Compact Power Amplifier LPC1
The 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 most class AB amplifiers. Crossover distortion at zero-crossings like in class AB does not 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, where active fan-cooling is not possible.
In most class-D Amplifiers, the voltages are limited by the driver-IC at 80 or 100 V. With our patented driver circuit with galvanic isolation the driver is independent of the inverter-voltage. in this amplifier makes higher supply- and output-voltages possible, at which high power can be generated without the need for a full bridge or extreme low load-impedance. This amplifier can work with a supply voltage of typically 160 VDC, limited only by the 200V N-channel mosfet’s. The maximum output voltage is 70 V peak.
In the LPC2, the mosfet’s are replaced by 250V-fets, making a supply of 2x100V possible. Maximum output-voltage is increased to >80V amplitude.
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 so 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 to the transition time of the output, and a large inductive load makes this transition time less dependent of output-currents, eliminating the dead-time-distortion.
The 2nd distortion mechanism is supply-line pollution, generating inter-modulation of the output signal. With a patented PWM modulator this distortion is eliminated completely by canceling all modulating effects 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 symmetrical inputs should be connected in parallel and in anti-phase. This way the output power can be doubled at twice the impedance, till 2kW in 4 Ohm.
One LPC1 module supplied with 2x 80V can deliver 1000W RMS in 2 Ohms or 600W RMS in 4 Ohms.
It can work with any supply-voltage between 2x 45 and 2x 90V.
The small heat sink integrated in the brick housing provides enough cooling in free air at short peak power or 300 W continuous or average power. More passive cooling for 1,2 kW continuous power 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 in racks or cabinets.
The power-efficiency is 90%, only 10% of output-power is conducted to the heat-sink.
Airflow is not needed.