Brother LX-200 Service Manual page 127

+5V Power Supply
Fig. 5.6-2 shows the timing chart of the power IC (IC#6) for the +5V DC power
supply during idling.
In this circuit, the transistor Q11 switches at approximately 100 kHz to convert the
unstabilized input voltage to a stabilized +5V supply.
When transistor Q11 is ON, energy accumulates in the coil L3 and electrolytic
capacitor C27 until they are able to supply a +5V voltage. Transistor Q11 turns OFF
and the energy is supplied by diode D4. The transistor Q11 switching ratio is
changed by the load current to create a stable supply. This control is conducted in
the power IC.
Fig. 5.6-2 +5 V Timing Chart
+24V Power Supply
Fig. 5.6-3 shows the timing chart for the +24V DC power supply during idling.
In this circuit, the transistor Q5 switches at approximately 100 kHz to convert the
unstabilized input voltage to a stabilized +24V supply.
When transistor Q5 is ON, energy accumulates in the coil L1. When transistor Q5
turns OFF, this energy is supplied through diode D3 to the electrolytic capacitor C17,
where it accumulates and is output as +24V DC.
The transistor Q5 switching ratio is changed by the load current to create a stable
supply. This control is conducted in the power IC.
Fig. 5.6-3 +24V Timing Chart
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