DC-DC control ICs are widely used in various electronic products. In order to unify materials, engineers often use DC-DC chips that they are familiar with and can output large currents. Regardless of the load size, one model is used. Therefore, the efficiency may not be satisfactory when the load current is small, how to solve it?
1. Consider the choice of LDO and DC-DC converters from the aspect of efficiency
LDO: The input voltage and the output voltage are not much different, and when the current is small, the LDO chip can be selected;
The power loss of the LDO can be seen from the formula. When the voltage difference between the input and output is large, or the output current is large, the power loss is high, the heat is more serious, and it cannot be used in many designs, but if it is Low dropout, LDO is very suitable for small currents, and the price is relatively low.
DC-DC converter: When the input and output voltage differences are large and a large current is output, the DC-DC chip must be selected.
The power loss of DC-DC is related to the internal process design of the chip. The efficiency is different in different use cases. If the selection is reasonable, the efficiency can reach more than 90%, the power loss can be very low, and it can be adapted to various occasions. Meet the needs of the designer.
2, the choice of conventional step-down DC-DC
Old solution: In the past few years, most of the DC-DC chips used were inefficient due to process problems. For example, for 36V input 5V/3A output applications, most engineers use products with a suffix of 2576. The efficiency curve is shown in Figure 1:
figure 1
The efficiency curve can be seen from Figure 1. At 5V output, the output current is below 80% when the output current is 200mA or 3A, which is difficult to meet more and more stringent energy requirements.
Moreover, due to the large power loss, most of the packages are TO-220 or DDDRK, which are bulky and occupy a large area of ​​PCB.
The new scheme: the new process DC-DC model MP4423 represented by MPS, the input voltage is 40V, the efficiency can reach more than 90% at 5V output, which can meet the application in most occasions.
figure 2
3, the choice of modular DC-DC
In addition to using the chip's own DC-DC solution, if it is limited by the volume or project schedule time, another type of modular DC-DC is a suitable choice, such as the ZY78xxS series from ZLG, the pin is compatible with the traditional 7805. The size is small, the efficiency is generally above 90%, which can greatly reduce the complexity of the design.
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