-up resistor R4, a current limiting resistor R3, an acceleration capacitor C2, a current limiting resistor R5 and Protection diode Q2, where: One end of the current-limiting resistor R3 is connected to the drain of the P-channel MOS transistor, and the other end is connected to the anode of the light-emitting diode included in the optocoupler U3, and the cathode of the light-emitting diode is connected to the speed-up capacitor C2 respectively. One end is connected to one end of the current limiting resistor R5, and the other end of the acceleration capacitor C2 is respectively connected to the cathode of the protection diode Q2 and the input end of the resistor R1; The other end of the current-limiting resistor R5 is connected to the anode of the protection diode Q2, and the output collector of the optocoupler U3 is respectively connected to one end of the pull-up resistor R4 and the input end of the NAND circuit. The other end of the pull-up resistor R4 is connected to the power supply VCC, and the output emitter of the optocoupler U3 is grounded. 6. The over-current detection circuit according to claim 5, wherein the acceleration capacitor C2 is used to accelerate the response of the over-current detection circuit. 7. The high-side power switch driving circuit according to claim 1, wherein the delay time τ of the delay circuit should be greater than the response time of the overcurrent detection circuit. 8. A high-side power switch driving method with overcurrent protection, characterized in that, using the circuit according to any one of claims 1 to 7, comprising the following steps: Step 1: When the software control signal EN is at a low level, the AND gate circuit U2 outputs a low level and the NAND gate circuit U1 outputs a high level, then the NPN transistor Q4 is in a cut-off state, and the NPN transistor collector voltage is the same as the VDD power supply , the P-channel MOSFET is in the cut-off state, the optocoupler U3 is in the cut-off state, and the overcurrent detection result ERROR is high level; Step 2: When no overcurrent fault occurs, the software control signal EN changes from low level to high level at time T0. Due to the existence of the delay circuit, the output signal of the delay circuit becomes low after T0+τ level, then, at the time T0, the AND gate circuit U2 outputs a high level, the NPN transistor Q4 is in a saturated conduction state, the collector voltage of the NPN transistor Q4 is ground, and the gate voltage of the P-channel MOSFET is lower than the power supply voltage VDD, then The P-channel MOSFET is in the conduction state, so that the optocoupler U3 is in the conduction state, and the response time of the over-current detection circuit is less than the delay time τ of the delay circuit, and the over-current detection result is within the time period of T0-(T0+τ) ERROR becomes low level, and the output of the NAND gate circuit becomes high level, ensuring that the output of the delay circuit changes from low level to high level; When no overcurrent fault occurs and the software enable signal EN is high, the P-channel MOSFET is always in the on state; Step 3: When the P-channel MOSFET is in the conduction process and an overcurrent fault occurs, the drain voltage of the P-channel MOSFET will become smaller. When the voltage difference between the drain and the gate is reduced to the point where the optocoupler U3 cannot be turned on , the overcurrent detection result ERROR becomes a high level, and the delay circuit outputs a low level after time τ, and the P-channel MOSFET can be turned off; When the software enable signal EN changes from low level to high level again, the P-channel MOSFET will be turned on again.

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