Class D amplifier

• US 20050231281A1
• Filed: 06/20/2005
• Published: 10/20/2005
• Est. Priority Date: 10/03/2002
• Status: Active Grant

• Current Assignee: Kenichi Taura, Masayuki Ishida, Masayuki Tsuji, Tsuyoshi Nakada
• Original Assignee: Kenichi Taura, Masayuki Ishida, Masayuki Tsuji, Tsuyoshi Nakada
• Inventors: Taura, Kenichi, Nakada, Tsuyoshi, Tsuji, Masayuki, Ishida, Masayuki
• Granted Patent: US 7,057,456 B2
• Time in Patent Office: Days
• US Class Current: 330/251
• 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

Abstract

A pulse modulated signal (ei) output from a pulse modulator (1) and a feedback signal (ef) containing distortion caused by a power switch (3) are integrated in a first integrator (21) and a second integrator (24), respectively, and are input to input terminals of a comparator (25 or 29), respectively, so that a correction signal (Vc) is generated.

Claims

1. A class D amplifier comprising:

a power switch for switching on/off a power supply supplying a supply voltage in response to a pulse width modulated signal;

a correction circuit for correcting a pulse width of said pulse width modulated signal to be input to said power switch in accordance with an amplitude of a feedback signal generated from an output of said power switch; and

an arithmetic unit for adjusting said amplitude of said feedback signal to be input to said correction circuit in accordance with a value of said supply voltage.

2. The class D amplifier according to claim 1, wherein

said arithmetic unit includes:

a subtracter for subtracting a reference voltage generated on the basis of a dc component of said supply voltage from said feedback signal; and

an adder for adding a fixed dc voltage to an output of said subtracter, wherein

an output of said adder is input to said correction circuit.

3. The class D amplifier according to claim 1, wherein said correction circuit includes:

a first integrator for integrating said pulse width modulated signal;

a second integrator for integrating a difference between said feedback signal and a reference voltage generated on the basis of a dc component of said supply voltage; and

a comparator for comparing outputs of said first and second integrators, and

an output of said comparator is input to said power switch.

4. The class D amplifier according to claim 3, wherein

said second integrator includes an operational amplifier having a reverse input terminal and a non-reverse input terminal, said feedback signal being input to said reverse input terminal through a first resistor and said reference voltage and a fixed voltage being applied to said non-reverse input terminal through second and third transistors, respectively.

5. The class D amplifier according to claim 3, wherein

said second integrator includes an operational amplifier having a reverse input terminal and a non-reverse input terminal, said feedback signal and said reference voltage as reversed being applied to said reverse input terminal through first and second resistors, respectively, and a fixed voltage being applied to said non-reverse input terminal through a third resistor.