As I wrote before, I don't know what the symbols in your calculation are.
What are the de-rating factor, Ts, Tc and Rth c-s?
Ts = heatsink temperature at the interface with the device.
Tc = device temperature at the interface with the sink, but most assume this is also the same temperature at the interface with the semiconductor material.
Rth c-s the the Thermal resistance from case to sink.
The sink is usually specified for dissipation when the sink backplate is at some fixed temperature ABOVE the ambient air temperature (Ta).
This DIFFERENCE between Ta and Ts is usually from 70Cdegrees to 80Cdegrees. The manufacturer usually tells you somewhere. It can take a bit of searching.
When the Ts-Ta differential is different from the specification value YOU must adjust the Rth s-a to account for the new value.
typically DF=1.5 when the diff is around 10 to 15C degrees ranging down to ~1.2 when diff is around 30 to 40Cdegrees. DF = 1 when the diff exactly matches the specification value.
esp and many other websites give all this backgound information.
You will also find all of this on this Forum.
Tc = device temperature at the interface with the sink, but most assume this is also the same temperature at the interface with the semiconductor material.
Rth c-s the the Thermal resistance from case to sink.
The sink is usually specified for dissipation when the sink backplate is at some fixed temperature ABOVE the ambient air temperature (Ta).
This DIFFERENCE between Ta and Ts is usually from 70Cdegrees to 80Cdegrees. The manufacturer usually tells you somewhere. It can take a bit of searching.
When the Ts-Ta differential is different from the specification value YOU must adjust the Rth s-a to account for the new value.
typically DF=1.5 when the diff is around 10 to 15C degrees ranging down to ~1.2 when diff is around 30 to 40Cdegrees. DF = 1 when the diff exactly matches the specification value.
esp and many other websites give all this backgound information.
You will also find all of this on this Forum.
No. For the SSHV, which is Shunt Regulator, you need to set the load consumption (in your case 50mA) plus whatever you decide for the Shunt Regulator (in your case 20mA, which is the recommended minimum), total 70 mA.
As for calculating the needed heatsink for certain load, I found few online calculators and guides:
Heatsink Calculations
Online Calculator .:. Heatsink
Power Transistors and Heat sinks
Heatsink Calculations
Online Calculator .:. Heatsink
Power Transistors and Heat sinks
There are usually two parameters of the circuit you want to power:
1. quiescent current (zero signal current);
2. signal current (AC current).
If you mentioned p.1 as a "consumption current" and p.2 as "want to shunt" current - then you were right.
The signal current in the circuits of small signal tube amplifiers, practically doesn't change the consumption from the regulator, not significantly.
In this case the consumption current is 50mA and the minimum headroom for the shunt regulator is 20mA. There is no other regulator, besides the shunt one, that requires extra current.
While I agree with you in general in this particular case we can't know exactly what the 50 mA is for. Some circuits (for example, SRPP) can have current swings as much as twice the quiescent current, which (the quiescent current), for example, in ECC88 case can be as much as 5-10мА. Stereo version of the circuit can have 10-20mA AC current demand easily. So to prevent misinterpreting I pointed out what the additional "shunted current" should be taken into the account.
It seems that what you wrote doesn't relate to the original question which was:
This question implies that the person asking think there are 2 regulators (regulator and shunt), while there is only one shunt regulator, which needs only one amount of headroom, say 20mA. There isn't a regulator plus shunt, each needing ones' own headroom.
The question wasn't about possible headroom for the consumption.
You may read my answer then. I clearly states, that
"If you mentioned p.1 as a "consumption current" and p.2 as "want to shunt" current - then you were right."
Joshua,
generally ClassA stages do not operate at constant current.
Expect a maximum current change of +100% and -99% of the quiescent (no signal) current for worst case operating conditions. There will be some that exceed the +100% estimate.
If the quiescent current of all the ClassA stages is 20mA, then I suggest that at least 40mApk be allowed as the likely peak demand.
generally ClassA stages do not operate at constant current.
Expect a maximum current change of +100% and -99% of the quiescent (no signal) current for worst case operating conditions. There will be some that exceed the +100% estimate.
If the quiescent current of all the ClassA stages is 20mA, then I suggest that at least 40mApk be allowed as the likely peak demand.
I thought the original question was about necessary Shunt regulator current setting to suit the demands of the circuit.
Your nonsense answer implying constant current operation would lead him to the wrong answer/s.
Am I correct in recalling you argued this constant current claim twice before?
Your nonsense answer implying constant current operation would lead him to the wrong answer/s.
Am I correct in recalling you argued this constant current claim twice before?
No, the original question was confusing about the shunt regulator, thinking a different current headroom is needed for the regulator and a different one for the shunt.
Why do you need 10 mA above the consumption?
The SSHV2 needs 20 mA above your maximum consumption.
If you need 60 mA for consumption, set SSHV2 to 80 mA.
