JP2021141771A - Voltage conversion device - Google Patents

Abstract

To provide a voltage conversion device that can output a voltage to a load more appropriately.SOLUTION: A voltage conversion device 1 includes a primary circuit 10, a secondary side circuit 20 including multiple output circuits 201 to 20n, and a control unit 30 that generates a control signal of an inverter circuit 11 on the basis of a difference between each detected output voltage V1 to Vn and each command voltage, and the secondary side circuit 20 includes filter circuit 401 to 40n that transmits a frequency signal corresponding to a specific frequency between an isolated transformer T and the respective output circuits 201 to 20n. However, each of filter circuits 401 to 40n has a specific frequency different from that of the other filter circuits 401 to 40n, and the control unit 30 adjusts the amplitude of the unit sine wave corresponding to each specific frequency of each of filter circuits 401 to 40n on the basis of the difference, and generates the control signal on the basis of the composite wave of each unit sine wave whose amplitude is adjusted.SELECTED DRAWING: Figure 1

Description

The present invention relates to a voltage converter.

Conventionally, an isolated DC / DC converter (voltage converter) that outputs two different voltages by using one inverter and one transformer has been proposed (see Non-Patent Document 1).

FIG. 4 is a circuit configuration diagram showing a voltage conversion device according to a comparative example. As shown in FIG. 4, the voltage conversion device 100 includes a primary side circuit 110, a secondary side circuit 120, and an isolation transformer IT. The primary side circuit 110 includes an inverter circuit 111 which is connected to a power supply and has a plurality of switching elements S1 to S4. The plurality of switching elements S1 to S4 are switched at a predetermined duty ratio D and a frequency f. A voltage having a magnitude determined by the input voltage V and the duty ratio D is applied to the primary winding IT1 of the isolation transformer IT at the frequency f.

The secondary side circuit 120 includes a first output circuit 121, a second output circuit 122, and a filter circuit 123. The first output circuit 121 is interposed between the secondary winding IT2 of the isolation transformer IT and the first load Lo1, and is configured to include a switching element, an inductance, a capacitor, and the like. Similar to the first output circuit 121, the second output circuit 122 is also interposed between the secondary winding IT2 of the isolation transformer IT and the second load Lo2, and has a switching element, an inductance, and an inductance. It is configured with a capacitor and the like.

The filter circuit 123 is interposed between the secondary winding IT2 of the isolation transformer IT and the second output circuit 122, and includes a series LC filter circuit 123a and a parallel LC filter circuit 123b. .. The series LC filter circuit 123a is a circuit whose impedance changes according to the frequency of the voltage, and the parallel LC filter circuit 123b is a circuit that prevents interference with the subsequent circuit (second output circuit 122).

FIG. 5 is a diagram showing the impedance characteristics of the series LC filter circuit 123a shown in FIG. As shown in FIG. 5, the series LC filter circuit 123a has a characteristic that the impedance Z increases as the frequency increases in a region of a predetermined frequency f'or higher.

The voltage conversion device 100 according to such a comparative example operates as follows when the resistance of the first load Lo1 is small and the resistance of the second load Lo2 is large. First, the duty ratio D at the time of switching of the inverter circuit 111 is determined according to the magnitude of the resistance of the first load Lo1. Here, since the resistance of the first load Lo1 is small, the required current value is large and the duty ratio D is also large. Further, the frequency f at the time of switching of the inverter circuit 111 is determined according to the magnitude of the resistance of the second load Lo2. Here, since the resistance of the second load Lo2 is large, the frequency f is determined so that the required current value becomes small and the impedance Z becomes large. Then, the plurality of switching elements S1 to S4 are switched so that the determined duty ratio D and the frequency f are achieved.

In the secondary circuit 120, electric power corresponding to the duty ratio D can be obtained, but since the duty ratio D is determined according to the magnitude of the resistance of the first load Lo1, it is supplied to the first output circuit 121. The power supply is insufficient by the amount of power supplied to the second output circuit 122. Therefore, in order to make up for the shortage, the duty ratio D of the inverter circuit 111 in the primary side circuit 110 is increased based on the feedback signal (actual voltage Vd) of the first output circuit 121. As a result of the increase in the duty ratio D, the feedback signal (actual voltage Vf) of the second output circuit 122 ^{exceeds the command voltage Vf *} , and the frequency f increases in order to suppress the actual voltage Vf. The electric power cut due to the increase in frequency f is transmitted to the first output circuit 121.

If the actual voltage Vd of the first output circuit 121 ^{is less than the command voltage Vd *} in a state where the frequency f is increased, the duty ratio D is further increased. Then, the above operation is repeated. On the other hand, when the actual voltage Vd of the first output circuit 121 ^{exceeds the command voltage Vd *} in a state where the frequency f is increased, the duty ratio D is reduced. When the duty ratio D is reduced, the frequency f is reduced and the impedance Z is also reduced to guarantee it. When the impedance Z becomes smaller, the actual voltage Vd supplied to the first output circuit 121 becomes smaller. After that, the above is repeated until the command voltages Vd ^* and Vf ^{* are achieved.}

Semiconductor Power Conversion / Motor Drive Joint Study Group of the Institute of Electrical Engineers of Japan (2018.1.19-2018.1.20) "Dual port output control of DC / DC converter focusing on the duty cycle and frequency of the inverter"

However, the voltage converter described in Non-Patent Document 1 cannot satisfy the requirements as follows when the resistance of the first load Lo1 is large and the resistance of the second load Lo2 is small. First, since the resistance of the first load Lo1 is large, the required current value is small, and the duty ratio D is also small. Further, since the resistance of the second load Lo2 is small, the frequency f is determined so that the required current value becomes large and the impedance Z becomes small. After that, even if the impedance Z is operated at the minimum frequency f, the duty ratio D is determined according to the large resistance of the first load Lo1. Therefore, the duty ratio D is the command voltage Vf ^{* from the second load Lo2 side.} It does not increase until it satisfies, and the command voltage Vf ^* cannot be satisfied.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a voltage conversion device capable of outputting a voltage more appropriately to a load. ..

The power conversion device according to the present invention includes a primary side circuit that is connected to a power source and controls the primary side output voltage by a switching element, and a plurality of output circuits for outputting a required output voltage according to different command voltages. A transformer that insulates between the secondary side circuit including the primary side circuit, the primary side circuit, and the secondary side circuit, and supplies a voltage corresponding to the primary side output voltage to the secondary side circuit, and the plurality of transformers. The switching element is switched based on the difference between the plurality of voltage detectors that detect the output voltage of each output circuit and the respective output voltages detected by each of the plurality of voltage detectors and the respective command voltage. A control signal generator for generating a control signal for the purpose is provided, and the secondary circuit is a filter circuit that transmits a frequency signal corresponding to a specific frequency between the transformer and each of the plurality of output circuits. Each of the filter circuits has a different frequency from the other filter circuits, and the control signal generator sets the specific frequency of each of the filter circuits based on the difference. The amplitude of the corresponding unit waveform signal is adjusted, and a control signal is generated based on the composite wave of each unit waveform signal whose amplitude has been adjusted.

According to the present invention, it is possible to provide a voltage conversion device capable of outputting a voltage more appropriately with respect to a load.

It is a circuit block diagram of the voltage conversion apparatus which concerns on this embodiment. It is a figure which shows the impedance characteristic of a plurality of series LC filter circuits. It is a block diagram which shows the detail of the control part shown in FIG. It is a circuit block diagram which shows the voltage conversion apparatus which concerns on a comparative example. It is a figure which shows the impedance characteristic of the series LC filter circuit shown in FIG.

Hereinafter, the present invention will be described with reference to preferred embodiments. The present invention is not limited to the embodiments shown below, and can be appropriately modified without departing from the spirit of the present invention. Further, in the embodiments shown below, some parts of the configuration are omitted from the illustration and description, but the details of the omitted technology are within a range that does not conflict with the contents described below. Needless to say, publicly known or well-known techniques are appropriately applied.

FIG. 1 is a circuit configuration diagram of the voltage conversion device according to the present embodiment. The voltage conversion device 1 according to the present embodiment is mounted on a vehicle, for example, and is a device that outputs a plurality of required output voltages according to different command voltages by using one power source E, and is a direct current. It is a DC / DC converter that converts voltage to DC voltage. The voltage conversion device 1 includes a primary side circuit 10, a secondary side circuit 20, an isolation transformer (transformer) T, and a control unit (control signal generation unit) 30. The primary side circuit 10 and the secondary side circuit 20 are insulated by an isolation transformer T.

The primary side circuit 10 has an inverter circuit 11 and is configured such that the input side is connected to the DC power supply E and the output side is connected to the primary side winding T1 of the isolation transformer T. The primary side circuit 10 applies the primary side output voltage Vt1 to the isolation transformer T.

The power source E is, for example, a secondary battery capable of repeating charging and discharging, and outputs a DC voltage to the output side (isolation transformer T side). The output side of the power supply E is connected to the inverter circuit 11, and a DC voltage is applied to the inverter circuit 11.

The inverter circuit 11 includes a plurality of switching elements SW, generates a voltage pulse signal by switching the plurality of switching elements SW, and controls the primary output voltage Vt1 applied to the isolation transformer T. be. In the inverter circuit 11, the input side is connected to the power supply E, and the output side is connected to the primary winding T1 of the isolation transformer T.

Although the inverter circuit 11 shows two switching elements SW in FIG. 1, the inverter circuit 11 is not particularly limited to two, and may include one or three or more. Further, the inverter circuit 11 may have any configuration as long as the primary output voltage Vt1 can be controlled by switching the switching element SW.

The isolation transformer T insulates between the primary side circuit 10 and the secondary side circuit 20, and includes a primary side winding T1 and a secondary side winding T2. This isolation transformer T supplies the secondary side output voltage Vt2 corresponding to the primary side output voltage Vt1 of the primary side circuit 10 to the secondary side circuit 20. That is, the isolation transformer T applies an alternating voltage to the secondary circuit 20 according to the winding ratio between the primary winding T1 and the secondary winding T2.

The secondary side circuit 20 is connected to the secondary side winding T2 of the isolation transformer T, and outputs a plurality of required output voltages corresponding to different command voltages (n (n is a natural number of 2 or more)). The output circuit 20 _{1 to} 20 _{n of the above} is included.

Each output circuit 20 _{1 to} 20 _n is provided at a branch destination branched in parallel from the secondary winding T2 of the isolation transformer T, and each is provided as a rectifier circuit 21 _{1 to} 21 _n and a voltage detection unit. It has 22 _{1 to} 22 _n . Each rectifier circuit 21 _{1 to} 21 _n is a so-called full-wave rectifier circuit, which includes a switching element, an inductance, and a capacitor. The rectifier circuits 21 _{1 to} 21 _n do not ask the circuit configuration as long as they can perform full-wave rectification. Each voltage detection unit ₂₂ 1 through 22 _n is configured to detect the output voltage _V 1 ~V _n of the output circuits ₂₀ 1 to 20 _n. The voltage detection units 22 _{1 to} 22 _n are connected in parallel with the respective rectifier circuits 21 _{1 to} 21 _n and their respective loads (not shown). The plurality of voltage detection units 22 _{1 to} 22 _n transmit signals corresponding to the output voltages V _{1 to} V _n of the plurality of output circuits 20 _{1 to} 20 _n to the control unit 30.

The control unit 30 controls the primary output voltage Vt1 by switching and controlling a plurality of switching elements SW constituting the inverter circuit 11. The control unit 30 was detected by the required output voltage (that is, the command voltage V ₁ ^{* to} V _n ^* _{) that each output circuit 20 1 to} 20 _n should supply to the load, and each voltage detection unit 22 _{1 to} 22 _n. A control signal for switching a plurality of switching elements SW is generated based on the difference between the output voltages V _{1 to} V _{n of} each output circuit 20 _{1 to 20 n.} Information on the command voltage V ₁ ^{* to} V _n ^* is stored in the control unit 30 by being stored in advance in the control unit 30, for example.

_{Further, the secondary side circuit 20 is a filter circuit 40 1} that transmits a frequency signal corresponding to a specific frequency between the isolation transformer T (secondary side winding T2) and the plurality of output circuits 20 _{1 to} 20 _n. It has ~ 40 _n . Each of the filter circuits 40 ₁ to 40 _n includes a series LC filter circuits 41 _{1 to} 41 _n and a parallel LC filter circuits 42 _{1 to} 42 _n .

Each series LC filter circuit 41 _{1 to} 41 _n has an impedance Z sufficiently reduced at a specific frequency (resonance frequency). In particular, the impedance Z of each of the series LC filter circuits 41 _{1 to} 41 _n is sufficiently increased at a specific frequency of the other series LC filter circuits 41 _{1 to} 41 _n. That is, the plurality of series LC filter circuits 41 _{1 to} 41 _n have different specific frequencies from the other series LC filter circuits 41 _{1 to} 41 _{n, and each series LC filter circuit 41 1 to} 41 n is different from the other series LC filter circuits 41 _{1 to 41 n.} The frequency signals transmitted by the LC filter circuits 41 _{1 to} 41 _{n are not substantially transmitted.} Each of the parallel LC filter circuits 42 _{1 to} 42 _n is a circuit for preventing interference with a subsequent circuit (rectifier circuit 21 _{1 to 21 n).}

FIG. 2 is a diagram showing impedance characteristics of a plurality of series LC filter circuits 41 _{1 to} 41 _n. As shown in FIG. 2, for example, the first series LC filter circuit 41 ₁ has a small impedance Z at a specific frequency f ₁ , and the second to nth series LC filter circuits 41 _{2 to} 41 n have specific frequencies f ₂ to _{41 n.} At f _n , the impedance Z is sufficiently large. Similarly, for the second series LC filter circuit 41 _2, small impedance Z at a specific frequency _{f 2,} the first and third to n series LC filter circuit _{41 1,} 41 3 to 41 specific frequencies of _n Impedance Z is sufficiently large in f ₁ , f _{3 to} f _n. The same applies to the _{third to} nth series LC filter circuits 41 3 to 41 _n.

FIG. 3 is a block diagram showing details of the control unit 30 shown in FIG. The control unit 30 shown in FIG. 3 includes a plurality of amplitude storage units 31 _{1 to} 31 _n , a plurality of unit frequency storage units 32 _{1 to} 32 _n , a plurality of multiplication units 33 _{1 to} 33 _n, and an addition unit 34. It includes a PWM signal generation unit 35.

Multiple amplitude storage unit ₃₁ 1 to 31 _n, the output circuits ₂₀ 1 to 20 _n of the command voltage _V ¹ * _~V ^{n *} a, the output circuits 20 ₁ detected by the voltage detecting unit ₂₂ 1 through 22 _n it is obtained by storing amplitude information for the difference between to 20 _n output voltage _V 1 ~V _n of. _{For example, if the output voltage V 1} detected with respect to the command voltage V ₁ ^* is large, the first amplitude storage unit 31 ₁ reduces the amplitude so that the output voltage V ₁ detected with respect to the command voltage V ₁ ^{* is large.} If it is small, it stores information that increases the amplitude. The same applies to the _{second to} nth amplitude storage units 31 2 to 31 _n. In FIG. 3, the plurality of amplitude storage units 31 _{1 to} 31 _n are conceptually illustrated so that the amplitudes are proportional to the difference, but this is merely a conceptual illustration. It is not limited to the contents shown in the figure.

The plurality of unit frequency storage units 32 _{1 to} 32 _n store unit sine waves (unit waveform signals) corresponding to specific frequencies of the series LC filter circuits 41 _{1 to} 41 _n. That is, for example, the first unit frequency storage unit 32 ₁ stores a sine wave having a frequency f _1. Similarly, the _{second to} nth unit frequency storage units 32 2 to 32 _n also store sine waves having _{frequencies f 2 to} f _{n, respectively.} The plurality of unit frequency storage units 32 _{1 to} 32 _n may store not only a sine wave corresponding to a specific frequency but also a rectangular wave or the like as long as it corresponds to a specific frequency.

The plurality of multiplication units 33 _{1 to} 33 _n multiply the amplitude output based on the information of the plurality of amplitude storage units 31 _{1 to} 31 _n by the unit sine wave of the plurality of unit frequency storage units 32 _{1 to} 32 _n. By doing so, a sine wave having a specific frequency whose amplitude is adjusted based on the above difference is generated. For example, the first multiplier unit 33 _1, the difference and the first amplitude memory 31 and the amplitude magnitude is adjusted based on the _first information, the first unit frequency unit sine wave of the storage unit 32 ₁ (frequency f ₁ ) And will be multiplied. The same applies to the _{second to} nth multiplication units 33 2 to 33 _n.

The addition unit 34 adds each signal generated by the _{plurality of multiplication units 33 1 to} 33 _n. The signal obtained by the addition unit 34 is a composite wave in which the signals generated by the _{plurality of multiplication units 33 1 to} 33 _{n are superposed.}

The PWM signal generation unit 35 inputs a signal from the addition unit 34 and, for example, compares it with a triangular wave to generate a control signal for switching a plurality of switching elements SW.

Next, the operation of the voltage conversion device 1 according to the present embodiment will be described. First, the control unit 30 has the above difference (arbitrary value is possible at the stage where the signal from the _{initial voltage detection units 22 1 to} 22 _n is not obtained) and the information of the _{plurality of amplitude storage units 31 1 to} 31 _n. The magnitude of the amplitude is determined based on. Next, the control unit 30 has a plurality of amplitudes _{determined based on the information of the plurality of amplitude storage units 31 1 to} 31 _n and a plurality of unit sine waves stored in the plurality of unit frequency storage units 32 _{1 to} 32 _n. Multiplication processing is performed by the multiplication units 33 _{1 to} 33 _{n of the above} , addition processing is performed by the addition unit 34, and the output is output to the PWM signal generation unit 35. The PWM signal generation unit 35 generates a control signal by a triangular wave comparison method or the like. The control unit 30 switches a plurality of switching elements SW based on the control signal generated in this way.

As a result, the primary side output voltage Vt1 corresponding to the switching control is applied to the primary side winding T1 of the isolation transformer T, and the secondary side circuit 20 is the secondary side corresponding to the primary side output voltage Vt1. The side output voltage Vt2 is supplied. Signal components corresponding to these frequency f ₁ is supplied to the first output circuit 20 ₁ is transmitted through the first filter circuit 40 _1. The signal component corresponding to the frequency f ₂ is supplied to the second output circuit 20 ₂ is transmitted through the second filter circuit 40 _2. The same applies to the other frequencies f _{3 to} f _n.

In this state, each of the plurality of voltage detection units 22 _{1 to} 22 _n detects the output voltages V _{1 to} V _n of the output circuits 20 _{1 to} 20 _n and feeds them back to the control unit 30.

As a result, the control unit 30 has _{the information of the plurality of amplitude storage units 31 1 to} 31 _n , the feedback output voltage V _{1 to} V _n, and the required output voltage to be output (that is, the command voltage V ₁ ^{* to} V _n ^*). ) And the difference, the amplitude is determined (adjusted). After that, the control unit 30 multiplies the _{unit sine wave by the multiplication units 33 1 to} 33 _n , and after the addition by the addition unit 34, the PWM signal generation unit 35 generates a control signal.

Thereafter, by repeating the above operation, becomes that the requested output voltage corresponding to the command voltage _V ^{1 *} _~V ⁿ * is supplied to the output circuits ₂₀ 1 to 20 _n, the output circuits ₂₀ 1 to 20 _n is The required output voltage will be output to the load.

In this way, according to the voltage converter 1 according to the present embodiment, a frequency signal corresponding to a specific frequency f _{1 to} f _{n is provided between the isolated transformer T and each of the plurality of output circuits 20 1 to} 20 _n. includes a filter circuit ₄₀ 1 to 40 _n for transmitting, the control unit 30, voltage detector ₂₂ 1-22 each of the output voltage is detected by the respective _{n V} 1 ~V _n and each command voltage _V ^{1 *} Based on the difference from ~ V _n ^* , the amplitude of the unit sine wave corresponding to each specific frequency f _{1 to} f _{n of each filter circuit 40 1} to 40 _n is adjusted, and the amplitude is adjusted for each. A control signal is generated based on a composite wave of a unit sine wave. Therefore, the amplitude of the unit sine wave corresponding to the specific frequencies f _{1 to} f _{n of the filter circuits 40 1} to 40 _n provided in front of the corresponding output circuits 20 _{1 to} 20 _n is adjusted, and the output circuit 20 is used. The magnitude of the voltage supplied to _{1 to} 20 _{n can be optimized.} Then, since the control signal is generated based on the composite wave of the unit sine wave whose amplitude is adjusted, the secondary side output voltage Vt2 corresponding to the composite wave is supplied to the secondary side circuit 20. Therefore, only a specific frequency component of the secondary output voltage Vt2 is supplied to the output circuits 20 _{1 to} 20 _{n through the corresponding filter circuits 40 1} to 40 _n. Therefore, it is possible to provide the voltage conversion device 1 which is not easily restricted by the load condition and can output the voltage more appropriately to the load.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and modifications may be made without departing from the spirit of the present invention. It may be combined.

For example, in the voltage conversion device 1 according to the present embodiment, the primary side circuit 10 is not particularly limited to the one shown in the figure as long as it is a circuit capable of changing the amplitude and frequency. Further, the filter circuits 40 ₁ to 40 _n are not particularly limited to the _{series LC filter circuits 41 1 to} 41 _n as long as the characteristics shown in FIG. 2 can be obtained.

Further, in FIG. 2, the resonance frequencies (specific frequencies) are assigned as _{f 1 to} f _{n in ascending order with respect to the first} output voltage 201 to the nth output circuit 20 _n. It's not a question. In addition, the rectifier circuits 21 _{1 to} 21 _n do not particularly ask the circuit configuration as long as they can perform full-wave rectification.

1: Voltage converter 10: Primary circuit 11: Inverter circuit 20: Secondary circuit 20 _{1 to} 20 _n : Output circuit 21 _{1 to} 21 _n : Rectifier circuit 22 _{1 to} 22 _n : Voltage detection unit 30: Control unit (Control signal generator)
31 _{1 to} 31 _n : Amplitude storage unit 32 _{1 to} 32 _n : Unit frequency storage unit 33 _{1 to} 33 _n : Multiplying unit 34: Adding unit 35: PWM signal generation unit 40 ₁ to 40 _n : Filter circuit 41 _{1 to} 41 _n : series LC filter circuit ₄₂ 1 through 42 _n: parallel LC filter circuit E: power SW: switching element T: isolation transformer (trans)
T1: Primary winding T2: Secondary winding V _{1 to} V _n : Output voltage V ₁ ^{* to} V _n ^* : Command voltage Vt1: Primary output voltage Vt2: Secondary output voltage

Claims (1)

A primary circuit that is connected to a power supply and controls the primary output voltage with a switching element.
A secondary circuit that includes multiple output circuits to output the required output voltage according to different command voltages,
A transformer that insulates between the primary side circuit and the secondary side circuit and supplies a voltage corresponding to the primary side output voltage to the secondary side circuit.
A plurality of voltage detectors for detecting the output voltage of each of the plurality of output circuits,
A control signal generation unit that generates a control signal for switching the switching element based on the difference between each output voltage detected by each of the plurality of voltage detection units and each command voltage is provided.
The secondary side circuit has a filter circuit for transmitting a frequency signal corresponding to a specific frequency between the transformer and each of the plurality of output circuits.
Each of the filter circuits differs from the other filter circuits in the specific frequency.
The control signal generation unit adjusts the amplitude of the unit waveform signal corresponding to the specific frequency of each of the filter circuits based on the difference, and the composite wave of each unit waveform signal whose amplitude is adjusted. A voltage converter characterized by generating a control signal based on.

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