CN112865730B - Class-D amplifier circuit and audio amplification method - Google Patents
Class-D amplifier circuit and audio amplification method Download PDFInfo
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- CN112865730B CN112865730B CN201911186316.3A CN201911186316A CN112865730B CN 112865730 B CN112865730 B CN 112865730B CN 201911186316 A CN201911186316 A CN 201911186316A CN 112865730 B CN112865730 B CN 112865730B
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- 238000000034 method Methods 0.000 title claims abstract description 9
- 230000003321 amplification Effects 0.000 title claims description 4
- 238000003199 nucleic acid amplification method Methods 0.000 title claims description 4
- 239000010752 BS 2869 Class D Substances 0.000 title description 2
- 230000001105 regulatory effect Effects 0.000 claims description 10
- 238000010586 diagram Methods 0.000 description 4
- 230000005236 sound signal Effects 0.000 description 3
Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
- H03F3/217—Class D power amplifiers; Switching amplifiers
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- Power Engineering (AREA)
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Abstract
The present disclosure relates to a class D amplifier circuit and an audio amplifying method, the circuit includes an input impedance, an operational amplifier, a voltage adjusting circuit, a pulse generating circuit and a driving circuit. The input impedance is coupled to the input end of the operational amplifier, receives an input voltage and outputs an input current. The operational amplifier outputs an amplified signal according to an input operation voltage and a feedback signal under the power supply of a first power supply voltage. The voltage adjusting circuit adjusts an input operation voltage of the operational amplifier. The pulse generating circuit outputs a pulse width modulation signal according to the amplified signal. The driving circuit generates a driving signal according to the pulse width modulation signal under the power supply of a second power supply voltage. Wherein the feedback signal is related to the driving signal.
Description
Technical Field
The present invention relates to an amplifier, and more particularly, to a class D amplifier circuit and an audio amplifying method.
Background
The class D amplifier is capable of converting an audio signal into high frequency pulses that can be switched out according to an audio input signal. In general, class D amplifiers use pulse width modulators to generate pulse width modulated signals. Here, the pulse width of the pulse width modulated signal can vary with the amplitude of the audio signal. Class D amplifiers have high performance compared to class AB amplifiers, thus significantly reducing the cost, size and weight of the overall system, and are widely used in devices requiring various audio frequencies, such as cell phones, flat panel televisions, and home theater receivers. However, in the existing class D amplifier, the supply voltage of the output stage always affects the operation voltage of the amplifier, so that the amplifier cannot achieve better operation characteristics.
Disclosure of Invention
In one embodiment, a class D amplifier circuit includes an input impedance, an operational amplifier, a voltage adjustment circuit, a pulse generation circuit, and a driving circuit. The input impedance is coupled to the input end of the operational amplifier, receives an input voltage and outputs an input current. The operational amplifier outputs an amplified signal according to an input operation voltage and a feedback signal under the power supply of a first power supply voltage. The voltage adjusting circuit adjusts an input operation voltage of the operational amplifier. The pulse generating circuit outputs a pulse width modulation signal according to the amplified signal. The driving circuit generates a driving signal according to the pulse width modulation signal under the power supply of a second power supply voltage. Wherein the feedback signal is related to the driving signal.
In one embodiment, an audio amplification method includes converting an input current to an input voltage; under the power supply of a first power supply voltage, outputting an amplified signal according to the input voltage, an input operation voltage and a feedback signal; adjusting an input operating voltage of the operational amplifier; outputting a pulse width modulation signal according to the amplified signal; and generating a driving signal according to the pulse width modulation signal under the power supply of a second power supply voltage. Wherein the feedback signal is related to the driving signal.
In some embodiments, the adjustment of the input operation voltage is achieved by providing an adjustment current.
In some embodiments, the adjustment current is independent of the first supply voltage.
In some embodiments, the regulated current is related to the first supply Voltage or to a Bandgap reference Voltage (Bandgap Voltage).
In some embodiments, the maximum current value of the second power supply voltage is greater than or equal to thousand times the maximum current value of the first power supply voltage.
In summary, according to the class D amplifier circuit and the audio amplifying method of the present invention, the input operating voltage of the operational amplifier is not affected by the variation of the supply voltage (the second supply voltage) of the output stage, and the input operating voltage is not required to be fixed to half of the supply voltage (the first supply voltage) of the operational amplifier, so that the input operating voltage can be determined according to the input pair types of various operational amplifiers, and the preferred operating voltage range of the operational amplifier is further achieved.
Drawings
Fig. 1 is a schematic diagram of a class D amplifier circuit according to an embodiment of the invention.
Fig. 2 is a flowchart of an audio amplifying method according to an embodiment of the invention.
Fig. 3 is a schematic diagram illustrating an operation of an exemplary voltage adjusting circuit shown in fig. 1.
Fig. 4 is a schematic diagram illustrating an operation of an exemplary voltage adjusting circuit shown in fig. 1.
Detailed Description
Referring to fig. 1, fig. 1 is a schematic diagram of a class D amplifier circuit according to an embodiment of the invention, wherein the class D amplifier circuit 10 is configured to receive an input voltage Vi and output a driving signal Vo to drive a load circuit 20. In some embodiments, the load circuit 20 may be, for example, an earphone or an audio output device such as a stereo, but is not limited thereto.
Here, the class D amplifier circuit 10 includes an input impedance 110, a voltage adjusting circuit 130, an operational amplifier 150, a pulse generating circuit 170, and a driving circuit 190.
The input impedance 110 is coupled to the input of the operational amplifier 150 with the voltage adjustment circuit 130. The output of the operational amplifier 150 is coupled to the pulse generating circuit 170. The pulse generating circuit 170 is coupled to the operational amplifier 150 and the driving circuit 190. The output of the driving circuit 190 is coupled back to the input of the operational amplifier 150 via a feedback path and provides a feedback signal If to the operational amplifier 150.
Referring to fig. 1 and 2, the input impedance 110 receives an input voltage Vi and generates an input current, i.e. converts the input voltage Vi into the input current (step S11). The voltage adjusting circuit 130 adjusts an input operation voltage of the operational amplifier 150 (step S13). The operational amplifier 150 outputs an amplified signal according to the input operation voltage and a feedback signal If under the power supply of a first power voltage Vcc (step S15). The pulse generating circuit 170 outputs a pulse width modulation signal (PulseWidth Modulation Signal; PWM SIGNAL) according to the amplified signal (step S17). The driving circuit 190 generates a driving signal Vo according to the pulse width modulation signal under the power of a second power voltage Vdd (step S19). Wherein the feedback signal If is related to the driving signal Vo.
In some embodiments, during the maximum volume output by the class D amplifier circuit 10, the maximum current value of the second supply voltage Vdd is greater than ten times the maximum current value of the first supply voltage Vcc. Generally, the second power voltage Vdd can pump a large current corresponding to a large output current (e.g., playing a large volume of audio signal) with respect to the first power voltage Vcc. The signal of the first power supply voltage Vcc is cleaner than the signal of the second power supply voltage Vdd.
In some embodiments, the voltage adjustment circuit 130 may be designed to eliminate the need to fix the first power supply voltage Vcc (i.e.,) Instead, the appropriate input operating voltage is determined for the input pair transistor form of the different operational amplifiers 150 (e.g.: Or (b) )。
In some embodiments, the voltage adjustment circuit 130 adjusts the input operating voltage of the operational amplifier 150 by providing an adjustment current (It) that adjusts the input current. In one embodiment, the regulated current (It) may be independent of the first supply voltage Vcc.
In an example, referring to fig. 3, the voltage adjusting circuit 130 may include a voltage-to-current component 131, a Y-time amplifying component 133, and a subtractor 135. The Y-power amplifying device 133 receives the first power voltage Vcc. A first input of subtractor 135 receives half of the second supply voltage Vdd. A second input terminal of the subtractor 135 is coupled to the output of the Y-time amplifying component 133, i.e. receives Y times the first power voltage Vcc (e.g. y×vcc). An output terminal of the subtractor 135 is coupled to the voltage-to-current component 131. The voltage-to-current component 131 generates a regulating current (It) according to the second power voltage Vdd and Y times the second power voltage Vdd (e.g.,). Wherein Y times is a specific multiplying power, and Y is a constant. In some embodiments, the voltage-to-current component 131 may be, for example, an impedance component (e.g.,) But is not limited thereto.
Here, the relationship of the input operation voltage (Vz) is expressed by the following expression 1.
The relation of the adjustment current (It) can be obtained according to the circuit design of the voltage adjustment circuit 130 as shown in the following formula 2.
Wherein,Representing the voltage-to-current component 131 and Vy representing the first amplified voltage generated by the Y-fold amplifying component 133. Here, the first amplified voltage Vy and the first power voltage Vcc may be in a proportional relationship. The ratio may be a specific ratio, i.e., Y. In other words, the first amplified voltage Vy can be realized with Y times the first power supply voltage Vcc. At this time, the adjustment current (It) of the above formula 2 can be replaced with the following formula 3.
As can be seen from the above equation 3, the adjustment current (It) can be proportional to the difference between the second power voltage Vdd and the first power voltage Vcc of a specific multiplying power (Y). Then, the adjustment current (It) of the above formula 3 is substituted into formula 1 to obtain the following formula 4 of the input operation voltage (Vz).
And, in the formula 4,It can be seen that the input operating voltage (Vz) can be proportional (Y times) to the first power voltage Vcc under the circuit design of the voltage adjusting circuit 130. Therefore, the input operation voltage (Vz) is not affected by the variation of the second power supply voltage Vdd.
In another example, referring to fig. 4, the voltage adjusting circuit 130 may include a voltage-to-current component 132, a K-time amplifying component 134, and a subtractor 135. The K-time amplifying device 134 receives a Bandgap reference Voltage (Bandgap Voltage) Vref. A first input of subtractor 135 receives half of the second supply voltage Vdd. A second input terminal of the subtractor 135 is coupled to the output of the K-times amplifying device 134, i.e. receives K-times the bandgap reference voltage Vref (e.g. k×vref). An output of the subtractor 135 is coupled to the voltage-to-current component 132. The voltage-to-current component 132 generates a regulated current (It) according to the second power voltage Vdd and K times the bandgap reference voltage Vref (e.g.,). Wherein, K times is a specific multiplying power, and K is a constant. Here, K and Y can be the same value or different values. In some embodiments, the voltage-to-current component 132 may be, for example, an impedance component (e.g.,) But is not limited thereto.
Here, the relational expression of the input operation voltage (Vz) is as follows in expression 5.
The relation of the adjustment current (It) can be obtained according to the circuit design of the voltage adjustment circuit 130 as shown in the following formula 6.
Wherein,Representing the voltage-to-current element 132, and Vk represents the second amplified voltage generated by the K-fold amplifying element 134. Here, the second amplified voltage Vk is proportional to the bandgap reference voltage Vref. Moreover, the ratio relationship may be a specific multiplying power, i.e. K times as described above. In other words, the second amplified voltage Vk can be realized with a band gap reference voltage Vref of K times. Therefore, the adjustment current (It) of the above equation 6 can be replaced with the following equation 7.
As can be seen from the above equation 7, the adjustment current (It) can be proportional to the difference between the second power voltage Vdd and the bandgap reference voltage Vref with a specific multiplying power (K). Next, the adjustment current (It) of the above equation 7 is substituted into equation 5 to obtain the following equation 8 of the input operation voltage (Vz).
And, in the formula 8,It can be seen that the input operating voltage (Vz) can be proportional (K times) to the bandgap reference voltage Vref under the circuit design of the voltage adjusting circuit 130. Therefore, the input operation voltage (Vz) is not affected by the variation of the second power supply voltage Vdd. In some embodiments, the bandgap reference voltage Vref may be generated by any reference voltage generating circuit.
In some embodiments, the feedback path can be implemented with a feedback resistor Rf. Here, the output terminal of the driving circuit 190 is coupled to the input terminal of the operational amplifier 150 via a feedback resistor Rf. For example, the driving signal Vo output by the driving circuit 190 is converted into a corresponding feedback signal If through the feedback resistor Rf, and the formed feedback signal If is returned and input to the input end of the operational amplifier 150.
In summary, according to the class D amplifier circuit and the audio amplifying method of the present invention, the input operating voltage of the operational amplifier is not affected by the variation of the supply voltage (the second supply voltage) of the output stage, and the input operating voltage is not required to be fixed to half of the supply voltage (the first supply voltage) of the operational amplifier, so that the input operating voltage can be determined according to the input pair types of various operational amplifiers, and the preferred operating voltage range of the operational amplifier is further achieved.
[ Symbolic description ]
10 Class D amplifier circuit
20. Load circuit
110. Input impedance
130. Voltage regulating circuit
131. Voltage-to-current assembly
133 Y-times amplifying assembly
132. Voltage-to-current assembly
134 K times amplifying assembly
135. Subtracter
150. Operational amplifier
170. Pulse generating circuit
190. Driving circuit
Vi input voltage
Vcc first supply voltage
If feedback signal
Vdd second supply voltage
Vo drive signal
Rf feedback resistor
Vref bandgap reference voltage
S11-S19.
Claims (6)
1. A class D amplifier circuit comprising:
an operational amplifier for outputting an amplified signal according to an input operation voltage and a feedback signal under the power supply of a first power supply voltage;
an input impedance coupled to the input end of the operational amplifier for receiving an input voltage and generating an input current;
a voltage adjusting circuit for adjusting the input operation voltage of the operational amplifier;
A pulse generating circuit for outputting a pulse width modulation signal according to the amplified signal; and
A driving circuit for generating a driving signal according to the pulse width modulation signal under the power supply of a second power supply voltage, wherein the feedback signal is related to the driving signal;
The voltage adjusting circuit provides an adjusting current to adjust the input operation voltage, and the adjusting current is in proportion to the difference value between the second power supply voltage and the first power supply voltage with a specific multiplying power.
2. A class D amplifier circuit as defined in claim 1, wherein the regulated current is independent of the first supply voltage.
3. A class D amplifier circuit as defined in claim 1, wherein the regulated current is related to the first supply voltage.
4. A class D amplifier circuit comprising:
an operational amplifier for outputting an amplified signal according to an input operation voltage and a feedback signal under the power supply of a first power supply voltage;
an input impedance coupled to the input end of the operational amplifier for receiving an input voltage and generating an input current;
a voltage adjusting circuit for adjusting the input operation voltage of the operational amplifier;
A pulse generating circuit for outputting a pulse width modulation signal according to the amplified signal; and
A driving circuit for generating a driving signal according to the pulse width modulation signal under the power supply of a second power supply voltage, wherein the feedback signal is related to the driving signal;
The voltage regulating circuit provides a regulating current to regulate the input operation voltage;
wherein the regulated current is related to a bandgap reference voltage;
The adjusting current is in proportion to the difference between the second power supply voltage and the band gap reference voltage with a specific multiplying power.
5. The class D amplifier circuit of claim 4, wherein the maximum current value of the second supply voltage is greater than or equal to ten times the maximum current value of the first supply voltage.
6. An audio amplification method, comprising:
Adjusting an input operating voltage of an operational amplifier;
under the power supply of a first power supply voltage, outputting an amplified signal by the operational amplifier according to the input operation voltage and a feedback signal;
outputting a pulse width modulation signal according to the amplified signal; and
Generating a driving signal according to the pulse width modulation signal under the power supply of a second power supply voltage, wherein the feedback signal is related to the driving signal;
Wherein adjusting an input operating voltage of an operational amplifier includes providing an adjusting current to adjust the input operating voltage, and the adjusting current is proportional to a difference between the second power supply voltage and the first power supply voltage of a specific multiplying power.
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| CN201911186316.3A CN112865730B (en) | 2019-11-27 | 2019-11-27 | Class-D amplifier circuit and audio amplification method |
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| CN201911186316.3A CN112865730B (en) | 2019-11-27 | 2019-11-27 | Class-D amplifier circuit and audio amplification method |
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| CN115561662A (en) * | 2022-09-26 | 2023-01-03 | 上海芯聆半导体科技有限公司 | Power supply detection circuit, power supply circuit, power amplifier integrated circuit and sound equipment |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6448851B1 (en) * | 2001-08-21 | 2002-09-10 | Texas Instruments Incorporated | Amplifier with offset compensation for a high voltage output transistor stage |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US5410592A (en) * | 1993-06-04 | 1995-04-25 | Harris Corporation | Class `D` audio speaker amplifier circuit with state variable feedback control |
| JPH08275514A (en) * | 1995-03-31 | 1996-10-18 | Toshiba Corp | Dc-dc converter |
| GB2425418B (en) * | 2005-04-22 | 2007-09-19 | Motorola Inc | Amplifier circuit and rf transmitter incorporating the circuit |
| TWI508430B (en) * | 2012-08-30 | 2015-11-11 | Anpec Electronics Corp | Pop-free single-ended output class-d amplifier |
| JP6510199B2 (en) * | 2014-08-19 | 2019-05-08 | ローム株式会社 | Switching circuit, audio amplifier integrated circuit, electronic device, driving method of electroacoustic transducer |
| TWI559682B (en) * | 2015-01-14 | 2016-11-21 | 智原科技股份有限公司 | Driving circuit, driving apparatus, and method for adjusting output impedance to match transmission line impedance by current adjusting |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6448851B1 (en) * | 2001-08-21 | 2002-09-10 | Texas Instruments Incorporated | Amplifier with offset compensation for a high voltage output transistor stage |
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