CN3768_12V_4A lead-acid battery charging board

Since there is no battery, the actual measurement using an electronic load shows that the output current can be stabilized to 3.95A. However, the inductor squeaks loudly. There should be no solution. It is a problem with the inductor manufacturing process. There is heat. When a heat sink is added to the back, the measured temperature is probably stable at around 70 degrees Celsius. The inductor itself basically does not generate heat. This may be due to the 3 milliohm DCR of the flat wire inductor. This is something that many ordinary inductors cannot do. of.

In addition, Infineon's PMOS IPD042P03L3 (the measured Rds is very low, about 3 milliohms), but it also generates heat, which is very slight.

In addition, during the test, the maximum current can reach 6A without pressure, which is not the 4A mentioned in the CN3768 datasheet. The maximum current depends on the selection of R1 R6 series sampling resistors (i.e., the Rcs resistor in the datasheet). Currently, four 0.06R 3W resistors are used in the test. When the alloy resistors in the 2512 package are stacked, the maximum current can reach 6A, but the heat is slightly larger. When a heat sink is added, the infrared temperature measurement is about 87 degrees Celsius.