And... for $15.00 you get a new one and have several more years of enjoyment.
I'm sorry guys, but I just don't see the problem here....
Yes the diodes have some allowance for power surges. They would never get electrical approval if they didn't. But there is a limit to the number of surges they can take. Plugging and unplugging an SMPS brick several times a day will reduce it's lifespan.
I applaud your credentials... but I didn't just make this up while joining DIYA... I've been in electronics both professionally and as a hobbyist since 1965(ish).
Unlike many, I've tried to keep up...
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Yes
https://www.eeweb.com/profile/haley...utorial-principles-functions-of-smps-circuits
"2.1.2 Input filter circuit
The double Pi filter network composed of C1, L1, C2 and C3 is mainly used to suppress the electromagnetic noise and clutter signal of the input power supply to prevent its interference to the power supply, and also to prevent the interference of the high-frequency clutters generated by the power supply itself to the electrical grid. The C5 will start to be charged when the power is turned on, producing a large instantaneous current, which is called surge current, but with an RT1 (thermistor) it can be effectively prevented. Because the instantaneous energy is all consumed on the RT1, after a certain time the resistance of RT1 will decrease as the temperature rises (RT1 is a negative temperature coefficient device) and the energy consumed by RT1 will be very small at this time, to make sure the following circuits work normally."
But you are fogetting one small thing ...
In a laptop or similar battery powered device, the brick only has to deal with it's own inrush of current. The battery power the device, the brick charges the battery.
In devices like mini-amps, modems, routers, etc. where there is no battery to buffer the startup currents the supply has to deal with it's own plus that of the device itself... That's where the shortened lifetime comes from.
I don't get what you are driving at, you said
what do you mean by most, and why wouldn't they have a NTC like in the article I've shown
If the device is always on, there is increased risk of SMPS failure due to random voltage spikes at the input. They are generated by ligtning strikes and home appliances induction motors switching on/off on the same supply circuit. If the device is turned off (disconnected from mains) when not in use, there is increased risk of failure due to turn-on current surge. A well designed SMPS does have protection for both conditions. A cheap one may lack one or both protection. The surge protection is the first one to be removed as cost saving measure. This does makes sense because most people are accustomed to leave the device always connected to the mains supply, but a mains rated power switch does cost money. It is cheaper for the manufacturer to implement a "pseudo off" feature where the power supply is always energized. It also helps masking the slow boot/initialization time of cheap and wimpy microcontrollers. Finally, uneffective turn-on surge protection is a common issue when the manufacturer has been forced to use a SMPS filter capacitor with excessive capacity to compensate for the faster degradation rate of cheaper parts. Fitting a 82uF capacitor instead of the 47uF design value will increase the chance that the residual capacity at the end of the warranty period will still be enough to operate the device. The diode at the input will short after maybe 100 surges, but there is a low chance that the device will be routinely turned off completely - if 100 surges will last for the warranty period, the manufacturer problem is solved.
If a products is supplied with a external power brick that does look suspicious, my suggestion is to get a good quality medical grade SMPS with same or better specs than the original one. This is expecially true if the device (or a failure) is expensive. Bad quality power supply will fail no matter what you do, and some failure modes, such as partial shorting of a overheated feedback winding on the SMPS transformer, will produce a high voltage, high energy spike on the output. It is not uncommon to have expensive devices, 1000+ euro list price, killed by a 10 euro charger. That's madness. Bad SMPS also have obnoxious EMI issues that will interfere with any nearby low level analog signal.
If a products is supplied with a external power brick that does look suspicious, my suggestion is to get a good quality medical grade SMPS with same or better specs than the original one. This is expecially true if the device (or a failure) is expensive. Bad quality power supply will fail no matter what you do, and some failure modes, such as partial shorting of a overheated feedback winding on the SMPS transformer, will produce a high voltage, high energy spike on the output. It is not uncommon to have expensive devices, 1000+ euro list price, killed by a 10 euro charger. That's madness. Bad SMPS also have obnoxious EMI issues that will interfere with any nearby low level analog signal.
I still have an older Dell laptop - 2004 vintage/XP -Lattitude D600.
The battery is original, holds a charge for maybe an hour or so with light use.
Has the original "power brick" as well.
This must have been "plugged in" and "unplugged" several thousand times over the 15 years that I used it.
And it still works!
This spitting contest over power supplies and their potential issues is funny, actually.
You either build something the right way, or you don't.
The battery is original, holds a charge for maybe an hour or so with light use.
Has the original "power brick" as well.
This must have been "plugged in" and "unplugged" several thousand times over the 15 years that I used it.
And it still works!
This spitting contest over power supplies and their potential issues is funny, actually.
You either build something the right way, or you don't.
Don't quite know why you turned your nose up at the blowtorch thread, I think you'd fit right in there
To better understand the issue, I should add that there is a significant price difference between a well designed SMPS built with good parts, and a "mainstream" one. A price sensitive or low-end product cannot have a good and long lasting SMPS power supply on this day and age.
As example, I recently sourced 500 switched mode power supply boards with enclosoure: screw type terminals, single output 120W 24V, a pretty common part. The one that came from a local manufacturer of industrial grade boards had Epcos main filter capacitor, detailed spec sheet and full EMC certification from Nemko. Good product, not the absolute best but it had all the protections and good warranty terms. Price: in the ballpark of 22 euro. The standard-quality one from a obscure OEM China manufacturer: 11 euro. It was not bad at first glance but minimal sourge protection and EMI filter. No real manufacturer warranty. To my experience, long term reliability and consistency of this kind of boards is unpredictable, some works for years and some don't; to be avoided if quality is important. I haven't even looked at the far-east no-name boards, they cost even less but then even the basic electrical safety rules aren't to be taken for granted anymore.
As example, I recently sourced 500 switched mode power supply boards with enclosoure: screw type terminals, single output 120W 24V, a pretty common part. The one that came from a local manufacturer of industrial grade boards had Epcos main filter capacitor, detailed spec sheet and full EMC certification from Nemko. Good product, not the absolute best but it had all the protections and good warranty terms. Price: in the ballpark of 22 euro. The standard-quality one from a obscure OEM China manufacturer: 11 euro. It was not bad at first glance but minimal sourge protection and EMI filter. No real manufacturer warranty. To my experience, long term reliability and consistency of this kind of boards is unpredictable, some works for years and some don't; to be avoided if quality is important. I haven't even looked at the far-east no-name boards, they cost even less but then even the basic electrical safety rules aren't to be taken for granted anymore.
Don't quite know why you turned your nose up at the blowtorch thread, I think you'd fit right in there
That thread is worthless, endless babble with nothing that interests me.
Ummm ... Je tape en anglais, n'est-ce pas?
I give up...
The OP asked if it was safe to leave a mni-amp on all the time.
The answer is "Yes".
Yes it will be fine.
Hook it up. Leave it plugged in... and just use it.
As I've explained far too often without anyone seeming to understand, that start up surge where it's feeding both it's internal capacitors and those of the amplifier can shorten it's lifetime somewhat if you keep unplugging it and plugging it back in.
I don't know how to say this any more clearly, so please stop asking.
To be honest, it's not possible to tell just by looking at the outside of a box, it will probably be fine, you pays your money and you takes your choice.
Well, if there's a NTC with a cold resistance of, say, 10 ohms in series with the input, the maximum surge will be 230V/10*sqrt 2 = 32 A, even if the device's output is shorted, won't it? The designer simply has to chose the NTC and the rectifier diodes so that they can cope with that, plus some safety margin.
Best regards!