Yeah...
Just needed more current. Under no load, no problem adjusting to +15 volts and -15 volts for the two regs.
CCS current at +15 volts out: 1.64V across 5R6, 292 mA
CCS current at -15 volts out: 1.07V across 5R6, 191 mA
Maybe I need around 4R7 for the positive reg, and 3R for the negative reg to achieve CSS around 350mA-400mA.
Just needed more current. Under no load, no problem adjusting to +15 volts and -15 volts for the two regs.
CCS current at +15 volts out: 1.64V across 5R6, 292 mA
CCS current at -15 volts out: 1.07V across 5R6, 191 mA
Maybe I need around 4R7 for the positive reg, and 3R for the negative reg to achieve CSS around 350mA-400mA.
I did not want to run
it for long under no load, just long enough to set output voltage and measure for CCS current. I will order some more resistors for R1 and report back later.
I used 3 yellow LEDs and two red LEDs, these parts are from the minikits, as are the transistors/FETs. I did not measure the LEDs for Vf just used them as is, feeling I usually have to adjust R1 anyway. I had to use different R1 values for my Quanghao V 1.0 boards as well, so I should have realised that.
it for long under no load, just long enough to set output voltage and measure for CCS current. I will order some more resistors for R1 and report back later.
I used 3 yellow LEDs and two red LEDs, these parts are from the minikits, as are the transistors/FETs. I did not measure the LEDs for Vf just used them as is, feeling I usually have to adjust R1 anyway. I had to use different R1 values for my Quanghao V 1.0 boards as well, so I should have realised that.
Yes, its the normal learned setting procedure anyway, but with your feedback later on we can be more informed of what happens with the actual fresh Mosfet and led batches sourced for the minikits and be able to give better ballpark values to the novice people. Mine are older batches and were hitting ~2V difference across Rset in the protos for instance. Your regs proved OK non the less. That's cool.
Guide small update
Guys, I had fixed a couple of parts numbering typos and added a paragraph in the end regarding different (lower) ballpark values for R1 (101,201,301) setting the CCS current. They are probably nearer to the mini-kits Mosfet Vgs and LEDs characteristics than to those from my prototypes, based on two early builds feedback. Its still in page #1 download link (on Hotfile this time).
Guys, I had fixed a couple of parts numbering typos and added a paragraph in the end regarding different (lower) ballpark values for R1 (101,201,301) setting the CCS current. They are probably nearer to the mini-kits Mosfet Vgs and LEDs characteristics than to those from my prototypes, based on two early builds feedback. Its still in page #1 download link (on Hotfile this time).
My results are similar that of Barrows:
Output +15V, -15V (for a Legato 3.1)
Voltage across R101: 1.490V Led String D102-104: 5.705V IRF9610: 4.215 V
Voltage across R101: 1.020V Led String D102-104: 5.720V IRF9610: 4.700 V
So really coherent results, but then I need very low value resistors to get 400mA:
Positive reg 3R9
Negative reg 2R5
Output +15V, -15V (for a Legato 3.1)
Voltage across R101: 1.490V Led String D102-104: 5.705V IRF9610: 4.215 V
Voltage across R101: 1.020V Led String D102-104: 5.720V IRF9610: 4.700 V
So really coherent results, but then I need very low value resistors to get 400mA:
Positive reg 3R9
Negative reg 2R5
On the other hand lower voltage across the setting resistor cuts a lot on its dissipation. Which is a good thing and comes handy in high current settings. We will just use a half distance rule of thumb as ballpark voltage drop expectation. Say 1.25V-1.3V to start with. I have already added that recommendation in the guide.
First 5.5V out build is working!
568mA CCS, 30mV voltage drift, perfect clean output, no oscillations.
I noticed when tuning the CCS resistor, that the voltage across it is more with bigger resistor values and less with smaller resistor values.
For example:
12Ω resistor, 1.87V
2Ω2 resistor, 1.25V
Is this normal?
568mA CCS, 30mV voltage drift, perfect clean output, no oscillations.
I noticed when tuning the CCS resistor, that the voltage across it is more with bigger resistor values and less with smaller resistor values.
For example:
12Ω resistor, 1.87V
2Ω2 resistor, 1.25V
Is this normal?
Attachments
Work in progress for my psu for the simplistic RIAA
It will be a 45VDC supply.
BTW, Salas: how much current does my 15mA RIAA consume, what would be a correct load resistor to test the psu?
Franz
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
It will be a 45VDC supply.
BTW, Salas: how much current does my 15mA RIAA consume, what would be a correct load resistor to test the psu?
Franz
~35mA per channel. 560R 10W for simulating both channels draw and holding well at 3.6W self absorbing dissipation. 5W if you will be rather quick. Don't rest the dummy on something nylon or paper.