Application in Brushless DC Motor Drive Circuit
IR's IR2110 chip is a monolithic integrated driver module for dual-channel, gate-driven, high-voltage, high-speed power devices. Due to its small size, low cost, high integration, fast response, high bias voltage and strong driving capability, this bootstrap integrated circuit for power MOSFET and IGBT drive has been adjusted since the introduction. Widely used in power drive fields such as speed and power conversion. The IR2110 uses advanced bootstrap circuitry and level shifting technology to greatly simplify the control requirements of logic devices for power devices, allowing each pair of MOSFETs (upper and lower) to share a single IR2110, and all IR2110s can share an independent power supply. For a typical 3-tube three-phase bridge inverter, three IR2110s can be used to drive three bridge arms, requiring only one 10V to 20V power supply. In this way, the volume of the drive circuit and the number of power sources are greatly reduced in engineering, the system structure is simplified, and the system reliability is improved.
1. Internal structure and functional characteristics of IR2110
When the input logic signal HIN/LIN=1, the output signal HO/LO=1, the control MOSFET is turned on; when HIN/LIN=0, HO/LO=0, the control MOSFET is turned off, and its SD input can be used to block This two-way drive. If the two driving voltages are less than 8.3V, the output signal will be blocked on-chip due to undervoltage. The output gate drive voltage ranges from 10V to 20V, and its typical level conversion time is: Ton=120ns, Toff=94ns. The typical dead time is 10ns. The built-in dead-band circuit prevents the straight-arm conduction caused by the turn-off delay of the MOS device and improves the reliability of the system.
2, brushless DC motor drive circuit
Permanent magnet brushless DC motor is a new type of motor developed with the development of high performance permanent magnet materials, motor control technology and power electronics technology. It has the advantages of simple structure, reliable operation, convenient maintenance and long life. Moreover, it has many advantages such as high operating efficiency, no excitation loss and good speed regulation performance of the DC motor, and also has the characteristics of high power density, low speed and large torque. Its application has grown rapidly from the initial military industry to aerospace, medical, information, home appliances and industrial automation.
3, the choice of bootstrap device
In the brushless DC motor power drive circuit, the three-way power tube of the lower arm is controlled by the internal MOS tube of the IR2110 chip by Vcc (+15V), and the gate drive power of the three-way power tube of the upper arm is charged and stored by the bootstrap capacitor. Realized. As shown in Figure 3, C1 and D1 are bootstrap capacitors and diodes, respectively, and C2 is a filter capacitor of Vcc. It is assumed that C1 has been charged to a sufficient voltage (Vc1Vcc) during the turn-off of Q1. When pin 10 (HIN) is high, Vc1 is applied between the gate and source of Q1, C1 is discharged through Rg1 and Q1 gate-source capacitor Cge1, and Cge1 is charged. At this time, Vc1 can be equivalent to one. power source. When pin 10 (HIN) is low, Q1 gate charge is rapidly released by Rg1, Dg1, Rx1, etc., and Q1 is turned off. After a short dead time (td), another IR2110 controls Q2 to turn on, Vcc charges C1 via D1 and Q2, and quickly replenishes energy for C1, so that the loop repeatedly implements bootstrap driving.
If C1 is slowly charged by the load, when the voltage of the bootstrap capacitor C1 is still less than 8.3V when the bootstrap voltage is above HIN=1, the output drive signal will be blocked by the on-chip logic due to undervoltage, and Q1 will not work. The choice of lifting capacitors is very important. If you choose improperly, it will cause damage to the chip or not work properly. The capacity of the bootstrap capacitor depends on the power MOSFET switching frequency being driven, the turn-on and turn-off duty cycles, and the gate charge current. Since the brushless DC motor driving circuit has a power MOSFET tube turned on at any moment of operation, and the system adopts the upper arm PWM modulation mode, the bootstrap capacitor charging time ratio in the driving circuit is provided. The driving power supply takes a long time, and the bootstrap capacitor is easy to charge, so it is possible to select a larger capacitance value. This driving circuit selects 1uF electrolytic capacitor.
The function of the diode D1 in the circuit is to prevent the excessive voltage from being reversed into the Vcc terminal when the Q1 is turned on to damage the chip. The diode D1 connected to the IR2110 power supply must have a reverse withstand voltage greater than the peak bus voltage of the driven power MOSFET. To prevent discharge at both ends of the bootstrap capacitor, the diode should use a high-frequency fast recovery diode. FR107, its maximum reverse recovery time is 500ns, the maximum reverse withstand voltage of 1000V.
The turn-on and turn-off transmission delay times of the IR2110 are basically matched, and the turn-on transmission delay time is longer than the turn-off transmission delay time by 25 ns, which ensures that the power tube of the same bridge arm does not simultaneously turn on during operation, thereby avoiding the through failure. occur. In order to further improve the safety, the power tube \ slow-on and fast-off\, the resistor Rg and the diode Dg are respectively connected in series at the gate of the power tube. The rising edge of the IR2110 drive pulse depends on Rg. The Rg value should not be too large to prevent the rising edge of the drive pulse from being steep, but it should not be too small to cause the drive current to be too large to damage the IR2110.
4 Conclusion
In this paper, the brushless DC motor power drive circuit based on the power driver chip IR2110 is designed, and the related devices are selected and designed. The circuit has the characteristics of simple structure, stability and reliability. Verification on a test prototype shows that this circuit implementation is effective and feasible.
