STK57FU391A-E データシートの表示（PDF） - ON Semiconductor

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STK57FU391A-E

PFC converter + 3-phase Inverter Power H-IC for 3-phase Motor Drive

ON Semiconductor 

STK57FU391A-E

Cb capacitor value calculation for boot-strap circuit (Cb)

Calculate conditions

Parameter

Upper side power supply.(VD)

Total gate charge of output power IGBT at 15V.(Qg)

Upper side power supply low voltage protection.(UVLO)

Upper side power dissipation.(Idmax)

Value

15[V]

0.132[μC]

12V

400[uA]

Capacitance calculation formula

Tonmax is upper arm maximum on time' equal the time when the Cb voltage falls from 15V to the upper limit of 'Low

voltage protection level.

“ton-maximum" of upper side is the time that Cb decreases 15V to the maximum low voltage protection of the upper side

(12V).

Thus, the following formula  is true.

VD x Cb – Qg – Idmax x tonmax = UVLO x Cb -------- *1

Cb = ( Qg + Idma x tonmax ) / ( VD – UVLO) --------- *2

The relationship between tonmax and Cb becomes as follows.

100

10

1

0.1

0.01

0.1

Tonmax-Cb characteristic

1

10

100

tonmax [ms]

Fig.16

1000

Recommended Cb is approximately 3 times of above calculated value.

Please make the decision by the evaluation with the set.

No.A2240-15/16

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