TNY266P_1 POWERINT [Power Integrations, Inc.], TNY266P_1 Datasheet - Page 7

• Manufacturer Part Number: TNY266P_1
• Description: 4.9W DVD power supply
• Manufacturer: POWERINT [Power Integrations, Inc.]

DER-10
4.9W DVD power supply using TNY266P
February 4, 2004
5 Circuit Description
5.1 Input EMI Filtering
C1, and C2 are the bulk capacitors. Together with L1, they form the EMI filter.
TinySwitch-II’s built-in frequency jitter helps achieve low EMI in spite of this very simple
EMI filter.
5.2 Primary Clamp Snubber
D5, R1, R2, and C3 form the primary clamp snubber to clamp the voltage spike at the
Drain pin after 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.
5.3 Output filtering
C6, C8, and C12 are the main output capacitors. C7, C9, and C11, along with L3, L4,
and L5, form second-stage output filters.
5.4 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.
5.5 “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 output drop to about 1/5
of
their normal voltages. During this condition, the load draws very little current. Because
of the TinySwitch’s EcoSmart operation, it draws very little input power - <200 mW. This
“DC Switch”, 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.
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