Single chip microcomputer STM32L151CCU6

Photocoupler

1. The fault phenomenon is: once started, the external fuse of the drive will be burned and the device will not run. During the inspection, the maintenance personnel found that a power tube was damaged, but because there was no data, it could not figure out the function of the tube. It thought that it was a power-driven front push, and replaced it with a power tube. After power-on, the insurance was burned again. The tube on it is also damaged. After the inspection by professional maintenance personnel, the initial analysis is correct, that is, the fuse is repeatedly blown, the stepper driver must have an abnormally large current, and a power tube is damaged. But the effect on the tube is not clear. In fact, the tube is a stepping motor power supply driving tube, and the stepping motor is a high voltage starting, and thus has to withstand high voltage and large current. Static inspection, in the circuit of the pulse ring distributor, the resistance of the power supply to the ground is small, but there is no short circuit. According to the number of components in the line and its power consumption, the resistance of the power supply to the ground should not be so small, so it is suspected that the components in the line are damaged.

2, power check, found that a chip is abnormally hot. After the power is turned off, the power supply pin of the chip is cut off, and the static check and the increase of the power supply to the ground should be normal. The resistance of the chip to ground is measured to be small. Check the model number of the chip, which is a non-standard model, which is not found in many manuals. After line analysis, it was confirmed to be the main component in the board: a ring pulse distributor.

3. To further confirm the problem of the chip, firstly change the stepper motor power supply tube with the same voltage and current power, restore the power supply pin of the chip, and replace the winding motor windings with the light-emitting diode circuit as the analog load. After the power is turned on, the light-emitting diodes are all bright, that is, the windings are all energized, which is not in accordance with the line requirements, and the input step pulse does not respond, so it is confirmed that the chip is damaged.

4. Solution: The chip is not on the market. In the case where the space inside the driver housing is allowed, a ring pulse generator is designed by using a combination line, that is, a combination of a D flip-flop and a NAND gate existing on the hand. On a small printed board, the original chip is removed and the small printed board is mounted on the pads of the original chip through the leads. The LED is still used as the analog load. After the power is turned on, the stepping pulse is applied to sequentially emit light in the phase sequence. Remove the simulated load, access the host, power on, and the device is operating normally.

5. This example shows that the maintenance personnel must not only be able to analyze the phenomenon (overcurrent), find out the obvious cause (power tube damage), but also be able to analyze the initial cause of the fault (pulse generator damage) step by step, and It is possible to replace difficult-to-solve device problems with existing component combinations on hand.