Bootstrap driving and rapid turn-off method of IGBT full bridge

Abstract

The invention discloses a bootstrap driving and rapid turn-off method of an IGBT full bridge, three half-bridge modules of the IGBT full bridge simultaneously drive six bridge arms of the full bridge through a bootstrap circuit by using the same power supply VCC, so that the whole IGBT full bridge is driven, the circuit structure is simplified, electronic devices and cost are saved, and the bootstrap driving and rapid turn-off method is especially beneficial to product design when space is insufficient; the negative voltage is increased on the lower bridge arm, and the upper bridge arm is connected in parallel with the triode and the resistor on the discharge loop, so that the turn-off of the IGBT is accelerated, the condition of wrong conduction is avoided, and the short circuit caused by simultaneous conduction of the upper and lower bridge arms is prevented, thereby protecting elements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of IGBT full-bridge control, in particular to a driving and shutting method of IGBT full-bridge. BACKGROUND

[0002] IGBT full-bridge, full name IGBT three-phase inverter full-bridge, is composed of 6 IGBT tubes, two by two groups form 3 independent bridge arms, and each bridge arm is composed of an upper bridge arm and a lower bridge arm. Three-phase inverter is one of the cornerstones of modern power electronics technology. Through ingenious switching control, it can efficiently and reliably convert DC power into efficient three-phase AC power. In traditional three-phase inverter, 4 independent power supplies are needed to drive the entire IGBT full-bridge to work, of which 1 power supply drives 3 lower bridge arms, and the remaining 3 power supplies drive 3 upper bridge arms respectively. This method provides 4 independent power supplies that do not interfere with each other, and has good stability. Through the cooperation of a special driving chip, it can be used to drive a larger power (several tens to hundreds of kW) inverter circuit. However, this method occupies a large design space. When used for small power inverter, due to insufficient design space or lower cost requirements, a more simple and low-cost driving scheme needs to be designed. SUMMARY

[0003] The purpose of the present application is to provide a driving and shutting method of IGBT full-bridge, which realizes driving three-phase inverter full-bridge circuit for the demand of smaller design space and lower cost.

[0004] Technical scheme: A bootstrap driving and fast shutting method of IGBT full-bridge, three half-bridge modules of IGBT full-bridge are driven by the same power supply VCC at the same time, and the driving steps for a single half-bridge module are as follows:

[0005] S1, turn on IGBT tube Q2 for a period of time by control system and driving chip, at this time IGBT tube Q1 is in the off state, when the C and E poles of Q2 are turned on, bootstrap capacitor C1 charges through the loop of VCC-D1-R4-C1-OUT-BUS;

[0006] S2, after bootstrap capacitor C1 is fully charged, control system and driving chip turn off IGBT tube Q2 and turn on IGBT tube Q1; when Q2 is off, the existence of negative voltage-VCC makes the parasitic capacitance on the IGBT tube discharge quickly, the power supply of driving chip U2 is completely provided by bootstrap capacitor C1, Q1 off makes the reference point of bootstrap capacitor C1 become the E pole voltage OUT of Q1, the voltage difference between the two ends of bootstrap capacitor C1 is maintained near VCC, and the voltage between the two ends of fast recovery diode D1 changes to prevent reverse current flow;

[0007] ​S3, the control system and drive chip turn off IGBT tube Q1, turn on IGBT tube Q2; the triode Q3 and the resistor R1 form an additional discharge loop to quickly turn off the IGBT tube Q1, after the IGBT tube Q2 is turned on, the self-boosting capacitor C1 is charged again, the energy of the self-boosting capacitor C1 in step S2 is surplus, and Q2 is turned on for a short time to charge the self-boosting capacitor C1;

[0008] S4, repeat step S2 and step S3, and the single half-bridge module drive is completed.

[0009] Further, the capacity of the self-boosting capacitor C1 is calculated as ,

[0010] Among them: The maximum drive current of the IGBT tube, The discharge voltage allowed by the self-boosting capacitor C1, The maximum pulse width when Q2 is turned on, , The IGBT tube switching frequency is not completely equal due to the existence of dead zone.

[0011] Further, VCC, BUS- and -VDD are a group of power supplies, wherein BUS- is the reference ground of the entire power supply loop, VCC is the positive power supply, and -VDD is the negative power supply.

[0012] Further, the triode Q3 is PNP type.

[0013] Beneficial effects: the self-boosting type driving and fast turn-off method of the IGBT full-bridge of the application, through the self-boosting circuit, only the same power supply is used to drive the six bridge arms of the full-bridge, thereby driving the entire IGBT full-bridge, simplifying the circuit structure, saving electronic devices and costs, and being especially beneficial to product design when space is insufficient; the negative voltage is increased through the lower bridge arm, the triode and the resistor are connected in parallel on the discharge loop of the upper bridge arm, the IGBT is accelerated to turn off, the mis-conduction is avoided, the upper and lower bridge arms are prevented from being turned on at the same time to cause short circuit, and the elements are protected. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a driving schematic diagram of a single half-bridge module;

[0015] Figure 2 It is a whole driving schematic diagram of the IGBT full-bridge. DETAILED DESCRIPTION

[0016] The application will be further illustrated below in combination with the drawings and specific embodiments.

[0017] A self-boosting type driving and fast turn-off method of an IGBT full-bridge, in combination with the drawings and specific embodiments, Figure 1 , 2As shown, a complete IGBT full bridge consists of three half-bridge modules. All three half-bridge modules drive the three lower bridge arms simultaneously through the same power supply VCC, thus driving the entire IGBT full bridge simultaneously through the same power supply VCC.

[0018] BUS+ and BUS- are DC power supplies. For a common three-phase inverter system, their potential difference Up is approximately 540V. VCC, BUS-, and -VDD form a power supply group, where BUS- is the reference ground for the entire power supply circuit, VCC is the positive power supply, and -VDD is the negative power supply. Because the switching frequency of IGBT transistors is typically in the range of several thousand to tens of kiloHz, and the voltage difference between the left and right sides of D1 is very large when IGBT Q1 is turned on, a fast recovery diode D1, a current-limiting resistor R4, and a Zener diode D2 are selected. The current-limiting resistor and its value depend on the capacitance of the bootstrap capacitor C1 and the switching frequencies of Q1 and Q2. The Zener diode D2 depends on the voltage value of VCC; generally, a Zener diode with a voltage regulation value slightly higher than VCC is selected to protect the bootstrap capacitor C1 and the driver chip U1. C3, C4, C5, and C6 are the power supply filter capacitors for the driver chip.

[0019] The driving steps for a single half-bridge module are as follows:

[0020] S1. The control system and driver chip turn on IGBT Q2 for a period of time. At this time, IGBT Q1 is in the off state. When the collector and emitter of Q2 are turned on, the bootstrap capacitor C1 is charged through the loop VCC-D1-R4-C1-OUT-BUS-.

[0021] After the bootstrap capacitor C1 is fully charged, the control system and driver chip turn off IGBT Q2 and turn on IGBT Q1. When Q2 is off, due to the presence of the negative voltage -VCC, the parasitic capacitance on the IGBT... To accelerate discharge, a negative voltage is applied to Q2 to speed up the IGBT turn-off. Meanwhile, for the driver chip U2, power is entirely supplied by the bootstrap capacitor C1. Since Q1 is off at this time, the reference point of the bootstrap capacitor C1 becomes the emitter voltage (OUT) of Q1. That is, the reference point of the bootstrap capacitor C1 changes, but the voltage across it cannot change abruptly; the voltage difference remains near VCC. The voltage change across the fast recovery diode D1 prevents reverse current flow.

[0022] S3, the control system and the drive chip turn off the IGBT tube Q1, and turn on the IGBT tube Q2, in the process, due to the limitation of the bootstrap capacitor C1, a negative voltage similar to-VDD cannot be formed to quickly turn off the IGBT tube, therefore, an additional discharge loop is formed by the PNP type triode Q3 and the resistor R1 to quickly turn off the IGBT tube Q1. After the IGBT tube Q2 is turned on, the bootstrap capacitor C1 is charged again, and the energy of the bootstrap capacitor C1 is not completely consumed in step S2, and there is still a margin, so that the Q2 is not needed to be turned on for a long time to charge the bootstrap capacitor C1, and the charging can be completed in a short time.

[0023] S4, repeat steps S2 and S3, and the single half-bridge module drive is completed.

[0024] The capacity of the bootstrap capacitor C1 needs to be calculated, ,

[0025] Wherein: The maximum drive current of the IGBT tube, The discharge voltage allowed by the bootstrap capacitor C1, The maximum pulse width when Q2 is turned on, , The IGBT tube switching frequency is not completely equal due to the existence of the dead zone.

[0026] The application changes the originally required four independent power supplies into one power supply, and drives the three lower bridge arms of the three half-bridge modules through the bootstrap type boost circuit by the single power supply, and charges the bootstrap capacitor of the upper bridge arm through the lower bridge arm when the lower bridge arm is turned on, and supplies power to the upper bridge arm by the bootstrap capacitor when the upper bridge arm needs to be turned on. One power supply can drive the whole IGBT full-bridge, simplifies the circuit structure, saves electronic devices and cost, and is especially beneficial to product design when the space is insufficient.

[0027] In order to protect the IGBT tube and avoid the simultaneous conduction of the upper and lower bridge arms, the IGBT tube needs to be quickly turned off. For a single IGBT tube, a negative voltage is provided by a voltage stabilizing tube to make the IGBT tube have a larger pressure difference when turned off, so that the IGBT tube can be quickly turned off, but the bootstrap type boost cannot provide a negative voltage relative to the traditional isolated power supply, because the voltage charged by the bootstrap capacitor is only a positive voltage, which will cause the IGBT to be turned off for a longer time, therefore, a negative voltage is adopted on the lower bridge arm, and a PNP type triode and a resistor are connected in parallel on the drive circuit on the upper bridge arm, an additional discharge loop is provided to accelerate the IGBT turn-off when turned off, to avoid the mis-conduction, to prevent the simultaneous conduction of the upper and lower bridge arms and short circuit, thereby protecting the elements.

Claims

1. A bootstrap driving and fast turn-off method for an IGBT full-bridge, characterized in that: The three half-bridge modules of the IGBT full-bridge are all driven simultaneously by the same power supply VCC, which drives the three lower bridge arms of the three half-bridge modules. The driving steps for a single half-bridge module are as follows: S1. The control system and driver chip turn on IGBT Q2 for a period of time. At this time, IGBT Q1 is in the off state. When the collector and emitter of Q2 are turned on, the bootstrap capacitor C1 is charged through the loop VCC-D1-R4-C1-OUT-BUS-. S2. After the bootstrap capacitor C1 is fully charged, the control system and driver chip turn off IGBT Q2 and turn on IGBT Q1. When Q2 is off, the presence of the negative voltage -VCC causes the parasitic capacitance on the IGBT to... Accelerated discharge: The power supply of the driver chip U2 is entirely provided by the bootstrap capacitor C1. When Q1 is turned off, the reference point of the bootstrap capacitor C1 becomes the emitter voltage OUT of Q1. The voltage difference across the bootstrap capacitor C1 is maintained near VCC. The voltage change across the fast recovery diode D1 prevents the current from flowing in reverse. S3. The control system and driver chip turn off IGBT Q1 and turn on IGBT Q2. Transistor Q3 and resistor R1 form an additional discharge circuit to quickly turn off IGBT Q1. After IGBT Q2 is turned on, it charges the bootstrap capacitor C1 again. In step S2, the bootstrap capacitor C1 has sufficient energy, so Q2 is turned on for a short time to charge the bootstrap capacitor C1. S4. Repeat steps S2 and S3 to complete the driving of a single half-bridge module.

2. The bootstrap driving and fast shutdown method for an IGBT full-bridge according to claim 1, characterized in that: The capacitance of the bootstrap capacitor C1 is calculated as follows: , in: This is the maximum drive current of the IGBT transistor. This is the allowable discharge voltage of the bootstrap capacitor C1. This is the maximum pulse width when Q2 is enabled. , The switching frequency of the IGBT is not exactly the same due to the existence of the dead time.

3. The bootstrap driving and fast shutdown method for an IGBT full-bridge according to claim 1, characterized in that: VCC, BUS-, and -VDD form a power supply group, where BUS- is the reference ground for the entire power supply loop, VCC is the positive power supply, and -VDD is the negative power supply.

4. The bootstrap driving and fast shutdown method for an IGBT full-bridge according to claim 1, characterized in that: Transistor Q3 is a PNP type.

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