UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

kalee20 · 26th Jun 2018, 1:00 pm

Boost converters can do funny things, and as brightsparkey says, can be 'interesting' to stabilise.

Although increasing the duty cycle causes the steady state output voltage to increase, when you do increase the duty cycle, the output voltage actually DECREASES briefly before it recovers and increases. This can make the feedback loop oscillate very readily. It has to be quite slow acting. Luckily, this only matters if the load (or input voltage) change rapidly. If they don't - and I'm talking tens of milliseconds - then it is not a problem.

If you are aiming to drive a battery-portable radio with 90V HT, be prepared to be very demoralised by the squeals and whistles breaking through. It really will need careful design plus lots of filtering, and then you'll probably have to put it in a screened box to stop radiated interference getting out. But you'll have a lot of fun.

26th Jun 2018, 1:00 pm	#30
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,081	Re: Switched Mode Power Supplies Boost converters can do funny things, and as brightsparkey says, can be 'interesting' to stabilise. Although increasing the duty cycle causes the steady state output voltage to increase, when you do increase the duty cycle, the output voltage actually DECREASES briefly before it recovers and increases. This can make the feedback loop oscillate very readily. It has to be quite slow acting. Luckily, this only matters if the load (or input voltage) change rapidly. If they don't - and I'm talking tens of milliseconds - then it is not a problem. If you are aiming to drive a battery-portable radio with 90V HT, be prepared to be very demoralised by the squeals and whistles breaking through. It really will need careful design plus lots of filtering, and then you'll probably have to put it in a screened box to stop radiated interference getting out. But you'll have a lot of fun.