Class d switching audio amplifier

A method of modulating a Class D switching amplifier, wherein the Class D switching amplifier includes an H-bridge output stage having a first half and a second half, the method comprising the steps of:

• (a) generating a triangle waveform for use as a first reference signal;
• (b) inverting the triangle waveform to produce a second reference signal;
• (c) comparing an audio input signal with a feedback signal, with the result of the comparison being an error signal
• (d) comparing the first reference signal to the error signal, with the result of the comparison being a first pulse width modulated signal;
• (e) comparing the second reference signal to the error signal, with the result of the comparison being a second pulse width modulated signal;
• (f) inverting the first pulse width modulated signal to produce a third pulse width modulated signal;
• (g) inverting the second pulse width modulated signal to produce a fourth pulse width modulated signal;
• (h) using the first pulse width modulated signal and the third pulse width modulated signal to drive the first half of the H-bridge;
• and
• (i) using the second pulse width modulated signal and the fourth pulse width modulated signal to drive the second half of the H-bridge.

A method of providing an isolated feedback signal within a Class-D switching amplifier, wherein the Class D switching amplifier includes an H-bridge output stage having a first pulse width modulated output signal and a second pulse width modulated output signal, the method comprising the steps of:

• (a) driving a first isolator with the first pulse width modulated output to produce a first isolator output signal;
• (b) driving a second isolator with the second pulse width modulated output to produce a second isolator output signal;
• (c) low pass filtering the first isolator output to produce a first isolated feedback signal;
• (d) low pass filtering the second isolator output to produce a second isolated feedback signal;
• and
• (e) combining the first isolated feedback signal with and the second isolated feedback signal to produce a single-ended isolated feedback signal.

A method of providing an isolated feedback signal within a Class-D switching amplifier, wherein the Class D switching amplifier includes an H-bridge output stage having a first pulse width modulated output signal and a second pulse width modulated output signal, the method comprising the steps of:

• (a) low pass filtering the first pulse width modulated signal to produce a first feedback signal;
• (b) low pass filtering the second pulse width modulated signal to produce a second feedback signal;
• (c) differentially driving a small signal transformer with the first feedback signal and the second feedback signal to produce a first isolated feedback signal and a second isolated feedback signal;
• and
• (d) combining the first isolated feedback signal with and the second isolated feedback signal to produce a single-ended isolated feedback signal.

A circuit topology for generating an ultra-low noise triangle waveform for use in a Class D switching amplifier, the circuit topology comprising:

• an ultra-low noise voltage regulator operable to reduce high frequency noise;
• a switched current source IC operable to provide a switched current capacitive charging circuit
• a low ESR capacitor interposed between the ultra-low noise voltage regulator and a circuit ground operable to provide a low impedance path to ground;
• and
• a ramp capacitor interposed between the ultra-low noise voltage regulator and the switched current source and operable to charge and discharge in a ramp-like manner, thereby providing a triangular shape to the low noise triangle waveform,
• wherein the ultra-low noise triangle waveform is taken from a terminal of the ramp capacitor.

A Class D switching amplifier comprising:

• a power supply circuit board operable to perform AC voltage regulation and to generate a power signal;
• and
• an amplifier circuit board presenting a topside and a bottomside and connected to the power supply board by a copper bus bar and one or more standoffs, and operable to receive the power signal, the amplifier circuit board including—
• a first half H-bridge including a first FET driver circuit electrically connected to and driving a first MOSFET and a second MOSFET, and
• a second half H-bridge including a second FET driver circuit electrically connected to and driving a third MOSFET and a fourth MOSFET,
• wherein the first half H-bridge is arranged upon the amplifier circuit board so as to be parallel with the second half H-bridge, and the first FET driver circuit is mounted on the bottomside of the amplifier circuit board while the second FET driver circuit is mounted on the topside of the amplifier circuit board.