| ??? 09/21/10 07:42 Read: times |
#178618 - Avoid driving gate all the way to next zero crossing Responding to: ???'s previous message |
You sometimes talk about 30% voltage and sometimes 30% power. Note that an increased voltage also increases the current so the power increases with the square. So it really is important to decide if you want/need 30% of max voltage or of max power.
Yes, I think you should give long drive pulse to triac instead of your previous four short pulses. But watch out from driving the triac all the way to next zero crossing. If your zero crossing detector fails or your code is late to respond, then a still driven gate will mean the triac will directly start on the next half-period. Having a sw timer that always makes sure that you stop driving the gate before next zero crossing assures that a failed zero-crossing detector will not lead to the heater staying at 100% power. In your case, such a timer is easy since you don't need to use phase control very near 100% - you can switch to counting half-periods long before you start to need 100% power so you will always have ample time from the time of ignite until the next zero crossing. |
