JPH0349556A - Power source circuit - Google Patents

Abstract

PURPOSE:To prevent the mutual influence between a main power source and a power source for audio outputs by supplying power source voltage to a power source circuit for audio during the ON period of a switching transistor and supplying it to the main power source circuit during the OFF period. CONSTITUTION:When a switching transistor 4 turns on, in a power source circuit 5 for audio, the output of the secondary winding 7 of a switching transformer is converted into DC voltage. And, this DC power source voltage is supplied to an audio load 10. Accordingly, power is supplied to the audio load 10 while the switching transistor 4 is on. Incidentally, energy is stored in the primary winding 6 of the switching transformer during this ON period. While, in a main power source circuit, the energy stored in the primary winding 6 is converted into DC voltage with a smoothing capacitor 3 through a rectifier diode 2 and supplied to a main load 11. This prevents the mutual influence between the side of the power source circuit 5 for audio and that of the main power source circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply circuit suitable for use in television receivers and the like.

[Conventional technology]

In the power supply circuit used in television receivers,
A DC power supply voltage is generated by rectifying the commercial AC voltage, and the power supply voltage for audio output is also output from this power supply circuit.

Another example of a conventional power supply circuit is a switching transformer that supplies the main power supply voltage to the main power supply circuit and the audio power supply voltage to the audio power supply circuit during the OFF period of the switching transistor. There is something.

[Problem to be solved by the invention]

However, in the former conventional technology, when there is a change in the audio output, the main power supply voltage generated in the main power supply circuit changes due to the change in the audio output. In order to reduce the power supply voltage to 1-}, a voltage drop resistor is used, which poses the problem of large power loss.

In addition, in the latter conventional technology, a winding (secondary winding) for the audio output power supply is added to the switching transformer, eliminating the need for a voltage drop resistor. Since the main power supply voltage is simultaneously supplied to the main power supply circuit during the period, and the audio power supply voltage is supplied to the audio power supply circuit at the same time, there is a problem in that audio load fluctuations tend to affect the main power supply voltage.

An object of the present invention is to solve this problem and provide a power supply circuit in which the main power supply and the audio output power supply do not influence each other.

[Means to solve the problem]

In order to achieve the above object, the present invention supplies a power supply voltage to an audio power supply circuit during an ON period of a switching transistor, and supplies a power supply voltage to a main power supply circuit during an OFF period of a switching transistor.

[Effect]

When the switching transistor is ON, power is stored in the switching transformer, and at the same time, power is supplied to the audio power source via the transformer-coupled secondary winding. At this time, no power is being supplied to the main power source. When the switching transistor is turned off, the power stored in the switching transformer is supplied to the main power source.

As a result, power is alternately supplied to the audio output side and the main power supply side, so that even if there is a load change in the audio, the main power supply is not affected by this.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a power supply circuit according to the present invention, where l is a primary power supply, 2 is a rectifier diode, 3 is a smoothing capacitor, 4 is a switching transistor, 5 is an audio power supply circuit, and 6 is a power supply circuit for audio. Primary side of switching transformer, 7
8 is a rectifier diode, 9 is a smoothing condenser, 10 is an audio load, 11 is a main load, and 12 is a drive circuit.

In the figure, a closed loop is formed between the switching transistor 4 and the primary winding 6 of the switching transformer, and the energy stored in the primary winding 6 of the switching transformer is transferred from the secondary winding 7 of the switching transformer to the primary winding 7. Loops are formed to take out the load 11, and these loops constitute a power supply circuit as a switching regulator circuit. The smoothing capacitor 3 transfers the energy stored in the switching I lance to the rectifier diode 2.
After being rectified through the DC voltage, it is smoothed to generate a DC main power supply voltage.

In the audio power supply circuit 5, when the switching transistor 4 is turned on, the output of the secondary winding 7 of the switching transformer is converted into DC by the rectifier diode 8 and the smoothing capacitor 9. This DC power supply voltage is supplied to an audio load 10 connected in parallel to a capacitor 9. Therefore, power is supplied to the audio load 1o while the switching transistor 4 is ON. Note that during this period, energy is accumulated in the secondary winding 6 of the switching transformer.

On the other hand, in the main power supply circuit, when the switching transistor 4 is turned OFF, the energy stored in the primary winding 6 is converted into direct current by the smoothing capacitor 3 via the rectifier diode 2, and is supplied to the main load 11. As described above, since power is supplied to the main load 11 and the audio load alternately, the mutual influence between the audio power supply circuit side and the main power supply circuit side is lost.

Also, the energy stored in the primary winding 6 of the switching transformer is taken out via the secondary winding 7, but at this time, the switching transistor 4 is turned on and the energy is transferred from the primary power supply 1 to the primary winding 6 of the switching transistor. Since energy is supplied to the main load 11, sufficient energy is stored in the next winding 6 when energy is supplied to the main load 11.

FIG. 2 is a circuit diagram showing another embodiment of the power supply circuit according to the present invention, in which parts corresponding to those in FIG.

In this embodiment, the primary winding 6 of a switching transformer for coupling the audio power supply circuit 5 is connected in series with the main load, and the same effects as the embodiment shown in FIG. 1 can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the timing of supplying the power supply voltage to the main power supply circuit and the timing of supplying the power supply voltage to the audio power supply circuit are made different from each other, so that fluctuations in the audio load are caused by fluctuations in the main power supply. The voltage is not transmitted to the circuit, and a stable power supply voltage can be obtained.

[Brief explanation of drawings]

FIGS. 1 and 2 are circuit diagrams showing embodiments of power supply circuits according to the present invention, respectively. DESCRIPTION OF SYMBOLS 1... Primary power supply, 2... Rectifier diode, 3... Smoothing capacitor, 4... Switching transistor, 5... Audio power supply circuit, 6... Primary winding of switching transformer, 7 ... Secondary winding of switching transformer, 8 ... Rectifier diode, 9 ... Smoothing capacitor, 10 ... Audio load. Hanawa 1 Hanawa 2 Nagi

Claims (1)

[Claims] 1. The output voltage of the primary power supply is supplied and turns on at a predetermined period,
In a power supply circuit including a switching transistor that is turned off and an inductance element that stores energy of the output voltage of the switching transistor and supplies the stored energy to a load while the switching transistor is off, the inductance element is used as a primary winding. A switching transformer having a secondary winding is provided opposite to the primary winding, and the energy stored in the primary winding of the switching transformer can be taken out from the secondary winding. A power supply circuit featuring: