KR20190099667A - Low-profile DC-DC Converter - Google Patents

Abstract

The present invention provides a low-profile DC-DC converter capable of size reduction. According to an embodiment of the present invention, the low-profile DC-DC converter comprises: a switch unit to switch an input voltage; a primary transformer including a multi-layer PCB with a primary coil, and generating a magnetic field by a voltage received from the switch unit; a secondary transformer including a multi-layer PCB with a secondary coil, and outputting a voltage induced by a magnetic field generated by the primary transformer; a rectifying unit to rectify a voltage outputted from the secondary transformer; a secondary wireless control unit to detect an output voltage of the rectifying unit to transmit the output voltage via short-range wireless communication; and a primary wireless control unit to receive an output voltage transmitted from the secondary wireless control unit via short-range wireless communication, and transmit a control signal in accordance with a change of the output voltage to the switch unit to adjust the output voltage. The switch unit, the primary transformer, and the primary wireless control unit are realized on a primary PCB. The secondary transformer, the rectifying unit, and the secondary wireless control unit are realized on a secondary PCB. An insulation layer may be inserted between the primary and the secondary PCB.

Description

Thin DC-DC Converters {Low-profile DC-DC Converter}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin DC-DC converter, and more particularly, to a thin DC-DC converter that transmits wireless power by electromagnetic induction and controls feedback of an output voltage by using near field communication.

With the rapid development of the electronics industry, a wide range of technological advances are being widely used in computers, calculators, electronic exchangers, audiovisual equipment, and communication equipments using switch-mode power supply (SMPS) power supplies. Recently, it has been actively discussed in the industrial field such as power factor improvement circuit, motor driving circuit, electronic ballast circuit, and the like, which requires diversification of required voltage and miniaturization and weight reduction of equipment. In particular, the small size and light weight in portable products have become an important goal to improve the productability, such as the performance of the product. The power supply unit for supplying power to these portable electronic devices has been difficult to compact and lightweight due to its unique characteristics. Low profile, which is required for on-board power supply, is one of the important R & D goals because it improves the density of the whole system. However, in switching DC / DC converters, in the process of converting energy, the size of the device is limited due to the size of the transformer, which is generally due to the use of a large ferrite core with a magnet wire winding. There are times when it is difficult to influence the cost much.

For high density, small size and light weight of existing power module, design and manufacture of power module considering actual operating conditions such as heat dissipation and optimized design of transformer for power conversion and heat dissipation are important factors. In the case of the conventional high-density power supply module, the switching frequency is generally driven from 100 to 300 kHz, and due to the application of the general winding type transformer, it is possible to solve the heat dissipation problem due to the heat generation problem as well as the error of the device characteristics, the deviation of the operating characteristics, and the difficulty of mass production. In addition, the situation includes a number of factors that are problematic in reliability.

In addition, switching DC / DC converters use transformers to overcome input and output voltage differences and electrical isolation, requiring safer electrical isolation, especially when high output voltages or electrical safety objectives are required. In order to satisfy this requirement, a constant distance between the primary side and the secondary side of the transformer must be maintained. However, the longer the insulation distance, the more complicated the structure of the transformer becomes, and it becomes difficult to minimize the size of the switching power converter.

Therefore, due to the application of the winding-type transformer, it is required to develop a technology of a DC-DC converter that can solve the heat dissipation problem due to the heat generation problem as well as the error of the device characteristics, the deviation of the operating characteristics, the mass production.

In this regard, there is a Korean Patent Publication No. 10-2013-0098973 named "DC / DC converter and a drive device having the same".

The technical problem to be solved by the present invention is to provide a thin DC-DC converter capable of increasing the insulation voltage of the transformer and miniaturization.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The thin DC-DC converter according to an embodiment of the present invention for solving the technical problem is composed of a switch unit for switching the input voltage, a multilayer PCB with a primary winding is formed, the magnetic field by the voltage input from the switch unit It consists of a primary side transformer for generating a multi-layer PCB, the secondary side winding is formed, the secondary side transformer for outputting the voltage induced by the magnetic field generated in the primary side transformer, the rectifier for rectifying the voltage output from the secondary side transformer The secondary side wireless control unit detects an output voltage of the rectifier and transmits the short-range wireless communication, and receives the output voltage transmitted from the secondary side wireless control unit through short-range wireless communication, and receives a control signal according to the change of the output voltage. And a primary side wireless control unit for transmitting the switch unit to adjust the output voltage. The transformer and the primary side wireless control unit are implemented on the primary side PCB, the secondary side transformer, rectifying unit and the secondary side wireless control unit are implemented on the secondary side PCB, and an insulating layer is inserted between the primary side PCB and the secondary side PCB. Can be.

Preferably, the primary side transformer includes a primary side multilayer PCB in which the primary side winding is formed in a pattern, and a primary side core surrounding an edge of the primary side multilayer PCB, wherein the secondary side transformer includes: It may include a secondary side multilayer PCB formed in a pattern, the secondary side core surrounding the edge of the secondary side multilayer PCB.

Preferably, the secondary-side wireless control unit compares the output voltage detected by the voltage distribution module and the output voltage detected by the voltage distribution module with the preset reference voltage, and the difference according to the comparison result as a PWM signal It may include a voltage conversion module for outputting, the secondary short-range wireless communication module for transmitting the PWM signal output from the voltage conversion module to the primary wireless control unit in the near field communication.

Preferably, the primary wireless control unit, the primary short-range wireless communication module for receiving the PWM signal transmitted from the secondary short-range wireless communication module, PWM for amplifying the PWM signal received through the primary short-range wireless communication module An amplification module, a PWM signal filter module for filtering the PWM signal amplified by the PWM amplification module and converting it into an analog control voltage, and changing a frequency according to the magnitude of the control voltage provided from the PWM signal filter module, It may include a PFM control module for generating a control signal according to the control unit.

Preferably, the insulating layer may be located between the primary side transformer and the secondary side transformer to transfer the heat generated from the insulation and the inside of the primary side transformer and the secondary side transformer to the outside.

Preferably, the thin DC-DC converter may further include an input impedance matching unit between the switch unit and the primary side transformer.

Preferably, the thin DC-DC converter may further include an output impedance matching unit between the secondary side transformer and the rectifier.

Preferably, the thin DC-DC converter may further include an external device interface unit connected to the primary side wireless control unit or the secondary side wireless control unit and connected to an external device for real time monitoring of the thin DC-DC converter. .

According to the present invention, by configuring the transformer as a multilayer PCB, it can have several advantages such as low leakage inductance, excellent thermal properties, minimum skin effect, high power density, low parasitic reactance, light weight, low profile.

In addition, the use of PCB-type windings in multi-layer PCB transformers simplifies the manufacturing process of transformers and inductors, saves manufacturing cost and time, achieves maximum current density and efficiency for a given conductor weight, and eliminates parasitic factors. The effect is reduced to minimize high frequency ringing at the output voltage.

In addition, by inserting an insulating layer (ceramic layer) in the multilayer PCB, the insulation effect between the primary side and the secondary side of the transformer can be increased, and heat generated inside can be transferred to the outside, thereby eliminating the heat dissipation problem caused by heat generation problems. can do.

Effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a view for explaining a thin DC-DC converter according to an embodiment of the present invention.
2 is a vertical cross-sectional view of a thin DC-DC converter according to an embodiment of the present invention.
3 is an exploded view of a transformer implemented with a multilayer PCB according to an embodiment of the present invention.
4 is a diagram for describing a primary side wireless control unit and a secondary side wireless control unit in a thin DC-DC converter according to an exemplary embodiment of the present invention.
5 is a diagram illustrating an example of a device used in a short range wireless communication module according to an embodiment of the present invention.
6 is a circuit diagram of a DC-DC converter except for the first and second controllers according to an exemplary embodiment of the present invention.
FIG. 7 is a circuit diagram illustrating conduction resistance of main elements for power loss analysis of the converter illustrated in FIG. 6.
8 is a graph showing the theoretical efficiency according to the output power state of the WTP (Wireless Power Transmission) converter.
9 is a graph showing the loss according to the output power state of the WTP converter.
FIG. 10 is a view illustrating operating waveforms of a simulation converter at low power and high power according to an embodiment of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view for explaining a thin DC-DC converter according to an embodiment of the present invention, Figure 2 is a vertical cross-sectional view of a thin DC-DC converter according to an embodiment of the present invention, Figure 3 is an embodiment of the present invention 4 is an exploded view of a transformer implemented with a multilayer PCB according to an example, FIG. 4 is a view illustrating a primary side wireless control unit and a secondary side wireless control unit in a thin DC-DC converter according to an embodiment of the present invention, and FIG. FIG. Is a diagram illustrating an example of a device used in a short range wireless communication module according to an exemplary embodiment.

Referring to FIG. 1, a low-profile DC-DC converter 100 according to an exemplary embodiment of the present invention includes a switch unit 110, a transformer 120, a rectifier 130, and a secondary side wireless controller 160. ), The primary side wireless control unit 170, and the insulating layer 180. In addition, the thin DC-DC converter 100 includes an input impedance matching unit 140 between the switch unit 110 and the transformer 120, and an output impedance matching unit 150 between the transformer 120 and the rectifying unit 130. It may further include.

The thin DC-DC converter of this configuration is implemented on the PCB as shown in FIG. That is, a switch unit 110, a primary side transformer 120a), an input impedance matching unit 140, and a primary side wireless control unit 170 are implemented in the primary side PCB, and the secondary side transformer 120b is implemented in the secondary side PCB. The output impedance matching unit 150 and the secondary side wireless control unit 160 are implemented, and an insulating layer 180 is inserted between the primary side PCB and the secondary side PCB.

The switch unit 110 switches the input voltage.

The switch unit 110 may be configured as a half bridge structure having two switches Q ₁ and Q ₂ , and the two switches may be switched on and under the switching control of the primary side wireless control unit 170. Can be turned off. That is, the two switches Q ₁ and Q ₂ of the switch unit 100 are alternately turned on / turned off in response to a control signal transmitted from the primary side wireless control unit 170 to convert a transformer ( The voltage applied to the primary winding of 120 is controlled. Since the half bridge is generally a well-known switch structure, a detailed description of the operation will be omitted.

The transformer 120 includes a primary side transformer 120a having a primary winding formed of a multilayer PCB on a primary side PCB, a secondary side transformer 120b having a secondary winding formed of a multilayer PCB on a secondary side PCB, and a switch unit. The voltage input from the 110 through the primary winding is output through the secondary winding in an electromagnetic induction manner. At this time, the transformer 120 converts the voltage input through the primary side winding according to the turns ratio of the primary side winding and outputs it through the secondary side winding. Inside a multilayer PCB transformer, the common winding is replaced by a PCB, with each layer representing one turn of the winding.

The transformer 120 is made of a multi-layer PCB, thereby having several advantages such as low leakage inductance, excellent thermal properties, minimal skin effect, high power density, low parasitic reactance, light weight, low profile. In addition, PCB-type windings used in multilayer PCB transformers are optimized to achieve maximum current density and efficiency for a given conductor weight. In addition, the effects of parasitic elements are reduced, minimizing high frequency ringing at the output voltage.

The transformer 120 includes a primary side transformer 120a and a secondary side transformer 120b as shown in FIG. 2, and the primary side transformer 120a includes a primary side core 121a and a primary side multilayer PCB 122. ), And the secondary side transformer 120b includes a secondary side core 121b and a secondary side multilayer PCB 123.

The primary side core 121a surrounds the edge of the primary side multilayer PCB 122 and the secondary side core 121b surrounds the edge of the secondary side multilayer PCB 123. The primary core 121a and the secondary core 121b may be, for example, an E-plane core as shown in FIG. 3.

The primary core 121a and the secondary core 121b of the transformer 120 are vertically held and directly fixed to the insulating layer 180 having excellent electrical insulating properties.

The primary side multilayer PCB 122 has a primary winding formed in a pattern and is connected to the switch unit 110. Accordingly, the primary side multilayer PCB 122 receives the switched voltage from the switch unit 110, is induced to the input voltage, and changes the magnetic flux with time.

The secondary side multilayer PCB 123 has a secondary winding formed in a pattern, is spaced a predetermined distance in a vertical direction in parallel to the primary side multilayer PCB 122, and shares the magnetic flux provided from the primary side multilayer PCB 122.

The primary multilayer PCB 122 and the secondary multilayer PCB 123 are each composed of a plurality of PCBs as shown in FIG. 3, and each PCB may form a conductive layer.

An insulating layer 180 is positioned between the primary side transformer 120a and the secondary side transformer 120b having the above-described configuration to implement insulation between the primary side transformer 120a and the secondary side transformer 120b. In this case, the insulating layer 180 may be, for example, a ceramic layer made of ceramic.

Accordingly, since the primary side transformer 120a and the secondary side transformer 120b are separated up and down around the insulating layer 180, the electrical insulation characteristics may be increased. Since the insulating layer 180 is formed in a PCB state, the DC-DC converter 100 may be miniaturized and lightweight. In addition, the windings and the cores of the primary and secondary transformers 120a and 120b may be in contact with the insulating layer 180 to transfer heat generated therein to the outside. That is, the insulating layer 180 serves as a heat pipe. Through this, since heat generated in the core 121 of the transformer 120 may be reduced, the core 121 may be miniaturized.

As such, the transformer 120 inserts an insulating layer 180 between the primary side transformer 120a and the secondary side transformer 120b to achieve complete insulation and physical separation to achieve wireless power transmission. In addition, if the insulating layer 180 is formed between the primary side transformer 120a and the secondary side transformer 120b, the heat generated when the power supply is driven is effectively discharged and thus serves as one heat pipe.

In addition, the inductance of the resonance network for wireless power transmission may be adjusted by adjusting the thickness of the insulating layer 180. The thickness of the insulating layer 180 may be configured, for example, from a minimum of 0.2T to a maximum of 1.0T.

The first and second switches Q ₁ and Q ₂ of the switch unit 110 operate at a controlled frequency and duty ratio to generate a resonant pulse voltage, and the resonant pulse voltage is input to the primary winding to form a turns ratio and a coupling coefficient. As a result, a certain amount of voltage is delivered to the secondary winding. Then, the transformer 120 transmits a voltage (power) by using a resonance phenomenon between the primary winding and the secondary winding. That is, the transformer 120 transmits wireless power in a magnetic resonance method.

As described above, the transformer 120 may increase the efficiency and lower the prototype height by inserting the insulating layer 180 between the primary side transformer 120a and the secondary side transformer 120b. In addition, by designing the winding of the transformer 120 in a PCB pattern, it is possible to minimize the height.

The transformer 120 is composed of flat PCB type layers, such as low leakage inductance, excellent thermal characteristics, minimal skin effect, high power density, low parasitic reactance, light weight and low profile. May have PCB-type windings used in multilayer PCB transformers are optimized to achieve maximum current density and efficiency for a given conductor weight. In addition, the effects of parasitic elements are reduced, minimizing high frequency ringing at the output voltage.

Since the PCB transformer 120 does not use windings, the manufacturing process of the transformer and the inductor is simplified, and the manufacturing cost and time are saved. It is also designed to be used for all types of power supply topologies at high switching frequencies. It guarantees high reliability and constant operation for a long time, and can get high power density, and can be made smaller and lighter.

The rectifier 130 rectifies the transformed voltage from the secondary winding of the transformer 120. That is, the rectifier 130 may be connected to the secondary winding of the transformer 120 and may output a DC voltage by receiving an induced voltage according to the winding ratio of the primary winding.

The rectifier 130 generates a DC voltage using energy provided from the transformer 120 using four diodes D ₁ , D ₂ , D ₃ , and D ₄ and a capacitor. That is, the rectifier 130 rectifies the voltage provided from the secondary winding of the transformer 120 by using a diode. Thereafter, the rectifier 130 smoothes the voltage rectified through the capacitor to generate a DC voltage. Here, the diode must be able to withstand forward current capability and reverse voltage, and the capacitor performs high frequency noise cancellation.

That is, the rectifier 130 rectifies the high frequency pulse transmitted from the transformer 120 and converts it into a DC voltage. For example, the rectifier 130 may be configured as a full-wave rectifier circuit.

As described above, the power applied to the primary winding of the transformer 120 generates a magnetic field, which induces electromotive force on the secondary winding of the transformer 120. The electromotive force induced in the secondary winding of the transformer 120 is converted into direct current by the rectifier 130 composed of a diode and a capacitor and output.

In this case, the transformer 120 is electrically insulated from the primary side and the secondary side, so that the primary side and the secondary side can be separated as necessary. In this case, the power transfer between the primary side and the secondary side is mediated by the magnetic flux generated at the primary side, and the closer the separated transformer 120 is, the higher the power transfer efficiency and the coupling ratio are. Such a transformer 120 may be used where it is necessary to transfer energy efficiently without using electrical contact such as a contactless charger.

The input impedance matching unit 140 is composed of a resonant element and makes the current waveform of the transformer 120 a stabilized sinusoidal wave.

The output impedance matching unit 150 allows the output waveform of the transformer secondary winding to be a stabilized sinusoidal wave.

On the other hand, the present invention is a method for solving the heat generated by the power loss generated during the power conversion process is provided with an insulating layer 180 to solve the ceramic or insulation and heat dissipation between the transformer for wireless power transmission. Although the primary side and the secondary side of the transformer 120 are in a very close position, the method for transmitting an electrical signal is not technically easy due to the insulating layer 180 provided therebetween. Thus, the present invention transmits a signal for feedback control of the output voltage using a short-range wireless communication device such as Bluetooth, Wi-Fi, and the like. In this case, since the signal transmission distance is close, there is no need to install an antenna for wireless transmission and reception, and the influence of external radio interference is small.

That is, the thin DC-DC converter 100 according to the present invention includes a secondary side wireless control unit 160 and a primary side wireless control unit 170 for transmitting and receiving a signal through short-range wireless communication for feedback control of the output voltage.

The secondary side wireless control unit 160 includes a secondary side short range wireless communication module 163 and detects an output voltage of the rectifying unit 130 to the primary side wireless control unit 170 through the secondary side short range wireless communication module 162. send.

The secondary side wireless control unit 160 includes a voltage distribution module 161, a voltage conversion module 162, and a secondary side short range wireless communication module 163.

The voltage distribution module 161 measures the output voltage of the rectifier 130 and transmits it to the voltage conversion module 162. That is, the voltage distribution module 161 is provided with a resistor (R1) and a resistor (R2) connected in series between the output terminal and the ground terminal as shown in Figure 4, by using two resistors (R1, R2) The voltage of the predetermined ratio is distributed from the voltage output from the rectifier 130 and transmitted to the voltage conversion module 162. In this case, the voltage output from the voltage distribution module 161 may be an analog voltage value. In FIG. 4, the voltage distribution module 161 is composed of two resistors R1 and R2, but resistance conditions may be variously configured.

The voltage conversion module 162 compares the analog output voltage output from the voltage distribution module 161 with a preset reference voltage, and outputs a difference according to the comparison result as a PWM signal. Here, the voltage conversion module 162 may be implemented with, for example, an LMZ21700 device.

The secondary short-range wireless communication module 163 transmits the PWM signal output from the voltage conversion module 162 to the primary wireless controller 170 through short-range wireless communication. At this time, the secondary short-range wireless communication module 163 may be implemented, for example, Bluetooth, Wi-Fi, ESP32.

The primary wireless controller 170 is provided with a primary short-range wireless communication module 171, receives the PWM signal transmitted from the secondary wireless control unit 160 through the primary short-range wireless communication module 171, and outputs an output voltage. The control signal according to the change of the control unit 110 transmits the output voltage.

The primary wireless controller 170 may include a primary short-range wireless communication module 171, a pulse width modulator (PWM) amplification module 172, a PWM signal filter module 173, and a pulse frequency modulation (PFM) control module 174. And a switch insulation driving module 175.

The primary short-range wireless communication module 171 receives the PWM signal transmitted through the secondary short-range wireless communication module 163 and transmits the PWM signal to the PWM amplification module 172. At this time, the primary short-range wireless communication module 171 may be implemented, for example, Bluetooth, Wi-Fi, ESP32.

The PWM amplification module 172 amplifies the PWM signal received through the primary side short-range communication module 171. In this case, the PWM amplification module 172 may be implemented with, for example, a transistor.

The PWM signal filter module 173 filters and converts the PWM signal amplified by the PWM amplification module 172 into an analog signal. Here, the analog signal may be a control voltage, and the PWM signal filter module 173 may be implemented with, for example, LPF.

The PFM control module 174 changes the frequency according to the magnitude of the control voltage provided from the PWM signal filter module 173 and generates a control signal according to the changed frequency. That is, the PFM control module 174 uses the PFM method to control the output voltage by varying the switching frequency of the switch unit 110. Accordingly, the PFM control module 174 causes the switch isolation driver 175 to control the switch 110 so that the output voltage is maintained at the reference voltage according to the control voltage provided from the PWM signal filter module 173. . That is, the PFM control module 174 operates the switch unit 110 when the output voltage is lower than the reference voltage, and does not operate the switch unit 110 when the output voltage is higher than the reference voltage. Keep it. In this case, a section in which the switch unit 110 operates becomes a burst section, and a section in which the switch unit 110 does not operate becomes an idle section. Therefore, the PFM mode is largely divided into a burst section and an idle section.

The PFM control module 174 may be implemented with, for example, an NCP1395 device.

The switch insulation driver 175 outputs a control signal generated by the PFM control module 174 to the control terminal of the switch unit 110. Then, the switch 110 performs an on / off operation according to the control signal.

On the other hand, the thin DC-DC converter according to the present invention may further include an external device interface 190 that can be connected to an external device to enable real-time monitoring of the thin DC-DC converter. For example, when the primary side or secondary side short-range wireless communication module (163, 171) is implemented with the ESP32 element as shown in Figure 5, the internal function of the ESP32 has a communication function such as I2C, CAN, Ethernet, etc. that can be wired communication with the outside Therefore, real time monitoring necessary for maintenance of power supply is possible. The ESP32 device is capable of short-range wireless communication such as Bluetooth and Wi-Fi in one device, and can be miniaturized by incorporating dual microprocessors.

FIG. 6 is a circuit diagram of a DC-DC converter excluding the primary and secondary wireless controllers according to an exemplary embodiment of the present invention. FIG. 7 is a circuit diagram illustrating conduction resistance of main elements for power loss analysis of the converter illustrated in FIG. 6. 8 is a graph showing the loss according to the output power state of the thin DC-DC converter, Figure 9 is a graph showing the theoretical efficiency according to the output power state of the thin DC-DC converter.

In designing a low-profile DC-DC converter for wireless power transmission, it is important to design the optimal semiconductor components and to understand the power loss of the power supply. Accordingly, the power P _L lost in the DC-DC converter may be derived using the on resistance of each device of the DC-DC converter as shown in FIG. 6 and the RMS current flowing through the device. Since the circuit of the DC-DC converter shown in FIG. 6 is a general configuration, a detailed description thereof will be omitted and the power lost in the DC-DC converter will be described.

RMS current I _S1 flowing through the first switch S1 of the switch unit _rms is equal to Equation 1 below, and the RMS current I _S2 flowing through the second switch _{S2. rms} ) is shown in Equation 2 below. The current flowing through the switch is determined by the output current (Io), the transformer's turns ratio, and the L _M resonant frequency (f _R ).

[Equation 1]

[Equation 2]

RMS current flowing through the transformer's primary resonant inductor (L _R ) (I _{LR) rms} ) can be calculated using Equation 3 below, and the RMS current I _LM flowing through the magnetic inductor L _{M rms} ) can be calculated using Equation 4 below.

[Equation 3]

[Equation 4]

Therefore, the current effective value I _{P rms} flowing in the primary side of the transformer can be calculated using Equation 5 described below.

[Equation 5]

The effective current value (I _{D1 rms} ) flowing through each rectifier diode of the secondary side can be calculated using Equation 6 below, and the power loss of the rectifier diode used in the converter is the effective current value flowing through the diode and the forward voltage of the diode. Is determined by (V _F ).

[Equation 6]

의 기본 전력 수식에 대입하여 알 수 있다.In this way, the RMS current flowing through the low-profile DC-DC converter for WTP (Wireless Power Transmission) can be summarized as a mathematical formula to calculate the conduction loss occurring in each device.

This can be found by substituting the basic power equation for.

7 shows the main resistance values of the WPT Converter circuit components. Since the effective current value flowing through each major element can be calculated using Equations 1 to 6, the theoretical value for power loss of the low-profile DC-DC converter can be derived.

The input and output characteristics and the specifications of the main elements used in the embodiment of the present invention are shown in Table 1.

TABLE 1

The actual current flowing through the module can be obtained by substituting the specifications and specifications of the actual WPT converter in Table 1 into Equations 1 to 6, and the derived value is obtained by using the on resistance of the converter. By substituting 9, the efficiency and power loss of the WTP converter can be obtained. And the theoretical efficiency and loss graph according to the output power state of the low-profile DC-DC converter can be drawn and its characteristics are as shown in Figs.

[Equation 7]

Here, P _IN may be input power, P _O may be output power, and P _L may be lost power.

[Equation 8]

[Equation 9]

As a result of analyzing the power loss of the WPT converter using the above equation, a maximum efficiency of about 93% is obtained when the output power is 500W, and power loss is generated at 35W. Based on these values, the optimal design of the low-profile DC-DC converter can be achieved by reflecting the heat radiation analysis and device selection of the WPT converter.

FIG. 10 is a view illustrating operating waveforms of a simulation converter at low power and high power according to an embodiment of the present invention.

10, the waveform (V _GS1, V _GS2), the resonant current (i _{LR, LM i)} of the primary winding of the transformer of the switch control _voltage, and indicate the voltage (V _T) of the secondary side of the transformer. (a) is an operating waveform under the condition that the input voltage is about 400V and the switching frequency is 1MHz. It can be seen that the resonant current waveform is triangular because of the magnetizing inductance induced by the low output current. (b) is the waveform measured under the condition of medium output and input voltage of 400V. (c) is the waveform measured under the maximum output and 400V input voltage. The current waveforms on the primary and secondary sides of the transformer are sinusoidal because they resonate with a switching frequency of 1 MHz.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

100: low-profile DC-DC converter
110: switch unit
120: transformer
130: rectifier
140: input impedance matching unit
150: output impedance matching unit
160: secondary wireless control unit
170: primary wireless control unit
180: insulation layer
190: external device interface unit

Claims (8)

A switch unit for switching an input voltage;
A primary side transformer formed of a multilayer printed circuit board (PCB) having a primary winding, and generating a magnetic field by a voltage input from the switch unit;
A secondary side transformer formed of a multilayer PCB having secondary side windings and outputting a voltage induced by a magnetic field generated in the primary side transformer;
A rectifier for rectifying the voltage output from the secondary transformer;
A secondary side wireless control unit which detects an output voltage of the rectifying unit and transmits the output voltage through short range wireless communication; And
And a primary side wireless control unit which receives the output voltage transmitted from the secondary side wireless control unit through short range wireless communication and transmits a control signal according to the change of the output voltage to the switch unit to adjust the output voltage.
The switch unit, the primary side transformer and the primary side wireless control unit are implemented on the primary side PCB, and the secondary side transformer, the rectifying unit and the secondary side wireless control unit are implemented on the secondary side PCB, and the primary side PCB and the secondary side PCB Thin DC-DC converter, characterized in that the insulating layer is inserted between. The method of claim 1,
The primary side transformer,
A primary multilayer PCB in which the primary winding is formed in a pattern; And
A primary core surrounding an edge of the primary multilayer PCB,
The secondary side transformer,
A secondary multilayer PCB in which the secondary winding is formed in a pattern; And
And a secondary side core surrounding the edge of the secondary side multilayer PCB. The method of claim 1,
The secondary side wireless control unit,
A voltage distribution module detecting an output voltage of the rectifier;
A voltage conversion module comparing the output voltage detected by the voltage distribution module with a preset reference voltage and outputting a difference according to the comparison result as a pulse width modulator (PWM) signal; And
And a secondary short-range wireless communication module for transmitting the PWM signal output from the voltage conversion module to the primary wireless control unit in short-range wireless communication. The method of claim 3,
The primary side wireless control unit,
A primary short-range wireless communication module configured to receive a PWM signal transmitted from the secondary short-range wireless communication module;
A PWM amplification module for amplifying the PWM signal received through the primary short-range wireless communication module;
A PWM signal filter module for filtering the PWM signal amplified by the PWM amplification module and converting the PWM signal into an analog control voltage; And
It characterized in that it comprises a PFM (Pulse Frequency Modulation) control module for changing the frequency in accordance with the magnitude of the control voltage provided from the PWM signal filter module, generating a control signal according to the changed frequency to control the switch unit DC-DC converter. The method of claim 1,
The insulating layer is
Located between the primary transformer and the secondary transformer, a thin DC-DC converter, characterized in that for transmitting the insulation and heat generated from the inside of the primary and secondary transformer to the outside. The method of claim 1,
The thin DC-DC converter further comprises an input impedance matching unit between the switch unit and the primary transformer. The method of claim 1,
The thin DC-DC converter further comprises an output impedance matching unit between the secondary transformer and the rectifying unit. The method of claim 1,
And a external device interface unit connected to the primary wireless control unit or the secondary wireless control unit and connected to an external device for real-time monitoring of the thin DC-DC converter.

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