問Step up電路

KSC

滿足以下功能的
1)簡單
2)易做(/改)
3)最大電流
4)最大電壓
5)4A電流
的Step up電路

ckshum

回復 1# KSC

建議可從MC34063加external transistor著手。若然你要更高switching frequency或synchronous switch的話，TI和LT都有過百種boost converter可供選擇。

pl8888

回復 1# KSC


輸入電壓 = ?
輸出電壓 = ?
最高負載 = ?
乜野用途?

ahuo

LTC 1871, 不過零件會多d
可以考慮買成品

meguro_

另借問:
有無IC做到~5V -> 12V or 21V + CC 30-100mA?
like this:
http://item.taobao.com/item.htm? ... &id=20111073833
IC面marking: IN5DD

pl8888

回復 5# meguro_


基本上簡單既 dc step up circuit 係類似e類型

http://www.talkingelectronics.co ... %20Circuits.html#10

100mA 應該無問題既, 不過要用大d數值既 cap (~100uF), 唔係高負載 (>> 100mA) 時電壓會 drop 得好犀利, 但要再高d電流就要改 circuit, 因為 555 既 output 會頂唔住.

原理可以參考以下

http://en.wikipedia.org/wiki/Charge_pump

當然也有 switching 類, 不過用於負載較高, 而且較隱定, 但比較複雜, CHING 提到既 LTC1871 就屬於e類

meguro_

回復 6# pl8888


how about constant current for LED?
I need 30-100mA adjustable by fixed resistor
Using LM317 is good or not?

pl8888

回復  pl8888


how about constant current for LED?
I need 30-100mA adjustable by fixed resistor
Usi ...
meguro_ 發表於 2013-12-13 13:41

The current needed by leds depends on the brightness you want to have.  Any value below maximum rating of the leds is good.  Otherwise, leds will be burnt if current exceeds maximum rating too much.  Another factor is that the topology you use to connect the leds, ie. series or parallel.  The design will be different, because leds are diodes which have forward voltage in them.

You may get information from the following website

http://ledcalc.com/

I don't have any idea for lighting leds, I have not studied them yet.

You don't need to use LM317 if your requirements, eg.

constant brightness over operating lifetime, if the leds are driven by batteries,
flicker effect of leds, if they are driven by ac power supply.

are not too rigid.

icefire

回復  pl8888


how about constant current for LED?
I need 30-100mA adjustable by fixed resistor
Usi ...
meguro_ 發表於 2013-12-13 13:41

如果電流唔大，可以用一般boost regulator IC，
LED Cathode駁限流電阻再駁GND，boost IC feedback pin度限流電阻輸出做控制得
V(FB) = I * R，一般boost regulator V(FB)唔係1.2V就0.8V

如果係5V->12V , <80mA，我會用NCP1406，唔貴，又去到1MHz，唔洗用咁大粒電感
一般都好少用倒Linear公司IC，太高級，負擔唔起

meguro_

回復 8# pl8888


    ok, i got it