Daewoo DTH-14Q1FS, Service Manual

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5) Drive circuit
The STR-S5707 applies the proportional drive system in order to minimize turn-on and satruration loss, and
storage time. In the conventional RCC system, turn-on loss and switching noise due to the surge current
appearing when the power transistor turns on are high as because the transistor is driven by the drive current
shown in Fig. 10-1. In addition, since is decreases linearly when the transistor turn off and a peak value of I
B2
is
not large, the storage time is long and the V
CE(sat)
voltage is high, which results in large turn-off loss. The circuit
and the waveforms of the proportional drive system which is applied to the STR-S5707 in order to reduce these
switching loss and shorten the storage time are shown in Fig . 10 and Fig. 10-2 respectively.
OSC
Drive
R810
C805
D806
Fig .10 D806 and C805 function to reverse-blas between the base and the emitter
of the transistor during its off state.
Fig .10-1 Waveforms of Conventional
RCC Power Supply Fig .10-2 Waveforms of power Supply
Using STR-S5707
VCE
IC
0
VCE
IC
0
V
BE
I
B
Reveres
bias
V
BE
I
B
Reveres
bias