Coil-driven overcurrent protection circuit and method

Abstract

The invention relates to a coil drive over-current protection circuit and method, and belongs to the technical field of over-current protection, and the coil drive over-current protection circuit comprises a voltage amplification circuit, a drive tube grid drive, a voltage comparison circuit and a coil drive circuit. Wherein M1 and M2 in the coil driving circuit are in a proportional relation, and currents I4 and I5 flowing through the M1 and the M2 are in a proportional relation; the triodes Q1 and Q2 form a common-base voltage amplifier circuit and output differential voltages V1 and V2; the output of the common-base voltage amplifier is connected with the input of the voltage comparison circuit; when V2 is greater than V2, the comparator outputs a logic signal FLAG to overturn; and when the V1-V2 is greater than the threshold voltage VTH of the M15, the current generated by the M15 is amplified by N times on the M29 through the M28, and is amplified by M times on the M27 through the M26 to discharge the grid electrodes of the M1 and the M2, so that the driving current is reduced, and the whole system is prevented from being damaged. According to the invention, coil driving overcurrent can be protected in time.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of overcurrent protection, and particularly relates to a coil driving overcurrent protection circuit and a coil driving overcurrent protection method. BACKGROUND

[0002] There are a large number of coil driving devices in modern life, such as relays, electromagnetic valves, etc. In a coil driving system, the working environment of the system is complex and changeable. In order to protect the entire system, the coil driving circuit applies various protection measures, such as overvoltage, overtemperature, overcurrent, short circuit, open circuit, etc. For example, the change of temperature is a gradual process, so the overtemperature protection processing can not need to be too fast. The change of current is fast, and the device current is large, so many adverse consequences may occur if there is no timely protection, such as burning out the winding of the coil, damaging the driving circuit, etc., so the speed requirement of overcurrent protection is high, and the device driving the coil needs to be turned off in a very short time.

[0003] At present, the overcurrent protection of the driving coil usually connects a small resistance as a current sensor in series between the driving tube and the ground. When the driving current flows through the resistance, a sampling voltage is generated, and the sampling voltage is compared with a reference voltage. When the sampling voltage exceeds the reference voltage, the circuit makes a corresponding processing. If the voltage on the current sensor resistance is too large, it will reduce the voltage applied to the coil, so in order to avoid reducing the efficiency of the coil driving, the voltage on the current sensor resistance is generally low, and the voltage is too low, which makes it difficult for the circuit to identify the subsequent processing, so the sampling voltage needs to be amplified during processing. Since the sampling voltage needs to be amplified by an operational amplifier, and then converted into a digital signal by an ADC converter, and then compared with a set value, or the amplified signal is compared with a set analog level, and then controlled after multiple comparisons, the reaction is slow, which is difficult to meet the protection requirements of the driving coil. SUMMARY

[0004] The technical scheme is as follows: The present application aims at the problems in the prior art, and provides a coil driving overcurrent protection circuit and a coil driving overcurrent protection method using the circuit, which has the advantages of actively discharging the coil driving tube gate and having little effect on the coil driving efficiency compared with directly connecting a current sampling resistance.

[0005] The technical scheme is as follows: A coil drive overcurrent protection circuit includes a voltage amplifier 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, thus acting as the driving transistors. MOSFETs M3, M4, M5, and M21 form a bias circuit, and transistors Q1 and Q2 form a common bias circuit. The common-base voltage amplifier circuit outputs differential voltages V1 and V2. The output of the voltage amplifier circuit is connected to the input of a voltage comparator circuit. When V1 > V2, the drive current reaches a 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 difference between V1 and V2 exceeds the threshold voltage V of M15... TH At this time, M26, M27, M28, and M29 amplify the current generated by M15 by a certain factor, discharge the gates of the coil drive transistors M1 and M2, reduce the drive current, and prevent damage to the entire system.

[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] Further, when the value of V1 - V2 is greater than the threshold voltage VTH of M15, the transconductance amplifier M15 generates a current I1. The current I1 flows through M26 via the current I2 generated by the mirror M29 of M28. The mirror M27 of M26 generates a current I3 to discharge the gates of the coil driving transistors M1 and M2, reducing their gate voltages to decrease the driving current. Among them, M28 and M29 are P-channel MOS transistors, and M15, M26, and M27 are N-channel MOS transistors. 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] A method for overcurrent protection of coil driving uses the above-mentioned coil driving overcurrent protection circuit and performs the following steps: Step S1: Determine the ratio of M1 to M2 respectively so that I4 and I5 are in a proportional relationship, determine the ratio of M29 to M28 so that I1 is amplified to I2, and determine the ratio of M27 to M26 so that I2 is amplified to I3; Step S2: As I4 gradually increases, the Vsensor voltage increases, and the magnitudes of V1 and V2 also change. Vsensor = I4 * Rsensor. When Vsensor < V T lnN, V1 < V2. When Vsensor > V T lnN, V1 > V2. When I4 > V T *lnN / Rsensor, the FLAG is inverted; Step S3: According to the inverted FLAG signal, it can be determined that the driving current has reached the set overcurrent value; Step S4: After Step S2, as I4 continues to increase, V1 further increases, and V2 will rapidly decrease. When the value of V1 - V2 is greater than the threshold voltage V TH of M15, the transconductance amplifier M15 conducts to generate a current I1; Step S5: The current I1 is amplified N times on M29 through M28, becoming the current I2, and then amplified M times on M27 through M26, becoming the current I3. That is, I3 is amplified N * M times relative to I1; Step S6: I3 discharges the gates of the coil driving transistors M1 and M2, reducing the gate voltages of the driving transistors and decreasing the driving current to avoid damage to the entire system.

[0011] Beneficial effects: 1) The present invention performs overcurrent protection by sampling the proportional current of the drive through a sampling resistor, without affecting the drive efficiency and with high overcurrent protection current accuracy.

[0012] 2) The sampling resistor can be selected to be of the order of ohms. Compared with the prior art, such a resistor is easier to integrate with less error.

[0013] 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.

[0014] 4) The circuit is simple, occupies a small chip area, and can reduce the cost of the chip. Attached Figure Description

[0015] Figure 1 This is the logic circuit diagram of the coil drive overcurrent protection circuit of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit it. Terms such as "upper," "lower," "front," "rear," "left," "right," "bottom," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the purpose of describing the invention. 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 invention.

[0017] like Figure 1 The 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 this time, M26, M27, M28, and M29 amplify the current generated by the transconductance amplifier M15 by a certain factor, discharge the gates of the coil drive transistors M1 and M2, reduce the drive current, and prevent damage to the entire system.

[0018] Q1 and Q2 are NPN-type triodes, M1, M2, M3, M4, M5, M14, M15, M26, and M27 are N-channel MOS transistors, M20, M21, M22, M28, and M29 are P-channel MOS transistors. M20 and M22 are the loads of Q1 and Q2 respectively; M14 provides current for the bases of Q1 and Q2, M3 provides a bias voltage for the bases of Q1 and Q2, and the common-base voltage amplifier composed of Q1 and Q2 outputs differential voltages V1 and V2.

[0019] Rsensor is a metal resistor with a resistance value ranging from 2 to 3 ohms.

[0020] Vsensor = Rsensor * I4. When I4 > V T *lnN / Rsensor, the drive current reaches the set overcurrent protection current value, which is equal to the sum of I4 multiplied by the ratio of M1 and M2 plus 1. FLAG is reversed, and the logic circuit makes corresponding processing, where V T is the thermal voltage, V T = kT / q, where k is the Boltzmann constant (1.38 * 10^-23 J / K), T is the absolute temperature, q is the charge of an electron (1.6 * 10^-19 C), and V T *lnN is the difference in V BE between two transistors at different current densities, and N is the ratio of Q1 and Q2.

[0021] When the value of V1 - V2 is greater than the threshold voltage V TH of M15, the transconductance amplifier M15 generates a current I1. The current I1 passes through the mirror M29 of M28, and the generated current I2 flows through M26. The mirror M27 of M26 generates a current I3 to discharge the gates of the coil drive transistors M1 and M2, reducing their gate voltages to decrease the drive current; where M28 and M29 are P-channel MOS transistors, M15, M26, and M27 are N-channel MOS transistors, 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.

[0022] A method for coil drive overcurrent protection uses the above coil drive overcurrent protection circuit and performs the following steps: Step S1: Determine the ratio of M1 to M2 respectively so that I4 and I5 are in a proportional relationship, determine the ratio of M29 to M28 so that I1 is amplified into I2, and determine the ratio of M27 to M26 so that I2 is amplified into I3; Step S2: I4 gradually increases, making the Vsensor voltage increase, and the magnitudes of V1 and V2 also change. Vsensor = I4 * Rsensor. When Vsensor < V T lnN, V1 < V2. When Vsensor > VT When lnN, V1>V2, I4>V T *lnN / Rsensor, FLAG flips; Step S3: Based on the flipped FLAG signal, it can be determined that the drive current has reached the set overcurrent value; Step S4: After step S2, I4 continues to increase, V1 further increases, and V2 will rapidly decrease. When the value of V1-V2 is greater than the threshold voltage V of M15... TH When the transconductance amplifier M15 is turned on, it generates a current I1; Step S5: Current I1 is amplified by N times through M28 and M29 to become current I2, and then amplified by M times through M26 and M27 to become current I3. That is, I3 is amplified by N*M times relative to I1. Step S6: I3 discharges the gates of coil drive transistors M1 and M2 to reduce the gate voltage of the drive transistors, reduce the drive current, and prevent damage to the entire system.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the principles and spirit of the present invention should be included within the protection scope of the present invention.

Claims

1. A circuit for coil-driven overcurrent protection, 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 comprises 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 acts as 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 voltage amplifier circuit is connected to the input of the voltage comparator circuit. When V1 > V2, the driving current reaches the set overcurrent value, the voltage comparator outputs the logic signal FLAG, which flips, and the logic circuit performs the 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 N times through M28 and M29, and then amplified M times through M26 and M27, which discharges the gates of the coil drive transistors M1 and M2, thereby reducing the drive current and preventing damage to the entire system.

2. The circuit for coil-driven overcurrent protection 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 circuit for coil-driven overcurrent protection 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 circuit for coil-driven overcurrent protection 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 value, which is equal to I4 multiplied by the ratio of M1 and M2 plus 1. The voltage comparator output logic signal FLAG flips, and the logic circuit performs 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 circuit for coil-driven overcurrent protection 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, M15, acting as a transconductance amplifier, generates current I1. I1 flows through M26 via current I2 generated by M29, the mirror of M28. M27, the mirror of M26, generates current I3 to discharge the gates of coil drive transistors M1 and M2, reducing their gate voltage and thus decreasing 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 based on the ratio of M28 and M29, and I3 is obtained by amplifying I2 based on the ratio of M26 and M27.

6. A method for coil-driven overcurrent protection, characterized in that: The circuit employs a coil-driven overcurrent protection as described in any one of claims 1 to 5 and performs the following steps: Step S1: Determine the ratio of M1 to M2 so that I4 and I5 are proportional; determine the ratio of M29 to M28 so that I1 is enlarged to I2; determine the ratio of M27 to M26 so that I2 is enlarged to I3. Step S2: I4 gradually increases, causing the Vsensor voltage to increase. The magnitudes of V1 and V2 also change. Vsensor = I4 * Rsensor. When Vsensor < V T lnN, V1 < V2. When Vsensor > V T lnN, V1 > V2. I4 > V T *lnN / Rsensor, and FLAG is inverted; Step S3: Based on the reversed FLAG signal, it can be determined that the drive current has reached the set overcurrent limit; Step S4: After step S2, I4 continues to increase, V1 further increases, and V2 will rapidly decrease. When the difference between V1 and V2 exceeds the threshold voltage V of M15... TH When M15 is turned on, it generates current I1; Step S5: Current I1 is amplified by N times through M28 and M29 to become current I2, and then amplified by M times through M26 and M27 to become current I3. That is, I3 is amplified by N*M times relative to I1. Step S6: I3 discharges the gates of coil drive transistors M1 and M2 to reduce the gate voltage of the drive transistors, reduce the drive current, and prevent damage to the entire system.

Images