A coil drive overcurrent protection circuit

Abstract

The utility model relates to a kind of coil drive overcurrent protection circuit, belong to overcurrent protection technical field, including voltage amplifier circuit, drive tube gate drive, voltage comparison circuit and coil drive circuit;Wherein M1 and M2 in coil drive circuit are proportional relationship, and the current I4 and I5 that both flow are proportional relationship;Triode Q1 and Q2 constitute common-base voltage amplifier circuit, output differential voltage V1 and V2;The output of common-base voltage amplifier connects the input of voltage comparison circuit, when V1>V2, comparator flips to outside output logic signal FLAG;When V1-V2 is greater than the threshold voltage V of M15 TH When, the current generated by M15 is amplified on M29 after passing M28, and then amplified on M27 again after passing M26, discharges the gate of coil drive tube M1 and M2, so that the drive current is reduced.The utility model can protect the coil drive overcurrent in time, avoid the damage of entire system.

Description

Technical Field

[0001] This utility model belongs to the field of overcurrent protection technology, specifically relating to a coil-driven overcurrent protection circuit. Background Technology

[0002] In modern life, there are numerous coil-driven devices, such as relays and solenoid valves. In coil-driven systems, the operating environment is complex and variable. To protect the entire system, coil drive circuits employ various protection measures, such as overvoltage, overtemperature, overcurrent, short circuit, and open circuit protection. For example, temperature changes are gradual, so overtemperature protection doesn't need to be too rapid; however, current changes rapidly, and the device current is often large. Failure to provide timely protection can lead to adverse consequences, such as burning out the coil windings or damaging the drive circuit. Therefore, overcurrent protection requires high speed, needing to shut down the device driving the coil within a very short time.

[0003] Currently, overcurrent protection for drive coils typically involves connecting a small resistor in series between the drive transistor and ground as a current sensor. When the drive current flows through the resistor, a sampling voltage is generated. This sampling voltage is compared to a reference voltage, and the circuit takes appropriate action when the sampling voltage exceeds the reference voltage. If the voltage across the current sensor resistor is too high, the voltage applied to the coil will decrease. Therefore, to avoid reducing the efficiency of the coil drive, the voltage across the current sensor resistor is generally quite low. However, a low voltage makes it difficult for subsequent circuit processing to identify the signal, requiring amplification of the sampling voltage. This involves multiple comparisons, such as amplifying the sampling voltage through an operational amplifier, converting it into a digital signal via an ADC converter, and comparing it with a set value, or comparing the amplified signal with a set analog level. This results in a slow response, making it difficult to meet the protection requirements for the drive coil. Utility Model Content

[0004] The technical solution is as follows: The purpose of this invention is to address the problems existing in the prior art by providing a coil drive overcurrent protection circuit, which has the advantages of actively discharging the gate of the coil drive transistor and having little impact on the coil drive efficiency compared to directly connecting the current sampling resistor in series.

[0005] The technical solution is as follows: A coil drive overcurrent protection circuit includes a voltage amplification circuit, a gate drive for driving transistors, a voltage comparator circuit, and a coil drive circuit. The coil drive circuit includes MOSFETs M1 and M2 and a resistor Rsensor. M1 and M2 are proportionally related, and the currents I4 and I5 flowing through them are also proportionally related. Current I4 flows through Rsensor to generate Vsensor. The drains of M1 and M2 are connected to the coil, which serves as the driving transistor. MOSFETs M3, M4, M5, and M21 form a bias circuit, and transistors Q1 and Q2 form a common bias circuit. The base voltage amplifier circuit outputs differential voltages V1 and V2. The output of the common-base voltage amplifier is the input of a voltage comparator. When V1 > V2, the drive current reaches the set overcurrent value, the voltage comparator output logic signal FLAG flips, and the logic circuit performs corresponding processing. MOSFET M15 is a transconductance amplifier that converts the output voltage of the common-base voltage amplifier into current. MOSFETs M26, M27, M28, and M29 amplify the current generated by M15. When the value of V1 - V2 is greater than the threshold voltage V of M15... TH At this time, the current generated by M15 is amplified by M28 and then by M29, and then by M26 and then by M27, which discharges the gates of the coil drive transistors M1 and M2, thereby reducing the drive current.

[0006] Furthermore, Q1 and Q2 are NPN transistors, M1, M2, M3, M4, M5, M14, M15, M26, and M27 are N-channel MOSFETs, and M20, M21, M22, M28, and M29 are P-channel MOSFETs. M20 and M22 are the loads of Q1 and Q2, respectively. M14 provides current to the bases of Q1 and Q2, and M3 provides bias voltage to the bases of Q1 and Q2. The common-base voltage amplifier composed of Q1 and Q2 outputs differential voltages V1 and V2.

[0007] Furthermore, Rsensor is a metallic resistor with a resistance range of 2-3 ohms.

[0008] Furthermore, Vsensor = Rsensor * I4, I4 = Vsensor / Rsensor, when I4 > Vsensor T When *lnN / Rsensor is applied, the drive current reaches the set overcurrent protection current value, which is equal to I4 multiplied by the ratio of M1 and M2 plus 1. The FLAG indicator is reversed, and the logic circuit performs corresponding processing, where V... T It is thermal voltage, V T =kT / q, where k is Boltzmann's constant (1.38*10-23 J / K), T is the absolute temperature, q is the charge of the electron (1.6*10-19 C), and V T *lnN represents the voltage (V) of the two transistors at different current densities. BE The difference, N is the ratio of Q1 to Q2.

[0009] Furthermore, when the value of V1-V2 is greater than the threshold voltage VTH of M15, the transconductance amplifier M15 generates a current I1. I1, through the current I2 generated by the mirror of M28 M29, flows through M26. The mirror of M26 M27 generates a current I3 to discharge the gates of the coil drive transistors M1 and M2, reducing their gate voltage and thus reducing the drive current. Among them, M28 and M29 are P-channel MOSFETs, and M15, M26, and M27 are N-channel MOSFETs. I2 is obtained by amplifying I1 according to the ratio of M28 and M29, and I3 is obtained by amplifying I2 according to the ratio of M26 and M27.

[0010] Beneficial effects: 1) This utility model uses the proportional current driven by the sampling resistor for overcurrent protection, which does not affect the driving efficiency and has high accuracy of overcurrent protection current.

[0011] 2) The sampling resistor can be selected in the ohm range. Compared with existing technologies, such resistors are easier to integrate and have smaller errors.

[0012] 3) Actively discharging the gate of the drive transistor through the circuit can more effectively protect the system and prevent damage to the entire system.

[0013] 4) The circuit is simple, occupies a small chip area, and can reduce the cost of the chip. Attached Figure Description

[0014] Figure 1 This is the logic circuit diagram of the coil drive overcurrent protection circuit of this utility model. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this utility model clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit it. Terms such as "upper," "lower," "front," "rear," "left," "right," "bottom," "inner," and "outer," indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the utility model. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the utility model.

[0016] like Figure 1The circuit shown is a coil drive overcurrent protection circuit, including a voltage amplifier circuit, a gate drive for the driving transistors, a voltage comparator circuit, and a coil drive circuit. The coil drive circuit includes MOSFETs M1 and M2 and a resistor Rsensor. M1 and M2 are proportional, and the currents I4 and I5 flowing through them are also proportional. Current I4 flows through Rsensor to generate Vsensor. The drains of M1 and M2 are connected to the coil, thus acting as the driving transistors. MOSFETs M3, M4, M5, and M21 form a bias circuit, and transistors Q1 and Q2 form a bias circuit. The common-base voltage amplifier circuit outputs differential voltages V1 and V2. The output of the common-base voltage amplifier circuit is connected to a voltage comparator circuit. When V1 > V2, the drive current reaches the set overcurrent protection current value, the comparator output logic signal FLAG flips, and the logic circuit performs corresponding processing. MOSFET M15 is a transconductance amplifier that converts the output voltage of the common-base voltage amplifier into current. MOSFETs M26, M27, M28, and M29 amplify the current generated by M15. When the value of V1 - V2 is greater than the threshold voltage V of M15... TH At that time, M26, M27, M28, and M29 undergo two stages of amplification, amplifying the current generated by the transconductance amplifier M15 by a certain factor, discharging the gates of the coil drive transistors M1 and M2, reducing the drive current, and preventing damage to the entire system.

[0017] Q1 and Q2 are NPN transistors; M1, M2, M3, M4, M5, M14, M15, M26, and M27 are N-channel MOSFETs; M20, M21, M22, M28, and M29 are P-channel MOSFETs. M20 and M22 are the loads of Q1 and Q2, respectively. M14 provides current to the bases of Q1 and Q2, and M3 provides bias voltage to the bases of Q1 and Q2. The common-base voltage amplifier composed of Q1 and Q2 outputs differential voltages V1 and V2. Rsensor is a metallic resistor with a resistance range of 2-3 ohms. Vsensor = Rsensor * I4, when I4 > V... T When *lnN / Rsensor is applied, the drive current reaches the set overcurrent protection current value, which is equal to I4 multiplied by the ratio of M1 and M2 plus 1. The FLAG indicator flips, and the logic circuit performs the corresponding processing. Where V... T It is thermal voltage, V T =kT / q, where k is Boltzmann's constant (1.38*10-23 J / K), T is the absolute temperature, and q is the charge of the electron (1.6*10-19 C). V T *lnN represents the voltage (V) of the two transistors at different current densities. BE The difference, N, is the ratio of Q1 to Q2. The value of V1-V2 is greater than the threshold voltage V of M15. THAt this time, the transconductance amplifier M15 generates a current I1. I1 passes through the mirror of M28, M29, which generates a current I2 that flows through M26. The mirror of M26, M27, generates a current I3 that discharges the gates of the coil drive transistors M1 and M2, reducing their gate voltage and thus reducing the drive current. M28 and M29 are P-channel MOSFETs, while M15, M26, and M27 are N-channel MOSFETs. I2 is obtained by amplifying I1 according to the ratio of M28 and M29, and I3 is obtained by amplifying I2 according to the ratio of M26 and M27.

[0018] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the principles and spirit of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A coil-driven overcurrent protection circuit, characterized in that: The circuit includes a voltage amplifier circuit, a gate drive for the driving transistors, a voltage comparator circuit, and a coil drive circuit. The coil drive circuit includes MOSFETs M1 and M2 and a resistor Rsensor. M1 and M2 are proportional, and the currents I4 and I5 flowing through them are also proportional. Current I4 flows through Rsensor to generate Vsensor. The drains of M1 and M2 are connected to the coil, which is the driving transistor. MOSFETs M3, M4, M5, and M21 form a bias circuit, and transistors Q1 and Q2 form a common-base voltage amplifier circuit, outputting differential voltages V1 and V2. The output of the common-base voltage amplifier is the input of the voltage comparator. When V1 > V2, the driving current reaches the set overcurrent value, the voltage comparator output logic signal FLAG flips, and the logic circuit performs corresponding processing. MOSFET M15 is a transconductance amplifier that converts the output voltage of the common-base voltage amplifier into current. MOSFETs M26, M27, M28, and M29 amplify the current generated by M15. When the value of V1-V2 is greater than the threshold voltage V of M15 TH At this time, the current generated by M15 is amplified by M28 and then by M29, and then by M26 and then by M27, which discharges the gates of the coil drive transistors M1 and M2, thereby reducing the drive current.

2. The coil drive overcurrent protection circuit as described in claim 1, characterized in that: Q1 and Q2 are NPN transistors, M1, M2, M3, M4, M5, M14, M15, M26, and M27 are N-channel MOSFETs, and M20, M21, M22, M28, and M29 are P-channel MOSFETs. M20 and M22 are the loads of Q1 and Q2, respectively. M14 provides current to the base of Q1 and Q2, and M3 provides bias voltage to the base of Q1 and Q2. The common-base voltage amplifier composed of Q1 and Q2 outputs differential voltages V1 and V2.

3. The coil drive overcurrent protection circuit as described in claim 1, characterized in that: The Rsensor mentioned is a metal resistor with a resistance range of 2-3 ohms.

4. The coil drive overcurrent protection circuit as described in claim 1, characterized in that: The Vsensor=Rsensor*I4, I4=Vsensor / Rsensor, when I4>V T When *lnN / Rsensor is applied, the drive current reaches the set overcurrent protection current, which is equal to I4 multiplied by the ratio of M1 and M2 plus 1. The output V1 of the common-base voltage amplifier exceeds V2, the output FLAG of the voltage comparator is inverted, and the logic circuit performs the corresponding processing; where V... T It is thermal voltage, V T =kT / q, where k is Boltzmann's constant, T is the absolute temperature, q is the charge of the electron, and V is the absolute temperature. T *lnN represents the voltage (V) of the two transistors at different current densities. BE The difference, N is the ratio of Q1 to Q2.

5. The coil drive overcurrent protection circuit as described in claim 1, characterized in that: The difference between V1 and V2 is greater than the threshold voltage V of M15. TH At this time, the current I1 generated by the transconductance amplifier M15 flows through the current I2 generated by the mirror of M28 M29 to M26. The mirror of M26 M27 generates a current I3 to discharge the gates of the coil drive transistors M1 and M2, reducing their gate voltage and thus reducing the drive current. Among them, M28 and M29 are P-channel MOSFETs, and M15, M26 and M27 are N-channel MOSFETs. I2 is obtained by amplifying I1 according to the ratio of M28 and M29, and I3 is obtained by amplifying I2 according to the ratio of M26 and M27.

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