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x0x:powersupply [2010/07/02 19:58]
ihatetoregister
x0x:powersupply [2011/08/25 22:26]
mickeydelp
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 {{template>​.templates:​schema|section=Power Supply|inputs=9 V AC, 50/60 Hz|outputs=5 V and 6 V, and the 12 V and 5.333 V}} {{template>​.templates:​schema|section=Power Supply|inputs=9 V AC, 50/60 Hz|outputs=5 V and 6 V, and the 12 V and 5.333 V}}
  
-The power supply is relatively simple to understand. The power comes in at 9 V AC, 50/60 Hz, and goes to the rectifier. From here it is split into 2 section, the 5 V and 6 V, and the 12 V and 5.333 V. At each section there are smoothing capacitors and [[bypasscapacitors|bypass capacitors]]. ​+The power supply is relatively simple to understand. The power comes in at 9 V AC, 50/60 Hz, and goes to the rectifier. From here it is split into two sections, the 5 V and 6 V, and the 12 V and 5.333 V. At each section there are smoothing capacitors and [[bypasscapacitors|bypass capacitors]]. ​
  
 See the [[jumpers]] page for a list of which jumpers go where. ​ See the [[jumpers]] page for a list of which jumpers go where. ​
- 
 ==== Block Diagram ==== ==== Block Diagram ====
 +{{:​x0x:​power-supply-overview-3.png|}}
  
 <draw name=psblock namespace=x0x>​ <draw name=psblock namespace=x0x>​
- +
 ==== The Rectifier and Smoother ==== ==== The Rectifier and Smoother ====
  
 {{http://​www.kpsec.freeuk.com/​animated/​brect.gif }} {{http://​www.kpsec.freeuk.com/​animated/​brect.gif }}
  
-The power input into the x0xb0x is 9 alternating current. This needs to be converted to direct currentbefore getting regulated to its proper voltage. This is done by the four 1N4001 diodes with what is called a bridge rectifier. You can see how a bridge rectifier works on the left hand side. While the bridge rectifier has in fact made sure our current is DC, it is in a state called "Full Wave Varying ​DC". We don't have a smooth line of direct current, rather, we have a series of camel humps, where the voltage goes from 0 V, to +9 V back to 0 V+The power input into the x0xb0x is 9 volt alternating current ​from an AC/AC adaptor. This needs to be converted to direct current before getting regulated to the different voltages. The 9 volt input is a root mean square value (rms) and is the value that is shown on a multimeter with the ac measuring setting. This means that the peak to peak voltage is 9 volts times the square root of two resulting in a peak to peak value of about 12.7 volt. Due to differences in ac adaptors the rms voltage could be over 10 volts resulting in a peak to peak voltage of about 14-15 volts.  
 + 
 +The ac/dc conversion ​is done by the four 1N4001 diodes with what is called a bridge rectifier. You can see how a bridge rectifier works on the left hand side. While the bridge rectifier has in fact made sure our current is DC, it is in a state called "full wave varying ​DC". We don't have a smooth line of direct current, rather, we have a series of camel humps, where the voltage goes from zero, to the peak voltage ​back to zero.  
 + 
 +The two 2.2 mF capacitors c3 and c5 perform a smoothing operation. When the voltage starts on its downward drop from the peak voltage to zero, the capacitors discharge, and the voltage drop is minimized. The DC waveform looks a lot smoother, and more like gentle waves rather than camel humps, and the varying voltage is quite minimal compared to the rectified output
  
-C3 and C5, the 2.2 mF capacitors perform a smoothing operation. When the voltage starts on its downward drop from +9 V to 0 V, the capacitors discharge, and the voltage drop is minimized. The DC waveform looks a lot smoother, and more like gentle waves rather than camel humps, and the varying voltage is quite minimal compared to the rectified output. ​ 
  
 ==== Regulated Voltage ==== ==== Regulated Voltage ====
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 The power also goes through another RC network (1K Ohm and 100uf), before sent to the voltage reference circuit. This is taken from the LM336Z datasheet. TM6 allows to adjust the "​breakdown voltage"​ of the voltage reference. D45-47 are used to "​obtain a lower temperature coefficient"​. This is then sent to an op-amp set up to be a [[voltagefollower|voltage follower]], to eliminate any loading effects. (This makes sure that 5.333 V is available throughout the entire circuit?​). ​ The power also goes through another RC network (1K Ohm and 100uf), before sent to the voltage reference circuit. This is taken from the LM336Z datasheet. TM6 allows to adjust the "​breakdown voltage"​ of the voltage reference. D45-47 are used to "​obtain a lower temperature coefficient"​. This is then sent to an op-amp set up to be a [[voltagefollower|voltage follower]], to eliminate any loading effects. (This makes sure that 5.333 V is available throughout the entire circuit?​). ​
  
-The 5.333 V is generated first with the voltage reference and buffer because it is the ac ground (virtual ground) for the whole circuit. It needs to be stable so is generated with this reference from ground rather than from a potentially unstable positive supply. It is buffered so it can supply current under load. As for why they chose 5.333 V maybe it was related to the VCO circuit. Ideally you would pick a bias voltage that is half the suppy rail, maybe they chose 5.333 as compromise related the generation of the saw wave+The 5.333 V is generated first with the voltage reference and buffer because it is the ac ground (virtual ground) for the whole circuit. It needs to be stable so is generated with this reference from ground rather than from a potentially unstable positive supply. It is buffered so it can supply current under load. The reason ​they chose 5.333 V is because ​it is evenly divisible by 0.08333 (i.e. 1/12 volt or one note in 1V/octave CV system).
   ​   ​
 The 5.333 V is sent to a [[noninvertingamplifier|non-inverting amplifier]],​ with the 2.2 k and 1.8 k resistors. This provides a 2.222 V gain to the 5.333 V, equaling a voltage of 11.851 V, giving us the 12 V power supply. Capacitors C60 and C61 seem to be [[bypasscapacitors|bypass capacitors]]. ​ The 5.333 V is sent to a [[noninvertingamplifier|non-inverting amplifier]],​ with the 2.2 k and 1.8 k resistors. This provides a 2.222 V gain to the 5.333 V, equaling a voltage of 11.851 V, giving us the 12 V power supply. Capacitors C60 and C61 seem to be [[bypasscapacitors|bypass capacitors]]. ​
/home/ladyada/public_html/wiki/data/pages/x0x/powersupply.txt · Last modified: 2016/01/28 18:05 (external edit)