I have a 555 timer circuit running at around 20Khz/50% duty cycle using a 10v input supply. Everything runs smoothly.
I then added directly to the output a power transistor, it's OWN power supply (30v+) and a coil based load.
At this point, everything is still ok, the load on the second power supply behaves.
Everything seems fine until I start to ramp the voltage up on the LOAD power supply. At that point the 555 seems to get very hot and I have to shut down.
I'm not sure which of the following is happening.
- Some of the LOAD voltage is getting back into the 555 circuit via the power transistors.
- There is some back EMF that is doing the same
- My idea that two seperate power supplies can be used each side of a power transistor is flawed (like a relay).
Anyone have any explainations before I need to upload a circuit diagram?
Thanks.
I then added directly to the output a power transistor, it's OWN power supply (30v+) and a coil based load.
At this point, everything is still ok, the load on the second power supply behaves.
Everything seems fine until I start to ramp the voltage up on the LOAD power supply. At that point the 555 seems to get very hot and I have to shut down.
I'm not sure which of the following is happening.
- Some of the LOAD voltage is getting back into the 555 circuit via the power transistors.
- There is some back EMF that is doing the same
- My idea that two seperate power supplies can be used each side of a power transistor is flawed (like a relay).
Anyone have any explainations before I need to upload a circuit diagram?
Thanks.