PWM chip abolute max Vcc

where to get parts for building your own transmitter.

PWM chip abolute max Vcc

Postby n4lta » Sun May 08, 2011 10:45 am

I am in the process of building a PWM modulator. My AC line is a bit high and my unregulated voltage from my power supply is 21 volts rather than 18 volts. Before using the supply I looked at the PWM IC Data Sheet and see that the Vcc on the chip is 15 volts abolute maximum rating.

The 160 ohm resistor will not drop the voltage to with the 15 volt max rating at 10-20 ma operating current.

Am I missing something? Do I need to use a 7815 or a 7818 to be safe?
n4lta
Member
 
Posts: 20
Joined: Thu Aug 05, 2010 8:53 pm

Re: PWM chip abolute max Vcc

Postby Gilly » Sun May 08, 2011 6:23 pm

Hi Hugh

I would change the 160 ohm resistor to appox 330 ohms just to keep the current to about 20ma or so....

I know someone who uses 50Volts with a 1.5Kohm resistor to regulate the current...


Wayne

VK3ALK
Gilly
Class E Enthusiast
 
Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Re: PWM chip abolute max Vcc

Postby n4lta » Sun May 08, 2011 6:41 pm

Thanks,

I will do that. I didn't want to burn out the chip while testing my new board layout.

Pat
n4lta
Member
 
Posts: 20
Joined: Thu Aug 05, 2010 8:53 pm

Re: PWM chip abolute max Vcc

Postby Gilly » Wed Jul 06, 2011 4:24 am

Hi Pat


How is the PWM going ?



Wayne
Gilly
Class E Enthusiast
 
Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Re: PWM chip abolute max Vcc

Postby n4lta » Wed Jul 06, 2011 9:35 pm

Pretty much done. I just finished the power supply and have tested the PWM generators, anti al filters ect. I built the audio section in a nice Hammond enclosure and the power supply in a Hammond rack cabinet. All the fets and power supply parts and metering are mounted and wired. I plan to wind the filter toriods and complete the filter in the next few days. I will post some photos when I am done. I used a real heavy duty toroidal power transformer rated at 120 volts and 9 amps with a 50 amp bridge and 12- 2200uF 160 volts caps.

I have a resistor bank rated at 5 ohms at 500 watts to test the PWM supply.


I ordered some FETs from KF1Z today to start the transmitter. Also ordered a couple of 2000pf variables from Fair Radio so It is slowly coming along.
n4lta
Member
 
Posts: 20
Joined: Thu Aug 05, 2010 8:53 pm


Return to Parts and Sources

Who is online

Users browsing this forum: No registered users and 1 guest

cron