EEVblog Electronics Community Forum
A Free & Open Forum For Electronics Enthusiasts & Professionals
Welcome,
Guest
. Please
login
or
register
.
Did you miss your
activation email
?
1 Hour
1 Day
1 Week
1 Month
Forever
Login with username, password and session length
This topic
This board
Entire forum
Google
Bing
Home
Help
Search
About us
Links
Login
Register
EEVblog Electronics Community Forum
»
General
»
General Technical Chat
»
Lower gain feedback transistor outputs more power on HV trans secondary, why?
« previous
next »
Print
Search
Pages: [
1
]
Go Down
Author
Topic: Lower gain feedback transistor outputs more power on HV trans secondary, why? (Read 858 times)
0 Members and 1 Guest are viewing this topic.
gkmaia
Frequent Contributor
Posts: 532
Country:
Electronics Hobbyist
Lower gain feedback transistor outputs more power on HV trans secondary, why?
«
on:
December 03, 2019, 09:44:33 pm »
I got a few Lecroy(siglent) WaveAce.
In one of them, the LCD backlight was a bit dim and I suspected the inverter was not supplying enough power to the backlight.
So I replaced Q3 and Q2 for new ones and backlight now is much brighter.
When I replaced them I tested both the old and the new one on my BK curve tracer. These are the results:
- OLD D1802 / Beta: 350 / Display brightness LOW
- NEW D1802 / Beta: 150 / Display brightness HIGH
As Q2/3 drive the oscillation on the primary I am curious to understand why a lower gain transistor on primary/feedback outputs more power on the secondary
Logged
Zero999
Super Contributor
Posts: 19886
Country:
0999
Re: Lower gain feedback transistor outputs more power on HV trans secondary, why?
«
Reply #1 on:
December 03, 2019, 10:03:30 pm »
My guess would be that having a lower beta, it's not driven so far into saturation, therefore will turn off faster, resulting in lower switching losses and higher efficiency, so a brighter light.
Logged
The following users thanked this post:
gkmaia
Print
Search
Pages: [
1
]
Go Up
« previous
next »
Share me
Smf
EEVblog Electronics Community Forum
»
General
»
General Technical Chat
»
Lower gain feedback transistor outputs more power on HV trans secondary, why?
There was an error while thanking
Thanking...
EEVblog Main Site
EEVblog on Youtube
EEVblog on Twitter
EEVblog on Facebook
EEVblog on Odysee