仿真应用问答

1. 能否介绍一下变压器的建模？
If you want to simulation the transformer , you must know the primary inductor value and secondary inductor and using the K factor connect the two wire. you can change the coupling factor K .e.g 0.99 for simulation it. Detail you can see the presentation files page 12.

2. 开关电源的最优化的仿真主要有那些内容
It is include the average simulation and switched simulation, Average simulation is used to measure the phase and gain margin and the switched simulation is using to simulated the detail switch waveform.

3. PSPICE与Saber比较，您感觉谁更适合电源仿真？
PSpice is a general purpose simulator and the Saber is a system level simulator only. PSpice can help you to investigate the circuit performance down to details.

4.能否解释一下为什么平均模型不能分析电流环的原因，谢谢
This is related to the internal structure of model. Dr. Ridley has provided an average model that work for both voltage and current loop. However, this is a AC small signal model that cannot calculate bias point and predict transient performance.

5. 在采用开关模型仿真的时候经常会遇到不收敛的情况，请问吴先生怎样才能很好的解决这个问题？
The convergence problems usually happen in SMPS simulations. There are several methods for solving this problem. The transient simulation time step can increase. The large number of simulation steps in each time step can avoid in some difficult point.
The GMIN optin in the option can be used for DC bias point to solve the convergence problem.
Some other option (i.e. ITL4=1000) will affect the tolerance of the simulation. This should be carefully considered in your design.

6. Pspice能否对电源的保护功能如过流过压过热保护等进行仿真模拟？效果如何？
Pspice simulation can also include the over current proctection, over voltage protection. These functions is similar to soft-start functions and other functions of the controller and SMPS. But the thermal effect usually does not be contained in the this level simulation. Except this thermal effect. Other protection functions can be simulated effectively.

7. 开关电源中最难设计、又最难调试的是高频变压器,Pspice在这方面能发挥多大作用？这套软件是否只能对安森美器件有用?软件哪里有提供？
Yes, you are right. If there is no pspice circuit to help you doing simulation. You will waste a lot of time to build a breadboard for testing. PSpice is a kind of circuit simulation that you can use computer to simulate your circuit. And it nevers blows out your circuit whether you put any component value on it.
For designing the high switching frequency converter. You can refer to page 12 of the slide. First, you add a ideal transformer on it. And then choose the primary magnetizing inductance of the transformer with its" leakage. Then combine with the pwm model and other components. Then you can simulate your circuit. After finished the simulation, you can click on the probe icon to add some probe on the node to see the voltage, current. By looking the waveform, so you can modify the components value to make your design as your expection.
Pspice is not the only software for Onsemi Parts. You can click on the link http://www.cadencepcb.com/products/pspice/
and choose the student evaluation. This is free version. Of course, there are limitation of this version. Also you can buy a full version of PSpice.