Can power modules be used in parallel? !

In actual projects, it is often the case that a power module cannot meet the current requirements of the load, or if you want to further improve the DCDC efficiency, most engineers will first think of paralleling the power supply to increase the current. For such a design, the usual evaluation result is: do not parallel roughly.

It is true that connecting power supplies in parallel helps reduce heat dissipation, improve efficiency, and provide greater output power. However, a simple parallel design is not reliable.

Some people say that when power supplies are connected in parallel, it is easy for backflow to occur, causing the current of one power module to flow into the second power module. All you need to do is add a diode to prevent backflow.

However, this consideration is not comprehensive enough. Engineers who have applied it in practice may find that when connecting power modules in parallel, sometimes one power module will continue to output while the other power module has no output, or one circuit will heat up severely, and the result will not meet expectations.

We use 1.8V BUCK power supply to specifically analyze the topology of dual power supply.

In the figure below, R1=R2=0Ω . To prevent backflow, diodes are connected to both buck inputs, and the sense is behind the diodes to offset the effect of the diode conduction voltage and ensure that the voltage at point A is 1.8V. In fact, the buck output is higher than 1.8V.

Due to the differences between devices, it is impossible for the outputs of BUCK1 and BUCK2 to be completely equal when they reach point A. Assuming that the voltage of BUCK1 reaching point A is higher than that of BUCK2, BUCK2 sense finds that the voltage is higher than the set value, so it reduces its own output, and finally only BUCK1 is in the output state.

Common name: drought kills, flood kills

Or: One core is in trouble, eight cores are watching

The resistance value of R1R2 can be changed to generate a voltage divider to offset the difference in the output voltages of the two BUCKs, allowing both bucks to work.

However, in actual project applications, I still do not recommend direct parallel use. It is best to choose a power module that supports discharge equalization for parallel connection. For most general power supplies, it is best to use them alone.

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