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yigiter
Joined: 22 Nov 2004
Posts: 16
Location: Istanbul,Turkey
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 06 Dec 2004 16:50 12->24V boost converter |
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hello,
i use a boost converter to convert 12VDC to 24VDC. the reference design is as below:
http://focus.ti.com/lit/ml/slvr061/slvr061.pdf
i want to ask about it's output current. it says that the output current is 3amps average and 8amps for 2 seconds. what are the factors that affect the output current. how can i improve the output current about 4amps continuous?
thanks for your concern.
regards,
-Erkan
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nicleo
Joined: 06 Sep 2004
Posts: 717
Helped: 60
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| 06 Dec 2004 18:52 12->24V boost converter |
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| You should make sure that the power ratings of L1, Q2, and D1 are 'enough' if 4amps is drawn by load continuously.
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IanP
Joined: 05 Oct 2004
Posts: 6346
Helped: 1505
Location: West Coast
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| 07 Dec 2004 1:59 Re: 12->24V boost converter |
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| Your main problem, if using IRL1104S, will be heat. Its max current is around 100A and its di/dt>200A/us, so these parameters are OK. But because it is in D2Pak it will not be easy to despatch all generated heat and this limits your average current..
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yigiter
Joined: 22 Nov 2004
Posts: 16
Location: Istanbul,Turkey
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| 07 Dec 2004 10:05 Re: 12->24V boost converter |
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| IanP wrote: |
| Your main problem, if using IRL1104S, will be heat. Its max current is around 100A and its di/dt>200A/us, so these parameters are OK. But because it is in D2Pak it will not be easy to despatch all generated heat and this limits your average current.. |
| eblc1388 wrote: |
| You should make sure that the power ratings of L1, Q2, and D1 are 'enough' if 4amps is drawn by load continuously... |
i am using IRF3205 instead of IRL1104. IRF3205 is in TO220 package and i am using L1 which is for 16amps. so there is not a problem about heat or about inductor. but i am not sure about the diode. it may be for 3amps. i should change it.
does the output current depend on only these parameters?
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olemp
Joined: 18 Jul 2004
Posts: 96
Helped: 2
Location: turkiye
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| 07 Dec 2004 11:27 12->24V boost converter |
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| yes all current pass through mosfet, inductance, diode(you can use them parallel) and of course load...and don't forget: your 12v supply should capaple of carrying that current .bu in that schema i could't understand something. in that ic, sesse the current a resistance is connected between source of the mosfet and gnd..and upper side of that resistance (also source of the mosfet) connected current sense input via low pass filter. what is the idea in that schema about usage of the current sense pin???is there any idea??
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nicleo
Joined: 06 Sep 2004
Posts: 717
Helped: 60
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| 07 Dec 2004 11:51 Re: 12->24V boost converter |
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| yigiter wrote: |
| Does the output current depend on only these parameters? |
The output current depends on your load. For example, if the output is 12V and the load is 3ohm, then the current drawn from the converter is 4A. So, you need to make sure L1, D1, and Q2 are sized for that rating.
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platonas
Joined: 14 Aug 2004
Posts: 165
Helped: 5
Location: Universal Citizen
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| 07 Dec 2004 13:06 Re: 12->24V boost converter |
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Certainly the main components that describe the output current capabilities for this circuit are L1, D1, and Q2.
Thicker wire for L1 windings.
Lower drop on D1 and most important higher current rating. Allways use a fast diode.
Q2 must be fast for the frequencies used, must have low Rds on and able to handle high current and dissipate head. (The last depends on packaging and headsink used)
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