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Everything posted by Newguy

  1. Hi Ante Thanks for your reply. Do u mean that I can vary the R6 from 15K to 75K. But how about the current? How about the current limiter? ??? Thanks
  2. Hi Ante Also, I would like to post my construction procedure of the circuit. But I don't know how to add photo to my message. Could u tell me how to make it? Thanks
  3. Hi Ante Good. I am going to build a power supply without transformer. But I still have some problems 1. Like page 53, TL431B is used to control the PWM. Its voltage is 2.5V. What is the variable range of R5 and R6? How to calculate that? Also, how can I determine the output range of a circuit like that? 2. Also can u give me some ideas about adding the current limiter? I have little experience about that. What kind of current limiter? How to calculate? Thanks very much
  4. Hi Ante I mean P29-P54 of the attached pdf file. This file provide some circuit, but I don't know weather they can be adapted to be variable output. I think it is not necessary to variable from 0V to 30V. Instead, it can vary from 3V-25V. Since I know it is hard for a SMPS to provide 0V. And u can read page 53. This circuit uses the R5, R6 and TL431B to provide reference. Can I just simply change these three items to provide variable output? Also can it be current limited. Thanks very much
  5. Hello every body I have studied the 0-30 VDC STABILIZED POWER SUPPLY WITH CURRENT CONTROL CIRCUIT and discussed it with audioguru. I think that is a very good circuit. However, if it can be realized by SMPS (switch mode power supply), it may be much lighter and the project may be challenging. As a result, I search some circuits(P29-P54). But I don't know how to make these circuits to be variable voltage output with current limitation. If u have any idea, please tell me, I am going to build this very soon. Thanks!!!!!!!! SMPS_POWER.pdf
  6. Hi Audioguru Thanks your suggestion. But since the overcharging part is not my responsiable, I have no need to worry about it. And The out put must be controled manually so I can't use IC. So, in order to let user to choice between constant current charging and constant voltage charging, I have to built one voltage regulator and one current regulator in the same charger. right? If I really built the voltage regulator, the output voltage will keep as my setting no matter the situation of the battery. And the current regulator is the same right ??? If not could you teach me how to find the rang of load for the constant current output and the constant voltage output. Additionally, back to our circuit. Do you mean that both your lab supply and regulator in market are trying to keep the set current first ? But by my limitted knowledge, I think your lab supply and the regulator can only limit the current not over a constant. Let say, if the load keep increasing and reach 80 ohm, (It just an asumption, is ture that in the actual world charging will only decrease the load of the battery ???) and the current drop to less than 1A(0.5A), then the circuit will still out put 10V and 0.5A. The circuit can not make sure that the output current is kept in 1A, if the load increase. Thanks very much
  7. Hi audioguru Thanks very much for telling me the limitation of the circuit. Actually, I am a student, I am finding a circuit which can provide a constant current and constant voltage for charging. And both the current and the voltage must be adjustable for different kinds of batteries. And I need not consider about the problem of over charging. Secondly, I found that some regulators like L200(ST) and LM117 can be built to be a Voltage and Current Regulator. In the data sheet the voltage out put and current out put are controled in the same circuit with two variable resistor. I want to know that in these kind of regulator circuit the voltage and current are controled individulally or related. However, I still can't find a suitable circuit after reading many web pages. Could you give me some hints? Thanks a lot L200_ADJUSTABLE_VOLTAGE_AND_CURRENT_REGULATOR.pdf
  8. Hi audioguru Thanks for telling me the source. And I would like to ask one think more that can this circuit be used for charger. I think that the current limitter can only limit the current not over one level, but it can not make sure the current is keeped in that level. For example, if I am charging a Li-Mh battery the resistance of the battery may change. But I have to keep the charging current in a constant level. Can I use this circuit for that kind of charging purpose. Thanks!!! ???
  9. I wish I could increase the max. current from 3 AMPs to 5 AMPs e.g. by changing the transformer, diodes and Transisters and PCB tracks width and heat sink etc.
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