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UC2844: uc2844 problem

Carl Shen
Prodigy 230 points
Part Number: UC2844

We are using a Ti switching power supply chip: uc2844. Input voltage: 86 ~ 260vac, output voltage: 24VDC, load: 15 ~ 20W, now the ring temperature test (25 ℃) with 15W, the maximum temperature rise of the chip after normal operation has reached 90 ℃.

The switching frequency of the chip is 100kHz, the driving resistance is 24 Ω, the MOS tube is n-channel MOS tube 900v / 15a, and the peripheral circuit is shown in the attachment (please do not send the picture).

  • 0
    TI__Mastermind 33115 points

    Hi Carl,

    Thanks for connecting through E2E.How are you determining that the UC2844 is reaching 90C?  If you have not already done this, I would recommend measuring the case temperature of the UC2844 with a thermocouple temperature probe to validate board temperature measurement or thermal imaging. If you are convinced the UC2844 case temperature is in fact 90C, this is not normal for 25C ambient. Does the temperature change between no load to full load, minimum to maximum input voltage? Can you measure VCC and ICC to determine the power dissipation? Measure VCC, OUT, ISENSE and VREF with an oscilloscope and provide waveforms, if possible?

    Also, you requested "not to send" the schematic. Please be aware that E2E is a public forum, sharing information for learning purposes. Everything you post on E2E is public and can be viewed by all who have an account.

    Regards,

    Steve M