AN440 STMICROELECTRONICS | Alldatasheet
Document overview
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Technical content
1 Principle of proposed gate circuit
Figure 2. Basic diagram of the triggering circuit through R1 and Tr and a negative current flows through the TRIAC gate.
- The TRIAC gate triggering current (IGT).
- The time duration of the gate current pulse.
- The TRIAC latching current (IL) especially for low rms current loads. + Vcc LINE I/O MCU GND LOAD D R1C TRIAC Tr + Vcc GND + Vcc I/O MCU GND LOAD D R1C TRIAC Tr + Vcc GND
2 Gate current pulse width setting
component to remain in the conducting state after the gate current IG has been removed. Figure 3. Gate control principle
Figure 5. Capacitance value versus supply voltage for different sensitivities
3 Experimental results
- TRIAC = BTA08-600CW
- IRMS = 2.12 A (load power: 500 W)
- Line voltage: 230 V rms, 50 Hz
- VCC = 5 V
- R1 = 36 Ω
- R2 = 300 Ω
- C = 3.3 µF
Figure 6. Triggering at zero current The component values are given in the following table for different application cases. Table 1. Component values for 3 different cases. TRIAC: BTA08-600CW
4 Conclusion
addition of a capacitor and a diode to control each TRIAC. phase lag between current and voltage. current and avoids all triggering. This factor acts as a safety feature. dc gate current is required. capacitor and diode. This solution is then easier and cheaper.
5 Revision history
Table 2. Document revision history 23-Apr-2004 2 Style sheet update. No Content change.