Knowledge: What Is Wirewound Resistors?

Wirewound resistors are made of copper, manganese or nickel-chromium alloy wire wound around the ceramic skeleton of a resistor, there will be a protective paint or glass glaze on the surface.

The advantages of wirewound resistors are low noise, no current noise and non-linearity. Small temperature coefficient, good stability, accuracy can reach 0.5% -0.05%, wirewound resistors can be used for high frequency. The shortness is poor high-frequency characteristics.

Wirewound resistors are resistors wire wrapped around the insulation skeleton and then insulated package processed. The resistance wire generally uses a certain resistivity of nickel-chromium, manganese and other alloys to make, insulation skeleton generally use ceramic, plastic, coated metal frame insulation. This kind of resistors has a small temperature coefficient, high accuracy. Among the wirewound resistors, there is a high power wirewound resistor made of ceramic, coated with a glaze or other heat-resistant and heat-dissipating insulating material on the outer surface of the resistor.

There is also an adjustable wire wound resistor in the wirewound resistors, which is wound on the outside with removable snap rings as contacting leads, with a long and narrow window above the glaze, revealing wire wound channel, snap ring move by contacting contact to adjust the resistance, it is an adjustable resistor. There are two common types of wirewound resistors: glazed wirewound resistors and enameled wirewound resistors.

Wirewound resistors are used in mobile phone chargers. Wirewound resistor value is accurate, in theory, unless it is to do the charger output voltage reference, the general charger does not use wirewound resistors, mobile phone charger circuit is SMPS switching power supply circuit, high-voltage side signal generating circuit has higher requirement, it is impossible to use wirewound resistors, otherwise it will lead to self-oscillation to impact oscillation frequency, so that the output fluctuations, only the low-voltage end uses sampling reference circuit that may use wirewound resistors ...... A cell phone charger circuit is not high precision electrical, do not need to calculate the capacitance and inductance of the PCB board into it, and the switching power supply itself has very large fluctuations, a wirewound resistor filtering effect is minimal.