Advertisement
7.3. Current Limitation Control
This IC uses a chopper type control as a current limitation control. The current limitation control
makes it operate in the large current flowing at the time of locking a motor when the motor shaft
operation cannot be performed. Then the actuator is protected and the dissipation of this IC is reduced.
(An additional over-current protection circuit is prepared in other block at the time of the power
supply short or GND short.)
The current limitation comparator is arranged to the low side, and higher threshold is defined as
Ilim-H, and lower one is defined as Ilim-L.
Moreover blanking time is prepared inside, and if exceeding the time, it will be considered that the
current limitation is operated.
The value of Ilim-H is set to 6.5 A (typ.), and Ilim-L = Ilim-H - 0.25 A (typ.).
7.3.1. Chopper type current limitation control
The basic operation of chopper type current limitation is as follows.
Ｉlim-H: 6.5A
Ｉlim-L: Ilim-H - 0.25A
Note1: This area is
ignored.
PWM1
(PWM2 is fixed to L.)
tBLANk1：11.5μs
Current Limit
Toff_min
(20.5μs)
Note: Some of timing charts in this document may be omitted or simplified for explanatory purposes
<Basic operaton>
(1) Current is detected with Ilim-H(6.5A).
(2) The Blanking counter starts counting after the detection. The Current Limit signal rises at the falling
edge of tBLANK1 because the current flows more than Ilim-H(6.5 A) after passing the time
(tBLANK1: 11.5 μs).
(3) After Blanking, the motor drive output is set to the short brake mode (lower simultaneous ON)
automatically. Then the current is regained.
At the same time, Toff_min also rises to "H" and starts counting.
The PWM1 signal of Note1 is ignored in this case. (Toff_min is given the priority.)
(4) After passing the time of Toff_min (20.5 μs) the normal mode (Forward) returns if the value is lower
than Ilim-L.
(5) The motor drive current is increasing because PWM1 becomes "H."
<When a PWM signal is input at the time of Forward>
(6) It is detected that the current flows more than Ilim-H (6.5 A) after restarting the motor operation at
Toff_min falling edge.
tBLANK1(11.5 μs) counter starts.
(7) If PWM1 becomes "L" during Blanking, the motor output is set to the short brake (lower similtaneous
ON), and the current is regained.
(8) The short brake is held because the current value after Toff_min (20.5 μs) is more than Ilm-L.
(9) The current Limit becomes "L" since the Ilim-L is detected, and the normal mode returns.
(10) Since the PWM holds "H", the motor drive current is increasing.
(2)
(1)
(3)
11.5μs
20.5μs
Figure 7.3-1 Chopper type current limitation control
(6)
(11)
(4)
(8) (9)
(7)
(10)
(5)
20.5μs
13 / 49
TB9051FTG
(12)
(14)
ｔ
(13)
Ver.1.1 2019-03-14
Advertisement
