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参数资料
| 型号： | AN-1192 |
| 厂商： | National Semiconductor Corporation |
| 英文描述： | broad portfolio of monolithic power integrated circuits covering power levels |
| 中文描述： | 丰富的产品组合覆盖功率级别单片功率集成电路 |
| 文件页数： | 2/21页 |
| 文件大小： | 548K |
| 代理商： | AN-1192 |
1.0 Introduction
National Semiconductor has a broad portfolio of monolithic
power integrated circuits covering power levels from a few
hundred milliwatts up to 60W of non-clipped continuous
average power. These ICs cover most audio applications by
themselves, however, for really high power applications,
other methods need to be employed because IC packages
have limited power dissipation capabilities.
There are many different ways of obtaining over 100W of
output power. Most high-end power amplifier manufacturers
utilize discrete circuits which allows them to market their
amplifiers as “specially designed.” However, there is a price
to be paid for discrete amplifier designs; they are complex,
difficult to design, require many components, lack the com-
prehensive protection mechanisms of integrated circuits and
are not as reliable.
Other methods of obtaining output power greater than 100W
include the use of power ICs as drivers for discrete power
transistors. There are a number of these types of circuits, but
they too possess all of the same flaws as discrete circuits,
including a lack of comprehensive output stage protection.
2.0 Objective
The objective is to provide simple high power solutions that
are conservatively designed, highly reliable and have low
part count. This document provides three specific, but not
unique, application circuits that provide output power of
100W, 200W, and above. These circuits are the parallel,
bridged, and bridged/parallel configurations.
These three circuits are simple to understand, simple to build
and require very few external components compared to
discrete power amplifier designs. Simplicity of design and
few components make this solution much more reliable than
discrete amplifiers. In addition, these circuits inherently pos-
sess the full protection of each individual IC that is very
difficult and time consuming to design discretely. Finally,
these circuits are well known and have been in industry for
years.
3.0 Conclusion
The BR100 (100W Bridged Circuit), PA100 (100W parallel
circuit), and the BPA200 (200W Bridged/Parallel Circuit) are
high power solutions that can be used in many applications,
but they are primarily targeted for home theater amplifier
applications such as powered subwoofers, self-powered
speakers, and surround sound amplifiers.
While bridged amplifier configurations are able to provide
high power levels, they also consume four times more power
than a conventional single-ended solution. However, it is
feasible to conservatively design a 100W bridged amplifier
solution, as will be shown here. The bridged solution is
designed to drive an 8
nominal load for self-powered
speaker or powered subwoofer applications.
The parallel amplifier is another configuration that can be
used to obtain higher output power levels by combining two
IC outputs and doubling output current drive capability. The
parallel topology provides a great way of achieving higher
power levels while keeping within IC power dissipation limits
by driving low impedance loads, which is the case for many
self-powered speaker and powered subwoofer designs. The
main advantage of the parallel configuration is its ability to
divide total power dissipation between ICs, since each am-
plifier is providing half of the load current.Another advantage
of the parallel design is that unlike the bridge design, more
than two ICs can be used. In fact, any number of ICs can be
used in a parallel design and when configured the same will
share the power dissipation equally. For example, using four
ICs to drive a 1
load means that each IC dissipates 1/4 of
the total power dissipation. In other words, the load to each
IC looks like a 4
load (Number Of ICs in Parallel * Load
Impedance = Load Impedance seen by each individual IC.)
Odd numbers of ICs can also be used.
For lower impedance loads (
<
8
), the parallel circuit is a
good solution for 100W power levels using just two devices.
Power levels above 100W may be obtained by using more
than two devices to increase output current capability and
power dissipation limits along with lower impedance loads.
If the bridged and parallel configurations are combined, the
outcome is a very high power amplifier solution that far
exceeds the capabilities of one IC alone, while maintaining
reasonable power dissipation levels within each IC. The
bridged portion doubles the output voltage swing and qua-
druples the total power dissipation while the parallel portion
halves the current between each IC set and divides the total
power dissipation between each of the four ICs. The result is
higher system output power with each IC not exceeding its
individual power dissipation capabilities. Higher output
power levels are attained, while the ICs run at a normal
temperature, keeping long term reliability high. The sche-
matic of the Bridged/Parallel Amplifier is shown in Figure 13.
The bridged/parallel circuit using four devices will produce
the maximum output power (
>
200W) into loads with an
impedance from 4
to 8
. For loads less than 4
, additional
devices may need to be placed in parallel or the supply
voltage reduced.
The data in the following sections will exemplify that the
parallel, bridged, and bridged/parallel solutions using mul-
tiple power ICs can meet high fidelity specifications while
providing output power from 100W up to 400W. The low
noise and excellent linearity traits of the monolithic IC are
transferred to the high power solution, making the circuit
even more attractive. In addition, the protection mechanisms
within the IC, which are not easily designed discretely, are
inherently designed into the circuit.
While the data show what specs can be achieved by the
configurations, as always, good design practices need to be
followed to achieve the stated results. In addition to good
electrical and layout design practices, the thermal design is
equally critical with Overture ICs. The following section will
expand on the thermal design aspects of Overture ICs. This
concept of “design by power dissipation” is applicable to all
types of high power solutions.
The PA100, BR100, and BPA200 schematics and test re-
sults exemplify what can be achieved with proper compo-
nent selection, thermal design, and layout techniques.
4.0 Thermal Background
The voltage and current ratings of a power semiconductor
are typically the first specs considered in designing high
power amplifiers. The same is true for an integrated mono-
lithic power amplifier. However, power dissipation ratings are
equally important to the long term reliability of the power
amplifier design. When using a monolithic IC in its intended
application and within its specified capabilities, the thermal
design is relatively straightforward. When an IC is used
beyond is capabilities, as in high power circuits, power dis-
sipation issues become more critical and not as straight-
A
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