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There Are So Many Resistors. How To Choose Resistors In Power Design?
Jul 19, 2018

Surge limiting resistors can limit the amount of surge current that AC-DC power may cause during the first connection and charging of energy storage capacitors. These resistors usually have low resistance and are connected in series with AC power lines. For higher power sources, negative temperature coefficient (NTC) resistors are usually used to achieve this purpose. The resistance values of these resistors fall with their own heating. One drawback of using such resistors is that the temperature must be kept constant during work to ensure low resistance. The third option is to use pulse-resistant resistor, which is usually in the form of Joule. It can better describe its function than the normal continuous power scale with tile.

The high voltage divider is used to provide feedback to the regulating circuit. These resistors usually have other secondary functions, such as monitoring the high voltage power supply in the defibrillator, charging the energy storage capacitor and turning off the power at the desired charge level.

High current detection is used to measure the power supply current. This measure adopts the principle of shunt ammeter. It needs to connect a low value resistor and measure the pressure drop on it to calculate the current size. In this kind of circuit design, the selection of resistance must be taken into consideration. On the one hand, low resistance is required to minimize heat and power consumption. On the other hand, high impedance is required to facilitate measurement.

In a word, resistance selection in almost all power supply designs has different characteristics priority and performance requirements, including resistors that require high voltage, high current and high power, and low tolerance resistors. Resistance is usually required to have specific properties, such as surge suppression or negative TCR.