JPH09201050A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a power unit by improving the utilizing efficiency of electric power by obtaining a target voltage by supplying a voltage from a switching power source connected in series with a smoothing means by controlling the sum of the output voltage of the smoothing means and switching power source. SOLUTION: The voltage of commercial power supply 22 is supplied to both a power transformer 23 and a switching power supply 26. A diode bridge which works as a rectifying means 24 band a capacitor which works as a smoothing means 25 are connected to the secondary side of the transformer 23 and the output of the means 25 is connected in series with the output of the power supply 26. The power supply 26 obtains a Zener voltage V2 by supplying a voltage V1 . Since the power supply 26 is constituted to only part of a target voltage, no higher voltage than a really necessary voltage is required from the power supply 26 and electric power can be utilized very highly efficiently. Therefore, an expensive small-sized power supply can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device capable of supplying a DC voltage to a load.

[0002]

2. Description of the Related Art As a power supply device for supplying a constant DC voltage to a load, a power supply transformer shown in FIG. 7 and a switching power supply shown in FIG. 8 are generally used. ing. In the configuration shown in FIG. 7, after the commercial power supply 1 is connected to the primary side of the power transformer 2, the voltage on the secondary side of the power transformer 2 determined by the winding ratio is rectified by the diode bridge 3 and smoothed by the capacitor 4. The voltage V between the output terminals is adjusted to be a predetermined voltage by the transistor 6 constituting the series regulator. In this adjustment, the voltage drop amount by the transistor 6 is controlled so that the voltage obtained by dividing the output voltage V by the resistors 7 and 8 becomes equal to the reference voltage 10 by the amplifier 9. At this time, since the transistor 6 has a large amount of heat generation, the heat radiation fins 11 dissipate heat.

At this time, since the power transformer 2 is used, the voltage adjustment by the transistor 6 is required. That is, the voltage V between the output terminals is basically determined by the winding ratio of the power transformer 2, but naturally varies depending on the current flowing through the load and the voltage fluctuation of the commercial power supply 1 itself. In order to guarantee this variation, the capacitor 4 is
For example, double voltage is required at both ends.

In the configuration shown in FIG. 8, the commercial power supply 1 is rectified by the diode bridge 12, smoothed by the capacitor 13, and then the high frequency voltage obtained by high speed switching by the switching transistor 14 is applied to the primary side of the switching transformer 15. In addition, the voltage generated on the secondary side is applied to the diode 16
The output voltage V is rectified and smoothed by the capacitor 17. At this time, the output voltage of the capacitor 17 is controlled by the pulse width control circuit 21 so that the output voltage V becomes constant even if the current flowing through the load fluctuates. That is, when the output voltage V becomes higher than the Zener voltage of the Zener diode 18, a large amount of current flows to the light emitting side of the photocoupler 19 through the resistor 20 and the photocoupler 1
Since a large amount of current also flows to the light receiving side of 9, the pulse width control circuit 21 reduces the ON ratio of the switching transistor 14. On the other hand, when the output voltage V becomes lower than the Zener voltage, the current on the light receiving side of the photocoupler 19 decreases and the ON ratio of the switching transistor 14 increases. When the ON ratio of the switching transformer rises, the current flowing through the switching transformer 15 increases and the voltage charged in the capacitor 17 rises. When the ON ratio of the switching transformer decreases, the capacitor 17
The voltage charged to the voltage drops.

[0005]

The configuration using the power supply transformer 2 shown in FIG. 7 has a problem that the capacity of the power supply transformer 2 must be about twice the required capacity. There is. The configuration using the switching power supply shown in FIG. 8 has a problem that large-sized components such as the switching transistor 14 must be used.

The present invention solves the problems of such a conventional structure, and an object thereof is to provide a small-sized and inexpensive power supply device.

[0007]

The first means of the present invention for achieving the above object is to connect a commercial power source with a rectifying means and a smoothing means directly connected to the commercial power source or connected via a power transformer. A small and inexpensive power supply device is provided which has a switching power supply for switching and rectifying and rectifying it into a DC voltage, and uses the switching power supply to make up for only the shortage of the output of the smoothing means, with high power utilization efficiency.

A second means of the present invention is a DC power source,
The output includes a switching power supply connected in series with the output of the DC power supply, and the switching power supply compensates only the shortage of the output of the DC power supply to provide a more compact and inexpensive power supply device.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a circuit diagram showing an embodiment of the present invention. The voltage of the commercial power supply 22 is supplied to both the power supply transformer 23 and the switching power supply 26. Further, a diode bridge which is the rectifying means 24 and a capacitor which is the smoothing means 25 are connected to the secondary side of the power transformer 23, and the output of the smoothing means 25 is the switching power supply 2 described above.
6 are connected in series. Switching power supply 2
6 is a diode bridge 27 that rectifies the voltage of the commercial power supply 22, a capacitor 28 that smoothes this voltage, and a switching transistor 29 that is connected to the capacitor 28.
A switching transformer 30, a diode 31 and a capacitor 32 connected to the secondary side of the switching transformer 30, a pulse width control circuit 36 for driving the switching transistor 29, a photocoupler 34, and a light emitting side of the photocoupler 34. The zener diode 33 and the resistor 35 are included.

The operation of this embodiment will be described below.
Due to the high speed switching by the switching transistor 29, a high frequency voltage is applied to the primary side of the switching transformer 30 and a current flows. A high frequency voltage is induced on the secondary side of the switching transformer 30 by the power at this time, and this voltage is rectified by the diode 31 and charged by the capacitor 32. Capacitor 32
Is shown as V ₂ in the figure, and is connected in series with the output voltage V ₁ of the smoothing means 25 connected to the secondary side of the power transformer 23. Therefore, the output voltage of this device is V ₁
It becomes + V ₂ . At this time, in the present embodiment, the Zener voltage V _Z of the Zener diode 33 is set to V ₁ + V ₂ . Therefore, when the output voltage V ₁ + V ₂ becomes higher than the Zener voltage V _Z , a current flows through the resistor 35 according to the degree of increase. That is,
A current flows on the light emitting side of the photocoupler 34.
For this reason, the pulse width control circuit 36 connected to the output side of the photocoupler 34 includes the switching transistor 29
Are driven so that V ₁ + V ₂ becomes V _Z. That is, the ON ratio of the switching transistor 29 is reduced. When the ON ratio of the switching transistor is reduced, the current flowing through the switching transformer 30 is reduced and therefore the voltage charged in the capacitor 32 is also reduced. That is, the output V ₂ decreases. On the contrary, when the output voltage V ₁ + V ₂ becomes lower than the Zener voltage V _Z , the current flowing through the light emitting side of the photocoupler 34 decreases. Therefore, the pulse width control circuit 36 drives so as to increase the ON ratio of the switching transistor 29. When the ON ratio of the switching transistor 29 increases, the current flowing through the switching transformer 30 increases, and the voltage charged in the capacitor 32 also increases. That is, the output V ₂ rises.

As described above, in the present embodiment, as shown in FIG. 2, the output voltage V ₁ + V ₂ is always kept constant at the Zener voltage V _Z. That is, the switching power supply 26 acts so as to compensate for the shortage of V ₁ with respect to the Zener voltage V _Z.

As described above, since the switching power supply 26 of this embodiment has a circuit configuration for supplying only a part of the target voltage, it is about half or less than that of the configuration for supplying all the output voltage. The capacity is enough. Further, also in the power transformer 23, in the case of the configuration of the present embodiment, it is sufficient that it can output a voltage equal to or lower than the net required voltage, and it can be used with extremely high efficiency.

If the capacitor 25 of the smoothing means is not used, V ₁ will be as shown by the broken line in FIG. 2, but it does not matter because the switching power supply outputs the shortage with V _Z.

In this embodiment, the commercial power source 22 for input is used.
On the other hand, the switching power supply 26 is connected in parallel with the power supply transformer 23, but the power supply transformer 23 lowers the voltage, and the switching power supply 26 may be connected to the secondary side of the power supply transformer 23. For example, it is possible to use a component of the switching power supply 26 having a low withstand voltage, and it is possible to reduce the circuit cost.

When the output voltage V ₁ + V ₂ is 140 V or higher, it is not necessary to use the power transformer 23. In this case, the rectifying means 24 and the smoothing means 25
Can be shared by the diode bridge 27 and the smoothing capacitor 28, and a very simple structure can be realized.

If the circuit configuration is as shown in FIG. 3, it is possible to realize a power supply device in which the rectifying means 41 and the smoothing means 42 are shared and the configuration of the switching power supply can be simplified. The circuit of the switching power supply is called buck boost,
The feature is that the polarity of the output voltage V ₄ can be inverted, and the switching transformer 30 used in the configuration shown in FIG. 1 is not used. In this circuit, the switching power supply 43 is connected to the secondary side of the power transformer 40, that is, the output of the smoothing means 42 after the rectifying means 41. The switching power supply 43 has a smoothing means 42.
Switching transistor 4 for switching the output of
4, a coil 45 that temporarily stores the output of the switching transistor 44, a diode 46 / capacitor 47 that rectifies and smoothes the outputs of the switching transistor 44 and the coil 45, a zener diode 48, and a pulse that monitors the output voltage of this device by a resistor 49. And a width control circuit 50.

The pulse width control circuit 50 controls the ON ratio of the switching transistor 44 similarly to the pulse width control circuit 36 used in FIG. 1, and the output voltage V ₃ + V as shown in FIG. ₄ is made equal to V _Z.

At this time, the power supply device of the present invention can be realized even if the circuit configuration is as shown in FIG. In this circuit, a step-down type switching power supply 60 called a buck is used. 55 is a secondary winding 56 having a center tap
And a secondary winding 57. A center tap type rectifying / smoothing means 58 is connected to the secondary winding 56, and a partial smoothing type rectifying / smoothing means 59 is connected to the secondary winding 57. The switching power supply 60 is connected to the rectifying / smoothing means 58 among them, and has a switching transistor 61 for switching the voltage thereof, a pulse width control circuit 64 for controlling the switching transistor 61, a Zener diode 62 for monitoring the output voltage of the circuit, and a resistor. It has 63. As the switching power supply 60, a boost type power supply called boost may be used. Further, the power transformer 55 may be an auto transformer, and as the rectification method, half-wave rectification / double voltage rectification may be used.

If the circuit structure is as shown in FIG.
A power supply device having a very simple structure generally called a DC-DC converter can be used. Reference numeral 70 denotes a DC power source such as a battery, and the negative electrode side of the output of the switching power source 71 is connected to the positive electrode side of the DC power source 70.
That is, the switching power supply 71 is connected in series to the output of the DC power supply 70. The pulse width control circuit 72 constituting the switching power supply 71 determines the total voltage of the output of the DC power supply 70 monitored by the Zener diode 73 and the resistor 74 and the output of the switching power supply 71 as the Zener diode 7
The voltage is adjusted to the voltage determined by 3.

[0020]

The first means of the present invention is a rectifying means and a smoothing means directly connected to a commercial power source or connected via a power transformer, and a switching power source for switching and rectifying the commercial power source to a DC voltage. The switching power supply is configured so as to control the sum voltage of the output of the smoothing means and the output of the switching power supply, so that only the part lacking the target voltage is supplemented by the switching power supply connected in series. Thus, a small-sized and inexpensive power supply device with high power utilization efficiency is realized.

A second means of the present invention comprises a DC power supply and a switching power supply whose output is connected in series with the output of the DC power supply, wherein the switching power supply is the sum of the output of the DC power supply and the output of the switching power supply. As a configuration for controlling the power supply, a small and inexpensive power supply device is realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a power supply device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram explaining output characteristics of the same.

FIG. 3 is a circuit diagram showing a configuration in which a switching power supply is connected to the secondary side of the power transformer.

FIG. 4 is an explanatory diagram explaining output characteristics of the same.

FIG. 5 is a circuit diagram showing another configuration in which a switching power supply is connected to the secondary side of the power transformer.

FIG. 6 is a circuit diagram showing a configuration using a DC power supply as an input.

FIG. 7 is a circuit diagram showing a power supply device using a conventional power transformer.

FIG. 8 is a circuit diagram showing a power supply device using a switching power supply which is a conventional example.

[Explanation of symbols]

 23 power supply transformer 24 rectification means 25 smoothing means 26 switching power supply 40 power supply transformer 42 smoothing means 43 switching power supply 55 power supply transformer 59 rectification and smoothing means 60 switching power supply 70 DC power supply 71 switching power supply

Claims (2)

[Claims] 1. An output of the smoothing means, comprising: a rectifying means and a smoothing means, which are directly connected to a commercial power source or connected via a power transformer, and a switching power source which switches the commercial power source and rectifies the DC voltage. And a switching power supply output connected in series, and the switching power supply controls a voltage of the sum of the output of the smoothing means and the output of the switching power supply. 2. A power supply device comprising a DC power supply and a switching power supply whose output is connected in series with the output of the DC power supply, wherein the switching power supply controls the voltage of the sum of the output of the DC power supply and the output of the switching power supply.