msc

原帖由 FireBlack 於 2009-7-23 12:54 PM 發表

This is incorrect. You cannot connect a constant current source with a constant voltage circuit.

限流 means you can use any current you like, but not exceeding a certain limit. It is not the same as ...

响 Power Supply 既限流掂解唔等如恆流, 可唔可以講出你對限流同恆流既法, 我本人覺得無乜分別.

Amuro

原帖由 poonpoon 於 2009-7-23 23:03 發表


讀工程唔係考文學,唔洗文法好,沙士比罅咁文彩.
但係作為過來人,好清楚明白,科研如果開始( 無錯只係開始 ) 爬入理論領域,
英文同數學無番咁上下,係無辦法入門既.
一個連入門都唔得既人,可唔可以 design IC ???

佢只不過係學 C 仔咁既水準,點解要納稅人比咁多$佢讀書.

首先是數學要有咁上下，而下是只懂數學，好多時U內真的要用在研究的數比AL還淺，所以有一定水準就可以，而不是要數學有頂尖水平。
過份偏重基本工的人其思路會有限制，這種制度下出來的人有同一傾向，無多樣性；一些有創意、善於打破概定思路的人，加上基礎工夫好的人，互相合作才有好效果。
而基礎也可以在事後補上，這可能更有效率，因為會只選實際有用的學習。

“塵乜稀”在科大考試能過關就已算成功，因為實際的工作能力前不是考試可以全面評審得到，不一定要考試成績頂尖才能有作為。

Amuro

原帖由 avdaemon 於 2009-7-23 23:19 發表


this one OK?

OK，但用在power supply我習慣用pnp。

Amuro

原帖由 poonpoon 於 2009-7-23 23:40 發表


唔盟添....

呢個唔係咁用途故喎,係接唔上穩壓當限流用...

穩壓器的地接在Q1 C腳，輸出接在VCC上。

Amuro

原帖由 FireBlack 於 2009-7-24 01:54 發表

This is incorrect. You cannot connect a constant current source with a constant voltage circuit.

限流 means you can use any current you like, but not exceeding a certain limit. It is not the same as ...

Why can connect them together? The main point is what will happen after connect them together!
In theory, the current source will keep loading have fix current value, no matter how high the resistance of the load is. That mean current need to have infinite output voltage at open circuit or high resistance loading. However, in real world, supply voltage is limited. So current can't increase after current source output reach max allowed voltage. At the time the current source is "killed" because current can't reach defined value. This is what is happen when load current below current limit.
When loading current increase over current limit. The current source active and keep loading current below or equal defined current.

The idea is that:
A current source in series the regulator.
Below current limit, regulator domain and kill the current source. So output voltage follow regulator.
Over current limit value, current source domain and kill the regulator. So output current follow current source.


This is work because the limitation of current source and regulator in real world.

[ 本帖最後由 Amuro 於 2009-7-24 07:40 編輯 ]

avdaemon

can we stop talking "天材" in this topic and talk on another thread?

avdaemon

the problem with bi-polar is VCE become high when in large current. Can we use a FET instead?

avdaemon

today found this linear circuit with voltage-regulate and current-limit function with great explanation.


http://www.feedagg.com/feed/214088/POWER-SUPPLY-CIRCUIT