While home theater systems, AV receivers, musical instruments, car entertainment and other high performance portable consumer devices are rapidly taking advantage of class D amplifiers for superior audio performance, their power needs are different. Individually designing a high performance class D audio amplifier for each of these products is time consuming, and can cost lot more. Furthermore, any delay in marketing the final product could hamper its success.
Alternatively, a single design platform that features scalable output audio power can simplify a designer's job, resulting in faster turnaround of the amplifier with fewer components, thus enabling a manufacturer to save time to market with the end product, as well as trim its cost. Consequently, simply changing the output MOSFETs with appropriate voltage ratings enables the designers to use the same base circuit design to create multiple power levels up to a total of 500W for a stereo output.
To achieve that goal, a reference design platform for a two-channel class D audio power amplifier with scalable output power has been developed. Besides allowing a designer to scale the output power stage from 25W per channel to 250W per channel, this IRAUDAMP7D audio design platform also offers selectable half-bridge (stereo) and full-bridge (bridged) topologies. For that, it incorporates the integrated high voltage class D audio driver IC IRS2092, along with its digital audio dual MOSFETs, such as IRFI4024H-117P, IRFI4019H-117P, IRFI4212H-117P and IRFI4020H-117P, on a single layer printed circuit board (PCB). Additionally, this design platform also presents an optimum PCB layout for peripheral circuits using a single sided board. As a result, it requires a small heatsink for normal operation (one-eighth of continuous rated power). Furthermore, all the required housekeeping power supplies and protection circuits are included in this reference design.
Although, the class D audio driver IRS2092 is crafted for applications between 25 and 250W per channel in half-bridge mode, it can also be used in full-bridge topology to boost the total output power to 1,000W for some specific application. A designer can extend the power to higher than 1,000W by placing external gate buffers.
Using state-of-the-art G5 HVIC technology, the 200V class D audio driver IRS2092 integrates features and functions that facilitate the design and construction of a high power class D amplifier using through-hole components on a single sided board. This high voltage audio driver is combined with optimized digital audio power MOSFETs to attain up to 250W per channel or 500W total audio power from a single layer PCB.
Fundamentally, implementing the advanced process technology, the new audio driver chip integrates four essential functions required for high-performance class D audio amplifier design on a single chip. These include error amplifier, PWM comparator, gate driver and robust protection circuitry. The built-in protection circuitry simplifies the complex task of overload protection with self-reset control and under-voltage lockout protection (UVLO). In essence, multiple protection features available include over-current protection (OCP), high-side and low-side MOSFET over-voltage protection (OVP), high-side and low-side MOSFET DC protection (DCP) and over temperature protection (OTP). In addition, the chip delivers programmable preset dead-time for improved total harmonic distortion (THD).
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