wonder if the fets are happy disconnecting an inductive DC load. ever tried disconnecting a solar panel plug in active duty ?
You could use independent power supply, but D7/D8 must be connected to main power supply. I designed this circuit for my AIO amp, for independent PSU I would use a bit different approach.
For 80-90V PSU use 200-250V mosfets (Rdson<10mR) and probably heatsink for them.
I have a doubt about it that the mosfets are rated at 120Amps now consider the pins of the mosfet upto what current ratings will those pins work without any issues? I mean the die of the mosfet might be able to deliver instantaneous or pulse currents of 120A but when it comes to sinusoidal waves what will be its capacity even though Vds is lower like about 3V or 4V max so when we check the SOA the device is capable of delivering the current but will the pins be able to deliver the current?
are you able to drive amplifier like +/-85V 500W into 4 ohms endup approx worse case current about 25Amp at an instance so will the pins be able to carry soo much of current?
are you able to drive amplifier like +/-85V 500W into 4 ohms endup approx worse case current about 25Amp at an instance so will the pins be able to carry soo much of current?
you can use infineon 150V mosfets in different packages (I prefer TO262-3)
TO220-3 IPP051N15N5
TO262-3 IPI051N15N5
TO263-7 IPB044N15N5
TO263-3 IPB048N15N5
I've always had the same concern about the current carrying capabilities of the TO-220 versions. This is why I chose to go with D2PAC 7 pin versions instead. I prefer the 5 parallel pins. IPB025N10N3 G Infineon Technologies | Mouser Canada
I too have had concerns about the pins carrying large current.
I am going to use four IRF100B201 (TO220) per channel, hoping that this will increase the current capability of the pins.🙄
I am going to use four IRF100B201 (TO220) per channel, hoping that this will increase the current capability of the pins.🙄
1. TO220 devices rated for 100A are tested to 100A (I worked at a power mosfet factory for 10 years). Remember, in an audio SSR application, you will not be conducting the fault current for very long - a few milli-seconds worst case
2. Mosfets - specifically Trench mosfets - can switch very large inductive loads. If you look at the spec sheet you will see an energy rating - make sure your worse case inductive load switch is < than this (E = 0.5LI^2)
3. Its important to switch the mosfets fast to limit the dissipation and remain within the energy rating
4. Mosfets can switch at their full rated energy capacity ad infinitum - e.g. 100 000 cycles and more. Relays cannot do this - I started a thread a few years ago after blowing up one of my B&W 703 speakers - the relay (16A 260 VAC) contacts welded closed.
4. The on resistance of a SSR for audio applications will typically be <20 mOhms and will be swamped by cable and crossover wiring resistance - i.e. it will have no real effect on damping.
2. Mosfets - specifically Trench mosfets - can switch very large inductive loads. If you look at the spec sheet you will see an energy rating - make sure your worse case inductive load switch is < than this (E = 0.5LI^2)
3. Its important to switch the mosfets fast to limit the dissipation and remain within the energy rating
4. Mosfets can switch at their full rated energy capacity ad infinitum - e.g. 100 000 cycles and more. Relays cannot do this - I started a thread a few years ago after blowing up one of my B&W 703 speakers - the relay (16A 260 VAC) contacts welded closed.
4. The on resistance of a SSR for audio applications will typically be <20 mOhms and will be swamped by cable and crossover wiring resistance - i.e. it will have no real effect on damping.
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Hi Bonsai,
thanks for the additional information.
What are your thoughts on disconnecting the power supplies to the amp board instead of disconnecting the output i.e. breaking the DC supply?
Assuming there is no large caps on the amp board.
Regards
Harry
thanks for the additional information.
What are your thoughts on disconnecting the power supplies to the amp board instead of disconnecting the output i.e. breaking the DC supply?
Assuming there is no large caps on the amp board.
Regards
Harry
I have not tried that but it should work well. The advantage with your proposal is that your mosfets need only be rated for the supply rail and not the full +and - rail as is the case when switching the speaker.
The important thing is to always switch the mosfets quickly.
The important thing is to always switch the mosfets quickly.
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Do we actually require mosfets with full + and - rail voltage rating for speaker relays? On the amplifier side they will only see between zero volts and rail voltage. How much voltage can we expect to be present on the speaker side?
The reactive properties of the load can kick back with a full rail of potential that could add to the actual power supply rail, which is why it is oft cited to rate for the full swing.
How often in a real situation does this occur? I can't say. I'd bet with component ratings being conservative and needing the 'perfect storm' of conditions one might find over-rating by 50% plenty adequate.
How often in a real situation does this occur? I can't say. I'd bet with component ratings being conservative and needing the 'perfect storm' of conditions one might find over-rating by 50% plenty adequate.
Thanks Jason. Likely when things go south in an amp, particularly full blown oscillation it would be pretty close to the perfect storm.
Ideally one would turn on the Mosfets after the power supply has settled.
Wish everyone a good Christmas vacation 🎅
No. 8 Ohm nominal is usually 6 Ohms pure resistance. On the randomly picked woofer below, the spec is 5.4 Ohms. 20 Amps, not 80 Amps.
Attachments
The mosfets need to be rated for the worst case reactive load. I agree you may not need the full + and - supply rating, but the full rating is the safest and easiest belt and braces approach.
