Power Amplifier LPC1
Amplifier LPC1 presented here combines some properties like high output power,
high sound quality and compact housing in brick-form.
The harmonic distortion, typically
0.1 % in most class D amplifiers, is eliminated here with some patented circuits.
Distortion is very low (<< 0.003 %@ 1kHz) at average listening levels
(0-400W) which makes this amplifier sound better than a good class AB amplifier.
Crossover distortion at zero-crossings like in class AB doesn't occur at all.
The remaining distortion components are low order harmonics increasing gradually
with output level like in loudspeakers and most ears.
The main application of the amplifier module is construction inside loudspeaker
cabinets or with 2 or more modules and a supply-unit inside a 19"-rack
as a PA-amplifier, in which active fan-cooling is not possible.
class-D Amplifiers, the voltages are limited by the driver-IC at 80 or 100 V.
A patented driver circuit with galvanic isolation in this amplifier makes higher
supply- and output-voltages possible, at which high power can be generated without
the need for a bridge or unpractical low impedance's. This amplifier can work
with a supply voltage of typically 160 VDC, limited only by the N-channel mosfet's.
The maximum output voltage is 70 V peak.
The 1st most common distortion mechanism
in class D amplifiers is the dead time between the off-switching of one mosfet
and the on-switching of the other. In this short period both mosfet's are in
off-state and the output is floating. The momentary voltage in this period is
strongly dependent on load current and thus non-linear, generating a kind of
crossover distortion at higher current-levels.
In the patented driver circuit, this dead time is much shorter and matched accurately
to the transition time of the output, eliminating this dead-time-distortion
The 2nd distortion mechanism is supply-line pollution, generating intermodulation
of the output signal. With a patented PWM-generator this distortion is eliminated
completely by compensating the modulation from the supply-voltage.
Unlike most class-D amplifiers, the
amplifier module described here is just half of a bridge, with one output-node
connected to ground. Output-voltage and Power can be doubled with 2 modules
in bridge-mode. The 2 outputs should be connected in anti-series, and the 2
inputs should be connected in parallel and in anti-phase. This way the output
power can be doubled at twice the impedance.
small heat sink integrated in the brick housing provides enough cooling in free
air at short peak power or 300 W continuous power. More passive cooling for
1,2 kW continuous is possible by mounting the module to an external heat sink
or housing. Two sides of the module are made flat for mounting easily at bigger
surfaces. For use inside closed loudspeaker-cabinets a fan is not possible
and not needed.
Module with cover removed, last version.
Output Power :
( driven at 1kHz sine, <0.1%THD, supply voltage 2*80V)
4 Ohms: 600 Watts RMS
2 Ohms: 1100 Watts RMS
1 Ohms: 1800 Watts Peak
per 2 modules, bridged:
8 Ohms: 1200 Watts RMS
4 Ohms: 2200 Watts RMS
2 Ohms: 3600 Watts Peak
Slew rate: 16 V/ microsec
Frequency Response :
+/- 0.1 dB, 20 Hz -20 kHz at 2 Ohms
+/- 1.2 dB, 10 Hz -20 kHz at 1 or 4 Ohms
+/- 3 dB, 1 Hz - 40 kHz at 2 Ohms
Overshoot squarewave: 10 %
Total Harmonic Distortion (THD)
< 0.03 %, -70 dB , 1000W, 2 Ohms, 1 kHz
<0.01 %, -80 dB , 700 W in 2 Ohms or 500W in 4 Ohms, 1 kHz
<0.003 %, -90 dB , 400 W in 2 or 4 Ohms, 1 kHz
Output Noise : 0.15 mV RMS,
-110 dB referenced to full output (20Hz-20kHz, unweighted)
Switching Frequency (250 kHz) at output : <50 mV RMS
Damping Factor : >150 (4
Ohms, 2 Hz- 500 Hz)
Input Sensitivity : 0.75 Volt
RMS or 1.07 V peak for full output (1 kW in 2 Ohm)
Voltage Gain : 60 X (35 dB)
Input Impedance : 2 * 220
Load Protection : Fuseless
short-circuit protection, clip limiting, current limiting at 60A.
Cooling : Passive free-air
at average signal < full power -6 dB,
With external heat sink at full power continuous.
Size : 200 mm W x 50 mm H
x 100 mm D
Power Efficiency : 93% (2
Ohms) to 95% (4 Ohms), at half to full power.
Supply requirements :
Main supply voltage : 2* 40- 80V DC, depending on power.
(Peak output voltage = 0,83
0,87 * supply voltage)
Idle-current: supply voltage/ 1,2 kOhm (60-70 mA at 2*80V)
Max current: 28 Amps peak, 14 Amps average, (2*80V, 1kW sine)
2nd supply (driverstage): voltage:
2* 12 V DC
current: 250 mA, +12V,
50 mA, -12V