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(多图) 闭环DC-DC转换器网络分析仪的注入变压器设计

来源:电子产品世界?? 2005年09月22日 ?? 收藏0

Injection Transformers for Closed-Loop DC-DC Converter Network Analysis

?????? Operating a current transformer as a voltage transformer provides a cost-effective alternative to injection transformers sold as test accessories.Engineering labs often have a network analyzer, but few of them include an injection transformer for closed-loop analysis of dc-dc converters. Agilent sells such transformers as test equipment accessories, but they are expensive. Ridley Engine

ering and Venable also sell injection transformers. Over-the-counter injection transformers have impressive specifications, but they also have high prices. Remember, they are only transformers. As an alternative, you can obtain a cost-effective injection transformer by operating a current transformer as a voltage transformer.

?????? Wide bandwidth is the most difficult parameter to achieve when designing a transformer. On one hand, low- frequency performance requires a larger core and more turns, which increases the transformer's physical size. High-frequency performance, on the other hand, requires good coupling, small size and minimum turns.

?????? Fortunately, a current transformer is acceptable for most applications. For example, the PE-51687 from Pulse Engineering has a 100-turn primary on a ferrite core and no secondary winding. A hole through the core lets you custom wind any number of secondary turns using stranded wire. The wire serves as a connection to the circuit under test and provides a drive level according to the number of secondary turns.

?????? Because we're building a voltage transformer, we need to control the primary voltage. Given that the transformer's primary reactance is higher than that of the source, connecting a 50- resistor in parallel with the primary properly terminates the network-analyzer source. For low frequencies, the primary's inductive reactance must be higher than the Thevenin equivalent as seen by transformer (25 ). Because the PE-51687 has a primary inductance of 20 mH, the lowest frequency at which that transformer should operate is: Xl = 2*3.1416*Freq*Lprim.

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DC-DC? 网络? 分析仪? 变压器?


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