An isolated driving circuit for a plurality of MOSFETs in parallel

Abstract

The application discloses a plurality of MOSFET parallel isolation driving circuit, characterized by: including driving transformer T1, MOSFET Q1, MOSFET Q2, the transformer T1 separates the driving ground and the power ground, and the driving circuit and the power loop are separated by the current mutual inductance, and the anti-interference ability is improved.The plurality of MOS parallel isolation driving circuit includes capacitor C1 and driving transformer T1, and the positive and negative half cycle driving signals are generated on the primary winding of T1 through capacitor C1 and driving transformer T1; the two secondary windings of the driving transformer are connected to the source and the gate of MOSFET Q1 and Q2 through driving resistors R1 and R2, respectively, and the driving circuit and the power loop are separated by the current mutual inductance, that is, the loop of driving current Ig1 and Ig2 and the loop of power current Id1 and Id2 are separated by the current mutual inductance.The application has the advantages of simple driving, good power consistency, small electromagnetic interference, easy meeting of the safety regulation isolation requirement, and convenient application in high-power expansion and multi-output occasions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronics, and particularly relates to a MOSFET parallel isolation driving circuit. BACKGROUND

[0002] Based on the MOSFET application, a low-voltage signal is used to control a high-voltage and large-current signal, and a weak electric signal is used to control a strong electric signal.

[0003] When the existing driving circuit drives a single MOSFET, it can work normally. Figure 1 As shown in the figure, the driving circuit controls the turn-on and turn-off of the MOSFET Q1 through the driving resistor R1. The driving circuit and the source of Q1 are single-point grounded at point A. The return path of the driving current Ig1 is shown in the figure, and the current passes through R1 and the source of Q1 and returns to the driving circuit from point A. The power current Id1 flowing through Q1 returns to the power circuit from point A. The driving current Ig1 and the power current Id1 return from their respective circuits, and no voltage difference is generated on the ground circuit, and the ground reference point is consistent.

[0004] When the existing driving circuit drives multiple MOSFETs in parallel, if there is a large line impedance, the turn-on of the MOSFET Q2 will be affected. As shown in the figure, Figure 2 MOSFETs Q1 and Q2 are used in parallel, and the driving resistors are R1 and R2, respectively. The power current flowing through Q1 is Id1, which returns to the power circuit from point A. The power current flowing through Q2 is Id2, which returns to the power circuit from point B through point A. Due to the non-ideal grounding between A and B, there is a line impedance Rs. The return path of the driving current Ig1 of Q1 is shown in the figure, Figure 2 The current passes through R1 and the source of Q1 and returns to the driving circuit from point A. The return path of the driving current Ig2 of Q2 is shown in the figure, and the current passes through R2 and the source of Q2 and returns to the driving circuit from point B through point A.

[0005] Due to the large power current Id2 of Q2, a voltage Us is generated on Rs. This voltage will affect the driving level Vgs2 of Q2. In severe cases, it will even affect the turn-on and turn-off of Q2. At the same time, Id2 belongs to a large power pulsating current, and a transient spike is generated on Rs, causing the gate of Q2 to fail. SUMMARY

[0006] To solve the problems in the prior art, the application provides a MOSFET parallel isolation driving circuit, which aims to solve the problem that when the driving circuit drives multiple MOSFETs, the line impedance caused by non-ideal grounding affects the turn-on and turn-off of the MOSFET, and even causes the gate to fail.

[0007] To solve the technical problems, the application provides the following technical solutions.

[0008] A plurality of MOSFET parallel isolation drive circuit, characterized by: including drive transformer T1, MOSFET Q1, MOSFET Q2, the transformer T1 will drive ground and power ground apart, through the current mutual inductance way will drive circuit and power loop independent, improve the ability of anti-interference.

[0009] Further, the plurality of MOS parallel isolation drive circuit, including capacitor C1, drive transformer T1, through capacitor C1 and drive transformer T1, on T1 primary winding produces positive and negative half cycle drive signal;Drive transformer two secondary winding, through drive resistance R1, R2 is connected to MOSFET Q1 and Q2 source and gate, the through current mutual inductance way will drive circuit and power loop independent, namely through the current mutual inductance way will drive current Ig1 and Ig2 loop and power current Id1 and Id2 loop independent.

[0010] Further, the through current mutual inductance way will drive current Ig1 and Ig2 loop and power current Id1 and Id2 loop independent, specifically: although Q1 grounding point A and Q2 grounding point B still exist impedance Rs, power current Id2 still on Rs produces voltage drop Us, because the drive circuit and power loop independent, Q1 and Q2 drive level is not affected by Q1 and Q2 power circuit, improve the parallel MOS drive anti-interference ability.

[0011] The advantages and effects of the present application

[0012] 1, the present application by changing the relative position between elements, achieved the unexpected effect: through the transformer T1 will power ground and drive ground isolation, changes the position relationship of drive current Ig1, Ig2 and power current Id1, Id2: from sharing a loop to two independent loop: from sharing a ground to two independent ground, through the above two relationship changes, improve the anti-interference ability.

[0013] 2, the present application drive simple, can control multiple output in single drive condition;Power consistency is good, electromagnetic interference is small, easy to meet the safety isolation requirements;Convenient in high power expansion and multiple output occasions application. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Prior art - single MOSFET drive circuit;

[0015] Figure 2 Prior art - multiple MOSFET drive circuit;

[0016] Figure 3The patent technology is a plurality of MOSFET parallel driving circuit. DETAILED DESCRIPTION

[0017] Design principle of the present application

[0018] 1. The design principle of isolating "drive ground" and "power ground". Since the drive currents Ig1 and Ig2 have their own independent induced power, the current comes from and returns to the induced power, so the drive ground is independent. Since the original power loop is separated from the drive circuit, only the power current Id1 and Id2 remain in the power loop, so the power ground is also independent.

[0019] 2. Comparison before and after improvement. Before improvement, as shown in Figure 2 , after improvement, as shown in Figure 3 . Before improvement, since Ig2 and Id2 share a loop, and Id2 is a strong pulsed current, the strong current Id2 generates a voltage drop Us when passing through the wire. In the loop shared by Ig2 and Id2, due to the voltage division of Us, the gate-source drive level of MOSFET Q2 is reduced from the original Vgs2 to (Vgs2-Us). The reduction of Q2 drive voltage is due to the fact that Ig2 and Id2 share a loop. After improvement, although the strong current Id2 will still generate circuit impedance Rs, since Ig2 and Id2 have been separated into two independent loops, Ig2 no longer flows through Rs, and the voltage Vgs between the gate and source of Q2 is independent of Id2. Therefore, although the circuit impedance Rs still exists, it has no effect on the voltage between the gate and source of Q2. As a result, the anti-interference ability of the MOS parallel circuit is enhanced after improvement.

[0020] Based on the above invention principle, the present application designs a plurality of MOS parallel isolation driving circuit, which is characterized by: including a driving circuit, a transformer T1, MOSFET Q1 and MOSFET Q2, the transformer T1 separates the drive ground and the power ground, and independently separates the drive circuit and the power loop through current mutual induction, thereby improving the anti-interference ability.

[0021] The plurality of MOSFET parallel power electronic driving circuit includes a capacitor C1 and a driving transformer T1. Through the capacitor C1 and the driving transformer T1, a positive and negative half-cycle drive signal is generated on the primary winding of T1. The two secondary windings of the driving transformer are connected to the source and gate of MOSFET Q1 and MOSFET Q2 through driving resistors R1 and R2, respectively. The drive circuit and the power loop are isolated through current mutual induction, that is, the drive current Ig1 and Ig2 loop and the power current Id1 and Id2 loop are independently separated through current mutual induction.

[0022] Supplementary note

[0023] 1. Figure 3 is the intercepted part of the total circuit, the total power supply is not intercepted. The total power supply is converted by the auxiliary circuit, on the one hand, to supply power to the drive circuit of Figure 3 , and on the other hand, to supply power to the main power circuit of Figure 3 .

[0024] 2. The transformer functions to make Ig2 and Id2 have their own independent induced power supply through induced current, two "independent drive grounds" are generated by the two independent induced power supplies, thereby separating the drive ground from the "common ground GND", and the original "common ground GND" is left as a "power ground" for power currents Id1 and Id2

[0025] The loop of the drive current Ig1 and Ig2 and the loop of the power current Id1 and Id2 are separated by current mutual induction, specifically: although the grounding point A of Q1 and the grounding point B of Q2 still have impedance Rs, the power current Id2 still generates a voltage drop Us on Rs, and since the drive circuit and the power loop are independent of each other, the drive level of Q1 and Q2 is not affected by the power circuit of Q1 and Q2, and the anti-interference ability of the parallel MOS is improved.

[0026] The application provides an implementation mode of two MOSFETs in parallel, and for more than two MOSFETs in parallel, the same function can be achieved by increasing the number of secondary winding of T1. The implementation principle is the same, and it also belongs to the scope of the application.

[0027] It should be emphasized that the above specific embodiments are only an explanation of the application, and are not a limitation of the application, and those skilled in the art can make modifications to the above embodiments without creative contribution after reading the specification, but as long as it is within the scope of the claims of the application, it is protected by the patent law.

Claims

1. A plurality of MOSFET parallel isolation drive circuit, characterized by: including drive transformer T1, MOSFET Q1, MOSFET Q2, the transformer T1 separates the drive ground and power ground, through the current mutual inductance way to separate the drive circuit and power loop, improve the ability of anti-interference; The plurality of MOSFET parallel isolation drive circuit, including capacitor C1, drive transformer T1, through capacitor C1 and drive transformer T1, positive and negative half cycle drive signal is generated on the primary winding of T1; the two secondary winding of drive transformer, through drive resistance R1, R2 is connected to the source and gate of MOSFET Q1 and Q2, respectively, the current mutual inductance way to separate the drive circuit and power loop, that is, through the current mutual inductance way to separate the drive current Ig1 and Ig2 loop and power current Id1 and Id2 loop; The current mutual inductance way to separate the drive current Ig1 and Ig2 loop and power current Id1 and Id2 loop, specifically: although the ground point A of Q1 and the ground point B of Q2 still exist impedance Rs, power current Id2 still produces voltage drop Us on Rs, because the drive circuit and power loop are independent, the drive level of Q1 and Q2 is not affected by the power circuit of Q1 and Q2, and the driving anti-interference ability of parallel MOSFET is improved.

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