JPH04275066A - Floating switching power supply device - Google Patents

Abstract

PURPOSE:To reduce an entire apparatus in size. CONSTITUTION:An AC induced in a secondary winding of a transformer 2 is converted to a DC voltage Vo via a diode 3, a capacitor 4, an AC induced in an intermediate terminal S3 of the secondary winding is converted to a DC floating voltage Vf via a diode 5, a capacitor 6, converted to a floating voltage Vf, the voltage Vf is varied by a switch 7, and an output voltage Vo to the ground is varied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floating power supply device having a function of switching floating voltage.

0002

[Prior Art] A conventional floating power supply device is shown in FIG.
As shown in FIG. 2, the secondary winding for generating the floating voltage Vf and the secondary winding for generating the required output voltage Vo are separately provided, and the alternating current of each secondary winding is connected to a rectifier circuit 31. , a smoothing circuit 32, a rectifying circuit 33, and a smoothing circuit 34 to rectify, smooth, and convert the voltage to direct current, and then add the floating voltage Vf and the output voltage Vo.

[0003] Switching of the floating voltage is achieved by, for example, rectifying or rectifying the alternating current of the secondary winding for generating the floating voltage.
After smoothing, it passes through the series regulator 35 and switches the drop voltage of the series regulator to the switch 36.
This was achieved by methods such as changing the

0004

[Problems to be Solved by the Invention] However, in the conventional example, the winding for generating the floating voltage VF is provided separately from the winding for generating the output voltage, which increases the size of the transformer and makes it difficult to downsize the device. The problem was that it was difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a floating switching power supply device that is more compact as a whole.

[0006]

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a first rectifying/smoothing means for extracting a DC output voltage from an AC induced in the secondary winding of a transformer, and It is characterized by comprising a second rectifying/smoothing means for extracting a DC floating voltage from the secondary winding, and a connecting means capable of changing the connection impedance between the reference potential and the second rectifying/smoothing means. shall be.

[0007]

[Operation] In the present invention, the alternating current induced in the secondary winding of the transformer is converted into a direct current voltage by the first rectifying and smoothing means, and the alternating current induced in the secondary winding is converted into a direct current floating voltage by the second rectifying and smoothing means. Convert to voltage, reference voltage and second rectifier
The connection impedance between the smoothing means and the smoothing means is changed by the connection means.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a transformer drive unit for injecting voltage into a transformer 2, and 2 is a transformer having a primary winding and a secondary winding provided with an intermediate terminal S3. 3 is a diode, 4 is a capacitor, which rectifies the alternating current between terminals S1 and S2 on the secondary winding side.
It smooths the surface. A diode 5 and a capacitor 6 rectify and smooth the alternating current between the intermediate terminal S3 and the terminal S1. Reference numeral 7 denotes a switch which switches, depending on the mode, whether to short-circuit the positive potential side of the DC voltage (VF) obtained by the diode 5 and capacitor 6 to a certain reference potential (GND) or to open it. This switch 7 is
For example, mechanical switches, relay elements, transistors,
This is realized using FET, etc. 8 is a bias resistor and switch 7
This is for setting the potential of the terminal S1 to GND when is OFF.

[0010] When switch 7 is OFF, terminals S1 and S2
The DC voltage Vo obtained by rectifying and smoothing the induced voltage between
The bias resistor 8 makes the ground (GND) a reference potential (the potential of S1 is GND).

On the other hand, when the switch 7 is ON, the terminal S1
, S3 is the DC voltage V obtained by rectifying and smoothing the AC between S3.
Since f is induced with respect to GND, the potential of the terminal S1 becomes -Vf. That is, at this time, it is possible to realize a power supply device with an output Vo in which -Vf is a floating potential.

[0012] As a result of the above, the floating potential -Vf
The floating voltage can be switched to either GND or -Vf depending on the mode without separately providing a winding for generation of Vf.

Other embodiments FIG. 2 shows another embodiment of the invention.

This embodiment is the same as the first embodiment in that it is a power supply device with an output Vo that uses -Vf as a floating potential, but the stability of Vf is high by applying feedback, and the voltage Vf is controlled by a resistor 16, The difference is that the voltage Vf can be varied by changing the amount of feedback obtained by dividing the voltage by 17 or by changing the reference voltage of the reference power supply 10.

That is, capacitor 1 to ground
The voltage Vf of 5 is divided by resistors 16 and 17, and compared with the reference voltage of the reference power supply 10 to find an error.The ON resistance of the transistor 14 is changed according to the error, and the voltage of the capacitor 15 with respect to the ground is changed. .

In this embodiment, the variable resistor 16 is changed depending on the mode.
, an example in which the voltage division ratio of the resistor 17 is changed has been described, but the voltage Vref of the reference power source 10 may be changed to change the floating voltage depending on the mode.

[0017]

[Effects of the Invention] As explained above, according to the present invention,
Since the winding for obtaining the output voltage and the winding for obtaining the floating voltage are shared, it is possible to downsize the transformer, which has the effect of making it possible to downsize the entire device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing a conventional floating switching power supply device.

[Explanation of symbols]

1 Transformer drive section 2　Trans 3, 5 Rectifier diode 4,6 Smoothing capacitor 7 Switch

Claims (1)

[Claims] 1. A first rectifying/smoothing means for extracting a DC output voltage from an alternating current induced in a secondary winding of a transformer, and a second rectifying/smoothing means for extracting a DC floating voltage from the secondary winding. A floating switching power supply device comprising a smoothing means and a connecting means capable of changing the connection impedance between the reference potential and the second rectifying/smoothing means.