Panasonic KX-FT937LA-B Service Manual page 46

KX-FT937LA-B
The following is an overview of how the power supply unit is controlled.
The control method of this power supply unit is pulse width modulation.
When Q is ON, the energy is charged in the transfer primary coil according to E . When Q is OFF, the energy is output from the
1 1 1
secondary transfer as follows.
L → D → Load → L
1
Then the power is supplied to the Load. When Q is ON, power is not output from the secondary side. The output voltage is fed
1
back in the control circuit according to the error amp rectifier. Then depending on how f is controlled, stabilization occurs. Also,
when the current load becomes too large, in order to decrease the voltage output, the increase in f is controlled and the output volt-
age is stabilized.
Therefore, basically the timing: f of Q1 controls the output voltage.
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