What is the normal value of the DS pole resistance of the mosfet tube?

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What is the normal value of the DS pole resistance of the mosfet tube? [Copy link]

 

When the GS of a brand new MOS tube is short-circuited, the resistance of the DS pole measured by a multimeter is infinite (the positive pole of the resistance scale is connected to D, and the negative pole is connected to S. The following resistances are all measured in this way).

The power amplifier of the vibration table uses IRFP260M tubes. Five tubes are connected in parallel to form a half bridge, and 20 tubes are connected in parallel to form an H-bridge circuit.

The tube is welded on the power amplifier module. When the DS inter-electrode resistance is measured when it is new, the multimeter reading is infinite. When the DS inter-electrode resistance is measured with a digital meter with a range of 220M, it is still infinite.

Some power amplifier modules have been used for more than ten years, and the inter-electrode resistance of DS is infinite.

Some amplifier modules can work normally even if the DS inter-electrode resistance is only 2M, and there will be no operation errors or fault shutdowns. Recently, a module with a DS resistance of 0.5M was measured and it can also be turned on and run.

The positive and negative power supplies of the power module are 200V. The output current of the power amplifier of one module is 50A. Two modules in one power amplifier box can output 100A. A cabinet can hold up to 7 boxes and can output a maximum current of 700A.

I don't understand why some power amplifier tubes can operate normally with only 2M ohm resistors.

吾妻思萌

The voltage difference between DS can activate the carrier channel.

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Each brand or model should be different because of different processes

For example, for a high-power tube like IRFP260M, its on-resistance is usually between tens of milliohms and hundreds of milliohms.

But when designing a circuit, for example, if you choose this type of tube, you still need to refer to the data sheet of this model according to the numerical requirements.

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The resistance value of 0.5M ohms is relatively low,

This indicates that the MOS tube in use has been degraded or damaged to some extent.

Although it may still work, its performance may be degraded, leakage current may increase, and subsequently, power loss and thermal issues may occur.

This is the only way to analyze it.

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When the bridge amplifier circuit of the power amplifier is just powered on, the four tubes are cut off, and the half-bridge is equivalent to two infinite resistors in series. In the ideal situation, the middle potential points O1 and O2 of the half-bridge are half of the power supply voltage, and the output of the power amplifier is 0.

When the actual DS inter-electrode resistance is not infinite, the inter-electrode resistance value measured by a multimeter is uncertain. How can the voltage division be the same when the two tubes of the half-bridge are cut off when the power is turned on?