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Cypress CY8C24x33 BLDC解决方案

2008-01-04 嵌入式在线收藏 | 打印

Cypress 公司基于PSoC 芯片CY8C24x33的BLDC闭环速度控制能够实现片上硬件的过流保护。这一点在BLDC控制是非常重要的，从而避免了过流的损害。PSoC BLDC马达控制还具有总系统成本低的优点。

        本文介绍了BLDC 马达的优点，CY8C24x33 主要性能，方框图，采用PSoC 的 BLDC 马达控制方框图，过流保护原理图以及电动自行车主控制电路图和驱动器电路图。

        BLDC closed-loop speed control using the PSoC device CY8C24x33. Hardware over-current protection in BLDC control application is also explained.

        Brushless DC motor (BLDC) is now replacing the traditional brushed DC motor which has higher reliability, higher efficiency, and lower noise. BLDC is popular in almost every field such as consumer electronics, home appliances, and industrial controls.
Development of high-performance BLDC control systems requires higher accuracy. This is achieved by using closed-loop control in a majority of BLDC control systems.

        This application note describes BLDC closed-loop speed control based on the Cypress PSoC chip CY8C24x33. This chip could be used in BLDC motor control applications, such as E-bike.

        BLDC 马达较有刷DC马达的优点：

        The advantages of BLDC motors over brushed DC motors are:
        High Efficiency
        Reliable and No Arcing on Commutation – No Brushes to Maintain
        Higher Speed and Power to Size Ratio
        Heat is Generated in Stator – Easy to Remove
        Lower Inertia – No Commutator
        Higher Acceleration Rate

        BLDC motors are considered more efficient than brushed DC motors. For the same input power, a BLDC motor converts more electrical power into mechanical power than a brushed motor because of the absence of friction due to brushes.

        CY8C24x33 主要性能：

        CY8C24x33 derives from the CY8C2has the following improvements:
Flash memory is doubled from 4K in CY8C24X23 to 8K in CY8C24x33;
SC blocks of Column 0 in CY8C24x23A are replaced with a SAR (Suc with a higher sample rate of 300 Ksps;
        GPIO increases from 24 IOs in CY8C24x23A up to 26 IOs.

图1CY8C24x33方框图

                                图2基于PSoC 的 BLDC 马达控制方框图

       PSoC用在BLDC过流保护的主要资源：

The PSoC resources used in BLDC over-current protection are:

       1. A digital block is placed with PWM8, whose output is the driving signal of a power device.

       2. A Continuous Time block (ACB00) is placed with a comparator (CMPPRG). The first input of the comparator is the voltage of the shunt resistor, which is proportional to the current flowing into the motor. The second input is the reference voltage set according to the application. Comparator outputs are high when the shunt voltage is higher than the reference voltage, else the outputs are low.

       3. Another digital block is placed with a digital buffer (DigBuf). It has two simple two-input two-output digital buffers. PWM and Comparator outputs route through the DigBuf module.

       4. The PWM output is also routed through Input1 of DigBuf to Row Output Bus.

       5. The over-current signal and comparator output are routed through Input2 of DigBuf to Row Output Bus.

       6. The over-current signal and the PWM output logically cuts off the PWM output when over-current occurs.

       The over-current protection mechanism is an on-chip low cost solution.