Class-D amplifier having high order loop filtering

• US 20060044057A1
• Filed: 08/26/2004
• Published: 03/02/2006
• Est. Priority Date: 08/26/2004
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Haroun, Baher, Hezar, Rahmi, Ramaswamy, Srinath, Forejt, Brett
• Application Number:
  US10/928,528
• Publication Number:
  US 20060044057A1
• Time in Patent Office: Days
• US Class Current: 330/10
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 2200/331 Sigma delta modulation being used in an amplifying circuit
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers
• CPC Class Codes: H03F 3/2173 of the bridge type

Abstract

An amplifier having an active and passive gain stage connect to a load for driving a load according to a system analog input. A first embodiment of the amplifier in accordance with the present invention includes a logic network connected between a comparator network and a switching system, wherein the comparator network connects to the passive gain stage. Specifically, the active gain stage may include an active filter connected to receive an analog or digital input and provide a difference between the analog or digital input and the feedback signal relative to the gain factor of a gain unit connected to the active filter. The passive gain stage includes a passive filter. The logic network generates at least one switching signal which controls the switching system that includes at least one switching device to selectively provide power to the load. An output signal from the switching system provides output for the amplifier and is fed back to the active gain stage. In another embodiment, the output is a two-level signal and the passive and active filters are second order low pass filters, where the gain factor is about 25 or more. In yet another embodiment, the gain factor is approximately 250. Moreover, the amplifier may include a digital delta-sigma modulator connected to supply a two level input.

Claims

3-1. The amplifier of claim 1, wherein the comparator network comprises:

a ramp signal generator to produce a ramp signal;

a first comparator coupled to receive the ramp signal and the passive filter output signal to provide a difference between the ramp signal and the passive filter output signal in a first comparator network output signal;

a multiplier coupled to receive the passive filter output signal to generate an inverted passive filter output signal; and

a second comparator coupled to receive the ramp signal and the inverted passive filter output signal to provide a difference between the ramp signal and the inverted passive filter output signal in a second comparator network output signal.