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DI-80

B

9/04

Power Integrations

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Figure 3. Real Input Power (left Y-axis) and Apparent Input

Power (right Y-axis) AC Input Voltage at 50 mA

Load Current (0.6 W Load).

Figure 2. Output Regulation (left Y-axis) and Efficiency

(right Y-axis) Over Load Current at 85 VAC and

265 VAC Input.

Key Design Points

• The output is not safety isolated from the input.

• The circuit shown in Figure 1 has a total output

voltage tolerance of ±10% (-20 °C to +85 °C ambient

temperature).

• To prevent noise coupling and to decrease EMI, place the

input filter components physically away from the source

node of the LinkSwitch-TN and L1 inductor.

• The DC input filter capacitors C1 and C2 can be placed as

a barrier between the AC input and LNK302 and L1. Their

size depends on the minimum operating input voltage and

required holdup time.

• Select ESR of output filter capacitor C5 based on the output

voltage noise requirement.

• Diode D3 should be an ultra-fast type. A reverse recovery

time t

of +70 °C or below. If the ambient temperature is higher,

then a diode with t

• Feedback diode D4 can be a low-cost slow diode such as

1N400X series, however it should be specified as a glass

passivated type to guarantee a specified reverse recovery

time.

• Pre-load R5 is only required for output regulation down

to zero load.

• Use LNK304 for up to 110 mA output current (<2 W

true input power and <6 VA apparent input power at

265 VAC). Select output inductor L1 value and current

rating accordingly.

• See LinkSwitch-TN Design Guide for in-depth

information.

12.5

13.0

Output Current (mA)

PI-3916-081004

11.0

11.5

12.0

60

50

80

70

0

20

10

40

30

30

20

10

0

50

40

85 VAC Load Regulation

265 VAC Load Regulation

85 VAC Efficiency

265 VAC Efficiency

2.5

2.0

3.0

Input Voltage (VAC)

PI-3917-081204

0.0

0.5

1.5

1.0

2.0

3.0

2.5

0.0

0.5

1.5

1.0

175

205

145

115

85

265

235

True Input Power (W)

Apparent Input Power (VA)