A kind of electric bicycle downhill automatic deceleration control device of system of the present invention and method,The deceleration control system mainly include a microprocessor,One motor drive circuit and a feedback detection circuit,The microprocessor receives electric switch aperture data and controls driving voltage and driving current that the motor drive circuit generates correspondence,When motor is operated according to the driving voltage and driving current,Microprocessor utilizes feedback detection circuit monitoring voltage and current status at any time； When microprocessor judges that electric bicycle is just locating the traveling of what descending according to voltage and current state,The duty cycle (duty cycle) of system's reduction pulse-width modulation signal,Make to reduce by the magnitude of current of motor,To reduce motor rotary speed,The descending speed of electric bicycle is enabled to slow down,It prevents that accident occurs during descending.本發明係一種電動代步車下坡自動減速控制裝置及方法，該減速控制裝置主要包含一微處理器、一馬達驅動電路及一回授檢測電路，該微處理器接收電門開度資料而控制該馬達驅動電路產生對應之驅動電壓及驅動電流，當馬達依據該驅動電壓及驅動電流運轉時，微處理器利用回授檢測電路隨時監測電壓及電流狀態；當微處理器根據電壓及電流狀態判斷電動代步車正處於下坡行進時，係縮減脈寬調變信號的工作週期(duty cycle)，使通過馬達的電流量降低，從而降低馬達轉速，令電動代步車之下坡速度減緩，防止在下坡過程中發生意外。
