The Significance Of Current Sense Resistor In Switch Mode Power Supply

1. The current sense resistor is normally located in the switch mode power supply area. A newer version of monitor- the b+ (boost) circuit also has this current sense resistor. If you fix electronic devices specifically the switch mode power supplies, the current noticing resistor is connected to the source pin of power FET (field impact transistor) and the other end to HOT GROUND. The value of the current sense resistor remains in the variety of 0.1 ohms to about 1 ohm. The worths depend upon the design 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 means current sense and this pin is linked to source pin of POWER FET. The function of this current sense circuit is for overcurrent defense. This circuit usually samples the voltage drop across a resistor in series with the switching FET transistor. If the current increases unusually due to some short circuit in the secondary side such as a shorted secondary diode or horizontal output transistor (HOT), the voltage will surpass a referral level and shut down the pulse generator which is the PWM IC. This circuit supplies protection to parts in the event an issue takes place. In some cases where overload happen-the power shunts.com section will blow and the majority of the time the parts changed 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 value have a great effect on the secondary output? A little change in value say from 0.22 ohm to 0.44 ohm can trigger your output voltage to drop into half! I have actually seen a great deal of repairers can't discover this kind of problem (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 altered by using typical meters, you can't separate. I personally use the Cock Smith ESR Meter which has the abilities to examine resistor worth down to 0.01 ohm! If you don't have this the unique meter you may just direct change the current sense resistor to see if the generated secondary output will back to regular voltage. Another suggestion is that if the current sense resistor in the screen B+ circuit has altered the worth it will trigger the output in the increase circuit to become low and you will have a small width screen and of course, the high voltage will end up being low. Rather of 24Kv, it ends up being 15-18Kv. The current sense resistor is normally located in the switch mode power supply area. If you repair electronic equipment particularly the switch mode power supplies, the current noticing resistor is connected to the source pin of power FET (field impact transistor) and the other end to HOT GROUND. The worth 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 most of the time the elements changed are the fuse, power feed, PWM IC, Zenner diode and current sense resistor.