A flyback converter is a circuit topology commonly used for auxiliary power supplies. Its advantage is that it can work in a very wide input voltage range, the circuit is simple, the components are few, but the efficiency is generally around 75%. Although switching power supplies operate at frequencies far beyond the human hearing range, they still produce audible noise under certain load conditions. The possible sources of audible noise are diverse. Noise can be caused by design defects (such as oscillating output voltage) or by noise components such as capacitors or transformers. In some cases, the sharp, harsh noise or hum that you hear may be like a fan swaying at an abnormal frequency, or because the power supply is close to an external EMI source (fluorescent or power strip).
This article explores the most common sources of noise in flyback power supplies and presents possible solutions. All of the operating procedures described below can be accomplished using a programmable AC power supply or autotransformer and an electronic load. Keep in mind that in some cases, the noise level produced by your power supply can be very low, and if the power supply is to be used in a sealed enclosure, audible noise will not pose a problem.
Possible noise source
The most common source of noise in flyback power supplies is the noise component. This noise is usually generated by a ceramic capacitor or a ferrite transformer core. The noise in ceramic capacitors is usually caused by the reverse piezoelectric effect. When a voltage is applied to the dielectric structure, mechanical stress or strain is induced, causing deformation of the material. When this material is deformed, the surrounding air is discharged, causing noise.
Since reverse piezoelectric effects occur when large voltage swings occur, designers can focus on finding ceramic capacitors with higher dV/dt swings. In a typical power supply, these capacitors include snubber capacitors, clamp capacitors, and ceramic output capacitors. To quickly determine if a ceramic capacitor is producing noise, replace it with a metal film capacitor with the same capacitor value and appropriate voltage rating. . If the noise level drops, you have found a source of noise in the circuit.
If the noise source is a clamp capacitor, you can replace it completely with a metal film capacitor, or try a ceramic capacitor with a different dielectric material. Another method is to replace the clamp capacitor being used, for example, by replacing it with a Zener clamp circuit. If the noise problem is due to a snubber capacitor, it can be replaced with a metal film capacitor, or the value of the series resistor can be increased to reduce the dV/dt noise on the capacitor. You can also use ceramic capacitors from other media to see if the noise is reduced.
Manage transformer core noise
On the other hand, the noise generated by the transformer core is usually caused by magnetostriction, which is similar to the reverse piezoelectric effect. Many ferromagnetic materials change shape when subjected to a magnetic field. As the magnetic field in the transformer core changes, such materials can cause physical vibration of the core. When the vibration frequency reaches the mechanical resonance frequency of the transformer, the vibration is amplified and causes greater audible noise. In AC electrical equipment (such as transformers that use a 60 Hz applied magnetic field), the maximum length change occurs twice per cycle, producing a familiar 120 Hz noise.
If this problem occurs with your design, first make sure it is not caused by improper design before you begin troubleshooting. First, verify that the supplied input voltage and output load meet the design specifications. If the operating voltage of the power supply is lower than the specified minimum input voltage or higher than the specified output load, then some of the AC cycles will lose regulation, which will cause the magnetic flux in the core to increase and generate noise.
storage systems, Solar Battery generator, Portable Solar Power System, solar energy systems, mobile solar energy generator, solar power generator, solar energy generator
| portable solar power system |
Portable Solar Power System
lithium solar battery, solar portable generators, inverter portable solar generator, portable solar system, solar home system
Delight Eco Energy Supplies Co., Ltd. , https://www.cndelight.com