In modern electronic devices, switching power supplies are widely used in the form of power supply, which has the characteristics of small size and high efficiency.
However, switching power supplies also generate harmonics, which affect the quality of power supply and the stability of power grid to a certain extent, and even cause harm to circuits and devices. Therefore, it is imperative to solve the problem of switching power supply harmonics.
Causes of switching power supply harmonics
Harmonic refers to a kind of electrical waveform with a higher frequency than the fundamental wave, and the source generally comes from factors such as nonlinear load, non-sinusoidal voltage and electromagnetic interference. The working principle of switch mode power supply determines that it is easy to generate harmonics.
1.Short-circuit effect of capacitor filter circuit
In switch mode power supply, capacitor filter circuit mainly plays the role of reducing the pulsating voltage on the power supply output, but under high frequency conditions, capacitor is also a short circuit. Short circuit will cause harmonic current to flow into the power supply, generate oscillation in the conductor, and cause noise and thermal effects.
2.Resonance effect of inductor filter circuit
In switching power supply, inductor filter circuit is mainly used to prevent high-frequency pulsation of power supply output. When the load current is very low, the inductor is in a resonant state, which will generate high-frequency harmonic current.
The high-frequency harmonic current generated will cause resonance in the power supply capacitor and line inductance, and generate high-frequency oscillation when the current flows.
3.Resonance effect of inductance 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 conditions so as to adjust the power supply output in time and improve the efficiency of the entire circuit.
However, the inductance feedback circuit will reduce the output voltage of the power supply through the resonant circuit, increasing the generation of harmonic current.
4.Influence of operating 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 generate relatively large electromagnetic waves on the coil, which will cause the electrical appliance itself and the electromagnetic waves to be full of mutual influence in the air.
Hazards of switching power supply harmonics
switch mode power supply harmonics will cause harm to both equipment and systems. The specific hazards are as follows:
1. Harm to the switching power supply itself
The harmonics generated by the switching power supply at high frequencies will increase the internal heat consumption of the switching tube, increasing the risk of damage.
2. Harm to the load
The output harmonics of the switching power supply will affect the load and easily damage the components in the circuit, especially the precision instruments and medical equipment.
3. Harm to the power grid
After the switching power supply outputs harmonics, it will propagate through the power grid, increase the harmonic current of the power grid, cause power grid overload, cable temperature rise, power transformer core damage and other problems, thus affecting stability.
Solutions to harmonics in switching power supplies
In order to better solve the harmonic problem of switching power supplies, the following solutions are usually adopted:
1. Use harmonic suppression circuit
The use of harmonic suppression circuit can limit the generation of high-frequency current and effectively reduce the impact of harmonic current on switching power supplies.
2. Use new filters
The new filters have a good solution effect on the harmonic problem of switching power supplies, such as the use of non-inductive topology circuits, multi-capacitor-multi-parameter filters, etc.
3. Improve the design of switching power supplies
In the design of switching power supplies, 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 the switching power supply, the generation and impact of harmonic current can be effectively reduced.
In short, the generation and harm of switching power supply harmonics are inevitable, and the problem can be effectively solved as long as certain technical measures are taken.
Therefore, in the use and design of switching power supplies, the harmonic situation must be fully considered, and correct and effective solutions must be adopted through brainstorming to ensure the working efficiency of modern electronic equipment and the stability of the system.
