Innovative CircuitsFrequently Asked Questions
Should I use a pre-regulator?
What is special about the high voltage Superpower?
Why is Superpower used in audio circuits?
What is the Load Sense Connection?
What can affect dynamic performance measurements?
Can dynamic performance be improved?
How is dynamic performance measured?
Does Superpower have an output current limit?
Can noise performance be improved?
Should I use a pre-regulator?
Superpower works best without a pre-regulator. The best source of
energy for a Superpower is a full wave rectified and filtered power
supply. A pre-regulator increases source impedance and limits dynamic
current to the Superpower.
What is special about the high voltage Superpower?
Superpower uses a boot-strapped (self-powered) floating reference
and error amplifier that sets its own power supply voltage range. The
Superpower design has output voltage set by a constant current through
a resistor. Only this single resistor and one transistor have to
sustain a constant high voltage, making the circuit more reliable than
other designs. It also does not require a separate floating transformer
or other costly and complicated circuitry.
The low drop out voltage keeps power dissipation in the load where
it belongs, not in the regulator. For situations where low drop out is
not possible, the high voltage Superpower is designed with TO-220
devices to allow easy heat sinking.
Why is Superpower used in audio circuits?
Clean, clear audio needs reserve power for bass and low midrange
frequencies, fast response for mid and high frequencies and low noise
across the audio spectrum and beyond. These requirements are not
independent but must be met simultaneously.
The step responses shown in the load regulation page
illustrates how Superpower can provide a great deal of current in a
very short time. The spectra in the line
regulation page show great noise performance across the audio
spectrum.
So no matter what your audio requirements may be, a Superpower will contribute to clean, clear dynamics in any audio subsection except a power amplifier output.
What is the Load Sense Connection?
Superpower is available with a load sense connection, allowing
voltage to be better controlled at the load by including impedance
between the regulator and the load in the regulator feedback loop. The load sense
connection has a potential to introduce noise so careful routing and
placement of both the regulator and its load are essential.
What can affect dynamic performance measurements?
Delivery of high current means a small amount of resistance can
cause relatively large voltage changes. One amp times 10 milliOhms is
10 mV, thousands of times more voltage than the
AC at the output of a Superpower. To achieve the measurements as seen
in the graphs and photos shown, extreme care must be taken to minimize
wire and PC trace lengths, maximize wire gauge and carefully place
measurement probes.
Can dynamic performance be improved?
Superpower has excellent dynamic performance as designed. This can be improved with minimum cost and board space. First, a local by-pass capacitor for the input voltage should be located near Superpower, 100µF or more electrolytic. A second 0.1µF ceramic (X7R or Z5U) cap in parallel with this may improve high frequency noise rejection. As seen in the pre-regulator notes above, a very low impedance input source is best.
Albert Shan has observed the following regarding input capacitor:
- Anyway, I've now soldered a cap directly on the input of superpower. It didn't really improve the output noise, but the interesting thing to note is that it does alter the sound. I wasn't expecting this to happen, given superpower's very high noise rejection ratio. So far, I found that it really does take a good cap there, an audio cap preferably. I've tried Panasonic FM low ESR, Sanyo Oscon SP low ESR. The Sanyo sounded really bad. The Panasonic FM sounded almost as good as the Panasonic FC caps I've already got there for the filter caps. A cheap 330uF Rubycon cap also sounded bad (less ambient, more flat and dry). I ended up with a 1000uF Elna Silmic II cap which I have in my parts bin. It gives better detail, imaging, and it does make it sound special. So you may want to put in the application note that if user wants to further improve the sonic quality, an audio cap such as Elna Silmic / Silmic II is recommended.
How is dynamic performance measured?
Good question. A standard power supply has limitations on output current that affect dynamic performance of Superpower, so what can be used for a Vin source? The only solution we found so far is to use a Superpower regulated source as Vin to test another Superpower. We use a Superpower regulated supply to test both dynamic performance and ripple rejection.
Dynamic performance is tested by switching a resistor from Vout to ground through a high speed transistor.
Ripple rejection is tested by modulating the output of a Superpower and using it as the Vin supply for the unit under test.
Does Superpower have an output current limit?
To provide minimum output impedance and maximum current, SP and SPJ
products have no current limit and no thermal protection. Careful
design and heat sinking must be done to prevent damage to the Superpower
and your circuit.
The SPL product is a Superpower with output short circuit current limit circuitry. It is available now, see the description here for more information.
Can noise performance be improved?
Bootstrap powered by its own output, Superpower is inherently low
noise (see SPICE noise simulation results below). The high quality reference
and low error amplifier gain keep noise at a minimum.
However, it is possible to improve noise performance. Good input bypassing as described above decreases noise
(especially at low frequencies), as does a large electrolytic capacitor across the output.