Page 177 - Rashid, Power Electronics Handbook

166 Y.-S. Lee and M. Chow

FIGURE 10.40 Practical ¯yback converter circuit: V IN ¼ 60 V;
FIGURE 10.38 Basic circuit of ¯yback converter. D S ¼ MUR460; D R ¼ MUR460; M 1 ¼ IRF640; R 1 ¼ 4:7 KO;
R 2 ¼ 100 O; C 1 ¼ 0:1 mF; C 2 ¼ 680 pF; C L ¼ 100 mF; ESR of
C L ¼ 0:05 O; L p ¼ 100 mH; L S ¼ 400 mH; R L ¼ 400 O; N P : N S ¼ 1 : 2;
effective winding resistance of L P ¼ 0:025 O; effective winding resistance
snubber (R C ) is used to damp the ringing voltage across the of L S ¼ 0:1 O; and coupling coef®cient K ¼ 0:992.
2 2
output recti®er D and a resistor-capacitor-diode clamping
R
(R C D ) is used to clamp the ringing voltage across the energy transferred to C is then dissipated slowly in the
1 1 S 1
switch M . The diode D here allows the energy stored by parallel resistor R without ringing problems.
1 S 1
the current in the leakage inductance to be converted to the The simulated waveforms of the ¯yback converter (circuit
form of a dc voltage across the clamping capacitor C . The given in Fig. 10.40) for discontinuous-mode operation are
1

FIGURE 10.39 Idealized steady-state waveforms of ¯yback converter for discontinuous-mode operation.