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UC2825: Reason for temperature increase

Satoshi
Guru 19645 points
Part Number: UC2825

One customer is evaluating UC2895, but IC temperature is increase about 70℃（Ta: 20℃ ⇒90℃）.

Please let me know about two points below;

①How to calculate IC's power dissipation  

②Idea for decrease temperature (= IC's power dissipation)

　Are Vin or fsw decrease, good effect?

UC2895 condition and information are below;

・Vin: 24V, fsw: 100kHz, Duty: 50% (Push-Pull)

・FET: 2SK3608-01S (Datasheet is attached)

2SK3608-01S.PDF

・Diode: RF081M2STR (Datasheet is attached)

RF081M2S.pdf

・Transformer: custom

・Any protection function are not detect

・High temperature is only UC2825.

　Board, FET, and the other components are not high temperature.

If there need detailed information, please let me know e-mail.

Best regards,

Satoshi

  • 0
    TI__Genius 13660 points
    Hi Satoshi,

    IC's total dissipation is Pd=Vcc * Ivcc. Although quiescent Vcc current is only 1.1 mA, the total supply current is higher, depending on the OUT current. Total Vcc current (Ivcc) is the sum of quiescent current and the average OUT current (Iout). Knowing the operating frequency and the MOSFET gate charge (Qg), average OUT current (Iout) can be calculated from Equation: Iout = Qg × fsw.
    For accurate power dissipation, you can directly measure voltage Vcc pin and current into Vcc pin, then multiplies.
    So according the equation PD, we can try to decrease operating frequency fsw and select a mosfet with a small Qg, and decrease Vcc voltage but must be in recommended range.

    Regards,
    Teng