In the field of modern power electronics, the series resonant inverter, due to its high efficiency and low loss, plays a significant role in applications such as induction heating and wireless energy transmission. This article will systematically introduce the control methods of the series resonant inverter, helping readers gain a comprehensive understanding of this key technology.
I. Working Principle of Series Resonant Inverter
The series resonant inverter consists of a DC power supply, switching devices and a resonant circuit. Its core lies in utilizing the characteristics of the LC resonant circuit. When the switching frequency approaches the resonant frequency, the circuit exhibits low impedance characteristics, thereby achieving efficient energy transmission. Compared with traditional inverters, the series resonant inverter has significant advantages such as low switching loss and low electromagnetic interference.
II. Classification of Main Control Methods
Frequency Control Method: Frequency control is the most basic control method. By adjusting the switching frequency, the output power can be changed. When the operating frequency is higher than the resonant frequency, the inverter exhibits inductive characteristics; when it is lower than the resonant frequency, it exhibits capacitive characteristics. This method is simple to implement, but it has disadvantages such as limited adjustment range and slow dynamic response.
2. Pulse Density Modulation (PDM) PDM controls the output power by varying the number of pulses within a unit time. Its advantage lies in the fixed switching frequency, which is beneficial for filter design. However, the power adjustment resolution is relatively low, which may result in significant output ripple.
3. Pulse Width Modulation (PWM) In PWM control, the frequency remains constant while the output power is changed by adjusting the pulse width. This method offers high power regulation accuracy and fast dynamic response, but it does increase switching losses and reduces system efficiency.
4. Phase Shift Control Phase shift control alters the output power by adjusting the phase difference between the two bridge arms. This method enables soft switching under zero-voltage or zero-current conditions, significantly reducing switching losses. However, the control algorithm is relatively complex and requires high requirements for the driving circuit.
III. Advanced Control Strategies
1. Adaptive Control Adaptive control can automatically adjust the control parameters according to the changes in load, ensuring that the system always operates in an optimal state. This method is particularly suitable for scenarios with frequent load variations.
2. Fuzzy Control Fuzzy control does not rely on precise mathematical models. It achieves control through empirical rules and has strong robustness against parameter changes and disturbances. However, it requires the design of appropriate membership functions and rule libraries.
3. Neural Network Control Neural network control achieves intelligent control by learning the system characteristics, and is capable of handling complex nonlinear relationships. However, it requires a large amount of training data and involves significant computational effort.
IV. Principles for Selecting Control Methods
Based on the application requirements, high-frequency induction heating is suitable for phase-shift control, while wireless charging systems may be more suitable for frequency control.
2. Consider efficiency requirements: In situations with high efficiency requirements, the soft-switching control method should be given priority.
3. Evaluate cost factors. The simple frequency control method has a lower cost, while the intelligent control solution has a higher cost but offers better performance.
V. Future Development Trends
Digital control technology: With the development of DSP and FPGA, digital control will become the mainstream, enabling the implementation of more complex algorithms and higher control accuracy.
2. Application of Intelligent Algorithms: Machine learning and artificial intelligence technologies will further enhance the adaptive capabilities and robustness of control systems.
3. Multi-objective Optimization Future control methods will place greater emphasis on the collaborative optimization of multiple objectives such as efficiency, EMI, and cost.
The control methods for series resonant inverters are diverse, each with its own advantages and disadvantages. In practical applications, the most suitable control strategy needs to be selected based on specific requirements. With the advancement of power electronics technology, more advanced and intelligent control methods will continue to emerge, promoting the application of series resonant inverters in a wider range of fields.
Post time: Dec-09-2025