JP7445462B2 - 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 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 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 outputs first and second required output voltages according to mutually different command voltages. a secondary side circuit including first and second output circuits for the purpose of the present invention, and insulating between the primary side circuit and the secondary side circuit, and supplying the primary side output voltage to the secondary side circuit. a transformer that detects output voltages of the first and second output circuits, first and second voltage detection units that detect output voltages of the first and second output circuits, and first and second voltage detection units that detect output currents of the first and second output circuits, respectively; Switching the switching element based on the difference between the first and second output voltages detected by each of the second current detection section and the first and second voltage detection sections and the respective command voltages. a control signal generating section that generates a control signal for the first output circuit, and the secondary side circuit includes a secondary side circuit having a characteristic that the impedance increases as the frequency decreases between the transformer and the first output circuit. and a second filter circuit between the transformer and the second output circuit, the second filter circuit having a characteristic that the impedance increases as the frequency increases, and the control signal generation section includes: The control signal is controlled based on the difference between the detected output voltage and the command voltage of the first and second output circuits, which has a larger required power determined from the detected output current and the respective command voltages. The duty ratio is determined, and the difference between the detected output voltage and the command voltage of the first and second output circuits, which has the smaller required power calculated from the detected output current and the respective command voltages, is determined. The frequency of the control signal is determined based on the frequency of the control signal.

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 first and second 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. 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, and generates a voltage pulse signal (rectangular wave) by switching the plurality of switching elements SW. It is something to control. 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 circuit 20 is connected to the secondary winding T2 of the isolation transformer T, and includes two output circuits 20 ₁ and 20 ₂ that output required output voltages according to different command voltages. has been done.

Each output circuit 20 ₁ , 20 ₂ is provided at a branch point branched in parallel from the secondary winding T 2 of the isolation transformer T, and each output circuit 20 ₁ , 20 2 has a rectifier circuit 21 1 , 21 ₂ and a voltage detection section 22 ₁ . , 22 ₂ and current detection units 23 ₁ , 23 ₂ . The first and second rectifier circuits 21 ₁ and 21 ₂ are so-called full-wave rectifier circuits, and are configured to include a switching element, an inductance, and a capacitor. Note that the circuit configurations of the first and second rectifier circuits 21 ₁ and 21 ₂ do not matter as long as they can perform full-wave rectification. The first and second voltage detection sections 22 ₁ and 22 ₂ detect the output voltages V ₁ and V ₂ of the respective output circuits 20 ₁ and 20 ₂ . The first and second voltage detection sections 22 ₁ and 22 ₂ are connected in parallel with the respective rectifier circuits 21 ₁ and 21 ₂ and respective loads (not shown). The first and second voltage detection sections 22 ₁ and 22 ₂ transmit signals corresponding to the output voltages V ₁ and V ₂ of the two output circuits 20 ₁ and 20 ₂ to the control section 30 . The first and second current detection sections 23 ₁ and 23 ₂ detect the output currents I ₁ and I ₂ of the respective output circuits 20 ₁ and 20 ₂ . The first and second current detection units 23 ₁ and 23 ₂ are arranged, for example, on the positive electrode side line of the output circuits 20 ₁ and 20 ₂ .

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 determines the required output voltage (i.e. command voltage V ₁ ^* , V ₂ ^* ) that each output circuit 20 ₁ , 20 ₂ should supply to the load and the required output voltage detected by each voltage detection unit 22 ₁ , 22 ₂ . A control signal for switching the plurality of switching elements SW is generated based on the difference between the output voltages V ₁ and V ₂ of the output circuits 20 ₁ and 20 ₂ . The information on the command voltages V ₁ ^* , V ₂ ^* is held in the control unit 30, for example, by being stored in the control unit 30 in advance.

Further, the secondary circuit 20 includes a filter circuit 40 1 that transmits a frequency signal corresponding to a specific frequency between the isolation transformer T (secondary winding T 2 ) and the two output circuits 20 ₁ , 20 _{2 .} , ₄₀₂ . Each filter circuit 40 ₁ , 40 ₂ includes a series LC filter circuit 41 ₁ , 41 ₂ and a parallel LC filter circuit 42 ₁ , 42 ₂ .

Each of the series LC filter circuits 41 ₁ and 41 ₂ has substantially symmetrical impedance characteristics with respect to frequency. Each parallel LC filter circuit 42 ₁ , 42 ₂ is a circuit for preventing interference with subsequent stage circuits (rectifier circuits 21 ₁ , 21 ₂ ).

FIG. 2 is a diagram showing impedance characteristics of the first and second series LC filter circuits 41 ₁ and 41 ₂ . As shown in FIG. 2, the first direct LC filter circuit ₄₁₁ has a characteristic that the impedance Z increases as the frequency f decreases below the first specific frequency fm1. On the other hand, the second direct LC filter circuit ₄₁₂ has a characteristic that the impedance Z increases as the frequency f increases below the second specific frequency fm2 (<fm1). Note that the first and second series LC filter circuits 41 ₁ and 41 ₂ have the same impedance Z at a frequency fi between the first specific frequency fm1 and the second specific frequency fm2.

FIG. 3 is a block diagram showing details of the control section 30 shown in FIG. 1. The control unit 30 shown in FIG. 3 includes two duty generation units 31 ₁ and 31 ₂ , two frequency generation units 32 ₁ and 32 ₂ , two power conversion units 33 ₁ and 33 ₂ , and a power comparison unit , a determination section 35, a switch signal generation section 36, and a drive circuit 37.

The two duty generation units 31 ₁ and 31 ₂ calculate the difference between the output voltages V ₁ and V ₂ detected by the two voltage detection units 22 ₁ and 22 ₂ and the respective command voltages V ₁ ^* and V ₂ ^* . Based on this, two duty ratio candidates D ₁ and D ₂ are generated.

Specifically, the first duty generation unit 31 ₁ calculates the difference between the output voltage V ₁ detected by the first voltage detection unit 22 ₁ and the command voltage V ₁ ^* on the first output circuit 20 ₁ side. Based on this, the first duty ratio candidate _D1 is generated. When the command voltage V ₁ ^* is larger than the detected output voltage _V 1 , the first duty generation unit 31 ₁ generates the first duty ratio candidate D ₁ to be larger, and the detected output When the command voltage V _{1 *} is smaller than ^the voltage V 1 , the first duty ratio candidate D ₁ is generated to be smaller.

Further, the second duty generation unit 31 ₂ generates a voltage based on the difference between the output voltage V ₂ detected by the second voltage detection unit 22 ₂ and the command voltage V ₂ ^* on the second output circuit 20 ₂ side. , which generates the second duty ratio candidate _D2 . When the command voltage V ₂ ^* is larger than the detected output voltage V ₂ , the second duty generation unit 31 ₂ generates a second duty ratio candidate D ₂ to be larger, and generates a larger second duty ratio candidate D 2 . When the command voltage V ₂ ^* is smaller than the voltage V ₂ , the second duty ratio candidate D ₂ is generated to be smaller.

The two frequency generators 32 ₁ and 32 ₂ calculate the difference between the output voltages V ₁ and V 2 detected by the two voltage detectors 22 ₁ and _{22 2} and the respective command voltages V ₁ ^* and V ₂ ^* . Based on this, two frequency candidates f ₁ and f ₂ are determined.

Specifically, the first frequency generation unit 32 ₁ calculates the difference between the output voltage V ₁ detected by the first voltage detection unit 22 ₁ and the command voltage V ₁ ^* on the first output circuit 20 ₁ side. Based on this, the first frequency candidate _f1 is determined. When the command voltage V ₁ ^* is larger than the detected output voltage V ₁ , the first frequency generation unit 32 ₁ generates the first frequency candidate f ₁ to be larger, and generates the detected output voltage When the command voltage V ₁ ^* is smaller than V ₁ , the first frequency candidate f ₁ is generated to be smaller.

Further, the second frequency generation section 32 ₂ generates a signal based on the difference between the output voltage V ₂ detected by the second voltage detection section 22 ₂ and the command voltage V ₂ ^* on the second output circuit 20 ₂ side. , to determine the second frequency candidate _f2 . When the command voltage V ₂ ^* is larger than the detected output voltage V ₂ , the second frequency generation unit 32 ₂ generates a second frequency candidate f ₂ to be smaller, and generates the detected output voltage When the command voltage V ₂ ^* is smaller than V ₂ , the second frequency candidate f ₂ is generated to be larger.

The two power conversion units 33 ₁ and 33 ₂ calculate the power based on the output currents I ₁ and I ₂ detected by the two current detection units 23 ₁ and 23 ₂ and the respective command voltages V ₁ ^* and V ₂ ^*. , which calculates the required power. Specifically, the first power conversion unit 33 ₁ multiplies the output current I ₁ detected by the first current detection unit 23 ₁ by the command voltage V ₁ ^* on the first output circuit 20 ₁ side. , the required power on the first output circuit ₂₀₁ side is determined. The second power conversion unit 33 ₂ multiplies the output current I ₂ detected by the second current detection unit 23 ₂ by the command voltage V ₂ ^* on the second output circuit 20 ₂ side to obtain the second power conversion unit 33 2 . This is to obtain the required power on the output circuit ₂₀₂ side.

The power comparison unit 34 compares the required power calculated by the two power conversion units 33 ₁ and 33 ₂ and determines which required power is larger and which is smaller. The power comparison unit 34 outputs the determined information to the determination unit 35.

The determination unit 35 selects one of the two duty ratio candidates D ₁ and D ₂ based on the required power determined by the power comparison unit 34 and determines the duty ratio D for controlling the inverter circuit 11. It is something. The determination unit 35 determines as the duty ratio D the duty ratio candidates D ₁ and D ₂ for the output circuits 20 ₁ and 20 ₂ whose required power is determined by the power comparison unit 34 . Therefore, the determination unit 35 determines the first duty ratio candidate D 1 as the duty ratio D when the first output circuit 20 ₁ has a large power requirement, and determines the first duty ratio candidate D ₁ as the duty ratio D when the first output circuit 20 ₁ has a high power requirement. In this case, the second duty ratio candidate _D2 is determined as the duty ratio D.

Further, the determination unit 35 selects one of the two frequency candidates f ₁ and f ₂ based on the required power determined by the power comparison unit 34 and determines the frequency f for controlling the inverter circuit 11. It is something. The determination unit 35 determines the frequency candidates f ₁ and f ₂ of the output circuits 20 ₁ and 20 ₂ whose required power is smaller as determined by the power comparison unit 34 as the frequency f. Therefore, the determination unit 35 determines the first frequency candidate f1 as the frequency f when the first output circuit ₂₀₁ has a small power requirement, and determines the first frequency candidate _f1 as the frequency f when the second output circuit ₂₀₂ has a low power requirement. The second frequency candidate _f2 is determined as the frequency f.

The switch signal generation section 36 generates a control signal for switching the inverter circuit 11 based on the duty ratio D and the frequency f determined by the determination section 35. The drive circuit 37 controls switching of the inverter circuit 11 based on the control signal generated by the switch signal generation section 36.

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

First, the first duty generation section 31 ₁ and the first frequency generation section 32 ₁ generate an output voltage V ₁ detected by the first voltage detection section 22 ₁ and a command voltage on the first output circuit 20 ₁ side. A first duty ratio candidate D ₁ and a first frequency candidate f ₁ are generated based on the difference from V ₁ ^* . In addition, the second duty generation unit 31 ₂ and the second frequency generation unit 32 ₂ generate the output voltage V ₂ detected by the second voltage detection unit 22 ₂ and the command voltage on the second output circuit 20 ₂ side. A second duty ratio candidate D ₂ and a second frequency candidate f ₂ are generated based on the difference from V ₂ ^* .

Further, the first and second power conversion units 33 ₁ and 33 ₂ convert the output current I ₁ detected by the first current detection unit 23 ₁ and the command voltages V ₁ ^* and V ₂ ^* stored in advance. From this, the required power for the first output circuit 20 ₁ side and the second output circuit 20 ₂ side is calculated.

Here, when the load resistance of the first output circuit 20 ₁ is small, the required current value on the first output circuit 20 ₁ side becomes large, and the required power also becomes large. On the other hand, when the load resistance of the second output circuit ₂₀₂ is large, the required current value on the second output circuit ₂₀₂ side becomes small, and the required power also becomes small. The power comparison unit 34 transmits such information on the requested power or information on the magnitude of the requested power to the determination unit 35.

After that, the determination unit 35 determines the duty ratio D and the frequency f based on the following two rules. That is, the determination unit 35 adopts the duty ratio candidates D ₁ and D _{2 of the output circuits 20 1 and 20 2 that have} larger required power among the first and second duty generation units 31 ₁ and 31 ₂ ( 1st rule). Further, the determination unit 35 adopts the frequency candidates f ₁ and f ₂ for the output circuits 20 ₁ and 20 ₂ that require smaller power among the first and second frequency generation units 32 ₁ and 32 ₂ (the Rule 2).

Here, in this example, the first duty ratio candidate _D1 is adopted as the duty ratio D because the required power on the first output circuit ₂₀₁ side is large. Furthermore, since the required power on the second output circuit ₂₀₂ side is small, the second frequency candidate _f2 is adopted as the frequency f.

Next, the signal generation unit 36 generates a control signal based on the duty ratio D and frequency f adopted by the determination unit 35, and the drive circuit 37 switches the switching element SW based on the generated control signal. do.

Here, in the secondary side circuit 20, power according to the duty ratio D can be obtained, but since the duty ratio D is determined according to the magnitude of the load resistance on the first output circuit ₂₀₁ side, the The power supplied to the first output circuit ₂₀₁ is insufficient by the amount of power supplied to the second output circuit ₂₀₂ . Therefore, in order to compensate for the shortage, the first duty ratio candidate _D1 generated by the first duty generation unit ₃₁₁ is increased, and the duty ratio D is also increased. As a result of the increased duty ratio D, the output voltage V ₂ of the second output circuit 20 ₂ exceeds the command voltage V ₂ ^* , and in order to suppress the output voltage V ₂ , the output voltage V 2 is generated by the second frequency generation unit 32 ₂ . The second frequency candidate _f2 is increased, and the frequency f is also increased. The power cut due to the increased frequency f is transmitted to the first output circuit ₂₀₁ . Further, regarding the first output circuit ₂₀₁ , the impedance Z becomes smaller due to the increased frequency f.

If the output voltage V ₁ of the first output circuit 20 ₁ is less than the command voltage V ₁ ^* 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 output voltage V ₁ of the first output circuit 20 ₁ exceeds the command voltage V ₁ ^* in a state where the frequency f is increased, the duty ratio D is decreased. When the duty ratio D is decreased, the frequency f and the impedance Z are also decreased on the second output circuit ₂₀₂ side in order to guarantee this. When the impedance Z on the second output circuit 20 ₂ side becomes smaller, the impedance Z on the first output circuit 20 ₁ side becomes larger. As a result, the output voltage _V1 supplied to the first output circuit ₂₀₁ becomes smaller.

Thereafter, by repeating the above operation, each output circuit 20 ₁ , 20 ₂ is supplied with the required output voltage according to the command voltage V ₁ ^* , V ₂ ^* , and each output circuit 20 ₁ , 20 ₂ is The required output voltage will be output to the load.

On the other hand, when the load resistance of the first output circuit ₂₀₁ is large, the required current value on the first output circuit ₂₀₁ side becomes small, and the required power also becomes small. On the other hand, when the load resistance of the second output circuit 20 is small, the required current value on the second output circuit ₂₀₂ side becomes large, and the required power also becomes large. The power comparison unit 34 transmits such information on the requested power or information on the magnitude of the requested power to the determination unit 35.

In this example, the second duty ratio candidate _D2 is adopted as the duty ratio D because the required power on the second output circuit ₂₀₂ side is large. Furthermore, since the required power on the first output circuit ₂₀₁ side is small, the first frequency candidate _f1 is adopted as the frequency f.

Next, the signal generation unit 36 generates a control signal based on the duty ratio D and frequency f adopted by the determination unit 35, and the drive circuit 37 switches the switching element SW based on the generated control signal. do.

In the secondary side circuit 20, power according to the duty ratio D is obtained, but since the duty ratio D is determined according to the magnitude of the load resistance on the _second output circuit 20, the second output The power supplied to the circuit ₂₀₂ is insufficient by the amount of power supplied to the first output circuit ₂₀₁ . Therefore, in order to compensate for the shortage, the second duty ratio candidate _D2 generated by the second duty generation section ₃₁₂ is increased, and the duty ratio D is also increased. As a result of the increased duty ratio D, the output voltage V ₁ of the first output circuit 20 ₁ exceeds the command voltage V ₁ ^* , and in order to suppress the output voltage V 1 , the output voltage V ₁ of the first output circuit 20 1 is generated by the first frequency generator 32 ₁ . The first frequency candidate _f1 is reduced, and the frequency f is also reduced. The power cut due to the decrease in frequency f is transmitted to the second output circuit ₂₀₂ . Furthermore, as for the second output circuit ₂₀₂ , the impedance Z becomes smaller because the frequency f becomes smaller.

If the output voltage V ₂ of the second output circuit 20 ₂ is less than the command voltage V ₂ ^* in a state where the frequency f is reduced, the duty ratio D is further increased. Then, the above operation will be repeated. On the other hand, when the output voltage V ₂ of the second output circuit 20 ₂ exceeds the command voltage V ₂ ^* in a state where the frequency f is increased, the duty ratio D is decreased. When the duty ratio D is decreased, the frequency f increases and the impedance Z decreases on the first output circuit ₂₀₁ side to ensure this. When the impedance Z on the second output circuit 20 ₂ side becomes smaller, the impedance Z on the first output circuit 20 ₁ side becomes larger. As a result, the output voltage _V2 supplied to the second output circuit ₂₀₂ becomes smaller. After that, the above steps are repeated until a required output voltage that satisfies the command voltages V ₁ ^* , V ₂ ^* is obtained.

In this way, according to the voltage conversion device 1 according to the present embodiment, based on the difference between the command voltages V ₁ ^* , V ₂ ^* with larger required power and the detected output voltages V ₁ , V ₂ Determine the duty ratio D of the control signal, and determine the frequency f of the control signal based on the difference between the command voltages V ₁ ^* , V ₂ ^* with smaller required power and the detected output voltages V ₁ , V ₂ . Therefore, the duty ratio D is determined based on the larger required power, and it is possible to supply the required output voltage according to the larger command voltage V ₁ ^* , V ₂ ^* . In addition, since the frequency f of the control signal is determined based on the smaller required power, the frequency f is determined so that the impedance Z becomes larger, and the required output according to the smaller command voltage V ₁ ^* , V ₂ ^* Can supply voltage. In particular, the first filter circuit 40 ₁ has a characteristic that the impedance Z increases as the frequency f decreases, and the second filter circuit 40 ₂ has a characteristic that the impedance Z increases as the frequency f increases. Therefore, even if the duty ratio D and frequency f are determined as described above based on the magnitude of the required power depending on the load condition, it is prevented that the required output voltage cannot be achieved. 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 and 40 ₂ are not particularly limited to the series LC filter circuits 41 ₁ and 41 ₂ as long as they can obtain the characteristics shown in FIG.

Furthermore, in the embodiment described above, the control configuration is not limited to that shown in FIG. 3 as long as the control signal is generated based on the rules 1 and 2 described above. In addition, the circuit configuration of the rectifier circuits 21 ₁ and 21 ₂ is not particularly limited as long as full-wave rectification is possible.

1 : Voltage converter 10 : Primary side circuit 11 : Inverter circuit 20 : Secondary side circuit 20 ₁ , 20 ₂ : Output circuit 21 ₁ , 21 ₂ : Rectifier circuit 22 ₁ , 22 ₂ : Voltage detection section 23 ₁ , 23 ₂ : Current detection section 30: Control section (control signal generation section)
31 ₁ , 31 ₂ : Duty generation unit 32 ₁ , 32 ₂ : Frequency generation unit 33 ₁ , 33 ₂ : Power conversion unit 34 : Power comparison unit 35 : Judgment unit 36 : Signal generation unit 37 : Drive circuit 40 ₁ , 40 ₂ : Filter circuit 41 ₁ , 41 ₂ : Series LC filter circuit 42 ₁ , 42 ₂ : Parallel LC filter circuit E : Power supply I ₁ , I ₂ : Output current SW : Switching element T : Isolation transformer (transformer)
T1: Primary winding T2: Secondary winding V ₁ , V ₂ : Output voltage V ₁ ^* , V ₂ ^* : 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 first and second output circuits for outputting first and second required output voltages according to mutually different command voltages;
a transformer that insulates between the primary side circuit and the secondary side circuit and supplies the primary side output voltage to the secondary side circuit;
first and second voltage detection units that detect output voltages of the first and second output circuits, respectively;
first and second current detection units that detect output currents of the first and second output circuits, respectively;
Control for generating a control signal for switching the switching element based on the difference between the first and second output voltages detected by each of the first and second voltage detection units and each command voltage. A signal generation section;
The secondary side circuit includes, between the transformer and the first output circuit, a first filter circuit having a characteristic that impedance increases as the frequency decreases; and the transformer and the second output circuit. a second filter circuit having a characteristic that the impedance increases as the frequency increases;
The control signal generation unit generates a difference between the detected output voltage and a command voltage of the first and second output circuits, which has a larger required power determined from the detected output current and the respective command voltages. The duty ratio of the control signal is determined based on the command voltage of the first and second output circuits, which has the smaller required power calculated from the detected output current and the respective command voltages, and the detected command voltage. A voltage conversion device characterized in that the frequency of the control signal is determined based on the difference between the output voltage and the output voltage.

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