WO2019085256A1

WO2019085256A1 - Power amplification circuit, power amplifier, and laser television

Info

Publication number: WO2019085256A1
Application number: PCT/CN2018/071429
Authority: WO
Inventors: 熊再祥; 李屹
Original assignee: 深圳光峰科技股份有限公司
Priority date: 2017-11-01
Filing date: 2018-01-04
Publication date: 2019-05-09
Also published as: CN109756687B; CN109756687A

Abstract

A power amplification circuit (3), a power amplifier, and a laser television. The power amplification circuit (3) comprises: a power supply circuit (300) and a power amplification drive circuit (400), wherein the power supply circuit (300) is electrically connected to the power amplification drive circuit (400); the power supply circuit (300) comprises an LLC resonant circuit (301) and an overcurrent protection circuit (302); the overcurrent protection circuit (302) is connected in parallel with the LLC resonant circuit (301); the overcurrent protection circuit (302) comprises a first resistor (3021) and a second resistor (3022); a first end of the first resistor (3021) is electrically connected to an output end of the LLC resonant circuit (301); a second end of the first resistor (3021) is electrically connected to an overcurrent protection end of the LLC resonant circuit (301); a first end of the second resistor (3022) is electrically connected to an output end of the LLC resonant circuit (301); a second end of the second resistor (3022) is grounded; and the second resistor (3022) is a variable resistor. The power amplification circuit (3) can effectively solve problems such as crashing or the burning out of a rear-stage circuit board caused by playing low-frequency music and videos.

Description

Amplifier circuit, power amplifier and laser TV

Technical field

The invention relates to the field of circuit design, in particular to a power amplifier circuit, a power amplifier and a laser television.

Background technique

At present, the power amplifier control of laser TV is mainly composed of two parts: power supply and power amplifier drive. The power supply part mostly uses half-bridge resonant converter (LLC) to control DC-DC conversion. The power amplifier drive part mainly uses digital audio power amplifier to control the sound. Expand. Under normal circumstances, when playing low frequency (50Hz~200Hz) music and video, the amplifier driver needs a large current. When the output current of the power supply circuit increases, the voltage of the overcurrent protection terminal of the half-bridge resonant converter is greater than the threshold voltage. At this time, the Fairchild Semiconductor series power switch in the half-bridge resonant converter is triggered to enter the automatic restart protection mode, A corresponding voltage is delivered to the power amplifier drive circuit.

technical problem

Therefore, when the existing laser television plays low-frequency music and video, it is prone to downtime or burnout of the rear-level circuit board.

1 is a schematic structural view of an embodiment of a power amplifier circuit in the prior art. The power amplifier circuit 1 includes two parts of a power supply circuit 100 and a power amplifier drive circuit 200 connected in series, and the power supply circuit 100 and the power amplifier drive circuit 200 are electrically connected. Specifically, the power supply circuit 100 includes an LLC resonant circuit 101 and an overcurrent protection circuit 102, and the overcurrent protection circuit 102 is connected in parallel with the LLC resonant circuit 101. Commonly, the LLC resonant circuit 101 includes a semiconductor power switch in series and a first transformer, and the overcurrent protection circuit includes at least two fixed value resistors (not shown). When playing low frequency (50 Hz to 200 Hz) music and video, the power amplifier driving circuit 200 requires a large current. When the output current of the power supply circuit 100 increases, this causes the overcurrent protection terminal voltage of the LLC resonant circuit 101 to be greater than the threshold voltage, which triggers the Fairchild semiconductor series power switch in the LLC resonant circuit 101 to enter the automatic restart protection mode. Similarly, when playing low frequency music and video, if the output current of the power supply circuit is too large, the power amplifying circuit 201 may be burned out.

Therefore, it is necessary to provide an improved power amplifier circuit.

Technical solution

It is an object of the present invention to provide a power amplifier circuit, a power amplifier, and a laser television to solve the downtime that occurs when playing low frequency music and video or to burn out the rear stage circuit board.

In order to solve the above technical problem, a technical solution adopted by the present invention is to provide a power amplifier circuit including: a power supply circuit and a power amplifier driving circuit, the power supply circuit and the power amplifier driving circuit are electrically connected, and the power supply circuit includes an LLC resonant circuit and An overcurrent protection circuit, the overcurrent protection circuit is connected in parallel with the LLC resonant circuit, the overcurrent protection circuit includes a first resistor and a second resistor, a first end of the first resistor and the LLC resonant circuit The output end is electrically connected, the second end of the first resistor is electrically connected to the overcurrent protection end of the LLC resonant circuit, and the first end of the second resistor is electrically connected to the output end of the LLC resonant circuit. The second end of the second resistor is grounded, and the second resistor is a variable resistor.

In order to solve the above technical problem, another technical solution adopted by the present invention is to provide a power amplifier including a speaker and any one of the above power amplifier circuits, and the power amplifier circuit is electrically connected to the speaker.

In order to solve the above technical problem, another technical solution adopted by the present invention is to provide a laser television including any of the above power amplifier circuits.

Beneficial effect

The invention has the beneficial effects that the power amplifier circuit includes an overcurrent protection circuit and a current limiting circuit, and the variable second resistor is used to split the LLC resonant circuit by adjusting the second resistor. The resistance value makes the overvoltage protection terminal voltage of the LLC resonant circuit within the threshold voltage range, avoiding problems such as downtime caused by excessive output current of the power supply circuit or burnout of the rear circuit board when playing low frequency music and video. The invention can improve the playing effect of music and video and enhance the user experience.

DRAWINGS

1 is a schematic structural view of an embodiment of a power amplifier circuit in the prior art;

2 is a schematic structural diagram of an embodiment of a power supply circuit in a power amplifier circuit provided by the present invention;

3 is a schematic structural view of an embodiment of a power amplifier circuit provided by the present invention;

4 is a schematic structural view of an embodiment of a current limiting circuit in a power amplifier circuit provided by the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings in order to make the technical solutions, the technical solutions, and the technical effects achieved by the present invention.

Referring to FIG. 2 and FIG. 3, FIG. 2 is a schematic structural diagram of an embodiment of a power supply circuit in a power amplifier circuit according to the present invention, and FIG. 3 is a schematic structural diagram of an embodiment of a power amplifier circuit provided by the present invention. The power amplifier circuit 3 provided by the present invention includes two parts of the power supply circuit 300 and the power amplifier drive circuit 400 connected in series, and the power supply circuit 300 and the power amplifier drive circuit 400 are electrically connected. Specifically, the power supply circuit 300 includes an LLC resonant circuit 301 and an overcurrent protection circuit 302, and the overcurrent protection circuit 302 is connected in parallel with the LLC resonant circuit 301. Specifically, the overcurrent protection circuit 302 includes a first resistor 3021 and a second resistor 3022. The connection relationship is as follows. The first end of the first resistor 3021 is electrically connected to the output end of the LLC resonant circuit 301, and the second end of the first resistor 3021 is electrically connected to the overcurrent protection end of the LLC resonant circuit 301, and the second resistor 3022 is The first end is electrically connected to the output of the LLC resonant circuit 301, and the second end of the second resistor 3022 is grounded. The second resistor 3022 is a variable resistor.

In a specific implementation scenario, when playing low frequency (50 Hz ~ 200 Hz) music and video, the power amplifier driving circuit needs a large current, but the current flowing through the first resistor 3021 is excessive, resulting in overcurrent protection of the LLC resonant circuit 301. The voltage at the terminal is greater than the preset threshold and enters the automatic restart protection mode. At this time, by reducing the resistance of the second resistor 3022, the excessive current is shunted out through the second resistor 3022, thereby reducing the voltage of the overcurrent protection terminal to a reasonable range without causing an overcurrent protection terminal voltage. Enters the automatic protection mode beyond its preset voltage threshold.

The LLC resonant circuit 301 includes a semiconductor power switch 3011 and a first transformer 3012 connected in series. The first end of the semiconductor power switch 3011 is connected to the power supply voltage, and the overcurrent protection end of the semiconductor power switch 3011 is electrically connected to the second end of the first resistor 3021. The first end of the first transformer 3012 is electrically connected to the second end of the first power transformer 3011, and the third end of the first transformer 3012 is electrically connected to the first end of the first resistor 3021. A fourth end of a transformer 3012 is electrically coupled to the power amplifier drive circuit 400.

In a specific implementation scenario, when playing low frequency (50 Hz to 200 Hz) music and video, the power amplifier driving circuit 400 needs a large current, which may cause the voltage of the overcurrent protection terminal of the semiconductor power switch 3011 to be greater than a preset voltage threshold. Enter the automatic protection mode. In the present invention, by adjusting the second resistor 3022 and reducing its resistance, an excessive current is shunted out through the second resistor 3022, thereby reducing the voltage of the overcurrent protection terminal to a reasonable range without causing The flow protection terminal voltage exceeds its preset voltage threshold and enters the automatic protection mode.

In another specific implementation scenario, the LLC resonant circuit further includes a second transformer (not shown), the input end of the second transformer is electrically connected to the fourth end of the first transformer 3012, and the output of the second transformer and the power amplifier The drive circuit 400 is electrically connected. The use of a secondary transformer for voltage regulation ensures a smoother and more reliable electrical signal output.

In a specific implementation scenario, the DC voltage at the first end of the first transformer 3012 is 220V. It should be noted that the preset voltage threshold of the overcurrent protection terminal of the semiconductor power switch 3011 is a range. Among them, the preset voltage threshold is obtained by a plurality of experimental statistics and analysis to obtain a reasonable preset voltage threshold range, and is set by the power amplifier circuit. The following is an example of 5 volts.

When the voltage of the overcurrent protection terminal of the semiconductor power switch 3011 does not exceed 5 volts, the power supply circuit 300 operates normally. When playing low frequency (50 Hz to 200 Hz) music and video, the power amplifier driving circuit 400 requires a large current, which causes the current through the first transformer 3012 to become large, ranging from about 41.667 amps to 65 amps. In this embodiment, the first resistor 3021 has a resistance of 500 ohms. Correspondingly, when the current flowing through the first resistor 3021 is greater than 5/500=0.01 amps, the semiconductor power switch 3011 is triggered to enter the automatic restart protection mode. In order to prevent the current flowing through the first resistor 3021 from being greater than 0.01 amps to trigger the semiconductor power switch 3011 to enter the automatic restart protection mode, the resistance value of the second resistor 3022 needs to be adjusted accordingly to cause a shunting effect. Specifically, the current value flowing through the second resistor 3022 needs to be in the range of 41.657 amps to 64.99 amps, and the corresponding resistance range of the second resistor 3022 needs to be adjusted to 5/41.657 ohms to 5/64.99 ohms, that is, 0.077 ohms to 0.12 ohms. ohm. In other embodiments, the resistance range of the second resistance is not limited to the above range, and the DC voltage value according to the first end of the first transformer 3012 and the preset voltage threshold of the overcurrent protection terminal of the semiconductor power switch 3011 are required. Adjust and match accordingly, not limited here.

With continued reference to FIG. 3, the power amplifier driving circuit 400 includes a current limiting circuit 402 and a power amplifying circuit 401 connected in series, and the power amplifying circuit 401 is electrically connected to the power supply circuit 300 through the current limiting circuit 402.

With continued reference to FIG. 4, FIG. 4 is a schematic structural diagram of a current limiting circuit in a power amplifier driving circuit provided by the present invention. The current limiting circuit 402 is composed of a triode 4024, a third resistor 4021, a fourth resistor 4022, and a fifth resistor 4023. The second end of the third resistor 4021 is electrically connected to the first end of the fourth resistor 4022, and the connection point thereof is electrically connected to the base of the transistor 4024. The emitter of the transistor 4024 is electrically coupled to the first end of the fifth resistor 4023. The collector of the tertiary tube 4024 is electrically connected to the first end of the third resistor 4021, and its connection point is electrically connected to the power supply circuit. The second end of the fourth resistor 4022 is electrically connected to the second end of the fifth resistor 4023, and the connection point thereof is electrically connected to the power amplifying circuit. In the present embodiment, the triode 4024 is an NPN type triode. In other embodiments, the type of the triode may also be other commonly used models, which is not limited herein.

In a specific implementation scenario, when the voltage output current of the power circuit 300 is a normal rated value, the semiconductor power switch 3011 is turned on. When the circuit is working normally, the bias current of the transistor 4024 is provided by the third resistor 4021, and the transistor 4024 is saturated. The current does not control the current, and the power amplifier driving circuit 400 works normally. When the voltage output current of the power supply circuit 300 is greater than the normal rated value, the current limiting circuit 402 protects the power amplifying circuit 401 from being burned when the current increases. Specifically, when the output current of the power supply circuit 300 is greater than the normal rated value, the voltage drop across the fifth resistor 4023 increases, and the sum of the voltage drop across the fifth resistor 4023 and the junction of the transistor 4024 is close to the voltage drop of the fourth resistor 4022. Then, the current passing through the transistor 4024 is started to be limited, thereby achieving the purpose of protecting the power amplifying circuit 401.

Different from the prior art, the present invention provides an overcurrent protection circuit and a current limiting circuit in a power amplifier circuit, which utilizes a variable second resistor to shunt the LLC resonant circuit, and adjusts the resistance of the second resistor to cause the LLC resonant circuit to pass The voltage of the current protection terminal is within the threshold voltage range to avoid problems such as downtime caused by excessive output current of the power supply circuit or burnout of the circuit board after the low frequency music and video are played. The invention can improve the playing effect of music and video and enhance the user experience.

The power amplifier circuit in any of the above embodiments can be applied to the power amplifier and electrically connected to the speaker disposed in the power amplifier.

Different from the prior art, in the power amplifier provided by the present invention, the power amplifier circuit includes an overcurrent protection circuit and a current limiting circuit, and the variable second resistor is used to shunt the LLC resonant circuit, and the resistance of the second resistor is adjusted. The value makes the overvoltage protection terminal voltage of the LLC resonant circuit within the threshold voltage range, avoiding problems such as downtime caused by excessive output current of the power supply circuit or burnout of the rear stage circuit board when playing low frequency music and video. The invention can improve the playing effect of music and video and enhance the user experience.

The power amplifier circuit in any of the above embodiments can also be applied to a laser television.

Different from the prior art, in the laser television provided by the present invention, the power amplifier circuit includes an overcurrent protection circuit and a current limiting circuit, and the variable second resistor is used to shunt the LLC resonant circuit, and the resistance of the second resistor is adjusted. The value makes the overvoltage protection terminal voltage of the LLC resonant circuit within the threshold voltage range, avoiding problems such as downtime caused by excessive output current of the power supply circuit or burnout of the rear stage circuit board when playing low frequency music and video. The invention can improve the playing effect of music and video and enhance the user experience.

In the above, various other changes and modifications can be made in accordance with the technical solutions and technical concept of the present invention, and all such changes and modifications should be included in the appended claims. The scope of protection.

Claims

a power amplifier circuit, comprising: a power supply circuit and a power amplifier driving circuit, wherein the power supply circuit and the power amplifier driving circuit are electrically connected,

The power supply circuit includes an LLC resonant circuit and an overcurrent protection circuit, the overcurrent protection circuit is connected in parallel with the LLC resonant circuit, the overcurrent protection circuit includes a first resistor and a second resistor, and the first resistor One end is electrically connected to an output end of the LLC resonant circuit, and a second end of the first resistor is electrically connected to an overcurrent protection end of the LLC resonant circuit, a first end of the second resistor and the LLC The output of the resonant circuit is electrically connected, the second end of the second resistor is grounded, and the second resistor is a variable resistor.
The power amplifier circuit according to claim 1, wherein the power amplifier driving circuit comprises a current limiting circuit and a power amplifying circuit connected in series, and the power amplifying circuit is electrically connected to the power supply circuit through the current limiting circuit.
The power amplifier circuit according to claim 2, wherein the current limiting circuit is composed of a triode, a third resistor, a fourth resistor, and a fifth resistor, and the second end of the third resistor and the first end of the fourth resistor Electrical connection, the connection point and the base of the triode are electrically connected;

The emitter of the triode is electrically connected to the first end of the fifth resistor;

The collector of the tertiary tube is electrically connected to the first end of the third resistor, and the connection point is electrically connected to the power circuit;

The second end of the fourth resistor is electrically connected to the second end of the fifth resistor, and the connection point thereof is electrically connected to the power amplifying circuit.
A power amplifier circuit according to claim 3, wherein said triode is an NPN type triode.
A power amplifier circuit according to claim 1, wherein said LLC resonant circuit comprises a semiconductor power switch and a first transformer connected in series,

The first end of the semiconductor power switch is connected to the power supply voltage, and the overcurrent protection end of the semiconductor power switch is electrically connected to the second end of the first resistor;

The first end of the first transformer is connected to a DC voltage, the second end of the first transformer is electrically connected to the second end of the semiconductor power switch, and the third end of the first transformer and the first end of the first resistor The terminal is electrically connected, and the fourth end of the first transformer is electrically connected to the power amplifier driving circuit.
The power amplifier circuit of claim 5, wherein the LLC resonant circuit further comprises a second transformer, the second transformer input is electrically connected to the fourth end of the first transformer, and the second transformer output is The power amplifier driving circuit is electrically connected.
The power amplifier circuit of claim 1 wherein said predetermined voltage threshold is 5 volts.
The power amplifier circuit according to claim 7, wherein said first resistance value is 500 ohms, and said second resistance value ranges from 0.077 ohms to 0.12 ohms.
A power amplifier comprising a speaker and the power amplifier circuit of any of claims 1-8, the power amplifier circuit being electrically coupled to the speaker.
A laser television comprising the power amplifier circuit of any of claims 1-8.