Overcurrent driving protection circuit with adjustable output duty ratio

Abstract

The invention belongs to the technical field of high-side driving overcurrent protection, and particularly relates to a protection circuit with an adjustable overcurrent driving output duty ratio. Comprising an over-current detection circuit, an adjustable duty ratio circuit, driving control logic, a field tube driver and a field tube. The over-current state of the high-side driving circuit is detected by using the over-current detection circuit, the field-effect tube grid driving circuit is controlled by using the logic gate circuit, the high-side driving working state is changed, the field-effect tube and the high-side driving circuit are protected to work in a non-over-current state, and meanwhile, the over-current state of the high-side driving circuit is controlled by using the adjustable duty ratio circuit in the capacitor charging and discharging process. The output duty ratio of the field effect transistor driving signal is adjusted, the corresponding logic gate circuit is selected according to the driving control logic, the non-working state proportion of the high-side driving circuit is amplified, and the average current of the high-side driving circuit in the overcurrent protection state is further reduced. The circuit provided by the invention is easy to realize, has strong anti-interference capability, and can effectively detect an overcurrent fault and reduce the average output current in an overcurrent state.

Description

Technical Field

[0001] The invention belongs to the technical field of high-side drive overcurrent protection, and in particular relates to an overcurrent drive protection circuit with adjustable output duty cycle. Background Art

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

[0003] At present, the common high-side drive overcurrent detection circuit mainly collects the voltage across the sampling resistor through the operational amplifier. The operational amplifier circuit is easily affected by common-mode interference, and the operational amplifier power supply is also difficult. It needs to be able to withstand the surge and spike voltage of the high-side power supply. The system cost is high, and the drive circuit constantly switches between the working and non-working states in the overcurrent state. The duty cycle of the effective output state of the drive control signal is large, and the actual power consumption of the drive circuit is large, which limits the actual application. Therefore, an overcurrent protection circuit that can withstand the surge and spike of the high-side power supply and reduce the average output current is needed. Summary of the invention

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

[0005] The technical solution of the present invention:

[0006] A protection circuit with adjustable overcurrent drive output duty cycle, comprising: an overcurrent detection circuit, an adjustable duty cycle circuit, a drive control logic, a field tube driver and a field tube;

[0007] The overcurrent detection circuit detects the current size of the driving circuit;

[0008] The adjustable duty cycle circuit is connected to the overcurrent detection circuit, outputs a driving signal in an overcurrent state when the current of the driving circuit exceeds a threshold value, and adjusts the time proportion of the output state of the driving circuit in the overcurrent state;

[0009] 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.

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

[0011] The input end of D1 is connected to the output end of the overcurrent detection circuit, and the output end is connected to one end of R5, one end of R6 and the positive pole of V5; the other end of V5 is connected to the positive pole of the power supply; the other end of R6 is connected to the negative pole 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 of the low state to the duty cycle of the high state that needs to be set is determined.

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

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

[0016] D1 is the OD gate output. When the output of D1 changes from low to high, the positive electrode of the power supply charges C3 through R5 and V5. When the output of D1 changes from high to low, C3 discharges through R6. The resistance value 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 is a high effective drive output circuit:

[0018] The drive control logic circuit is provided with a Schmitt trigger, which conditions 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 non-output time ratio of the drive circuit is greater than the output time ratio.

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

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

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

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

[0023] Furthermore, the overcurrent detection circuit is connected to the driving circuit, collects the current value of the driving circuit according to the voltage difference across the sampling resistor R0, converts the current value into a voltage value and transmits it to the input end of D1;

[0024] The resistor R3 that converts the current value into the voltage value in the overcurrent detection circuit is selected based on the following method:

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

[0026] Beneficial effects of the present invention:

[0027] The present invention uses an "overcurrent detection circuit" to detect the overcurrent state of the high-side drive circuit, uses a logic gate circuit to control the field effect tube gate drive circuit, changes the working state of the high-side drive, protects the field effect tube and the high-side drive circuit from working in a non-overcurrent state, and uses the "adjustable duty cycle circuit" capacitor charging and discharging process to adjust the output duty cycle of the field effect tube drive signal, selects the corresponding logic gate circuit according to the drive control logic, amplifies the non-working state ratio of the high-side drive circuit, and further reduces the average current of the high-side drive circuit in the overcurrent protection state. The "overcurrent detection circuit" includes a voltage following function, a current following function, an amplification adjustment function, and a current acquisition function. The voltage following function is used to obtain the current flowing through the load and convert it into a voltage signal. The current following function is used to convert this voltage signal into a collectable current signal, and this current is transmitted to the current acquisition function to realize the voltage conversion of the overcurrent detection current. The amplification adjustment function ensures that the voltage following function module and the current following function are in a normal working state. The "adjustable duty cycle circuit" includes a capacitor charging circuit and a capacitor discharging circuit. By adjusting the resistance of the charging and discharging loops, the charging and discharging speed of the capacitor is changed, thereby reducing the output effective signal state ratio in the drive control logic signal, and cooperating with the drive control logic to reduce the average current of the overcurrent protection state of the high-side drive circuit. The present invention is simple in design, easy to implement, and has strong anti-interference ability. It can effectively detect the overcurrent state of the high-side drive circuit and reduce the average current of the overcurrent protection state of the high-side drive circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is the functional block diagram of the high-side driver control;

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

[0031] Figure 3 This is the schematic diagram of the adjustable duty cycle circuit. DETAILED DESCRIPTION

[0032] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0033] The following describes the embodiments of the present disclosure 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. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0034] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an 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 described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0035] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present disclosure. The illustrations only show components related to the present disclosure rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

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

[0037] In one embodiment of the present invention, a protection circuit with adjustable overcurrent drive output duty cycle is provided, comprising: an overcurrent detection circuit, an adjustable duty cycle circuit, a drive control logic, a field control driver and a field control;

[0038] The overcurrent detection circuit detects the current size of the driving circuit;

[0039] The adjustable duty cycle circuit is connected to the overcurrent detection circuit, outputs a driving signal in an overcurrent state when the current of the driving circuit exceeds a threshold value, and adjusts the time proportion of the output state of the driving circuit in the overcurrent state;

[0040] 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.

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

[0042] The input end of D1 is connected to the output end of the overcurrent detection circuit, and the output end is connected to one end of R5, one end of R6 and the positive pole of V5; the other end of V5 is connected to the positive pole of the power supply; the other end of R6 is connected to the negative pole 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 of the low state to the duty cycle of the high state that needs to be set is determined.

[0045] In this embodiment, the driving control logic has a high effective driving output circuit or a low effective driving output circuit.

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

[0047] D1 is the OD gate output. When the output of D1 changes from low to high, the positive electrode of the power supply charges C3 through R5 and V5. When the output of D1 changes from high to low, C3 discharges through R6. The resistance value 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 is a high effective drive output circuit:

[0049] The drive control logic circuit is provided with a Schmitt trigger, which conditions 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 non-output time ratio of the drive circuit is greater than the output time ratio.

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

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

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

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

[0054] In this embodiment, the overcurrent detection circuit is connected to the driving circuit, collects the current value of the driving circuit according to the voltage difference between the two ends of the sampling resistor R0, converts the current value into a voltage value and transmits it to the input end of D1;

[0055] The resistor R3 that converts the current value into the voltage value in the overcurrent detection circuit is selected based on the following method:

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

[0057] In the overcurrent protection circuit with high effective drive control logic of this embodiment, the resistance value of R5 is set to be greater than R6, and the charging speed of C3 is less than the discharging speed, that is, the speed of the comparator output from low to high is less than the speed from high to low. The drive control logic circuit includes a Schmitt trigger, which conditions 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 the drive circuit's non-output time is greater than the proportion of the output time.

[0058] Similarly, in the overcurrent protection circuit with high effective drive control logic, the resistance value of R5 is set smaller than that of R6, so the charging speed of capacitor C3 is greater than the discharging speed, that is, the speed of the comparator output from low to high is greater than the speed from high to low. The drive control logic circuit includes a Schmitt trigger, which conditions the drive signal into a square wave. The duty cycle of the low state in the drive signal is smaller than that of the high state, and the proportion of the drive circuit's non-output time is greater than the proportion of the output time.

[0059] The overcurrent protection circuit of the present embodiment has an adjustable duty cycle of the driving signal, and the specific circuit operation process is as follows:

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

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

[0062] Please also see Figure 1 , Figure 2 ,in, Figure 1 This is the engine high-side drive control function block diagram. Figure 2 This is the schematic diagram of the overcurrent detection circuit. Figure 3 It is the schematic diagram of the adjustable duty cycle circuit.

[0063] Example 1: Combination Figure 2 , describing the static working condition of the current detection circuit, cases 1 to 4 are described as the current continues to increase.

[0064] Case 1: When the load current I=0, that is, no current passes 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 cut-off state, and the voltage across R3 is 0V.

[0065] Case 2: When the load current I gradually increases (I gradually increases), that is, when there is current passing through the "current sampling resistor" R0, the voltage across the resistor R0 is "R0*I", the transistor V1 is turned on, the transistor V2 is turned on, the emitter voltage of V2 is "50V-R0*I", the base voltage of V2 is about "49.3V-R0*I", the transistor V3 is gradually turned on, the emitter and collector currents of the transistor V3 are basically equal, both approximately equal to "R0*I / R1", so 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 the resistor R0 is "R0*Iv2", the transistor V1 is turned on, the transistor V3 is turned on, and the transistor V2 is in the cut-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 the resistor R3 in case 2. Case 4: When the load current I continues to increase, the transistor V1 is turned on, the transistor V3 is turned on, the transistor V2 is in the cut-off state, and the V4 diode is turned on to protect 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 situations 1, 2, 3 and 4, in the non-overcurrent state, the overcurrent detection circuit must be ensured to work in situations 1 and 2. The capacitor C1 is used to protect the transistor V3, and the capacitor C2 is used to confirm the overcurrent time and filter out the overcurrent burrs.

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

[0069] 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 thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A protection circuit with adjustable overcurrent drive output duty cycle, characterized in that , including over-current detection circuit, adjustable duty cycle circuit, drive control logic, field control driver and field control; The overcurrent detection circuit detects the current size of the driving circuit; The adjustable duty cycle circuit is connected to the overcurrent detection circuit, outputs a driving signal in an overcurrent state when the current of the driving circuit exceeds a threshold value, and adjusts the time proportion of the output state of the driving circuit in the overcurrent 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.

2. The overcurrent drive output duty cycle adjustable protection circuit according to claim 1, characterized in that ,The adjustable duty ratio circuit includes: a comparator D1, a resistor R5, a resistor R6, a diode V5 and a capacitor C3; The input end of D1 is connected to the output end of the overcurrent detection circuit, and the output end is connected to one end of R5, one end of R6 and the positive pole of V5; the other end of V5 is connected to the positive pole of the power supply; the other end of R6 is connected to the negative pole of V5, one end of C3 and the drive control logic; the other end of C3 is grounded.

3. The overcurrent drive output duty cycle adjustable protection circuit according to claim 2, characterized in that , the ratio of R5 to R6 is based on: The ratio of the duty cycle of the low state to the duty cycle of the high state that needs to be set is determined.

4. The overcurrent drive output duty cycle adjustable protection circuit according to claim 3, characterized in that , the driving control logic has a high effective driving output circuit or a low effective driving output circuit.

5. The overcurrent drive output duty cycle adjustable protection circuit according to claim 4, characterized in that , when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic is a high effective drive output circuit: D1 is the OD gate output. When the output of D1 changes from low to high, the positive electrode of the power supply charges C3 through R5 and V5. When the output of D1 changes from high to low, C3 discharges through R6. The resistance value of R5 is greater than that of R6.

6. The overcurrent drive output duty cycle adjustable protection circuit according to claim 5, characterized in that , when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic is a high effective drive output circuit: The drive control logic circuit is provided with a Schmitt trigger, which conditions 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 non-output time ratio of the drive circuit is greater than the output time ratio.

7. The overcurrent drive output duty cycle adjustable protection circuit according to claim 6, characterized in that , when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic is a low effective drive output circuit: D1 is the OD gate output. When the output of D1 changes from low to high, the positive electrode of the power supply charges C3 through R5 and V5. When the output of D1 changes from high to low, C3 discharges through R6. The resistance value of R5 is smaller than that of R6.

8. The overcurrent drive output duty cycle adjustable protection circuit according to claim 7, characterized in that , when the adjustable duty cycle circuit is in an overcurrent state, and the drive control logic is a low effective drive output circuit: The drive control logic circuit is provided with a Schmitt trigger, which conditions the drive signal into a square wave. The duty cycle of the low state in the drive signal is smaller than the duty cycle of the high state, and the non-output time ratio of the drive circuit is greater than the output time ratio.

9. The overcurrent drive output duty cycle adjustable protection circuit according to claim 8, characterized in that ,The over-current detection circuit is connected to the driving circuit, and collects the current value of the driving circuit according to the voltage difference across the sampling resistor R0, converts the current value into a voltage value and transmits it to the input end of D1; The resistor R3 that converts the current value into the voltage value in the overcurrent detection circuit is selected based on the following method: The overcurrent threshold value *R3>the reference terminal voltage of D1.

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