Innovative CircuitsApplication Notes
Should you use a pre-regulator?
The high voltage Superpower
Superpower in audio circuits
Load Sense Connection
Dynamic Performance
Improving dynamic performance
Does Superpower have an output current limit?
Improving noise performance
Should you 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.
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.
Superpower 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.
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 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.
Dynamic Performance
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.
Improving dynamic performance
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.
Does Superpower have an output current limit?
To provide the absolute minimum output impedance, the standard
(TO-220 equiv.) Superpowers 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.
High voltage and high current Superpower versions will be available by year end (2010) with current limit and thermal protection. Contact us about availability or to discuss your specific requirements.
Improving noise performance
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.
Belleson® has introduced a small form factor, high output current Superpower™
regulator. The new SPJ78 and SPJ17 devices are available with Vout of +3.3V, +5V
and +6.25V, at current to 2 amps.