US4178556A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Class D amplifier system
Assignee: Individual
•
Filing: 1978-04-19
•
Granted: 1979-12-11
•
Expires: 1998-04-19
Abstract
Abstract In a Class D amplifier system comprising a pulse width modulator for pulse width modulating with an audio signal a carrier signal having a frequency higher than that of the audio signal, an output switching amplifier connected to the modulator, and a lowpass filter connected to the output amplifier to supply a demodulated audio signal to a load in which a trap circuit resonant at a carrier signal frequency is provided in the lowpass filter to permit part of an output signal from the trap circuit which is free from a carrier signal component to be negative-fed back to the pulse width modulator.
Inventors
- 👤 Brian E. Attwood
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:04
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/20; H03F3/21; H03F3/217
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
146 words
A Class D amplifier system comprising: an audio amplifier for amplifying an audio signal; a carrier signal source; a pulse width modulator for pulse width modulating a carrier signal from said carrier signal source by an output signal of said audio amplifier; means connecting the output of said audio amplifier and the output of said carrier signal source to said pulse width modulator as inputs; an output amplifier having an input connected to the output of said pulse width modulator for amplifying a pulse width modulated signal; a low pass filter having an input connected to the output of said output amplifier to apply a recovered audio signal to a load; a trap circuit arranged in said lowpass filter to resonate at a carrier signal frequency; and negative feed-back circuit means connecting an output voltage from said trap circuit as input to said pulse width modulator.
Claim 2
Dependent Claim
146 words
A Class D amplifier system comprising: an audio amplifier for amplifying an audio signal; a carrier signal source; a pulse width modulator for pulse width modulating a carrier signal from said carrier signal source by an output signal of said audio amplifier; means connecting the output of said audio amplifier and the output of said carrier signal source to said pulse width modulator as inputs; an output amplifier having an input connected to the output of said pulse width modulator for amplifying a pulse width modulated signal; a low pass filter having an input connected to the output of said output amplifier to apply a recovered audio signal to a load; a trap circuit arranged in said lowpass filter to resonate at a carrier signal frequency; and negative feed-back circuit means connecting an output voltage from said trap circuit as input to said pulse width modulator.
Claim 3
Dependent Claim
21 words
A Class D amplifier system according to claim 1, in which said carrier signal source is comprised of a crystal oscillator.
Claim 4
Dependent Claim
38 words
A Class D amplifier system according to claim 1, in which said trap circuit is a parallel resonance circuit comprising a coil and a capacitor which is connected between the output of said output amplifier and said load.
Claim 5
Dependent Claim
34 words
A Class D amplifier system according to claim 1, further comprising a series resonance circuit connected between the output of said lowpass filter and ground and adapted to resonate at the carrier signal frequency.
References Cited (Backward Citations)
US4059807A
Cited
US4021745A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-12-10 | 1983-06-11 | 1983-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-12-10 | 1987-06-11 | 1987-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-12-10 | 1991-06-11 | 1991-12-11 | $7700.00 | Window Closed / Lapsed |