阅读说明：本技术 一种用于功率开关mosfet导通电流采样电路 (MOSFET (Metal-oxide-semiconductor field Effect transistor) conduction current sampling circuit for power switch ) 是由 黄胜明 李卫东 于 2020-03-23 设计创作，主要内容包括：本发明实施例提供了一种用于功率开关MOSFET导通电流采样电路,涉及电机驱动保护的技术领域。本发明实施例提供了一种用于功率开关MOSFET导通电流采样电路,电路由控制器控制第一驱动器和/或第二驱动器,包括：正转采样电路,正转驱动MOS管组,反转驱动MOS管组以及第一电容C1以及检测电阻Rsen；正转采样电路包括第五MOS管M5、第六MOS管M6以及第一监视MOS管Msen1、第一开关SW1以及第一比较器；通过上述器件及其连接方式,可以将通过检测电阻Rsen电流大幅度减小,从而减少通过检测电阻Rsen的热耗,降低了散热系统的设计难度。(The embodiment of the invention provides a MOSFET (metal oxide semiconductor field effect transistor) conduction current sampling circuit for a power switch, and relates to the technical field of motor drive protection. The embodiment of the invention provides a MOSFET (metal oxide semiconductor field effect transistor) conduction current sampling circuit for a power switch, wherein the circuit controls a first driver and/or a second driver by a controller, and the MOSFET conduction current sampling circuit comprises: the forward rotation sampling circuit is used for forward rotation driving of the MOS tube group, and reverse rotation driving of the MOS tube group, the first capacitor C1 and the detection resistor Rsen; the forward rotation sampling circuit comprises a fifth MOS transistor M5, a sixth MOS transistor M6, a first monitoring MOS transistor Msen1, a first switch SW1 and a first comparator; through the device and the connection mode thereof, the current passing through the detection resistor Rsen can be greatly reduced, so that the heat consumption passing through the detection resistor Rsen is reduced, and the design difficulty of a heat dissipation system is reduced.)

1. A MOSFET on-current sampling circuit for a motor driven power switch, said circuit having a controller controlling a first driver and/or a second driver, comprising: the forward rotation sampling circuit is used for forward rotation driving of the MOS tube group, and reverse rotation driving of the MOS tube group, the first capacitor C1 and the detection resistor Rsen;

the forward rotation sampling circuit comprises a fifth MOS transistor M5, a sixth MOS transistor M6, a first monitoring MOS transistor Msen1, a first switch SW1 and a first comparator;

the forward rotation driving MOS tube group comprises a second MOS tube M2 and a third MOS tube M3;

the reverse driving MOS tube group comprises a first MOS tube M1 and a fourth MOS tube M4;

the source of the first MOS transistor M1 is connected to the drain of the second MOS transistor M2, the source of the second MOS transistor M2 is grounded, the gate of the first MOS transistor M1 is connected to one output end of the second driver, the gate of the second MOS transistor M2 is connected to the other output end of the second driver, and the drain of the first MOS transistor M1 is connected to an external power supply;

the source of the third MOS transistor M3 is connected to the drain of the fourth MOS transistor M4, the source of the fourth MOS transistor M4 is grounded, the gate of the third MOS transistor M3 is connected to one output end of the first driver, the gate of the fourth MOS transistor M4 is connected to the other output end of the first driver, and the drain of the third MOS transistor M3 is connected to an external power supply;

the gate of the fifth MOS transistor M5 is connected to the output end of the first summer, the drain of the fifth MOS transistor M5 is connected to the external power supply through a first resistor R1, and the source of the fifth MOS transistor M5 is connected to the drain of the first monitoring MOS transistor Msen 1;

a gate of the first monitoring MOS transistor Msen1 is connected to one end of the first switch SW1 and one end of the first capacitor C1, respectively, and a source of the first monitoring MOS transistor Msen1 is connected to a non-inverting input terminal of the first comparator;

the gate of the sixth MOS transistor M6 and the drain of the sixth MOS transistor M6 are both connected to one input end of the first summer, and the source of the sixth MOS transistor M6 is connected to the source of the first MOS transistor M1 and the drain of the second MOS transistor M2, respectively;

the other end of the first capacitor C1 is respectively connected with the same-direction input end of the first comparator and the other input end of the first summator;

the output end of the first comparator is connected with the controller;

one end of the detection resistor Rsen is grounded, the other end of the detection resistor Rsen is connected with the equidirectional input end of the first comparator 1, and the reverse input end of the first comparator is connected with a reference voltage V_lim。

2. The circuit of claim 1, further comprising an inverse sampling circuit,

the inversion sampling circuit comprises a seventh MOS transistor M7, an eighth MOS transistor M8, a second monitoring MOS transistor Msen2, a second switch SW2 and a second comparator;

the gate of the seventh MOS transistor M7 is connected to the output end of the second summer, the drain of the seventh MOS transistor M7 is connected to the external power supply through a second resistor R2, and the source of the seventh MOS transistor M7 is connected to the drain of the second monitoring MOS transistor Msen 2;

a gate of the second monitoring MOS transistor Msen2 is connected to one end of the second switch SW2 and one end of the second capacitor C1, respectively, and a source of the second monitoring MOS transistor Msen2 is connected to a non-inverting input terminal of the second comparator;

the gate of the eighth MOS transistor M8 and the drain of the eighth MOS transistor M8 are both connected to one input end of the second summer, and the source of the eighth MOS transistor M8 is connected to the source of the third MOS transistor M3 and the drain of the fourth MOS transistor M4, respectively;

the other end of the second capacitor C1 is respectively connected with the non-inverting input end of the second comparator and the other input end of the second summator;

and the output end of the second comparator is connected with the controller.

3. The circuit of claim 1, wherein the first monitoring MOS transistor Msen1 and the second MOS transistor M2 have the same channel length, and the channel width of the first monitoring MOS transistor Msen1 is 1/n of that of the second MOS transistor M2.

4. The circuit of claim 2, wherein the second monitoring MOS transistor Msen2 and the fourth MOS transistor M4 have the same channel length, and the channel width of the second monitoring MOS transistor Msen2 is 1/n of that of the fourth MOS transistor M4.

Technical Field

The invention relates to the technical field of motor drive circuit protection, in particular to a MOSFET (metal oxide semiconductor field effect transistor) conduction current sampling circuit for a power switch.

Background

Dc motors are widely used in electronic devices such as printers, robots, industrial automation, and electric tools. To operate the motor, a control driver chip is applied. Fig. 1 shows a schematic diagram of a two-phase brush motor drive, where M1, M2, M11, M22 are MOSFET switches. When M22 and M1 are turned on, current flows from VDD through switch M22 from the positive pole to the negative pole of the motor, through switch M1 and current detection resistor R_SENTo the ground, the motor rotates forward(ii) a When M2 and M11 are turned on, current flows from VDD through switch M2 from the negative pole to the positive pole of the motor, through switch M11 and current sense resistor R_SENThe motor reverses direction of flow to ground.

In order to protect the motor from being shorted to supply VDD or ground, the current through the motor needs to be monitored to avoid excessive current through the motor, i.e., Over Current Protection (OCP). As shown in FIG. 1, the conventional overcurrent protection method uses an external current sensing resistor R connected between the SEN port and ground_SENTo monitor the current through the motor. The current through the motor passes through R no matter whether the current is in the forward direction or the reverse direction_SEN. The positive electrode of the over-current monitoring comparator (OCP Comp) is connected with the SEN end, and the negative electrode is connected with an over-current monitoring reference voltage V_ilim. When the current flowing through the motor is excessive, the current detection resistor R_SENThe voltage on will be higher than V_ilimAnd the output state of the overcurrent monitoring comparator is turned over, and the logic control circuit controls the driver to turn off a switch for connecting the motor to a power supply and the ground, so that the motor is protected.

Generally, for a general dc motor, the current for driving the motor is large, and can reach more than one ampere, for example, one ampere during steady operation. Since starting the motor requires a current larger than the steady operation, in order to avoid the false protection, the overcurrent protection point is usually set to be more than 2 times of the steady operation current of the motor, for example, 2.5 times, that is, the overcurrent value is set to be 2.5A. If overcurrent protection reference voltage V_ilimSet at 0.5V, the current sensing resistor Rsen needs to take a value of 0.2 ohms. While the drive current through the motor is 1A in steady operation, the power dissipation on the sensing resistor Rsen is 0.2 watts. This not only results in more energy loss, but also increases the design difficulty of heat dissipation for the system.

In summary, in the prior art, the heat loss of the detection resistor Rsen is large, which increases the difficulty of heat dissipation of the system.

Disclosure of Invention

In view of the above, an object of the present invention is to provide a MOSFET conduction current sampling circuit for a power switch, so as to reduce heat dissipation of a detection resistor Rsen and reduce difficulty in heat dissipation design of a system in the prior art.

In a first aspect, the present invention provides a MOSFET conduction current sampling circuit for a power switch, the MOSFET conduction current sampling circuit being controlled by a controller to control a first driver and/or a second driver, the MOSFET conduction current sampling circuit comprising: the forward rotation sampling circuit is used for forward rotation driving of the MOS tube group, and reverse rotation driving of the MOS tube group, the first capacitor C1 and the detection resistor Rsen;

the forward rotation sampling circuit comprises a fifth MOS transistor M5, a sixth MOS transistor M6, a first monitoring MOS transistor Msen1, a first switch SW1 and a first comparator;

the forward rotation driving MOS tube group comprises a second MOS tube M2 and a third MOS tube M3;

the reverse driving MOS tube group comprises a first MOS tube M1 and a fourth MOS tube M4;

the source of the first MOS transistor M1 is connected to the drain of the second MOS transistor M2, the source of the second MOS transistor M2 is grounded, the gate of the first MOS transistor M1 is connected to one output end of the second driver, the gate of the second MOS transistor M2 is connected to the other output end of the second driver, and the drain of the first MOS transistor M1 is connected to an external power supply;

the source of the third MOS transistor M3 is connected to the drain of the fourth MOS transistor M4, the source of the fourth MOS transistor M4 is grounded, the gate of the third MOS transistor M3 is connected to one output end of the first driver, the gate of the fourth MOS transistor M4 is connected to the other output end of the first driver, and the drain of the third MOS transistor M3 is connected to an external power supply;

the gate of the fifth MOS transistor M5 is connected to the output end of the first summer, the drain of the fifth MOS transistor M5 is connected to the external power supply through a first resistor R1, and the source of the fifth MOS transistor M5 is connected to the drain of the first monitoring MOS transistor Msen 1;

a gate of the first monitoring MOS transistor Msen1 is connected to one end of the first switch SW1 and one end of the first capacitor C1, respectively, and a source of the first monitoring MOS transistor Msen1 is connected to a non-inverting input terminal of the first comparator;

the gate of the sixth MOS transistor M6 and the drain of the sixth MOS transistor M6 are both connected to one input end of the first summer, and the source of the sixth MOS transistor M6 is connected to the source of the first MOS transistor M1 and the drain of the second MOS transistor M2, respectively;

the other end of the first capacitor C1 is respectively connected with the same-direction input end of the first comparator and the other input end of the first summator;

the output end of the first comparator is connected with the controller;

one end of the detection resistor Rsen is grounded, the other end of the detection resistor Rsen is connected with the equidirectional input end of the first comparator 1, and the reverse input end of the first comparator is connected with a reference voltage V_ilim。

Preferably, the device also comprises an inversion sampling circuit,

the inversion sampling circuit comprises a seventh MOS transistor M7, an eighth MOS transistor M8, a second monitoring MOS transistor Msen2, a second switch SW2 and a second comparator;

the gate of the seventh MOS transistor M7 is connected to the output end of the second summer, the drain of the seventh MOS transistor M7 is connected to the external power supply through a second resistor R2, and the source of the seventh MOS transistor M7 is connected to the drain of the second monitoring MOS transistor Msen 2;

a gate of the second monitoring MOS transistor Msen2 is connected to one end of the second switch SW2 and one end of the second capacitor C1, respectively, and a source of the second monitoring MOS transistor Msen2 is connected to a non-inverting input terminal of the second comparator;

the gate of the eighth MOS transistor M8 and the drain of the eighth MOS transistor M8 are both connected to one input end of the second summer, and the source of the eighth MOS transistor M8 is connected to the source of the third MOS transistor M3 and the drain of the fourth MOS transistor M4, respectively;

the other end of the second capacitor C1 is respectively connected with the non-inverting input end of the second comparator and the other input end of the second summator;

the output end of the second comparator is connected with the controller;

preferably, the first monitoring MOS transistor Msen1 and the second MOS transistor M2 have the same channel length, and the channel width of the first monitoring MOS transistor Msen1 is 1/n of the channel width of the second MOS transistor M2.

Preferably, the second monitoring MOS transistor Msen2 and the fourth MOS transistor M4 have the same channel length, and the channel width of the second monitoring MOS transistor Msen2 is 1/n of the channel width of the fourth MOS transistor M4.

The embodiment of the invention has the following beneficial effects: the embodiment of the invention provides a MOSFET (metal oxide semiconductor field effect transistor) conduction current sampling circuit for a power switch, which is used for controlling a first driver and/or a second driver by a controller and comprises: the forward rotation sampling circuit is used for forward rotation driving of the MOS tube group, and reverse rotation driving of the MOS tube group, the first capacitor C1 and the detection resistor Rsen; the forward rotation sampling circuit comprises a fifth MOS transistor M5, a sixth MOS transistor M6, a first monitoring MOS transistor Msen1, a first switch SW1 and a first comparator; through the device and the connection mode thereof, the current passing through the detection resistor Rsen can be greatly reduced, so that the heat consumption passing through the detection resistor Rsen is reduced, and the design difficulty of a heat dissipation system is reduced.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a MOSFET on-current sampling circuit for a power switch provided in the prior art;

fig. 2 is a MOSFET on-current sampling circuit for a power switch according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a forward rotation operation of a motor for a MOSFET conduction current sampling circuit of a power switch according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a motor reverse rotation operation for a MOSFET conduction current sampling circuit of a power switch according to an embodiment of the present invention.

Icon: 1 — a first comparator; 2 — second comparator.

Detailed Description

To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The current overcurrent protection method is to monitor the current through the motor with an external current sensing resistor RSEN connected between the SEN port and ground. The current through the motor passes through RSEN whether it is in the forward or reverse direction. Based on the above, the circuit for sampling the on-state current of the power switch MOSFET provided by the embodiment of the invention can reduce the power loss on the detection resistor Res and reduce the design difficulty of system heat dissipation.

For the convenience of understanding the present embodiment, a MOSFET on-current sampling circuit for a power switch disclosed in the present embodiment will be described in detail first.