TEA1733T_TEA1733LT_2

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Product data sheet

Rev. 02 — 26 March 2010

9 of 20

NXP Semiconductors

TEA1733T; TEA1733LT

GreenChip III SMPS control IC

7.10 Overpower or high/low line compensation (VINSENSE and

ISENSE pins)

The overpower compensation function can be used to realize a maximum output power

which is nearly constant over the full input mains.

The overpower compensation circuit measures the input voltage on the VINSENSE pin

and outputs a proportionally dependent current on the ISENSE pin. The DC voltage

across the soft start resistor limits the maximum peak current on the current sense

resistor.

At low output power levels, the overpower compensation circuit is switched off

(See Figure 9).

7.11 Soft start-up (ISENSE pin)

A soft start is made to prevent audible noise during start-up or a restart condition. Before

the converter starts, the soft start capacitor C6 (see Figure 3) on the ISENSE pin is

charged. When the converter starts switching, the primary peak current slowly increases

as the soft start capacitor discharges through the soft start resistor (R6, see Figure 3).

The soft start time constant is set by the soft start capacitor value chosen. The soft start

resistor value must also be taken into account, but this value is typically defined by the

overpower compensation (see Section 7.10).

Fig 8.

Leading edge blanking

VISENSE

t

014aaa932

Fig 9.

Overpower compensation using pins VINSENSE and ISENSE

2

1.7

0.68

1234

014aaa933

(

μA)