The Significance Of Current Sense Resistor In Change Mode Power Supply

1. The current sense resistor is normally found in the switch mode power supply section. A more recent variation of monitor-the b+ (increase) circuit also has this current sense resistor. If you repair electronic equipment especially the switch mode power supplies, the current picking up resistor is linked to the source pin of power FET (field effect transistor) and the other end to HOT GROUND. The value of the current sense resistor is in the variety of 0.1 ohms to about 1 ohm. The values depend upon the style of each power supply. In monitor power supply where pulse width modulation (PWM) IC UC3842 are utilized. Pin 3 of this power ic is called I-sense which implies current sense and this pin is linked to source pin of POWER FET. The purpose of this current sense circuit is for overcurrent security. This circuit generally samples the voltage drop throughout a resistor in series with the changing FET transistor. If the current increases abnormally due to some short circuit in the secondary side such as a shorted secondary diode or horizontal output transistor (HOT), the voltage will go beyond a referral level and shut down the pulse generator which is the PWM IC. This circuit supplies security to components in the event a problem happens. In many cases where overload happen-the power section will blow and the majority of the time the elements altered are the fuse, power feed, PWM IC, Zenner diode and current sense resistor. Do you know that a small change in this current sense resistor worth have an excellent effect on the secondary output? A little change in value say from 0.22 ohm to 0.44 ohm can cause your output voltage to drop into half! I have seen a lot of repairers can't spot this kind of issue (low output voltage) due to that they utilized an analog or digital meter that doesn't have the low ohms vary. If the low ohms resistor has its worth changed by utilizing regular meters, you can't differentiate. I personally utilize the Cock Smith ESR Meter which has the capabilities to examine resistor value down to 0.01 ohm! If you do not have this the unique meter you might just direct replace the current sense resistor to see if the created secondary output will back to typical voltage. Another tip is that if the current sense resistor in the screen B+ circuit has altered the worth it will cause the output in the boost circuit to become low and you will have a small width screen and of course, the high voltage will become low. Instead of 24Kv, it becomes 15-18Kv. The current sense resistor is usually found in the switch mode power https://shunts.com supply section. If you fix electronic equipment specifically the switch mode power products, the current sensing resistor is connected to the source pin of power FET (field result transistor) and the other end to HOT GROUND. The value of the current sense resistor is in the range of 0.1 ohms to about 1 ohm. In some cases where overload happen-the power area will blow and many of the time the parts changed are the fuse, power feed, PWM IC, Zenner diode and current sense resistor.