How to reduce the interference of core power transformers for audio power amplifier circuit
How to reduce the interference of core power transformers for audio power amplifier circuit - 2019 03 - 30 15:05:22 power transformer can be formed by magnetic field, electromagnetic induction and the circuit of amplifier interference, is sound interference sources in the machine. So, to deal with its working status and application environment, can effectively avoid the interference generated by the iron core power transformers, the amplifier to get excellent sound effects. 1, the core power transformers except for the power amplifier, also can amplifier and power supply coupled up, make the interference sources in the grid into the amplifier, at the same time, it will reflect changes in the current and voltage produced by the amplifier power grid. In order to cut off the winding between electrostatic field and capacitive coupling, isolation and common-mode rejection of interference, avoid the common-mode voltage of the grid or circuit coupled to the secondary or primary, the sound of Faraday electrostatic shielding with core of power transformer winding is key. This block can be alternating layers of copper foil, can also be a complete closed structure, anyhow for winding ( Especially to the primary winding) Surrounded by the more, the better the common-mode rejection. 2, the magnetic field generated by the iron core power transformer interference has been puzzled amplifier quality improve, even if there is the pure power, from its magnetic field induction can also cause amplifier quality serious decline. Because of the high price of magnetic shielding isolation cover, Even higher than the iron core transformer itself, which is why some imported iron core transformer high price) , the general domestic machine is rarely used magnetic shielding isolation cover to cut off the transformer magnetic disturbance, many just use simple iron cage, or even simply install the transformer bare, so cannot effectively magnetic shielding. Foreign high-quality iron core transformer often use multilayer manganese alloy and crude copper layer and structure, the transformer surrounded, on the one hand using manganese swim and the characteristics of high resistance, high permeability magnetic short circuit, on the other hand caused by copper layer within a contrary to interfere with the magnetic field of magnetic field eddy current degaussing interference, thus greatly reduced the magnetic field of transformer were leaked. Amateur conditions is difficult to get mumetal cover, but also can use 1. 5 mm made of soft iron and copper multilayer structure of magnetic shield. 3, when the iron core transformer primary impedance is equal to the source resistance value reflection of resistance in parallel with the load, there will be a low frequency cutoff, increase is the result of iron core transformer noise, so the core power transformers also must have enough inductance. But it doesn't become blind increase iron-core transformer output power of reason. Is because, iron core transformer inductance change with iron core magnetic flux density, and the secondary load power hour, core magnetic flux density will decrease, bring down the inductance. In general, the core of power transformer power can be in the secondary power supply power of 1. 4 - Choose between 2 times, more appropriate. 4, high quality of transformer core permeability is very high, magnetostrictive effect is also very high, is sensitive to external magnetic field, the influence of pressure, vibration, to generate additional voltage, thus causing interference. Therefore, in the assembly or installation of the transformer, to take the following measures: iron core or block must be demagnetized before assembly. Avoid iron core short-circuit, produce eddy current, reduce the magnetic flux, decreased inductance. Transformer should be vacuum impregnation, making laminated can't each other. The transformer to be installed on a bed of shock absorption, any magnetic field source is suspension installation. If the installation space allows, for acoustic isolation transformer should be. 5, in the form of a transformer to reduce the interference is also very important. Generally, ring or O type iron core transformer with high efficiency, magnetic flux leakage is small, but magnetic flux saturation, easily hurt to resist the interference of power grid. EI type iron core transformer, on the other hand, and because there is a certain air gap, can make the core permeability stability. R type transformer, between the two. Because, power grid pollution more serious in our country, so many & other; Enthusiasts throughout the &; More chose the EI type transformer as an audio power supply.