Characteristics and differences between analog circuit ultrasonic generator and digital circuit ultrasonic generator

  The development of switching power supplies is closely related to the development of switching power supplies, and the development of switching power supplies is closely linked to the development of power electronic switching devices. It has also gone through three development stages: the era of bipolar switching transistors, the era of VDMOS, and the era of IGBT tubes; so its operating frequency has also gone through the development process of industrial frequency, low frequency, medium frequency to high frequency. With the rapid development of power electronic devices, the control of power electronic circuits is also developing rapidly. The control circuit was originally composed of discrete components with phase control as the means, and then developed to an integrated controller, and then to computer control of high-frequency switches. At present, it is developing towards higher frequency, lower loss and full digitalization.

  The old analog circuit ultrasonic generator has a simple structure and is easy to repair. Replacing the mold requires accurate adjustment of the ultrasonic frequency.

  The analog control circuit has the disadvantages of low control accuracy, slow dynamic response, inconvenient parameter setting, severe temperature drift, and easy aging. The emergence of dedicated analog integrated control chips has greatly simplified the control circuit of power electronic circuits. The switching frequency of the control signal is increased, and only a number of limited capacitance components are required to directly form an analog regulator with a correction link, which improves the reliability of the circuit. However, it is precisely because of the existence of resistors and capacitors that the inherent defects of analog control circuits, such as the accuracy and consistency of component parameters and component aging, still exist. In addition, analog integrated control chips also have problems such as high power consumption, low integration, inflexible control, and weak versatility.

  Replacing analog control with digital control can eliminate the shortcomings of conventional analog regulators such as temperature drift, which are difficult to overcome. It is conducive to parameter setting and variable parameter adjustment, and it is convenient to adjust the control scheme and realize a variety of new control strategies through program software changes. At the same time, it can reduce the number of components, simplify the hardware structure, and improve system reliability. In addition, it can also realize automatic storage of operating data and automatic fault diagnosis, which is conducive to the intelligent operation of power electronic devices.

There are generally three forms of ultrasonic generator application control technology: MCU control and FPGA control. However, we use UC3875 as the controller here, which can be used as the PWM duty cycle variable and overvoltage and overcurrent protection functions.