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Given: A MOSFET is used in a switching power-pole found in Fig. 2-4 a of the text. The operating conditions are as follows: Vin = 35 V, Io = 6 A, the switching frequency fs = 300 kHz, and the duty ratio d = 0.4. a) Consider the diode in the power pole. Assuming an offset voltage forward bias model of the free-wheeling diode in which VFM = 1.2 V, calculate the average forward power loss in the diode. HINT: Consider Eq. 2 A-1. b) In the diode reverse recovery characteristic shown in Fig. 2A−1, ta = 10 ns, trf = 25 ns, and IRRM = 2 A, calculate the average switching power loss in the diode. HINT: Consider Eq. 2 A-2. c) How much in overall average switching loss in MOSFET will be if the impact of diode reverse recovery is included during MOSFET switching? Assume tri = tfi = 20 ns and tfv = trv = 25 ns. d) If the maximum junction temperature of the diode is Tj(max) = 110∘C, what is the maximum acceptable thermal resistance from junction to ambient if the maximum ambient temperature is Ta(max) = 40∘C? Pdiode,F = (1−d)⋅VFMIo Pdiode,sw = (12 IRRMtb)⋅Vd,neg⋅fs

Given: A MOSFET is used in a switching power-pole found in Fig. 2-4 a of the text. The operating conditions are as follows: Vin = 35 V, Io = 6 A, the switching frequency fs = 300 kHz, and the duty ratio d = 0.4. a) Consider the diode in the power pole. Assuming an offset voltage forward bias model of the free-wheeling diode in which VFM = 1.2 V, calculate the average forward power loss in the diode. HINT: Consider Eq. 2 A-1. b) In the diode reverse recovery characteristic shown in Fig. 2A−1, ta = 10 ns, trf = 25 ns, and IRRM = 2 A, calculate the average switching power loss in the diode. HINT: Consider Eq. 2 A-2. c) How much in overall average switching loss in MOSFET will be if the impact of diode reverse recovery is included during MOSFET switching? Assume tri = tfi = 20 ns and tfv = trv = 25 ns. d) If the maximum junction temperature of the diode is Tj(max) = 110∘C, what is the maximum acceptable thermal resistance from junction to ambient if the maximum ambient temperature is Ta(max) = 40∘C? Pdiode,F = (1−d)⋅VFMIo Pdiode,sw = (12 IRRMtb)⋅Vd,neg⋅fs

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Given: A MOSFET is used in a switching power-pole found in Fig. 2-4a of the text. The operating conditions are as follows: V in = 35 V , I 0 = 6 A , the switching frequency f s = 300 k H z , and the duty ratio d = 0.4 . a) Consider the diode in the power pole. Assuming an offset voltage forward bias model of the free-wheeling diode in which V F M = 1.2 V , calculate the average forward power loss in the diode. HINT: Consider Eq. 2A-1. b) In the diode reverse recovery characteristic shown in Fig. 2 A − 1 , t a = 10 n s , t r f = 25 n s , and I R R M = 2 A, calculate the average switching power loss in the diode. HINT: Consider Eq. 2A-2. c) How much in overall average switching loss in MOSFET will be if the impact of diode reverse recovery is included during MOSFET switching? Assume t r i = t f i = 20 n s and t f v = t r v = 25 n s . d) If the maximum junction temperature of the diode is T j ( max ) = 110 ∘ C , what is the maximum acceptable thermal resistance from junction to ambient if the maximum ambient temperature is T a ( max ) = 40 ∘ C ?
P diode , F = ( 1 − d ) ⋅ V F M I o P diode , s w = ( 1 2 I R R M t b ) ⋅ V d , n e g ⋅ f s

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