基于UCC28610的25-90W Cascoded Flyback Power Supply Controller

iczoom188

基于UCC28610的25-90W Cascoded Flyback Power Supply Controller

　　1 特性

　　级联配置可实现完全集成式电流控制而无需外部传感电阻器

　　具有由共源共栅配置实现的低待机功耗的快速启动

　　针对整个运行范围内最优效率的频率和峰值电流调制

　　绿色环保模式 (GM) 突发开关数据包提升无负载效率

　　高级过流保护限制均方根 (RMS) 输入和输出电流

　　热关断

　　支持重试或锁存响应的定时过载

　　可编程无光耦输出过压保护

　　快速闭锁故障恢复

　　8 引脚小外形尺寸集成电路 (SOIC) 封装以及 8 引脚塑料双列直插 (PDIP) 无铅封装

　　2 应用

　　通用输入交流和直流适配器，12 至 65W

　　高效内务处理和辅助电源

　　离线电池充电器

消费类电子产品(DVD 播放器、机顶盒、数字电视、游戏机和打印机)

TI产品现货库存在线购买：https://www.iczoom.com/brand/509-c-1-20.html

　　3 说明

　　UCC28610 将交流和直流消费类电源解决方案的性能和可靠性水平提高到全新的水平。

　　一个脉宽调制 (PWM) 调制算法在整个运行范围内保持断续或转换模式运行的同时，变化开关频率和初级电流。与一个共源共栅架构组合在一起，这些技术创新在一个传统反激式架构中改进了效率、可靠性和系统成本。

　　UCC28610 提供一个可预期的最大功率阈值，以及一个针对过载的定时响应，从而实现对浪涌功率要求的安全处理。对于重试或锁存模式，过载故障响应是可由用户设定的。额外保护 功能 包括输出过压检测、可编程最大导通时间和热关断。

　　The flyback converter is attractive for low power AC/DC applications because it provides output isolation and wide input operating abilities using a minimum number of components. Operation of the flyback converter in Discontinuous Conduction Mode (DCM) is especially attractive because it eliminates reverse recovery losses in the output rectifier and it simplifies control.

　　The UCC28610 is a flyback controller for 12-W to 65-W, peak AC/DC power supply applications that require both low AC line power during no-load operation and high average efficiency. This controller limits the converter to DCM operation. It does not allow Continuous Conduction Mode (CCM) operation. Forced DCM operation results in a uniquely safe current limit characteristic that is insensitive to AC line variations. The peak current mode modulator does not need slope compensation because the converter operates in DCM.

　　The operation of the UCC28610 is facilitated by driving the external high voltage MOSFET through the source. This configuration is called a cascode driver. It features fast start-up and low input power under no-load conditions without having high voltage connections to the control device. The cascode driver has no effect on the general operation of the flyback converter.

　　The feedback pin uses current rather than voltage. This unique feature minimizes primary side power consumption during no-load operation by avoiding external resistive conversion from opto-coupler current to voltage.

　　Average efficiency is optimized by the UCC28610 between peak power and 22% peak power with constant peak current, variable off-time modulation. This modulation tends to make the efficiency constant between 22% and 100% peak load, eliminating the need to over-design to meet average efficiency levels that are required by EnergyStar™.

　　The forced DCM feature provides protection against excessive primary currents in the event that the input voltage becomes very low. The highest possible secondary currents can be described by Equation 1. The UCC28610 adds further protection by allowing the user to program the maximum on-time.

　　The Maximum On-Time (MOT) function causes the converter to react as if there is an overload condition if the load is sufficiently large during a line sag condition. During low line conditions the MOT function limits the on-time of the primary switch which limits the peak current in the primary power stage. Figure 19 shows how the MOT period, tMOT, is programmed over the range of 1.5 μs to 5 μs for either range of programming resistors. The resistor range determines the controller’s response to a sustained overload fault – to either Latch-off or to Shutdown/Retry, which is the same response for a line-sag, or brown out, condition.

　　The UCC28610 controller monitors the output voltage by sampling the voltage at the auxiliary winding. The sampling time has a fixed delay of 1 μs, tBLANK,OVP, after the internal driver turns off. This allows the auxiliary winding to be sampled after the bias winding voltage settles from the transient. This same delay is used to blank the ZCD input to avoid unintended zero crossing detection should the ringing be large enough to cross the ZCD zero crossing threshold.

　　The output over-voltage (OV) threshold is set using the turn ratio of the auxiliary winding to the output secondary and a resistive divider into the ZCD input pin. The UCC28610 will always enter a latched-off state if it detects an OV condition. The VDD supply must cycle below the fault reset threshold to re-start in order to recover. The functionality of the over-voltage detection function is shown in Figure 20.