04-16-2014, 04:21 PM
I just checked the 80 Rect datasheet again and it lists max peak transient plate current at 2.2 amps.
In my simulator I get about 890mA peak plate current for the very first cycle of the 120 Hz. So, I think I'm OK. I have made some assumptions about the 80 Rect. model which I think are close, I modeled it as two 1N4007 diodes each in series with 300 ohms. Even if I'm off by a factor of two on the 300 Ohms I'm still OK.
Also, the 1.5K resistors seem to really isolate the later two Caps from the startup transient. Making them 10uF instead of 22uF hardly
changed the first cycle peak current at all.
This makes sense as the dominant factor is charging the input cap
(here 10uF directly from the 80 rectifier output). Initially that cap
looks like a dead short so the current is limited by the impedance
of the 80 rect. plus whatever transformer resistance and leakage inductance there is.
The two C's on the other side of the 1.5Ks don't seem to factor
in at all to that first cycle peak current surge.
Herb S.
In my simulator I get about 890mA peak plate current for the very first cycle of the 120 Hz. So, I think I'm OK. I have made some assumptions about the 80 Rect. model which I think are close, I modeled it as two 1N4007 diodes each in series with 300 ohms. Even if I'm off by a factor of two on the 300 Ohms I'm still OK.
Also, the 1.5K resistors seem to really isolate the later two Caps from the startup transient. Making them 10uF instead of 22uF hardly
changed the first cycle peak current at all.
This makes sense as the dominant factor is charging the input cap
(here 10uF directly from the 80 rectifier output). Initially that cap
looks like a dead short so the current is limited by the impedance
of the 80 rect. plus whatever transformer resistance and leakage inductance there is.
The two C's on the other side of the 1.5Ks don't seem to factor
in at all to that first cycle peak current surge.
Herb S.
