CR1632 battery

　　Introductory circuit knowledge of power supply: primary and secondary series and parallel connection of transformer

　　Power transformers are the same as ordinary devices. During emergency operations, multiple transformers can be used in series and parallel under certain conditions. For example, commercially available power transformers can fully meet the requirements. When the transformer power meets the requirements but there is no suitable voltage, two or more transformers can be used in series; when the voltage meets the requirements but the transformer power is not enough, two or more transformers can be used in parallel to meet the requirements. Circuit power requirements. The power transformer is composed of an inductor coil, so it completely follows the operation rules of the inductor. You can connect the primary of the power transformer in series or the secondary of the output. The four situations are introduced below.

　　1. Primary series connection of power transformer

　　In the transformer calculation formula, there is a constant N called the turns ratio, which is the ratio of the primary turns to the secondary turns. The primary-to-secondary voltage ratio is N, and the primary-to-secondary current ratio is 1/N. For example: two A transformer with a primary of 220V and a secondary of 18V, N is 13. If the primary of the two transformers are connected in series, the output voltage on a single secondary will drop below 9V. In this case, when the secondary voltage of a single transformer is higher than the power supply of the multiple electrical appliances, two or more primary transformers can be used in series. However, if the two secondary circuits are connected in series, they will not be of much use value. In this case, as long as the power requirement of a single transformer is guaranteed, the secondary output voltage is not necessarily the same. Its output voltage is calculated as: V single = (V1 times + V2 times +...Vn times)/Vn.

　　2. Secondary series connection of power transformer

　　The secondary series connection of a power transformer is a combination of two or more transformers when a single power is sufficient but the secondary output voltage is not. For example, when the primary input of two transformers is 220V and the secondary output is 18V, if you want to supply 33V to the load, the secondary of the two transformers can be connected in series. It is also very easy to connect the secondary of the power transformer in series. Different secondary outputs can also be used in series as long as the power of a single transformer is ensured. Under ideal conditions, when the primary input voltages of multiple transformers are the same, the total output calculation formula is: V total = V primary / (V1 times + V2 times +...Vn times).

　　3. Primary parallel connection of transformer

　　This situation is a common example in our lives. The remote control transformer and the main transformer (power switching transformer) in multiple old-fashioned color TVs with different power supplies are all connected in parallel at the primary level of the transformer. 4. Secondary parallel connection of transformer

　　The secondary parallel connection of power transformer is used when the secondary output voltage of a single transformer is the same but the single power cannot meet the requirement. Its application is to superimpose the secondary currents of multiple transformers to meet the power needs of the load. The secondary of the power transformer is connected in parallel, so that the output power is the sum of the powers of multiple transformers.

　　The series-parallel application of power transformers does not distinguish between linear power supply circuits and switching power supply circuits. In the previous linear power supply circuits, there were more application examples of secondary series connection. For example, the reverse-pass transformer in the TV set used the series connection of the secondary of the transformer. In today's high-power switching power supplies, there are more applications of secondary parallel connection. For example, in switching power supplies with hundreds of watts, the secondary of the transformer is often connected in parallel to increase the power. Pay attention to the following points when applying series and parallel power transformers:

　　(1) When connecting power transformers in series and parallel, pay attention to the same terminals of the transformers. When used in series, they must be in series and not in reverse. When used in parallel, the same terminals must be in parallel with the same terminals, otherwise the transformer will be burned.

　　(2) The above calculation is only an ideal algorithm, but in fact the loss of a single transformer after they are connected in series and parallel is very large. The secondary output voltage of each power transformer will be lower than the result calculated by the above formula.

　　(3) If different secondary outputs are to be used in parallel, it is best to do it after voltage stabilization, and the parallel voltage is the lowest voltage value among the transformer outputs. When the secondary circuits are connected in series, they can be directly connected in series, or they can be connected in series after voltage stabilization.

　　(4) A common ground in the power circuit is necessary. Potential comparisons and voltage calculations are only possible with a reference point.

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