Kenichi Nakashima
Kenichi Nakashima
Sr Staff Product Marketing Specialist
Published: July 4, 2022

Renesas will release a RL78/F24 BLDC-RSSK (12V Motor Control Renesas Solution Starter Kit for RL78/F24) in October, 2022. This RSSK is appropriate for BLDC/FOC motor control and includes a small motor. 
This RSSK includes a small motor and an inverter board, as well as three different motor control software versions: 
#1 Sensorless FOC control based on 3-shunt, #2 Sensorless FOC control based on single-shunt, #3 Sensorless trapezoidal control.
As soon as the user receives this kit, the motor operation can be evaluated targeting for e.g. future pumps and fans applications.

fig1 Renesas Solution Starter Kit

Figure 1 Renesas Solution Starter Kit (RTK7F124FGS0000BJ)

Fig 2 Block Diagram

Figure 2 Block Diagram (Pump Example)

RL78/F24 BLDC-RSSK provides all reference design materials (circuit diagram, PCB pattern diagram, etc.) and characteristic data (EMC) so that the customer can easily design a motor control board for their specific application.
As an extension of the already existing RL78/F13, F14 devices, at first, the new RL78/F24 MCU becomes available, which is providing an optimized feature set for small motor control. (Fig. 3)

Fig 3 RL78/F24 Motor Control Function

Figure 3 RL78/F24 Motor Control Function

Extended complementary PWM mode of Timer RDe adds symmetric/asymmetric PWM function, and decimation function of interrupt and A/D trigger signal to existing Timer RD functions. The sensorless single-shunt FOC control method is realized by using the extended complementary PWM mode. For the current detection in U-, V-, W-phase, it is necessary to acquire the single-shunt current in the state shown in Fig. 4. 

Fig 4 Current Detection for Single-Shunt Each Phase

Figure 4 Current Detection for Single-shunt Each Phase

The shunt current is measured by using the A/D converter, with its short conversion time. By using asymmetric PWM output function of extended complementary PWM mode, A/D conversion can be performed without changing the PWM duty ratio. (Fig. 5)

Fig 5 Phase Shift for Single-shunt Current Detection

Figure 5 Phase Shift for Single-shunt Current Detection

Single-shunt sensorless FOC motor control can be easily developed by using this kit. Furthermore single-shunt FOC control systems can be realized at lower costs, because the components number is reduced compared to three-shunt FOC control.
Another new RL78/F24 feature is the application accelerator unit (AAU). The AAU performs various arithmetic operations on its own, while off-loading the CPU. Hereby the overall required CPU processing for the vector control operation is strongly reduced. 
Table.1 shows a list of specific AAU functions.

Table.1 Application Accelerator Unit Operation List

AAU Algorithm Mode

Execution Cycle

1. Sine operation

1 clock

2. Cosine operation

1 clock

3. Clarke & Park transformation

7 clocks

4. Inverse Park (I-Park) transformation

6 clocks

5. Inverse Clarke (I-Clarke) transformation

5 clocks

6. PI control for motor operation

15 clocks

7. Clarke & Park transformation and PI control for motor operation

22 clocks

8. I-Park & I-Clarke transformation

11 clocks

9. PI control for DC/DC converter control operation (1 to 3 channels)

6 to 18 clocks

10. Multiply 32-bit × 32-bit = 64-bit operation

5 clocks

This kit utilizes “Clarke & Park transformation and PI control for motor operation” (No.7) and “Inverse Park & inverse Clarke transformation” (No.8).

The RL78/F24 MCU used in this RSSK provides various functions that are effective in motor control. It is an ideal product with small size and very low power consumption that can meet various needs of customers' solutions.

Scheduled sales start of this kit: October 2022
Kit mode: RTK7F124FGS00000BJ


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