What is CPU?
CPU, also known as central processing unit, is generally composed of arithmetic unit, controller, internal memory, input/input device, interface circuit and bus, but with the advancement and update of technology, its function and structure are constantly expanding— -The circuit around the original CPU is also integrated into the device. Expansion of its hardware equipment to a certain scale, so that it can independently complete a more complex control function, this device is called a microprocessor. In the family of microprocessors, in order to be suitable for a certain application field, in terms of hardware composition-different from general-purpose microprocessors (such as 80C51)-there is a certain uniqueness, as the frequency converter specified in this article is often used The microprocessor has a six-way PWM wave output function, which can achieve specific control functions. It is also called a microcontroller, alias: single chip microcomputer. Because people in the industry generally regard the circuit board of the inverter single-chip as the CPU motherboard, from the perspective of convention and concise definition, this book also refers to the microcontroller (single-chip) as CPU.Microcontroller for inverter control, also known as "high-performance microcontroller", should be a dedicated control chip developed specifically. It must have at least six PWM wave formation and output circuits and ports to output the six inverter pulses required by the drive circuit; there should be A/D conversion circuit, and some also have D/A conversion circuit to adapt to the analog input 3. Processing of output; high-speed pulse signal input, output port and serial port sending and receiving pins are required to process various digital signals and communication instructions; program memory and data memory should be included to store programs and original data and Rewriteable data; of course, there are other circuits such as port drivers and various buffers, which will not be repeated here.
What goes into and out of each CPU pin is nothing more than some "signal flow", some only go in and out, and do not go back, such as the digital signal input by the control terminal; some only go out and go, but go and not return , Such as the relay signal output by the CPU on the control terminal; some are round-trip entry, and some are in and out, such as the signal transmitted between the CPU and the memory, and the operation display panel, such signals are circulated in both directions. All signals can be divided into two categories in terms of signal nature: digital and analog. The voltage detection signal and speed control command signal are often analog, and the start and stop signals of the inverter and the keyboard input signal are digital (switching). Some analog signals are processed by the external circuit of the CPU, such as those that are sent to the CPU after A/D conversion, and some are directly entered into the CPU pins and processed by the internal A/D circuit. The different hardware circuit of the CPU is inevitable. This leads to differences in external circuits.
The integration of the microcontroller is high enough. It is impossible to integrate all the circuit components required for the operation without limit. It needs the active cooperation of the external circuit to work. There are three working conditions that are necessary for the microcontroller, the so-called three elements of CPU work: +5V power supply, working clock, reset signal. The working clock is generated by the internal circuit of the microcontroller and the pin external crystal oscillator component to form an oscillation circuit; the reset signal is generated by the external reset circuit when the power is turned on a low (or high) pulse, send Enter the reset pin of the microcontroller, reset by the internal circuit control program, and enter the standby state. The program memory and data memory (memory for short) inside the microcontroller have limited capacity and use, and often require external memory-electrically erasable memory to complete some data storage tasks (especially user program storage tasks) , Which should constitute the four elements of the normal operation of the microcontroller. To accept the user's instruction or report the working status of the inverter to the user, a microcontroller needs a man-machine interface-to operate the display panel, communicate with the user, and communicate normally with the operation display panel, becoming the five elements of the microcontroller's work . In addition, the quality of the external circuit of each pin of the microcontroller will affect the operation of the microcontroller. Since then, the seven elements, eight elements, or even dozens of elements of the microcontroller's work have appeared immediately. In fact, according to the author, from the perspective of the microcontroller (or microprocessor, CPU), the three elements are necessary for work. Without it, the microcontroller cannot meet the most basic working conditions. Other reasons causing the microcontroller to not work are due to external circuits. It is not that the microcontroller itself is not working, right.The external circuits and external framework of the microcontroller have been set up, but only a "body" can't work, and a "soul" that directs the operation of the body-software control program. The program capacity of the inverter is relatively large, generally up to thousands of lines. The control function of the microcontroller is concentrated on two points. One is the control of the output PWM wave. At this point, the high-quality and low-quality inverters can see a clear difference. Some PMW waves are very optimized, and some are a bit bad. ——The output torque is small, the operation noise is large, and the carrier interference is also large; First, the state detection and protection of the inverter module, this task is completed together with the external circuit, and it is also the highlight of the inverter circuit.
Microcontroller——Single-chip microcomputer technology has become an important technical branch of automation control technology. I hope my friends should master some related knowledge by themselves, so I will not repeat them here.The failure rate of the CPU motherboard is relatively low, accounting for about 20% of the total failure rate. Faults mostly occur on fault detection circuits and control terminal circuits. The overhaul of the fault detection circuit has become an important overhaul of the CPU motherboard. When the fault detection circuit (follow-up circuit for voltage and current detection, temperature detection circuit) itself is damaged, it means a bit of "lied to report the military situation" and deliberately messed up. It is clear that the main circuit is good, but it reports an "output short circuit" fault or output failure Phase failure, obviously the fan is good, but reported overheating failure, etc., so that the inverter can not be put into normal operation. The failure of the control terminal is mostly because the user mistakenly accesses the high voltage, and the terminal power supply is burned out at 24V, the terminal input circuit is damaged and the input side circuit of the photocoupler is damaged, etc.
The damage rate of the CPU chip itself is below 2%. Due to the technical blockade involved, internal programs are not easy to crack. General maintenance personnel do not have the relevant conditions to repair the chip, only to purchase original manufacturer accessories, or to replace the CPU motherboard, the so-called "board level repair". But for the local damage of the CPU chip, you can use alternative methods to try to repair it.