IEC 61000-4-4 Burst immunity test
UM0583
16/23
5
IEC 61000-4-4 Burst immunity test
5.1 Test
conditions
●
Ambient temperature: 25 °C
●
Relative humidity: 35%
●
Test performed in accordance with IEC 61000-4-4
5.2
Demonstration board immunity test
The AC line input X2 capacitor C15 (10 nF) is used to help avoid triggering the AC switch
(ACS108-6S). The MCU program reads the AVF signal at each AC line peak voltage (see
Figure 12
). The AC switch state detection is deducted if the AVF signal remains at the same
level for three consecutive AC line cycles.
Figure 12.
AVF signal detection
The demonstration board and mains wires are placed 10 cm above the ground reference.
The mains wire is shorter than 1 m. Each operating cycle has been tested (load OFF and
ON). The burst withstanding level is higher than 4 kV without spurious triggering of the ACS
or ST7Lite3 MCU loss, whatever the coupling mode (to L, N, PE, etc.).
5.3
Recommendations for improving application immunity
To improve application EMC performance, the software must be EMC-oriented (for more
information please refer application note AN1015):
●
Auto-recovery routine. At each RESET interrupt, the program must check if the data in
the RAM are stored as scheduled. Indeed, a RESET can occur without the supply
voltage having fallen below V
RM
(data retention parameter). In this case, a complete
startup is not necessary, and the program can continue working with the previous RAM
ZVS
V
AC
TIMER
ZVS detection => TIMER ON
ZVS delay
> T/4 ms
T/2 ms
READ AVF and TIMER OFF
READ AVF and TIMER OFF
ZVS detection => TIMER ON
ZVS delay
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