Abstract:
The invention is a power amplifier circuit for providing a signal acceptable for use in audio amplifiers or similar applications without requiring a stable power supply free from fluctuations. An alternating current power supply signal rectified to a direct current signal is processed by two voltage multipliers. A voltage divider establishes a unity gain level, and the variance from this voltage is squared by the first voltage multiplier. This squared voltage is then multiplied with a triangular wave signal to generate a modulated triangular wave signal. The modulated triangular wave signal and a signal to be amplified, typically an audio signal, are processed by an internal comparator to generate a pulse width modulated signal. This modulated signal is processed by a power transistor network and filter to provide an amplified signal to a load device. By modulating the triangle wave signal to compensate for fluctuations in the power supply to the amplifier circuit, noise or ripples present in the power supply are demodulated, eliminating the requirement for a regulated power supply.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 60/489,664 filed Jul. 24, 2003. 
     
    
     TECHNICAL FIELD OF INVENTION 
       [0002]    The present invention relates to amplifier design, and more particularly to a power amplifier for audio and other signals. Still more specifically, the present invention relates to design of an amplifier circuit capable of manipulating an unregulated AC signal to provide an amplified signal to a load device, so that fluctuations in the power supply to the amplifier circuit are compensated for, and noise or ripples present in the power supply are removed, eliminating the requirement for a regulated power supply. 
       BACKGROUND OF THE INVENTION 
       [0003]    Power amplifiers are commonly used to amplify electrical signals supplying power to certain types of electronic devices, such as audio speakers. Most power amplifiers use, and depend upon, clean, regulated direct current (DC) power input. Unregulated DC power generated from unregulated alternating current (AC) is “noisy”, containing power fluctuations unsuitable for most power amplifying applications. 
         [0004]    In typical applications, power amplifiers must convert an unregulated, noisy 120-volt AC power source into a regulated, clean DC power source. If the unregulated AC power input is simply rectified to a DC power input, any fluctuations, noise or ripple in the AC power signal may be transferred to the DC power signal. The noise inherent in DC power in this situation may be translated to the amplified output signal. In audio applications, such excessive variances in the power supply will result in undesirable hum, distortions, and noise at the speaker. As such, there is a need for regulated DC power supplies to power applications with a reduced noise factor. 
         [0005]    Conventional power amplifiers rectify an AC signal to a regulated DC power source with transformers and other active inductive and capacitive circuits, which account for the majority of the weight, waste heat output, and cost of production associated with these prior-art amplifiers. As such, there is also a need for audio amplifiers that weigh less, produce less heat, and cost less. 
         [0006]    A number of approaches have been tried to minimize or overcome the above-identified problems. U.S. Pat. No. 4,042,890 to Eckerie filters the DC power signal to reduce high-frequency noise. U.S. Pat. No. 4,605,910 to Covill produces a switch modulated signal for producing an output signal that is independent of the supply voltage, thereby eliminating noise caused by fluctuating AC voltage signals. U.S. Pat. No. 4,737,731 to Swanson senses variations in the DC power signal and adjusts the gain in the audio frequency signal according to the variances to reduce modulation distortion. In U.S. Pat. No. 5,132,637 also to Swanson, a plurality of actuable power amplifiers are controlled by a correction signal to produce a cleaner signal. U.S. Pat. No. 5,777,519 to Simopoulos uses a correction signal as an input to a variable switching power supply to eliminate some noise in the power signal. 
         [0007]    However, each of these methods share the problems of high cost, high heat loss, high weight, and overall inefficiency. A different method for regulating the power output that eliminates the regulated DC power source would offer significant advantages in cost and efficiency as well as a significant reduction in weight and increase in output power. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention eliminates the need to regulate a DC power supply by regulating the gain of an amplifier in response to fluctuations and ripple in the unregulated DC power supply so that those fluctuations and ripples do not appear at the output power signal. Unregulated AC power may be supplied from a conventional AC outlet or from an isolation or other transformer. Unregulated AC power is first rectified into unregulated DC power, and this unregulated DC power signal is monitored by a voltage divider to establish a power supply “variance” signal. This variance signal is then squared by an analog multiplier. A second multiplier processes the signal from the first multiplier with a triangular wave signal to produce an input signal to an internal comparator. The first and second voltage multipliers comprise a triangular wave modulator. The resulting output signal from the second multiplier is the modulated triangular wave signal. 
         [0009]    An internal comparator accepts an input audio signal as well as the output signal from the second multiplier. This internal comparator monitors and processes the input audio signal with the modulated triangular wave signal to generate a Pulse Width Modulation (PWM) output signal. From the internal comparator, the PWM output signal is amplified by power device transistors, and the amplified PWM signal passes through filters to remove a high-frequency carrier component. The signal output from the filters is an amplified PWM power signal, which is then used to drive a load device. 
         [0010]    The variances in the power supply voltage are demodulated or removed by this approach, thereby eliminating the need for a regulated DC power supply. The invention provides for dynamic adjustment for noise in the unregulated DC power supply, resulting in a simpler and more efficient power amplifier to derive a clean, regulated, amplified power drive signal. The present invention also provides audio improvements including compression and frequency equalization. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawings in which like numerals represent like elements. 
           [0012]      FIG. 1  is a basic circuit block diagram illustrating a preferred embodiment of the functional components of the power amplifier of the present invention. 
           [0013]      FIG. 2  is a circuit schematic of a preferred embodiment of the AC power circuit. 
           [0014]      FIG. 3  is the circuit schematic of a preferred embodiment of the DC bridge rectifier and voltage divider. 
           [0015]      FIG. 4  is a circuit schematic of a preferred embodiment of the triangular wave modulator (TWM) containing two voltage multipliers. 
           [0016]      FIG. 5  is a circuit schematic of a preferred embodiment of the pulse width modulator (PWM) controller containing the triangular wave generator and pulse width modulation amplifier. 
           [0017]      FIG. 6  is the circuit schematic of a preferred embodiment of the power device transistor and filter. 
           [0018]      FIG. 7  is a circuit schematic of a preferred embodiment of the RMS-to-DC converter used to provide an additional signal for providing dynamic range compression, or Automatic Gain Control, to the amplifier circuit. 
           [0019]      FIG. 8  is a composite circuit schematic of a preferred embodiment of the present invention for a modulated triangular wave audio power amplifier. 
           [0020]      FIG. 9  illustrates the internal operative connectivity for the PWM controller illustrated schematically and described in detail in connection with  FIG. 5 . 
           [0021]      FIG. 10  is a block diagram of the modulated triangular wave audio power amplifier configured as a noise-canceling amplifier. 
           [0022]      FIG. 11  is a block diagram of the modulated triangular wave audio power amplifier configured to compress or expand dynamic range or for signal equalization or cancellation. 
           [0023]      FIG. 12  is a block diagram of the modulated triangular wave audio power amplifier configured to introduce an additional signal to output. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    In the following Detailed Description of the Preferred Embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. For example, intervening electrical components may be located along electrical connections, and electrical components of different ratings may be used, without departing from the scope of the present invention. Moreover, persons of ordinary skill in the art will know that numerous minor alternatives to a specific circuit design are possible, without departing from the scope of the present invention. Thus understood, the details of the circuit provided, including the ratings of the electrical components in the specific preferred embodiments, are not intended to limit the scope of any claim, nor to be read into any claim, but merely to provide an example of a fully enabled and disclosed best mode of practicing a preferred embodiment of the invention. 
         [0025]      FIG. 1  illustrates a preferred embodiment of the basic electrical components of the amplifier of the present invention. As seen in  FIG. 1 , an AC power supply  5  is coupled to an optional AC power circuit (transformer)  7  by an electrical connection  50 . Optional AC power circuit  7  is coupled to a bridge rectifier  10  by an electrical connection  51 . Bridge rectifier  10  is coupled to a voltage divider  15  by an electrical connection  55 . Bridge rectifier  10  is also coupled to a power device transistor  30  by an electrical connection  60 . 
         [0026]    Voltage divider  15  is coupled to a first input  21  of a first voltage multiplier  20  by an electrical connection  65  and to a second input  22  by an electrical connection  66 . The output of first voltage multiplier  20  is coupled to a first input  24  of a second voltage multiplier  23  by an electrical connection  67 . A triangular wave generator  27  is coupled to a second input  26  of second voltage multiplier  23  by electrical connection  68 . First voltage multiplier  20  and second voltage multiplier  23  comprise a triangular wave modulator (TWM)  91 . 
         [0027]    The output of second voltage multiplier  23  is coupled to a first input  28  of an internal comparator  25  by an electrical connection  70 . In a preferred embodiment, an audio signal source  35  is coupled to a second input  29  of an internal comparator  25  by an electrical connection  80 . The output of internal comparator  25  is coupled to a power device transistor  30  by an electrical connection  75 . In the preferred embodiment, internal comparator  25  is internal of a pulse width modulation controller integrated circuit (PWM controller  93 ) that includes triangular wave generator  27 , as described in detail below. Power device transistor  30  is coupled to a filter  40  by an electrical connection  85 . Filter  40  is coupled to a load device  45  by an electrical connection  90 . 
         [0028]    In operation, unregulated AC power supply  5  supplies an unregulated, AC power signal to the amplifier. The unregulated AC power signal passes through bridge rectifier  10 , which rectifies, or converts, the unregulated AC power signal into an unregulated DC power signal. This unregulated DC power signal is used to provide a reference voltage to triangle wave modulator  91  as well as being used by power device transistors  30  to power load device  45 . 
         [0029]    From bridge rectifier  10 , the unregulated DC power signal passes through voltage divider  15 . Voltage divider  15  establishes a unity voltage level and provides two input power signals comprising the voltage variance of the power signal into first voltage multiplier  20 . First voltage multiplier  20  multiplies these two signals together, providing an unregulated DC power signal equal to the square of the voltage variance. 
         [0030]    The output of first voltage multiplier  20  is coupled to first input  24  of second voltage multiplier  23 . Triangular wave generator  27  generates a triangular wave signal that is coupled to second input  26  of second voltage multiplier  23 . These two signals are multiplied together by second voltage multiplier  23  to generate a modulated triangular wave signal. 
         [0031]    The modulated triangular wave signal, output from triangular wave modulator  91 , is the first input to PWM Amp  25 . The second input to PWM Amp  25  is the audio signal being amplified, from audio source  35 . PWM Amp  25  compares the modulated triangular wave signal and the audio signal to generate a pulse width modulation (PWM) power signal carrying the audio component. The PWM power signal then passes to power device transistors  30 , which amplify the PWM power signal. This amplified PWM power signal then passes through filter  40  (e.g., an inductance capacitor filter) which filters out the high-frequency carrier component of the PWM power signal. This filtered PWM power signal provides a clean, undistorted audio signal free of noise to load device  45  because the modulated triangle wave signal compensates for variances in AC power supply  5 , powering the load device  45  for the relevant application. 
         [0032]      FIG. 2  illustrates a preferred embodiment for the AC power circuit ( 7  in  FIG. 1 ) of the present invention. In this embodiment, the AC power circuit uses a triac  150  and optocoupler  140  to delay the onset of AC power in the amplifier. This time delay power-on circuit delays the onset of AC power to allow the control circuit to stabilize and avoid loud pops when switched on. 
         [0033]    In the circuit, AC power from an outside AC power source (e.g., wall outlet, generator, etc.) is provided through an electrical pole  101  and an electrical pole  103 . Electrical poles  101  and  103  are coupled respectively by an electrical connection  102  and an electrical connection  104  in a parallel electrical circuit with a two-pole circuit breaker  105 . Electrical connection  102  is coupled from circuit breaker  105  to a transformer  110  (e.g., 12-volt transformer). Electrical connection  104  is also coupled from circuit breaker  105  to transformer  110 . 
         [0034]    Transformer  110  steps down the supply voltage (e.g., from 120-volts AC to 12-volts AC). Current flows from transformer  110  through two electrical connections  111  and  113  to a bridge rectifier  112 . The output from bridge rectifier  112  passes through electrical connections  116  and  114  to a filter network  115 . In a specific preferred embodiment, filter network  115  comprises a 2200 μF capacitor  117 , a 100 μF capacitor  118 , and a 0.1 μF capacitor  119  coupled in parallel with bridge rectifier  112  by electrical connections  116  and  114 . 
         [0035]    An electrical connection  121  couples a power supply regulator  120  to electrical connection  116 . In a specific preferred embodiment, power supply regulator  120  is of the type comparable to a Motorola 78L12. Power supply regulator  120  is coupled to an electrical ground  108  by an electrical connection  123 . A capacitor  124  and a capacitor  126  are coupled to power supply regulator  120  by an electrical connection  122 . The two capacitors  124  and  126  are also coupled together by electrical connection  114 . 
         [0036]    An electrical connection  127  couples a resistor  128  to a terminal V 12    125 . Terminal V 12    125  represents a source of direct current (DC) power supplied for the circuit. In the preferred embodiment disclosed, the voltage supplied is for a 12-volt circuit. Also in the preferred embodiment disclosed, resistor  128  is a 68K-ohm resistor. A resistor  129  is coupled to electrical connection  127  by an electrical connection  130  in a parallel electric circuit configuration. 
         [0037]    As stated, terminal V 12    125  is coupled to electrical connection  127 , and this electric terminal V 12    125  provides a DC power source (e.g., 12-volt). Resistor  128  and resistor  129  are both coupled to the DC power source. Resistor  128  is coupled in series with another resistor  131  by electrical connection  133 . In a specific preferred embodiment, resistor  131  is a 68K-ohm resistor. Resistor  129  is coupled in series with a capacitor  132  by an electrical connection  134 . Resistor  131  is coupled to an electrical ground  108  by an electrical connection  136 , and capacitor  132  is coupled to an electrical ground  108  by an electrical connection  137 . 
         [0038]    A comparator  135  is coupled to electrical connections  133  and  134 . The non-inverting input to comparator  135  is coupled to electrical connection  134  by an electrical connection  139 . The inverting input of comparator  135  is coupled to electrical connection  133  by an electrical connection  141 . Comparator  135  compares the input voltages of the two electrical connections. If the voltage at electrical connection  139  is less than the voltage at electrical connection  141 , the output of comparator  135  will be low, with the voltage at the output at an electrical connection  142  at the lowest possible value (e.g., digital output=0). If the voltage at electrical connection  139  is greater than the voltage at electrical connection  141 , the output of comparator  135  will be high, with the voltage at the output at electrical connection  142  at its highest value (e.g., digital output=1). 
         [0039]    An optocoupler  140  is comprised of a light emitting diode (LED)  171  and a phototransistor  172  inside a component case. Light emitting diode  171  emits light when the digital output value from comparator  135  equals 1 (e.g., the voltage at electrical connection  139  is greater than that at electrical connection  141 ). An electrical connection  143  couples a resistor  144  to the LED  171 . An electrical connection  146  couples resistor  144  to ground  108 . In a specific preferred embodiment, resistor  144  is a 560K-ohm resistor. 
         [0040]    Phototransistor  172  has a light sensitive base region. When light strikes the photosensitive base of phototransistor  172 , the emitter-to-collector resistance falls, allowing current to flow through phototransistor  172 . When the digital output value from comparator  135  equals 1 (logic 1 state), LED  171  is illuminated. Light from LED  171  charges the base of phototransistor  172 , permitting current flow through phototransistor  172 . Thus, optocoupler  140  functions as a switch triggered by the output of comparator  135 . 
         [0041]    An electrical connection  152  couples circuit breaker  105  and the AC power to a capacitor  157 , a triode alternating current switch (triac)  150 , and a resistor  145 . Resistor  145  is coupled to optocoupler  140  by an electrical connection  147 . An electrical connection  149  further couples electrical connection  147  to the gate of triac  150 . Triac  150  is coupled to a terminal L 2    165  and optocoupler  140  by an electrical connection  151 . Capacitor  157  is coupled to a resistor  155  by an electrical connection  156 , and resistor  155  is further coupled to terminal L 2    165  by an electrical connection  153 . Terminal L 1    160  is coupled to transformer  110  and breaker  105  by electrical connection  107 . 
         [0042]    Optocoupler  140  isolates triac  150  from the control circuit. When phototransistor  172  is activated by LED  171 , voltage applied to the gate of triac  150  causes current to flow through triac  150  and energize terminal L 2    165 . Once the gate activates triac  150 , AC power will continue to terminal L 2    165  and L 1    160  as long as the circuit remains energized. The optocoupler  140  and triac  150  combination will delay circuit power-up until the control circuit stabilizes, avoiding pops and hiss from the audio output. 
         [0043]      FIG. 3  illustrates a preferred embodiment of a bridge rectifier  205  ( 10  in  FIG. 1 ) and a voltage divider (resistors  210 ,  215 , and their electrical interconnection,  15  in  FIG. 1 ) of the present invention. A pair of terminals L 1    160  and L 2    165  are coupled to bridge rectifier  205  by electrical connections  201  and  202  respectively. Two electrical output connections from bridge rectifier  205  couple to a resistor-capacitor (RC) filter and resistor voltage divider network arrangement. An electrical connection  208  couples bridge rectifier  205  to terminal V H    240 . Terminal V H    240  represents a high voltage terminal connection. An electrical connection  207  couples bridge rectifier  205  to an electrical connection  221 , and to an electrical connection  206 . Electrical connection  221  is coupled to ground  108 . An electrical connection  209  couples bridge rectifier  205  to a capacitor  230 . In a specific preferred embodiment, capacitor  230  is a 1000 μF capacitor. Electrical connection  206  couples capacitor  230  to electrical connection  207 . Electrical connection  209  is also coupled to electrical connection  208 . 
         [0044]    A resistor  210  and a resistor  215  are connected in series to each other and to capacitor  230  in a parallel circuit. An electrical connection  212  couples resistor  210  to electrical connection  208 . An electrical connection  211  further couples resistor  210  to resistor  215 . Electrical connection  221  couples resistor  215  to ground  108 . 
         [0045]    An electrical connection  213  couples resistors  210  and  215  to the non-inverting terminal of an operational amplifier  218  (op amp  218 ). An electrical connection  217  couples the output of op amp  218  to the inverting terminal input of op amp  218 . Thus configured op amp  218  performs as a voltage follower. An electrical connection  216  connects the output of op amp  218  (the voltage follower) to a terminal T 1    250 . The arrangement of the resistors  210  and  215  and the electrical connections  213  and  211  between resistors  210  and  215  comprises a resistor voltage divider network. One or both of resistors  210  and  215  may be variable, to accommodate adjustment of the power variance signal. 
         [0046]      FIG. 4  illustrates a preferred embodiment of the circuit for the triangular wave modulator ( 91  in  FIG. 1 ) of the present invention. Although the preferred embodiment shown in  FIG. 4  discloses a design for an analog circuit, the equivalent functionality may be achieved through digital circuitry, such as, for example, by use of digital signal processors. 
         [0047]    As seen in  FIG. 4 , a terminal T 1    250  is coupled to a first resistor  382  by an electrical connection  301 . Resistor  382  is subsequently coupled to a first voltage multiplier  310  ( 20  in  FIG. 1 ), an integrated circuit chip with a voltage multiplier circuit, by an electrical connection  383  to pin  1 . Terminal T 1    250  is coupled to a second resistor  381  by electrical connection  301  through an electrical connection  303 . Resistor  381  is subsequently coupled to first voltage multiplier  310  by an electrical connection  384  to pin  8 . Pin  7  of voltage multiplier  310  is coupled to a capacitor  305  (typically 0.1 μF) by an electrical connection  308 . Pin  2  of first voltage multiplier  310  is coupled to electrical connection  308  by an electrical connection  309 . 
         [0048]    Capacitor  305  is coupled to ground  108  by an electrical connection  306 . Terminal V G    302  is coupled to electrical connection  308  by an electrical connection  304 . Terminal V G    302  represents a virtual ground for supplying a ground reference to single power supply electrical components. Pin  5  of first voltage multiplier  310  is coupled to a resistor  315  by an electrical connection  312 , and resistor  315  is coupled to a terminal V 12    125  by an electrical connection  314 . In a specific preferred embodiment, resistor  315  is 60K-ohm resistor. Pin  6  of first voltage multiplier  310  is coupled to terminal V G    302  by electrical connection  377 . 
         [0049]    Pin  4  of first voltage multiplier  310  is coupled to the inverting input of an op amp  320  by an electrical connection  311 . A resistor  325  is coupled to the inverting input of op amp  320  by an electrical connection  317 , which is coupled to electrical connection  311 . An electrical connection  321  couples an RMS terminal  330  to the pin  8  input of a second voltage multiplier  340  ( 23   FIG. 1 ) through an electrical connection  336 . An electrical connection  324  couples resistor  325  to the output of op amp  320  through an electrical connection  327 . An electrical connection  326  couples a resistor  335  to electrical connection  324 . 
         [0050]    Electrical connection  336  couples resistor  335  to pin  8  of second voltage multiplier  340 . This signal input is the square of the variance of the input voltage to first voltage multiplier  310 . The signal from RMS terminal  330  is added to this signal. The second input is from a triangular wave generator through pin  1  of second voltage multiplier  340 . Pin  7  of second voltage multiplier  340  is coupled to an electrical connection  351  by electrical connection  341 . Pin  2  of second voltage multiplier  340  is coupled to electrical connection  341  by an electrical connection  343 . 
         [0051]    Pin  5  of second voltage multiplier  340  is coupled to a resistor  355  by an electrical connection  337 . Resistor  355  is further coupled to a terminal V 12    125  by an electrical connection  339 . In a specific preferred embodiment, resistor  355  is a 60K-ohm resistor. Pin  6  of second voltage multiplier  340  is connected to V G    302  by an electrical connection  379  which is coupled to electrical connection  351 . 
         [0052]    Pin  4  of second voltage multiplier  340  is the output of the two voltage multipliers. This output is connected to an inverter amplifier circuit, comprising an op amp  350  and resistor  358 . Pin  4  of second voltage multiplier  340  is coupled to the inverting input of op amp  350  by an electrical connection  344 . Electrical connection  356  couples resistor  358  to electrical connection  344 . The output of op amp  350  is coupled to electrical connection  357 , which couples resistor  358  to capacitor  360  by connection  352 . Capacitor  360  is coupled to terminal T 3    375  by electrical connection  361 . 
         [0053]    Pin  1  of second voltage multiplier  340  receives the input triangular wave signal. Terminal T 2    380  is coupled to a capacitor  365  by electrical connection  366 . In a specific preferred embodiment, capacitor  365  is a 0.047 μF capacitor. Capacitor  365  is coupled to the non-inverting input of a voltage follower op amp  370  by an electrical connection  371 . The output of op amp  370  is coupled to a resistor  345  by an electrical connection  346 . In a specific preferred embodiment, resistor  345  is a 10K-ohm resistor. Electrical connection  346  is coupled to the inverting input of voltage follower op amp  370  by an electrical connection  373 . Resistor  345  is coupled to pin  1  of second voltage multiplier  340  by an electrical connection  342 . 
         [0054]      FIG. 5  illustrates a preferred embodiment of the present invention for the pulse width modulation controller ( 93  in  FIG. 1 ) including its audio input circuitry, the triangular wave generator, and the pulse width modulation amplifier. The audio source signal input to the amplifier is through terminals T 4    401  and T 5    402 . Terminal T 4    401  is coupled to a capacitor  412  by an electrical connection  407 . In a specific preferred embodiment, capacitor  412  is a 22 μF capacitor. A resistor  405  is coupled to electrical connection  407  by an electrical connection  408 . In a specific preferred embodiment, resistor  405  is a 100K-ohm resistor. Resistor  405  is coupled to a terminal V G    302  by an electrical connection  409 , and terminal T 5    402  is coupled to electrical connection  409  by an electrical connection  404 . 
         [0055]    Capacitor  412  is coupled to a resistor  415  by an electrical connection  406 . In a specific preferred embodiment, resistor  415  is an 11K-ohm resistor. A capacitor  410  is coupled to electrical connection  406  by an electrical connection  403 . In a specific preferred embodiment, capacitor  410  is a 0.1 μF capacitor  410 . Resistor  415  is coupled to the non-inverting terminal of an op amp  416  by an electrical connection  414 . Capacitor  410  is connected in a parallel circuit to resistor  415  by an electrical connection  411  connected to electrical connection  414 . 
         [0056]    Op amp  416  is configured as a follower. Electrical connection  414  is coupled to the non-inverting input of op amp  416 . The output of the op amp  416  is coupled to a resistor  418  by an electrical connection  413 . In a specific preferred embodiment, resistor  418  is a 390-ohm resistor. An electrical connection  417  couples electrical connection  413  to the inverting input of op amp  416 , thus configuring op amp  416  as a voltage follower. Resistor  418  is coupled to a capacitor  420  by an electrical connection  419 . In a specific preferred embodiment, capacitor  420  is a 22 μF capacitor. Capacitor  420  is coupled to a pulse width modulation controller  430  ( 93  in  FIG. 1 ). 
         [0057]    In the preferred embodiment disclosed, PWM controller  430  is an integrated circuit chip, which provides the triangular wave generator and internal comparator circuit. An electrical connection  421  is connected to PIN  1  (AUDA) of PWM controller  430 . A terminal AA  425  is coupled to electrical connection  421  by an electrical connection  426 . Terminal AA  425  represents the audio input to the circuit. In the preferred embodiment, the audio input is buffered as shown by voltage follower  416 . A capacitor  423  is coupled to electrical connection  421  by an electrical connection  422 , and the capacitor  423  is coupled to ground  108  by an electrical connection  427 . In a specific preferred embodiment, capacitor  423  is a 6800-pF capacitor. 
         [0058]    An electrical connection  451  couples the audio input signal to an inverting amplifier  450 . Electrical connection  451  is coupled to a resistor  452 . An electrical connection  449  couples resistor  452  to the inverting input of op amp  450 . An electrical connection  467  couples electrical connection  449  to another resistor  448 . In a specific preferred embodiment, resistor  452  and resistor  448  are 22K-ohm resistors. 
         [0059]    A capacitor  456  is coupled to electrical connection  451  by an electrical connection  477 . Capacitor  456  is coupled to ground  108  by an electrical connection  457 . In a specific preferred embodiment, capacitor  456  is a 47-pF capacitor. A resistor  454  is coupled to electrical connection  477  by an electrical connection  453 , in a parallel circuit arrangement with capacitor  456 . An electrical connection  459  couples resistor  454  to connection  458 , thence to Terminal V G    302 . 
         [0060]    Terminal V G    302  is coupled to electrical connection  459  by an electrical connection  458 . An electrical connection  461  couples electrical connection  459  to the non-inverting input of op amp  450 . A capacitor  462  is coupled to electrical connection  461  by an electrical connection  469 , and electrical connection  493  couples capacitor  462  to electrical connection  495  and ground  108 . 
         [0061]    The output of the op amp  450  is coupled to a resistor  445  by an electrical connection  471 . In a specific preferred embodiment, resistor  445  is a 390-ohm resistor. Resistor  445  is coupled to a capacitor  443  by an electrical connection  444 . In a specific preferred embodiment, capacitor  443  is a 22-μF capacitor. An electrical connection  479  couples capacitor  443  to pin  8 , the Audio B (AUD B) input, on controller  430 . An electrical connection  481  couples electrical connection  479  to a capacitor  440 , and electrical connection  497  couples capacitor  440  to ground  108 . In a specific preferred embodiment, capacitor  440  is a 6800-pF capacitor 6800. 
         [0062]    In a specific preferred embodiment, pulse width modulation controller  430  is a Zetex ZXCD 1000, the internal configuration of which is illustrated in  FIG. 9 . In this embodiment, electrical connection  421  is coupled to pin  1  of PWM controller  430 . Pin  1  is the Audio A (AUD A) input, which is the non-inverting input to the first internal comparator on controller  430 . The Audio B (AUD B) input, pin  8 , is coupled to op amp  450  by electrical connection  479 . AUD B is the non-inverting input to the second internal comparator on controller  430 . A terminal T 3    375 , the output from second voltage multiplier  340 , is coupled to the Triangle B (TRI B) input, pin  7 , of PWM controller  430  by electrical connection  489 . Electrical connection  429  couples electrical connection  489 , and terminal T 3    375 , to Triangle A (TRI A) input, pin  2  of PWM controller  430 . 
         [0063]    PWM controller  430  includes two internal comparators (see  FIG. 9 ). The AUD A input, pin  1  of PWM controller  430 , is coupled to the non-inverting input of the first internal comparator, and the TRI A input, pin  2  of PWM controller  430 , is the inverting input of the first internal comparator. The Output A (OUT A), pin  15  of PWM controller  430 , is the output signal from the first internal comparator and is coupled to terminal T 6    498  by an electrical connection  463 . The AUD B input, pin  8  on PWM controller  430 , is the non-inverting input of the second internal comparator, and the TRI B input, pin  7  of PWM controller  430 , is the inverting input of the second internal comparator. The Output B (OUT B), pin  10  of PWM controller  430 , is the output signal from the second internal comparator and is coupled to terminal T 7    499  by an electrical connection  486 . 
         [0064]    PWM controller  430  also generates the triangular wave signal input to second voltage multiplier  340 . OSC A generates a triangular wave signal. The OSC A output, pin  3 , is coupled to terminal T 2    380  by electrical connection  431 . Referring back to  FIG. 4 , it is seen that the triangular wave signal at terminal T 2    380  subsequently passes through capacitor  365 , follower  370 , and resistor  345 , to the pin  1  input of second voltage multiplier  340 . Referring again to  FIG. 5 , pin  5  of PWM controller  430 , COSC, is coupled to a capacitor  437  by electrical connection  432 , and capacitor  437  is coupled to ground  108  by electrical connection  439 . In a specific preferred embodiment, capacitor  437  is a 330-μF capacitor. Pin  9  of PWM controller  430 , GND, is coupled to ground  108  by electrical connection  479 . Pin  11  of PWM controller  430 , GND 2 , is coupled to electrical connection  479  and ground  108  by an electrical connection  496 . 
         [0065]    Pin  12  of PWM controller  430 ,  9 VB, is connected to an internal power supply of PWM controller  430  (typically 9-volt), and is coupled by an electrical connection  472  to three capacitors  470 ,  474 , and  480 , which are individually connected in a bridge, or parallel arrangement to electrical connection  479 . Pin  14  of the PWM controller  430 ,  9 VA, is connected to the internal power supply of PWM controller  430  (typically 9-volt), and is coupled by an electrical connection  469  to electrical connection  472  and the three capacitors  470 ,  474 , and  480 . Pin  16  of the PWM controller  430 ,  5 V 5 , is connected to an internal power supply of PWM controller  430  (typically 5.5-volt), and is coupled to a capacitor  435  by an electrical connection  461 . Capacitor  435  is coupled to ground  108  by an electrical connection  443 . An electrical connection  439  couples a capacitor  434  to electrical connection  461  and to  5 V 5 . An electrical connection  441  couples capacitor  434  to ground  108 . 
         [0066]    Pin  13 , V CC , receives the external power supply to PWM controller  430 . Pin  13 , V CC  is coupled to the power supply terminal V 12    125  (12-volt in the specific preferred embodiment), by electrical connection  468 , and is coupled by three capacitors  473 ,  475 , and  478  in a bridge, or parallel circuit arrangement, to electrical connection  479  and ground  108 . The external power supply V CC  supplies power to PWM controller  430 , and regulators on PWM controller  430  drop the power to the internal power sources (typically 9-volt and 5.5-volt) required by the internal circuitry of PWM controller  430 . 
         [0067]      FIG. 6  illustrates a preferred embodiment for the power device transistor and filter ( 30  in  FIG. 1 ) of the present invention. A terminal T 6    498  is coupled by an electrical connection  501  to an electrical connection  503 . Electrical connection  503  couples a capacitor  521  to a capacitor  505  in series. An electrical connection  527  couples capacitor  521  to the anode of diode  530 . An electrical connection  529  couples the cathode of diode  530  to a terminal V H    213 . An electrical connection  533  couples a resistor  534  to electrical connection  529  and to the cathode of diode  530  in a parallel circuit. An electrical connection  531  couples electrical connection  527  and an electrical connection  532  to resistor  536 . An electrical connection  535  couples electrical connection  531  to the anode of a diode  537  in a parallel circuit to a resistor  536 . Cathode of diode  537  is coupled to electrical connection  539  by an electrical connection  538 . 
         [0068]    An electrical connection  545  couples a capacitor  546  to electrical connection  529  and terminal V H    213  and the cathode of diode  530 . In a specific preferred embodiment, capacitor  546  is a 0.47-μF capacitor. An electrical connection  548  couples capacitor  546  to ground  108 . 
         [0069]    Electrical connection  539  couples resistor  536  and electrical connection  538  to the gate of a P-channel metal-oxide-semi-conductor field-effect transistor (MOSFET)  540 . The source of MOSFET  540  is coupled to electrical connection  529  by an electrical connection  541 . The drain of MOSFET  540  is connected to an electrical connection  520  by an electrical connection  542 . 
         [0070]    Capacitor  505  is coupled to the cathode of a diode  510  by an electrical connection  504 . An electrical connection  508  couples electrical connection  504  to a resistor  513 . An electrical connection  502  couples electrical connection  508  to a resistor  511  in a parallel circuit to diode  510 . An electrical connection  509  couples resistor  511  to an electrical connection  507 . An electrical connection  512  couples the cathode of a diode  514  to electrical connection  502  in a parallel circuit to resistor  513 . An electrical connection  515  couples the anode of diode  514  to an electrical connection  516 , which is coupled to resistor  513 . 
         [0071]    Electrical connection  516  couples resistor  513  and the anode of diode  514  to the gate of an N-channel MOSFET  517 . The source of MOSFET  517  is coupled to electrical connection  507  by electrical connection  519 , and electrical connection  519  is coupled to electrical connection  548  and ground  108  by electrical connection  507 . The drain of MOSFET  517  is coupled to electrical connection  520  by an electrical connection  518 . Electrical connection  520  is coupled to a inductor  543 . Inductor  543  is coupled to the first output terminal OUT 1    601  of the amplifier by an electrical connection  544 . In a specific preferred embodiment, inductor  543  is a 20-μH inductor. Electrical connection  528  couples a capacitor  547  to electrical connection  520  and inductor  543 . An electrical connection  549  couples capacitor  547  to ground  108 . In a specific preferred embodiment, capacitor  547  is a 1-μF capacitor. The combination of inductor  543  and capacitor  547  forms an LC filter configuration for the signal output at OUT 1    601 . 
         [0072]    A terminal T 9    499  is coupled by an electrical connection  551  to an electrical connection  553 . Electrical connection  553  couples a capacitor  571  and a capacitor  555  together in series. An electrical connection  577  couples capacitor  571  to the anode of a diode  580 . An electrical connection  579  couples the cathode of diode  580  to a terminal V H    214 . An electrical connection  583  couples a resistor  584  to an electrical connection  579  and the cathode of diode  580  in a parallel circuit. An electrical connection  581  also couples electrical connection  577  and an electrical connection  582  to a resistor  586 . An electrical connection  585  couples electrical connection  581  to the anode of a diode  587  in a parallel circuit to resistor  586 . The cathode of diode  587  is coupled to an electrical connection  589  by an electrical connection  588 . 
         [0073]    An electrical connection  595  couples a capacitor  596  to electrical connection  579  and terminal V H    214  and the cathode of diode  580 . In a specific preferred embodiment, capacitor  596  is a 0.47-μF capacitor. Electrical connection  598  couples capacitor  596  to ground  108 . 
         [0074]    An electrical connection  589  couples resistor  586  and an electrical connection  588  to the gate of a P-channel MOSFET  590 . The source of MOSFET  590  is coupled to an electrical connection  579  by an electrical connection  591 . The drain of MOSFET  590  is connected to an electrical connection  570  by an electrical connection  592 . 
         [0075]    Capacitor  555  is coupled to the cathode of a diode  560  by an electrical connection  554 . An electrical connection  558  couples electrical connection  554  to a resistor  563 . An electrical connection  552  couples electrical connection  558  to a resistor  561  in a parallel circuit to diode  560 . An electrical connection  559  couples resistor  561  to an electrical connection  557 . An electrical connection  562  couples the cathode of a diode  564  to electrical connection  552  in a parallel circuit to resistor  563 . An electrical connection  565  couples the anode of diode  564  to an electrical connection  566 , which is coupled to resistor  563 . 
         [0076]    Electrical connection  566  couples resistor  563  and the anode of diode  514  to the gate of an N-channel MOSFET  567 . The source of MOSFET  567  is coupled to electrical connection  557  by an electrical connection  569 , and electrical connection  569  is coupled to an electrical connection  598  and ground  108  by electrical connection  557 . The drain of MOSFET  567  is coupled to electrical connection  570  by an electrical connection  568 . Electrical connection  570  is coupled to an inductor  593 . Inductor  593  is coupled to the second output terminal OUT 2    602  of the amplifier by an electrical connection  594 . In a specific preferred embodiment, inductor  593  is a 20-μH inductor. An electrical connection  578  couples a capacitor  597  to electrical connection  570  and inductor  593 . Electrical connection  599  couples capacitor  597  to ground  108 . In a specific preferred embodiment, capacitor  597  is a 1-μF capacitor. The combination of inductor  593  and capacitor  597  forms an LC filter configuration for the signal output at OUT 2    602 . A load device (not shown), typically a speaker in audio applications, is connected to each of the outputs OUT 1    601  and OUT 2    602 . 
         [0077]      FIG. 7  illustrates an alternative preferred embodiment in which a dynamic range compression component is added to the circuit. In this embodiment, an RMS-to-DC converter integrated circuit  605  (RMS converter  605 ) provides modulation to compensate for volume changes in the input signal (e.g., dynamic range compression). The triangular wave, in addition to being modulated to compensate for power variances, is further modulated with the output of the RMS (root-mean-square) converter  605 . The RMS converter  605  generates a signal relative to the RMS value of the audio input at AA  425  to obtain variable compression of the audio level. In a specific preferred embodiment, RMS converter  605  is an Analog Devices AD 736 RMS-to-DC converter integrated circuit. Pin  1  of RMS converter  605  is coupled to a capacitor  610  by an electrical connection  609 . In a specific preferred embodiment, capacitor  610  is a 10-μF capacitor. Electrical connection  641  couples a terminal V G    302  to capacitor  610 . An electrical connection  608  couples pin  8  of RMS converter  605  to electrical connection  641  and terminal V G    302 . Pin  2  of RMS converter  605  is coupled to terminal AA  425  by an electrical connection  603  and is the input into RMS converter  605 . 
         [0078]    Pin  3  of RMS converter  605  is coupled to a capacitor  625  by an electrical connection  604 . In a specific preferred embodiment, capacitor  625  is a 47-μF capacitor. The output of RMS converter  605  at pin  6  is coupled to a potentiometer  650  by electrical connection  616 . Potentiometer  650  permits selectable, adjustable compression of the triangular wave modulated circuit. The wiper leading from potentiometer  650  is coupled to a resistor  645 . Resistor  645  is coupled to an RMS terminal  330  by an electrical connection  647 . In a specific preferred embodiment, resistor  645  is a 10K-ohm resistor. An electrical connection  652  couples potentiometer  650  to a terminal V G    302 . Electrical connection  616  from the output pin  6  of converter  605  is coupled to capacitor  625  by electrical connection  617 . 
         [0079]    Pin  4  of converter  605  is coupled to an electrical ground  108  by an electrical connection  607 . An electrical connection  613  couples a capacitor  615  to electrical connection  607 . In a specific preferred embodiment, capacitor  615  is a 0.1-μF capacitor. An electrical connection  616  couples capacitor  615  to a terminal V G    302 . An electrical connection  611  couples electrical connection  607  to a capacitor  620 , and electrical connection  612  couples capacitor  620  to pin  5  of the converter  605 . In a specific preferred embodiment, capacitor  620  is a 100-μF capacitor. 
         [0080]    Pin  7  of converter  605  is coupled to a terminal V 12    125  by an electrical connection  618 . An electrical connection  639  couples electrical connection  641 , and terminal V G    302 , to a capacitor  640 . An electrical connection  634  couples capacitor  640  to electrical connection  618  and the terminal V 12    125 . In a specific preferred embodiment, capacitor  640  is a 0.1-μF capacitor. 
         [0081]      FIG. 8  illustrates the connectivity between the various circuit components described in detail hereinabove, showing the relationship between the rectifier and divider circuit of  FIG. 3 , the triangle wave modulator of  FIG. 4 , the pulse width modulator of  FIG. 5 , and the power device of  FIG. 6 , as might be implemented in a production circuit board. 
         [0082]      FIG. 9  illustrates the internal operative connectivity for pulse width modulation controller  430  described in the preferred embodiment in detail in connection with  FIG. 5 . 
       OPERATION OF THE PREFERRED EMBODIMENTS 
       [0083]      FIG. 10  illustrates in schematic, block diagram form, the modulated triangular wave amplifier as similarly illustrated in  FIG. 1 , according to a preferred embodiment of the present invention. In  FIG. 10 , the device is configured as a noise-canceling amplifier, which is capable of removing or canceling “ripple” from a power supply. Power is supplied to rectifier  10 . A signal (such as an audio signal) to be amplified may be provided to an optional pre-amplifier  1011  to boost the signal strength. The amplified signal is then input to PWM controller  93 , while rectified power (DC) is input to TWM  91 . 
         [0084]    A triangle (Δ) wave generated by triangle wave generator  91  ( 27  in  FIG. 1 , and described in detail in connection with  FIG. 4 ) is coupled from PWM controller  93  and is modulated by TWM  91  and returned to PWM controller  93 . The output of PWM controller  93  is input to power device  30 , which also receives rectified power from rectifier  10 . Thus, the output of PWM controller  93  is employed to cancel noise present in the rectified power signal. The output of power device  30  is typically applied to a filter  40  and then to a load  45 , such as an audio speaker. 
         [0085]      FIG. 11  illustrates in schematic, block diagram form the modulated triangular wave amplifier according to another preferred embodiment of the present invention. In this preferred embodiment, the device is configured to modify the dynamic range of an input signal (i.e., to limit or enhance bandwidth, equalize the signal, or to compensate for, or cancel, signal elements). In this embodiment, power is supplied to rectifier  10 , while a signal (such as an audio signal) to be modified may be provided to an optional pre-amplifier  1011  to boost the signal strength. Rectified power (DC) is input to TWM  91 . The amplified signal is input to a Signal Processor  1013  coupled between the output of pre-amplifier  1011  and TWM  91 . The amplified signal is also input, without signal processing, to PWM controller  93 . 
         [0086]    The choice of signal processor  1013  “type” corresponds with the desired modification to the signal. Thus, the output of PWM controller  93 , with the addition of signal processing through TWM  91 , is used in power device  30  to accomplish the desired modification to the input signal, while power-supply noise-cancellation is also achieved. This configuration is most effectively adapted for audio input signals with an audio speaker load  45 . 
         [0087]      FIG. 12  illustrates in schematic block diagram form, the triangular wave modulated amplifier, according to another preferred embodiment of the present invention. In this preferred embodiment, the device is configured to introduce an overlay or cancellation signal (pink noise, an advertisement, compensation for ambient noise, etc.) onto the output signal to load  45 . 
         [0088]    The overall configuration is identical to that in  FIG. 11 , with an additional signal source  1015  supplied to signal processor  1013 . The signal processor  1013  then supplies the processed signal to TWM  91 , which in turn affects the desired modification to the output signal of PWM controller  93 . By this configuration, an overlay or background noise compensation signal may be added while power supply noise-cancellation is also provided. 
         [0089]    In each of the embodiments of the present invention disclosed in  FIG. 10 ,  FIG. 11 , and  FIG. 12 , it is understood that unregulated DC power may be supplied directly TWM  91 , if DC power, rather than AC power, is the available power source. 
         [0090]    While the invention has been particularly shown and described with respect to preferred embodiments, it will be readily understood that minor changes in the details of the invention may be made without departing from the spirit of the invention.