JP2563607Y2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a power supply device suitable for use in an electronic device such as an audio device or a video device.

2. Description of the Related Art As a power supply device used for an electronic device such as an audio device or a video device, for example, a power supply device shown in FIG.

In brief, 1 is an AC power supply, 2 is a rectifying element, 3 is a smoothing capacitor, and 4 is a load. Reference numeral 5 denotes an impedance control circuit, which is interposed between the positive terminal of the smoothing capacitor 3 and one end of the load 4. 6a and
6b is a resistor connected in series to both ends of the load 4. 7a and 7b are output terminals of the DC power supply.

The voltage at the connection point of the resistors 6a and 6b is fed back to the impedance control circuit 5, and the impedance is controlled according to the load voltage, so that the voltage applied to the load 4 is controlled to be always constant.

As is well known, the voltage after being rectified by the rectifying element 2 has a pulsating waveform, which is smoothed by the smoothing capacitor 3, but cannot be completely smoothed. As shown in FIG.

Therefore, conventionally, the impedance control circuit 5 controls the voltage (E) equal to or lower than the voltage (V) including the ripple component to be applied to the load 4.
Therefore, a constant DC voltage E from which a ripple component is removed is always applied to the load 4.

[Problem to be Solved by the Invention] According to the configuration of FIG. 2, only the power below the voltage E shown in FIG. Are configured to be consumed by the resistance component in the impedance control circuit 5. That is, there is a drawback that power is consumed wastefully.

Therefore, in the present invention, the power that is wasted is reduced.

[Means for Solving the Problems] The present invention provides a smoothing capacitor connected to the output side of a rectifying element, a series circuit of a first switching element and a replenishing capacitor connected in parallel with the smoothing capacitor. A second switching element connected in parallel with the first switching element, and a comparison circuit for comparing the output voltage of the smoothing capacitor with a reference voltage.

When the output voltage of the smoothing capacitor is higher than the reference voltage, the first switching element is turned on by the output of the comparison circuit, and the replenishment capacitor is charged by the smoothing capacitor.

When the output voltage of the smoothing capacitor is lower than the output voltage of the supplementary capacitor, the second switching element is turned on, and power is supplied to the load from the supplementary capacitor in addition to the smoothing capacitor. Things.

[Operation] When the output voltage of the smoothing capacitor becomes higher than the reference voltage, the replenishment capacitor is charged by the smoothing capacitor, and the output voltage of the smoothing capacitor is controlled to decrease.

When the load increases and the output voltage of the smoothing capacitor becomes lower than the output voltage of the replenishing capacitor, power is supplied to the load from the replenishing capacitor in addition to the smoothing capacitor. Control is performed so that the output voltage of the capacitor increases.

As a result, the voltage supplied to the load is stabilized so as to have a constant value, and the power is used effectively.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 2 are denoted by the same reference numerals.

In the figure, 1 is an AC power supply, 2 is a rectifying element, 3 is a smoothing capacitor, and 4 is a load. For convenience of explanation, the lines from the positive terminal and the negative terminal of the smoothing capacitor 3 to the load 4 are referred to as a positive line 3a and a negative line 3b.

A resistor 8 and a constant voltage element 9 such as a Zener diode are connected between the positive line 3a and the negative line 3b. A connection point between the resistor 8 and the low voltage element 9 is connected to a negative input terminal of the comparison circuit 11. , The positive line 3 a is connected to the positive input terminal of the comparison circuit 11 via the resistor 10.

The output terminal of the comparison circuit 11 is connected to the base of an npn transistor 12 as a switching element. The collector of this transistor 12 is connected to the positive line 3a, the emitter is connected to the negative line 3b through the replenishing capacitor 13, and the connection point between the emitter and the replenishing capacitor 13 is connected to the anode of a diode 14 as a switching element. , Its cathode is connected to the positive line 3a.

The set voltage (zener voltage) E of the low-voltage element 9 is selected to be equal to the load voltage required by the load 4.

In a normal operating state without overload, the voltage V obtained across the smoothing capacitor 3 is equal to the load voltage E described above.
The voltage of the AC power supply 1 or the like is selected so as to be larger.

 Next, the operation will be described.

In a normal operation state, the voltage V of the smoothing capacitor 3 is larger than the set voltage (load voltage) E of the constant voltage element 9 (V>
E). At this time, the positive input terminal voltage of the comparison circuit 11 becomes higher than the negative input terminal voltage, the output of the comparison circuit 11 becomes high level, and the transistor 12 is turned on.

Therefore, current flows from the smoothing capacitor 3 to the supplementary capacitor 13 through the collector-emitter of the transistor 12, and the supplementary capacitor 13 is charged. That is,
When V> E, a portion higher than the voltage E indicated by oblique lines in FIG.

Thus, the replenishing capacitor 13 is used as the smoothing capacitor 3.
, The voltage of the smoothing capacitor 3 decreases to reach the set voltage E.

When the load 4 suddenly increases from such a normal operation state, for example, when a large volume is generated in an audio device, a large amount of electric power is required instantaneously, and the charge of the smoothing capacitor 3 alone cannot cover the load. The output voltage of the smoothing capacitor 3, that is, the voltage between the output terminals 7a and 7b decreases.

At this time, when the cathode voltage of the diode 14 becomes lower than the anode voltage, the diode 14 is turned on, the electric charge charged in the replenishing capacitor 13 is supplied to the load 4 through the diode 14, and the output voltage of the smoothing capacitor 13 decreases. Be avoided.

As described above, in this example, the voltage between the output terminals 7a and 7b is always stabilized, so that sufficient power can be supplied to the load 4 and the power that has been wasted for stabilization is effectively used. Used for

[Effects of the Invention] As described above, according to the invention, the replenishment capacitor is charged and discharged in accordance with the output voltage of the smoothing capacitor to stabilize the load voltage. As a result, the power of the ripple component, which has been wasted, is charged in the replenishing capacitor, and is effectively used as the replenishing power when the load becomes large, so that the unnecessary power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a power supply device, and FIG. 3 is a waveform diagram for explaining its operation. 2 Rectifying element 3 Smoothing capacitor 4 Load 9 Constant voltage element 11 Comparison circuit 12 Transistor 13 Replenishment capacitor 14 Diode

Claims (1)

(57) [Scope of request for utility model registration] 1. A smoothing capacitor connected to an output side of a rectifying element, a series circuit of a first switching element and a replenishing capacitor connected in parallel with the smoothing capacitor, and a first switching element. A second switching element connected in parallel; and a comparison circuit for comparing the output voltage of the smoothing capacitor with a reference voltage. When the output voltage of the smoothing capacitor is higher than the reference voltage, The first switching element is turned on by the output, and the replenishment capacitor is charged by the smoothing capacitor. When the output voltage of the smoothing capacitor becomes lower than the output voltage of the replenishment capacitor, the second switching is performed. The element is turned on, and the load is applied not only from the smoothing capacitor but also from the supplemental capacitor. Power supply, characterized in that power is supplied.