Conclusion

AN1379

8/10

Doc ID 8317 Rev 5

3

Conclusion

The IEC 61000-4-4 standard requires that for systems working on public power networks,

the system must operate without any problem during burst voltages up to 1 kV. It has been

shown that thanks to the mains filter, which is commonly added in washing machines in

order to reduce the noise generated by universal motor brushes, Triacs and ACSs of 5 mA

sensitivity can pass the standard requirements. However, some manufacturers increase the

burst level up to 2 kV. In this case, only ACSs will fulfill the requirement without additional

components.

As for the Triacs, they will turn on due to high dV/dt rates. An RC circuit must then be added

to even out the dV/dt and designers must manage the following trade-off:

1.

Reduce dV/dt rates: The snubber capacitance must be high and the snubber

resistance must be low.

2.

Reduce the dI/dt rate at turn on: The snubber capacitance must be low and the snubber

resistance must be high.

Along with the fact that these snubbers and the varistors are no longer required with ACSs,

using ACS reduces design time and increases electronic board reliability.

References

1.

“Thyristors and Triacs: holding current - an important parameter”, Application note

AN302, Revision 3, STMicroelectronics, March 2008.

2.

L.Gonthier, “A New Solid State Switch for Home Appliances”, International Appliance

Technical Conference, West Lafayette, Indiana (USA), May 1999.

3.

L.Gonthier, “A New Overvoltage-Protected Logic Level AC Switch Thanks to Functional

Integration”, European Conference on Power Electronics and Application (EPE'99),

Lausanne (Switzerland), September 1999.