Conclusion

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Doc ID 15727 Rev 1

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Conclusion

MCUs supplied from negative 3.3 V power supplies are good replacements of 5 V supplied

MCUs for the control of ACS/TRIACs.

It is possible to design gate control circuits that provide enough current for triggering the

ACS/TRIAC. Calculations of proper gate resistors have been provided.

supply. They do indeed allow the power supply consumption to be reduced compared to

TRIACs.

The design of a 3.3 V power supply has to achieve a good accuracy (±5%) to reduce gate

current variation. A capacitive power supply cannot provide the accuracy required. An

SMPS with additional regulation has to be used.

The maximum gate current must meet MCU operating conditions. Refer to the maximum I/O

port current capability. The maximum current capability for any I/O of the STM32 port is 20

mA. One I/O pin to control the Z0103 is sufficient. Putting the I/O ports in parallel in order to

control the less sensitive devices is possible and could also be implemented.

The maximum MCU GND current capability is another parameter that has to be met. The

STM32’s current capability is 150 mA. The STM8S has different current capabilities for

different power supply ratings: 160 mA for a 5 V power supply, and 80 mA for a 3.3 V power

supply.

The average gate current consumption has to meet the capability of the power supply

current. The average gate current can be reduced using pulse gate control. This is

especially efficient for boards where several ACSs or TRIACs are controlled at the same

time.