Application of SPMC75F2313A in electric bicycles

Introduction
China is the country with the largest number of bicycles used as a means of transportation in the world. At present, there are nearly 500 million bicycles. Among them, electric bicycles have developed rapidly in recent years, and the output has doubled year by year. In 2004, the output reached 6.76 million, and in 2005 it was also around 10 million. The Yangtze River Delta, the Pearl River Delta, and the Bohai Bay are important production bases for electric vehicles. Industry insiders said that among the 500 million bicycles, if 10% of them are replaced by electric bicycles, that is 50 million. Calculated at an average price of 2,000 yuan per bicycle, the most conservative estimate is a big cake of 100 billion yuan, and the market prospect is very broad.
The main purpose of this article is to vigorously promote the application of SPMC75 series chips, verify its performance according to national standards, and enter various domestic home appliance manufacturers.

1 Working principle
Electric bicycles are green and environmentally friendly transportation tools with functions such as electric drive, pedal drive, and electric and pedal combined use. The principle and structure of electric bicycles are not complicated. It can be considered to be a set of motor drive mechanisms on the basis of bicycles (see Figure 1?1). The battery sends power to a motor through a controller, and the motor is placed in the rear wheel. The rotation of the motor drives the bicycle forward. The controller of the electric bicycle is connected to a speed control handle, and a power sensor is installed on the pedal center axis. Turning the speed control handle allows the controller to detect different voltage values. The controller simulates and adjusts the voltage delivered to the motor according to the voltage value, thereby controlling the speed of the motor.

Figure 1-1 Electric bicycle control block diagram

The controller brushless motor control method is to control the conduction and cutoff of the upper and lower arm MOS tubes of the motor three-phase drive according to the motor position feedback signal, thereby realizing electronic commutation. As shown in the figure below, the motor is connected in a triangle, and the conduction sequence of the upper and lower arm MOS tubes of the three-phase drive is: V1-V2, V2-V3, V3-V4, V5-V4, V5-V6, V1-V6.

Figure 1-2 Driving circuit

2 System Block Diagram
The electric bicycle uses SPMC75F2313A as the main control MCU. The main tasks of the MCU are 1:1 power assistance, speed regulation voltage detection, battery voltage detection, current detection, overcurrent interrupt detection, 3-way Hall position detection, online debugging function, abnormal display output, brake control, 6-way motor drive output, speed display interface, and high-speed speed limit. The system block diagram is as follows:

3 Controller electrical specifications
★ Motor used: Brushless DC ★ Output power: 500W
★ Input voltage: 48/36V DC ★ Rated current: Low speed (35A)/High speed (25A)
★ Operating temperature: -40 degrees ~ 120 degrees ★ Undervoltage protection: 41V/31V±1V
★ Controller power consumption: Normal mode <3 watts, power saving mode <1.5 watts

4 Controller function introduction
◆Zero start ◆1:1 power assistance
◆Automatic cruise ◆Automatic direction identification
◆Speed ​​display ◆Power off when stalled
◆High speed limit ◆Brake control
◆Reverse without damping ◆Low noise when starting
◆Intelligent power saving mode ◆Fault display output
◆Motor phase angle 120 degrees ◆Electronic soft brake (EBS)
◆MCU built-in position detection anti-interference interface

4.1 Motor phase angle
It can be used for motors with Hall signal phase difference of 120 degrees.

4.2 1:1 Power Assist
1:1 power assistance means that when the speed control handlebar is not rotated and the electric vehicle is turned on, the electric vehicle will provide 1:1 power assistance according to the rider's riding speed.

4.3 Electronic Soft Brake (EBS)
provides intelligent electronic braking function to ensure that the vehicle is stabilized within a short distance after braking.

4.4 Undervoltage protection
Provides accurate voltage detection and is judged by software. It can accurately grasp the battery voltage value and will not switch on and off at the undervoltage boundary, which can avoid over-discharge and damage to the battery. This low voltage value can be set by software.

4.5 Automatic phase identification
Allows users to connect the three wires of the motor at will, and the external output wire determines whether to identify the phase change.

4.6 Speed ​​display
Directly feed back motor voltage signal or Hall signal to provide instrument indication

4.7 Automatic cruise control
Turn the handle to the desired angle to make the electric vehicle reach a certain speed. If the handle does not rotate within 8 seconds (the time can be set), the electric vehicle can keep the vehicle at this speed. Pressing the brake can release the cruise control function or turning the handle back to release it.

4.8 Output voltage waveform
Provides square wave voltage waveform output.

4.9 Flip without damping
Pushing backward without resistance, reversing easily.

4.10 Power off when stalled
The software can intelligently detect motor stall conditions and provide power off delay protection. The delay time can be set by the software.

4.11 High speed limit
The maximum speed is set by the short circuit. The maximum speed can be reduced when the short circuit is used, and the maximum speed can be reached when the short circuit is open.

4.12 Zero start
When starting, you don’t need to step on it, you can start it by controlling the handle.

4.13 Intelligent power saving mode
After the power is turned on for a period of time, if the user does not input any work instructions, the controller will enter the sleep state to save battery power.

4.14 MCU built-in position detection anti-interference interface
The powerful variable frequency control chip provides a Hall signal feedback interface in hardware. This interface also provides anti-noise and anti-interference functions, providing more accurate commutation, improving motor efficiency, and reducing improper commutation.

4.15 High-precision speed counter
Powerful frequency conversion control chip, including 16-bit speed interface counter, can improve the accuracy of speed calculation and avoid speed jitter and other phenomena.

4.16 Low noise at
startup When starting, it includes current waveform correction, low noise, and low vibration to meet the requirements.

5 Introduction to chip features
This design uses the SPMC75f2313A*LQFP44 microcontroller, and the core uses the μ'nSP16-bit microprocessor with independent intellectual property rights of Lingyang Technology. It integrates a variety of functional modules: multi-function I/O port, serial port, ADC, timer counter and other common hardware modules, as well as PWM generator that can generate motor drive waveform, multi-function capture comparison module, BLDC motor drive dedicated position detection interface, two-phase incremental encoder interface and other special hardware. The
SPMC75f2313A*LQFP44 package is shown in Figure 5?1. The specific characteristics of the chip are as follows:

Figure 5-1 SPMC75f2313A～LQFP44 package

6 Conclusion
SPMC75 series MCU has strong anti-interference ability and is widely used in control fields such as frequency conversion home appliances, inverters, and industrial control.