Output control apparatus of pulse width modulator

• US 6,803,798 B1
• Filed: 08/13/2003
• Issued: 10/12/2004
• Est. Priority Date: 03/19/2003
• Status: Expired due to Fees

• Current Assignee: Sonix Technology Company Limited
• Original Assignee: Sonix Technology Company Limited
• Inventors: Wei, Wei-Hsin, Chang, Jung-Lin, Ho, Sheng-Yi
• Primary Examiner(s): Lam, Tuan T.
• Application Number:
  US10/639,503
• Publication Number:
  US 20040183579A1
• Time in Patent Office: 426 Days
• Field of Search: 327/178, 327/179, 327/180, 327/333, 327/312, 327/316, 327/323, 330/10, 330/135, 330/136, 381/120, 381/121, 381/107, 381/108
• US Class Current: 327/178
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers
• CPC Class Codes: H03G 3/00 Gain control in amplifiers or frequency changers
• CPC Class Codes: H03G 3/3021 by varying the duty cycle

Abstract

The invention provides an output control apparatus for adjusting the output level of a pulse width modulation (PWM) signal by changing the amplitude level of the output PWM signal. The output control apparatus comprises a control signal generator, a digital-to-analog converter (DAC), and an output circuit. The control signal generator generates a digital control signal. The DAC outputs a predetermined level according to the digital control signal. The output circuit with a negative feedback loop receives the PWM signal and receives the predetermined level by the negative feedback loop. While the PWM signal is logic number “0”, the negative feedback loop is not switched on, so as to control the level of the PWM signal at a base level. While the PWM signal is logic number “1”, the negative feedback loop is switched on, so as to control the level of the PWM signal at the predetermined level.

Claims

1. A control apparatus for controlling a level of a pulse width modulation signal (PWM signal) generated by a pulse width modulator (PWM), the apparatus comprising:

a control signal generator for generating a digital control signal;

a digital-to-analog converter (DAC) for outputting a predetermined level according to the digital control signal; and

an output circuit with a negative feedback loop for

receiving the PWM signal, and receiving the predetermined level by the negative feedback loop;

while the PWM signal is logic number “

0”

, not switching on the negative feedback loop, so as to control the level of the PWM signal at a base level; and

while the PWM signal is logic number “

1”

, switching on the negative feedback loop, so as to control the level of the PWM signal at the predetermined level.

2. The apparatus of claim 1, wherein the control signal generator is an N bits structure for generating 2^N kinds of different digital control signals.

3. The apparatus of claim 2, wherein the DAC generates 2^N kinds of different predetermined levels according to the 2^N kinds of different digital control signals.

4. The apparatus of claim 1, wherein the DAC further comprises:

a decoder for converting the digital control signal to a corresponding level control signal;

a plurality of analog switches, each analog switches switching on or off being controlled by the level control signal; and

a plurality of resistances connecting to a power supply for determining the predetermined level according to the allocation of the plurality of analog switches.

5. The apparatus of claim 1, wherein the output circuit further comprises a receiving element for receiving the PWM signal and judging the PWM signal is logic number “

0”

or “

1”

.

6. The apparatus of claim 1, wherein the output circuit further comprises a base level input for providing the base level.

7. The apparatus of claim 6, wherein the output circuit further comprises a plurality of switch components for

while the PWM signal is logic number “

0”

, not switching on the negative feedback loop but switching on the base level input to control the level of the PWM signal at the base level; and

while the PWM signal is logic number “

1”

, switching on the negative feedback loop to control the level of the PWM signal at the predetermined level.

8. The apparatus of claim 7, wherein the negative feedback loop further comprises an amplifier combination for receiving the predetermined level, and while the negative feedback loop is switched on, setting the level of the PWM signal equal to the predetermined level.

9. An output control apparatus for controlling an output level of a PWM signal at a predetermined level, the output control apparatus comprising:

an input for inputting the PWM signal;

a predetermined level input for providing a predetermined level;

a base level input for providing a base level;

a high level input for providing a highest level;

a level output for outputting an output level of the PWM signal;

a switch combination comprising a plurality of switches for connecting to the input, the base level input, and the high level input; and

an amplifier comprising;

an inverting input for inputting the predetermined level;

a non-inverting input for connecting to the level output; and

an amplifier output for connecting to the switch combination;

wherein, while the PWM signal is logic number “

0”

, the switch combination switches on the base level input and connects the amplifier output to the high level input to make the amplifier not be switched on, so as to control the level of the PWM signal at the base level; and

wherein, while the PWM signal is logic number “

1”

, the switch combination doesn'"'"'t switch on the base level input and connects the amplifier output to the level output to make the amplifier and the switch combination form a negative feedback loop, so as to control the level of the PWM signal at the predetermined level.

10. The output control apparatus of claim 9, further comprising a control signal generator for generating a digital control signal.

11. The output control apparatus of claim 10, further comprising a DAC for receiving the digital control signal and outputting the predetermined level to the predetermined level input, wherein the predetermined level is determined by the digital control signal.

12. The apparatus of claim 11, wherein the control signal generator is a N bits structure for generating 2^N kinds of different digital control signals.

13. The apparatus of claim 11, wherein the DAC further comprises:

a decoder for converting the digital control signal to a corresponding level control signal;

a plurality of analog switches, each analog switches switching on or off being controlled by the level control signal; and

a plurality of resistances connecting to a power supply for determining the predetermined level according to the allocation of the plurality of analog switches.

14. The apparatus of claim 12, wherein the DAC generates 2^N kinds of different predetermined levels according to the 2^N kinds of different digital control signals.

15. An output control apparatus for controlling an output level of a PWM signal at a predetermined level, the output control apparatus comprising:

a set of differential inputs for differentially inputting the PWM signal;

a predetermined level input for providing a predetermined level;

a set of base level inputs for providing a base level;

a set of high level inputs for providing a highest level;

a set of differential level outputs for differentially outputting an output level of the PWM signal;

a switch combination comprising a plurality of switches for connecting to the set of differential inputs, the set of base level inputs, and the set of high level inputs; and

an amplifier combination comprising a plurality of amplifiers, each amplifier connecting to a differential input of the set of differential inputs, a base level input of the set of base level inputs, a high level input of the set of high level inputs, and a differential level input of the set of differential level inputs, each the amplifier comprising;

an inverting input for inputting the predetermined level;

a non-inverting input for connecting to the differential level output; and

an amplifier output for connecting to the switch combination;

wherein while the PWM signal is logic number “

0”

, the switch combination switches on the base level input and connects the amplifier output to the high level input to make the amplifier not be switched on, so as to control the level of the PWM signal at the base level; and

while the PWM signal is logic number “

1”

, the switch combination doesn'"'"'t switch on the base level input and connects the amplifier output to the level output to make the amplifier combination and the switch combination form a negative feedback loop, so as to control the level of the PWM signal at the predetermined level.

16. The output control apparatus of claim 15, further comprising a control signal generator for generating a digital control signal.

17. The output control apparatus of claim 16, further comprising a DAC for receiving the digital control signal and outputting the predetermined level to the predetermined level input;

wherein the predetermined level is determined by the digital control signal.

18. The apparatus of claim 17, wherein the control signal generator is an N bits structure for generating 2^N kinds of different digital control signals.

19. The apparatus of claim 17, wherein the DAC further comprises:

a decoder for converting the digital control signal to a corresponding level control signal;

a plurality of analog switches, each analog switches switching on or off being controlled by the level control signal; and

a plurality of resistances connecting to a power supply for determining the predetermined level according to the allocation of the plurality of analog switches.

20. The apparatus of claim 18, wherein the DAC generates 2^N kinds of different predetermined levels according to the 2^N kinds of different digital control signals.