KR101276983B1 - a DC-DC converter and a method for operating it - Google Patents

Abstract

In the DC-DC converter according to an embodiment of the present invention, a DC-DC converter, comprising: a plurality of transformers for transforming the power supplied from the input terminal to the input side coil to transfer to the output side coil; A switch unit including a plurality of input side switches for alternately operating the plurality of transformers; And an output terminal for outputting power output from the output side coil, wherein the switch unit alternately operates the plurality of transformers by switching at zero voltage using a magnetizing inductance of some of the plurality of transformers.

Description

DC-DC converter and a method of operation thereof {a DC-DC converter and a method for operating it}

The present invention relates to a DC-DC converter and a method of operating the same. More specifically, the present invention relates to a DC-DC converter capable of reducing output stage loss and current ripple without using a separate filter inductor at the output stage by using magnetizing inductance of a transformer and a method of operating the same.

With the development of the industry and the expansion of renewable energy, large-capacity DC / DC converters (DC power converters) are being actively researched in terms of small size and light weight, and are widely used in broadcasting communication equipment, OA equipment, industrial electronic application equipment, and precision equipment. It is widely used as a power supply device, a low voltage / large current converter, or a high voltage converter in fields such as a computer and an ozone generator.

In addition, a zero-emission vehicle (ZEV) using an electric lamp is generally equipped with a DC / DC converter for the system high efficiency, the insulation is essential for safety.

In addition, in order to achieve high integration and high efficiency of DC / DC converter technology, a zero voltage or zero current switching method is used to reduce switching loss and switching stress by making a switching point of a switch at zero voltage or zero current of a switch.

1 is a circuit diagram of a power stage configuration for achieving general zero voltage or zero current switching.

Referring to FIG. 1, a full bridge DC-DC converter circuit in which an output filter (smoothing unit) is formed of an inductor and a capacitor is illustrated. In this general power stage, the filter inductor 10 is inserted into the output stage in order to satisfy the current ripple specification of the output stage and to reduce the filter capacitor capacity and the number of uses.

In general, using a circuit of such a configuration uses the energy stored in the leakage inductance and the filter inductor of the transformer to mitigate the change in voltage generated during switching, thereby achieving zero voltage switching.

However, the general power stage circuit as shown in FIG. 1 has a problem in that the capacitance of the capacitor must be increased when directly applied to the output capacitor because the ripple component of the transformer output current is large. In addition, there is a problem that the number of capacitors is used to increase the total volume of the filter portion.

In addition, when a filter inductor is added to reduce output stage current variation and condenser input current ripple, the conduction loss and core loss of the inductor increases as the output current increases, thereby reducing efficiency during large current output.

In the case of configuring a full bridge switch, zero voltage switching is performed using the output current and the filter inductor during the operation of the two switches, but only the energy stored in the leakage inductance of the transformer can be used for the remaining two switches. There is a problem that the zero voltage switching is not performed at light loads unless it is increased or the additional circuit is mounted.

It is an object of the present invention to provide a DC-DC converter capable of zero voltage or zero current switching without a filter inductor at the output stage and a method of operating the same.

In addition, the present invention provides an efficient DC-DC converter and its operation method even at a large current output.

In addition, the present invention provides a DC-DC converter capable of increasing the zero voltage switching efficiency and reducing the output current ripple and a method of operating the same.

DC-DC converter according to an embodiment of the present invention for achieving the above object, a plurality of transformer for transforming the power supplied from the input terminal to the input side coil to transfer to the output side coil; A switching unit including a plurality of input side switches and a plurality of output side switches for alternately operating the plurality of transformers; A controller for controlling the switching unit; And an output stage for outputting power output from the output side coil, wherein the controller controls switching at zero voltage by using magnetization inductance of some of the plurality of transformers.

In addition, a method of operating a DC-DC converter according to an embodiment of the present invention for achieving the above object, in the method of operating a DC-DC converter, a plurality of transformers including an input power source and a first transformer and a second transformer Feeding the field; Turning off the input and output side switches of the second transformer while turning on the input and output side switches of the first transformer; Turning off the input and output side switches of the first transformer; And when the voltage across the second transformer is zero, turning on an input side switch of the second transformer.

According to an embodiment of the present invention, zero voltage or zero current switching is possible without a filter inductor at the output stage. In addition, the efficiency at the time of high current output can be increased.

In addition, according to the embodiment of the present invention, the magnetizing inductance of the transformer can be used for zero voltage or zero current switching to reduce cost and reduce volume.

In addition, even when a full bridge switch is configured, there is an effect of enabling zero voltage switching at light load.

1 is a diagram illustrating a general zero voltage switching circuit.
2 is a circuit diagram of a DC-DC converter according to an embodiment of the present invention.
3 is a graph illustrating a voltage current waveform of a DC-DC converter according to an embodiment of the present invention.
4 is a circuit diagram illustrating a full bridge DC-DC converter according to an embodiment of the present invention.
5 is a circuit diagram illustrating a parallel structured DC-DC converter according to another embodiment of the present invention.
6 is a circuit diagram illustrating an interleaved DC-DC converter according to another embodiment of the present invention.
7 is a flowchart illustrating a method of operating a DC-DC converter according to an embodiment of the present invention.

The following merely illustrates the principles of the invention. Thus, those skilled in the art will be able to devise various apparatuses which, although not explicitly described or shown herein, embody the principles of the invention and are included in the concept and scope of the invention. Furthermore, all of the conditional terms and embodiments listed herein are, in principle, intended only for the purpose of enabling understanding of the concepts of the present invention, and are not intended to be limiting in any way to the specifically listed embodiments and conditions .

It is also to be understood that the detailed description, as well as the principles, aspects and embodiments of the invention, as well as specific embodiments thereof, are intended to cover structural and functional equivalents thereof. It is also to be understood that such equivalents include all elements contemplated to perform the same function irrespective of the currently known equivalents as well as the equivalents to be developed in the future, i.e., the structure.

In the claims of this specification, components expressed as means for performing the functions described in the detailed description include all types of software including, for example, a combination of circuit elements or firmware / microcode, etc. that perform the functions. It is intended to include all methods of performing a function which are combined with appropriate circuitry for executing the software to perform the function. The invention, as defined by these claims, is equivalent to what is understood from this specification, as any means capable of providing such functionality, as the functionality provided by the various enumerated means are combined, and in any manner required by the claims. It should be understood that.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: There will be. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The suffix "module" and " part "for components used in the following description are given merely for ease of description, and the" module "and" part "

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram illustrating a DC-DC converter according to an embodiment of the present invention.

Referring to FIG. 2, the DC-DC converter according to an embodiment of the present invention includes an input terminal 110, a first transformer 131, a second transformer 132, and a first input side switch unit 121 for power input. And a second input side switch unit 122, a first output side switch unit 141, a second output side switch unit 142, and an output terminal 150. The controller may further include a controller (not shown) for controlling the operation of each switch unit described above.

The input terminal 110 supplies input power to the first transformer 131 and the second transformer 132. In general, the vehicle DC-DC converter may be a low voltage dc-dc converter (LDC) in which a high voltage of 150 to 350V is input and transformed into an output of 12V. And, the transformed output power can be used in the design of a vehicle charger. Therefore, according to an embodiment of the present invention, but may be used in the field of using a large current output type by the transformer, but is not limited thereto.

Meanwhile, the first input side switch unit 121 and the second input side switch unit 122 alternately operate in synchronization with the first output side switch unit 141 and the second output side switch unit 142, and output stage 150. Make sure power is supplied to the For example, when the first input side switch unit 121 is in an ON state, the first output side switch unit 141 is also in an ON state, so that the first transformer 131 transfers power, and the second input side switch unit 121 is used. Is in an ON state, the second output side switch unit 141 is also in an ON state, and the second transformer 132 transmits power.

Here, according to an embodiment of the present invention, while the first input side switch unit 121 and the first output side switch unit 141 are ON, the second input side switch unit 122 and the second output side switch unit 142 are used. Is OFF, the second transformer 132 stores the magnetizing inductance energy. That is, the second transformer 132 is charged.

When the first input side switch unit 121 and the first output side switch unit 141 are turned off, the second input switch unit 122 and the second output side switch unit 142 are turned off and the second transformer 132 is turned off. The magnetization inductance stored in) is output in the form of a current, and discharge occurs. When the voltage across both of the second transformer 132 becomes zero at the time when the discharge is completed, the second input switch 122 and the second output switch 142 are turned on and the second transformer 132 supplies power. Will be delivered. On the other hand, since the first input side switch 121 and the first output side switch 141 are turned off, the first transformer 131 charges the magnetizing inductance during this time. Therefore, the zero voltage switching can be achieved while repeating the above process.

On the other hand, the input coils of the first transformer 131 and the second transformer 132 are connected in series, the output coils are connected in parallel, it is possible to transfer the above-described alternating power.

Through this operation, the energy stored in the magnetizing inductance of the transformer is used as an energy source of zero voltage switching, so zero voltage switching is possible without a filter inductor at the output stage, and zero voltage switching is performed at all loads regardless of the light weight of the load. It becomes possible.

Meanwhile, the first output terminal switch unit 141 and the second output terminal switch unit 142 may include a rectifying unit. The rectifier may also include a synchronous rectifier switch or a diode rectifier for rectification. Synchronous rectifier switches enable zero-current switching even at high currents by allowing the output stage to switch for each synchronization.

In addition, although FIG. 2 illustrates a circuit in which the first output stage switch 141 and the second output stage switch 142 include a synchronous current switch as a rectifier, the present invention includes a diode rectifier instead of synchronous rectifier switching. Zero voltage switching according to an embodiment of the present invention is possible, and the effect of the output side characteristic of reducing the ripple current can be obtained.

3 is an operation waveform graph for describing an operation of a DC-DC converter according to an embodiment of the present invention according to the circuit of FIG. 2.

The operation of the DC-DC converter according to an embodiment of the present invention will be described in detail with reference to FIG. 3 as follows.

First, when input power is input from the input terminal 110, S1, the first input side switch unit 121, is turned on, and SR1, the first output side switch unit 141, is turned on, and the first transformer 131 connected to the output terminal is output. Connected to 150, the power is to be delivered. As described above, while S1 and SR1 are ON, S2 which is the second input side switch unit 122 and the second output side switch unit 142 SR2 are turned OFF. As a result, the second transformer 132 is not connected to the output terminal 150, and does not transmit power, and the magnetizing inductance is charged according to the input current.

Thereafter, when a predetermined time has elapsed, S1 which is the first input side switch unit 121 is turned off, and SR1 which is the first output side switch unit 141 is also turned off. Then, as soon as S1 and SR1 are turned off, current flows by the power charged in the magnetizing inductance of the charged second transformer 132, so that the DS (drain to source) voltage of S1 is increased, and the DS voltage of S2 is increased. Will decrease.

Thereafter, when the applied voltage of S2 decreases to 0 and the diode connected to S2 conducts, S2 turns on and zero voltage switching is performed.

In addition, when S2, the second input side switch unit 122, is turned on, the polarity of the input voltage transmitted to the second transformer 132 is changed, thereby charging the magnetizing inductance of the first transformer 131.

On the other hand, the second transformer 132 transfers power to the output terminal 150 through the diode included in the second output side switch unit 142. Zero voltage switching is made possible by turning on SR2 of the second output side switch unit 142 at the time when power is transmitted. In addition, when the current of the rectifying unit included in the first output side switch unit 141 and the second output side switch unit 142 is zero current or the voltage is zero voltage, SR2 may be switched on.

In addition, the first output side switch unit 141 enables zero current switching by considering a voltage decrease transition time when the first output side switch unit 141 is turned off due to the magnetization and leakage inductance of the first transformer.

As a result of the operation of the circuit according to the embodiment of the present invention as described above, the waveform flowing to the synchronous current of the first output side switch unit 141 and the synchronous current of the second output side switch unit 142 is shown in the lower part of FIG. Is shown. Comparing ISR1 and ISR2, the current at the output stage forms an overlapping form by alternating operations of the first and second transformers 131 and 312.

In addition, it can be seen that the current ripple component is greatly reduced in the load current Io shown at the bottom according to the overlapped form.

Therefore, according to an embodiment of the present invention it can be seen through Figure 3 that the current overlap of the ISR1 and ISR2 is made by the alternating operation of the transformer, thereby reducing the ripple of the load current Io.

4 is a circuit diagram illustrating a full bridge DC-DC converter according to an embodiment of the present invention.

Referring to FIG. 4, the DC-DC converter according to the embodiment of the present invention may configure the input terminal in the form of a full bridge 160. As shown in FIG. 4, the pair of S3 switches and the pair of S4 switches of the input terminal 160 configured as full bridges may constitute the first module 161 and the second module 162, respectively. The modules correspond to the S1 switch and the S2 switch described with reference to FIG. 3, respectively, and may operate alternately, so that the switching between the first module 161 and the second module 162 is performed in the same order as described in FIG. 3. Can be done. For example, when the first module 161 is ON and the second module 162 is OFF, the first transformer unit 131 transmits power and the magnetization inductance of the second transformer unit 132 is charged. The operation may be performed in order, and the subsequent operation is the same as described above and will be omitted.

The full-bridge DC-DC converter circuit according to an embodiment of the present invention shown in FIG. 4 is capable of zero voltage switching using alternating magnetization inductance as well as the DC-DC converter of FIG. The transformer can be driven to superimpose the output current and reduce the current ripple. In particular, in one embodiment of the present invention by using a full bridge configuration, there is an advantage that the zero voltage switching is possible even at the time of high voltage input.

5 and 6 are circuit diagrams of a parallel structured DC-DC converter and an interleaved DC-DC converter according to another embodiment of the present invention.

Referring to FIG. 5, according to another embodiment of the present invention, the DC-DC converter circuit of FIG. 3 may be configured in parallel to provide a DC-DC converter capable of high efficiency output even at a large current. In FIG. 5, the S1 and S2 switch units 171 of the upper converter circuit alternately operate to operate a pair of transformers of the transformer unit 181 of the upper converter circuit alternately as described with reference to FIG. 3 to magnetize inductance. Zero voltage switching can be performed. In addition, the S1 and S2 switch units 172 of the lower converter circuit may perform zero voltage switching as described above using a pair of transformers of the transformer unit 182 of the lower converter circuit.

In addition, referring to FIG. 6, in another embodiment of the present invention, the interleaved DC- is operated using a parallel structure shown in FIG. 5 and having a phase difference of 90 degrees between the switches of each of the switches S1, S2, S3, and S4. DC converters can be used.

The interleaved DC-DC converter controls the switch operation of each module so as to have a phase difference, thereby eliminating the filter inductor of the output stage as described above, and enabling zero voltage switching using magnetizing inductance. According to the operation mode, the output ripple can be greatly reduced while maintaining the characteristics of the same.

5 and 6, the output terminal 150 may further include a condenser for preventing saturation of the transformer.

7 is a flowchart illustrating a method of operating a DC-DC converter according to an embodiment of the present invention.

Referring to FIG. 7, first, the first input side switch 121 and the first output side switch 141 are turned on to operate the first transformer 131 (S100).

Then, the second input side switch 132 and the second output side switch 142 connected to the second transformer 132 are turned off (S110). Here, since the output side switch 142 is OFF, the second transformer 132 may not perform a power transmission operation and may charge energy with magnetization inductance (S120).

Thereafter, when the predetermined time passes, the first input side switch 121 is turned off (S130). When the first input side switch 121 is turned off, due to the magnetization inductance of the second transformer 132 stored in step S120, the voltage of the second input side switch 122 is maintained and then decreased for a predetermined transition time.

In operation S140, it is determined whether the voltage at both ends of the second input side switch 122 becomes 0V.

Thereafter, the second input side switch 122 is changed to ON when the voltage across the second input side switch 122 becomes OV (S150). As such, since the voltage across the switch can be turned on at 0V, zero voltage switching is performed to switch to the power supply by the second transformer 132.

As described above, the DC-DC converter and the operation method thereof according to the present invention enable the design of an output stage that does not require a filter inductor. Then, zero voltage or zero current switching is possible by using the magnetizing inductance of the plurality of transformers. As a result, the output current is overlapped to reduce the ripple component, and there is an advantage of reducing the conduction loss and the core loss due to the inductor even in a large current output.

On the other hand, it is possible to solve the problems of PCB and busbar shape and path design in the design of the large current output pattern according to the inductor insertion.

In particular, the zero voltage switching of all the switches is possible through the magnetizing inductance of the transformer itself without the need for adding a general leakage inductance or resonant inductor, thereby minimizing the current parasitic component.

In addition, since the plurality of transformers in the above-described DC-DC converter can all be manufactured with the same specification, the effect of reducing the performance deterioration due to an increase and a deviation of the design parameters of the transformer can also be brought.

The operating method of the DC-DC converter according to the present invention described above may be stored in a computer-readable recording medium that is produced as a program for execution in a computer, and examples of the computer-readable recording medium include ROM, RAM, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and the like, and also include those implemented in the form of carrier waves (eg, transmission over the Internet).

The computer readable recording medium may be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. And, functional programs, codes and code segments for implementing the above method can be easily inferred by programmers of the technical field to which the present invention belongs.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It should be understood that various modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

110: input terminal 121, 122: input side switch unit
131, 132: transformer section 141, 142: output side switch section
150: output stage

Claims (13)

In DC-DC converter,
A plurality of transformers for transforming power supplied from the input terminal to the input side coil and transferring the power to the output side coil;
An input switch unit including a plurality of input side switches for alternately operating the plurality of transformers;
An output stage for outputting power output from the output side coil;
An output switch unit including a plurality of output side switches operating in accordance with operations of the plurality of input side switches, and supplying power to the output terminals;
A control unit controlling an operation of the plurality of input side switches and the plurality of output side switches,
And the input switch unit alternately operates the plurality of transformers by switching at zero voltage using the magnetizing inductance of some of the plurality of transformers. The method of claim 1,
Further comprising a rectifier for rectifying the power output from the output side coils of the plurality of transformers,
The rectifier includes a at least one of a synchronous rectifier switch or a diode rectifier. The method of claim 2,
The input switch unit is a DC-DC converter that is switched when the current of the rectifier is zero current or voltage is zero voltage. The method of claim 1,
The input coils of the plurality of transformers are connected in series, and the output coils of the plurality of transformers are connected in parallel. The method of claim 1,
The plurality of transformers includes a first transformer and a second transformer,
When an input voltage is applied to the DC-DC converter, when the first input side switch for operating the first transformer is turned on, the second input side switch for operating the second transformer is turned off to magnetize inductance of the second transformer. DC-DC converter that is charged. The method of claim 5,
And the input switch unit turns off the second input side switch when the first input side switch is turned off and the voltage across the second input side switch is zero voltage. The method of claim 1,
The plurality of input-side switches are connected in a full bridge form DC-DC converter, characterized in that for controlling to alternately switch. The method of claim 1,
The plurality of input side switches are composed of a plurality of modules, the control unit is a DC-DC converter for controlling the switching to be performed alternately by operating the plurality of modules simultaneously. The method of claim 1,
The plurality of input side switch is composed of a plurality of modules, the control unit is a DC-DC converter for switching the plurality of modules to have a phase difference of 90 degrees each. 10. The method according to claim 8 or 9,
The output terminal further comprises a capacitor for preventing saturation of the plurality of transformers. In the operation method of the DC-DC converter,
Connecting a first input side switch, a second input side switch, a first output side switch, and a second output side switch for alternating operation of the first transformer and the second transformer;
Supplying input power;
Turning off the second input side switch and the second output side switch while turning on the first input side switch and the first output side switch;
Turning off the first input side switch and the first output side switch; And
And turning on the second input side switch and the second output side switch when the voltage across the second input side switch is zero voltage. 12. The method of claim 11,
Turning off the second input side switch and the second output side switch,
Method of operating a DC-DC converter comprising the step of charging the magnetizing inductance of the second transformer. 12. The method of claim 11,
And connecting input coils of the first transformer and the second transformer in series, and connecting the output coils of the first transformer and the second transformer in parallel.

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