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Anonymous users2024-02-08Theoretical formulas have their own algorithms and can only be referred to. The answer can only be obtained in experiments.
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Anonymous users2024-02-07vf=vmos-vindcmax-150v。
1. The transformer of the single-ended flyback switching power supply is a coupling inductor in essence, which should undertake the work of energy storage, voltage transformation, and energy transmission.
2. In the flyback converter, the sum of the secondary-side reflected voltage, i.e., the flyback voltage vf and the input voltage, should not be higher than the withstand voltage of the main switch, and a certain margin should be left (150V is assumed here). The flyback voltage is determined by the following formula: VF = VMOS-VINDCMAX - 150V.
3. The relationship between the flyback voltage and the output voltage is determined by the turns ratio of the primary and secondary sides. Therefore, after the flyback voltage is determined, the turns ratio of the primary and secondary sides can be determined.
Fourth, the maximum turbulent ratio of flyback power supply appears in the state of the lowest input voltage and maximum output power, according to the magnetic balance of the transformer in the steady state, there can be the following formula: vindcmin dmax=vf (1-dmax).
5. Whether the current (ampere) of the inductor (including flyback transformer) is continuous or intermittent: In the converter in intermittent mode, the inductor current is zero at some point in the cycle. The continuous current (ampere) is to have a sufficient amount of inductance to maintain the minimum load current ilmin (including false loads), and the inductor should have current flow at any point in the cycle.
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Anonymous users2024-02-06The books you read will come and get you in. I went around the source for a long time, but I couldn't find myself. In fact, the flyback transformer is very easy to calculate, which is basically based on experience, supplemented by formulas.
For example, for 12V1A transformer, first determine the size of the transformer based on experience, of course, you have to determine what type of transformer to use according to the actual situation of the shell and board, such as EE, EF, and EFD, and then RM, PQ...Wait, followed by the size, the classic transformer of 12W is EF20, first according to experience, we know that the primary of 12W is about 90 turns, then calculate the secondary, the secondary voltage ratio and the turns ratio are equal, 12V*, the minimum input voltage is 90V*, and then 127 17= This is their voltage ratio, that is, the turns ratio, and then use the primary turns 90 This is the number of secondary turns. I understand that it is 90V input and 12V output, which is calculated by the maximum duty cycle, and the inductance is also calculated by formula, LP=VIMIN*DMax IPK*F IPK=2PO DMAXVIMIN, which is about a MH, but the inductance calculated by experience is a little more than the actual application, so we generally take.
This frequency is based on 67K.
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Anonymous users2024-02-05It is determined according to the output voltage requirements, the withstand voltage of the MOS tube, and the peak current of the transformer. There is no fixed formula for calculating it.
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Anonymous users2024-02-04The design of flyback switching power supply transformer should start from the number of turns of the primary stage, and the maximum voltage stress of the switch, the most important parameter of the ratio of the number of turns of the initial stage, should be designed according to the idea of inductor in order to be successful.
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Anonymous users2024-02-03The method is fine, and the sensitivity value is not too big, I have made one before, and the sensitivity value is about the same.
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Anonymous users2024-02-02How is the primary inductance so big?
Primary inductance calculation formula:
The difference between forward and flyback of switching power supply is as follows: >>>More
Hello, this problem is very easy to explain, the energy stored by the transformer when the flyback switching power supply is no-load, there is a charge for the post-stage capacitor, and the false load is also absorbed by RCD (not all, RCD only absorbs the energy generated by the transformer leakage inductance, and consumes it with R heating), as well as the MOS tube, and the switching loss of the post-stage rectification, because there is a turn-on and turn-off, it must be a loss, just a matter of size, the duty cycle of the switch tube conduction at no load is very small, So the stored energy is very small (as far as the transformer is concerned, not to mention the pre-amp capacitor, you are also asking about the transformer), the loss of the machine itself is very small (but there must be a loss when each component is energized), used to maintain the voltage stabilization of the power supply, feedback, etc., you can add a power meter at the input AC end, and the power loss is generally less than 1W, so it is very small.
50Hz, 220V 60W bulb, 270mA current, series into the transformer winding, even if the transformer's own other windings have been short-circuited, or artificially short-circuited other windings, according to the transformer electromagnetic principle, the primary current emergency increases dramatically, but due to the current limiting effect of the 60W bulb (270mA), will it heat up? In addition, the winding of the high-frequency switching transformer working above 40kHz, for the 50Hz alternating current frequency, its inductive reactance is very small, far less than the impedance of the bulb, which is similar to the DC impedance, and the result is; The bulb is always on, the transformer is slightly cool, because of the theoretical analysis, I have not used this method, for reference, I use the boiling method, I hope to really practice the peer correction, similar methods, commonly used in electrician maintenance, for the power frequency transformer, the motor winding is added to the low-voltage alternating current heating up and softening and removal,
The LED driver is actually a switching power supply, which generally has the role of soft start and constant current. For 220V power supply, a switching power supply with an isolation transformer is used because the voltage needs to be greatly reduced. If it is used for 12 volt and 24 volt power supply, there is generally no need for a transformer.
The output three wires should be dual 18V transformers, output after 18V rectification, and output after 36V finishing. When overhauling electrical appliances with electricity, even if the voltage is not too high, you should be careful, safety is the main thing, right? The voltage of V is dangerous, and it is necessary to pay attention to safety when operating.