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DER-37 参数 Datasheet PDF下载

DER-37图片预览
型号: DER-37
PDF下载: 下载PDF文件 查看货源
内容描述: 16W超薄适配器电源采用TOP245P [16W Low Profile Adapter Supply using TOP245P]
分类和应用:
文件页数/大小: 32 页 / 1258 K
品牌: POWERINT [ Power Integrations ]
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DER-37  
16W Adapter using TOP245P  
April 27, 2004  
The CONTROL pin requires 2 mA to power the internal circuitry of the chip. Any current  
beyond that normally would be shunted, and commands the duty cycle to reduce. With  
2 mA of current the duty cycle is set to maximum.  
Feedback current above ~2mA forward biases Q1 through R10 and pulls up R13 via  
R14. The X pin looks like a 1.2V voltage source. The current it is sourcing determines  
the output MOSFET peak current limit. As current decreases, the peak current limit is  
reduced from maximum (when X-pin current is 170 uA), down to a minimum of 40% of  
nominal peak current limit (when X-pin is at 30 uA). Therefore, as the feedback current  
increases, the sink current decreases and the primary current limit reduces, thereby  
allowing the output voltage feedback loop to control the primary peak current. Resistor  
R14 sets the peak current limit (startup and overload). Any feedback current above 2 mA  
engages the X pin control, the current into the CONTROL pin is limited to this level and  
therefore, the PWM function of the CONTROL pin does not determine the duty cycle.  
As the load is reduced, the primary current limit reduces until it reaches 40% of peak  
current limit. At this point, another X-pin function is activated. The remote ON/OFF  
(inhibit) threshold is reached at an X pin sink current of approximately 27 µA. The supply  
then operates with fixed 25% current limit, but with a variable off-time, resulting in a  
variable switching frequency. To maintain regulation, as the load is further reduced, the  
frequency reduces. This greatly reduces switching losses, maintaining high standby  
efficiency and low no-load power consumption.  
Slope compensation is provided by a ramp signal generated from the bias winding via  
D4, R7 and C9. C9 also serves as a high frequency roll off filter.  
Power Integrations  
Tel: +1 408 414 9200 Fax: +1 408 414 9201  
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