HT2273 datasheet(7/10 Pages) HOTCHIP

7 / 10 page

HT2273

7/10

Current Mode PWM Controller

www.hotchip.com.cn

Ver1.0

Function Description

HT2273 is a high performance current mode PWM

controller,

optimized

for

low

power

AC/DC

application. Ultra low startup current and operating

current together with burst mode feature minimize

the standby power consumption and improve the

switching efficiency. In addition to reduce the

external

component

count,

the

internal

synchronous

slope

compensation

combines

compensation combines with

the leading-edge

blanking

improves system large stability and

reduces

the

possible

subharmonic

oscillation.

HT2273 also have multiform general recovery

protection mode. The main function is described as

below

Startup Current and Startup Control

Startup current of HT2273 is designed to be

extremely low at 5uA, so that VCC could be

charged up above UVLO threshold level and device

starts up quickly. A large value startup resistor can

therefore be used to minimize the power loss,

predigest the design of startup circuit and provides

reliable startup in application. For the design of

AC/DC adaptor with universal input range, a startup

resistor of 2 MΩ, 1/8 W could be used together with

a VCC capacitor to provide a fast startup and low

power dissipation solution.

Operating Current

The operating current of HT2273 is low at 1.8mA.

Excellent efficiency is achieved with low

operating current together and extended burst

mode control circuit.

Soft Start

HT2273 features an internal 4ms soft start to soften

the electrical stress occurring in the power supply

during startup. It is activated during the power on

sequence.

soon as

VCC reaches

UVLO

（ OFF ）， the CS peak voltage is gradually

increaced from 0.15V to the maximum level. Every

restart up is followed by a soft start.

Extended Burst Mode Operation

At zero load or light load, most of the power

dissipation of the switching power supply comes

from the MOSFET switching loss, the core loss of

the transformer and the loss on the snubber circuit.

The magnitude of power loss is in proportion to the

number of switching events within a period of time.

Therefore reducing the switch event leads to

reduction on the power loss and thus saving the

energy.

For the burst mode control circuit, HT2273 self

adjusts the switching mode according to the loading

condition. At the condition of no load or

light/medium load, the FB input voltage drops below

burst mode threshold level. Device enters Burst

Mode control on the basis of the judgment. The

gate drive output switches only when VCC voltage

drops below a preset level and FB input is active.

Otherwise the gate drive remains at off to

minimize the switching loss and power consumption

to the greatest extend. The frequency control also

eliminates the audio noise at any loading

conditions.

HT2273 数据表(PDF) 7 Page - Hotchip Technology Co.,Ltd

HT2273 数据表(HTML) 7 Page - Hotchip Technology Co.,Ltd

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