STMicroelectronics STEVAL-GLA001V1, Руководство пользователя

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Figure 24. Soft-start operation (on the left) and soft-stop operation (on the right)
Wait for next zero
voltage crossing
tp_1
td_1 td_(x-1)
tp_(x-1)
td_2
tp_2 tp_1
td_1 td_(x-1)
tp_(x-1)
td_(x-2)
tp_(x-2)
Triac gate
command
V
MAINS
td
tp
td
tp
All parameters (range, default value, unit, step, etc.) used to configure the load control for this mode are
described in
Section 3.6 User interface . For more details regarding the hardware components used for this mode,
refer to Section 2.5 Hardware function description .
3.4 ZVS function
The ZVS (Zero Voltage Switching) function allows control of the loads in synchronization with the mains voltage,
which is especially useful for avoiding excessive dI/dt at turn ON that can damage the AC switches. The ZVS
signal versus mains voltage is shown below.
Figure 25. ZVS signal versus mains voltage (zoom on the right)
The real ZVS signal is not exactly synchronized with mains voltage due to component tolerance and delay. A
virtual delay “td_zvs” is implemented in the
NUCLEO-F030R8 development board firmware to counter this
problem. You measure it with an oscilloscope and modify the value through the user interface (for more details,
refer to firmware user manual).
In case of inductive load use, you must take into account the delay due to the
STEVAL-GLA001V1 evaluation
board and the phase shift due to the load. By adding these two delays, you can control the inductive load exactly
at the zero current crossing.
Figure 26. Parameters in case of inductive load (example on the right) shows an example of inductive load use:
the “Final value” entered in “td_zvs” should be the difference between the “td_zvs” delay and the inductive load
delay. For example, “td_zvs” due to the STEVAL-GLA001V1 is 1000 µs, and inductive load delay is 2500 µs: the
final value is “td_zvs” – “inductive load delay” = 1000 – 2500 = –1500 µs.
Figure 26. Parameters in case of inductive load (example on the right)
In phase control mode, the “zcs_margin” parameter lets you avoid period overlap. This parameter should be taken
into account in "td" calculation: a half-period should be equal to the sum of “tp”, “td” and “zcs_margin” as shown in
Figure 27. Parameters for phase control mode .
UM2304
ZVS function
UM2304 - Rev 3
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