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Dongguan Jiuqi Industrial Co., Ltd.
Contact: Mr.liang
Mobile: +86-13122876672
Tel: 0769-81818179
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Features and selection of power adapter components
| Features and selection of power adapter components |
| In the power adapter, the voltage and current waveforms are all abrupt pulse states, and the voltage or current borne by the components is not only the power supply voltage added to the components, but also the inductive voltage caused by the inductance in the circuit and the charging current of the capacitor, which makes the selection of components complicated. In fact, the power adapter is an AC/DC or DC/DC converter with the function of voltage stabilization, even though the so-called DC/DC transformation. In the actual process, DC is inverted into AC in pulse state, and then converted into DC voltage by pulse rectification and filtering. In this process, the requirements of rectifying and filtering components and power frequency rectifying circuit are greatly different. The maximum value, average value and effective value of power frequency sine wave ac power supply have a fixed proportional relationship according to the sine function, and the rated parameters of components can be calculated very accurately. However, the relationship between the values of pulse wave, voltage and current is not invariable, but varies greatly with the pulse wave and the nature of load. Even if the integral method is used to calculate the average value of the pulse waveform, the pulse waveform is required to have a certain rule, and the instability of the waveform amplitude and time relationship makes the calculation difficult to be accurate. In particular, the quantitative measurement of pulse waveform is beyond the accurate measurement of general simple instruments. In addition to the pulse oscilloscope, there is no simpler way, such as the reverse voltage value of the power adapter. In some cases, it is more difficult to measure the effective value of the pulse. For example, an RMS of 6.3v is required to power a CRT filament with a row-reverse pulse, and there seems to be no other way to measure it accurately than by using a magnetoelectric meter made up of thermocouple sensors or a high-frequency electric meter. In other words, it is impossible for components working in the pulse circuit to select their performance through measured voltage and current parameters. As for the theoretical calculation, it can only reach the degree of approximate estimation. The most obvious example is a single-ended switching circuit, whose power adapter backvoltage is theoretically calculated to be twice the maximum input voltage. In practice, the pulse waveform added to the collector of the power adapter is affected by the lumped and distributed parameters of the energy storage inductance and the nature of the power load, and the reverse voltage of the power adapter will exceed the theoretical value. Because the induction potential of inductance coil is not only a function proportional to the change of current, but also inversely proportional to the time when the current changes. In addition, the distribution parameter of inductance coil -- J. Therefore, no matter the passive element or the device in the pulse state, its performance choice is different from the ordinary analog circuit. |
| | release time：2019.10.18 Source： |
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