DC 16V to 5V

electricor

DC 16V to 5V [Copy link]

 

Why does the simulated 5v increase slowly? I don't know what went wrong.

qwqwqw2088

There is no problem with the circuit design, but the parameters of the components, the inductor, MOS tube, and the rated current of the diode. I don't know if the C9 capacitor is a bit small. It can be adjusted in the simulation software. The actual circuit should be loaded to confirm.

electricor

qwqwqw2088 posted on 2018-8-6 07:52 There is no problem with the circuit design, but the component parameters, inductor, MOS tube, and the rated current of the diode. I don’t know if the C9 capacitor is a bit small for simulation software...

I changed the C9 capacitor to 470uf, but it still increases slowly. I also want to ask, is the input capacitor of 3.3uf too much?

maychang

1. Where is the load of the simulation circuit? Without a load, it is not a real working state. 2. The output voltage of the switching power supply is of course zero at the beginning of the simulation, and then gradually increases to the rated value. It is a slow increase in nature and it is impossible to reach the rated value immediately after the simulation starts. The simulation is calculated step by step, and the calculation process is slower than the actual process (the simulation time may be hundreds or even thousands of times longer than the actual circuit use time).

electricor

maychang posted on 2018-8-6 09:34 1. Where is the load of the simulation circuit? Without load, it is not a real working state. 2. The output voltage of the switching power supply is of course zero at the beginning of the simulation...

Oh, that's it. Thank you very much

maychang

electricor posted on 2018-8-6 09:43 Oh, I see. Thank you very much.

You chose IRF540, which has a maximum continuous current of 28A. Do you really need such a large current?

electricor

maychang posted on 2018-8-6 14:51 You chose IRF540, which is a tube with a maximum continuous current of 28A. Do you really need such a large current?

First of all, thank you very much for your careful answer. I only need 3A current, but will it have any impact if I use this tube? If there is a big impact, what model should I use?

maychang

electricor posted on 2018-8-6 21:29 First of all, thank you very much for your careful answer. I only need 3A current, but will it have any impact if I use this tube? If there is a big impact...

The larger the tube capacity (maximum reverse withstand voltage, maximum forward current), the larger the tube volume, and the more expensive it is. The first impact is of course the cost, and the second is that the larger the capacity of the tube, the higher the driving capability required. Therefore, it is necessary to choose the right tube according to the output voltage and current.

qwqwqw2088

electricor posted on 2018-8-6 08:24 I changed the C9 capacitor to 470uf, but it still increases slowly. I would also like to ask, is the input capacitor 3.3uf too much?

I still recommend taking a good look at the requirements of the LM5117 manual. The LM5117 is generally in the range of 200-300KHz. It must be set within the range required by the chip. If it is 100KHz, there should be problems if it is not in the frequency range. The simulation chip model sometimes also affects the simulation effect. The simulation circuit needs to simplify the components. From C13 to C18, a bunch of capacitors are connected in parallel. I don’t know what they are playing. If you really want to make the circuit of this chip, it is best to apply for a sample to build an actual circuit, otherwise it is all just talk.

maychang

electricor posted on 2018-8-6 21:29 First of all, thank you very much for your careful answer. I only need 3A current, but will it have any impact if I use this tube? If there is a big impact...

In fact, 16V is reduced to 5V, 3A output current, Texas Instruments has many types of chips, and the power MOS tube has been built into the chip. Such chips are very simple to use and do not have so many peripheral components. You can enter your requirements on the official website of Texas Instruments, and the website will help you choose the appropriate model.

electricor

qwqwqw2088 posted on 2018-8-7 07:47 I still suggest you take a good look at the LM5117 manual for requirements. The LM5117 is generally in the range of 200-300KHz, and you need to set it within the range required by the chip...

Hmm, ok, thank you