PCB Fabrication

Three simple current detection circuits

by:A-TECH      2021-03-30
In power supplies and other equipment, current detection or feedback is usually required. Current detection usually uses a series sampling resistor to amplify the voltage on the resistor through an amplifier. If you want to improve the detection accuracy, you often need to use a more expensive instrumentation amplifier. The offset voltage of the op amp is relatively large. Here are some ingenious and cheap current detection circuits 1. Triode current detection circuit If you simply use the transistor on and off to detect the current, the transistor needs to be turned on at about 0.7V, and when the current is relatively small, a larger resistor is required in series. At the same time, a large feedback voltage is wasted. As shown in the above method, a relatively small resistor can be used, and the current I can be detected with a small voltage consumption. The sensitivity of the detection can be adjusted by adjusting the resistance of the transistor base machine. This circuit can be used in chargers and other places that need to show whether there is charging current. 2. High-sensitivity current detection circuit This circuit uses two diodes for current sampling. The sensitivity is very high, and the current can achieve a large dynamic range. It is more suitable for high-power or high-voltage applications. The disadvantage is that the voltage needs to be damaged by about 1.4V. . 3. TL431 current feedback circuit TL431 is inexpensive and is widely used in the feedback loop of switching power supplies, but its FB voltage is 2.5V. When directly used as current feedback, a large sampling resistor is required and voltage is wasted. In the figure, two TL431s are used to achieve current feedback, and a relatively small sampling resistor can be used to achieve precise current feedback. If there is a voltage feedback network, then the voltage feedback circuit of U3 is combined. Here to enter the pricing page https://www./online/
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