JP7352179B2 - Overcurrent protection devices, DC/DC converter devices, and power systems - Google Patents

Description

The present disclosure relates to an overcurrent protection device for a DC/DC converter device including multiple LLC resonant converters. The present disclosure also relates to a DC/DC converter device including such an overcurrent protection device. The present disclosure also relates to a power system including a DC/DC converter device equipped with such an overcurrent protection device.

When the current flowing through the DC/DC converter device increases in order to increase the power supplied from the DC/DC converter device to the load device, heat generation in the DC/DC converter device also increases. Therefore, in order to reduce heat generation in DC/DC converter devices, DC/DC converter devices with multiplexed components, for example a plurality of LLC resonant converters, are known. In this case, the plurality of LLC resonant converters operate in mutually different phases.

For example, Patent Document 1 discloses that a plurality of primary windings receive power from a corresponding half-bridge circuit, a plurality of secondary windings each magnetically coupled to each primary winding and connected to an output terminal, A switching multiphase resonant voltage converter is disclosed having a plurality of LLC resonant circuits respectively connected to each primary winding. The primary or secondary windings are connected such that the actual or virtual neutral point is floating.

European Patent Application Publication No. 2299580

Generally, in order to protect the circuit from overcurrent, a DC/DC converter device may include an overcurrent protection device that stops the operation of the switching elements of the inverter when an overcurrent occurs. In order to detect the occurrence of an overcurrent, an overcurrent protection device uses, for example, a current sensor to measure the current flowing through the primary circuit of a transformer, and then compares the measured current with a predetermined overcurrent threshold. compare.

As described above, when the DC/DC converter device includes a plurality of LLC resonant converters, the transformer, inductor, capacitor, etc. of each LLC resonant converter may have different variations from their design values. Due to these variations, the peak value (amplitude), effective value, waveform, etc. of the current of each phase become non-uniform. Therefore, if a common overcurrent threshold is set for each LLC resonant converter to protect each LLC resonant converter from overcurrent, the overcurrent threshold is the maximum amount of current allowed to flow through a given LLC resonant converter. It may be lower than the maximum value (for example, 160% of the rated current). In this case, there is a possibility that the operation of the DC/DC converter device may be stopped unnecessarily before the current flowing through the LLC resonant converter reaches the maximum allowable value. Therefore, there is a need for an overcurrent protection device that does not unnecessarily stop the operation of the DC/DC converter device before the current flowing through each LLC resonant converter reaches the maximum allowable value.

An object of the present disclosure is an overcurrent protection device for a DC/DC converter device including a plurality of LLC resonant converters, which An object of the present invention is to provide an overcurrent protection device that does not unnecessarily stop the operation of a converter device. Further, an object of the present disclosure is to provide a DC/DC converter device including such an overcurrent protection device. Further, an object of the present disclosure is to provide a power system including a DC/DC converter device equipped with such an overcurrent protection device.

An overcurrent protection device according to one aspect of the present disclosure includes:
An overcurrent protection device for a DC/DC converter device including a plurality of LLC resonant converters, the overcurrent protection device comprising:
Each of the plurality of LLC resonant converters includes at least one switching element, a transformer, and a capacitor, and the plurality of LLC resonant converters operate in different phases from each other,
The overcurrent protection device includes:
Measuring the current flowing in the primary circuit of the transformer of each LLC resonant converter using a plurality of current sensors,
setting an overcurrent threshold for each of the LLC resonant converters based on the measured current;
For any one of the plurality of LLC resonant converters, when the measured current exceeds the overcurrent threshold, a stop signal is output that stops the operation of the switching element of each LLC resonant converter.

As a result, even if non-uniform current flows through each LLC resonant converter, the operation of the DC/DC converter device is unnecessarily stopped before the current flowing through each LLC resonant converter reaches the maximum allowable value. It can be made difficult to do.

In an overcurrent protection device according to one aspect of the present disclosure,
setting a common reference current value for the plurality of LLC resonant converters;
calculating a current crest factor of each LLC resonant converter based on the measured current, respectively;
The product of the current crest factor of each of the LLC resonant converters and the reference current value is set as an overcurrent threshold of each of the LLC resonant converters.

Thereby, the overcurrent threshold value for each phase can be set based on the current crest factor of the current for each phase.

A DC/DC converter device according to one aspect of the present disclosure includes:
a plurality of LLC resonant converters each comprising at least one switching element, a transformer, and a capacitor and operating in mutually different phases;
a plurality of current sensors that respectively measure the current flowing in the primary side circuit of the transformer of each of the LLC resonant converters;
The overcurrent protection device according to claim 1 or 2 is provided.

As a result, even if non-uniform current flows through each LLC resonant converter, the operation of the DC/DC converter device is unnecessarily stopped before the current flowing through each LLC resonant converter reaches the maximum allowable value. It can be made difficult to do.

A power system according to one aspect of the present disclosure includes:
a power supply device that supplies a first DC voltage;
The DC/DC converter device according to claim 3, which converts the first DC voltage to a second DC voltage;
and a load device operated by the second DC voltage.

As a result, even if non-uniform current flows through each LLC resonant converter, the operation of the DC/DC converter device is unnecessarily stopped before the current flowing through each LLC resonant converter reaches the maximum allowable value. It can be made difficult to do.

The overcurrent protection device according to one aspect of the present disclosure provides a DC/ It is possible to make it difficult to stop the operation of the DC converter device unnecessarily.

FIG. 1 is a block diagram schematically showing a configuration example of a power system including a DC/DC converter device 5 according to an embodiment. 2 is a circuit diagram schematically showing a configuration example of the DC/DC converter device 5 of FIG. 1. FIG. 3 is a block diagram schematically showing a configuration example of an overcurrent protection device 15 in FIG. 2. FIG. 3 is a graph showing exemplary waveforms of U-phase current, V-phase current, and W-phase current detected by current sensors CS1 to CS3 of DC/DC converter device 5 of FIG. 2. FIG. It is a circuit diagram schematically showing a configuration example of a DC/DC converter device 5A according to a modification of the embodiment.

Hereinafter, an embodiment (hereinafter also referred to as "this embodiment") according to one aspect of the present disclosure will be described based on the drawings. Like numerals indicate like components in the drawings.

[Application example]
FIG. 1 is a block diagram schematically showing a configuration example of a power system including a DC/DC converter device 5 according to an embodiment. The power system in FIG. 1 includes, for example, an AC power supply device 1, a noise filter device 2, a rectifier 3, a power factor regulator 4, a DC/DC converter device 5, and a load device 6.

The noise filter device 2, the rectifier 3, and the power factor regulator 4 receive supply of AC power from the AC power supply device 1 and generate DC power having a first DC voltage. In this specification, the AC power supply device 1, the noise filter device 2, the rectifier 3, and the power factor regulator 4 are also referred to as a "power supply device" that supplies the first DC voltage. The DC/DC converter device 5 converts the first DC voltage into a second DC voltage. The load device 6 is operated by the second DC voltage.

FIG. 2 is a circuit diagram schematically showing a configuration example of the DC/DC converter device 5 of FIG. 1. The DC/DC converter device 5 includes at least a plurality of LLC resonant converters 11 to 13, a capacitor C0, a driving device 14, an overcurrent protection device 15, and a plurality of current sensors CS1 to CS3.

The LLC resonant converter 11 includes switching elements Q1 and Q2, a transformer T1, an inductor Lr1, a capacitor Cr1, and diodes D1 and D2. Switching elements Q1 and Q2 constitute an inverter that generates AC power from DC power. The transformer T1 has a primary winding w1 and secondary windings w2, w3, and also has a leakage inductance Lm1. Inductor Lr1, capacitor Cr1, and leakage inductance Lm1 constitute an LLC resonant circuit. Further, diodes D1 and D2 constitute a rectifier circuit.

The LLC resonant converter 12 includes switching elements Q3 and Q4, a transformer T2, an inductor Lr2, a capacitor Cr2, and diodes D3 and D4. Switching elements Q3 and Q4 constitute an inverter that generates AC power from DC power. The transformer T2 has a primary winding w4 and secondary windings w5, w6, and also has a leakage inductance Lm2. Inductor Lr2, capacitor Cr2, and leakage inductance Lm2 constitute an LLC resonant circuit. Further, diodes D3 and D4 constitute a rectifier circuit.

The LLC resonant converter 13 includes switching elements Q5, Q6, a transformer T3, an inductor Lr3, a capacitor Cr3, and diodes D5, D6. Switching elements Q5 and Q6 constitute an inverter that generates AC power from DC power. The transformer T3 has a primary winding w7 and secondary windings w8, w9, and also has a leakage inductance Lm3. Inductor Lr3, capacitor Cr3, and leakage inductance Lm3 constitute an LLC resonant circuit. Further, diodes D5 and D6 constitute a rectifier circuit.

Capacitor C0 smoothes the output power of LLC resonant converters 11-13.

The driving device 14 drives the switching elements Q1 to Q6 so as to operate the LLC resonant converters 11 to 13 in mutually different phases (for example, phases different by 120 degrees). The drive device 14 drives the switching elements Q1 to Q6 by, for example, pulse width modulation.

Current sensors CS1 to CS3 measure currents flowing through the primary circuits of transformers T1 to T3 of each LLC resonant converter 11 to 13, respectively.

Overcurrent protection device 15 uses a plurality of current sensors CS1 to CS3 to measure the currents flowing through the primary side circuits of transformers T1 to T3 of each LLC resonant converter 11 to 13, respectively. Overcurrent protection device 15 sets an overcurrent threshold for each LLC resonant converter 11 to 13 based on the measured current. Overcurrent protection device 15 protects switching elements Q1 to Q6 of each LLC resonant converter 11 to 13 when the measured current exceeds an overcurrent threshold for any one of the plurality of LLC resonant converters 11 to 13. Outputs a stop signal to stop the operation. Overcurrent protection device 15 sends a stop signal to drive device 14 .

Overcurrent protection device 15 can individually and dynamically set an overcurrent threshold for each of LLC resonant converters 11 to 13. As a result, even if non-uniform current flows through each LLC resonant converter 11-13, the overcurrent protection device 15 prevents the current flowing through each LLC resonant converter 11-13 from reaching the maximum allowable value. This makes it difficult to stop the operation of the DC/DC converter device 5 unnecessarily.

[Embodiment]
Hereinafter, a power system including a DC/DC converter device including an overcurrent protection device according to an embodiment will be further described.

[Configuration example]
Each component of the power system will be further explained with reference to FIG.

The AC power supply device 1 supplies AC power of a predetermined voltage and a predetermined frequency. The AC power supply device 1 may be a power supply equipment of a commercial power grid, and may instead include, for example, a DC power supply device and an inverter.

The noise filter device 2 is configured to reduce at least one of a normal mode noise signal and a common mode noise signal propagating through the conducting wire. The noise filter device 2 includes at least one of an active filter including an active element that generates an inverted signal having a polarity opposite to that of a noise signal, and a passive filter including passive elements such as a capacitor and an inductor.

The rectifier 3 converts AC power supplied from the AC power supply device 1 via the noise filter device 2 into DC power. The rectifier 3 may be a rectifier circuit including a diode bridge. Further, the rectifier 3 may be a synchronous rectifier circuit including a switching element that operates in accordance with the phase of the input alternating current voltage or alternating current.

The power factor regulator 4 adjusts the power factor of the DC power output from the rectifier 3. The power factor regulator 4 may include passive elements such as inductors and/or capacitors, and may further include active elements such as transistors and diodes.

The DC/DC converter device 5 converts the first DC voltage output from the power factor regulator 4 into a second DC voltage.

The load device 6 is operated by the DC power output from the DC/DC converter device 5 and performs some work. The load device 6 includes, for example, a motor, a storage battery, a sensor, a communication device, and the like.

Each component of the DC/DC converter device 5 will be further described with reference to FIG. 2.

In the example of FIG. 2, the pair of switching elements Q1 and Q2, the pair of switching elements Q3 and Q4, and the pair of switching elements Q5 and Q6 each constitute a half-bridge inverter.

In the example of FIG. 2, the first terminal of the primary winding w1 of the transformer T1 is connected to a node between switching elements Q1 and Q2 via an inductor Lr1. A first terminal of the primary winding w4 of the transformer T2 is connected to a node between switching elements Q3 and Q4 via an inductor Lr2. A first terminal of the primary winding w7 of the transformer T3 is connected to a node between switching elements Q5 and Q6 via an inductor Lr3. The second terminal of the primary winding w1 of the transformer T1, the second terminal of the primary winding w4 of the transformer T2, and the second terminal of the primary winding w7 of the transformer T3 are connected to a neutral voltage via capacitors Cr1 to Cr3. Connected to point N0. In the example of FIG. 2, the neutral point N0 is floating.

In the example of FIG. 2, both ends of the secondary windings w2, w3 of the transformer T1 are connected to the positive output terminal of the DC/DC converter device 5 via diodes D1, D2, respectively, and the secondary windings w2, w3 The center tap of is connected to the negative output terminal of the DC/DC converter device 5. Both ends of the secondary windings w5, w6 of the transformer T2 are connected to the positive output terminal of the DC/DC converter device 5 via diodes D3, D4, respectively, and the center taps of the secondary windings w5, w6 are connected to the DC / is connected to the negative output terminal of the DC converter device 5. Both ends of the secondary windings w8 and w9 of the transformer T3 are connected to the positive output terminal of the DC/DC converter device 5 via diodes D5 and D6, respectively, and the center taps of the secondary windings w8 and w9 are / is connected to the negative output terminal of the DC converter device 5.

As mentioned above, LLC resonant converters 11-13 operate in different phases from each other. For this reason, the drive device 14 uses a control signal to turn on the switching element Q1 and turn off the switching element Q2 in the first half of each cycle, and turn off the switching element Q1 and turn on the switching element Q2 in the second half of each cycle. is sent to switching elements Q1 and Q2. Further, the drive device 14 turns on the switching element Q3 and turns off the switching element Q4 in the first half of each cycle delayed by 120 degrees from the on/off operation of the switching elements Q1 and Q2, and turns on the switching element Q3 in the second half of each cycle. A control signal is sent to switching elements Q3 and Q4 to turn off switching element Q4 and turn on switching element Q4. Further, the drive device 14 turns on the switching element Q5 and turns off the switching element Q6 in the first half of each cycle delayed by 240 degrees from the on/off operation of the switching elements Q1 and Q2, and turns on the switching element Q5 in the second half of each cycle. A control signal is sent to switching elements Q5 and Q6 to turn off switching element Q6 and turn on switching element Q6. As a result, LLC resonant converters 11 to 13 generate U-phase, V-phase, and W-phase power, which have phases different from each other by 120 degrees.

The output voltage of each LLC resonant converter 11-13 depends on the switching frequency of switching elements Q1-Q6. Therefore, the drive device 14 changes the switching frequency of the switching elements Q1 to Q6 according to the desired output voltage of the DC/DC converter device 5.

In the example of FIG. 2, current sensor CS1 is provided to measure the U-phase current flowing between capacitor Cr1 and neutral point N0. Current sensor CS2 is provided to measure the V-phase current flowing between capacitor Cr2 and neutral point N0. Current sensor CS3 is provided to measure the W-phase current flowing between capacitor Cr3 and neutral point N0.

FIG. 3 is a block diagram schematically showing a configuration example of the overcurrent protection device 15 of FIG. 2. As shown in FIG. The overcurrent protection device 15 includes rectifiers 21-1 to 21-3, peak detectors 22-1 to 22-3, effective value calculators 23-1 to 23-3, and crest factor calculators 24-1 to 24-3. , threshold calculators 25-1 to 25-3, comparators 26-1 to 26-3, and an OR operator 27.

The rectifier 21-1, the peak detector 22-1, the effective value calculator 23-1, the crest factor calculator 24-1, the threshold calculator 25-1, and the comparator 26-1 are used in the LLC resonant converter 11. An overcurrent detection circuit 20-1 is configured to detect overcurrent.

The rectifier 21-1 rectifies the U-phase current measured by the current sensor CS1 and sends it to the peak detector 22-1, the effective value calculator 23-1, and the OR operator 27.

The peak detector 22-1 detects the current peak value of the U-phase current. The peak detector 22-1 includes, for example, a peak hold circuit.

The effective value calculator 23-1 calculates the current effective value of the U-phase current. Since calculating the effective value takes time, the effective value calculator 23-1 uses a low-pass filter to generate an average value of the rectified U-phase current instead of the effective value of the U-phase current. It's okay. Here, for example, an average value over one or more immediately preceding cycles may be generated, or an average value over the period from the time when the DC/DC converter device 5 is started up to the present time may be generated.

The crest factor calculator 24-1 calculates the current crest factor of the U-phase current=current peak value/current effective value based on the current peak value and current effective value of the U-phase current.

The threshold calculator 25-1 calculates the product of the current crest factor of the U-phase current and a preset reference current value as the overcurrent threshold ThU of the U-phase current, and A current threshold ThU is set in the comparator 26-1. A reference current value common to LLC resonant converters 11 to 13 is preset in threshold calculator 25-1. The reference current value indicates the effective value of the current when the peak value of the current is considered to reach a predetermined overcurrent threshold.

Further, an initial value of the crest factor common to the LLC resonant converters 11 to 13 is set in advance in the threshold calculator 25-1. As mentioned above, calculating the effective value takes time. Further, the overcurrent protection device 15 does not have effective value data at the time of starting its operation. Therefore, until the effective value calculator 23-1 can calculate the current effective value of the U-phase current, the threshold calculator 25-1 uses the current crest factor of the U-phase current instead of the current crest factor of the U-phase current. The initial value of the set crest factor is used. The initial value of the crest factor is set based on the design value of the waveform of the U-phase current. For example, the crest factor of a sine wave is √2, the crest factor of a triangular wave is √3, and the crest factor of a rectangular wave is 1.

Further, an upper limit Th1 and a lower limit Th2 of the overcurrent threshold, which are common to the LLC resonant converters 11 to 13, are preset in the threshold calculator 25-1.

The comparator 26-1 determines whether the instantaneous value of the rectified U-phase current exceeds the overcurrent threshold ThU of the U-phase current, and sends an output signal indicating the determination result to the OR operator 27. . For example, the output signal of the comparator 26-1 transitions from a low level to a high level when the instantaneous value of the rectified U-phase current exceeds the overcurrent threshold ThU of the U-phase current.

In this way, the overcurrent detection circuit 20-1 dynamically sets the overcurrent threshold ThU of the U-phase current based on the measured U-phase current, and also determines whether the measured U-phase current It is determined whether the threshold value ThU has been exceeded.

The rectifier 21-2, the peak detector 22-2, the effective value calculator 23-2, the crest factor calculator 24-2, the threshold calculator 25-2, and the comparator 26-2 are used in the LLC resonant converter 12. An overcurrent detection circuit 20-2 is configured to detect overcurrent. Like the overcurrent detection circuit 20-1, the overcurrent detection circuit 20-2 dynamically sets the overcurrent threshold of the V-phase current based on the measured V-phase current, and It is determined whether the V-phase current exceeds the overcurrent threshold ThV.

The rectifier 21-1, the peak detector 22-1, the effective value calculator 23-1, the crest factor calculator 24-1, the threshold calculator 25-1, and the comparator 26-1 are used in the LLC resonant converter 11. An overcurrent detection circuit 20-1 is configured to detect overcurrent. Like the overcurrent detection circuits 20-1 and 20-2, the overcurrent detection circuit 20-3 dynamically sets the overcurrent threshold of the W-phase current based on the measured W-phase current, and also , it is determined whether the measured W-phase current exceeds an overcurrent threshold ThW.

When at least one of the U-phase current, V-phase current, and W-phase current exceeds the corresponding overcurrent threshold, the OR operator 27 selects switching elements Q1 to Q6 of each LLC resonant converter 11 to 13. Outputs a stop signal to stop the operation.

The rectifiers 21-1 to 21-3, the peak detectors 22-1 to 22-3, and the effective value calculators 23-1 to 23-3 may be configured as analog circuits that operate in continuous time. Further, the crest factor calculators 24-1 to 24-3, the threshold calculators 25-1 to 25-3, the comparators 26-1 to 26-3, and the OR operator 27 operate in discrete time. It may also be configured as a digital circuit.

[Operation example]
FIG. 4 is a graph showing exemplary waveforms of the U-phase current, V-phase current, and W-phase current detected by the current sensors CS1 to CS3 of the DC/DC converter device 5 of FIG.

As described above, the transformers T1 to T3, inductors Lr1 to Lr3, capacitors Cr1 to Cr3, and the like of the plurality of LLC resonant converters 11 to 13 may have different variations from their design values. Due to these variations, the peak value, effective value, waveform, etc. of the current of each phase become non-uniform. FIG. 4 shows a case where the U-phase current, V-phase current, and W-phase current have mutually different peak values and waveforms.

For example, in a simulation conducted by the present inventors, even if an attempt was made to generate U-phase current, V-phase current, and W-phase current that have the same peak value and the same waveform, due to component variations, the following Currents with different peak values, rms values, and crest factors were generated.

――――――――――――――――――――――――――――――――――
Peak value Effective value Crest factor――――――――――――――――――――――――――――――――
U phase 7.63833 5.41779 1.409860847
V phase 9.28427 5.83791 1.590341406
W phase 7.53056 4.85251 1.551889641
――――――――――――――――――――――――――――――――――

Typically, when multiple circuits have the same circuit configuration and are composed of the same types of components, the circuits have the same characteristics. Therefore, when the DC/DC converter device 5 includes a plurality of LLC resonant converters 11 to 13, it is natural that a common overcurrent threshold value is set for each LLC resonant converter 11 to 13. However, due to variations in the components of each LLC resonant converter 11-13, the characteristics of each LLC resonant converter 11-13 are different from each other. Therefore, if a common overcurrent threshold is set for each LLC resonant converter 11 to 13, the overcurrent threshold will be the maximum value of current that is allowed to flow through a certain LLC resonant converter (for example, 160% of the rated current). %) may be lower. In this case, there is a risk that the DC/DC converter device 5 may be stopped unnecessarily before the current flowing through the LLC resonance converter reaches the maximum allowable value.

As described below, the overcurrent protection device 15 according to the embodiment allows the current flowing through each of the LLC resonant converters 11 to 13 to be allowed even when non-uniform current flows through each of the LLC resonant converters 11 to 13. It is possible to make it difficult to stop the operation of the DC/DC converter device 5 unnecessarily before reaching the maximum value.

(Step S1) As described above, the reference current value, the initial value of the crest factor, and the upper limit Th1 and lower limit Th2 of the overcurrent threshold are preset in the overcurrent protection device 15. For example, set the reference current value to 10A, set the initial value of the crest factor to √2, set the upper limit Th1 of the overcurrent threshold to 13A, and set the lower limit Th2 of the overcurrent threshold to 7A. May be set.

(Step S2) The overcurrent protection device 15 determines the current state of each of the U-phase current, V-phase current, and W-phase current in a certain cycle (nth cycle) of the U-phase current, V-phase current, and W-phase current. Detect the peak value of , calculate the current effective value, and calculate the current crest factor.

(Step S3) The overcurrent protection device 15 compares the current crest factor calculated in step S2 with the reference current value set in step S1 for each of the U-phase current, V-phase current, and W-phase current. The products are calculated and updated as overcurrent thresholds ThU, ThV, and ThW for the next period (n+1 period). If the calculated overcurrent thresholds ThU, ThV, and ThW exceed the upper limit Th1 set in step S1, the overcurrent threshold is set to the upper limit Th1. Furthermore, when the calculated overcurrent thresholds ThU, ThV, and ThW are smaller than the lower limit Th2 set in step S1, the overcurrent threshold is set to the lower limit Th2.

(Step S4) The overcurrent protection device 15 determines that in the next cycle (n+1 cycle), at least one of the U-phase current, V-phase current, and W-phase current corresponds to the corresponding overcurrent calculated in step S3. When thresholds ThU, ThV, and ThW are exceeded, a stop signal is output that stops the operation of switching elements Q1 to Q6 of each LLC resonant converter 11 to 13. Otherwise, the overcurrent protection device 15 returns to step S2 and repeats the process.

As shown in FIG. 4, overcurrent protection device 15 can individually and dynamically set overcurrent threshold values ThU, ThV, and ThW for each of LLC resonant converters 11 to 13. As a result, even if non-uniform current flows through each LLC resonant converter 11-13, the overcurrent protection device 15 prevents the current flowing through each LLC resonant converter 11-13 from reaching the maximum allowable value. This makes it difficult to stop the operation of the DC/DC converter device 5 unnecessarily.

[Modified example]
Although the embodiments of the present disclosure have been described in detail above, the above descriptions are merely illustrative of the present disclosure in all respects. It goes without saying that various improvements and modifications can be made without departing from the scope of the present disclosure. For example, the following changes are possible. In addition, below, the same code|symbol is used regarding the same component as the said embodiment, and description is abbreviate|omitted suitably about the same point as the said embodiment. The following modified examples can be combined as appropriate.

FIG. 5 is a circuit diagram schematically showing a configuration example of a DC/DC converter device 5A according to a modification of the embodiment. Instead, LLC resonant converters 11A to 13A are provided.

The LLC resonant converter 11A includes a transformer T11 and an inductor Lm11 in place of the transformer T1 and its leakage inductance Lm1 in FIG. 2, and diodes D11 to D14 in place of the diodes D1 and D2 in FIG. Further, the LLC resonant converter 12A includes a transformer T12 and an inductor Lm12 in place of the transformer T2 and its leakage inductance Lm2 in FIG. 2, and diodes D15 to D18 in place of the diodes D3 and D4 in FIG. Further, the LLC resonant converter 13A includes a transformer T13 and an inductor Lm13 in place of the transformer T3 and its leakage inductance Lm3 in FIG. 2, and diodes D19 to D22 in place of the diodes D5 and D6 in FIG.

The LLC resonant circuits of the LLC resonant converters 11A to 13A may each include inductors Lm11 to Lm13, which are discrete elements, instead of the leakage inductances Lm1 to Lm3 of the transformers T1 to T3.

Further, in the example of FIG. 5, the node corresponding to the neutral point N0 of FIG. 2 is connected to the negative electrode (or ground conductor) of the primary circuit of each transformer T11 to T13.

Further, the transformer T11 has a primary winding w1 and a secondary winding w11. The secondary winding w11 is connected to the output terminal of the DC/DC converter device 5 via a full bridge rectifier circuit including diodes D11 to D14. Further, the transformer T12 has a primary winding w4 and a secondary winding w12. The secondary winding w12 is connected to the output terminal of the DC/DC converter device 5 via a full bridge rectifier circuit including diodes D15 to D18. Further, the transformer T13 has a primary winding w7 and a secondary winding w13. The secondary winding w13 is connected to the output terminal of the DC/DC converter device 5 via a full bridge rectifier circuit including diodes D19 to D22.

Only part of the configuration shown in FIG. 5 may be applied to the DC/DC converter device 5 of FIG. 2. For example, LLC resonant converters 11 to 13 in FIG. 2 may each include inductors Lm11 to Lm13 in FIG. 5. Further, the neutral point N0 in FIG. 2 may be connected to the negative electrode (or ground conductor) of the primary circuit of each transformer T1 to T3. LLC resonant converters 11 to 13 in FIG. 2 may include transformers T11 to T13 and diodes D11 to D22 in FIG. 5 instead of transformers T1 to T3 and diodes D1 to D6. Thereby, the degree of freedom in designing the DC/DC converter device can be improved.

Each LLC resonant converter 11 to 13, 11A to 13A may include a full bridge inverter including four switching elements instead of a half bridge inverter including two switching elements, and may include at least one switching element. Other inverters may also be provided.

The DC/DC converter device 5 includes two or four or more LLC resonant converters, and may be configured to generate not only three-phase but two-phase or four-phase or more alternating current power.

The power system may include a DC power supply instead of the AC power supply 1 and the rectifier 3. Further, the power system may include an inverter and an AC load device instead of the DC load device 6. The overcurrent protection device according to the embodiment is also applicable to these cases.

[effect]
It is difficult to predict by analysis the unbalance of the peak value, effective value, waveform, etc. of the current of each phase that occurs due to variations in the components of each LLC resonant converter 11 to 13. On the other hand, the overcurrent protection device 15 according to the embodiment sets the overcurrent threshold based on the current crest factor to the LLC resonance It can be set individually and dynamically for each converter 11 to 13.

In this way, the overcurrent protection device 15 according to the embodiment allows the current flowing through each LLC resonant converter 11 to 13 to reach the maximum allowable current even when non-uniform current flows through each LLC resonant converter 11 to 13. It is possible to make it difficult to stop the operation of the DC/DC converter device 5 unnecessarily before the value is reached.

The DC/DC converter device 5 according to the embodiment includes the plurality of LLC resonance converters 11 to 13, so that the heat source can be distributed in the case of the DC/DC converter device 5. Therefore, for example, it is possible to provide a high power, high power density DC/DC converter device that does not have an air cooling fan.

[summary]
The overcurrent protection device, DC/DC converter device, and power system according to each aspect of the present disclosure may be expressed as follows.

An overcurrent protection device 15 according to one aspect of the present disclosure is an overcurrent protection device 15 for a DC/DC converter device 5 including a plurality of LLC resonant converters 11 to 13. each includes at least one switching element Q1-Q6, a transformer T1-T3, and a capacitor Cr1-Cr3. The plurality of LLC resonant converters 11 to 13 operate in mutually different phases. Overcurrent protection device 15 uses a plurality of current sensors CS1 to CS3 to measure the currents flowing through the primary side circuits of transformers T1 to T3 of each LLC resonant converter 11 to 13, respectively. Overcurrent protection device 15 sets an overcurrent threshold for each LLC resonant converter 11 to 13 based on the measured current. Overcurrent protection device 15 protects switching elements Q1 to Q6 of each LLC resonant converter 11 to 13 when the measured current exceeds an overcurrent threshold for any one of the plurality of LLC resonant converters 11 to 13. Outputs a stop signal to stop the operation.

An overcurrent protection device 15 according to one aspect of the present disclosure sets a common reference current value to a plurality of LLC resonant converters 11 to 13. Overcurrent protection device 15 calculates the current crest factor of each LLC resonant converter 11 to 13 based on the measured current. Overcurrent protection device 15 sets the product of the current crest factor and reference current value of each LLC resonant converter 11 to 13 as an overcurrent threshold value of each LLC resonant converter 11 to 13, respectively.

A DC/DC converter device 5 according to one aspect of the present disclosure includes a plurality of LLC resonant converters 11 that each include at least one switching element Q1 to Q6, a transformer T1 to T3, and a capacitor Cr1 to Cr3, and operate in mutually different phases. -13, a plurality of current sensors CS1-CS3 each measuring the current flowing through the primary side circuit of the transformers T1-T3 of each LLC resonant converter 11-13, and an overcurrent protection device 15 according to claim 1 or 2. Be prepared.

A power system according to one aspect of the present disclosure includes a power supply device that supplies a first DC voltage, and a DC/DC converter device 5 according to claim 3 that converts the first DC voltage into a second DC voltage. , and a load device 6 operated by a second DC voltage.

The overcurrent protection device according to one aspect of the present disclosure is applicable, for example, to a power system that operates as a power supply system that receives AC power and outputs DC power of approximately 2 kW.

The overcurrent protection device according to one aspect of the present disclosure can be applied, for example, to a power conversion device including a plurality of inverters in which current imbalance occurs for a reason different from that of the DC/DC converter device 5 according to the embodiment. be.

1 AC power supply device 2 Noise filter device 3 Rectifier 4 Power factor regulator 5,5A DC/DC converter device 6 Load devices 11 to 13, 11A to 13A LLC resonant converter 14 Drive device 15 Overcurrent protection device 20-1 to 20- 3 Overcurrent detection circuits 21-1 to 21-3 Rectifiers 22-1 to 22-3 Peak detectors 23-1 to 23-3 Effective value calculators 24-1 to 24-3 Crest factor calculators 25-1 to 25 -3 Threshold calculator 26-1 to 26-3 Comparator 27 OR operator C0, Cr1 to Cr3 Capacitor CS1 to CS3 Current sensor D1 to D6, D11 to D22 Diode Lm1 to Lm3 Leakage inductance Lr1 to Lr3, Lm11 ~Lm13 Inductor N0 Neutral point Q1~Q6 Switching element T1~T3, T11~T13 Transformer w1~w9, w11~w13 Winding

Claims (3)

An overcurrent protection device for a DC/DC converter device including a plurality of LLC resonant converters, the overcurrent protection device comprising:
Each of the plurality of LLC resonant converters includes at least one switching element, a transformer, and a capacitor, and the plurality of LLC resonant converters operate in different phases from each other,
The overcurrent protection device includes:
setting a common reference current value for the plurality of LLC resonant converters;
Measuring the current flowing in the primary circuit of the transformer of each LLC resonant converter using a plurality of current sensors,
calculating a current crest factor of each LLC resonant converter based on the measured current, respectively;
setting the product of the current crest factor of each of the LLC resonant converters and the reference current value as an overcurrent threshold of each of the LLC resonant converters;
For any of the plurality of LLC resonant converters, when the measured current exceeds the overcurrent threshold, outputting a stop signal that stops the operation of the switching element of each of the LLC resonant converters;
Overcurrent protection device. a plurality of LLC resonant converters each comprising at least one switching element, a transformer, and a capacitor and operating in mutually different phases;
a plurality of current sensors that respectively measure the current flowing in the primary side circuit of the transformer of each of the LLC resonant converters;
and the overcurrent protection device according to claim 1 .
DC/DC converter device. a power supply device that supplies a first DC voltage;
The DC/DC converter device according to claim 2 , which converts the first DC voltage to a second DC voltage;
and a load device operated by the second DC voltage.
power system.

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