ZVS circuit diagram: full analysis of the principle, application, component role, frequency regulation and comparison with PWM circuit

I. Overview of ZVS Circuit Diagram

ZVS (Zero Voltage Switching) is a power conversion technology aiming to achieve zero voltage switching in switching power circuits. The working principle of the ZVS power supply is to realize highly efficient power conversion by controlling the turn-on and turn-off timing of the switching tubes. In the ZVS circuit, the switching tubes are switched when the voltage is zero, thus greatly reducing the switching losses and improving the overall efficiency of the circuit.

II. Working Principle of ZVS Circuit

The working principle of the ZVS circuit can be summarized in the following steps:

• Startup Process: When powered on, the current flowing through L1 is zero. The power supply turns on Q1 and Q2 through R1 and R2, and the current in L1 gradually increases. Due to the difference in the characteristics of the two switching tubes, the currents flowing into the two switching tubes are different. Assuming that the current of Q1 is greater than that of Q2, the gate voltage of Q1 is higher than that of Q2. Through the two diodes D1 and D2, the voltage at point a is lower than that at point c, forming positive feedback, which makes Q1 turn on and Q2 turn off, thus completing the startup process.
• Steady-State Operation: When Q1 is turned on in the steady state, the current of T1 charges C1. The voltage of C1 gradually becomes negative at point a and positive at point c and increases sinusoidally, while the current of T1 decreases sinusoidally. When the voltage of C1 is around zero, Q1 turns off and Q2 turns on. After C1 is discharged completely, the current in the winding of T1 from point c to point a reaches the maximum value and then charges C1, making the voltage of C1 positive at point a and negative at point c, and the voltage across C1 increases sinusoidally. At this time, the two MOS tubes enter the amplification region simultaneously.
• Realization of ZVS Condition: Under the ZVS condition, the switching tubes are switched when the voltage is zero, thus realizing zero voltage switching. This needs to be achieved by controlling the parameters of the resonant capacitor and the resonant inductor to ensure that the resonant circuit reaches a zero-current state at the appropriate time point.

III. Applications of ZVS Circuit Diagram

The ZVS circuit diagram has important applications in many fields. The following are some common applications:

1. Power System

• DC-AC Power Conversion: In the process of converting DC power into AC power, the ZVS circuit can improve the conversion efficiency, reduce energy losses, and make the output AC power quality higher and more stable. It can be applied to equipment such as uninterruptible power supplies (UPS).
• Power Transmission and Distribution: It helps to improve the power transmission efficiency and reduce line losses. Especially in high-voltage direct current transmission systems, ZVS technology can be used in key equipment such as converters to improve the overall performance and reliability of the system.

2. Communication Equipment

• Power Management Module: It provides stable and efficient power for various chips and modules in communication equipment. The high efficiency and low temperature rise characteristics of the ZVS circuit can ensure the reliability of the power management module during long-term operation, reduce failures caused by overheating, and extend the service life of the equipment.
• Radio Frequency Power Amplifier: In the radio frequency power amplifier, ZVS technology can improve the efficiency of the power amplifier, reduce power consumption, thereby improving the transmission power and signal quality of communication equipment, and at the same time reducing the heat dissipation requirements of the equipment, which is conducive to the miniaturization and integration of the equipment.

3. Aerospace

• Aerospace Electronic System: In the aerospace field, extremely high requirements are placed on the reliability and stability of electronic equipment. The high-efficiency and low-EMI (Electromagnetic Interference) characteristics of the ZVS boost circuit enable it to provide stable power for various equipment in the aerospace electronic system, ensuring flight safety and the normal operation of the system.
• Satellite Power System: In satellite and other space vehicles, the performance of the power system is crucial. ZVS technology can be applied to the power conversion and management circuits of satellites to improve power efficiency, reduce energy losses, and at the same time reduce the electromagnetic interference on satellite communications and other electronic equipment.

4. Medical Devices

• Medical Imaging Equipment: Equipment such as X-ray machines, CT scanners, and MRI devices require stable and efficient power to drive high-voltage generators, radio frequency coils and other components. The ZVS circuit can provide high-quality power to ensure the imaging quality and stability of the equipment, and at the same time reduce the electromagnetic interference on surrounding medical equipment.
• Medical Monitoring Equipment: It is used to provide power for various medical monitoring equipment such as electrocardiogram monitors and blood pressure monitors. Its high efficiency and low noise characteristics help to improve the performance of the monitoring equipment and ensure the accuracy and reliability of the monitoring data.

5. Industrial Automation

• Control System: It provides reliable power for PLCs (Programmable Logic Controllers), industrial computers, sensors and other equipment in the industrial automation control system. The high conversion efficiency and stability of the ZVS circuit can ensure the long-term stable operation of the control system and improve the reliability and efficiency of the production process.
• Robot: In the drive system, control system and sensor system of robots, the ZVS circuit diagram can be used for power conversion and management to provide stable power support for the efficient operation of robots, while reducing energy consumption and heat dissipation requirements and improving the working performance and service life of robots.
• Motor Drive: It can be applied to the variable frequency speed regulation system of industrial motors. By improving the power conversion efficiency and reducing the switching losses, it can realize the efficient and energy-saving operation of motors, and at the same time reduce the electromagnetic interference on surrounding equipment and improve the reliability of the system.

6. Automotive Electronics

• Electric Vehicles: In key components such as the battery management system, motor drive system and on-board charger of electric vehicles, the ZVS circuit can improve the energy conversion efficiency, extend the battery driving range, and at the same time reduce the volume and weight of the system, improving the performance and competitiveness of electric vehicles.
• Hybrid Electric Vehicles: It is used in the power system and electronic control system of hybrid electric vehicles to realize the efficient conversion and management between different energy sources and improve the overall energy utilization efficiency and performance of the vehicle.
• Charging Piles: In charging piles, ZVS technology can improve the charging efficiency, reduce energy losses during the charging process, and at the same time reduce electromagnetic interference, improve the reliability and safety of charging piles, and provide guarantee for the fast and safe charging of electric vehicles.

7. Consumer Electronic Products

• Liquid Crystal Televisions: In the power board of liquid crystal televisions, the ZVS circuit can improve the power conversion efficiency, reduce power consumption and electromagnetic interference, make the TV picture more stable and clear, and at the same time reduce the heat generation of the power part and improve the reliability and service life of the TV.
• Laptop Computers: It provides efficient and stable power for the power adapters and internal power management circuits of laptop computers, which helps to extend the battery life, and at the same time reduces the heat generation during the use of the computer and improves the user experience.
• Mobile Phone Chargers: Some high-end mobile phone chargers have begun to adopt ZVS technology to improve the charging efficiency, shorten the charging time, and at the same time reduce the volume and weight of the charger, making it convenient for users to carry and use.

The ZVS circuit diagram is an efficient power conversion technology. By controlling the turn-on and turn-off timing of the switching tubes, it realizes highly efficient power conversion. The design and application of the ZVS circuit diagram are of great significance for improving the efficiency and stability of the power system.

IV. What Are the Functions of the Resonant Capacitor and Resonant Inductor in the ZVS Circuit Diagram?

1. Function of the Resonant Capacitor

In the ZVS (Zero Voltage Switching) circuit, the resonant capacitor plays a crucial role. It forms an LC resonant circuit together with the primary inductor in the circuit. The resonant frequency of this circuit is related to the parameters of the resonant capacitor and the resonant inductor. The main function of the resonant capacitor is to control the resonant frequency of the circuit to match the frequency of the input voltage, thus realizing resonant switching. If the parameters of the resonant capacitor are improperly selected, it may lead to a mismatch between the resonant frequency and the input voltage frequency, which will then affect the performance of the circuit.

2. Function of the Resonant Inductor

The resonant inductor also plays a key role in the ZVS circuit. It forms an LC resonant circuit together with the resonant capacitor. Its function is to control the resonant frequency of the circuit together with the capacitor. When the current in the circuit changes, the inductor will smooth the current change by storing and releasing magnetic energy, which makes the inductor have frequency selectivity in the resonant circuit. When the input frequency approaches the intrinsic frequency of the inductor, the impedance of the inductor will become very large, causing the current to flow through the inductor while ignoring the influence of the capacitor and resistor.

3. Joint Function of the Resonant Capacitor and Resonant Inductor

The joint function of the resonant capacitor and the resonant inductor in the ZVS circuit is to realize zero voltage switching. When the switching tube is turned off, the resonant capacitor will release the electrical energy stored in the circuit back to the input power supply, thus reducing the voltage in the circuit to zero and achieving the effect of zero voltage switching and reducing the losses of the switching tube. Therefore, the resonant capacitor and the resonant inductor play a vital role in the ZVS circuit. They can control the resonant frequency of the circuit, reduce the switching losses and improve the efficiency of the circuit.

When designing the ZVS circuit, the selection of the parameters of the resonant capacitor and the resonant inductor is very important and needs to be accurately calculated and selected according to the actual situation of the circuit to ensure that the circuit can work normally and achieve the expected efficiency.

V. How to Adjust the Resonant Frequency According to the Working Principle of the ZVS Circuit?

1. Working Principle of the ZVS Circuit

The ZVS (Zero Voltage Switching) circuit is a special switching power supply circuit. It can realize zero voltage switching during the turn-on and turn-off processes of the switching elements, thus greatly reducing the switching losses and improving the efficiency of the circuit. The ZVS circuit usually contains a resonant circuit. By adjusting the parameters of the resonant circuit, precise control of the working frequency of the circuit can be achieved.

2. Methods for Adjusting the Resonant Frequency

Adjusting the resonant frequency of the ZVS circuit usually involves changing the values of the inductance and capacitance in the resonant circuit. Specifically, it can be achieved through the following methods:

• ｒｅｐｌａｃｅ the Inductor or Capacitor: Directly ｒｅｐｌａｃｅ the inductor or capacitor elements in the circuit and choose different specifications to change the resonant frequency.
• Adjust the Connection Mode of the Inductor or Capacitor: Change the connection mode of the inductor or capacitor, such as parallel or series connection, to change their equivalent values and then affect the resonant frequency.
• Use Variable Inductors or Capacitors: Use adjustable inductor or capacitor elements, such as potentiometers or variable capacitors, to dynamically adjust the resonant frequency.

3. Experimental Verification

In actual operation, the effect of adjusting the resonant frequency can be verified by building an experimental circuit. For example, a ZVS circuit can be built on a breadboard, and then the values of the inductance and capacitance in the circuit can be changed to observe the change in the working frequency of the circuit. Through the recording and analysis of experimental data, the effectiveness of the adjustment method can be verified and the circuit design can be further optimized.

4. Precautions

When adjusting the resonant frequency of the ZVS circuit, the following points need to be noted:

• Maintain Circuit Stability: During the adjustment process, it is necessary to ensure that other parameters of the circuit will not be adversely affected due to the change in the resonant frequency, so as not to affect the stability and safety of the circuit.
• Avoid Too Low Resonant Frequency: If the resonant frequency is too low, it may lead to unstable operation of the circuit or even failure to start.
• Consider the Actual Application Scenario: In actual applications, factors such as the working environment and load conditions of the circuit also need to be considered, and an appropriate resonant frequency should be selected to ensure the performance and efficiency of the circuit.

Through the above methods, the resonant frequency can be adjusted according to the working principle of the ZVS circuit to meet different application requirements.

VI. Comparison between ZVS Circuit and PWM Circuit

1. Advantages

Low switching losses: The ZVS (Zero Voltage Switching) circuit can perform switching operations when the voltage of the switching tube drops to zero, thus significantly reducing the switching losses and improving energy efficiency.

• Low Switching Noise: Due to the relatively small fluctuations in voltage and current during the switching process, the switching noise of the ZVS circuit is also relatively low.
• Reduced Electromagnetic Interference: The switching process of the ZVS circuit is smoother, reducing electromagnetic interference, which is beneficial to improving the stability and reliability of the system.
• Simple Circuit Structure: The design of the ZVS circuit is relatively simple and easy to implement and maintain.

2. Disadvantages

Poor load adaptability: Under light load conditions, the ZVS circuit may have difficulty in realizing zero voltage switching and may need to increase the resonant inductor to achieve it, which may affect the flexibility and efficiency of the system.

• Duty Cycle Loss: Due to the existence of leakage inductance or the addition of a resonant inductor, duty cycle loss may occur, which will then affect the performance of the system.
• Large Primary Side Circulating Current: The ZVS circuit may generate a relatively large circulating current on the primary side, increasing the conduction losses of the system and reducing the efficiency.
• Voltage Spikes and Oscillations: Leakage inductance and secondary side rectifier diodes and capacitors may generate voltage spikes and oscillations, further reducing the efficiency of the system.

In summary, the ZVS circuit has advantages in terms of switching losses, noise, electromagnetic interference and circuit structure, but has disadvantages in terms of load adaptability, duty cycle loss, primary side circulating current and voltage spikes. The choice of which circuit depends on the requirements and limitations of specific application scenarios.