SSL2102 datasheet(9/21 Pages) NXP

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SSL2102_1

Product data sheet

Rev. 01 — 29 June 2009

9 of 21

NXP Semiconductors

SSL2102

SMPS IC for dimmable LED lighting

8.6 Demagnetization

The system operates in discontinuous conduction mode if the AUX pin is connected. As

long as the secondary stroke has not ended, the oscillator will not start a new primary

stroke. During the ﬁrst tsup(xfmr_ring) seconds, demagnetization recognition is suppressed.

This suppression may be necessary in applications where the transformer has a large

leakage inductance and at low output voltages.

8.7 Overcurrent protection

The cycle-by-cycle peak drain current limit circuit uses the external source resistor

RSENSE1 to measure the current. The circuit is activated after the leading edge blanking

time tleb. The protection circuit limits the source voltage over the RSENSE resistor to

Vth(ocp)SOURCE and thus limits the primary peak current.

8.8 Short-winding protection

The short-winding protection circuit is also activated after the leading edge blanking time.

If the source voltage exceeds the short-winding protection threshold voltage

Vth(swp)SOURCE, the IC stops switching. Only a power-on reset will restart normal operation.

The short-winding protection also protects in case of a secondary diode short circuit.

8.9 Overtemperature protection

Accurate temperature protection is provided in the device. When the junction temperature

exceeds the thermal shut-down temperature, the IC stops switching. During thermal

protection, the IC current is lowered to the start-up current. The IC continues normal

operation as soon as the overtemperature situation has disappeared.

(1)

At N

× V

o =80V)

Fig 7.

Typical phase of drain ringing at switch-on (at

200

400

800

f (kHz)

phase

(

°)

−20

−40

014aaa573

600

RSENSE is the resistor between the SOURCE pin and GND

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