A protection circuit with adjustable duty cycle of over-current driving output

Abstract

The present application belongs to the technical field of high-side drive over-current protection, and particularly relates to a protection circuit with adjustable duty cycle of over-current drive output. The protection circuit comprises an over-current detection circuit, an adjustable duty cycle circuit, a drive control logic, a field tube driver and a field tube. The over-current detection circuit is used to detect the over-current state of the high-side drive circuit, the logic gate circuit is used to control the gate drive circuit of the field effect tube, the working state of the high-side drive is changed, the field effect tube and the high-side drive circuit are protected to work in the non-over-current state, the adjustable duty cycle circuit is used to adjust the output duty cycle of the field effect tube drive signal through the capacitor charging and discharging process, the corresponding logic gate circuit is selected according to the drive control logic, the proportion of the non-working state of the high-side drive circuit is amplified, and the average current of the high-side drive circuit in the over-current protection state is further reduced. The circuit is easy to implement, has strong anti-interference ability, can effectively detect the over-current fault, and can reduce the average output current in the over-current state.

Description

Technical Field

[0001] This invention belongs to the field of high-side drive overcurrent protection technology, specifically relating to a protection circuit with adjustable overcurrent drive output duty cycle. Background Technology

[0002] High-side drive circuits are widely used in power electronics and other fields. Overcurrent protection of drive circuits is crucial. Current detection circuits are usually located near the circuit being detected and send the current information of the circuit being detected to the drive control circuit in the form of voltage.

[0003] Currently, common high-side drive overcurrent detection circuits primarily rely on operational amplifiers (op-amps) to sample the voltage across a sampling resistor. However, op-amp circuits are susceptible to common-mode interference, and powering them is challenging, requiring them to withstand high-side power supply surges and spikes. This results in high system costs. Furthermore, during overcurrent conditions, the drive circuit rapidly switches between operating and non-operating states, leading to a large duty cycle in the effective output state of the drive control signal and significant power consumption, thus limiting practical applications. Therefore, an overcurrent protection circuit capable of withstanding high-side power supply surges and spikes while reducing the average output current is needed. Summary of the Invention

[0004] In view of this, the present invention provides a protection circuit with an adjustable duty cycle for overcurrent drive output. The circuit is easy to implement, has strong anti-interference ability, can effectively detect overcurrent faults, and reduce the average output current under overcurrent conditions.

[0005] The technical solution of the present invention:

[0006] An overcurrent drive output duty cycle adjustable protection circuit includes: an overcurrent detection circuit, an adjustable duty cycle circuit, drive control logic, a field-effect transistor driver, and a field-effect transistor.

[0007] The overcurrent detection circuit detects the magnitude of the current in the drive circuit;

[0008] An adjustable duty cycle circuit is connected to the overcurrent detection circuit. When the current of the drive circuit exceeds the threshold, it outputs a drive signal in the overcurrent state and adjusts the time ratio of the drive circuit output state in the overcurrent state.

[0009] The drive control logic is connected to the adjustable duty cycle circuit, and controls the MOSFET driver based on the overcurrent signal, thereby controlling the working state of the MOSFET.

[0010] Furthermore, the adjustable duty cycle circuit includes: comparator D1, resistor R5, resistor R6, diode V5, and capacitor C3;

[0011] The input terminal of D1 is connected to the output terminal of the overcurrent detection circuit. The output terminal is connected to one end of R5, one end of R6, and the positive terminal of V5. The other end of V5 is connected to the positive terminal of the power supply. The other end of R6 is connected to the negative terminal of V5, one end of C3, and the drive control logic. The other end of C3 is grounded.

[0012] Furthermore, the ratio of R5 to R6 is based on:

[0013] The ratio of the duty cycle in the low state to the duty cycle in the high state needs to be determined.

[0014] Furthermore, the drive control logic has either a high-active-drive output circuit or a low-active-drive output circuit.

[0015] Furthermore, when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic has a high effective drive output circuit:

[0016] D1 is the OD gate output. When the output of D1 goes from low to high, the positive terminal of the power supply charges C3 through R5 and V5. When the output of D1 goes from high to low, C3 discharges through R6. The resistance of R5 is greater than that of R6.

[0017] Furthermore, when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic has a high effective drive output circuit:

[0018] The drive control logic circuit is equipped with a Schmitt trigger, which modulates the drive signal into a square wave. The duty cycle of the low state in the drive signal is greater than the duty cycle of the high state, and the proportion of the non-output time of the drive circuit is greater than the proportion of the output time.

[0019] Furthermore, when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic has a low active drive output circuit:

[0020] D1 is the OD gate output. When the output of D1 goes from low to high, the positive terminal of the power supply charges C3 through R5 and V5. When the output of D1 goes from high to low, C3 discharges through R6. The resistance of R5 is less than that of R6.

[0021] Furthermore, when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic has a low active drive output circuit:

[0022] The drive control logic circuit is equipped with a Schmitt trigger, which modulates the drive signal into a square wave. The duty cycle of the low state in the drive signal is less than the duty cycle of the high state, and the proportion of the non-output time of the drive circuit is greater than the proportion of the output time.

[0023] Furthermore, the overcurrent detection circuit is connected to the drive circuit. It collects the current value of the drive circuit based on the voltage difference across the sampling resistor R0, converts the current value into a voltage value, and transmits it to the input terminal of D1.

[0024] In the overcurrent detection circuit, the resistor R3 that converts the current value to a voltage value is selected based on the following method:

[0025] The overcurrent threshold *R3 > the reference terminal voltage of D1.

[0026] The beneficial effects of this invention are:

[0027] This invention utilizes an "overcurrent detection circuit" to detect the overcurrent state of the high-side drive circuit. It uses logic gates to control the gate drive circuit of the field-effect transistor (FET), changing the high-side drive's operating state to protect the FET and the high-side drive circuit, ensuring they operate in a non-overcurrent state. Simultaneously, an "adjustable duty cycle circuit" adjusts the output duty cycle of the FET drive signal during the capacitor charging and discharging process. Based on the drive control logic, appropriate logic gates are selected to amplify the proportion of the high-side drive circuit in its non-operating state, further reducing the average current of the high-side drive circuit during overcurrent protection. The "overcurrent detection circuit" includes voltage tracking, current tracking, amplification and adjustment, and current acquisition functions. The voltage tracking function acquires the load current and converts it into a voltage signal. The current tracking function converts this voltage signal into an acquireable current signal and transmits it to the current acquisition function, achieving voltage conversion of the overcurrent detection current. The amplification and adjustment function ensures that the voltage tracking and current tracking modules are in normal operating condition. The "adjustable duty cycle circuit" includes a capacitor charging circuit and a capacitor discharging circuit. By adjusting the resistance values ​​of the charging and discharging circuits, the charging and discharging speed of the capacitor is changed, thereby reducing the proportion of valid output signal states in the drive control logic signal. In conjunction with the drive control logic, this reduces the average current under overcurrent protection conditions in the high-side drive circuit. This invention is simple in design, easy to implement, and has strong anti-interference capabilities. It can effectively detect overcurrent conditions in the high-side drive circuit and reduce the average current under overcurrent protection conditions. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a block diagram of the high-side drive control function;

[0030] Figure 2 This is the schematic diagram of an overcurrent detection circuit;

[0031] Figure 3 This is a schematic diagram of an adjustable duty cycle circuit. Detailed Implementation

[0032] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0033] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0034] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0035] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The illustrations only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0036] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0037] In one embodiment of the present invention, a protection circuit with adjustable duty cycle for overcurrent drive output is proposed, comprising: an overcurrent detection circuit, an adjustable duty cycle circuit, drive control logic, a field-effect transistor driver, and a field-effect transistor.

[0038] The overcurrent detection circuit detects the magnitude of the current in the drive circuit;

[0039] An adjustable duty cycle circuit is connected to the overcurrent detection circuit. When the current of the drive circuit exceeds the threshold, it outputs a drive signal in the overcurrent state and adjusts the time ratio of the drive circuit output state in the overcurrent state.

[0040] The drive control logic is connected to the adjustable duty cycle circuit, and controls the MOSFET driver based on the overcurrent signal, thereby controlling the working state of the MOSFET.

[0041] The adjustable duty cycle circuit includes: comparator D1, resistor R5, resistor R6, diode V5, and capacitor C3;

[0042] The input terminal of D1 is connected to the output terminal of the overcurrent detection circuit. The output terminal is connected to one end of R5, one end of R6, and the positive terminal of V5. The other end of V5 is connected to the positive terminal of the power supply. The other end of R6 is connected to the negative terminal of V5, one end of C3, and the drive control logic. The other end of C3 is grounded.

[0043] In this embodiment, the ratio of R5 to R6 is based on:

[0044] The ratio of the duty cycle in the low state to the duty cycle in the high state needs to be determined.

[0045] In this embodiment, the drive control logic is either a high-active-drive output circuit or a low-active-drive output circuit.

[0046] In this embodiment, when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic has a high effective drive output circuit:

[0047] D1 is the OD gate output. When the output of D1 goes from low to high, the positive terminal of the power supply charges C3 through R5 and V5. When the output of D1 goes from high to low, C3 discharges through R6. The resistance of R5 is greater than that of R6.

[0048] In this embodiment, when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic has a high effective drive output circuit:

[0049] The drive control logic circuit is equipped with a Schmitt trigger, which modulates the drive signal into a square wave. The duty cycle of the low state in the drive signal is greater than the duty cycle of the high state, and the proportion of the non-output time of the drive circuit is greater than the proportion of the output time.

[0050] In this embodiment, when the adjustable duty cycle circuit is in an overcurrent state and the drive control logic has a low active drive output circuit:

[0051] D1 is the OD gate output. When the output of D1 goes from low to high, the positive terminal of the power supply charges C3 through R5 and V5. When the output of D1 goes from high to low, C3 discharges through R6. The resistance of R5 is less than that of R6.

[0052] In this embodiment, when the adjustable duty cycle circuit is in an overcurrent state and the drive control logic has a low active drive output circuit:

[0053] The drive control logic circuit is equipped with a Schmitt trigger, which modulates the drive signal into a square wave. The duty cycle of the low state in the drive signal is less than the duty cycle of the high state, and the proportion of the non-output time of the drive circuit is greater than the proportion of the output time.

[0054] In this embodiment, the overcurrent detection circuit is connected to the drive circuit. It collects the current value of the drive circuit based on the voltage difference across the sampling resistor R0, converts the current value into a voltage value, and transmits it to the input terminal of D1.

[0055] In the overcurrent detection circuit, the resistor R3 that converts the current value to a voltage value is selected based on the following method:

[0056] The overcurrent threshold *R3 > the reference terminal voltage of D1.

[0057] In the overcurrent protection circuit of the drive control logic in this embodiment, the resistance value of R5 is set to be greater than that of R6, and the charging speed of C3 is less than the discharging speed. That is, the comparator output speed from low to high is less than the speed from high to low. The drive control logic circuit includes a Schmitt trigger to condition the drive signal into a square wave. The duty cycle of the low state in the drive signal is greater than that of the high state, and the proportion of time the drive circuit does not output is greater than the proportion of time it outputs.

[0058] Similarly, in the overcurrent protection circuit of the drive control logic, the resistance value of R5 is set to be less than that of R6, so the charging speed of capacitor C3 is greater than the discharging speed. That is, the comparator output speed from low to high is greater than the speed from high to low. The drive control logic circuit contains a Schmitt trigger to condition the drive signal into a square wave. The duty cycle of the low state in the drive signal is less than that of the high state, and the proportion of time the drive circuit does not output is greater than the proportion of time it outputs.

[0059] This embodiment features an overcurrent protection circuit with an adjustable duty cycle for the drive signal. The specific circuit operation process is as follows:

[0060] Step 1: Based on the overcurrent I and the formula R0*I>0.7, select a reasonable sampling resistor value R0; resistor R1 is generally selected to be no greater than 1K; based on the output current value R0*I / R1 of the current follower circuit and the final voltage value to be converted, select an appropriate R3; based on R3 and the output current value R0*I / R1 of the current follower circuit, and considering the characteristics of the transistor, select an appropriate R2; based on the voltage drop of R0*I, select the value of R4 to ensure that the PNP transistor in the amplification and adjustment circuit is in the amplification region;

[0061] Step 2: Based on the effective value of the drive logic signal, select the values ​​of R5, R6, and C3 to reduce the proportion of the effective output signal state in the drive control logic signal;

[0062] Please also refer to Figure 1 , Figure 2 ,in, Figure 1 This is a functional block diagram of the engine high-side drive control. Figure 2 This is the schematic diagram of an overcurrent detection circuit. Figure 3 This is a schematic diagram of an adjustable duty cycle circuit.

[0063] Example 1: Combination Figure 2 Describe the static operation of the current detection circuit. Cases 1 to 4 are described according to the continuous increase of current.

[0064] Case 1: When the load current I = 0, that is, when no current flows through the "current sampling resistor" R0, transistor V1 is turned on, transistor V2 is turned on, the emitter voltage of V2 is +50V, the base voltage of V2 is about +49.3V, transistor V3 is in the cutoff state, and the voltage across R3 is 0V.

[0065] Scenario 2: When the load current I gradually increases (I gradually increases), that is, when current flows through the "current sampling resistor" R0, the voltage across resistor R0 is "R0*I". Transistor V1 conducts, transistor V2 conducts, the emitter voltage of V2 is "50V-R0*I", and the base voltage of V2 is approximately "49.3V-R0*I". Transistor V3 gradually conducts, and the emitter and collector currents of transistor V3 are approximately equal, both approximately equal to "R0*I / R1". Therefore, the voltage across R3 is "R0*I / R1*R3". When the load current I = 0, the voltage across R3 is also "R0*I / R1*R3".

[0066] Case 3: When the load current I increases to Iv2, the voltage across resistor R0 is "R0*Iv2". Transistor V1 is turned on, transistor V3 is turned on, and transistor V2 is in the off state. That is, the emitter voltage of V3 is greater than the emitter voltage of V2, but V4 is not triggered to turn on. At this time, the voltage across R3 is greater than the voltage across resistor R3 in case 2. Case 4: When the load current I continues to increase, transistor V1 is turned on, transistor V3 is turned on, transistor V2 is in the off state, and diode V4 is turned on, protecting V2 from being broken down by the collector and emitter voltages. At this time, the voltage across R3 is "(R0*I-2.1) / R1*R3".

[0067] Combining scenarios 1, 2, 3, and 4, under non-overcurrent conditions, the overcurrent detection circuit must be ensured to operate in scenarios 1 and 2. Capacitor C1 protects transistor V3, while capacitor C2 confirms the overcurrent duration and filters out overcurrent spikes.

[0068] When the overcurrent detection circuit detects an overcurrent condition, the drive logic signal cuts off the output. After the output is cut off, the load current decreases. After exiting the overcurrent condition, the drive logic signal continues to output. As the drive circuit continuously switches between output and non-output states, the adjustable duty cycle circuit reduces the proportion of the output valid signal state in the drive control signal, thereby reducing the average current of the high-side drive circuit under overcurrent protection.

[0069] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A protection circuit with adjustable duty cycle for overcurrent drive output, characterized in that... It includes an overcurrent detection circuit, an adjustable duty cycle circuit, drive control logic, a MOSFET driver, and a MOSFET. The overcurrent detection circuit detects the magnitude of the current in the drive circuit; An adjustable duty cycle circuit is connected to the overcurrent detection circuit. When the current in the drive circuit exceeds a threshold, it outputs a drive signal in the overcurrent state and adjusts the time ratio of the drive circuit output state in the overcurrent state. The adjustable duty cycle circuit includes: comparator D1, resistors R5 and R6, diode V5, and capacitor C3. The input terminal of D1 is connected to the output terminal of the overcurrent detection circuit, and the output terminal is connected to one end of R5, one end of R6, and the positive terminal of V5. The other end of V5 is connected to the positive terminal of the power supply. The other end of R6 is connected to the negative terminal of V5, one end of C3, and the drive control logic. The other end of C3 is grounded. The ratio of R5 to R6 needs to be determined by the ratio of the duty cycle in the low state to the duty cycle in the high state. The drive control logic is connected to the adjustable duty cycle circuit, and controls the field tube driver based on the overcurrent signal, thereby controlling the working state of the field tube; When the adjustable duty cycle circuit is in overcurrent state and the drive control logic has a high effective drive output circuit: D1 is an OD gate output. When the output of D1 goes from low to high, the positive terminal of the power supply charges C3 through R5 and V5. When the output of D1 goes from high to low, C3 discharges through R6. The resistance value of R5 is greater than that of R6. When the adjustable duty cycle circuit is in an overcurrent state and the drive control logic has a high effective drive output circuit: a Schmitt trigger is provided in the drive control logic circuit, the Schmitt trigger modulates the drive signal into a square wave, the duty cycle of the low state in the drive signal is greater than the duty cycle of the high state, and the proportion of the non-output time of the drive circuit is greater than the proportion of the output time. When the adjustable duty cycle circuit is in overcurrent state and the drive control logic has a low effective drive output circuit: D1 is an OD gate output. When the output of D1 goes from low to high, the positive terminal of the power supply charges C3 through R5 and V5. When the output of D1 goes from high to low, C3 discharges through R6. The resistance value of R5 is less than that of R6. When the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic has a low active drive output circuit: The drive control logic circuit is equipped with a Schmitt trigger, which modulates the drive signal into a square wave. In the drive signal, the duty cycle of the low state is less than the duty cycle of the high state, and the proportion of the non-output time of the drive circuit is greater than the proportion of the output time. The overcurrent detection circuit is connected to the drive circuit. It collects the current value of the drive circuit based on the voltage difference across the sampling resistor R0, converts the current value into a voltage value, and transmits it to the input terminal of D1. In the overcurrent detection circuit, the resistor R3 that converts the current value to a voltage value is selected based on the following method: Overcurrent threshold R3 > D1's reference terminal voltage.

2. The overcurrent drive output duty cycle adjustable protection circuit according to claim 1, characterized in that... The drive control logic is either a high-active-drive output circuit or a low-active-drive output circuit.

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