JPH028554Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to the improvement of a power supply circuit, and its purpose is to prevent deterioration of the S/N ratio due to harmonic components of a capacitor charging current in the power supply circuit.

Conventionally, the diode accumulated charge absorbing capacitor C1 shown in FIG. ₁ was intended to absorb electromagnetic plates of 100 KHz or higher.

In Fig. 1, 1 is a power transformer, D ₁ ,
D ₂ is a forward and reverse diode, C ₂ is a smoothing capacitor, and a positive DC voltage is obtained at terminal a and a negative DC voltage is obtained at terminal b.

In the above configuration, C ₁ is intended to absorb electromagnetic waves of 100KHz or higher as mentioned above, but on the other hand, the output current waveform of the rectifier circuit (diodes D ₁ and D ₂ ) flows only when diodes D ₁ and D ₂ are conductive. It is an audio frequency band because it has a pulsed waveform.
The effect was not sufficient to suppress S/N deterioration of the amplifier circuit due to high frequency components of 120 Hz (when the input AC wave number is 60 Hz) or higher.

Therefore, in this invention, the harmonic components of the rectified current are removed by constructing a filter circuit with a capacitor using the inductance of the secondary winding of the power transformer 1.Example will be explained in detail below. explain.

Figure 2 shows the first embodiment circuit of this invention, in which 1 is a power transformer, D ₁ and D ₂ are diodes, C ₂ is a smoothing capacitor, a is a + DC output end, and b is a - DC output end. .

Intermediate tap d of secondary winding 1b of power transformer 1
is connected to the common connection end of capacitor C ₂ . The above configuration is the same as the conventional example shown in FIG.

C ₃ (0.22 μF) is a capacitor connected between taps f and g formed between the winding start end c and the intermediate tap d, and between the intermediate tap d and the winding end e, respectively, of the secondary winding 1b.

In the equivalent circuit of such a circuit configuration, as shown in FIG. 4, a low-pass filter is formed by the inductance of the power transformer and the capacitor _C3 . Note that R is the load.

Therefore, tap f is applied so that the harmonic components are attenuated by the attenuation characteristics of the low-pass filter.
Noise can be suppressed by selecting the extraction position of g and the value of the capacitor.

FIG. 3 shows the second embodiment, in which capacitors C ₄ (0.47 μF) and C ₄ (0.47 μF) are connected between tap f and intermediate tap d, and between tap g and intermediate tap d, respectively. The equivalent circuit is shown in FIG. 5, and a noise suppressing effect can be obtained by the same action.

As explained above, in a power supply circuit consisting of at least a power transformer, a rectifier circuit, and a smoothing circuit, a tap is formed in the secondary winding of the power transformer, and a capacitor connected to the tap is connected to the secondary winding. It is characterized by forming a filter with the inductance of the winding, and has the effect of removing harmonics of the rectified current and improving the S/N ratio of the amplifier.

Although this invention has been described with respect to a power supply circuit that can obtain positive and negative DC voltages, it is clear that it can also be applied to a power supply circuit that can obtain only positive or negative outputs.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram of a conventional power supply circuit, Figures 2 and 3 are wiring diagrams of a power supply circuit according to an embodiment of this invention, and Figures 4 and 5 are equivalent to Figures 2 and 3, respectively. It is a circuit diagram.

Claims (1)

[Scope of utility model registration request] In a power supply circuit having at least a power transformer, a rectifier circuit, and a smoothing circuit, a tap is formed in the secondary winding of the power transformer, and a filter circuit is formed by a capacitor connected to the tap and the inductance of the secondary winding. A power supply circuit featuring: