PI超薄筆記本電腦設計:The notebook adapter power supply shown in Figure 1 features the
Power Integrations? TOPSwitch?-HX TOP261LN in a fl yback
confi guration, using a universal input to deliver a 65 W, 19.7 V
Figure 1. 65 W Notebook Adapter Schematic.
output. The features designed into the TOP261LN (U11) provide the
type of protection important to a notebook adapter such as OVP,
latching shutdown, and hysteretic thermal-overload protection.
All TOPSwitch-HX devices feature EcoSmart? to provide constant
effi ciency over full specifi ed load range. EcoSmart utilizes multicycle
modulation (MCM), a proprietary, automatic function that
eliminates special operating modes usually necessary at specifi c
load thresholds. This simplifi es and optimizes circuit design for
meeting future energy effi ciency regulation changes without
redesign.
Capacitor C66 at the input reduces differential mode EMI, while
Resistors R63 and R64 provide a discharge path upon AC removal
to prevent shock. Bridge rectifi er D25 rectifi es the AC. Bulk
capacitors C63 and C64 fi lter the resulting DC. A line-sensing
network (D26 and C70) enables implementation of a fast AC reset
function. A clamp network (C43, R93, R62, D18, VR2, and R72)
prevents voltage spikes at the Drain (D) pin upon MOSFET switch
turn-off. Y-capacitor C41 reduces common-mode EMI, as does common-mode inductor L1.