Filter circuit of electronic tube power amplifier switching power supply

Abstract

The utility model belongs to the field of audio power amplifiers, and discloses a filter circuit of an electronic tube power amplifier switching power supply, which comprises an alternating current filter circuit, a full-wave rectifier circuit for converting power frequency alternating current into direct current, and a direct current filter circuit, and an alternating current input end of the full-wave rectifier circuit is connected with the alternating current filter circuit through the alternating current filter circuit. The direct-current output end of the full-wave rectification circuit is connected with the direct-current filter circuit; the filter circuit of the electronic tube power amplifier switching power supply adopts a'double-pi-type 'filter mode of a pi-type alternating-current filter circuit and a pi-type direct-current filter circuit, and has the advantages of simple circuit structure, high efficiency and reasonable design, and in the pi-type direct-current filter circuit, a power frequency inductor adopts a large inductor of a millihenry level, the direct-current output ripple is relatively small, and the filter circuit is stable and reliable. The direct-current voltage at the two ends of the filter capacitor is high, and the current distortion correction and power factor compensation capabilities are improved, so that the power factor of the electronic tube power amplifier switching power supply is effectively improved, and meanwhile, the ground noise level of a power amplifier is also reduced.

Description

Technical Field

[0001] The utility model relates to the field of audio power amplifiers, and more specifically, to a filter circuit of a switching power supply of an electronic tube power amplifier. Background Art

[0002] In the field of audio power amplifiers (amplifiers for short), currently, according to the power amplifier components, they are mainly divided into two types, namely transistor amplifiers and tube amplifiers. Tube amplifiers have low power and weak large dynamic effects. After the emergence of transistor amplifiers, they have replaced tube amplifiers in the mainstream market because of their low cost, small size, and high power. They have good support for pop music, especially large dynamics. However, since tube amplifiers also have their own unique characteristics, such as natural and sweet sound, "gall taste", and good reproduction of classical music, they are also loved by some audiophiles and can maintain some markets. There are three types of conventional tube amplifier filament power supplies. The first power supply is to directly provide the required low-voltage AC power supply through the power frequency transformer, the second power supply is to provide a low-voltage DC power supply after the power frequency transformer is stepped down and rectified and filtered, and the third power supply is to provide a low-voltage DC power supply through a switching power supply. Since the core power amplifier component used in the tube amplifier is the tube, and the tube filament power supply requires low voltage and high current, a more efficient switching power supply is generally used. The front end of the switching power supply generally includes an AC filter circuit, a full-wave rectifier circuit that converts industrial frequency AC power into DC power, and a DC filter circuit. The AC input end of the full-wave rectifier circuit is connected to the AC filter circuit through the AC filter circuit, and the DC output end of the full-wave rectifier circuit is connected to the DC filter circuit. In order to improve the filtering effect and the power factor, the switching power supply generally uses a passive PFC filter circuit to add a full-wave rectifier circuit, that is, the DC filter circuit uses a passive PFC filter circuit. Audio power amplifiers have relatively high requirements for power purity. The passive PFC filter circuit mainly consists of a small microhenry inductor connected in series with the full-wave rectifier circuit and a capacitor connected in parallel at the output end of the microhenry inductor. Although it effectively improves the power factor and filters out grid noise, this simple, low-cost passive PFC uses a small microhenry inductor that is generally only a few microhenries to tens of microhenries, so the DC output ripple is large, the DC voltage across the filter capacitor is also low, and the ability to correct current distortion and compensate power factor is very poor. After testing, the power factor is only 0.437, and the AC hum will seriously interfere with the sound quality of the audio. Utility Model Content

[0003] In order to solve the above-mentioned defects existing in the passive PFC filter circuit adopted in the existing tube power amplifier switching power supply, the utility model improves the existing circuit structure and important component parameters, and provides a filter circuit of the tube power amplifier switching power supply with improved power factor and low background noise.

[0004] To achieve the above purpose, the technical solution adopted by the utility model is: a filter circuit of a switching power supply of an electron tube power amplifier, comprising an AC filter circuit, a full-wave rectifier circuit for converting industrial frequency AC power into DC power, and a DC filter circuit, wherein the AC input end of the full-wave rectifier circuit is connected to the AC filter circuit through the AC filter circuit, and the DC output end of the full-wave rectifier circuit is connected to the DC filter circuit; the full-wave rectifier circuit comprises a bridge rectifier bridge or an integrated rectifier bridge composed of four diodes; its characteristic is that: the DC filter circuit is a π-type DC filter circuit, the π-type DC filter circuit comprises a first DC filter capacitor and a second DC filter capacitor, both of which are connected in parallel between the output ends of the rectifier bridge, the industrial frequency inductor is connected in series with the positive pole of the DC output end of the bridge rectifier bridge or the integrated rectifier bridge, and the first DC filter capacitor and the second DC filter capacitor are respectively connected in parallel to the two ends of the industrial frequency inductor; wherein the inductance parameter of the industrial frequency inductor is 0.5mH~500mH.

[0005] Furthermore, the AC filter circuit is a π-type AC filter circuit, which includes a first AC filter capacitor, a second AC filter capacitor, and a first common-mode inductor; the first AC filter capacitor is connected in parallel to the power input end of the first common-mode inductor, and the second AC filter capacitor is connected in parallel to the power output end of the first common-mode inductor.

[0006] Working principle: After the circuit is powered on, it is rectified and filtered through the π-type AC filter circuit, full-wave rectifier circuit, and π-type DC filter circuit to obtain a 320V DC voltage, and after high-frequency chopping through the subsequent switching power supply, the high-frequency AC power required by the tube amplifier filament is obtained at the output end of the switching power supply. More specifically, in the π-type DC filter circuit, after the small-capacity first DC filter capacitor behind the integrated rectifier bridge, the large inductor, the power frequency inductor, is connected, and then filtered through the large-capacity filter capacitor, the second DC filter capacitor, to obtain a high-purity DC power supply of about 320V, and after high-frequency chopping through the subsequent switching power supply, the high-frequency AC power supply is obtained at the output end of the switching power supply to power the tube amplifier. After the π-type DC filter circuit uses the large-capacity inductor, the power factor is increased to above 0.67, which not only improves the power factor of the circuit but also reduces the noise floor of the amplifier to a very low level.

[0007] It can be seen from the above that, compared with the prior art, the utility model has the following advantages: the filter circuit of the switching power supply of the electronic tube amplifier adopts a "double π-type" filtering method of a π-type AC filter circuit and a π-type DC filter circuit, the circuit structure is simple, efficient, and reasonably designed. In the π-type DC filter circuit, the industrial frequency inductor adopts a large inductor of the millihenry level, the DC output ripple is small, the DC voltage across the filter capacitor is also high, and the ability to correct current distortion and compensate power factor is improved, thereby effectively improving the power factor of the switching power supply of the electronic tube amplifier, and also reducing the background noise level of the amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a circuit diagram of a preferred embodiment of the present invention;

[0009] Figure 2 This is a circuit diagram of a preferred embodiment 1 of the present utility model;

[0010] Figure 3 This is a circuit diagram of the second preferred embodiment of the present utility model. DETAILED DESCRIPTION

[0011] The present invention and its beneficial technical effects are further described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0012] It should be noted that the descriptions of "first", "second", etc. in the present utility model are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the technical features.

[0013] Implementation method 1: See Figure 1~Figure 2The filter circuit of the electronic tube power amplifier switching power supply preferably implemented in the utility model comprises an AC filter circuit 11, a full-wave rectifier circuit 12 for converting industrial frequency AC power into DC power, and a DC filter circuit 13. The AC input end of the full-wave rectifier circuit 12 is connected to the AC filter circuit 11 through the AC filter circuit 11, and the DC output end of the full-wave rectifier circuit 12 is connected to the DC filter circuit 13; the full-wave rectifier circuit 12 comprises a bridge rectifier bridge or an integrated rectifier bridge DB1 composed of four diodes; the DC filter circuit 13 is a π-type DC filter The circuit, the π-type DC filter circuit, includes a power frequency inductor L2, a first DC filter capacitor EC1, and a second DC filter capacitor EC2, which are all connected in parallel between the output end of the rectifier bridge DB1. The power frequency inductor L2 is connected in series with the positive pole of the DC output end of the bridge rectifier or the integrated rectifier bridge DB1. The first DC filter capacitor EC1 and the second DC filter capacitor EC2 are respectively connected in parallel at both ends of the power frequency inductor L2; wherein, the inductance parameter of the power frequency inductor L2 is 0.5mH~500mH. The inductance parameter of the power frequency inductor L2 can be selected within the range of 0.5mH~500mH according to the use requirements, and generally the larger the better; the larger the inductance parameter, the larger the volume of the power frequency inductor L2. At this time, the appropriate power frequency inductor L2 can be selected according to the internal space of the power amplifier. The larger the inductance parameter of the power frequency inductor L2, the better.

[0014] Preferably, the AC filter circuit 11 is a π-type AC filter circuit, which includes a first AC filter capacitor C1, a second AC filter capacitor C2, and a first common-mode inductor L1; the first AC filter capacitor C1 is connected in parallel to the power input end of the first common-mode inductor L1, and the second AC filter capacitor C2 is connected in parallel to the power output end of the first common-mode inductor L1.

[0015] Preferably, a third DC filter capacitor EC5 for filtering high-voltage DC is connected in parallel across the second DC filter capacitor EC2.

[0016] Preferably, a fuse FU1 is connected in series to the busbar at the live input end of the first common-mode inductor L1.

[0017] Preferably, a recoverable fuse FU2 is connected in series to the power supply neutral line input terminal bus of the first common mode inductor L1, and the current protection action parameter of the recoverable fuse FU2 is smaller than the current protection action parameter of the fuse FU1.

[0018] See also Figure 2In the circuit, the AC filter circuit 11 is connected to the mains 10 such as 230V AC, the first AC filter capacitor C1 and the second AC filter capacitor C2 are X capacitors, the first common mode inductor L1 is a common mode inductor, the first common mode inductor L1 and the first AC filter capacitor C1 and the second AC filter capacitor C2 form a π-type circuit, the third capacitor C3 and the fourth capacitor C4 are Y capacitors, the rectifier bridge DB1 is a full-wave rectifier bridge, the first DC filter capacitor EC1, the second DC filter capacitor EC2 and the third DC filter capacitor EC5 are high-voltage resistant filter capacitors.

[0019] Implementation method 2: See Figure 3 This embodiment is further optimized on the basis of the first embodiment. The π-type AC filter circuit also includes a third AC filter capacitor C3 and a fourth AC filter capacitor C4 for filtering out common-mode interference on the bus. The third AC filter capacitor C3 and the fourth AC filter capacitor C4 are respectively connected in parallel between the bus at the power output end of the first common-mode inductor L1 and the ground wire. The ground wire here refers to the chassis ground, which is used to filter out common-mode interference on the bus near the AC input end of the full-wave rectifier circuit 12.

[0020] The usage and working principle are as follows: Select the component parameters according to the actual situation. Figure 2 or Figure 3 The circuit diagram is made into a circuit board and installed in the electron tube amplifier; the power frequency inductor L2 is relatively large in size and can be fixed near the circuit board in an external manner and connected to the circuit board through a plug. After the circuit is powered on, the current passes through the fuse FU1 and then through the π-type AC filter circuit and the third AC filter capacitor C3 and the fourth AC filter capacitor C4 to filter out burr interference, and then after being rectified by the rectifier bridge DB1, it is filtered and flattened by the π-type DC filter circuit and the fifth capacitor C5, and a 320V DC voltage is obtained at the DC output 14. After high-frequency chopping by the subsequent switching power supply, the high-frequency AC power required for the filament of the electron tube amplifier is obtained at the output end of the switching power supply.

[0021] The innovation of the utility model lies in the application of π-type DC filter circuit. After the π-type DC filter circuit adopts the high-inductance power frequency inductor, the power factor is increased to above 0.67, which not only improves the power factor of the circuit but also reduces the background noise of the power amplifier to a very low level. In the above description, the specific models and parameters of the components selected in the circuit can be matched and adjusted according to the actual use situation, which belongs to the commonly used technology in the prior art. In order to save space, the content that is conventionally used in the prior art, such as structure and process, will not be repeated. The processing technology and parts that are not disclosed can be processed according to the conventional technology of the prior art.

[0022] The above description and specific embodiments do not constitute any limitation to the present invention. The present invention is not limited to the specific implementation methods disclosed and described above. The control ideas and methods of the present invention may be implemented or transformed in different ways, which should also fall within the protection scope of the claims of the present invention.

Claims

1. A filter circuit for a switching power supply of an electron tube power amplifier, comprising an AC filter circuit (11), a full-wave rectifier circuit (12) for converting industrial frequency AC power into DC power, and a DC filter circuit (13), wherein an AC input end of the full-wave rectifier circuit (12) is connected to the AC filter circuit (11) through the AC filter circuit (11), and a DC output end of the full-wave rectifier circuit (12) is connected to the DC filter circuit (13); the full-wave rectifier circuit (12) comprises a bridge rectifier or an integrated rectifier bridge (DB1) composed of four diodes; and the characteristics are: The DC filter circuit (13) is a π-type DC filter circuit, comprising a power frequency inductor (L2), a first DC filter capacitor (EC1), and a second DC filter capacitor (EC2), all of which are connected in parallel between the output end of the rectifier bridge (DB1); the power frequency inductor (L2) is connected in series with the positive electrode of the DC output end of the bridge rectifier or the integrated rectifier bridge (DB1); the first DC filter capacitor (EC1) and the second DC filter capacitor (EC2) are respectively connected in parallel at both ends of the power frequency inductor (L2); wherein the inductance parameter of the power frequency inductor (L2) is 0.5mH~500mH.

2. The filter circuit of the switching power supply of the electron tube power amplifier as claimed in claim 1, characterized in that: The AC filter circuit (11) is a π-type AC filter circuit, comprising a first AC filter capacitor (C1), a second AC filter capacitor (C2), and a first common mode inductor (L1); the first AC filter capacitor (C1) is connected in parallel to a power input end of the first common mode inductor (L1), and the second AC filter capacitor (C2) is connected in parallel to a power output end of the first common mode inductor (L1).

3. The filter circuit of the switching power supply of the electron tube power amplifier as claimed in claim 2, characterized in that: The π-type AC filter circuit also includes a third AC filter capacitor (C3) and a fourth AC filter capacitor (C4) for filtering common-mode interference on the busbar. The third AC filter capacitor (C3) and the fourth AC filter capacitor (C4) are respectively connected in parallel between the power output end busbar of the first common-mode inductor (L1) and the ground line.

4. The filter circuit of the switching power supply of the electron tube power amplifier as claimed in claim 1, 2 or 3, characterized in that: A third DC filter capacitor (EC5) for filtering high-voltage DC is connected in parallel to both ends of the second DC filter capacitor (EC2).

5. The filter circuit of the switching power supply of the electron tube power amplifier as claimed in claim 2, characterized in that: A fuse (FU1) is connected in series to the busbar at the live input end of the power supply of the first common mode inductor (L1).

6. The filter circuit of the switching power supply of the electron tube power amplifier as claimed in claim 5, characterized in that: A resettable fuse (FU2) is connected in series to the power supply neutral line input end bus of the first common mode inductor (L1), and the current protection action parameter of the resettable fuse (FU2) is smaller than the current protection action parameter of the fuse (FU1).

Images