The uc3845 driver high boost circuit does not work

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The uc3845 driver high boost circuit does not work [Copy link]

 

Dear brothers, recently I was working on the uc3845 driver circuit and initially used a signal generator to supply it. The main circuit will move, but after switching to uc3845, the duty has been unable to be controlled and maintained at 50% full duty. There is no way to automatically control the duty. Is there something wrong with the input 40v and the output 400v vo/vi=2+n/1? -D I set the number ratio to 1:4 duty40%

qwqwqw2088

Is the power supply voltage of UC3845 enough? The chip is not working

maychang

Your UC3845 is only powered by R16, R17, and R18, which is not enough. Even if your power supply voltage is 40V, it cannot be powered directly by Vcc, let alone such a large resistor connected in series with Vcc. To power the chip, you need to refer to the typical application circuit in the UC3845 manual.

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qwqwqw2088 Published on 2018-2-27 18:38 Is the power supply voltage of UC3845 enough? The chip is not working

I can’t reach 15v, so I can use 7815 to stabilize the voltage. Thank you

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maychang published on 2018-2-27 19:22 Your UC3845 is only powered by R16, R17, and R18, which is not enough. Even if your power supply voltage is 40V, it cannot be powered directly by Vcc, let alone...

Thanks for the technical reply

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maychang published on 2018-2-27 19:22 Your UC3845 is only powered by R16, R17, and R18, which is not enough. Even if your power supply voltage is 40V, it cannot be powered directly by Vcc, let alone...

Please tell me, the frequency of uc3845 is normal but the duty can only be 0.xx% from the beginning. What is the problem?

qwe3319543

maychang published on 2018-2-27 19:22 Your UC3845 is only powered by R16, R17, and R18, which is not enough. Even if your power supply voltage is 40V, it cannot be powered directly by Vcc, let alone...

Please tell me, my duty cannot be fully activated and the boost action is only 0.xx%. Is this normal? What is the problem?

maychang

qwe3319543 Published on 2018-3-24 14:09 Please tell me, my duty cannot be fully turned on and the boost action is only 0.xx%. Is f normal? What is the problem?

You mean that the duty cycle is very small, which seems abnormal. First measure whether the output voltage is normal (in line with design requirements). If the output voltage is as designed, then possible problem areas are R1 and R2, and R12 and R13.

qwqwqw2088

qwe3319543 Published on 2018-3-24 13:10 I can’t get it to 15v. I can just use 7815 to stabilize the voltage. Thanks

I can’t get it to 15v because the power supply is not normal and the chip is not working.

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qwqwqw2088 published on 2018-3-25 21:53 There is no way to reach 15v. The power supply is not normal and the chip does not work.

It is because we use a large power supply of 40v. In the past, the voltage supplied to 3845 needed to be reduced, so we used 7815. Now it will operate normally, but there is a problem with the duty. One-sided 3845 is No problem, but after connecting all the circuits, the duty is very low or 99%.

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maychang published on 2018-3-24 15:20 What you mean is that the duty cycle is very small, which seems abnormal. First measure whether the output voltage is normal (in line with design requirements). If the output voltage is in line with the design...

But the duty is too low, how can it rise? I just gave the 3845 15v and asked it to operate. It is normal to see pin 6, but in all the circuits, only the frequency and voltage are normal, and the duty part is not 0. % is 99%

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I would like to add that the 3 angles cannot stabilize the 1v triangle wave. There seems to be a surge. How to solve it?

maychang

qwe3319543 Published on 2018-3-26 18:10 But the duty is too low, how can it rise? I just gave 3845 15v and asked it to operate. It is normal for pin 6, but the whole circuit only has frequency voltage...

"First measure the output voltage to see if it is Normal (in line with design requirements).” I asked this question the day before yesterday, and I haven’t received a reply to this day.

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maychang published on 2018-3-26 19:19 "First measure whether the output voltage is normal (in line with the design requirements)." I asked this question the day before yesterday, and I haven't received a reply to this day.

Is the output voltage the main circuit high boost or the 3845? Because the duty is too low, the output voltage cannot rise at all, which is abnormal.

maychang

qwe3319543 Published on 2018-3-27 14:52 Is the output voltage of the main circuit high boost or 3845? Because the duty is too low, the output voltage cannot rise at all, which is abnormal

Your circuit load is R6, R7, R8, R9, R10, R11 and R12. The output voltage should refer to the voltage from the upper end of R6 to the lower end of R12, which is the voltage across C5.