How to Solve the Harmonic of Switching Power Supply?

In modern electronic equipment, switching power supply is a widely used form of power supply, which has the characteristics of small size and high efficiency. 

However, the switching power supply will also produce harmonics, which will affect the quality of the power supply and the stability of the grid to a certain extent, and even cause harm to the circuit and device. 

Therefore, it is imperative to solve the harmonic problem of switching power supply.

Causes of harmonics in switching power supplies:

Harmonic refers to a higher frequency than the fundamental wave waveform, the source is generally from nonlinear load, non-sine wave voltage and electromagnetic interference and other factors. 

The working principle of switching power supply determines that it is easy to produce harmonics.

1. Short circuit of capacitor filter circuit

In the switching power supply, the capacitor filter circuit mainly plays the role of reducing the pulsating voltage on the output of the power supply, but at high frequency conditions, the capacitor is also a short circuit.

The short circuit will cause the harmonic current to flow into the power supply, produce oscillation in the conductor, and cause noise and thermal effects.

2. Resonance of inductor filter circuit

In the switching power supply, the inductor filter circuit is mainly used to prevent the output of the power supply from high-frequency pulsation, when the load current is very low, the inductor is in a resonant state, which will produce high-frequency harmonic current.

The generated high frequency harmonic current will cause the capacitor of the power supply and the inductance of the line to resonate, and produce high frequency oscillation when the current flows.

3. Resonance effect of inductive feedback circuit

The resonant feedback circuit is an important performance feature of the switching power supply. The feedback controller is used to continuously monitor the load and power supply, so as to adjust the power output in time and improve the efficiency of the whole circuit.

However, the inductive feedback circuit will reduce the output voltage of the power supply through the resonant circuit, which increases the generation of harmonic current.

4. The effect of working frequency

The higher the operating frequency of the switching power supply, the higher the harmonics, and the richer the harmonic current generated.

The high-frequency current will produce a relatively large electromagnetic wave on the coil, which will lead to the electrical appliance itself and electromagnetic waves filled with the phenomenon of mutual influence in the air.

The harm of switching power supply harmonics

Switching power supply harmonics will cause harm to equipment and systems.

What are the dangers of harmonics in switching power supplies? 

The specific hazards are as follows:

1. Damage to the switching power supply

The harmonics generated by the switching power supply in the case of high frequency will increase the internal consumption and heat of the switching tube, which will increase the risk of damage.

2. The load is damaged

The output harmonics of the switching power supply will affect the load, which is easy to damage the components in the circuit, especially for precision instruments and medical equipment.

3. Damage to the power grid

After the harmonic output of the switching power supply, it will spread through the power grid, increase the harmonic current of the power grid, resulting in power grid overload, cable temperature rise, power transformer core damage and other problems, thus affecting the stability.

What is the best solution to reduce harmonics?

In order to better solve the harmonic problem of switching power supply, the following solutions are usually used:

1. Adopt harmonic suppression circuit

By using harmonic suppression circuit, the generation of high frequency current can be limited and the influence of harmonic current on switching power supply can be reduced effectively.

2. Adopt new filter

The new filter has a good effect to solve the harmonic problem of switching power supply, such as non-inductive topological circuit, multi-capacitance-multi-parameter filter and so on.

3. Improve the design of switching power supply

In the design of the switching power supply, its electronic components, wiring forms and composite materials should be optimized to minimize its internal energy loss and energy degradation, and reduce the generation of harmonics.

4. Install energy-saving appliances or increase output voltage

By installing energy-saving appliances or increasing the output voltage of switching power supply, the generation and influence of harmonic current can be effectively reduced.

In short

Harmonic generation and harm of switching power supply is inevitable, as long as certain technical measures can be taken to effectively solve the problem. 

Therefore, in the use and design of the switching power supply, it is necessary to fully consider the harmonic situation, and brainstorm a correct and effective solution to ensure the efficiency of modern electronic equipment and the stability of the system.