CRE6559 datasheet(8/9 Pages) CRE

8 / 9 page

Built-in slope compensation circuit adds voltage

ramp onto the current sense input voltage for PWM

generation. This greatly improves the close loop

stability at CCM and prevents the sub-harmonic

oscillation and thus reduces the output ripple

voltage.

The internal power MOSFET in CRE6559 is driven

by a dedicated gate driver for power switch control.

Too weak the gate drive strength results in higher

conduction and switch loss of MOSFET while too

strong gate drive results the compromise of EMI. A

good tradeoff is achieved through the built-in totem

pole gate design with right output strength and dead

time control. The low idle loss and good EMI system

design is easier to achieve with this dedicated

control scheme. In addition to the gate drive control

scheme mentioned, the gate drive strength can also

be adjusted externally by a resistor connected

between VDD and VDDG, the falling edge of the

Drain output can be well controlled. It provides

great flexibility for system EMI design.

Good power supply system reliability is achieved

with its rich protection features including Cycle-

by-Cycle c urrent limiting(OCP),Over Load

Protection(OLP)and over voltage clamp,

UnderVoltage Lockout onVDD(UVLO). With

Proprietary technology, the OCP is line voltage

range. At overload condition when FB input

voltage exceeds power limit threshold value for

more than TD_PL, control circuit reacts to shut

down the switcher. Switcher restarts when VDD

voltage drop below UVLO limit. VDD is supplied

by transformer auxiliary winding output. It is

clamped when VDD is higher than 30V .The output

of CRE6559 is shut down when VDD drop below

UVLO_ON limit and Switcher enters power on

start-up sequence.

CRE6559 FREQ SHUFFLING

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CRE6559 датащи(PDF) 8 Page - CRE Semiconductor Inc.