powerSTEP01
Phase current control: current mode
Figure 21. Adaptive decay - fast decay tuning
1st fast decay:
Tfast = TOFF_FAST/8
3rd fast decay:
Tfast = TOFF_FAST/2
Ton > TON_MIN
Tfast = TOFF_FAST/2
2nd fast decay (*):
Tfast = TOFF_FAST/4
reference current
(*)Note: starting from 2nd fast decay the system combines
fast and slow decay during the OFF phase.
AM15050v1
When two or more fast decays are performed with the present target current, the control
system adds a fast decay at the end of every off-time keeping the OFF state duration
constant (tOFF is split into tOFF, SLOW and tOFF, FAST). When the current threshold is
increased by a microstep change (rising step), the system returns to normal decay mode
(slow decay only) and the tFAST value is halved.
Stopping the motor or reaching the current sinewave zero crossing causes the current
control system to return to the reset state.
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STMICROELECTRONICS [ ST ]
