Class D amplifier

• US 20060028272A1
• Filed: 08/03/2005
• Published: 02/09/2006
• Est. Priority Date: 08/03/2004
• Status: Active Grant

• Current Assignee: Pioneer Corporation
• Original Assignee: Pioneer Corporation
• Inventors: Ozawa, Akio, Kudo, Kazuyuki
• Granted Patent: US 7,276,968 B2
• Time in Patent Office: Days
• US Class Current: 330/251
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers

Abstract

A drive signal that matches the bias of a transistor is generated. A differential amplifier calculates the difference between a specified voltage of negative power supply and another input signal. Then, a resistor that realizes a pull-down function level-shifts it towards a negative power supply voltage having a higher absolute voltage value to generate another differential signal, which is in turn amplified in another amplifier, to generate another drive signal that matches the bias of another transistor. Respective current mirror circuits detect a falling voltage occurring at both ends of a resistor connected between the transistor and the higher positive power supply voltage and a falling voltage occurring at both ends of a resistor connected between the other transistor and the higher negative power supply voltage, respectively. Then, the presence of an excessive electric current is detected by generating electric currents in accordance with to the falling voltages.

Claims

1. A class D amplifier comprising:

a pair of switching elements composed of first and second switching elements which are complementally symmetrical with respect to a voltage of a power supply;

first bias voltage level shift means that generates a drive signal to be supplied to said first switching element by level-shifting a square-wave first input signal; and

second bias voltage level shift means that generates a drive signal to be supplied to said second switching element by level-shifting a square-wave second input signal,

said class D amplifier being provided for performing class D amplification by allowing said first and second switching elements to perform a push-pull operation based on the respective drive signals supplied thereto,

wherein said first bias voltage level shift means has first differential amplification means that calculates a differential signal between said first input signal and a predetermined voltage, and first bias means that generates a level-shifted drive signal to be supplied to said first switching element by pulling up said differential signal towards the power supply voltage of the first switching element,

wherein said second bias voltage level shift means has second differential amplification means that calculates a differential signal between said second input signal and a predetermined voltage, and second bias means that generates a level-shifted drive signal to be supplied to said second switching element by pulling down said differential signal towards the power supply voltage of the second switching element.

2. A class D amplifier having a pair of switching elements composed of first and second switching elements which are complementally symmetrical with respect to a voltage of a power supply, said class D amplifier being provided for performing class D amplification by allowing said first and second switching elements to perform a push-pull operation based on the respective square-wave drive signals supplied thereto, p1 the class D amplifier comprising:

a first resistor connected between said first switching element and said power supply;

a second resistor connected between said second switching element and said power supply;

a first current mirror circuit that receives a falling voltage generated at both ends of said first resistor and generates an electric current corresponding to said falling voltage; and

a second current mirror circuit that receives a falling voltage generated at both ends of said second resistor and generates an electric current corresponding to said falling voltage,

wherein said respective currents output from said first and second current mirror circuits serve as an excessive electric current detection current that shows whether or not excessive electric currents flow in said first and second switching elements.

3. A class D amplifier comprising:

a pair of switching elements composed of first and second switching elements which are complementally symmetrical with respect to a voltage of a power supply;

first bias voltage level shift means that generates a drive signal to be supplied to said first switching element by level-shifting a square-wave first input signal; and

second bias voltage level shift means that generates a drive signal to be supplied to said second switching element by level-shifting a square-wave second input signal,

said class D amplifier being provided for performing class D amplification by allowing said first and second switching elements to perform a push-pull operation based on the respective drive signals supplied thereto,

wherein the class D amplifier further comprises;

a first resistor connected between said first switching element and said power supply;

a second resistor connected between said second switching element and said power supply;

a first current mirror circuit that receives a falling voltage generated at both ends of said first resistor and generates an electric current corresponding to said falling voltage; and

a second current mirror circuit that receives a falling voltage generated at both ends of said second resistor and generates an electric current corresponding to said falling voltage,

wherein said first bias voltage level shift means has first differential amplification means that calculates a differential signal between said first input signal and a predetermined voltage, and first bias means that generates a level-shifted drive signal to be supplied to said first switching element by pulling up said differential signal towards the power supply voltage of the first switching element,

wherein said second bias voltage level shift means has second differential amplification means that calculates a differential signal between said second input signal and a predetermined voltage, and second bias means that generates a level-shifted drive signal to be supplied to said second switching element by pulling down said differential signal towards the power supply voltage of the second switching element.