Renesas Electronics designs several motor control ICs for China
Under the dual pressures of energy shortage and strict environmental protection requirements, higher energy efficiency, better dynamic performance and lower operating noise have become the inevitable trend of motor drive design. Therefore, the conversion from the traditional AC motor design to the advantages of efficiency, noise, weight, life and other advantages of the brushless DC motor (BLDC) / stepper motor (SM), is also becoming a hot spot for motor control application designers. .
120° DC brushless motor and stepper motor control
As is known, the interval between the three Hall sensors is 120°, and each Hall signal is switched in accordance with the direction of the rotating magnetic pole. According to the state of the three Hall signals, position information can be obtained once every 60° (6 modes per cycle). If the conduction mode of each phase is switched in accordance with the timing, the rotating magnetic flux is generated as shown in the following figure, so that the rotor obtains a moment and rotates.
The calculation of the motor rotation speed is obtained from the difference between the current timer count value and the timer count value before 2π [rad]. The timer count value is obtained by an external interrupt triggered by the Hall signal, during which the timer TAU is always free to count. This method of speed measurement is equally applicable even if there are positional deviations in the three Hall sensors.
In order to start the motor and obtain the position information of the rotor, it is necessary to provide a 60° start timing to the motor. This triggers the external interrupt corresponding to the Hall signal and continuously performs commutation control to allow the motor to rotate. The adjustment value of the duty ratio at any time (n) is calculated by the following formula, thereby realizing the adjustment of the rotational speed of the motor.
A stepper motor is an open-loop control motor that converts an electrical pulse signal into an angular displacement or a linear displacement. In the case of non-overloading, the speed and stop position of the motor depend only on the frequency of the pulse signal and the number of pulses, and are not affected by load changes. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction, called the "step angle", and its rotation is performed step by step at a fixed angle. The angular displacement can be controlled by controlling the number of pulses to achieve accurate positioning. The speed and acceleration of the motor can be controlled by controlling the pulse frequency to achieve the purpose of speed regulation.
Designed for the Chinese market
For China's increasingly mature motor control applications, Renesas Electronics has introduced a number of MCU products specifically for the Chinese market, aiming to achieve high processing performance with the lowest power consumption, enhanced computing power and peripheral functions.
R7F0C009 series
R7F0C009 is a small-capacity single-chip microcomputer developed by Renesas Electronics for electric bicycles, power tools, household appliances and other applications that require control of DC brushless motors. The RL78 core not only has a high-precision (±2%) on-chip oscillator, a CPU with a 24MHz operating frequency, and other standard built-in functions. It also uses a multiplier and multiply-accumulate instruction from the R8C family with verifiable Tracking records, such as timer RD/RJ, event link controller, 1-channel op amp, and 2-way analog comparators, allow the system to be built at a lower overall cost for more compact size and lower power consumption.
The series of MCUs are configured with 30-44 pins and a maximum of 16KFlash. The chip integrates up to 12 channels of ADC and motor control dedicated timer RD for three-phase PWM drive. It is especially suitable for DC brushless motors because it can output 3 pairs of PWM waveforms that are non-overlapping and inverting.
The Event Link Controller (ELC) can use the timer to trigger (automatic/delay) A/D sampling without CPU intervention to improve motor control performance.
The R7F0C009MCU also integrates a programmable gain amplifier and comparator to support 2-channel comparison (high/low speed selectable), high speed travel mode (motor current feedback to prevent overcurrent protection) and low power low speed travel mode (battery detection) It can be used for current monitoring protection.
In addition, most of the MCU's pins can support a large current output of 40mA, which can reduce the number of external drive components and further reduce costs. Renesas Electronics also provides reference designs for electric bicycle controllers and DC brushless power tools for motor control microcontrollers, shortening customer entry time and product development cycle.
R7F0C014 series
The target market of the R7F0C014 series of microcontrollers is locked in inverter motor control, software modems, household appliances, mobile devices, medical and healthcare equipment and other consumer electronics, office equipment, industrial equipment and other fields. The series also features the RL78 core and is available in 32-pin LQFP (0.8mm pin pitch) and 64-pin (0.5mm and 0.65mm pin pitch) packages.
The R7F0C014 not only has a high-precision (±1%) on-chip oscillator, a 32MHz operating frequency CPU, and other standard built-in functions, but also uses a faster multiplier and multiply-accumulate R8C family than the RL78/G13 series. Command function with verifiable trace, such as timer RD/RG for three-phase PWM drive, data transfer controller, event link controller, can frame the system at a lower overall cost for a more compact size And lower power consumption.
In addition, it also supports wide voltage operation (1.6V-5.5V working voltage), and built-in a large number of functions to support functional security (such as A / D converter test function), and large-capacity Flash (128KBFlash, 8KBRAM, 8KB) Data Flash), users can add a large number of security-related codes to meet IEC and security requirements.
R7F0C806/807 series
The R7F0C806/807 series of microcontrollers feature a high-precision ±2% on-chip oscillator (TA=0+40°C), making it possible to run the CPU up to 20MHz with built-in optional power-on reset and watchdog timers. It helps the system achieve a more compact size and low power consumption, making the entire system cost less. In addition, the R7F0C806/807 has a built-in real-time output control circuit that can simultaneously achieve 8-channel output through the PWM output mode of the timer, which helps customers to develop brushless DC motor control and stepper motor control (two at the same time).
Available in 20-pin SSOP and SOP packages, and in a 4KB-8KB flash array, the family is ideal for small appliances and general-purpose consumer applications.
In practical applications, by using the TAU's PWM output function, one DC motor or two stepper motors can be controlled; by generating an interrupt caused by INTP0, the output can be cut off; by software setting, it can be forced to cut off. Select between the four outputs of Hi-Z output, low level output, high level output, and disable cut output.
