Abstract: This document will guide you how to implement high-performance three-phase inverter power supply system with SPMC75F2413A and IPM PS21865A.
Keyword: SPMC75F2413A, PS21865A, Inverter Power Supply

1 Introduction
An inverter power supply is a power supply conversion device characterized by exact waveform output, steady voltage output and adjustable output frequency and voltage. They are mainly used in the fields of instrument and meter, sensing and industrial control. This document is intended to introduce how to perform the three-phase inverter power supply with SPMC75F2413A and IPM (PS21865A).

2 Features
SPMC752413A, a new 16-bit microcontroller in 'nSP? family, is a dedicated chip for inverter control applications. With its powerful timers and PWM output function, SPMC752413A can drive various motors easily.
The SPMC75F2313A operates at 0~24MHz under 4.5~5.5V. The memory capacity includes a 32K-word flash memory plus a 2K-word working SRAM; other features include 64 programmable multi-functional I/Os; 5 general-purpose 16-bit timers (two timers for position detection for BLDC motor and two timers for quadrature-encoder pulse circuit), which support capture input/PWM compare match output function; two dedicated configurable timer period registers; programmable watchdog; low-voltage reset; 8-channel10-bit analog-to-digital conversion. Following are the detailed features:

3 System Design
The high-performance three-phase inverter power supply system consists of Sunplus 16-bit MCU SPMC75F2413A and Mitsubishi IPM PS21865A. The block diagram is shown in Figure 3-1.

Figure 3-1 System Block Diagram

System functions:
A. Performance adjustment arguments: To fulfill the specific needs for various applications.
B. Real-time information and status display: To show the system status and MMI.
C. Dedicated keyboard for system arguments setting and control.
D. Advanced system protection: To protect system from damage in abnormal operation.
Operation flow:
SPMC75F2413A integrates the driving signals with the control information from keyboard or communication interface. After being powered by PS21865A, the signals are used to drive the motor. Meanwhile, SPMC75F2413A performs supervision function. In case, if fault occurs, it will protect the system and issue signal to alert users.

4 Hardware Design
Wave synthesizing circuit is the center of the system operation, and its performance and structure decides the whole system performance. Here the circuit is composed of SPMC75F2413A, IPM PS21865A, transformer and output filter circuit. There is a three-phase frequency bridge and its driving circuit in the PS21865A to magnify the SVPWM frequency. The output transformer and filter circuit are mainly for transforming the magnified SVPWM signal into sine wave, filtering the higher harmonic and outputting correct wave. SPMC75F2413A has the following three major functions,: Generating SVPWM signal to drive the inverter power supply, performing MMI function for easy system control, and dealing with fault to protect system from damage.
The three-phase complementary SVPWM signal generated by SPMC75F2413A outputs via pins IOB0~5 to control the PS21865A three-phase full bridge circuit. The generated signals are supplied to load after being processed by the power synthesizer, low pass filter and three-phase output transformer. Meanwhile, both system operation current and output voltage will be fed back for system control. IOB6 and IOB7 are for the error detection and over-load protection input; once PS21865A operates abnormally (over-voltage, low-voltage, over-current or over-heat) or system over-load, MCU will disable the driving signal to PS21865A and issue an interrupt to be processed.
We will not discuss more details here for other general modules. For the system diagram block, please refer to Figure 3-1.

5 Software Design
The system software falls into three parts: Waveform generator (SVPWM generator and referred driving routines), system control program, and MMI program.
The waveform generator is shown in Figure 5-1. Here the SVPWM generator structure is reduced. The function of structure (except PWM generator module) will be performed in PWM generating routine with software. The modulation coefficient and multiplier are used to control wave amplitude and compensate power-supply fluctuation.

Figure 5-1 Driving Structure

PWM period interrupt subroutine is the key of the waveform synthesizing shown in Figure 5-2. Program will perform phase accumulation, look up table to calculate sine/cosine wave, calculate vector coefficient, convert spatial vector and update duty ratio, then complete the rest of processes and return.

Figure 5-2 PWM Period Interrupt Process

System control is the centre of the system operation, which is responsible for transmitting the controlling signals based on the system configurations and current status making system perform normally.
Man Machine Interface (MMI), an easy-to-use interface designed to dominate inverter, mainly executes start/stop functions and all argument configurations to driver.

6 Epilogue
The inverter control development requires real-time and readable code by mixing C and assembly languages. 'nSP? IDE provides a user-friendly interface to embed ASM routine in C code or C routine in assembly code.
SPMC75F2413A features rich hardware resources including two timers and 30 IO pins to use. With this built-in dedicated hardware, it is quite easy to develop inverter control on SPMC75F2413A. Because of these tremendous features built inside the SPMC75F2413A plus satisfied engineering support guaranteed from Sunplus, one of the Top 20 IC design companies worldwide, SPMC75F2413A is one of best solutions in the industry today for general inverter and home appliance markets.

7 Reference
[1] Lei Sixiao, Li Bocheng, and Lei Xiangli, Sunplus 16-Bit Microcontroller's Fundamental and Application, XIDIAN University Press
[2] Sunplus Technology, SUNPLUS SPMC75F2413A Programming Guide V1.1
[3] Mitsubishi Electronics, PS21865A Data Sheet [M]