I have only just joined All about circuits as a result of attempting to construct a new Regulated 60V 3Amps supply for my refurbished Bailey 30Watt amplifier (it had been viciously attacked in my workshop by wood lice, slugs and damp and smoked quite profusely when powered up! ).
The original voltage regulator used discrete components (now obselete ) and I thought it would be nice to use more modern technology (not so modern as an SMPSU!!).
I have built a number of supplies and bread boarded them, but they all seem to be somewhat noisy. The initial challenge was that the output from the Reservoir capacitor was in the region of 95Volts which only the LT783 could handle. I replaced the transformer such that the voltage is now a more modest 75 Volts, which is still a tad high for the LM317AVH BUT it seems to cope OK.
My query is related to the inclusion of the pass transistor in the circuit. Most of the application data I have read (e.g TI, LT,) tend to place the transistor such that it is switched on by the current flowing INTO the regulator through a resistor connected across the emitter and base and involve the regulator in supplying a smaller part of the current to the load. My most successful attempt was actually using the output from the regulator by connecting it directly to base of the pass transistor (a Toshiba 2SC5200) with the load connected to the emitter.
I have simulated both approaches using LTspice and they both appear to work OK but I don't know how to measure ripple and noise using LTspice.
If someone could please comment on my approach I would be most grateful, I have been around the houses quite a few times and am very befuddled about this - maybe I should not have dismissed a buck converter, though I would have problem soldering the very small technology we have now (my 60W Solon iron is a bit on the large size).
Regards,
Don
The original voltage regulator used discrete components (now obselete ) and I thought it would be nice to use more modern technology (not so modern as an SMPSU!!).
I have built a number of supplies and bread boarded them, but they all seem to be somewhat noisy. The initial challenge was that the output from the Reservoir capacitor was in the region of 95Volts which only the LT783 could handle. I replaced the transformer such that the voltage is now a more modest 75 Volts, which is still a tad high for the LM317AVH BUT it seems to cope OK.
My query is related to the inclusion of the pass transistor in the circuit. Most of the application data I have read (e.g TI, LT,) tend to place the transistor such that it is switched on by the current flowing INTO the regulator through a resistor connected across the emitter and base and involve the regulator in supplying a smaller part of the current to the load. My most successful attempt was actually using the output from the regulator by connecting it directly to base of the pass transistor (a Toshiba 2SC5200) with the load connected to the emitter.
I have simulated both approaches using LTspice and they both appear to work OK but I don't know how to measure ripple and noise using LTspice.
If someone could please comment on my approach I would be most grateful, I have been around the houses quite a few times and am very befuddled about this - maybe I should not have dismissed a buck converter, though I would have problem soldering the very small technology we have now (my 60W Solon iron is a bit on the large size).
Regards,
Don