JPH022077Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a power supply smoothing circuit with a ground plate suitable for a power supply smoothing circuit for a low frequency amplifier.

Conventionally, the first power supply smoothing circuit for low frequency amplifiers
As shown in the figure, an AC voltage is applied between terminals 1 and 2 of the primary coil of the power transformer T, and an AC voltage of a desired value is obtained between terminals 3 and 4 of the secondary coil. For example, the + terminal of the first power supply smoothing electrolytic capacitor C1 is connected to the first output terminal 6 of the rectifier circuit RCT consisting of, for example, diodes D1 and D2 connected to The - terminals of the electrolytic capacitors C2 are connected to each other, and the - terminals 7 and + terminals 8 of the first and second power supply smoothing capacitors C1 and C2 are respectively led out from the middle point 5 of the secondary coil of the power transformer T. A power supply smoothing circuit has been proposed that is connected to the ground common terminal 10.

This power supply smoothing circuit is a well-known half-wave rectifier circuit that obtains DC outputs with a phase difference of 180 degrees, and DC outputs +B and -B are obtained between the output terminals 6 and 9, respectively, and the common terminal 10. be.

Low frequency amplifier AMP using this power supply smoothing circuit
To operate the low frequency amplifier AMP, connect output terminal 6 to terminal 11, output terminal 9 to terminal 12,
In addition, one terminal of the speaker coil L of the speaker SP is connected to the terminal 13, and the input signal terminal 1 is connected to the terminal 14.
5 and further connect the other terminal 16 of the speaker coil L to the common terminal 10, respectively. As a result, DC outputs +B and -B are supplied to terminals 11 and 12,
For example, PHONO, TAPE from input signal terminal 15
A low frequency input such as the following is amplified by the low frequency amplifier AMP and output from the speaker SP.

In this case, the load current +Il flowing through the speaker coil L and the charging current +In flowing through the power supply smoothing electrolytic capacitor C1 are both common terminal 10 - - terminal 7 of the power supply smoothing electrolytic capacitor C1 - Output terminal Similarly, the load current -Il flowing through the speaker coil L and the charging current -In flowing through the power supply smoothing electrolytic capacitor C2 are connected to the common terminal 10-power supply smoothing electrolytic capacitor C2. + terminal 8 of capacitor C2 - power supply smoothing electrolytic capacitor C2 - output terminal 9
It flows along the path shown by the arrow.

However, as shown in FIG. 2, each of the above-mentioned charging currents +In and -In includes rectification noise of the diodes D1 and D2, which is shown by a steep high peak value at the initial stage of the charging current.

Therefore, the load current +Il and -Il are the charging current +In
and -In are interfered with or cross-modulated by the above-mentioned rectification noise, and the low-frequency output from the speaker SP is obtained as if the above-mentioned rectification noise has been mixed, which has the drawback of degrading the sound quality. .

The present invention was made to eliminate the above-mentioned drawbacks of the conventional technology, and uses a grounding plate having a hollow part to separate the charging current containing the rectification noise of the rectifier flowing into the smoothing capacitor and the load current flowing into the speaker coil. The purpose of this is to provide a novel power supply smoothing circuit with a ground plate, in which the load current flowing through the speaker coil is prevented from being interfered with or cross-modulated by the charging current including rectification noise by conducting through separate paths, and is shown in the drawings below. This is explained by:

FIG. 3 shows a circuit diagram of an embodiment of the power supply smoothing circuit with a ground plate according to the present invention. The same parts as those in FIG. L terminal 1
6 and - terminal 7 of power supply smoothing electrolytic capacitor C1
and the + terminal 8 of the power supply smoothing electrolytic capacitor C2 are connected to a grounding plate 17 having a hollow part 18 made of copper or aluminum so as to be orthogonal to each other with the hollow part 18 in between. It has the same configuration as that in FIG. That is, the - terminals 7 and + terminals 8 of the power supply smoothing electrolytic capacitors C1 and C2 sandwich the hollow part 18 of the ground plate 17.
Similarly, the common terminal 10 and the terminal 16 of the speaker coil L are connected to the terminals c and d of the grounding plate 17 with the hollow part 18 of the grounding plate 17 sandwiched therebetween. Note that these terminals a,
b, c, and d are located in the middle of each side of the ground plate 17, and the terminal a is connected to the ground plate 17 so that the line connecting terminals a and b is orthogonal to the line connecting terminals c and d, sandwiching the hollow part 18. , b, c, and d are arranged.

Therefore, the charging current +In of the power supply smoothing electrolytic capacitor C1 described above is connected to the terminal a- at the ground plate 17.
The current is divided into a path of terminal c (common terminal 10) and a path of terminal a-terminal d-terminal b-terminal c (common terminal 10). In this case, since the impedance of the former path is approximately 1/3 of the impedance of the latter path, approximately 3/4 of the charging current +In flows through the former path from terminal a to terminal c.

In this case, approximately 3/4 of the charging current +In flows through the path from terminal a to terminal c, including the rectification noise exhibiting the steep high peak value described above in FIG. The inventor has confirmed that approximately 1/4 of the charging current +In flows through the path c, including rectification noise that exhibits a much lower peak value than that shown in Figure 2, as shown in Figure 4. There is.

Note that the load current +I flows through the path between terminal d and terminal a on the ground plate 17.
Therefore, the degree to which the load current +I is interfered with or cross-modulated by the rectification noise caused by the diode D1 of the charging current +In can be greatly reduced compared to the conventional case shown in FIG. In addition, the charging current -In of the power supply smoothing electrolytic capacitor C2 mentioned above is also connected between terminals b and c (common terminal 10) on the ground plate 17.
Since the current is divided into the path from terminal b to terminal d to terminal a to terminal c (common terminal 10), approximately 3/4 of the charging current -In is divided into the path from terminal B to terminal D to terminal A to terminal C (common terminal 10). In FIG. 2, the rectification noise exhibiting the steep high peak value described above flows through the path of low impedance between terminal b and terminal c, and the terminal b and
Approximately 1/4 of the charging current -In is on the high impedance path from terminal d to terminal a to terminal c, and rectification noise having a significantly lower peak value than that shown in Fig. 2 as shown in Fig. 4 is generated. It contains and flows. Therefore, the load current -Il flowing through the path from terminal b to terminal d of the ground plate 17 is also equal to the diode D2 of the charging current -In.
The degree of interference or cross-modulation caused by rectification noise caused by this can be greatly reduced compared to the conventional case shown in FIG.

Furthermore, the use of the grounding plate 17 means that the grounding plate 17 is a surface grounding, as opposed to the conventional point grounding shown in FIG. This can further prevent mutual interference from occurring.

In the above description, a half-wave rectifier circuit using a rectifier RCT with diodes D1 and D2 has been described as an example, but it goes without saying that the same applies to a full-wave rectifier circuit.

As described in detail above, the power supply smoothing circuit with a ground plate according to the present invention transfers the charging current including the rectification noise of the rectifier flowing into the power supply smoothing electrolytic capacitor through the ground plate having a hollow part, and the impedance of the ground plate. This causes most of the charging current, which contains rectification noise with a steep high peak value, to be diverted to the path with low impedance, and the majority of the charging current, which contains rectification noise with a steep peak value, is diverted to the path with high impedance, and the majority of the charging current is diverted to the path with high impedance, which contains rectification noise with a steep peak value. Therefore, interference or cross-modulation caused by rectification noise of the charging current to the load current flowing through the high impedance path of the ground plate can be significantly reduced compared to conventional methods. It has great characteristics.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional power supply smoothing circuit, Fig. 2 is a charging current waveform diagram of a power supply smoothing electrolytic capacitor including rectification noise of a rectifier, and Figs. 3 and 4 are diagrams with a ground plate according to the present invention. FIG. 2 is a circuit diagram illustrating a power supply smoothing circuit and a charging current waveform diagram of a power supply smoothing electrolytic capacitor including rectification noise of a rectifier which is shunted to the load terminal side of a ground plate. T...power transformer, RCT...rectifier, D1,
D2...Diode, C1, C2...Power supply smoothing electrolytic capacitor, AMP...Low frequency amplifier, SP...
...Speaker, L...Speaker coil, 1, 2
...Primary coil terminals of power transformer T, 3, 4...
... Secondary coil terminal of power transformer T, 5 ... Secondary coil midpoint terminal of power transformer T, 6, 9 ... Output terminal of diodes D1, D2, 10 ... Common terminal, 15 ... Low frequency input terminal , 17...Earth plate, 18...Hollow part, a, b, c, d...Terminal of earth plate 17.

Claims (1)

[Scope of utility model registration request] One terminal of the first power supply smoothing capacitor is connected to the first output terminal of the rectifier circuit connected to both ends of the secondary coil of the power transformer, and the second terminal is connected to the second output terminal of the rectifier circuit.
One terminal of the first power supply smoothing capacitor and the second terminal of the second power supply smoothing capacitor are respectively connected to a ground plate having a hollow part, symmetrically with the hollow part in between. A common terminal connected to the middle point of the secondary coil of the power transformer and a load side terminal of the low frequency amplifier are connected to the ground plate of the first and second power supply smoothing capacitors. A power supply smoothing circuit with a ground plate, characterized in that the circuit is connected across the hollow part at right angles to the lines connecting the connected terminals.