U2010B-MFP Datasheet, PDF (4/18 Pages) ATMEL Corporation – Phase-control IC with Current Feedback and Overload Protection

The series resistance R₁ can be calculated as follows:
R_1max = ^V-----^m----^a--ⁱ-₂ⁿ---^s-_´---–--_I--_t^V-_o---_tS----^m---^a---^x-
Voltage Monitoring
where:
V_mains = Mains supply voltage
V_Smax = Maximum supply voltage
I_tot = Total current consumption = I_Smax + I_x
I_Smax = Maximum current consumption of the IC
I_x = Current consumption of the external components
When the voltage is built up, uncontrolled output pulses are avoided by internal voltage
monitoring. Apart from that, all latches in the circuit (phase control, load limit regulation)
are reset and the soft-start capacitor is short-circuited. This guarantees a specified
start-up behavior each time the supply voltage is switched on or after short interruptions
of the mains supply. Soft start is initiated after the supply voltage has been built up. This
behavior guarantees a gentle start-up for the motor and automatically ensures the opti-
mum run-up time.
Phase Control
Automatic Retriggering
The function of the phase control is mainly identical to the well-known IC U211B. The
phase angle of the trigger pulse is derived by comparing the ramp voltage V₃, which is
mains-synchronized by the voltage detector, with the set value on the control input, pin
4. The slope of the ramp is determined by Cj and its charging current Ij. The charging
current can be varied using Rj at pin 14. The maximum phase angle, a_max, can also be
adjusted by using Rj (minimum current flow angle jmin), see Figure 5 on page 10.
When the potential on pin 3 reaches the set point level of pin 4, a trigger pulse width, t_p,
is determined from the value of Cj (t_p = 9 µs/nF). At the same time, a latch is set with
the output pulse as long as the automatic retriggering has not been activated. When this
happens, no more pulses can be generated in that half cycle. The control input at pin 4
(with respect to pin 10) has an active range from V₈ to -1 V. When V₄ = V₈, then the
phase angle is at its maximum, a_max, i.e., the current flow angle is minimum. The mini-
mum phase angle, a_min, is set with V₄ ³ -1 V.
The current-detector circuit monitors the state of the triac after triggering by measuring
the voltage drop at the triac gate. A current flow through the triac is recognized when the
voltage drop exceeds a threshold level of typically 40 mV.
If the triac is quenched within the relevant half-wave after triggering (for example owing
to low load currents before or after the zero crossing of the current wave, or for commu-
tator motors, owing to brush lifters), the automatic retriggering circuit ensures immediate
retriggering, if necessary with a high repetition rate, t_pp/t_p, until the triac remains reliably
triggered.
4 U2010B
4766A–INDCO–01/04