Softstart unit for amplifier
![1343](https://cdn.xingosoftware.com/elektor/images/fetch/dpr_1,w_200/https%3A%2F%2Fwww.elektormagazine.com%2Fassets%2Fupload%2Fimg%2Fpublic%2Foriginal%2Famplifier-top.jpg)
This project includes a softstart circuit for powering up an audio-amplifier and some peripherie.
Some month ago I planned to build an amplifier. The amplifier should be built as small as possible. So I decided to use a 300W switched power supply to drive the amplifier. Because of the inrush current of the supply, a softstart unit was needed.
My research at the internet revealed, that there is no unit which would fulfill my needs.
So I decided to develop it by myself.
The concept of this unit is based on the ATTINY24 microcontroller which programmed statemachine will start first the main power supply and after that the amplifiers. This sequence is necessary, because the big capacitor of the amplifier (>50mF) will cause the supply in short circuit mode.
For a comfortable use, there is a remote control ability achieved by the µC. Via IR interface a servo motor of the volume pot could be controlled. Of course, I designed an automatically starting trigger of the amplifier, if there is any audio signal on the line inputs. Also an additional supply for the preamp is included on the PCB.
So thank you for reading this and be sure that constructive criticism is always welcome...
My research at the internet revealed, that there is no unit which would fulfill my needs.
So I decided to develop it by myself.
The concept of this unit is based on the ATTINY24 microcontroller which programmed statemachine will start first the main power supply and after that the amplifiers. This sequence is necessary, because the big capacitor of the amplifier (>50mF) will cause the supply in short circuit mode.
For a comfortable use, there is a remote control ability achieved by the µC. Via IR interface a servo motor of the volume pot could be controlled. Of course, I designed an automatically starting trigger of the amplifier, if there is any audio signal on the line inputs. Also an additional supply for the preamp is included on the PCB.
So thank you for reading this and be sure that constructive criticism is always welcome...
Updates from the author
Hans Gans 5 years ago
The attached sketch shows how the Softstart Unit must be connected correctly to the controlling audio source. It should be noted that the different ground lines are not connected due to the galvanic isolation. Correctly, the shielding should only be applied at one end.
If there is no need for the auto "ON / OFF" function, it can be switched off. You will find this point after the last IR Teach command using the power button, which switches between active or inactive "Auto ON / OFF".
Hans Gans 5 years ago
So I upload the actually version here.
ElektorLabs 5 years ago
Hans Gans 5 years ago
Die Klemme K11_1 sollte von L* in N* umbenannt werden. Die Klemme K11 ist der Schaltkontakt für das SMPS bzw. den Trafo.