Sako MOSFET and Zhaoyi Innovation MCU design scheme cooperation case (2)

release time:2022-03-17Author source:SlkorBrowse:2177

Scheme design of non-inductive micromotor based on GD32E230/F303 MCU

Dental cell phone, also known as oral cell phone, is a kind of medical instrument specially used in stomatology. Since its coming out, it has been welcomed by patients and operators with its unusual rotation speed, quickly replacing electric cell phone and becoming an indispensable tool in dental work today.

In this scheme, Zhaoyi Innovation GD32E230/F303 series MCU is adopted as the main controller, which has the characteristics of high speed, stability, low noise and low cost. It can be used in stomatology to hold high-speed dental needles for drilling, grinding teeth, tooth cleaning and beauty care.

Electrical parameters of motor scheme

· Rotational speed ≥ 300,000 rpm, and the maximum torque range is 0.075-0.15N.cm
· Positive and negative rotation/speed control/speed display
· Multi-channel air valve control
· Noise < 70dB

1、GD32E230 Low-cost Scheme of Non-inductive Square Wave Control

Program characteristics

GD32E230 super-value MCU with Arm Cortex-M23 core is used as the main controller. In the non-inductive square wave control, the commutation signal is mainly obtained by the way of back EMF zero crossing (the phase difference between the signal of back EMF zero crossing and the commutation signal of the motor is 30° Electric angle). In order to get the zero-crossing signal of back EMF, the hardware comparator method is used to compare the detected terminal voltage with the neutral voltage of the motor to get the zero-crossing signal of back EMF.

This scheme has the characteristics of simple circuit, low cost, etc., and is mainly used in dental cleaning equipment, dental care and other occasions.

Scheme circuit board

Main specifications of GD32E230 series MCU
· Cortex-M23@72MHz, 55DMIPS processing performance· Flash: 64KB/32KB/16KB· SRAM : 8KB/6KB/4KB
· High-speed and high-precision ADC,12Bits ADCx1@2.6Msps,10 channels· Advanced timer x1 can generate 6 complementary PWM outputs with adjustable dead time.· General timer x5· With Flash hardware encryption protection· Multiple serial communication modes: I2Cx2, SPIx2, UARTx2;· Rich package types: TSSOP 20/LGA20/QFN28/QFN32/LQFP 32/LQFP 48· Power supply: 1.8V~3.6V· Single-cycle hardware multiplier, hardware divider, hardware frequency divider, nested vector interrupt controller (NVIC) and other independent resources· Operating temperature range of industrial grade: -40℃~105℃· Industrial ESD characteristics: 6000 Volt

2、GD32F303 High Performance Scheme of Non-inductive FOC Control

Program characteristics

Sensorless FOC control mainly uses motor mathematical model and some knowledge of automatic control principle to realize motor control. In the control of induction-free FOC, it is usually necessary to use the corresponding observer to obtain the rotor position indirectly, in order to obtain better dynamic and static characteristics, control accuracy, response speed and stability of the system. This scheme is designed by GD32F303 mainstream MCU based on Arm Cortex-M4 core. GD32F303 has floating-point operation function on the chip, which can better set the proportional parameters of PID control and has fast dynamic response.

The control method is synovial ring observer method (please refer to the application data of brushless DC motor control for specific formula and principle). It is realized by using the control principle of synovial membrane variable structure in automatic control principle. In fact, variable structure is a control strategy of variable structure control system, which is characterized by its discontinuous control. Under certain characteristics, it forces the system to move in a small amplitude and high frequency up and down the specified hyperplane, which is what we often call "sliding mode" or "sliding mode" motion. This sliding mode has nothing to do with the parameters and disturbances of the system, and can be designed, so the system has good robustness.

Technical highlights

The start-up of brushless and non-inductive DC motor is a key step. In order to achieve the characteristics of fast and stable start-up and low noise, I/F start-up method is adopted in this scheme. The core of I/F start-up mode is to generate a rotating current vector with amplitude following the reference value and frequency gradually increasing in the armature winding, so as to accelerate the rotor start-up. Its characteristic is that it works in the state of open-loop speed and closed-loop current. After coordinate transformation, the stator winding current is projected on the rotating coordinate system determined by the commanded position angle, and it is constrained by the expected value, which can effectively avoid overcurrent. Its control block diagram is shown in the following figure.

The rotating speed of this scheme can be 100~380,000 RPM at high and low speed, and it is suitable for micro high-speed motor applications, such as medical dental high-speed mobile phones, grinding machines, etc.

Scheme circuit board

Main specifications of GD32F303 series MCU

· Cortex-M4@120MHz main frequency, processing performance of 150DMIPS
· Flash: 256KB~3072KB· SRAM : 48KB~96KB· Power supply: 2.6V~3.6V
· 3 12-bit ADCs @ 2.6msps, 21 channels
· 1 24-bit SysTick timer system beat timer, up to 4 general-purpose 16-bit timers, 2 basic timers and 1 enhanced timer.
· Multiple serial communication modes: I2C x2, SPI x3, USART+UART x5· Rich package types: LQFP48/LQFP64/LQFP100/LQFP144
· Single-cycle hardware multiplier, hardware divider, hardware frequency divider, nested vector interrupt controller (NVIC) and other independent resources
· Floating Point Unit floating point arithmetic unit
· Operating temperature range of industrial grade: -40℃~85℃

Focusing on the 32-bit MCU of the GD32 series of Zhaoyi Innovation (www.bjzycxkjgf.dayinmao.com), the mos FET of SAKO Micro SLKOR (www.slkormicro.com) is widely used in this kind of scheme, such as TVS and ESD tubes which are responsible for motor driving, anti-static and surge discharge in peripheral circuits. Sawei Technology Co., Ltd. (http://www.slkormicro.com) was founded in 2005. For more than ten years, it has been adhering to the concept of "creating value by technology", mainly researching and producing silicon carbide, SiC silicon carbide diode, SiC silicon carbide MOS tube and IGBT single tube. Series 2301, 3401, 3904 and 13n50 products such as high and low voltage MOS tube, ChinaMOS, COOL MOS tube, power management IC, hall Hall element SL1603SL SL1613SH SL1615SH, thyristor, fast recovery diode and diode can also be matched with KingHelm (WWW.BDS666.COM) WiFi antenna, GPS antenna, Beidou antenna and TWS Bluetooth headset ceramic antenna. Mainly used in: new energy vehicles, intelligent robots, inverters, power tools, power electronics, switching power supplies, outdoor lighting power supplies, PD fast charging, TWS Bluetooth headsets and other fields.

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