AnalogPower无刷电机MOSFET设计指南.pdf
需积分: 5 59 浏览量
2022-08-09
09:50:44
上传
评论
收藏 339KB PDF 举报
AN2016-3
Analog Power USA Applications Department
Brushless DC Motor Control Using Surface Mount MOSFETs
Brushless DC Motors typically require six MOSFETs for the power switching and yet have significant size
constraints for the electronics. However a new generation of MOSFETs and surface mount packages provide
extremely low RDS in small packages, allowing the miniaturization of motor drive circuits and elimination of
heatsinks. In this design example we will make an 18V 10A speed control using a Microchip MIC4607-1 MOSFET
driver. This driver is rated at 85V maximum allowing this design to be adapted for use up to 60V operating voltage.
The basic powertrain circuit is shown in Figure 1. N-Channel MOSFETs are used for both high side and low side
due to the lower RDS and the availability of driver ICs to drive them. The low side FETs provide speed control
PWM, and the upper FETs are used for commutation steering. During the PWM off-time, the current freewheels
through the applicable off MOSFET’s diode. This plus the high inductances found in motors results in diode
reverse recovery when the bottom FET turns on for the next PWM on-period which can create electrical noise.
Figure 1. Three phase motor drive circuit showing diode conduction and recovery during PWM
The use of the diodes and their reverse recovery means that the gate drive of the top and bottom MOSFETs needs
careful consideration. The top MOSFETs are used for steering/commutation only and therefore have a switching
frequency an order of magnitude or more lower than the PWM low side MOSFETs. This means that at first pass,
the top MOSFETs could tolerate higher gate series resistance, but these MOSFETs also see high dv/dt as the
diode recovers. This dv/dt can turn on the MOSFET, increase losses dramatically and even cause device failures,
so it should be minimized as much as possible. A simple answer is to insert a significant resistance in series with
the bootstrap capacitor so it provides a slower turn on and yet it does not hinder a fast turn off and a strong Gate-
Source clamp to ensure the MOSFET stays off. No such flexibility is available for the low side FETs as the gate
drive voltage is not typically available phase by phase. A series resistance is the only simple variable and its value
has to be a compromise between ensuring soft turn on, limiting the reverse recovery current in the top MOSFETs
and providing good off-state pull down. However the addition of a diode and extra resistor allows tailoring of turn on
and turn off speeds separately.
The periods of diode conduction and hence recovery are not always obvious and therefore we will look at them and
the appropriate gate drive one by one. The most obvious case is the PWM of the low side switch. During the power
stroke, Q1 and Q4 are on. During the PWM freewheel period the inductive-driven current flows through D3. Then
for the next power stroke Q4 turns on and commutates D3. Q3/D3 is therefore subject to reverse recovery current
阿菠萝仔
- 粉丝: 1
- 资源: 6
最新资源
- 7777端口抓包数据集
- IMG_0694.GIF
- 基于图像的三维模型重建C++源代码+文档说明(高分课程设计)
- 基于聚焦法的工件立体测量方案，根据数据进行三维重建 使用HALCON处理图像，MATLAB拟合数据+源代码+数据集+效果图
- 锄战三国村 修改：货币使用不减 v1.10(2) 原创 (中文）.apk
- 基于python实现的单目双目视觉三维重建+源代码+图像图片(高分课程设计)
- 基于C+++OPENCV的全景图像拼接源码(课程设计)
- 基于Python+OpenCV对多张图片进行全景图像拼接，消除鬼影，消除裂缝+源代码+文档说明+界面截图(高分课程设计)
- 基于C++实现的全景图像拼接源码(课程设计)
- 基于SIFT特征点提取和RASIC算法实现全景图像拼接python源码+文档说明+界面截图+详细注释(95分以上课程大作业)
资源上传下载、课程学习等过程中有任何疑问或建议，欢迎提出宝贵意见哦~我们会及时处理！
点击此处反馈
评论0