ICE2QR2280G-1(2015) 데이터 시트보기 (PDF) - Infineon Technologies

부품명

상세내역

제조사

ICE2QR2280G-1
(Rev.:2015)

20 W 5 V SMPS Evaluation Board with Quasi - Resonant CoolSET™ ICE2QR2280G-1

Infineon Technologies 

20 W 5 V SMPS Evaluation Board with

Quasi-Resonant CoolSET™ ICE2QR2280G-1

Circuit operation

5.3

Output stage

On the secondary side, 5 V output, the power is coupled out via a schottky diode D21. The capacitors C21

and C22 provide energy buffering followed by the L-C filters L21 and C23 to reduce the output ripple and

prevent interference between SMPS switching frequency and line frequency considerably. Storage

capacitors C21 and C22 are designed to have an internal resistance (ESR) as small as possible. This is to

minimize the output voltage ripple caused by the triangular current.

5.4

Feedback loop

For feedback, the output is sensed by the voltage divider of Rc1 and Rc3 and compared to TL431 internal

reference voltage. Cc1, Cc2 and Rc4 comprise the compensation network. The output voltage of TL431 is

converted to the current signal via optocoupler IC2 and two resistors Rc5 and Rc6 for regulation control.

6

Circuit operation

6.1

Startup operation

Since there is a built-in startup cell in the ICE2QR2280G-1, there is no need for external start up resistor,

which can improve standby performance significantly.

When VCC reaches the turn on voltage threshold 18V, the IC begins with a soft start. The soft-start

implemented in ICE2QR2280G-1 is a digital time-based function. The preset soft-start time is 12ms with 4

steps. If not limited by other functions, the peak voltageon CS pin will increase step by step from 0.32V to 1V

finally. After IC turns on, the VCC voltage is supplied by auxiliary windings of the transformer.

6.2

Normal mode operation

The secondary output voltage is built up after startup. The secondary regulation control is adopted with

TL431 and optocoupler. The compensation network Cc1, Cc2 and Rc4 constitute the external circuitry of the

error amplifier of TL431. This circuitry allows the feedback to be precisely controlled with respect to

dynamically varying load conditions, therefore providing stable control.

6.3

Primary side peak current control

The MOSFET drain source current is sensed via external resistor R4 and R4A. Since ICE2QR2280G-1 is a

current mode controller, it would have a cycle-by-cycle primary current and feedback voltage control which

can make sure the maximum power of the converter is controlled in every switching cycle.

6.4

Digital frequency reduction

During normal operation, the switching frequency for ICE2QR2280G-1 is digitally reduced with decreasing

load. At light load, the MOSFET will be turned on not at the first minimum drain-source voltage time, but on

the nth. The counter is in range of 1 to 7, which depends on feedback voltage in a time-base. The feedback

voltage decreases when the output power requirement decreases, and vice versa. Therefore, the counter is

set by monitoring voltage VFB. The counter will be increased with low VFB and decreased with high VFB. The

thresholds are preset inside the IC.

Application Note

5

Revision 1.1, 2015-04-02

Share Link: