JPH09215325A - Dc power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve operation efficiency by providing a system with a transformer for driving a first and a second rectifier element which are connected to a tertiary winding installed in a main transformer through a third rectifier element. SOLUTION: A switching element 14 is connected to a primary-side winding 12 of a main transformer 11 and a transformer for driving a first and a second rectifier element 15, 16 is connected to a tertiary winding 45 in the main transformer 11 through a third rectifier element 44. When the switching element 14 is turned on, voltage is induced in a secondary-side first winding 42 of the main transformer 11 through a primary winding 41 of the transformer for driving a first and a second rectifier element 15, 16 and the second rectifier element 16 is turned off by the voltage inducted in a secondary-side second winding 43. As a result, DC Id is caused to flow in the direction shown by the arrow through the first rectifier element 15 and thereby power is supplied to a load 19. When the switching element 14 is turned off, on the other hand, reverse voltage is induced and current If is caused to flow in the same direction as the DC Id to supply power to the load 19. Therefore, the operation efficiency can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC switching power supply device that efficiently supplies electric power to a load through a rectifying element that opens and closes synchronously.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a conventional DC power supply device. In FIG. 4, reference numeral 10 denotes a DC switching power supply device as a whole, 11 is a main transformer, 12 is a primary winding of the main transformer, 13 is a secondary winding thereof, and black circles are windings respectively. Indicates the end of winding or the beginning of winding. Reference numeral 14 represents a switching element. Reference numerals 15 and 16 denote rectifying elements that open and close synchronously, and in this case, are field effect transistors. Reference numeral 17 is a smoothing choke coil, 18 is a smoothing capacitor, 19 is a load, and 20 is a DC voltage source.

The power supply device shown in FIG. 4 is a so-called switching power supply and takes out the input DC as a DC output. The DC current from the DC voltage source 20 is controlled by a control device (not shown) to open / close the switching element 14 so as to generate an AC signal, which flows through the primary winding 12 of the main transformer 11. Although an example in which a field effect transistor is used as the switching element 14 is given, the AC signal generated in the secondary winding 13 of the main transformer 11 when the element 14 is turned on is generated by opening and closing the field effect transistors 15 and 16. Is rectified by the smoothing choke coil 17 and the smoothing capacitor 18 and smoothed.
9.

Now, when the secondary winding 13 has a positive voltage in the direction of arrow Vs in FIG. 4, the field effect transistor 15 is turned on, and a direct current flows in the direction shown by arrow Id in FIG. DC voltage is supplied to the load 19. At this time, the field effect transistor 16 is off. When the switching element 14 is turned off and the secondary winding 13 of the main transformer 11 becomes a positive voltage in the direction opposite to the direction of the arrow Vs, the field effect transistor 15 is turned off and at the same time the field effect transistor 16 is turned on. Change to. The operation in which the two current switching elements connected to the secondary winding of the main transformer are exclusively on / off controlled in this manner is called synchronous switching. Unlike when it is connected as in the case of a diode, it operates automatically, unlike when it receives a control signal from the outside. An element other than the field effect transistor may be used as long as a rectified current can be obtained by performing the synchronous switching operation.

Therefore, a direct current flows in the direction shown by the arrow If, and the current flowing in the smoothing choke coil 17 is in the same direction as described above, so that the direct current supply to the load 19 is continued. FIG. 5 is a diagram showing voltage / current waveforms related to the secondary winding 13 of the main transformer 11. FIG. 5 (a) shows the AC voltage Vs generated in the secondary winding 13 of the main transformer.
FIG. 6 is a diagram showing a current If flowing in the field effect transistor 16. In FIG. 5A, the voltage Vs is generated as a pulse in the positive direction, for example, only while the switching element 14 is on. At this time, Id shown in the current waveform
Flows in the direction shown in FIG.

When the switching element 14 is turned off, the voltage Vs is immediately inverted and becomes a pulse voltage in the negative direction, for example. The field effect transistor 16 is turned on,
The current If in the direction shown in FIG. 4 flows. The field effect transistor 16 is turned off in the latter half of the negative waveform of the voltage Vs. At that time, the current If continues to flow in the same direction in a slightly small amount through the regenerative diode which the field-effect transistor 16 inherently has. When the switching element 14 is turned on next time, that is, when the field effect transistor 15 is turned on, the well-known PWM control is performed such that the off time slightly longer than the on time of the switching element 14 has elapsed.

Next, FIG. 6 is a diagram for explaining a case where the conventional switching power supply device shown in FIG. 4 is connected in parallel. In FIG. 6, 10 and 30 are switching power supply devices as a whole, 19 is a common load for the power supply devices 10 and 30 connected in parallel, and 21 and 22 are stop diodes. Switching power supply device 10, 3
The constituent elements in 0 are the same, and the elements in 30 are not shown.

As for the power supply device 30 shown in FIG. 6, another power supply device can be connected in parallel if necessary. Normally, the same DC voltage is applied to the output terminals of a plurality of power supply devices, and power is jointly supplied to the common load 19. Therefore, different current values may be shared. Young
An abnormal condition occurs in the power supply device 10 and the DC voltage at the output end is zero V
Let's say At this time, if the stop diode 21 is not connected to the power supply device 10, the following trouble occurs.

That is, because of an abnormality, the field effect transistor 1
Both 5 and 16 are off. When the stop diode 21 is not connected, the voltage on the side opposite to the ground potential of the load 19 is high, so that the load voltage is applied to the gate of the field effect transistor 15 to turn it on. Normally, the field-effect transistor 15 has a characteristic that it is turned on by the voltage of the main transformer 11 secondary winding 13, but in the on-state based on a so-called sneak current, it is not turned on with low resistance, but rather with respect to the current circuit of Id. The state has a resistance value of a certain magnitude.

That is, a load connected in parallel with the load 19 causes a large loss. Therefore, the stop diode 21 or the like is inserted to prevent the generation of a sneak current.

[0011]

In the operation waveform diagram shown in FIG. 5, the field effect transistor 16 is off in the latter half of the period during which the current If flows, and the field effect transistor 16 has a resistance to the current. At that time, due to the current flowing through the regenerative diode, power loss occurs in the latter half of If, and the field effect transistor 16 has a drawback that it generates more heat than the field effect transistor 15.

When the power supply devices are connected in parallel, it is necessary to insert a stop diode. The stop diode has a drawback that a voltage drop occurs due to a large current when passing a current, an expensive diode itself is required, and heat is generated. SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC power supply device which improves the above-mentioned drawbacks, has high operation efficiency, and does not use an expensive diode even when connected in parallel and can effectively supply power.

[0013]

FIG. 1 is a diagram showing a basic configuration of the invention described in claim 1. In FIG. In FIG. 1, 11 is a main transformer, 12 is a primary winding of the main transformer, 13 is a secondary winding thereof, 14 is a switching element, 15 is a first rectifying element,
Reference numeral 16 is a second rectifying element, 17 is a smoothing choke coil, 1
8 is a smoothing capacitor, 19 is a load, 20 is a DC voltage source, 40 is a transformer for driving a rectifying element, 41 is the primary winding of the transformer, 42 is the same secondary winding, and 43 is the same. Secondary side second winding, 44 is a third rectifying element, and 45 is a tertiary winding of the main transformer.

A switching element 14 is connected to the primary side winding 12 of the main transformer 11, and a main transformer is connected via a secondary side winding 13 of the main transformer and first and second rectifying elements 15 and 16 which synchronously open and close. The secondary side AC output is rectified and smoothed, and the obtained DC is loaded 1
In order to achieve the above object, the present invention has the following configuration in the DC power supply device for supplying the voltage to the DC power supply unit 9. That is, the invention according to claim 1 comprises the first and second rectifying element driving transformers 40 connected to the tertiary winding 45 provided in the main transformer 11 via the third rectifying element 44. Configure.

According to a second aspect of the present invention, a field effect transistor is used as the synchronous switching element. A third aspect of the invention is configured by connecting a plurality of sets of the power supply devices in parallel and supplying direct current to the load.

(Operation) In the circuit diagram shown in FIG. 1, when the switching element 14 is turned on and off, the main transformer 11
An AC signal Vs is generated in the secondary winding 13 of the above, and the voltage generated in the tertiary winding 45 at this time turns on the third rectifying element 44. Therefore, the voltage Vs is the primary of the rectifying element driving transformer 40. It is applied to both ends of the side winding 41.

FIG. 2 is an operation waveform diagram of the circuit shown in FIG. FIG. 2A shows an AC voltage Vs generated in the secondary winding 13 of the main transformer 11. When the switching element 14 is turned on, this voltage Vs is applied to the primary winding 41 of the transformer 40.
The voltage Vg1 is generated in the secondary side first winding 42 via. The voltage Vg1 is shown in FIG. The magnitude of the voltage Vg1 is a value proportional to the winding ratio of the windings 41 and 42 in the positive direction and proportional to the winding 42 in the negative direction.

Next, the voltage Vg2 generated in the secondary side second winding 43 of the rectifying element driving transformer 40 has a polarity opposite to that of Vg1. As shown in FIG. 2 (c), a large voltage in the negative direction is the winding ratio of the winding 41 and the winding 43, and a large voltage in the positive direction is the winding 4
It is a value proportional to 3, respectively. Vg shown in Fig. 2 (b)
The first pulsed voltage of 1 turns on the first rectifying element 15, and at the same time the voltage of Vg2 turns off the second rectifying element 16. As a result, the direct current Id flows through the first rectifying element 15 in the direction shown in the figure, and power is supplied to the load 19.

Then, since the switching element 14 is turned off, the secondary side first winding 42 of the transformer 40 for driving the rectifying element,
An alternating voltage (the latter half of Vs) in the opposite direction to the above is generated in the second winding 43. Since the current If flowing through the first rectifying element 15 is in the same direction as the direct current Id, the load 19
DC power is continuously supplied to. Switching element 1
The first rectifying element 15 is on for about the time when 4 is on, and then is off.

The second rectifying element 16 is off during the on time of the switching element 14, and is turned on by the voltage generated in the second winding 43 when the switching element 14 is off. The switching element 14 is normally off for a longer time than the on-time, and the second rectifying element 16 is on for the duration of the voltage generated in the second winding 43 during that period.

First, the transformer 40 for driving the rectifying device is used.
Since the second rectifying element is driven, especially in the second rectifying element 16, if the switching element 14 is in the latter half of the off state, that is, the latter half of the flow of If, as shown in FIG. Will flow as before and will not cause a loss. According to the invention described in claim 2, since the rectifying element for opening and closing the field effect transistor is used, synchronous control can be easily performed.

According to the third aspect of the invention, even if the power supply circuits are connected in parallel, the load terminal voltage is not directly applied to the control electrode of the synchronous switching element, so that the efficiency may deteriorate. Absent.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a circuit diagram showing an embodiment of the invention described in claims 1 to 3. In FIG. 3, the parts connected in parallel have the same configuration as the power supply circuit shown in the uppermost part, and therefore details are not shown. In FIG. 3, different points from FIG. 1 are that the secondary side second winding of the rectifying element drive transformer and the second rectifying element are connected, and that a diode is connected between the second winding and the output terminal. Is.

In FIG. 3, a winding 45 is added to the secondary side second winding 43 of the rectifying element driving transformer 40, and the intermediate tap 46 of the winding is connected to the anode of the diode 47. The cathode of the diode 47 is connected to the DC output terminal 48. In FIG. 3, if the number of turns of the winding 41 is N1, the number of turns of the winding 42 is N2, the number of turns of the winding 43 is N3, the number of turns of the winding 45 is N5, and the number of turns of N3 + N5 is N4, then in FIG. A value proportional to 42/41 is Vs · N2 / N1 and N
A value proportional to 2 is Vo · N2 / N3, where
Vo is a DC voltage between terminals 48 and 49 in FIG. 2 (c),
The value proportional to 43 is Vo · N4 / N3, 43 /
A value proportional to 41 is Vs · N4 / N1.

The difference in voltage is similar to the difference in the operation of the field effect transistor 16 as the second rectifying element. Further, the diode 47 is shown as a diode 67 connected at the same position inside the power supply circuit 60 connected in parallel. These diodes prevent the DC voltage at the terminal 48 from being directly applied to the field effect transistors of the operable power supply circuit, eg the gates of 15, 16 when one of the power supply circuits connected in parallel becomes inoperable. To do. At that time, no sneak current is generated, so that no loss occurs in the DC output.

Further, in this diode, since the current flowing through the main transformer 11 is suddenly cut off when the switching element 14 is turned off, the rectifying element driving transformer 4 at that time is cut off.
It is connected in order to prevent the voltage between both terminals of the secondary side first and second windings of 0 from rising sharply.

[0027]

As described above, according to the present invention, the rectifying element driving transformer is connected between the main transformer and the synchronous driving transformer, and the individual winding for driving the rectifying element is provided. Since it has, the operation of the rectifying element can be efficiently performed. According to the second aspect of the present invention, since the field effect transistor is used, it is possible to easily control the synchronous switching.
According to the invention described in claim 3, it is not necessary to use an expensive diode which has been conventionally used, and a parallel-connected power supply device having stable operation can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the invention according to claim 1.

FIG. 2 is an operation waveform diagram of the circuit shown in FIG.

FIG. 3 is a diagram showing an embodiment of the invention described in claims 1 to 3.

FIG. 4 is a circuit configuration diagram showing a conventional DC power supply device.

FIG. 5 is a diagram showing voltage / current waveforms related to the secondary winding of the main transformer.

6 is a diagram illustrating a case where the conventional DC power supply device shown in FIG. 4 is connected in parallel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 power supply device 11 main transformer 12 primary side winding 13 of main transformer 13 same secondary side winding 14 switching element 15 first rectifying element 16 second rectifying element 17 smoothing choke coil 18 smoothing capacitor 19 load 20 DC voltage Source 40 Transformer for driving rectifying element 41 Primary winding of the transformer 42 Primary first winding 43 Secondary secondary winding 42 Secondary secondary winding 44 Third rectifying element 45 Tertiary winding of main transformer

Claims (3)

[Claims] 1. A first transformer for connecting a switching element to the primary winding of the main transformer and opening and closing in synchronization with the secondary winding of the main transformer.
In a DC power supply device that rectifies and smoothes the secondary side AC output of a main transformer via a second rectifying element and supplies the obtained DC to a load, a third rectifying element is provided in a tertiary winding provided in the main transformer. A DC power supply device comprising a first and a second rectifying element driving transformer connected via the DC power supply. 2. A DC power supply device, wherein a field effect transistor is used as the synchronous rectifying element according to claim 1. 3. A plurality of sets of the DC power supply device are connected in parallel, and one of the secondary windings of the rectifying device driving transformer of each set and an output terminal are connected by a unidirectional device. The DC power supply device according to claim 1 or 2, which is characterized in that.