米6体育平台手机版

ZHCSQ75C June 2022 – March 2023 UCC28C50-Q1 , UCC28C51-Q1 , UCC28C52-Q1 , UCC28C53-Q1 , UCC28C54-Q1 , UCC28C55-Q1 , UCC28C56H-Q1 , UCC28C56L-Q1 , UCC28C57H-Q1 , UCC28C57L-Q1 , UCC28C58-Q1 , UCC28C59-Q1

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机械数据 (封装 | 引脚)

D|8
- MSOI002K

散热焊盘机械数据 (封装 | 引脚)

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9.2.2.6 Primary-Side Current Stress and Input Capacitor Selection

The input capacitors must be rated for the maximum input voltage, limit the input voltage ripple, and support the required RMS current. The primary peak current (I_{M_VIN}) and duty cycle (D_VIN) at any input voltage (V_IN) can be derived with the following equations

Equation 18.

I_{M_V I N} = \sqrt{\frac{2 \times P_{O}}{L_{M} \times f_{S W} \times η}}

Equation 19.

D_{V I N} = \frac{I_{M} \times L_{M}}{V_{I N}} f_{S W}

The minimum input capacitance (C_{IN_MIN}) and RMS current (I_{CIN_RMS}) they must support can be estimated with the following

Equation 31.

C_{I N_M I N} = \frac{I_{M} \times D_{V I N}}{2 \times f_{S W} \times V_{I N_R I P P L E}}

Equation 21.

I_{C I N_R M S} = \sqrt{\frac{{I_{M}}^{2} \times D_{V I N}}{3} - {(\frac{P_{O}}{V_{I N} \times η})}^{2}}

Assuming 30% input voltage ripple for both 20 W at 40-V and 40 W at 125-V, the required minimum input capacitance is calculated for each case based on the above equations. C_{IN_MIN} at 40-V input is 1.15 µF, while C_{IN_MIN} at 125-V input is only 0.24 µF.

Low voltage operation requires almost 5x more input capacitance to produce the same percentage of input voltage ripple. If the input of auxiliary power supply is tapped to the input of the system power converters, such as the back-up power supply of traction inverters, the input capacitance of the power converters may be sufficient to meet the C_{IN_MIN} requirement at 40-V input. Therefore, the design example only parallels 2-3 high-voltage film capacitors near the regulator for high frequency decoupling.