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About Chinese LLC SMPS
About Chinese LLC SMPS
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Old 2nd October 2017, 04:44 AM   #1
umut1001 is offline umut1001  Europe
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Default About Chinese LLC SMPS

Hi.I bought a LLC SMPS from China.It is here HIFI Audio Soft Switching Power Supply Board For Power Amplifier +-36V +-48V 500W | eBay

I thought the price is good but i am a bit disappointed.It did not come with Rubycon caps at input and also output.It also seems it is made a bit low quality.Poor soldering I have a limited information about SMPSs and also LLC.As i heard LLC is very sensitive about L and C values and resonant frequency. As a capacitor seller i have much more quality than the caps at input and output caps( 120uF 450v and 2200uf 50v) Especially 2200uf 50v seems very low quality. Can i change them without problem?Is there any need of adjustmens ? (altough it seems there is no adjustment trimmer or sth like that) I am using it with iraudamp7s in bridged mode for my 6ohm subwoofer.(SB34NRX75-6) SMPS Voltage is +-48v Plays music and cinema good.Good dynamics.But i want to improve Thank you in advance.
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Last edited by umut1001; 2nd October 2017 at 04:53 AM.
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Old 2nd October 2017, 08:53 AM   #2
JonSnell Electronic is online now JonSnell Electronic  United Kingdom
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Changing the electrolytics will not make them work any better. Do not replace the tuning capacitors!
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Old 2nd October 2017, 11:46 AM   #3
ejaouen is offline ejaouen  France
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could you tell us based on which controller IC and or other IC chips are these "softswitch LLC 500w chinese smps" from ebay link ?
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Old 3rd October 2017, 04:03 AM   #4
umut1001 is offline umut1001  Europe
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Sorry the chip module is sealed with black epoxy and no info
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Old 4th October 2017, 02:45 AM   #5
umut1001 is offline umut1001  Europe
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Quote:
Originally Posted by JonSnell Electronic View Post
Changing the electrolytics will not make them work any better. Do not replace the tuning capacitors!
No i wont change tuning caps of course.I can easily hear differences when i change caps on regular power supplies and i just wondered if an improvement may happens on Smps
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Old 4th October 2017, 02:55 AM   #6
nigelwright7557 is offline nigelwright7557  United Kingdom
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They have to cut corners somewhere to get the price down.

LLC SMPS are very good. As the transformer primary sees a sine wave and not a square wave there is much less radiation from the SMPS.

The resonant frequency is very important. If you move it by changing caps then you can shift the frequency into the capacitive high current mode and possibly destroy it.
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Old 6th October 2017, 07:47 PM   #7
AMason is offline AMason
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Background: I designed the LLC in the Benchmark AHB2 amp.

Be careful. LLC power supply can be done very well, but can also be botched pretty easily. I wouldn't hazard changing any parts. The designer may be relying on a specific capacitor value or ESR for stability.

It's risky business modifying power supplies as there are often multiple dependencies.

I get scared thinking of how many DIYers are using SMPS' in the first place (400-600 Vdc doesn't tickle!), and especially SMPS that are of either unknown origin or don't have any safety testing.

Does anyone have links to DIY SMPS that solve some of these issues?
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Old 6th October 2017, 08:34 PM   #8
blueskull is offline blueskull  China
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You can replace the output caps. LLC isn't very sensitive to cap ESR so replacing with lower ESR cap will not reduce its stability by too much. I don't think replacing input cap will help much besides potentially increasing its lifetime.

As for frequency, don't bother. It has a feedback control loop that automatically tunes and detunes it for output voltage regulation. An LLC almost never operates at resonant frequency anyway, otherwise it won't be able to regulate output voltage when input voltage changes.

Regarding to shock hazard, this one seems to be well designed -- clearances and creepages are decent, maybe not the best. Transformer has physically isolated bobbin islands for pri and sec windings, which is good. If the optocoupler and Y cap are certified, this should be good enough.

Primary side EMI filter choke seems to be not that well implemented in terms of insulation, there's no physical separation between L and N windings, this could be a fire hazard if magnet wire insulation is compromised due to being rubbed against toroidal core. This is not a big deal if the core has reliable insulated coating, but I can't say that for sure without having the SMPS physically in my hand.

Reference: I hold an MSEE in electric power system engineering, and a PhD candidacy in power electronics.
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Old 8th October 2017, 08:28 PM   #9
Eva is offline Eva  Spain
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Quote:
Originally Posted by nigelwright7557 View Post
They have to cut corners somewhere to get the price down.

LLC SMPS are very good. As the transformer primary sees a sine wave and not a square wave there is much less radiation from the SMPS.

The resonant frequency is very important. If you move it by changing caps then you can shift the frequency into the capacitive high current mode and possibly destroy it.
This is not an accurate statement. The radiated EMI from the transformer (magnetic field) comes from voltage drop across leakage inductance. In conventional push-pull, forward or flyback SMPS leakage inductance must be as low as possible. In LLC SMPS leakage inductance is higher and is used as a ballast, there is the option to include leakage inductance in the transformer or to use an external inductor. The 1st option is adequate for small power adapters, but radiated EMI is higher. The 2nd option is adequate for audio SMPS.
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Old 4th January 2019, 08:08 AM   #10
hansueli is offline hansueli  Switzerland
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Hello umut1001
Can you tell me if you are happy with the power supply. More than one year you are using it.


Is the used regulator an irs2795x chip? Its a LLC driver and used in the IRAUDPS3 supply.


Thanks
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