JP7445463B2 - voltage converter - Google Patents

Description

The present invention relates to a voltage converter.

Conventionally, an isolated DC/DC converter (voltage converter) that outputs two different voltages 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 converter 100 includes a primary circuit 110, a secondary circuit 120, and an isolation transformer IT. The primary side circuit 110 is connected to a power source and includes an inverter circuit 111 having 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 frequency f. A voltage determined by the input voltage V and the duty ratio D is applied to the primary winding IT1 of the isolation transformer IT at a frequency f.

The secondary 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 includes a switching element, an inductance, a capacitor, and the like. Similarly 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 includes switching elements, inductance, and It is configured with a capacitor etc.

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 depending on the frequency of the voltage, and the parallel LC filter circuit 123b is a circuit that prevents interference with the subsequent stage circuit (second output circuit 122).

FIG. 5 is a diagram showing the impedance characteristics of the series LC filter circuit 123a shown in FIG. 4. As shown in FIG. 5, the series LC filter circuit 123a has a characteristic in which impedance Z increases as the frequency increases in a region above a predetermined frequency f'.

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 during switching of the inverter circuit 111 is determined according to the resistance of the first load Lo1. Here, since the resistance of the first load Lo1 is small, the required current value becomes large, and the duty ratio D also becomes large. Further, the frequency f at the time of switching of the inverter circuit 111 is determined according to 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 is small and the impedance Z is large. Then, the plurality of switching elements S1 to S4 are switched so that the determined duty ratio D and frequency f are achieved.

In the secondary circuit 120, power according to the duty ratio D is obtained, but since the duty ratio D is determined according to the resistance of the first load Lo1, the power is not supplied to the first output circuit 121. The amount of power supplied to the second output circuit 122 is insufficient. Therefore, in order to compensate 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 increased 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 power cut due to the increased 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 will be 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 decreased. When the duty ratio D is reduced, the frequency f is reduced and the impedance Z is also reduced in order to guarantee this. As the impedance Z becomes smaller, the actual voltage Vd supplied to the first output circuit 121 becomes smaller. After that, the above steps are repeated until the command voltages Vd ^* , Vf ^* are achieved.

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

However, when the resistance of the first load Lo1 is large and the resistance of the second load Lo2 is small, the voltage conversion device described in Non-Patent Document 1 cannot satisfy the following requirements. 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. Furthermore, since the resistance of the second load Lo2 is small, the frequency f is determined so that the required current value is large and the impedance Z is small. After that, even if it is operated at the frequency f where the impedance Z is minimum, the duty ratio D is determined according to the large resistance of the first load Lo1, so the duty ratio D is the command voltage Vf ^* from the second load Lo2 side. It does not increase until the command voltage Vf* is satisfied, and the command voltage Vf ^* cannot be satisfied.

The present invention has been made to solve such conventional problems, and its purpose is to provide a voltage converter that can more appropriately output voltage to a load. .

The voltage conversion device according to the present invention includes a primary side circuit that is connected to a power source and controls a primary side output voltage using a switching element, and a plurality of output circuits that output required output voltages according to different command voltages. a transformer that insulates between the primary circuit and the secondary circuit and supplies the secondary circuit with a voltage according to the primary output voltage; a plurality of voltage detection sections that detect the output voltage of each of the output circuits; and switching the switching element based on the difference between each output voltage detected by each of the plurality of voltage detection sections and each required output voltage. a control signal generation unit that generates a control signal for the purpose of the output circuit, and the secondary side circuit includes a filter that transmits a frequency signal corresponding to a specific frequency between the transformer and each of the plurality of output circuits. circuit, each of the filter circuits is different from the other filter circuits in the specific frequency, and the control signal generation section is configured to generate a signal at the specific frequency of the filter circuit for each of the plurality of output circuits. A switch signal having a duty ratio based on the difference is generated, and a control signal is generated by time-divisionally switching the switch signals of each of the plurality of output circuits.

According to the present invention, it is possible to provide a voltage conversion device that can more appropriately output voltage to a load.

FIG. 1 is a circuit configuration diagram of a voltage converter according to the present embodiment. FIG. 3 is a diagram showing impedance characteristics of a plurality of series LC filter circuits. FIG. 2 is a block diagram showing details of the control section shown in FIG. 1. FIG. FIG. 2 is a circuit configuration diagram showing a voltage conversion device according to a comparative example. 5 is a diagram showing impedance characteristics of the series LC filter circuit shown in FIG. 4. FIG.

Hereinafter, the present invention will be explained along with preferred embodiments. Note that the present invention is not limited to the embodiments shown below, and can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments described below, illustrations and explanations of some components are omitted, but the details of the omitted techniques will be described within the scope of not contradicting the content described below. It goes without saying that publicly known or well-known techniques are applied as appropriate.

FIG. 1 is a circuit configuration diagram of a voltage converter according to this embodiment. The voltage conversion device 1 according to the present embodiment is mounted on a vehicle, for example, and is a device that uses one power source E to output a plurality of required output voltages according to different command voltages, and is a device that outputs a plurality of required output voltages according to different command voltages. This 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 section (control signal generation section) 30. Note that the primary side circuit 10 and the secondary side circuit 20 are insulated by an insulation transformer T.

The primary circuit 10 has an input side connected to a DC power source E, an output side connected to a primary winding T1 of an isolation transformer T, and includes an inverter circuit 11. 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 that can be repeatedly charged and discharged, and outputs a DC voltage to the output side (insulation transformer T side). The output side of the power supply E is connected to the inverter circuit 11 and applies a DC voltage 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 side output voltage Vt1 applied to the isolation transformer T. be. The inverter circuit 11 has an input side connected to a power source E, and an output side connected to a primary winding T1 of an isolation transformer T.

In addition, although the inverter circuit 11 is illustrated with two switching elements SW in FIG. 1, it is not limited to two, and may include one or three or more. Further, the inverter circuit 11 may have any configuration as long as it can control the primary side output voltage Vt1 by switching the switching element SW. In particular, the configuration of the inverter circuit 11 does not matter as long as it is a circuit (such as a full-bridge converter or a half-bridge converter) that can generate, for example, three-level rectangular waves.

The isolation transformer T provides insulation between the primary circuit 10 and the secondary circuit 20, and includes a primary winding T1 and a secondary winding T2. This isolation transformer T supplies a secondary output voltage Vt2 corresponding to the primary output voltage Vt1 of the primary circuit 10 to the secondary 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 winding T2 of the isolation transformer T, and has a plurality of (n (n is a natural number of 2 or more)) outputting required output voltages according to different command voltages. It is configured to include output circuits 20 ₁ to 20 _n .

Each output circuit 20 ₁ to 20 _n is provided at a plurality of parallel branches branched from the secondary winding T2 of the isolation transformer T, and each output circuit 20 ₁ to 20 n is connected to a rectifier circuit 21 1 to 21 _n and a voltage detection section. 22 ₁ to 22 _n . Each of the rectifier circuits 21 ₁ to 21 _n is a so-called full-wave rectifier circuit, and includes a switching element, an inductance, and a capacitor. Note that the circuit configuration of the rectifier circuits 21 ₁ to 21 _n does not matter as long as it can perform full-wave rectification. Each voltage detection unit 22 ₁ to 22 _n detects the output voltage V ₁ to V _n of each output circuit 20 ₁ to 20 _n . Each voltage detection section 22 ₁ - 22 _n is connected in parallel with a respective rectifier circuit 21 ₁ - 21 _n and a respective load (not shown). The plurality of voltage detection sections 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 section 30.

The control unit 30 controls the primary side output voltage Vt1 by controlling switching of a plurality of switching elements SW that constitute the inverter circuit 11. This control unit 30 controls 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 the output voltage detected by each voltage detection unit 22 ₁ to 22 _n . Control signals for switching the plurality of switching elements SW are generated based on the difference between the output voltages V ₁ to V _n of the output circuits 20 ₁ to 20 _n . Information about the command voltages V ₁ ^* to V _n ^* is held in the control unit 30, for example, by being stored in the control unit 30 in advance.

The secondary circuit 20 also includes a filter circuit 40 1 that transmits a frequency signal corresponding to a specific frequency between the isolation transformer T (secondary winding T2) and the plurality of output circuits 20 ₁ to 20 _{n .} ~ _40n . Each filter circuit 40 ₁ to 40 _n includes a series LC filter circuit 41 ₁ to 41 _n and a parallel LC filter circuit 42 ₁ to 42 _n .

Each of the series LC filter circuits 41 ₁ to 41 _n has impedance Z sufficiently reduced at a specific frequency (resonant frequency). In particular, each series LC filter circuit 41 ₁ to 41 _n has a sufficiently large impedance Z 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 a specific frequency different from other series LC filter circuits 41 ₁ to 41 _n , and each series LC filter circuit 41 1 to 41 n has a specific frequency different from other series LC filter circuits 41 ₁ to 41 _n . This means that the frequency signals transmitted by the LC filter circuits 41 ₁ to 41 _n are substantially not transmitted. Each of the parallel LC filter circuits 42 ₁ to 42 _n is a circuit for preventing interference with subsequent stage circuits (rectifier circuits 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 a small impedance Z at a specific frequency f ₂ to At _fn , impedance Z is made sufficiently large. Similarly, for the second series LC filter circuit 41 ₂ , the impedance _Z is small at the specific frequency f ₂ , and the impedance Z is small at the specific frequency f ₂ , _and Impedance Z is made sufficiently large at f ₁ , f ₃ to f _n . The same applies to the third to n-th series LC filter circuits 41 ₃ to 41 _n .

FIG. 3 is a block diagram showing details of the control section 30 shown in FIG. 1. The control section 30 shown in FIG. 3 includes a duty generation section 31, a synchronization switching section 32, a signal generation section 33, and a drive circuit 34.

The duty generation unit 31 inputs a signal (feedback signal) corresponding to the output voltages V ₁ to V _n detected by the plurality of voltage detection units 22 ₁ to 22 _n , and generates a signal (feedback signal) corresponding to the command voltage V ₁ ^* to V _n ^*. Duty ratios D ₁ to D _n are determined based on the differences.

Specifically, the duty generation unit 31 compares the command voltage V ₁ ^* corresponding to the first output circuit 20 ₁ with the output voltage V ₁ detected by the first voltage detection unit 22 ₁ , and generates the command. If the voltage V ₁ ^* is larger, the first duty ratio D 1 for the first output circuit 20 ₁ is increased, and if the command voltage V ₁ ^* is smaller, the first duty ratio D ₁ for the first output circuit 20 ₁ is increased. Decrease the first duty ratio _D1 .

Similarly, the duty generation unit 31 compares the command voltage V ₂ ^* according to the second output circuit 20 ₂ and the output voltage V ₂ detected by the second voltage detection unit 22 ₂ , and calculates the command voltage V ₂ ^*. If the command voltage V 2 * is larger, the second duty ratio D 2 for the second output circuit 20 ₂ is increased, and if the command voltage V ₂ ^* is smaller, the second duty ratio D ₂ for the second output circuit 20 ₂ is increased. Decrease the ratio _D2 . The same applies to the third to nth duty ratios D ₃ to D _n .

The duty generation section 31 transmits information on the duty ratios D ₁ to D _n determined in this manner to the synchronization switching section 32 .

The synchronization switching unit 32 generates frequencies f 1 to f _n corresponding to specific frequencies f _{1 to} f _n of each series LC filter circuit 41 ₁ to 41 _n , according to a time division rule determined by an arbitrary method. It is.

In addition, the synchronization switching unit 32 generates duty ratios D ₁ to D _n determined by the duty generation unit 31, that is, duty ratios D ₁ to D _n corresponding to the first to nth output circuits 20 ₁ to 20 _n , Synchronization is performed with specific frequencies f ₁ to f _n of each series LC filter circuit 41 ₁ to 41 _n , that is, specific frequencies f ₁ to f _n corresponding to the first to nth output circuits 20 ₁ to 20 _n . It is something. Specifically, the synchronization switching unit 32 synchronizes the first duty ratio _D1 and the first specific frequency _f1 , and synchronizes the second duty ratio _D2 and the second specific frequency _f2 . . The same applies to the third to nth duty ratios D ₃ to D _n and the third to nth specific frequencies f ₃ to f _n .

Furthermore, the synchronization switching unit 32 outputs the combinations of the synchronized duty ratios D ₁ to D _n and the specific frequencies f ₁ to f _n to the signal generation unit 33 in a time-division manner. Therefore, for example, the synchronization switching unit 32 outputs the first combination of the first duty ratio D ₁ and the first specific frequency f ₁ to the signal generation unit 33, and then outputs the first combination of the first duty ratio D 1 and the first specific frequency f 1 to the signal generation unit 33, and then outputs the first combination of the first duty ratio D 1 and the first specific frequency f ₁ to the signal generation unit 33. The second combination with the second specific frequency _f2 is output to the signal generation section 33. Thereafter, the synchronization switching section 32 sequentially outputs the third to nth combinations to the signal generation section 33 in the same manner.

The signal generating section 33 generates a control signal for controlling the inverter circuit 11 based on the information of the first to nth combinations from the synchronous switching section 32. At this time, the signal generation section 33 generates a plurality of switch signals corresponding to each of the plurality of output circuits 20 ₁ to 20 _n . That is, the signal generation unit 33 generates a first switch signal having a first duty ratio D _{1 at a first specific frequency f 1 based} on the first combination information from the synchronous switching unit 32. . This first switch signal is intended for the first output circuit ₂₀₁ .

Further, the signal generation unit 33 generates a second switch signal having a second duty ratio D _{2 at a second specific frequency f 2 based} on the second combination information from the synchronization switching unit 32 . . This second switch signal is for the second output circuit ₂₀₂ . Similarly, the signal control unit 33 sets the third to nth duty ratios at the third to nth specific frequencies f ₃ to f _n based on the information of the third to nth combinations from the synchronization switching unit 32. Third to nth switch signals D ₃ to D _n are generated. These third to nth switch signals are intended for the third to nth output circuits 20 ₃ to 20 _n .

Furthermore, the signal generation unit 33 generates a control signal for switching each switch signal in a time-division manner. To give an example, the signal generation unit 33 first sends a first switch signal directed to the first output circuit ₂₀₁ for a predetermined period of time, then continues a second switch signal directed to the second output circuit ₂₀₂ for a predetermined period of time. After that, the third to nth switch signals for the third to nth output circuits 20 ₃ to 20 _n are generated to generate control signals that continue for a predetermined period of time. Note that the first to nth switch signals do not have to be the first control signals, and the order can be arbitrary. Furthermore, the durations of the first to nth switch signals may also be unequal within the predetermined time period. The signal generation section 33 outputs such a control signal to the drive circuit 34.

The drive circuit 34 controls switching of the inverter circuit 11 based on the control signal generated by the signal generation section 33.

Next, the operation of the voltage converter 1 according to this embodiment will be explained.

First, the duty generation unit 31 of the control unit 30 generates the first to second voltages based on the difference (any value is possible at the stage where the initial signals from the voltage detection units 22 ₁ to 22 _n are not obtained). The first to n-th duty ratios D ₁ to D _n corresponding to the n output circuits 20 ₁ to 20 _n are determined. Next, the synchronization switching unit 32 generates the first to n-th specific frequencies f ₁ to f _n and also generates the first to n-th duty ratios D ₁ to D _n and the first to n-th specific frequencies. The first to nth combinations are generated by synchronizing f ₁ to f _n .

The signal generation unit 33 generated the first to nth switch signals based on the information of the first to nth combinations from the synchronization switching unit 32, and switched the first to nth switch signals in a time-sharing manner. Generate control signals. The drive circuit 34 switches the plurality of switching elements SW based on the control signal generated in this way.

As a result, the primary output voltage Vt1 according to the switching control is applied to the primary winding T1 of the isolation transformer T, and the secondary output voltage Vt1 corresponding to the primary output voltage Vt1 is applied to the secondary circuit 20. A side output voltage Vt2 is supplied. Among these, the signal component corresponding to the first duty ratio D ₁ corresponding to the first specific frequency f ₁ passes through the first filter circuit 40 ₁ and is supplied to the first output circuit 20 ₁ . Further, the signal component corresponding to the second duty ratio _D2 corresponding to the second specific frequency _f2 is transmitted through the second filter circuit ₄₀₂ and supplied to the second output circuit ₂₀₂ . The same applies to other specific frequencies f ₃ to f _n , and signal components corresponding to the third to nth duty ratios D ₃ to D _n are transmitted through the third to nth filter circuits 40 ₃ to 40 _n . and is supplied to the third to nth output circuits 20 ₃ to 20 _n .

In this state, the plurality of voltage detection units 22 ₁ to 22 _n each detect the output voltages V ₁ to V _n of the respective output circuits 20 ₁ to 20 _n , and feed them back to the control unit 30.

Thereby, the duty generation unit 31 of the control unit 30 generates the first to nth duty ratios D based on the difference between the detected output voltages V ₁ to V _n and the command voltages V ₁ ^* to V _n ^* . ₁ - Adjust D _n .

Thereafter, by repeating the above operation, each output circuit 20 ₁ to 20 _n is supplied with a required output voltage according to the command voltage V ₁ ^* to V _n ^* , and each output circuit 20 ₁ to 20 _n is The required output voltage will be output to the load.

In this way, according to the voltage conversion device 1 according to the present embodiment, frequency signals corresponding to specific frequencies f ₁ to f _n are provided between the isolation transformer T and each of the plurality of output circuits 20 ₁ to 20 _n . The control unit 30 detects each of the plurality of output circuits _{20 1 to} 20 _n at specific frequencies f ₁ to _{f n of} the filter circuits 40 ₁ to 40 _n , respectively. It generates switch signals having duty ratios D ₁ to D _n based on the differences between the output voltages V ₁ to V _n and the command voltages V ₁ ^* to V _n ^* , respectively, and outputs the plurality of output circuits 20 ₁ to 20 A control signal is generated by switching each of the _n switch signals in a time-division manner. Therefore, switch signals with duty ratios D ₁ to _{D n set} for each specific frequency f ₁ to f _n of the filter circuits 40 ₁ to 40 _n provided before the output circuits 20 ₁ to 20 n are obtained, By performing switching using a control signal obtained by switching the switch signal in a time-division manner, appropriate voltages are supplied to each of the output circuits 20 ₁ to 20 _n in a time-division manner. Therefore, it is possible to provide the voltage converter 1 that can more appropriately output voltage to the load.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and changes may be made without departing from the spirit of the present invention, and well-known and publicly known techniques may be used. May be combined.

For example, in the voltage converter 1 according to the present embodiment, 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 they can obtain the characteristics shown in FIG. .

Furthermore, in FIG. 2, the resonance frequencies (specific frequencies) are assigned from f ₁ to f _n in descending order from the first output circuit 20 ₁ to the n-th output circuit 20 _n , but the order is particularly It's not something to ask. In addition, the circuit configuration of the rectifier circuits 21 ₁ to 21 _n is not particularly limited as long as full-wave rectification is possible.

Furthermore, in the above embodiment, the control configuration is limited to that shown in FIG. 3 as long as it is configured to generate a control signal in which switch signals corresponding to each of the plurality of output circuits 20 ₁ to 20 _n are switched in a time-sharing manner. do not have.

1: Voltage converter 10: Primary side circuit 11: Inverter circuit 20: Secondary side circuit 20 ₁ to 20 _n : Output circuit 21 ₁ to 21 _n : Rectifier circuit 22 ₁ to 22 _n : Voltage detection section 30: Control section (Control signal generation section)
31: Duty generation section 32: Synchronization switching section 33: Signal generation section 34: Drive circuit 40 ₁ to 40 _n : Filter circuit 41 ₁ to 41 _n : Series LC filter circuit 42 ₁ to 42 _n : Parallel LC filter circuit E: Power supply SW: Switching element T: Isolation transformer (transformer)
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 side circuit connected to a power supply and controlling a primary side output voltage by a switching element;
a secondary side circuit including a plurality of output circuits for outputting required output voltages according to different command voltages;
a transformer that insulates between the primary side circuit and the secondary side circuit and supplies a voltage according to the primary side output voltage to the secondary side circuit;
a plurality of voltage detection units that detect output voltages of each of the plurality of output circuits;
A control signal generation section that generates a control signal for switching the switching element based on a difference between each output voltage detected by each of the plurality of voltage detection sections and each required output voltage. ,
The secondary side circuit has a filter circuit between the transformer and each of the plurality of output circuits that transmits a frequency signal corresponding to a specific frequency,
Each of the filter circuits is different from the other filter circuits in the specific frequency,
The control signal generation section generates, for each of the plurality of output circuits, a switch signal having a duty ratio based on the difference at the specific frequency of the filter circuit, and also generates a switch signal for each of the plurality of output circuits over time. A voltage conversion device characterized by generating control signals switched by division.

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