Datasheet U2010B (Atmel) - 4

link to page 10
3. General Description 3.1 Mains Supply
The Atmel® U2010B contains voltage limiting and can be connected with the mains supply via D and R . Supply voltage – between pin 10 and pin 11 – is smoothed by C . 1 1 1 In the case of V ≤ 70% of the overload threshold voltage, pins 11 and 12 are connected inter- 6 nally whereby V ≤ 1.2V. When ⏐ V ⏐ ≥ ⏐ V ⏐ , the supply current flows across D . sat 6 T70 3 The series resistance R can be calculated as follows: 1 V – V R mains Smax = ------------------- 1max 2 × Itot where: V = Mains supply voltage mains V = Maximum supply voltage Smax I = Total current consumption = I + I tot Smax x I = Maximum current consumption of the IC Smax I = Current consumption of the external components x
3.2 Voltage Monitoring
When the voltage is built up, uncontrolled output pulses are avoided by internal voltage monitor- ing. 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 isnitiated after the supply voltage has been built up. This behavior guarantees a gentle start-up for the motor and automatically ensures the optimum run-up time.
3.3 Phase Control
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 V , which is mains-synchro- 3 nized by the voltage detector, with the set value on the control input, pin 4. The slope of the ramp is determined by Cϕ and its charging current Iϕ. The charging current can be varied using Rϕ at pin 14. The maximum phase angle, α , can also be adjusted by using Rϕ (minimum max current flow angle ϕmin), see Figure 7-1 on page 10. When the potential on pin 3 reaches the set point level of pin 4, a trigger pulse width, t , is deter- p mined from the value of Cϕ (t = 9µs/nF). At the same time, a latch is set with the output pulse as p 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 V to -1V. When V = V , then the phase angle is at its maximum, α , i.e., the 8 4 8 max current flow angle is minimum. The minimum phase angle, α , is set with V ≥ –1V. min 4
4 Atmel U2010B
4766D–INDCO–03/11 Document Outline Features Applications 1. Description 2. Pin Configuration 3. General Description 3.1 Mains Supply 3.2 Voltage Monitoring 3.3 Phase Control 3.4 Automatic Retriggering 3.5 Current Synchronization 3.6 Voltage Synchronization with Mains Voltage Compensation 3.7 Load-current Compensation 3.8 Load-current Limitation 3.8.1 Mode Selection 4. Absolute Maximum Ratings 5. Thermal Resistance 6. Electrical Characteristics 7. Diagrams 8. Ordering Information 9. Package Information 10. Revision History