Design method of DC frequency conversion washing machine based on SPMC75F2413A

1 Introduction
Washing machines are an indispensable household appliance in the home, and they are developing very fast. Fully automatic washing machines are favored by everyone because of their convenience. Fully automatic means that a series of processes such as water filling, washing, rinsing, and drying are completed automatically. The controller usually has several washing programs for users to choose from for different clothes. Frequency conversion control is widely used in the control of washing machines due to its advantages such as high performance and energy saving. The following introduces the control system of a DC frequency conversion washing machine designed using the SPMC75F2413A and SPCE061A microcontrollers of Lingyang Technology Company.

2 Chip Features
SPMC75F2413A is an embedded 16-bit microcontroller for variable frequency drive developed by Sunplus Technology Co., Ltd. It is suitable for variable frequency motor drive, power supply, home appliances and in-vehicle fan control systems.
Features include:
◆ Sunplus 16-bit u'nSP processor (ISA 1.2)
◆ Operating voltage: 4.5V ~ 5.5V
◆ Maximum operating speed: 24MHz
◆ Operating temperature: -40 ℃ ~ 85 ℃
◆ On-chip memory:
32KW (32K×16) Flash
2KW (2K×16) SRAM
◆ Phase-locked loop circuit based on clock generation module
◆ Watchdog timer
◆ 10-bit analog/digital converter
8-channel input
10us (100kHz) conversion time
◆ Serial communication interface
Universal asynchronous serial communication interface (UART)
Standard peripheral interface (SPI)
◆ 64 (QFP80) / 53 (QFP64, SDIP64) general-purpose input and output pins
◆ Power management
2 low-power modes: Wait/Standby
Each peripheral can be powered independently
◆ Two compare match timers
◆ 5 16-bit general purpose timers
2 PWM outputs for driving motors (complementary 3-phase 6-way PWM outputs)
2 for speed capture
1 for speed feedback loop
◆ Center or edge PWM output
◆ PWM output protection through external error protection pin
◆ Programmable dead time control ◆
PWM service and error interrupt generation
◆ Ability to drive AC induction motors and DC brushless motors
◆ Embedded online simulation function (ICE)

3 System Overall Solution Introduction
The whole system mainly consists of two parts: the DMC control board controlled by SPMC75F2413A and the PANEL board controlled by SPCE061A. The connection system block diagram between the two is shown in Figure 3-1.

Figure 3-1 Components of a variable frequency washing machine system

The PANEL controller uses a 16-bit SPCE061A controller, and its main functions include: key scanning, status display and communication. The washing machine is controlled by key input to select the operation mode, and the water volume, reservation time, and detailed parameters of washing, cleaning and dehydration can be set; the power button is the starting connection with the drive control circuit board, and the start or pause button is to run the washing machine or pause. The remaining time during the operation is displayed through a 7-segment display.
The DMC controller uses a 16-bit SPMC75F2413A single-chip controller, and its main functions include: detecting the position signal of the motor rotor and driving the DC brushless motor in a 120-degree square wave PWM drive mode.

4 System Hardware Design
The system control includes two parts: the DMC control board and the PANEL control board. The following mainly introduces the hardware design of the DMC control board.
4.1 Power supply circuit
Figure 4-1 shows the EMI power filter and single-phase full-bridge rectifier circuit. The AC power input connector is CON1, and the voltage is 220VAC. The power input end passes through the surge absorber ZNR3 to prevent excessive voltage surges from damaging the device. C8 and C12 are connected in series to the ground point, which can usually also be connected to the housing. The output DC voltage can be obtained after rectification by the full-bridge rectifier DB1 and filtering by C13.

Figure 4-1 EMI power filter [page]

Figure 4-2 is a DC/DC power supply circuit. The output power of the power supply is P+18V and +12V. After the P+18V power is output, it generates P+15V and P+5V through IC21 and IC22 respectively to supply the working voltage of the IPM power module. And +12V generates +5V power through linear regulator IC20 to supply the working voltage of digital circuits such as SPMC75F2413A.

Figure 4-2 DC/DC power supply circuit

4.2 MCU control circuit
Figure 4-3 shows the MCU control circuit. This part of the circuit is mainly based on the u'nSP SPMC75F2413A microcontroller. CON5 is connected to the online debugger and emulator ICE.

Figure 4-3 MCU control circuit

4.3 IPM motor drive circuit
Figure 4-4 is an IPM motor drive circuit. Because the driven motor is a three-phase variable frequency, the microcontroller generally needs to be able to output 6 PWM signals. SPMC75F2413A can complete this function in chip hardware through MCP and PDC timer modules. The IPM module integrates the drive circuit and overcurrent detection circuit. The PWM output signal of the MCU is sent to the IPM module through the optocoupler. However, in actual application, it is necessary to consider the protection of the MCU and the rapid generation of high-impedance signals to the IPM module and the normal drive of the optocoupler. Therefore, the buffer circuit of IC12 is added to the circuit; the overcurrent feedback signal is connected to the input pin of FTINx after the optocoupler, so as to be able to quickly protect the IPM module. D5, D6, D7, C37, C40 and C43 generate the bootstrap circuit to provide the drive signal of the IPM upper arm switch.

Figure 4-4 IPM motor drive circuit