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标题: 基于LM5023的AC-DC 准谐振电流模式 PWM 控制器 [打印本页]

作者: iczoom188 时间: 2018-11-27 17:00
标题: 基于LM5023的AC-DC 准谐振电流模式 PWM 控制器

基于LM5023的AC-DC 准谐振电流模式 PWM 控制器

　　1 Features

　　Critical Conduction Mode

　　Peak-Current Mode Control

　　Skip-Cycle Mode for Low-Standby Power

　　Hiccup Mode for Continuous Overload Protection

　　Cycle-by-Cycle Overcurrent Protection Maintains Accuracy Over the Universal AC Line

　　Line-Voltage Feedforward

　　OVP Protection by Sensing the Auxiliary Winding

　　Integrated 0.7-A Peak Gate Driver

　　Direct Opto-Coupler Interface

　　Leading Edge Blanking of Current Sense Signal

　　Maximum Frequency Clamp 130 kHz

　　Programmable Soft-Start

　　Thermal Shutdown

　　8-Pin VSSOP Package

　　Create a Custom Design using the LM5023 with the WEBENCH Power Designer

　　2 Applications

　　Universal Input AC-to-DC Notebook Adapters from 10 W to 65 W

　　High-Efficiency Housekeeping and Auxiliary Power Supplies

　　Battery Chargers

　　Consumer Electronics (DVD Players, Set-Top Boxes, DTV, Gaming, Printers)

　　3 Description

　　The LM5023 is a quasi-resonant pulse width modulated (PWM) controller which contains all of the features needed to implement a highly efficient off-line power supply. The LM5023 uses the transformer auxiliary winding for demagnetization detection to ensure critical conduction mode (CrCM) operation. The LM5023 features a hiccup mode for overcurrent protection with an auto restart to reduce the stress on the power components during an overload. A skip-cycle mode reduces power consumption at light loads for energy conservation applications (ENERGY STAR®, CEPCP, and so forth). The LM5023 also uses the transformer auxiliary winding for output overvoltage protection (OVP); if an OVP fault is detected the LM5023 latches off the controller.

　　The LM5023 is a quasi-resonant PWM controller which contains all of the features needed to implement a highly efficient off-line power supply. The LM5023 uses the transformer auxiliary winding for demagnetization detection to ensure quasi-resonant operation (valley-switching) to minimize switching losses. For applications that need to meet the ENERGY STAR low standby power requirements, the LM5023 features an extremely low lq current (346 µA) and skip-cycle mode which reduces power consumption at light loads. The LM5023 uses a feedback signal from the output to provide a very accurate output-voltage regulation <1%. To reduce overheating and stress during a sustained overload conditions the LM5023 offers a hiccup mode for over-current protection and provides a current-limit restart timer to disable the outputs and forcing a delayed restart (hiccup mode).

For offline start-up, an external depletion mode N-channel MOSFET can be used. This method is recommended for applications where a very low standby power (<50 mW) is required. For application where a low standby power is not as critical, an enhancement mode, N-channel MOSFET can be used. If an OV is detected on the auxiliary winding (QR pin), the device permanently latches off, requiring recycling of power to restart. VCC voltage must be brought lower than VRST to reset the latch. Additional features include line-current feedforward, pulse-by-pulse current limit, and a maximum frequency clamp of 130 kHz.

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