Here's the schematic: http://www.raleighaudio.com/ccs.htm
I'm somewhat confused on how to compute the output voltage since R1 and R2 is limited to combinations that produces 2.5V across R2. Is there a formula?
also what kind of triode can I use? can I use 6as7 (the only non-matched tube that I got and I have 2 of them)?
thank you.
I'm somewhat confused on how to compute the output voltage since R1 and R2 is limited to combinations that produces 2.5V across R2. Is there a formula?
also what kind of triode can I use? can I use 6as7 (the only non-matched tube that I got and I have 2 of them)?
thank you.
Re: Re: Re: need help understanding voltage regulator schematic (using CCS) from Rale
Ok, suppose the IC does not draw a current through the gate;
now let's the current across resistors will be 1 miliamper, so R2 will be 2.5 KOhm. So, to regulate 150V you'll need (150-2.5)=125.5 KOhm, for 250V you will need 225.5 KOhm, and so on...
But I still don't understand why do you want to vaste a tube if you can use one zener diode, or a zener with a transistor if you don't have powerful enough zener?
Suppose, the tube's filament opens up, then unregulated high voltage goes to where lower regulated should go...
Also, it is high and unregulated while the tube is cold...
jarthel said:
Ok, suppose the IC does not draw a current through the gate;
now let's the current across resistors will be 1 miliamper, so R2 will be 2.5 KOhm. So, to regulate 150V you'll need (150-2.5)=125.5 KOhm, for 250V you will need 225.5 KOhm, and so on...
But I still don't understand why do you want to vaste a tube if you can use one zener diode, or a zener with a transistor if you don't have powerful enough zener?
Suppose, the tube's filament opens up, then unregulated high voltage goes to where lower regulated should go...
Also, it is high and unregulated while the tube is cold... 
Jarthel,
The equation for the voltage at the input to the TL431 is:
Vin = Vshunt * [ R2 / (R1 +R2)]
Now... declare Vin to be 2.495 Volts.
Put these into the equation and solve for R1:
R1 = (R2 * ( Vsh - 2.495 )) / 2.495
How to choose R2? I just happen to know that 24.9kOhms is a good value for R2. Here's why: R2 should always have 2.5 Volts across it... so we know the current flowing through it. The input to the TL431 steals a little current from the divider, but we don't want this "theft" to cause an error. Furthermore, the amount of current it steals changes all over with temperature.
So we want the current flowing through R1 & R2 to look huge in comparison to little current being stolen... thats where the 24.9k comes in. So look up the "input bias current" for the TL431... then calculate the current in R2... and you can figure out the "swamping factor".
The equation for the voltage at the input to the TL431 is:
Vin = Vshunt * [ R2 / (R1 +R2)]
Now... declare Vin to be 2.495 Volts.
Put these into the equation and solve for R1:
R1 = (R2 * ( Vsh - 2.495 )) / 2.495
How to choose R2? I just happen to know that 24.9kOhms is a good value for R2. Here's why: R2 should always have 2.5 Volts across it... so we know the current flowing through it. The input to the TL431 steals a little current from the divider, but we don't want this "theft" to cause an error. Furthermore, the amount of current it steals changes all over with temperature.
So we want the current flowing through R1 & R2 to look huge in comparison to little current being stolen... thats where the 24.9k comes in. So look up the "input bias current" for the TL431... then calculate the current in R2... and you can figure out the "swamping factor".
Re: Re: Re: Re: need help understanding voltage regulator schematic (using CCS) from Rale
how did you come up with 125.5Kohm?
I was thinking along the lines of
150V - 2.5V = 147.5V / 1mA = 147.5Kohm?
say the unregulated voltage across from across R1 and R2 combined is 300V. (not sure if this info is even important)
thank you.
Wavebourn said:
how did you come up with 125.5Kohm?
I was thinking along the lines of
150V - 2.5V = 147.5V / 1mA = 147.5Kohm?
say the unregulated voltage across from across R1 and R2 combined is 300V. (not sure if this info is even important)
thank you.
The voltage I called Vshunt, or Vsh, is the same as B+. Sorry, I think in terms of the circuit.
Does that clear things up?
'ang on mite... If B+ (Vsh) goes up, then the 2.5 V goes up too. Then the TL431 starts sinking more current to ground through itself and the tube... and it keeps doing this until its input comes back to 2.5 Volts. You see the TL431 is actually a clever little gizmo... it is an op-amp with a "current" output, and a voltage reference all wrapped in one neat little package.
Now... this is a shunt regulator... you do want a shunt right???
Does that clear things up?
'ang on mite... If B+ (Vsh) goes up, then the 2.5 V goes up too. Then the TL431 starts sinking more current to ground through itself and the tube... and it keeps doing this until its input comes back to 2.5 Volts. You see the TL431 is actually a clever little gizmo... it is an op-amp with a "current" output, and a voltage reference all wrapped in one neat little package.
Now... this is a shunt regulator... you do want a shunt right???
Jarthel,
What exactly are you trying to regulate? I ask because shunt regs have to be applied rather carefully...
The is a bit abstract but, shunts are to used to regulate a current. That is not to say it is a "current regulator"... it's not. A shunt regulator needs to have a current source for a supply... not a voltage.
Just one resistor solves all this basically...
What exactly are you trying to regulate? I ask because shunt regs have to be applied rather carefully...
The is a bit abstract but, shunts are to used to regulate a current. That is not to say it is a "current regulator"... it's not. A shunt regulator needs to have a current source for a supply... not a voltage.
Just one resistor solves all this basically...
hope this text schematic comes out clearly
230VAC transformer secondary -> tube rectifier -> choke (10H 90ohm) -> 100uF -> CCS circuit (70ma? - not sure yet) (as found in Bas Horneman's website) -> the voltage regulator as found in the raleigh audio website.
using PSUD2, the voltage across the 100uF is 170VDC. I need 150VDC at the output of the raleigh audio circuit.
I'm just confused on how to calculate the R1 and R2 values to get the 2.5V for the TL431 and at the same time, the resistor values will determine the B+
230VAC transformer secondary -> tube rectifier -> choke (10H 90ohm) -> 100uF -> CCS circuit (70ma? - not sure yet) (as found in Bas Horneman's website) -> the voltage regulator as found in the raleigh audio website.
using PSUD2, the voltage across the 100uF is 170VDC. I need 150VDC at the output of the raleigh audio circuit.
I'm just confused on how to calculate the R1 and R2 values to get the 2.5V for the TL431 and at the same time, the resistor values will determine the B+
jarthel said:
Resistors represent a negative feedback. The IC compares the voltage on input against internal 2.5V it has "in mind", and if the voltage is higher it draws more current that causes the tube to draw more current until the IC sees 2.5V on the input, and vice versa.
You defenitely are asking wrong people why that particular guys put such strange schematics on their website. Ask them.
poobah said:Jarthel,
What exactly are you trying to regulate? I ask because shunt regs have to be applied rather carefully...
The is a bit abstract but, shunts are to used to regulate a current. That is not to say it is a "current regulator"... it's not. A shunt regulator needs to have a current source for a supply... not a voltage.
Just one resistor solves all this basically...
the examples in onsemi's tl431 datasheet uses Vin so maybe it also uses voltage?
Hi jarthel,
poobah provided a correct formula in post #5 above. So, if you pick R2 to be 24.9K and want your B+ to be 150V,
R1 = (24.9k * (150 - 2.495)) / 2.495 = 1.47M
Now, it turns out that 1.47M is a standard value so you are done.
However, often it doesn't turn out that close and you will have to play around with the values of R1 and R2 to get the value for B+ that you want.
Dave
poobah provided a correct formula in post #5 above. So, if you pick R2 to be 24.9K and want your B+ to be 150V,
R1 = (24.9k * (150 - 2.495)) / 2.495 = 1.47M
Now, it turns out that 1.47M is a standard value so you are done.
However, often it doesn't turn out that close and you will have to play around with the values of R1 and R2 to get the value for B+ that you want.
Dave
Hi,
The tube provides isolation from the high voltage. The tube is in series with the TL431 so the same current goes through both.
The tube should be chosen by its max plate voltage and max plate current plus a bit for good measure. For plate voltage I usually pick the value of the regulated voltage as a limit. So in your case any tube that can have 150V or more on it. You don't need much current, just the expected variation in the load current plus a few, say five, milliampers.
Dave
The tube provides isolation from the high voltage. The tube is in series with the TL431 so the same current goes through both.
The tube should be chosen by its max plate voltage and max plate current plus a bit for good measure. For plate voltage I usually pick the value of the regulated voltage as a limit. So in your case any tube that can have 150V or more on it. You don't need much current, just the expected variation in the load current plus a few, say five, milliampers.
Dave
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