Another amplifier protection

[output]

I am planning do develop a power amp protection cicruit. I have seen many, but most of them do not fullfill my requirements.

Just wondering if there is already osmthing out there which fits the hill.

My requirements:
- To be used for monoblock pwr amp
- No PCB mounted standby transformer, but external. (allows for torroid which has lower quiescent current (suitable for "always on")
- Power on via exernal trigger signal from pre-amp.
- Input signall detection, which allows for:

• Auto power off (optionally on as well)
• No power on if the input level is above certain treshold ( to prevent
  accidentally hight volumes )- Relay for inrush current limit

- Relay for main transormer power
- DC imbalance detection of main power supply.
- AC off detection
- Up to 2 temperature sensors
- Speaker relay control
- Controlled by microcontroller
- Output DC detection must be able to switch off speaker relay without
microcontroller intervention.
- Circuit galvanically isolated from power amp itself (with hig CMRR)
- Status indicated by multiple LED's
- Temperature: cold, warm, protection on
- DC protection active
- Power on sequence/power on active
- Preferably no switching regulators

Some nice to have:
I2C or UARt to the outside world which allows remote monitoring

• Amp bias measurement. (and maybe digital setting)
• -3dB and clip indication
• Input muting relay ?

Current setup I am thinking off:

DC detecion: wel known discrete 2 transistor circuit
Input detection: galvanic isolation with linear optocoupler
Microcontroller: MSP430G2553 or something similar.
pin count 20 or 28 pin, 200ksps ADC
Temperature sensor(s) probably I2C
Al circuitry on the protection board. "amp side electronics" powered from amp psu. This mainly is an opamp for input signal detect and the DC detection circuit.

Any thoughts on this, or suggestions for something existing. ?

 

[jwilhelm]

The 21'st century protection system has most of what you are looking for already. http://www.diyaudio.com/forums/solid-state/264313-how-build-21st-century-protection-board.html

All your extra requirements could be easily added. In early versions I opted for the external control transformer, but figured out quickly it make for a messy build with little advantage.

 

[output]

Thanks, it does indeed match most of my requirements. Will probbaly this as a starting point.