TNY264_1 POWERINT [Power Integrations, Inc.], TNY264_1 Datasheet - Page 7

• Manufacturer Part Number: TNY264_1
• Description: Generic PCB for DVD Player using TinySwitch-II
• Manufacturer: POWERINT [Power Integrations, Inc.]

DER-9
Generic PCB for DVD Player using TinySwitch-II
February 4, 2004
4 Circuit Description
4.1 Input EMI Filtering
C1 and C2 are the bulk capacitors. Together with L1 and L2, they form the EMI filter.
TinySwitch-II’s built-in frequency jitter helps achieve low EMI in spite of this very simple
EMI filter.
C18 is an option for a high voltage ceramic capacitor in case a single electrolytic
capacitor is required for the bulk capacitor.
4.2 Primary Clamp Snubber
D5, R1, R2, and C3 form the primary clamp snubber to clamp the voltage spike at the
Drain pin after TinySwitch-II turn-off. D5 is a 1N4007G, a glass-passivated version of the
standard 1N4007, with controlled reverse recovery. Its use, along with R2, improves EMI
and efficiency.
4.3 Output filtering
C6, C8, C10, C12 and C14 are the main output capacitors. C7, C9, C11 and C13, along
with L3, L4, L5 and R8, form second-stage output filters.
4.4 Output Feedback
U2, VR1, and R15 form the voltage feedback network. The 5V output voltage setpoint is
set by the voltage drops of U2, VR1, and R15. The TinySwitch-II unique feedback
scheme, with constant feedback current over line and load changes, means that the
current in the zener does not change, thus the voltage drops in U2, VR1, and R15 do not
change. This yields tight regulation in spite of the circuit’s simplicity and low cost.
4.5 “DC Switch”
J4 is connected to a switch, wherein if it is closed, the 5V output drops to about 1.2V,
th
because the zener ZR1 is essentially shorted out. All the outputs drop to about 1/5
of
their normal voltages. During this condition, the load draws very little current. Because
of TinySwitch-II’s EcoSmart operation, it draws very little input power - <200 mW. This
“DC Swtich” can be used in place of a normal “AC Switch” that’s used to disconnect the
AC power. The DC Switch is lower cost because it does not have to be Safety–rated,
and is lower voltage.
4.6 +8V Option
Q1, R4, R5 and R6 form a linear regulator to generate +8V in case of +8V is required.
VR3 is another solution of generating +8V. Yet another option is to use a zener as a
series pass element.
4.7 –22V option
R8 and C13 form a post-stage filter for –22V.
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