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ICE5QSAG

Quasi-Resonant Controller

Infineon Technologies 

Quasi-Resonant Controller

Functional Description

VCS (V)

VCS_N, 1

0.9

Starting ZC = 1

Starting ZC = 3

Figure 8

0.83 1.29 VVIN_REF

VVIN (V)

Variation of the VCS limit voltage according to the VIN voltage

3.5

Active Burst Mode with selectable power level

At light load condition, the IC enters Active Burst Mode operation to minimize the power consumption. Details

about Active Burst Mode operation are explained in the following paragraphs.

The burst mode entry level can be selected by changing the different resistor RSel at FB pin. There are 2 levels to

be selected with different resistor which are targeted for low range of active burst mode power (Level 1) and

high range of active burst mode power (Level 2). The following table shows the control logic for the entry and

exit level with the FB voltage.

Table 4

Two levels entry and exit active burst mode power

Level VFB

1

VFB > VREF_B

2

VFB < VREF_B

VCS

VCS_BL1 = 0.31 V

VCS_BL2 = 0.35 V

Entry level

VFB_EBLX

0.90 V

1.05 V

Exit level

VFB_LB

2.75 V

2.75 V

During IC first startup, the internal RefGOOD signal is logic low when VCC < 4 V. It will reset the Burst Mode level

Detection latch. When the Burst Mode Level Detection latch is low and IC is in OFF state, the IC internal RFB

resistor is disconnected from the FB pin and a current source Isel is turned on instead.

From Vcc=4 V to Vcc on threshold, the FB pin will start to charge to a voltage level associated with RSel resistor.

When Vcc reaches Vcc on threshold, the FB voltage is sensed. The burst mode thresholds are then chosen

according to the FB voltage level. The Burst Mode Level Detection latch is then set to high. Once the detection

latch is set high, any change of the FB level will not change the threshold selection. The current source Isel is

turned off in 2 μs after VCC reaches VCC on threshold and the RFB resistor is re-connected to FB pin (see Figure 9).

Vdd

Ise l

UVLO

Refgood

S

2μs

R

delay

Burst mode

detection latch

VCS_BLx

VFB_E BL x

Selec tio n

Lo gic

Com pare

logic

S2

RFB

S1

FB

VR EF _B

Control unit

Figure 9 Burst mode detect and adjust

Datasheet

11 of 27

V 2.1

2020-02-03

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