YZ2354/YZ2358 [ETC]

12V 1A适配器应用; 12V 1A适配器应用


型号：	YZ2354/YZ2358
厂家：	ETC
描述：	12V 1A适配器应用 12V 1A适配器应用
文件：	总9页 (文件大小：6091K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

深圳由甲科技有限公司

YZ235X

PWM Controller of High-performance Current Mode

Product Specification

FEATURES

GENERAL DESCRIPTION

■ Power on Soft Start Reducing MOSFET Vds Stress

combines

a dedicated current mode PWM

YZ235X

■ Frequency shuffling for EMI

controller with a high voltage power MOSFET. It is

GWtimized for high performance, low standby power, and

cost effective off-line flyback converter applications in sub

20W range.

■ Extended Burst Mode Control For Improved Efficiency

and Minimum Standby Power Design

■ Audio Noise Free Operation

■ Fixed 50KHZ Switching Frequency

YZ235X complete protection coverage with

automatic self-recovery feature including Cycle-by-Cycle

current limiting (OCP), over load protection (OLP), VDD

over voltage clamp and under voltage lockout (UVLO).

Excellent EMI performance is achieved with Power-Source

proprietary frequency shuffling technique together with soft

switching control at the totem poGW gate drive output.

The tone energy at below 20KHZ is minimized in the

design and audio noise is eliminated during operation.

■ Internal Synchronized Slope Compensation

■ Low VDD Startup Current and Low Operating Current

■ Leading Edge Blanking on Current Sense Input

■ Good Protection Coverage With Auto Self-Recovery

¾ VDD Over Voltage Clamp and Under Voltage

Lockout with Hysteresis (UVLO)

¾ Y.SUN Proprietary Line Input Compensated

Cycle-by-Cycle Over-current Threshold Setting

For Constant Output Power Limiting Over

Universal Input Voltage Range.

YZ235X

is offered in SOP-8 & DIP8 package.

¾ Overload ProtectiGW (OLP).

¾ Over voltage Protection (OVP)

■ Compatible with OB2353/OB2354/CR6224

■ Pb-Free SOP-8L & DIP-8L

APPLICATIONS

Offline AC/DC flyback converter for

■ Battery Charger

■ PDA power supplies

■ Digital Cameras and Camcorder Adaptor

■ VCR, SVR, STB, DVD&DVCD Player SMPS

■ Set-Top Box Power

■ Auxiliary Power Supply for PC and Server

■ Open-frame SMPS

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YZ235X

TYPICAL APPLICATION

YZ235X

GENERAL INFORMATION

Pin Configuration

Absolute Maximum Ratings

The YZ235X is offered in SOP8 & DIP8 package as

shown below.

SOP8

DIP8

TERMINAL ASSIGNMENTS

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YZ235X

OUTPUT POWER TABLE

Product

230VAC±15%

Open Frame

85-264VAC

Open Frame

Package

YZ2353

YZ2354

YZ2358

DIP8

16W

27W

12W

Notes:

1. Maximum practical continuous power in an open frame design with sufficient drain pattern as a heat sink, at 50℃

ambient.

BLOCK DIAGRAM

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YZ235X

ELECTRICAL CHARACTERISTICS

(TA = 25C, VDD=VDDG=16V, if not otherwise noted)

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YZ235X

CHARACTERIZATION PLOTS

(The characteristic graphs are normalized at Ta=25℃)

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YZ235X

OPERATION DESCRIPTION

The switch frequency reduces at light/no load condition

to improve the conversion efficiency. At light load or no

load condition, the FB input drops below burst mode

threshold level and device enters Burst Mode control.

The Gate drive output switches only when VDD voltage

drops below a preset level and FB input is active to

output an on state. Otherwise the gate drive remains at

off state to minimize the switching loss and reduces the

standby power consumption to the greatest extend.

The switching frequency control also eliminates the

audio noise at any loading conditions.

The YZ235X is a low power off-line SMPS Switcher

optimized for off-line flyback converter applications in sub

20W power range. The ‘Extended burst mode’ control

greatly reduces the standby power consumption and

helps the design easily to meet the international power

conservation requirements.

Startup Current and Start up Control

Startup current of is designed to be very low so

YZ235X

that VDD 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

yet achieve a reliable startup in application. For AC/DC

adaptor with universal input range design, a 2 MΩ, 1/8

W startup resistor could be used together with a VDD

capacitor to provide a fast startup and yet low power

dissipation design solution.

Oscillator Operation

The switching frequency of

is internally fixed at

YZ235X

50KHZ. No external frequency setting components are

required for PCB design simplification.

Current Sensing and Leading Edge Blanking

Operating Current

The Operating current of

is low at 2mA.

YZ235X

Cycle-by-Cycle current limiting is offered in YZ235X

current mode PWM control. The switch current is

detected by a sense resistor into the sense pin. An

internal leading edge blanking circuit chops off the

sensed voltage spike at initial internal power MOSFET

on state due to snubber diode reverse recovery and

surge gate current of internal power MOSFET so that

the external RC filtering on sense input is no longer

needed. The current limiting comparator is disabled and

cannot turn off the internal power MOSFET during the

blanking period. The PWM duty cycle is determined by

the current sense input voltage and the FB input voltage.

Good efficiency is achieved with YZ235X low operating

current together with the ‘Extended burst mode’ control

features.

Soft Start

YZ235X 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. As

soon as VDD reaches UVLO(OFF), the peak current is

gradually increased from nearly zero to the maximum

level of 0.77V. Every restart up is followed by a soft start.

Frequency shuffling for EMI improvement

frequency Shuffling (switching frequency

. The oscillation

The

modulation) is implemented in

YZ235X

Internal Synchronized Slope Compensation

frequency is modulated so that the tone energy is spread

out. The spread spectrum minimizes the conduction

band EMI and therefore eases the system design.

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.

Extended Burst Mode Operation

At light load or zero load condition, most of the power

dissipation in a switching mode power supply is from

switching loss on the mosfet, the core loss of the

ransformer and the loss on the snubber circuit. The

magnitude of power loss is in proportion to the switching

frequency. Lower switching frequency leads to the

reduction on the power loss and thus conserves the

energy. The switching frequency is internally adjusted at

no load or light load condition.

Drive

The internal power MOSFET in

is driven by a

YZ235X

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.

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YZ235X

OPERATION DESCRIPTION

voltage clamp, Under Voltage Lockout on VDD (UVLO).

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.

With Power-Source Proprietary technology, the OCP is

line voltage compensated to achieve constant output

power limit over the universal input 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 drops below UVLO limit.

VDD is supplied by transformer auxiliary winding output.

It is clamped when VDD is higher than 30V. The output of

Protection Controls

is shut down when VDD drops below UVLO_ON

Good power supply system reliability is achieved with its

rich protection features including Cycle-by-Cycle current

limiting (OCP), Over Load Protection (OLP) and over

YZ235X

limit and Switcher enters power on start-up sequence

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YZ235X

PACKAGE MECHANICAL DATA

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YZ235X

8-Pin Plastic DIP

声明：

1.由甲保留说明书的更改权，恕不另行通知！客户在下单前应获取最新版本资料，并验证相关

信息是否完整和最新。

2.任何半导体产品特定条件下都有一定的失效或发生故障的可能，买方有责任在使用由甲产品

进行系统设计和整机制造时遵守安全标准并采取安全措施，以避免潜在失败风险可能造成人身伤害

或财产损失情况的发生！

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YZ2354/YZ2358 [ETC]

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