JP3475798B2 - DC power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type DC power supply device used in various electronic devices.

[0002]

2. Description of the Related Art A conventional switching type DC power supply device is shown in FIG.
As shown in FIG. 3, the resonance capacitor 3 is connected in parallel with the secondary coil 2 to form a resonance circuit, and the output of the resonance circuit is rectified and smoothed by the diode 6 and the capacitor 7.

The DC power supply device having such a resonance circuit can efficiently transmit a large output to the secondary side circuit even when the coupling with the primary side coil 1 is relatively low. .

[0004]

However, in the above-mentioned configuration, in order to obtain a required output current, a current as shown in FIG. 8B is applied to the resonance circuit of the secondary coil 2 and the capacitor 3. Flowing. At this time, the waveform of the current flowing through the diode 6 of the rectifying circuit is as shown in FIG.
This waveform corresponds to the shaded portion in (b) of the figure, and the current other than the shaded portion does not become the output current but causes internal loss.

In the above-described operation, the effective value of the current flowing through the secondary coil 2 is 2 to 3 times the output current, so that the secondary coil 2 generates heat due to the loss due to this current, and the secondary coil 2 generates heat. The surface temperature of the housing on which the side coil 2 is mounted rises excessively, which is an obstacle when trying to obtain a relatively large output current.

The present invention solves the above problems and reduces the current flowing through the resonant circuit on the secondary side with an extremely simple circuit to effectively control the temperature of the housing in which the secondary coil is mounted. The present invention provides a DC power supply device that can be reduced.

[0007]

In order to achieve the above object, the present invention connects a resonance capacitor to a secondary side coil in parallel, and further connects a series circuit of an inductor and a rectifier to both ends of this resonance circuit. They are connected in parallel, and rectification circuits are provided at both ends of this circuit to obtain an output. As a result, the current flowing through the secondary coil can be reduced, and the temperature rise of the housing in which the secondary coil is mounted can be reduced.

Further, when a resonance capacitor is connected in parallel to the secondary coil, only inductors are connected in parallel to both ends of the resonance circuit, and a rectification circuit is provided at both ends of this circuit to obtain an output. , The current flowing through the added inductor becomes AC, but if the conditions are set appropriately, the same effect as when a diode is connected in series with the inductor is obtained. In addition to reducing the above-mentioned temperature rise, this circuit eliminates the loss due to the diode and has the effect of reducing the cost and mounting area.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention includes a primary coil supplied with a high frequency current, and a secondary coil magnetically coupled to the primary coil to receive electric power.
A capacitor connected in parallel with the secondary coil, a series circuit of an inductor and a diode connected in parallel with the secondary coil, and a rectifier circuit connected to the secondary coil to produce a DC output. With this, it is possible to reduce the current flowing through the secondary coil and reduce the temperature rise of the housing in which the secondary coil is mounted.

According to a second aspect of the present invention, a primary coil supplied with a high-frequency current, a secondary coil magnetically coupled to the primary coil to receive electric power, and the secondary coil. A capacitor connected in parallel with the coil, an inductor connected in parallel with the secondary coil, and a rectifier circuit connected to the secondary coil to generate a DC output, and an appropriate condition In the following, in addition to obtaining the same effect as that of claim 1, it is possible to reduce the loss in the diode, the number of parts, and the cost.

According to a third aspect of the present invention, there is provided a primary side winding to which a high frequency current is supplied, and a secondary side winding magnetically coupled to the primary side winding to receive electric power. A transformer, a capacitor connected in parallel with the secondary coil, a series circuit of an inductor and a diode connected in parallel with the secondary winding, and a DC output connected to the secondary winding. And a rectifier circuit that produces
It has the effect of reducing the current flowing through the secondary winding and reducing the temperature rise of the transformer.

According to a fourth aspect of the present invention, there is provided a primary winding supplied with a high frequency current, and a secondary winding magnetically coupled to the primary winding to receive electric power. A transformer and a capacitor connected in parallel with the secondary winding,
A transformer having an inductor connected in parallel with the secondary winding and a rectifier circuit connected to the secondary winding to produce a DC output. It has the effect of reducing the temperature rise.

(Embodiment 1) FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is a primary side coil for supplying high frequency current, 2 is mounted in a housing different from the primary side coil 1, and receives magnetic energy radiated from the primary side coil 1, A secondary coil for converting into electric energy, 3 is a resonance capacitor that forms a resonance circuit with the secondary coil 2, 4 is an inductor, 5 is a diode, and a series connection circuit of this inductor 4 and diode 5 is It is connected in parallel with the resonance circuit. The rectifying diode 6 and the smoothing capacitor 7 are a rectifying circuit for obtaining a DC output.

The current waveforms (Id, I
c, I _L ) is as shown in FIG. Here, a period I in FIG. 2 is a period in which the rectifying diode 6 of the rectifying circuit is off, and a current (Ic) flowing through the resonance capacitor 3 is a resonance current generated by the secondary coil 2 and the resonance capacitor 3. And becomes as shown in FIG. Further, the current (I _L ) flowing through the inductor 4 flows according to the voltage generated in the secondary coil 2, but the voltage generated in the secondary coil 2 is a sine wave and only the forward current flows due to the diode 5. As shown in FIG. 2C, the current Ip flows at the end of the period I.

A period II in FIG. 2 is a period in which the rectifying diode 6 of the rectifying circuit is on, and a current as shown in FIG. 2A flows through the diode 6 of the rectifying circuit to the output side. Here, this current is the sum of the current in FIG. 2 (b) and the current in FIG. 2 (c), and the current in FIG. 2 (c) is the value of the output voltage and the inductance of the inductor 4 with Ip as the peak. It decreases with the slope determined by. Since this current flows without passing through the secondary coil 2, the current flowing through the secondary coil 2 in order to obtain a predetermined DC output current (Idc) is reduced by an amount corresponding to the shaded area in FIG. 2C. Therefore, heat generation in the secondary coil 2 can be reduced.

Here, in order to control the output voltage or current to a predetermined value, a method of inserting an impedance variable element in series with the resonance capacitor 3 and controlling this impedance by the output amount is also possible and has been used recently. .

(Second Embodiment) FIG. 3 is a circuit diagram of a second embodiment of the present invention, which is the same as FIG. 1 except that the diode 5 is not provided. The current (Ic) in the resonance capacitor 3 and the current (Id) in the rectifying diode 6 of the rectifier circuit are the same as those in FIG. 2 except that only the current flowing through the inductor 4 flows in both directions.

By doing so, not only the loss of the diode 5 caused by the current shown in FIG. 2 (c) flowing through the diode 5 of FIG. 1 disappears, but also the cost of the diode 5 and the mounting aspect can be saved. become.

Furthermore, by setting the values of the inductances of the period I, the period II, and the inductor 4 to appropriate conditions,
A current as indicated by the broken line in FIG. 4C can be made to flow, and the reverse current of the inductor 4 can be eliminated,
The same effect as in FIG. 1 can be obtained.

(Embodiment 3) FIG. 5 is a circuit diagram of Embodiment 3 of the present invention. However, the primary coil 1 and the secondary coil 2 are not mounted in separate housings but one 2 is the same as that of the first embodiment except that the relationship between the primary winding 1 and the secondary winding 2 of the transformer 8 of FIG. As described above, since the temperature rise of the secondary winding 2 can be reduced, it is easy to downsize the transformer 8, and
The amount of copper used in the winding can be reduced, and the cost effect will be great.

(Embodiment 4) FIG. 6 is a circuit diagram of Embodiment 4 of the present invention. However, the primary coil 1 and the secondary coil 2 are not mounted in separate housings, but one The transformer 8 is the same as the second embodiment except that the relation between the primary winding 1 and the secondary winding 2 is the same, and the current waveforms of respective parts are also the same as those in FIG. 4 and the same as the second embodiment. As described above, the reduction of the temperature rise of the secondary winding 2 facilitates downsizing of the transformer 8 and also eliminates the loss due to the diode 5. In addition, the amount of copper used in the winding can be reduced, and the cost effect obtained by omitting the diode 5 is great.

[0022]

As described above, according to the present invention, the secondary side coil or the secondary winding is connected to the series circuit of the inductor and the diode in parallel.
The current of the secondary coil or the secondary winding can be reduced, and the temperature rise can be suppressed, so that a relatively large output DC power supply device can be realized.

Further, not only the non-contact type DC power supply device but also the transformer of a normal switching type power supply device,
A capacitor having a resonance capacitor on the secondary side is very effective in reducing the size and cost of the transformer.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram of each current waveform in FIG.

FIG. 3 is a circuit diagram of a DC power supply device according to another embodiment of the present invention.

FIG. 4 is a schematic diagram of each second current waveform.

FIG. 5 is a circuit diagram of a DC power supply device according to another embodiment of the present invention.

FIG. 6 is a circuit diagram of a DC power supply device according to another embodiment of the present invention.

FIG. 7 is a circuit diagram of a conventional DC power supply device.

FIG. 8 is a schematic diagram of each current waveform in FIG.

[Explanation of symbols]

1 Primary coil / Primary winding 2 Secondary coil / Secondary winding 3 Resonance capacitor 4 inductor 5 diode 6 Rectification diode 7 Smoothing capacitor 8 transformers

Claims (4)

(57) [Claims] 1. A primary coil to which a high-frequency current is supplied, a secondary coil magnetically coupled to the primary coil to receive electric power, and a capacitor connected in parallel with the secondary coil. A DC power supply device comprising a series circuit of an inductor and a rectifier connected in parallel with the secondary coil, and a rectifier circuit connected to the secondary coil to generate a DC output. 2. A primary side coil supplied with a high frequency current, a secondary side coil magnetically coupled with the primary side coil to receive electric power, and a capacitor connected in parallel with the secondary side coil. A DC power supply device comprising: an inductor connected in parallel with the secondary coil; and a rectifier circuit connected to the secondary coil to generate a DC output. 3. A primary winding supplied with a high frequency current,
A transformer having a secondary winding that magnetically couples with the primary winding to receive electric power, a capacitor connected in parallel with the secondary winding, and connected in parallel with the secondary winding. DC power supply device comprising a series circuit of the inductor and the rectifier, and a rectification circuit connected to the secondary winding to produce a DC output. 4. A primary winding supplied with a high frequency current,
A transformer having a secondary winding that magnetically couples with the primary winding to receive electric power, a capacitor connected in parallel with the secondary winding, and connected in parallel with the secondary winding. DC power supply device having a controlled inductor and a rectifier circuit connected to the secondary winding to generate a DC output.