Special protection device for over-current and short circuit of H-bridge circuit

Abstract

The utility model discloses a special protection device for over-current and short circuit of an H-bridge circuit. The special protection device comprises a sampling resistor R20 used for detecting over-current and short circuit of the H-bridge circuit of a direct current motor control system, a driving ICU3 used for controlling on-off of the H-bridge circuit, and a current monitoring and protection unit. The output control end of the driver ICU3 is connected with the input control end of the H-bridge circuit, the enabling end of the driver ICU3 is connected with the control signal output end of the current monitoring and protection unit, and the control signal input end of the current monitoring and protection unit is connected with the sampling resistor. According to the utility model, the protection circuit composed of the integrated operational amplifier and the comparator is used, when the DC motor control system is short-circuited or over-current, the H-bridge circuit can be closed within several microseconds, thereby ensuring that circuit board elements of the DC motor control system and the DC motor are not damaged. And short-circuit signals collected by the sampling resistor are accessed to a microcontroller of a direct-current motor control system, and the signals are latched, so that logic control and operation are facilitated.

Description

TECHNICAL FIELD

[0001] The utility model relates to H bridge circuit drive circuit especially H bridge circuit overcurrent and short circuit special protection device. BACKGROUND

[0002] At present, the H bridge circuit drive is mostly used in the DC motor control system to realize the positive and reverse rotation of the DC motor. When the external machinery or the DC motor is in fault (such as blocked rotation, short circuit), the H bridge circuit is easily burnt out during the working process of the DC motor. To solve the above problem, the conventional method is to increase the fuse type or self-recovery fuse at the power supply end to prevent the H bridge circuit or the DC motor from being burnt out. Although the fuse type fuse can avoid the burning of the circuit element or the DC motor in the rear stage, the fuse type fuse needs to be replaced manually after being fused. The self-recovery fuse is a temperature sensitive device, which needs to be overheated to play a protection role, delays the protection time, and is easy to cause the protected circuit to be burnt out. In addition, because the self-recovery fuse is related to temperature, when the working temperature changes, the protection current changes, and the change is large, which is easy to cause improper protection.

[0003] The utility model discloses a kind of overcurrent and short circuit protection circuits of servo motor, current sampling signal is directly input single-chip microcontroller to judge whether H bridge is short-circuited / overcurrent by current sampling resistance, since single-chip microcomputer sampling needs to have interval time, cutting off fastest also needs tens of milliseconds, cannot protect operation to hardware in short time.

[0004] The utility model discloses a kind of controllable logic circuits and H bridge circuits for H bridge circuit, which solves the problem of preventing the upper and lower bridge arms of the H bridge circuit from being opened simultaneously, which can prevent short circuit. However, it does not solve the problem of H bridge circuit burnout caused by external machinery or motor fault (such as blocked rotation, short circuit). SUMMARY

[0005] Therefore, the utility model provides a kind of H bridge circuit overcurrent and short circuit special protection device, realizes when H bridge circuit short circuit or overcurrent occurs, quickly close H bridge circuit.

[0006] To achieve the above purpose, the utility model takes the following technical scheme:

[0007] The utility model discloses a H bridge circuit overcurrent and short circuit special protection device, including the sampling resistance R20 for detecting the overcurrent and short circuit of DC motor control system H bridge circuit, the drive ICU3 for controlling the on-off of H bridge circuit, current monitoring and protection unit, drive ICU3 output control end is connected with H bridge circuit input control end, and drive ICU3 enables end is connected with current monitoring and protection unit control signal output end, and current monitoring and protection unit control signal input end connects the sampling resistance.

[0008] Optionally, the current monitoring and protection unit comprises an integrated operational amplifier U1 and a comparator U2; the in-phase input end of the integrated operational amplifier U1 is connected with the sampling resistance R20 through a low-pass filter composed of R2 and C1; the anti-phase input end of the integrated operational amplifier U1 is connected with the output end of the integrated operational amplifier U1 through a high-pass filter composed of R3 and C2; the voltage at the output end of the integrated operational amplifier U1 is related to the input signal at the in-phase input end thereof: By selecting appropriate resistance size, the current amplification multiple adjustment is realized.

[0009] The output end of the integrated operational amplifier U1 is connected with the in-phase input end of the comparator U2 through R4; the anti-phase input end of the comparator U2 is connected with the working power supply VCC through a voltage dividing circuit composed of resistors R5 and R6; by adjusting the two resistors R5 and R6, the current size when the comparator U2 outputs a high level can be changed; the output end of the comparator U2 is connected with the enable end of the drive ICU3.

[0010] Further, the signal input end of the drive ICU3 is connected with the logic signal output end of the microcontroller of the DC motor control system respectively; the short circuit signal collected by the sampling resistance R20 of the current monitoring and protection unit is connected with the external interrupt signal input end of the microcontroller of the DC motor control system.

[0011] The utility model uses the protection circuit composed of the integrated operational amplifier and the comparator; when the short circuit or overcurrent condition occurs in the DC motor control system, the H bridge circuit can be closed within several microseconds, so that the circuit board elements of the DC motor control system and the DC motor are not damaged. Moreover, the short circuit signal collected by the sampling resistance is connected to the microcontroller of the DC motor control system, the signal is latched, and the logic control and operation are facilitated. Meanwhile, the utility model has modular design and can be used for protecting other high-power switching devices. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The utility model discloses a circuit principle drawing.

[0013] Figure 2 The utility model discloses a H bridge circuit principle drawing.

[0014] Figure 3 The direct current motor control system circuit principle block diagram is described in the utility model. DETAILED DESCRIPTION

[0015] The embodiments of the utility model will be described in detail below with reference to the drawings, and the embodiments are implemented on the premise of the technical scheme of the utility model, detailed implementation modes and specific operation processes are given, but the protection scope of the utility model is not limited to the following embodiments.

[0016] It should be noted that, in the description of the utility model, unless otherwise explicitly specified and limited, the terms "connected", "connected" that may appear should be understood broadly, for example, it can be fixedly connected, or integrally connected, it can be mechanically connected, or electrically connected, it can be directly connected, or indirectly connected through an intermediate medium, the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the utility model can be understood according to specific circumstances.

[0017] As shown in Figures 1-3 The utility model discloses a H bridge circuit overcurrent and short circuit special protection device, including the sampling resistance R20 for detecting direct current motor control system H bridge circuit overcurrent and short circuit, the drive ICU3 for controlling the on-off of H bridge circuit, current monitoring and protection unit, the drive ICU3 output control end is connected with H bridge circuit input control end, and the drive ICU3 enables end is connected with current monitoring and protection unit control signal output end, and current monitoring and protection unit control signal input end connects the high potential end of sampling resistance R20, and the low potential end of sampling resistance R20 is grounded.

[0018] The direct current motor control system of this embodiment is as shown in Figure 3As shown in the figure, the power stabilizing circuit provides stable voltage for the whole system, and the driving power provides stable voltage and sufficient current for the operation of the DC motor. The microcontroller communicates with other devices, obtains instructions, and performs other operations through the external communication interface. In order to control the speed of the DC motor, the PWM interface of the microcontroller is needed; if the speed is not needed to be controlled, only the forward and reverse rotation and start and stop functions are needed, then the PWM output port can be replaced by a normal IO port. The driving ICU3 has an enable terminal, and the enable terminal is connected to the IO port of the microcontroller. The H-bridge circuit is implemented using four standard NMOS transistors / IGBTs, and the specific model needs to be selected according to the rated power of the DC motor. The current sampling resistor R20 is connected between the common low end of the H-bridge circuit and the ground, and this resistor can collect the current flowing through the MOS transistor. The DC motor is connected through the interfaces M1 and M2 in the middle of the H-bridge circuit, and the model of the DC motor is selected according to the use scenario. In this embodiment, the current sampling resistor R20 is connected to the current monitoring and protection unit, and when the current exceeds the set value, the enable terminal of the driving ICU3 will be turned off instantly, and the signal will be sent to the interrupt port of the microcontroller. In addition, the voltage signal of the current sampling resistor R20 is amplified and connected to the pin with AD (analog-to-digital conversion) function of the microcontroller.

[0019] As Figure 2 shown, Q1, Q2, Q3, and Q4 in the H-bridge circuit of this embodiment are MOS or IGBT power switching devices matched with the rated power of the DC motor; this embodiment takes N-channel MOS transistors as an example, in which Q1 and Q3 are high sides of the H-bridge circuit, and Q2 and Q4 are low sides of the H-bridge circuit. The control signals H1, H2, L1, and L2 come from the driving IC U3, which respectively control the four MOS transistors of the H-bridge circuit and can control their opening and closing. The resistors R13, R14, R15, and R16 have one end respectively connected to the control poles of the four MOS transistors Q1, Q2, Q3, and Q4, and the other end connected to the ground terminal GND, which are pull-down resistors of the control poles, preventing the MOS transistors from malfunctioning when the output terminal of the driving IC U3 is in a high resistance state. One end of the current sampling resistor R20 is connected to the output terminal of the low side MOS transistor, and the other end is connected to the ground terminal GND. The current sampling resistor R20 is usually selected as a high-power milliohm level, so that the voltage on the DC motor M1, M2 hardly changes when the current changes.

[0020] The current sampling resistor R20 can convert the large current signal flowing through the DC motor into a voltage signal, which is led out by the network CURRENT_S for amplification / collection. The interfaces M1 and M2 connect the two ends of the DC motor to realize the forward and reverse rotation of the DC motor; at the same time, if the control signals applied to the control poles of the four MOS transistors Q1, Q2, Q3, and Q4 are PWM or other signals that change periodically, then the speed of the DC motor can be changed.

[0021] AsFigure 3 As shown, PWM1, PWM2, PWM3, PWM4 in the driving IC U3 are logic signal interfaces output by the microcontroller; the SHUT_OFF signal comes from the output end of the comparator U2, and this signal is connected to the enable end of the driving IC U3. According to the model and function of the driving IC U3, the enable end may be high active or low active. In this embodiment, the low active is taken as an example. The resistors R9, R10, R11 and R12 are connected to the output end of the driving IC U3, and the other ends of the resistors R9, R10, R11 and R12 are connected to H1, H2, L1 and L2 respectively, that is, the control ends of the four MOS tubes Q1, Q2, Q3 and Q4 in the H-bridge circuit, which are used to adjust the gate current of the four MOS tubes Q1, Q2, Q3 and Q4, so as to adjust the switching speed of the four MOS tubes Q1, Q2, Q3 and Q4, and further optimize the electromagnetic radiation. According to the function of the driving IC U3, the level of H1, H2, L1 and L2 is controlled by the input end logic signal. At the same time, when the enable end of the driving IC U3 is disabled, the output end of the driving IC U3 is in a high resistance state, and at this time, the four MOS tubes Q1, Q2, Q3 and Q4 in the H-bridge circuit are all in the off state.

[0022] As shown in the figure, Figure 3 The signal CURRENT_S comes from the current sampling resistor R20 in the H-bridge circuit module, that is, the voltage signal of the direct current motor current on the resistor. Usually, it is only in the order of millivolt. After the signal passes through the low-pass filter composed of the resistor R2 and the capacitor C1, it is connected to the non-inverting input end of the precision integrated operational amplifier U1. One end of the resistor R1 is connected to the ground, and the other end is connected to the inverting input end of the precision integrated operational amplifier U1, and is also connected to one end of the resistor R3 and the capacitor C2. The other end of the high-pass filter composed of the resistor R3 and the capacitor C2 is connected to the output end of the precision integrated operational amplifier U1, which constitutes a standard amplification circuit. The relationship between the voltage at the output end of the precision integrated operational amplifier U1 and the input signal is:

[0023] ;

[0024] The current amplification multiple is adjusted by selecting appropriate resistance values; the signal VO_U1 at the output end of the precision integrated operational amplifier U1 is connected to the pin with ADC collection function of the microcontroller, and the real-time collection of the direct current motor current is realized through the internal AD conversion of the microcontroller.

[0025] The output end of the precision integrated operational amplifier U1 is connected to the non-inverting input end of the comparator U2 through the resistor R4, the working power supply VCC is connected to the inverting input end of the comparator U2 through the voltage division of resistors R5 and R6 and the filtering capacitor C3, the current value of the high level output of the comparator U2 can be changed by adjusting the two resistors R5 and R6, the output end of the comparator U2 outputs the SHUT_OFF signal to the enable end of the driving IC U3 through the current limiting resistor R7, and the signal is input to the external interrupt input pin of the microcontroller. The function of this connection is that when the DC motor or the external interface of M1 and M2 is short-circuited or overcurrent, the current flowing through the current sampling resistor R20 will instantaneously increase, causing the output voltage of the CURRENT_S signal amplified by the precision integrated operational amplifier U1 to be too high, exceeding the threshold value set at the inverting input end of the comparator U2, so that the output end of the comparator U2 changes from the original low level to the high level; the SHUT_OFF signal is connected to the enable end of the driving IC U3 and the external interrupt pin of the microcontroller, and the output end of the driving IC U3 will instantaneously enter the high resistance state, thereby causing the H-bridge circuit to be instantaneously turned off, the current flowing through the four MOS tubes Q1, Q2, Q3 and Q4 of the H-bridge circuit is cut off, and the current flowing through the sampling resistor R20 becomes 0 again, and the SHUT_OFF signal becomes low again. In order to prevent the SHUT_OFF signal from oscillating, the SHUT_OFF signal needs to be latched, and the method is not unique and can be input to the latch or other IC. In this embodiment, the SHUT_OFF signal is input to the external interrupt pin of the microcontroller, and when the level of the SHUT_OFF signal changes, the microcontroller will immediately enter the external interrupt program, and in the interrupt program, the microcontroller will immediately make the four front-stage control signals of the H-bridge circuit, namely PWM1, PWM2, PWM3 and PWM4, output low level, and the four N-channel MOS tubes Q1, Q2, Q3 and Q4 are turned off; therefore, the four MOS tubes Q1, Q2, Q3 and Q4 can be turned off within a few microseconds when short-circuit or overcurrent occurs, so as to achieve the purpose of protecting the circuit board components and the DC motor.

[0026] The above scheme adopts current low-end sampling (the current sampling resistor is at the bottom of the H-bridge), and the current sampling resistor can also be placed at the top of the H-bridge, and a special current collection chip is used to amplify the current, which can achieve the same function.

[0027] Finally, it should be further emphasized that the above is only the preferred embodiment of the present application, and is not intended to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it can still be modified without the need for creative labor to the technical solutions recorded in the foregoing embodiments, or to make equivalent replacement for some of the technical features. Thus, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A kind of H bridge circuit overcurrent and short-circuit special protection device, it is characterized in that: The application relates to a direct-current motor control system H-bridge circuit overcurrent and short-circuit detection sampling resistor, a driving ICU3 for controlling the on-off of the H-bridge circuit, a current monitoring and protection unit; the driving ICU3 output control end is connected with the H-bridge circuit input control end, the driving ICU3 enable end is connected with the current monitoring and protection unit control signal output end, and the current monitoring and protection unit control signal input end is connected with the sampling resistor.

2. The overcurrent and short-circuit protection device for H-bridge circuits according to claim 1, characterized in that: The current monitoring and protection unit comprises an integrated operational amplifier U1 and a comparator U2; the integrated operational amplifier U1 same-phase input end is connected with the sampling resistor through a low-pass filter, the integrated operational amplifier U1 opposite-phase input end is connected with the integrated operational amplifier U1 output end through a high-pass filter; the integrated operational amplifier U1 output end is connected with the comparator U2 same-phase input end, the comparator U2 opposite-phase input end is connected with a working power supply through a voltage dividing circuit, and the comparator U2 output end is connected with the driving ICU3 enable end.

3. The overcurrent and short-circuit protection device for H-bridge circuits according to claim 1 or 2, characterized in that The signal input ends of the driving ICU3 are respectively connected with the logic signal output ends of a microcontroller of the direct-current motor control system; the short-circuit signal collected by the sampling resistor of the current monitoring and protection unit is connected with the external interrupt signal input end of the microcontroller of the direct-current motor control system.

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