As shown below, I used a switch chip tny276pn, optocoupler pc817, regulator source tcl431 and some small components (capacitors, resistors, etc.) designed a 5Vdc switching power supply. Transformers are custom, according to the flyback type, 132kHz, 85 ~ 265Vac parameters to do. The upper right corner of the picture p2 end is a 20-30 ohm coil, and now found that the input voltage dropped to 20Vac, 5Vdc was unstable, coil control of the magnet was to jump, I would like to 20Vac this parameter increased to 60 ~ 80Vac, So that the coil control of the magnet in the low voltage when the high jump, how should modify the circuit? Thank you.
Always do not see the picture in the know. However, from the description point of view, this problem needs to change the way of thinking. It is contradictory to detect the voltage at the input of the power supply in a power supply output circuit with a regulated function.
In 20Vac was stable output, it is to ensure that the power supply in the 60 ~ 80Vac can work properly, should be the design margin, when the power load increases, the lower limit voltage will rise. Further, the lower limit to the present 20Vac, but also take into account the factors of load changes. In short, this is not a bad thing, no need to change the design to improve it, improve the possible impact of reliability.
The AC voltage should be measured at the input of the power supply, ie, the high voltage side. As the precision is not high, you can add a simple test circuit on the high side, such as with a 60V regulator in series with a light lotus (LED side, of course, have a current limiting resistor), the other side of the lotus ) There is an accurate action signal, with a S8050 transistor connected to the 5Vdc power control solenoid can be a.
In the electromagnet action, 5Vdc or stable, which can ensure the reliability of the operation of the electromagnet, will not produce jitter.
Thought is important, the circuit is very simple, not on the map, and recently know the map often shows no time, occasionally to see.
The maximum power of your power is 1.25W, the overall power supply power by 70% efficiency of 1.8W.
In this case need to modify the transformer. To the place there are the following:
1, the transformer to increase the ratio; such as the original is 200: 5, now changed to 300: 5. Now want to do your request 60-80VAC input protection, you need the current transformer parameters to be calculated;
2, the transformer sensation increased; proposed to change to 4mH ~ 8mH.
Once the two done, the protection voltage will rise.
The maximum power of the power is 1.25W, the overall power supply power by 70% efficiency of 1.8W.
In this case need to modify the transformer. To the place there are the following:
1, the transformer to increase the ratio; such as the original is 200: 5, now changed to 300: 5. Now want to do your request 60-80VAC input protection, you need the current transformer parameters to be calculated;
2, the transformer sensation increased; proposed to change to 4mH ~ 8mH.
Once the two done, the protection voltage will rise.
How do not provide transformer parameters?
The maximum power of your power is 1.25W, the overall power supply power by 70% efficiency of 1.8W.
In this case need to modify the transformer. To the place there are the following:
1, the transformer to increase the ratio; such as the original is 200: 5, now changed to 300: 5. Now want to do your request 60-80VAC input protection, you need the current transformer parameters to be calculated;
2, the transformer sensation increased; proposed to change to 4mH ~ 8mH.
Once the two done, the protection voltage will rise.
I am an electronic design engineer, is developing a 12V20A repair charger, you can add to my discussion.
