Converter

Abstract

To provide a technology that makes it possible to acquire information on the peak value of a resonance current by a simple structure.SOLUTION: A converter of current resonance type may comprise: a first switching element; an inductance connected in series to the first switching element; a capacitor connected in series to the first switching element and the inductance; a current sensor for detecting a current flowing in the inductance and the capacitor; and an acquisition unit for acquiring information on the current detected by the current sensor. The acquisition unit may acquire information on the detection current of the current sensor at the timing when a prescribed time has elapsed after the first switching element was turned on.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a current resonance type converter.

Background Art

[0002] Patent Document 1 discloses an LLC converter. The LLC converter of Patent Document 1 includes a switching element, an inductance connected in series with the switching element, and a capacitor connected in series with the switching element and the inductance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an LLC converter, it may be necessary to detect a resonance current in order to control a switching element. The LLC converter of Patent Document 1 includes a current detection circuit for detecting a resonance current. However, simply detecting a resonance current may complicate the configuration of the current detection circuit. This specification provides a technology capable of acquiring information on the peak value of a resonance current with a simple configuration.

Means for Solving the Problems

[0005] In a first aspect of the present technology, a current resonance type converter may include a first switching element, an inductance connected in series with the first switching element, a capacitor connected in series with the first switching element and the inductance, a current sensor that detects a current flowing through the inductance and the capacitor, and an acquisition unit that acquires information on the current detected by the current sensor. The acquisition unit may acquire information on the detected current of the current sensor at a timing when a predetermined time has elapsed from the timing when the first switching element turns on.

[0006] According to this configuration, information on the resonance current in the current resonance type converter can be acquired at an appropriate timing. Thereby, information on the peak value of the resonance current can be acquired with a simple configuration.

[0007] In a second aspect, in the first aspect described above, the acquisition unit may acquire information on the detected current of the current sensor at a timing when a time Tx represented by the following formula has elapsed from the timing when the first switching element turns on.

[0008]

Equation

[0009] According to this configuration, information on the peak value of the resonance current can be acquired with a simple configuration.

[0010] In a third aspect, in the first or second aspect described above, the converter may include a plurality of the switching elements connected in series with the inductance and the capacitor. The acquisition unit may acquire information on the detected current of the current sensor at a timing when a predetermined time has elapsed from the timing when each switching element turns on.

[0011] According to this configuration, even when the first switching element is turned on or when the second switching element is turned on, information on the peak value of the resonance current can be obtained with a simple configuration.

[0012] In a fourth aspect, in any one of the first to third aspects, the converter may be a converter connected to the secondary battery.

[0013] According to this configuration, information on the peak value of the resonance current of the converter connected to the secondary battery can be obtained with a simple configuration.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0015] The LLC converter of the embodiment will be described with reference to the drawings. As shown in FIG. 1, the LLC converter 2 of the embodiment is connected to a power supply 4 and a load 6. The LLC converter 2 is a device that converts the input voltage input from the power supply 4 into an output voltage (for example, steps up or steps down) and applies it to the load 6. The LLC converter 2 is a current resonance type converter. The LLC converter 2 is mounted on, for example, an electric vehicle (for example, an electric car or a hybrid car). The LLC converter 2 of the embodiment is a half-bridge converter, but in a modified example, it may be a full-bridge converter. The type of the LLC converter 2 is not particularly limited.

[0016] The power supply 4 connected to the input side of the LLC converter 2 is, for example, a DC power supply such as a lithium-ion battery or a nickel-metal hydride battery. In a modified example, the power supply 4 may be configured to convert the voltage of an AC commercial power supply into a DC voltage and input it to the LLC converter 2. The load 6 connected to the output side of the LLC converter 2 is, for example, a resistance component in a motor. Note that the types of the power supply 4 and the load 6 are not particularly limited.

[0017] The LLC converter 2 includes a primary-side circuit 10, a secondary-side circuit 40, a transformer 50 configured between the primary-side circuit 10 and the secondary-side circuit 40, and a control unit 100. The LLC converter 2 in the embodiment is an isolated converter in which the primary-side circuit 10 and the secondary-side circuit 40 are isolated.

[0018] The primary-side circuit 10 of the LLC converter 2 is connected to the power supply 4. The primary-side circuit 10 includes a first switching element 12, a second switching element 14, a smoothing capacitor 52, a primary-side coil 16, an exciting inductance 18, a leakage inductance 22, and a resonance capacitor 24. The primary-side circuit 10 also includes a current sensor 60 that detects the current flowing through the leakage inductance 22 and the resonance capacitor 24.

[0019] The first switching element 12 and the second switching element 14 are, for example, transistors such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors). The LLC converter 2 converts the input voltage from the power supply 4 into an output voltage to the load 6 by alternately and periodically switching the on and off states of the first switching element 12 and the second switching element 14. The first switching element 12 is the switching element on the high-potential side of the LLC converter 2, and the second switching element 14 is the switching element on the low-potential side of the LLC converter 2.

[0020] In a modified example, the LLC converter 2 may include a diode connected in anti-parallel with the first switching element 12 and a capacitor connected in parallel with the first switching element 12. Further, the LLC converter 2 may include a diode connected in anti-parallel with the second switching element 14 and a capacitor connected in parallel with the second switching element 14.

[0021] The smoothing capacitor 52 of the primary circuit 10 is connected in parallel with the first switching element 12 and the second switching element 14. The primary coil 16 of the primary circuit 10 and the secondary coil 42 of the secondary circuit 40 together form a transformer 50. The LLC converter 2 transmits the power of the primary circuit 10 to the secondary circuit 40 via the transformer 50.

[0022] The exciting inductance 18 of the primary circuit 10 is connected in parallel with the primary coil 16. The leakage inductance 22 and the resonance capacitor 24 are connected in series with the primary coil 16. Further, the leakage inductance 22 and the resonance capacitor 24 are connected in series with the exciting inductance 18.

[0023] In the LLC converter 2, the power supply 4, the first switching element 12, the primary coil 16, the leakage inductance 22, and the resonance capacitor 24 are connected in series. Also, the second switching element 14, the primary coil 16, the leakage inductance 22, and the resonance capacitor 24 are connected in series. In the LLC converter 2, when the second switching element 14 turns off and the first switching element 12 turns on, the current due to the voltage of the power supply 4 flows through the leakage inductance 22 and the resonance capacitor 24. Also, when the first switching element 12 turns off and the second switching element 14 turns on, the current due to the charge stored in the resonance capacitor 24 flows through the leakage inductance 22 and the resonance capacitor 24. The current flowing through the leakage inductance 22 and the resonance capacitor 24 is sometimes called a resonance current. The LLC converter 2 is a so-called current resonance type converter.

[0024] In the LLC converter 2, the resonance frequency (f) determined by the inductance (Lr) of the leakage inductance 22 and the capacitance (Cr) of the resonance capacitor 24 is expressed by the following equation (1).

[0025] [Number]

[0026] Next, the secondary circuit 40 of the LLC converter 2 will be described. The secondary circuit 40 is connected to the load 6. The secondary circuit 40 includes a secondary coil 42, a plurality of rectifying diodes 44a - 44d, and a smoothing capacitor 54.

[0027] The secondary coil 42 of the secondary circuit 40 and the primary coil 16 together form a transformer 50. A current is generated in the secondary circuit 40 by the power transmitted to the secondary circuit 40 via the transformer 50. The plurality of rectifying diodes 44a - 44d rectify the current in the secondary circuit 40. In a modified example, a transistor may be used instead of a diode as the rectifying element for rectifying the current in the secondary circuit 40. The smoothing capacitor 54 of the secondary circuit 40 is connected in parallel with the load 6.

[0028] Next, the control unit 100 will be described. The control unit 100 includes, for example, a CPU, a ROM, and a RAM, etc., and executes predetermined control and processing related to the LLC converter 2 according to a predetermined program. For example, the control unit 100 switches the on and off states of the first switching element 12 and the second switching element 14. For example, the control unit 100 turns off the second switching element 14 and, at the same time, turns on the first switching element 12. Also, the control unit 100 turns off the first switching element 12 and, at the same time, turns on the second switching element 14. The control unit 100 does not turn on the second switching element 14 when the first switching element 12 is on. Also, the control unit 100 does not turn on the first switching element 12 when the second switching element 14 is on.

[0029] Next, the processes executed by the control unit 100 will be described. FIG. 2 is a flowchart of the processes executed by the control unit 100. The process in FIG. 2 starts, for example, when an operation start instruction for the LLC converter 2 is input to the control unit 100. In FIG. 2, the first switching element 12 is represented as SW1, and the second switching element 14 is represented as SW2.

[0030] In S2 of the process in FIG. 2, the control unit 100 sets a predetermined time Tx for detecting the resonance current of the LLC converter 2. The predetermined time Tx is set, for example, based on the following formula (2).

[0031] [Number]

[0032] In the subsequent S4, the control unit 100 starts the switching operation of the LLC converter 2. The control unit 100 alternately switches the on and off states of the first switching element 12 and the second switching element 14.

[0033] In the subsequent S6, the control unit 100 determines whether the first switching element 12 switches from off to on (i.e., turns on). If the first switching element 12 turns on (YES in S6), the process proceeds to S8. In S8, the control unit 100 starts timing. The control unit 100 measures the elapsed time T1 from the timing when the first switching element 12 turns on.

[0034] On the other hand, if the first switching element 12 does not turn on (NO in S6), the process proceeds to S12. In S12, the control unit 100 determines whether the second switching element 14 switches from off to on (i.e., turns on). If the second switching element 14 turns on (YES in S12), the process proceeds to S14. In S14, the control unit 100 starts timing. The control unit 100 measures the elapsed time T2 from the timing when the second switching element 14 turns on.

[0035] On the other hand, when the second switching element 14 does not turn on (NO in S12), the process proceeds to S22. In S22, the control unit 100 determines whether the first switching element 12 is in the on state. If the first switching element 12 has not turned off after turning on (see S6), the first switching element 12 is in the on state. When the first switching element 12 is in the on state (YES in S22), the process proceeds to S24. On the other hand, when the first switching element 12 is in the off state (NO in S22), the process proceeds to S32.

[0036] In S24 after YES in S22, it is determined whether the elapsed time T1 from the timing when the first switching element 12 turned on matches the time Tx set in S2 above. When the elapsed time T1 from the timing when the first switching element 12 turned on matches the set time Tx (YES in S24), the process proceeds to S26. On the other hand, when the elapsed time T1 does not match the set time Tx (NO in S24), the process waits.

[0037] In S26 after YES in S24, the control unit 100 acquires the information of the current detected by the current sensor 60. That is, the control unit 100 acquires the information of the detected current of the current sensor 60 at the timing when the set time Tx has elapsed from the timing when the first switching element 12 turned on. Thereby, the control unit 100 can acquire the information of the peak value of the resonance current in the LLC converter 2 when the first switching element 12 is turned on. The control unit 100 stores the acquired detected current information in, for example, a storage unit (ROM or RAM). In the subsequent S28, the control unit 100 resets the timing started in S8 above.

[0038] On the other hand, in S32 after NO in the above S22, the control unit 100 determines whether or not the second switching element 14 is in the on state. If the second switching element 14 has not turned off after turning on (see S12), the second switching element 14 is in the on state. If the second switching element 14 is in the on state (YES in S32), the process proceeds to S34. On the other hand, if the second switching element 14 is in the off state (NO in S32), the process proceeds to S42.

[0039] In S34 after YES in S32, it is determined whether or not the elapsed time T2 from the timing when the second switching element 14 turned on matches the time Tx set in S2 above. If the elapsed time T2 from the timing when the second switching element 14 turned on matches the set time Tx (YES in S34), the process proceeds to S36. On the other hand, if the elapsed time T2 does not match the set time Tx (NO in S34), the process waits.

[0040] In S36 after YES in S34, the control unit 100 acquires the information of the current detected by the current sensor 60. That is, the control unit 100 acquires the information of the detected current of the current sensor 60 at the timing when the set time Tx has elapsed from the timing when the second switching element 14 turned on. Thereby, the control unit 100 can acquire the information of the peak value of the resonance current in the LLC converter 2 when the second switching element 14 is turned on. The control unit 100 stores the acquired detected current information in, for example, a storage unit (ROM or RAM). In the subsequent S38, the control unit 100 resets the timing started in S14 above.

[0041] In S42 after S8, S14, S28, S32, or S38 above, the control unit 100 determines whether or not to end the switching operations of the first switching element 12 and the second switching element 14. If the control unit 100 ends the switching operations (YES in S42), the process of FIG. 2 ends, and if the switching operations are not ended (NO in S42), the process returns to S6 above and the process is repeated.

[0042] (Effect)

[0043] According to this configuration, information on the resonance current in the current resonance type converter can be acquired at an appropriate timing. Thereby, information on the peak value of the resonance current can be acquired with a simple configuration. Therefore, for example, the resonance capacitor 24, the smoothing capacitors 52 and 54 can be downsized, and the entire apparatus can be downsized. Also, the LLC converter 2 can be made to have a higher response speed.

[0044] The LLC converter 2 includes a second switching element 14 connected in series with the leakage inductor 22 and the resonance capacitor 24. The control unit 100 alternately switches on and off the first switching element 12 and the second switching element 14. The control unit 100 acquires information on the detected current of the current sensor 60 at a timing when a predetermined time Tx has elapsed from the timing when the second switching element 14 turns on. According to this configuration, even when the second switching element 14 turns on, information on the peak value of the resonance current can be acquired with a simple configuration.

[0045] (Modification) In the above-described embodiment, the secondary circuit 40 of the LLC converter 2 is configured to be connected to the load 6, but the configuration is not limited to this. In the modification, the secondary circuit 40 of the LLC converter 2 may be connected to a secondary battery (for example, a lithium ion battery, a nickel metal hydride battery, etc.).

[0046] The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in this specification or the drawings can achieve multiple purposes simultaneously, and achieving one of these purposes itself has technical utility.

Description of Reference Numerals

[0047] 2: LLC converter, 4: power supply, 6: load, 10: primary circuit, 12: first switching element, 14: second switching element, 16: primary coil, 18: exciting inductance, 22: inductance, 24: resonant capacitor, 40: secondary circuit, 42: secondary coil, 44a - 44d: rectifying diode, 50: transformer, 60: current sensor, 100: control unit

Claims

1. A current resonance type converter, comprising: a switching element; an inductance connected in series with the switching element; a capacitor connected in series with the switching element and the inductance; a current sensor for detecting a current flowing through the inductance and the capacitor; an acquisition unit for acquiring information on the current detected by the current sensor; wherein the acquisition unit acquires information on the detected current of the current sensor at a timing when a predetermined time has elapsed from the timing when the switching element turns on.

2. The converter according to Claim 1, wherein the acquisition unit acquires information on the detected current of the current sensor at a timing when a time Tx represented by the following formula has elapsed from the timing when the switching element turns on.

3. The converter according to Claim 1 or 2, comprising a plurality of the switching elements connected in series with the inductance and the capacitor; wherein the acquisition unit acquires information on the detected current of the current sensor at a timing when a predetermined time has elapsed from the timing when each switching element turns on.

4. The converter according to Claim 1 or 2, which is a converter connected to a secondary battery.

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