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IRF7807VD2PbF 数据表(PDF) 3 Page - International Rectifier |
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IRF7807VD2PbF 数据表(HTML) 3 Page - International Rectifier |
3 / 9 page IRF7807VD2PbF www.irf.com 3 Control FET Special attention has been given to the power losses in the switching elements of the circuit - Q1 and Q2. Power losses in the high side switch Q1, also called the Control FET, are impacted by the R ds(on) of the MOSFET, but these conduction losses are only about one half of the total losses. Power losses in the control switch Q1 are given by; P loss = Pconduction+ Pswitching+ Pdrive+ Poutput This can be expanded and approximated by; P loss = I rms 2 × R ds(on ) () + I × Q gd i g × V in × f ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ + I × Q gs 2 i g × V in × f ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ + Q g × Vg × f () + Q oss 2 ×V in × f ⎛ ⎝ ⎞ ⎠ This simplified loss equation includes the terms Q gs2 and Q oss which are new to Power MOSFET data sheets. Q gs2 is a sub element of traditional gate-source charge that is included in all MOSFET data sheets. The importance of splitting this gate-source charge into two sub elements, Q gs1 and Qgs2, can be seen from Fig 1. Q gs2 indicates the charge that must be supplied by the gate driver between the time that the threshold voltage has been reached (t1) and the time the drain current rises to I dmax (t2) at which time the drain volt- age begins to change. Minimizing Q gs2 is a critical fac- tor in reducing switching losses in Q1. Q oss is the charge that must be supplied to the out- put capacitance of the MOSFET during every switch- ing cycle. Figure 2 shows how Q oss is formed by the parallel combination of the voltage dependant (non- linear) capacitance’s C ds and Cdg when multiplied by the power supply input buss voltage. Figure 1: Typical MOSFET switching waveform Synchronous FET The power loss equation for Q2 is approximated by; P loss = Pconduction + Pdrive + Poutput * P loss = I rms 2 × R ds(on) () + Q g × Vg × f () + Q oss 2 × V in × f ⎛ ⎝ ⎜ ⎞ ⎠ + Q rr × Vin × f ( ) *dissipated primarily in Q1. Power MOSFET Selection for DC/DC Converters 4 1 2 Drain Current Gate Voltage Drain Voltage t3 t2 t1 V GTH t0 |
类似零件编号 - IRF7807VD2PbF |
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类似说明 - IRF7807VD2PbF |
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