Current detection circuit, power conversion device and power system

Abstract

To provide a current detection circuit that can minutely adjust characteristics when detecting both the directions of a bidirectional current flowing in a current transformer.SOLUTION: The present invention relates to a current detection circuit for detecting the value of a switching current by a detection resistance with a current transformer. The current detection circuit detects the value of the switching current by switching the detection resistance and a reset resistance according to the direction in which the switching current flowing on a primary side of the current transformer flows.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a current detection circuit, a power conversion device, and a power system. [Background technology]

[0002] In a switching power supply, when detecting a pulsed DC current, a current transformer is used to detect the current. For example, when a current flows through the current transformer in a predetermined direction (for example, the forward direction), the diode becomes conductive and the current can be detected by the detection resistor.

[0003] However, in converters that require bidirectional operation or precharge operation, the direction of current flowing through the current transformer differs between forward and reverse operation. When current flows in the positive direction during forward operation, the current can be detected by the detection resistor, but when current flows in the negative direction during reverse operation, the diode does not conduct and the current cannot be detected by the detection resistor.

[0004] For example, a configuration that detects both the current during forward operation and the current during reverse operation could be configured to have a current transformer for forward operation and one for reverse operation, but this would require two current transformers, which could cause problems with the increased number of parts and circuit size.

[0005] Here, the rectifier circuit described in Patent Document 1 is designed to be able to detect the direct current flowing in pulses on the primary side of the current transformer in either direction (see Patent Document 1). The rectifier circuit is a full-bridge type rectifier circuit connected to the secondary side of the current transformer, and selects a current path that follows the flow of the secondary current. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-325340 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the rectifier circuit described in Patent Document 1, it is sometimes difficult to finely adjust the characteristics when detecting the currents in each of the two directions flowing through the current transformer.

[0008] The present disclosure has been made in consideration of the above circumstances, and has an objective of providing a current detection circuit, a power conversion device, and a power system that are capable of finely adjusting the characteristics when detecting currents in each of the two directions flowing through a current transformer. [Means for solving the problem]

[0009] One aspect of the present disclosure is a current detection circuit that uses a current transformer to detect a value of a switching current by a detection resistor, and detects the value of the switching current by switching between the detection resistor and the reset resistor depending on the direction of the switching current flowing through the primary side of the current transformer. a first diode, a second diode, a first reset resistor, a first detection resistor, a second detection resistor, a first switch element, and a positive voltage level shift circuit, wherein a series connection circuit of the first diode and the first detection resistor is connected in parallel to a secondary winding of the current transformer, a series connection circuit of the second diode and the first reset resistor is connected in parallel to the secondary winding of the current transformer, a series connection circuit of the first switch element and the second detection resistor is connected in parallel to the first reset resistor, the first diode is connected in a direction to be conductive when the switching current flows in a predetermined direction, and the second diode is connected in a direction to prevent conduction when the switching current flows in the predetermined direction, and the positive voltage level shift circuit converts a negative voltage detected using the parallel connection of the second detection resistor and the first reset resistor to a positive voltage level. This is a current detection circuit. One aspect of the present disclosure is a current detection circuit that uses a current transformer to detect a value of a switching current with a detection resistor, and detects the value of the switching current by switching between the detection resistor and a reset resistor depending on a direction of flow of the switching current flowing through a primary side of the current transformer, the current detection circuit having a first diode, a second diode, a first reset resistor, a second reset resistor, a first detection resistor, a second detection resistor, a first switch element, a second switch element, and a positive voltage level shift circuit, wherein a series connection circuit of the first diode and the second reset resistor is connected in parallel to a secondary winding of the current transformer, and a series-connected circuit with a detection resistor connected in parallel to the second reset resistor, a series-connected circuit of the second diode and the first reset resistor connected in parallel to a secondary winding of the current transformer, a series-connected circuit of the first switch element and the second detection resistor connected in parallel to the first reset resistor, the first diode is connected in a direction such that it is conductive when the switching current flows in a predetermined direction, and the second diode is connected in a direction such that it is non-conductive when the switching current flows in the predetermined direction, and the positive voltage level shift circuit converts a voltage detected using the second detection resistor to a positive voltage level.

[0010] One aspect of the present disclosure is a power conversion device having a current detection circuit.

[0011] One aspect of the present disclosure is a power system including a power conversion device. Effect of the Invention

[0012] According to the current detection circuit, power conversion device, and power system disclosed herein, it is possible to finely adjust the characteristics when detecting currents in each of the two directions flowing through a current transformer. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing a configuration of a power system according to a first embodiment. [Diagram 2] 3 is a diagram showing a configuration of a current detection unit according to the first embodiment. FIG. [Diagram 3] 4 is a diagram showing a configuration of a positive voltage level shift circuit of the current detection unit according to the first embodiment. FIG. [Figure 4] FIG. 11 is a diagram showing a configuration of a power system according to a second embodiment. [Diagram 5] FIG. 11 is a diagram showing a configuration of a current detection unit according to a second embodiment. [Figure 6] 13(A) to 13(G) are diagrams showing operational waveforms of various parts according to the second embodiment. [Figure 7] 10(H) to 10(L) are diagrams showing operational waveforms of each unit according to the second embodiment. [Figure 8] FIG. 11 is a diagram showing a configuration of a control circuit according to a second embodiment. [Figure 9] FIG. 13 is a diagram illustrating a configuration of a current detection unit according to a third embodiment. [Figure 10] 11A to 11C are diagrams showing operational waveforms of various parts according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0015] (First embodiment) [Power System] FIG. 1 is a diagram showing a configuration of a power system 1 according to the first embodiment. The power system 1 includes a DC power source 11 (power source V HV ), a DC-DC converter 2 which is an example of a power conversion device, and a resistor 27 which is a load (resistance R L ) and a DC power supply 28 (power supply V LV ) and an external microcomputer 111.

[0016] In this embodiment, a power system 1 mounted on a vehicle will be described as an example, and an on-vehicle DC-DC converter 2 that performs bidirectional operation will be described as an example, but the present invention is not limited to this. In this embodiment, the power supply V HV is the high-side battery voltage, and the power supply V LV is the auxiliary battery voltage, and the resistance R L is the vehicle load.

[0017] [DC-DC converter] The DC-DC converter 2 includes four FETs 12 to 15 (switching elements), each of which is a MOS (Metal Oxide Semiconductor)-FET (Field Effect Transistor), a transformer 16 (transformer Tr), and a capacitor 17 (capacitor C HV ), four FETs 21 to 24 (switching elements) each being a MOS-FET, and a choke coil 25 (choke coil L ch ) and capacitor 26 (capacitor C LV ), a current detection unit 31 consisting of a current detection circuit, an HV voltage detection unit 32, an LV voltage detection unit 33, and a control circuit 41.

[0018] The transformer 16 has a primary winding 61 (primary winding N P1 ) and secondary winding 62 (secondary winding N S1 ) and a core 63. The current detection unit 31 includes a current transformer 81 (current transformer CT) and a current-voltage conversion unit . The current transformer 81 has a primary winding 91 (primary winding N CT1 ) and secondary winding 92 (secondary winding N CT2 ) and a core 93.

[0019] The ground terminal 51 and the ground terminal 53 represent terminals having a reference potential. In this embodiment, the reference potential is the ground (GND). In this embodiment, the ground terminal 51 and the ground terminal 53 may be common.

[0020] The full bridge circuit consisting of four FETs 12 to 15 outputs a DC voltage V HV The primary transformer voltage is generated from Transformer 16 converts the primary transformer voltage V generated by the full bridge circuit into HV The secondary transformer voltage V LV The signal is converted to the original signal using a turns ratio and transmitted. V LV =n s1 / n p1 ×V HV Here, the turn ratio is the ratio of the number of turns of the primary winding 61 to the secondary winding 62, n p1 :n s1 It is.

[0021] The four FETs 21 to 24 rectify the AC voltage on the secondary side to generate a DC voltage. The choke coil 25 and the capacitor 26 smooth the rectified DC voltage.

[0022] Here, the connection terminals of the resistor 27 and the DC power supply 28 on the opposite side to the choke coil 25 are connected to a ground terminal 51 . In addition, the sources of the two FETs 22 and 24 and the connection end of the capacitor 26 opposite to the choke coil 25 are connected to the ground terminal 51. Note that this arrangement is just one example, and as another configuration example, the choke coil 25 may be arranged on the side of the ground terminal 51, that is, on the side of the sources of the FETs 22 and 24.

[0023] During forward operation (in this embodiment, an operation of transmitting power from the primary side to the secondary side), four operation modes exist depending on the states of the four FETs 12-15. Mode 1-1 is a mode in which FET 12 and FET 15 are on and FET 13 and FET 14 are off. At this time, power is transmitted from the primary side to the secondary side of transformer 16, power is supplied to the output, and energy is stored in choke coil 25. Mode 1-2 is a mode in which FET 12 and FET 14 are on and FET 13 and FET 15 are off. At this time, a reflux occurs on the primary side of the transformer 16 and energy is released from the choke coil 25 to the output. Mode 1-3 is a mode in which FET 13 and FET 14 are on and FET 12 and FET 15 are off. At this time, power is transmitted from the primary side to the secondary side of transformer 16, power is supplied to the output, and energy is stored in choke coil 25. Modes 1-4 are modes in which FET 13 and FET 15 are on and FET 12 and FET 14 are off. At this time, a reflux occurs on the primary side of transformer 16 and energy is released from choke coil 25 to the output.

[0024] After the operations from mode 1-1 to mode 1-4 are completed, the mode returns to mode 1-1 again, and the operations from mode 1-1 to mode 1-4 are repeated. In each mode, of the current flowing through choke coil 25, an AC component flows through capacitor .

[0025] In this embodiment, the control circuit 41 controls the on / off of each of the four FETs 12 to 15 to adjust the on-duty width of the semiconductor switching elements, and as a result, the duty ratio of the power transmission time is adjusted to achieve the desired output voltage. In this embodiment, the control circuit 41 controls the on / off of each of the four FETs 21 to 24.

[0026] During reverse operation (in this embodiment, the operation of transmitting power from the secondary side to the primary side), there are four operation modes depending on the states of the four FETs 21 to 24. Mode 2-1 is a mode in which all of the FETs 21 to 24 are in an on state. At this time, energy is stored in the choke coil 25 on the secondary side of the transformer 16. Mode 2-2 is a mode in which FET 22 and FET 23 are on and FET 21 and FET 24 are off. At this time, the transformer 16 transmits power together with the energy stored in the choke coil 25 from the secondary side to the primary side. In mode 2-3, all of the FETs 21 to 24 are in the on state. At this time, energy is stored in the choke coil 25 on the secondary side of the transformer 16. Mode 2-4 is a mode in which FET 21 and FET 24 are on and FET 22 and FET 23 are off. At this time, the transformer 16 transmits power together with the energy stored in the choke coil 25 from the secondary side to the primary side. After the operations from mode 2-1 to mode 2-4 are completed, the operation returns to mode 2-1 again, and the operations from mode 2-1 to mode 2-4 are repeated.

[0027] The current detection unit 31 detects the primary side input current I CT1 Detect. In the current detection unit 31, a current transformer 81 detects a primary input current I CT1 The detected current I CT2 is converted to the winding ratio. I CT2 =n CT1 / n CT2 ×I CT1 Here, the turn ratio is the ratio of the number of turns of the primary winding 91 to the secondary winding 92, n CT1 :n CT2 be. Generally, in the current transformer 81, the number of turns of the primary winding 91 is n CT1 is smaller, and the number of turns of the secondary winding 92, n CT2 As a specific example, the number of turns of the primary winding 91, n CT1 is 1, and the number of turns of the secondary winding 92, n CT2 is 100, but is not limited to this. One end of the secondary winding 92 is connected to the ground terminal 53 .

[0028] In the current detection unit 31, the current-voltage conversion unit 82 converts the detected current I CT2 is readable by the control circuit 41. CS (In this embodiment, the detection voltage V CS1 or the detection voltage V during reverse operation CS2 ) to

[0029] The HV voltage detector 32 has an insulating element inside and detects the DC voltage V HV The voltage V that can be read by the control circuit 41 HV_sense Convert to. The LV voltage detection unit 33 detects the DC voltage V LV The voltage V that can be read by the control circuit 41 LV_sense Convert to.

[0030] The control circuit 41 is, for example, a microcomputer or a DSP (Digital Signal Processor). The control circuit 41 converts the detected voltage V obtained by the current-voltage conversion unit 82 of the current detection unit 31 into CS and the voltage V obtained by the HV voltage detection unit 32. HV_sense and the voltage V obtained by the LV voltage detection unit 33. LV_sense and controls the operation of each part based on the values ​​of these voltages.

[0031] For example, the control circuit 41 outputs a switch change-over signal SW1 for controlling the reset section of the current transformer 81 to the current-voltage conversion section . Furthermore, the control circuit 41 outputs signals for controlling the on / off of each of the FETs 12 to 15 to the gates of the FETs 12 to 15 via drivers (not shown) provided for each drive system. Furthermore, the control circuit 41 outputs signals for controlling the on / off of each of the FETs 21 to 24 to the gates of the respective FETs 21 to 24 via drivers (not shown) provided for each drive system. In reality, drivers for driving the FETs 12-15, 21-24 would be required between the control circuit 41 and these FETs. However, for the sake of simplicity, the following description will be given assuming that the respective FETs 12-15, 21-24 can be driven directly by signal outputs from the control circuit 41.

[0032] The control circuit 41 is controlled by an external microcomputer 111 . In this embodiment, the external microcomputer 111 is a microcomputer of an ECU (Electronic Control Unit) provided on the vehicle side. Based on the state of the vehicle, the external microcomputer 111 outputs a selection signal SEL to the control circuit 41. The selection signal SEL is a signal that selectively instructs the DC-DC converter 2 to operate in the forward direction or the reverse direction. The external microcomputer 111 is, for example, a DC power supply 11 (power supply V HV ) and the state of DC power supply 28 (power supply V LV ) to output a selection signal SEL. In this embodiment, in forward operation, the current I HV is a positive current, and in reverse operation, the current I HV becomes a negative current.

[0033] During forward operation, the DC-DC converter 2 receives the DC voltage V HV The power is supplied to the DC power supply 28, thereby charging the DC power supply 28. On the other hand, during reverse operation, the DC-DC converter 2 is supplied with a DC voltage V LV By supplying the power to the DC power supply 11, the DC power supply 28 discharges.

[0034] [Current detection section] FIG. 2 is a diagram showing a configuration of the current detection unit 31 according to the first embodiment. In the current detection unit 31, the current-voltage conversion unit 82 includes a first detection resistor 231 (first detection resistor R CS1), a diode 232 (diode D1), and a first reset resistor 211 (first reset resistor R rst1 ) and the second detection resistor 212 (second detection resistor R cs2 ), a first switch element 213, a diode 214 (diode D2), and a positive voltage level shift circuit 251.

[0035] The diode 232 and the first detection resistor 231 are connected in series. This series connection circuit is connected in parallel with the secondary winding 92 of the current transformer 81. The low potential side of the voltage across the first detection resistor 231 is connected to the ground terminal 53, and the positive voltage generated on the high potential side is the first detection voltage V CS1 The signal is connected to the control circuit 41 so as to be input to the control circuit 41 as a signal. The diode 232 is connected in a direction such that it is conductive when the switching current flows in a predetermined direction (in this embodiment, the forward direction).

[0036] The diode 214 and the first reset resistor 211 are connected in series. This series connection circuit is connected in parallel with the secondary winding 92 of the current transformer 81. The diode 214 is connected in a direction that blocks conduction when the switching current flows in a predetermined direction. In other words, the diode 214 is connected in a direction that conducts when the switching current flows in a direction opposite to the predetermined direction (in this embodiment, the negative direction).

[0037] The first switch element 213 and the second detection resistor 212 are connected in series. This series connection circuit is connected in parallel with the first reset resistor 211. A positive voltage level shift circuit 251 is connected to a point between the first switch element 213 and the second detection resistor 212 . The positive voltage level shift circuit 251 outputs the second detection voltage V CS2 The control circuit 41 is connected to the input terminal 42 so as to input the following signal:

[0038] An example of the operation of the current detection unit 31 will be described. The current to be detected on the secondary side of the current transformer 81 is I CT2 When a current flows in the positive direction, the first switch element 213 is turned off (non-conductive) by the control circuit 41. As a result, the first detection resistor 231 is used as a detection resistor, and the first reset resistor 211 is used as a reset resistor. At this time, the waveform detected by the first detection resistor 231 is the first detection voltage V CS1 to the control circuit 41.

[0039] On the other hand, the detected current I CT2 When current flows in the negative direction, the control circuit 41 turns on (conducts) the first switch element 213. As a result, the parallel combined resistance of the second detection resistor 212 and the first reset resistor 211 is used as the detection resistor, and the first detection resistor 231 is used as the reset resistor. At this time, the high potential side of the voltage across both ends of the parallel combined resistance of the second detection resistor 212 and the first reset resistor 211 is connected to the ground terminal 53, and a negative voltage generated on the low potential side passes through the positive voltage level shift circuit 251 and is converted to the second detection voltage V CS2 to the control circuit 41.

[0040] The positive voltage level shift circuit 251 converts the waveform detected by the second detection resistor 212 into a waveform of a positive voltage level. Here, as a circuit for converting a waveform of a negative voltage level into a waveform of a positive voltage level, for example, a circuit that inverts the positive and negative polarity of the waveform may be used, or a circuit that level-shifts the voltage of the waveform in the positive direction may be used.

[0041] By such an operation, it becomes possible to accurately detect the current even when a pulsed direct current flows through the primary side of the current transformer 81 in either the positive or negative direction.

[0042] When the current on the primary side of the current transformer 81 flows in both positive and negative directions, not only when the switching current is a current flowing opposite to a predetermined direction, but also when the switching current is a current flowing in a predetermined direction, the first switch element 213 may be made conductive, so that the first detection resistor 231 serves as a detection resistor for the current flowing in the predetermined direction, and the second detection resistor 212 serves as a reset resistor.

[0043] FIG. 3 is a diagram showing a configuration of a positive voltage level shift circuit 251a of the current detection unit 31a according to the first embodiment. The current detection unit 31 a is a specific example of the current detection unit 31 . The positive voltage level shift circuit 251 a is a specific example of the positive voltage level shift circuit 251 .

[0044] The positive voltage level shift circuit 251a is a circuit that uses an inverting amplifier circuit. The inverting amplifier circuit is configured using an operational amplifier 271, a resistor 272, and a resistor 273. Specifically, one end of the resistor 272 is connected to a point between the first switch element 213 and the second detection resistor 212. The other end of the resistor 272 and one end of the resistor 273 are connected, and the point between these is connected to the negative input terminal of the operational amplifier 271. The other end of the resistor 273 and the output terminal of the operational amplifier 271 are connected, and these are connected to the second detection voltage V CS2 The operational amplifier 271 has a positive input terminal connected to the ground terminal 53.

[0045] [Regarding the first embodiment] As described above, in the power system 1 according to the present embodiment, in the switching power supply, the detection resistor is switched by the switch element (first switch element 213) according to the operating state of the DC-DC converter 2, so that it is possible to detect a bidirectional current using the current transformer 81. This makes it possible for the current detection unit 31 to accurately detect a current regardless of whether a pulsed DC current flows in the positive or negative direction on the primary side of the current transformer 81. In the current detection unit 31 according to this embodiment, it is possible to finely adjust the characteristics when detecting the current flowing through the current transformer 81 in each of the two directions.

[0046] In the current detection unit 31 according to this embodiment, in the secondary circuit of the current transformer 81 (current-voltage conversion unit 82 in this embodiment), the detection resistors (first detection resistor 231, second detection resistor 212, and first reset resistor 211 used as a detection resistor) and reset resistors (first reset resistor 211, first detection resistor 231 used as a reset resistor) are switched according to the direction of the current. As a result, the current I CT2 The functions of the sense resistor and reset resistor are switched depending on the direction of the resistor.

[0047] Therefore, in the current detection unit 31, it is possible to make the resistance value of the detection resistor different during forward and reverse operation, and it is possible to select a resistor having an optimum resistance value as the detection resistor during each operation. This makes it possible to finely adjust the detection level during each operation by changing the resistance value.

[0048] In addition, in the current detection unit 31, it is possible to make the resistance value of the reset resistor different between forward operation and reverse operation, and it is possible to select a resistor having an optimum resistance value as the reset resistor for each operation. This makes it possible to finely adjust the resistance value to ensure a reliable reset for each operation.

[0049] In addition, by switching the reset resistor during each operation, it is possible to avoid nonlinear characteristics, for example, regarding the relationship between the load current and the peak value of the detection voltage during a light load. Here, during a light load, the current I CT1 Whether the sense of the potential is positive or negative, there may be cases where current flows in both directions.

[0050] Here, in the example of FIG. 2 according to the first embodiment, compared to the example of FIG. 5 according to the second embodiment, the second reset resistor 411 and the second switch element 412 for switching the reset resistor during reverse operation are omitted. For example, in the period T off2 If the time t1 is sufficiently long, a sufficient reset time can be ensured when resetting the current transformer 81 during reverse operation, and therefore the configuration shown in FIG. 2 according to the first embodiment is effective. Furthermore, for example, when the charging current of the DC power supply 11 during reverse operation is small, the configuration shown in FIG. 2 according to the first embodiment is effective. Thus, in the current detection unit 31 shown in FIG. 2 according to the first embodiment, the range of usable current or voltage is narrower than that in the example of FIG. 5 according to the second embodiment, but the number of components can be reduced.

[0051] Here, as the first switch element 213, for example, a semiconductor switch element such as a MOS-FET or a bipolar transistor, a mechanical switch element, or a photocoupler may be used. When a MOS-FET is used, the polarity of the built-in body diode of the MOS-FET is connected between both ends of the secondary winding 92 of the current transformer 81 in a direction opposite to the polarity of the diodes 214 and 232 connected in series therewith. In addition, any driving method may be used as a method for driving these switch elements.

[0052] Furthermore, for example, an inverting amplifier circuit or a differential amplifier circuit using an operational amplifier can be applied to the positive voltage level shift circuit 251, but the present invention is not limited to these. In addition, an amplifier circuit such as a common emitter amplifier using a bipolar transistor may be used, and further, if a function is built into the control circuit in the control circuit 41, that function may be used.

[0053] Second embodiment In the second embodiment, differences from the first embodiment will be described in detail, and detailed description of similarities to the first embodiment will be omitted.

[0054] [Power System] FIG. 4 is a diagram showing a configuration of a power system 301 according to the second embodiment. In FIG. 4, for ease of explanation, components similar to those in the power system 1 shown in FIG. 1 are denoted by the same reference numerals, and detailed explanations thereof will be omitted. In the example of FIG. 4 relating to the second embodiment, the configuration of the current-voltage conversion unit 382 and the control by the control circuit 341 are different from the example of FIG. 1 relating to the first embodiment, and therefore the current detection unit 331 and the DC-DC converter 302 are different. In this embodiment, the control circuit 341 also outputs a switch change-over signal SW2 to the current-voltage converter 382.

[0055] [Current detection section] FIG. 5 is a diagram showing a configuration of a current detection unit 331 according to the second embodiment. 5, for convenience of explanation, the same components as those of the current detection unit 31 shown in FIG. 2 are denoted by the same reference numerals, and detailed explanations thereof will be omitted. The current-voltage conversion unit 382 shown in FIG. 5 differs from the example in FIG. 2 in that the second reset resistor 411 (second reset resistor R rst2 2 in that it is provided with a second switch element 412. Also, the control circuit 341 differs from the example in FIG. 2 in that it also controls the second switch element 412.

[0056] 5, the diode 232 and the second reset resistor 411 are connected in series. This series connection circuit is connected in parallel with the secondary winding 92 of the current transformer 81. The second switch element 412 and the first detection resistor 231 are connected in series. This series connection circuit is connected in parallel with the second reset resistor 411. The voltage across the parallel combined resistance of the first detection resistor 231 and the second reset resistor 411 is determined by connecting the low potential side to the ground terminal 53 and the positive voltage generated on the high potential side to the first detection voltage VCS1 The signal is connected to the control circuit 341 so as to be input to the control circuit 341 as a signal.

[0057] An example of the operation of the current detection unit 331 will be described. The current to be detected on the secondary side of the current transformer 81 is I CT2 When current flows in the positive direction, the control circuit 341 turns the first switch element 213 off (non-conductive) and turns the second switch element 412 on (conductive). As a result, the parallel combined resistance of the first detection resistor 231 and the second reset resistor 411 is used as the detection resistor, and the first reset resistor 211 is used as the reset resistor. At this time, the waveform detected by the parallel combined resistance of the first detection resistor 231 and the second reset resistor 411 is the first detection voltage V CS1 to the control circuit 341.

[0058] On the other hand, the detected current I CT2 is flowing in the negative direction, the control circuit 341 turns the first switch element 213 on (conducting) and turns the second switch element 412 off (non-conducting). As a result, the parallel combined resistance of the second detection resistor 212 and the first reset resistor 211 is used as the detection resistor, and the second reset resistor 411 is used as the reset resistor. At this time, the high potential side of the voltage across both ends of the parallel combined resistance of the second detection resistor 212 and the first reset resistor 211 is connected to the ground terminal 53, and the negative voltage generated on the low potential side is converted to the second detection voltage V via the positive voltage level shift circuit 251. CS2 to the control circuit 341. The positive voltage level shift circuit 251 converts the waveform detected by the second detection resistor 212 into a waveform of a positive voltage level.

[0059] By such an operation, it becomes possible to accurately detect the current even when a pulsed direct current flows through the primary side of the current transformer 81 in either the positive or negative direction.

[0060] The current I CT1 and the secondary side detected current ICT2 When current flows in both the positive and negative directions, the control circuit 341 turns on both the first switch element 213 and the second switch element 412, and either one of the parallel combined resistance of the first detection resistor 231 and the second reset resistor 411 and the parallel combined resistance of the second detection resistor 212 and the first reset resistor 211 is used as the detection resistor and the other is used as the reset resistor, thereby improving the linearity of the load current detection when the main circuit is lightly loaded. In this case, during forward operation, the parallel combined resistance of the first detection resistor 231 and the second reset resistor 411 is used as the detection resistor, and the parallel combined resistance of the second detection resistor 212 and the first reset resistor 211 is used as the reset resistor, while during reverse operation, the parallel combined resistance of the first detection resistor 231 and the second reset resistor 411 is used as the reset resistor, and the parallel combined resistance of the second detection resistor 212 and the first reset resistor 211 is used as the detection resistor. Note that such control does not necessarily have to be performed. In this embodiment, the main circuit is a circuit in which a current is detected by the current detection unit 331, and is a portion of the circuit of the DC-DC converter 2 excluding the circuit of the current detection unit 331.

[0061] [Waveform during forward operation] A forward operation (in this embodiment, an operation of transmitting power from the primary side to the secondary side) will be described. In forward operation, the power supply V HV The power supply V LV It charges the auxiliary battery and supplies power to the vehicle loads.

[0062] In FIG. 6, (A) to (G) are diagrams showing operational waveforms of each unit according to the second embodiment. FIG. 6A shows an operational waveform 1011 indicating the on and off timing of the FET 12. FIG. 6B shows an operational waveform 1012 indicating the on and off timing of the FET 13. FIG. 6C shows an operational waveform 1013 indicating the on and off timing of the FET 14. FIG. 6D shows an operational waveform 1014 indicating the on and off timing of the FET 15. FIG. 6E shows the primary current I CT1 10 shows an operational waveform 1015. FIG. 6F shows the first detection voltage V CS1 10 shows an operational waveform 1016. FIG. 6G shows the second detection voltage V CS2 10 shows an operational waveform 1017.

[0063] In this embodiment, there are four modes depending on the combination of on / off timings of the four FETs 12 to 15. Mode 1-1 is a mode during which both FET 12 (represented as S1 in FIG. 6; control voltage A to the switch element) and FET 15 (represented as S4 in FIG. 6; control voltage D to the switch element) are on. Mode 1-2 is a mode during which both FET 12 (represented as S1 in FIG. 6; control voltage A to the switch element) and FET 14 (represented as S3 in FIG. 6; control voltage C to the switch element) are on. Mode 1-3 is a mode during which both FET 13 (represented as S2 in FIG. 6; control voltage B to the switch element) and FET 14 (represented as S3 in FIG. 6; control voltage C to the switch element) are on. Mode 1-4 is a mode during which both FET 13 (represented as S2 in FIG. 6; control voltage B to the switch element) and FET 15 (represented as S4 in FIG. 6; control voltage D to the switch element) are on.

[0064] Here, a pulse that is high (High: hereinafter referred to as Hi) in mode 1-1 and mode 1-3 and low (Low: hereinafter referred to as Lo) in mode 1-2 and mode 1-4 is defined as a PWM pulse. The length of mode 1-1 and the length of mode 1-3 are each time T on1 It is. The length of mode 1-2 and the length of mode 1-4 are each time Toff1 It is. Time T on1 and time T off2 The sum of these is the time T sw1-2 It becomes. The total value of the periods of Mode 1-1 to Mode 1-4 is the time T sw1-1 It becomes.

[0065] In a steady state, the Duty 1 of each of the four FETs 12 to 14, which determines the on / off timing of the four FETs 12 to 15, is fixed at 50%. In this embodiment, a case will be described in which the voltage control method is phase shift control. In practice, it is common to provide a dead time, which is a short period during which both FET12 and FET13, and both FET14 and FET15 are off, between the timing of turning off FET12 and turning on FET13, the timing of turning on FET12 and turning off FET13, the timing of turning off FET14 and turning on FET15, and the timing of turning on FET14 and turning off FET15. However, in this embodiment, for the sake of simplicity, such dead time will be ignored.

[0066] It is possible to perform synchronous rectification operation by combining the on / off of FET22 (control voltage E to switch element) and FET23 (control voltage E to switch element) with the on / off of FET21 (control voltage F to switch element) and FET24 (control voltage F to switch element). However, in this embodiment, for the sake of simplicity, an on-period is not provided for these, and they are operated using body diodes.

[0067] In mode 1-1, when FET 12 and FET 15 are turned on, a voltage V HV is applied, the body diodes of FET 21 and FET 24 become conductive, power is transmitted to the secondary side of the transformer 16, power is supplied to the output, and energy is stored in the choke coil 25. In mode 1-2, the leakage inductance L of the transformer 16 lk Due to the energy stored in the leakage inductance L lk , primary winding 61, FET 14, FET 12, leakage inductance L lk At the same time, the body diodes of FET21 to FET24 are rendered conductive from the choke coil 25, and energy is released to the output. In mode 1-3, when FET 13 and FET 14 are turned on, a voltage V HV is the voltage with the opposite polarity (-V HV ) is applied, the body diodes of FET 22 and FET 23 become conductive, power is transmitted to the secondary side of transformer 16, power is supplied to the output, and energy is stored in choke coil 25. In modes 1-4, the leakage inductance L of the transformer 16 lk Due to the energy stored in the leakage inductance L lk , FET13, FET15, primary winding 61, leakage inductance L lk At the same time, the body diodes of FET21 to FET24 are rendered conductive from the choke coil 25, and energy is released to the output.

[0068] The control circuit 341 generates a signal to turn on the second switch element 412 and turn off the first switch element 213. This causes the current I CT1 During the periods of mode 1-1 and mode 1-3, when the secondary side detectable current I CT2 flows in the positive direction, the diode 232 becomes conductive, and a current flows through the first detection resistor 231 and the second reset resistor 411. As a result, this current becomes the first detection voltage V CS1 and input to the control circuit 341.

[0069] On the other hand, during the periods of mode 1-2 and mode 1-4 in which no input current flows, the primary current I CT1 During this period, the detected current I CT2flows in the negative direction, the diode 232 becomes non-conductive, and the diode 214 becomes conductive, so that the first reset resistor 211 magnetically resets the current transformer 81. As a result of the above, the current detection unit 331 can accurately detect the current during forward operation.

[0070] [Waveform during reverse operation] The reverse operation will now be described. During reverse operation, the power supply V LV The auxiliary battery is connected to the power supply V HV The high-voltage battery is charged.

[0071] In FIG. 7, (H) to (L) are diagrams showing operational waveforms of each unit according to the second embodiment. FIG. 7H shows an operational waveform 1018 indicating the on and off timing of the FET 22 and the FET 23. FIG. 7(I) shows an operational waveform 1019 indicating the on and off timing of the FET 21 and the FET 24. FIG. 7(J) shows the primary current I CT1 10 shows an operational waveform 1020. FIG. 7(K) shows the first detection voltage V CS1 10 shows an operational waveform 1021. FIG. 7(L) shows the second detection voltage V CS2 10 shows an operational waveform 1022.

[0072] In this embodiment, there are four modes depending on the combination of on / off timings of the four FETs 21 to 24. Mode 2-1 is a mode in which FET22 (represented as S6 in FIG. 7; control voltage E to the switch element), FET23 (represented as S7 in FIG. 7; control voltage E to the switch element), FET21 (represented as S5 in FIG. 7; control voltage F to the switch element), and FET24 (represented as S8 in FIG. 7; control voltage F to the switch element) are all on. Mode 2-2 is a mode during which both FET 22 (represented as S6 in FIG. 7; control voltage E to the switch element) and FET 23 (represented as S7 in FIG. 7; control voltage E to the switch element) are on. Mode 2-3 is a mode in which FET22 (represented as S6 in FIG. 7; control voltage E to the switch element), FET23 (represented as S7 in FIG. 7; control voltage E to the switch element), FET21 (represented as S5 in FIG. 7; control voltage F to the switch element), and FET24 (represented as S8 in FIG. 7; control voltage F to the switch element) are all on. Mode 2-4 is a mode during which both FET 21 (represented as S5 in FIG. 7; control voltage F to the switch element) and FET 24 (represented as S8 in FIG. 7; control voltage F to the switch element) are on.

[0073] In a steady state, the on / off timing of the FETs 21 to 24 is determined by the control voltages E and F. It is possible to perform synchronous rectification operation by combining the on / off of FETs 12 to 15. However, in this embodiment, for the sake of simplicity, an on-period is not provided for these, and operation is performed using body diodes.

[0074] In mode 2-1, when the FETs 21 to 24 are turned on, one side of the choke coil 25 is short-circuited to the ground (GND), and a DC voltage V LV is applied and energy is stored. In mode 2-2, when FET 21 and FET 24 are turned off, the choke coil 25 operates as a current source, and the choke coil 25, FET 23, the secondary winding 62 of the transformer 16, FET 22, and the voltage V LV At this time, on the primary side of the transformer 16, the body diodes of the FETs 13 and 14 are conductive, and the primary winding 61 of the transformer 16, the FET 14, the primary winding 91 of the current transformer 81, and the voltage V HVSince a current flows through the path of the FET 13 and the primary winding 61 of the transformer 16, power is transmitted to the primary side of the transformer 16. In mode 2-3, when the FETs 21 to 24 are turned on, one side of the choke coil 25 is short-circuited to the ground (GND), and a DC voltage V LV is applied and energy is stored. In mode 2-4, when FET 22 and FET 23 are turned off, choke coil 25 operates as a current source, and the choke coil 25, FET 21, secondary winding 62 of transformer 16, FET 24, and voltage V LV At this time, on the primary side of the transformer 16, the body diodes of the FET 12 and the FET 15 are conductive, and the primary winding 61 of the transformer 16, the FET 12, the primary winding 91 of the current transformer 81, and the voltage V HV Since a current flows through the path of the FET 15 and the primary winding 61 of the transformer 16, power is transmitted to the primary side of the transformer 16.

[0075] The control circuit 341 generates a signal to turn on the first switch element 213 and turn off the second switch element 412. As a result, the current I CT1 During the periods of mode 2-2 and mode 2-4, when the secondary side sensed current I CT2 flows in the negative direction, the diode 214 becomes conductive, and a current flows through the second detection resistor 212 and the first reset resistor 211. As a result, this current is equal to the second detection voltage V CS2 The negative voltage is shifted to a positive voltage level by the positive voltage level shift circuit 251, thereby generating a second detection voltage V CS2 and input to the control circuit 341.

[0076] On the other hand, during the periods of mode 2-1 and mode 2-3 in which the input current does not flow, the primary current I CT1 During this period, the detected current I CT2flows in the forward direction, the diode 214 becomes non-conductive, and the diode 232 becomes conductive, so that the second reset resistor 411 performs magnetic reset of the current transformer 81. As a result, the current detection section 331 can accurately detect the current during reverse operation.

[0077] [Control circuit] 8, a method for determining the switch change-over signals SW1 and SW2 and a method for determining the first detection voltage V CS1 and the second detection voltage V CS2 Explain how to apply this. The control circuit 41 receives a mode selection signal SEL and a voltage V LV_sense and the first detection voltage V CS1 and the HV voltage sense value, V HV_sense and the second detection voltage V CS2 The control circuit 100 outputs the generated pulses, that is, control voltages A to D and control voltages E to F, and switch change-over signals SW1 and SW2.

[0078] FIG. 8 is a diagram showing a configuration of a control circuit 341 according to the second embodiment. The control circuit 341 includes a reference power supply 511, an error amplifier 512 (E / A), a slope voltage source 513, an adder 514, a comparator 515, a reference pulse generator 516, a pulse generating unit 517, a reference power supply 531, an error amplifier (E / A) 532, a reference pulse generator 533, a pulse generating unit 534, a short circuit current protection unit 551, a NOR circuit 552, and a mode selection unit 571.

[0079] The error amplifier 512 is connected to the reference voltage V ref1 and voltage V LV_sense Amplify the difference between. In the example of FIG. 8, the reference voltage V ref1 is input, and the voltage V LV_sense is entered. Here, the negative side of the reference power supply 511 is connected to the ground terminal 53 .

[0080] The adder 514 calculates the first detection voltage V cs1 and the slope compensation voltage V supplied from the slope voltage source 513. slope and add. The comparator 515 compares the output from the error amplifier 512 with the output from the adder 514 . In the example of FIG. 8, the addition result by the adder 514 is input to the positive input terminal of the comparator 515, and the output from the error amplifier 512 is input to the negative input terminal of the comparator 515.

[0081] An enable signal EN1 output from a mode selection section 571 is input to an enable terminal (EN) of the pulse generation section 517. The pulse generating unit 517 operates when enabled by the enable signal EN1. The enable signal EN1 is a Hi (high) or Lo (low) signal. When the input enable signal becomes Lo, the pulse generating unit 517 stops operating, and the operation of the main circuit stops for a certain period of time.

[0082] The pulse generating unit 517 generates a reference pulse V base The control circuit 303 receives timing information of the FETs 12 to 15 (reference voltage) and generates pulse signals used for driving the gates of the FETs 12 to 15 based on the timing information, and outputs the pulse signals to the gates of the FETs 12 to 15. This performs current mode control in the main circuit of the DC-DC converter 302. Note that, as the current mode control, for example, general control may be performed. In the example of FIG. 8, the output from the comparator 515 and the reference pulse V base is entered.

[0083] The error amplifier 532 is driven by the reference voltage V ref2 and voltage VHV_sense Amplify the difference between. In the example of FIG. 8, a reference voltage V ref2 is input, and the voltage V HV_sense is entered. Here, the negative side of the reference power supply 531 is connected to the ground terminal 53 .

[0084] An enable signal EN2 output from a NOR circuit 552 is input to an enable terminal (EN) of the pulse generating unit 534. The pulse generating unit 534 operates when enabled by the enable signal EN2.

[0085] The pulse generating unit 534 receives the output from the error amplifier 532 and the reference pulse V s The control circuit 303 receives timing information of the reference voltage (a triangular wave voltage) and generates pulse signals used for driving the gates of the FETs 21 to 24 based on the timing information, and outputs the pulse signals to the gates of the FETs 21 to 24. This controls the voltage mode in the main circuit of the DC-DC converter 302. Note that, for example, general control may be performed as the voltage mode control. In the example of FIG. 8, the output from the error amplifier 532 and the reference pulse V s is entered.

[0086] A second detection voltage V CS2 is entered. Here, in the short circuit current protection unit 551, for example, a detection threshold and a recovery threshold are set in advance. In addition, the short circuit current protection unit 551 receives the second detection voltage V CS2 When the second detection voltage V exceeds a predetermined detection threshold, the short circuit current protection unit 551 outputs an enable signal that is switched from Hi to Lo. CS2When the output voltage Vcc falls below a predetermined recovery threshold, the output enable signal is switched from Lo to Hi. As the short circuit current protection unit 551, for example, a comparator is used, but the invention is not limited to this.

[0087] NOR circuit 552 receives as input the enable signal output from short circuit current protection unit 551 and the enable signal output from mode selection unit 571, and outputs enable signal EN2 corresponding to these to pulse generation unit 534. As a result, the enable signal output from mode selection unit 571 and the enable signal output from short circuit current protection unit 551 are input to the enable terminal (EN) of pulse generation unit 534. When the input enable signal becomes Lo, the pulse generating unit 534 stops operating, and the operation of the main circuit stops for a certain period of time.

[0088] The mode selection unit 571 selects either the forward operation or the reverse operation. The mode selection unit 571 receives a selection signal SEL output from the external microcomputer 111. The mode selection unit 571 then outputs a switch changeover signal SW1 and a switch changeover signal SW2 based on the value of the input selection signal SEL.

[0089] Here, the external microcomputer 111 outputs a Hi signal as the selection signal SEL when instructing a forward direction operation, and outputs a Lo signal as the selection signal SEL when instructing a reverse direction operation. When a Hi selection signal SEL is input, the mode selection unit 571 operates in the forward direction, by setting the switch change-over signal SW1 to the first switch element 213 to Lo, setting the switch change-over signal SW2 to the second switch element 412 to Hi, setting the enable signal EN1 to the pulse generation unit 517 to Hi, and setting the enable signal (signal that becomes the enable signal EN2) to the pulse generation unit 534 to Lo. On the other hand, when a Lo selection signal SEL is input, the mode selection unit 571 performs reverse operation by setting the switch change-over signal SW1 to the first switch element 213 to Hi, setting the switch change-over signal SW2 to the second switch element 412 to Lo, setting the enable signal EN1 to the pulse generation unit 517 to Lo, and setting the enable signal (signal that becomes the enable signal EN2) to the pulse generation unit 534 to Hi.

[0090] As a result, in the control circuit 41, the first detection voltage V CS1 In addition, the control circuit 41 detects the second detection voltage V CS2 and generates pulse-shaped control voltages E to F. As described above, with reference to FIG. 8, the method of determining the switch change-over signals SW1 and SW2 and the first detection voltage V CS1 and the second detection voltage V CS2 However, the determination method and application method are not limited to this.

[0091] [Regarding the second embodiment] As described above, in the power system 301 according to this embodiment, by switching the switch elements (the first switch element 213 and the second switch element 412) in accordance with the operating state of the DC-DC converter 302 in the switching power supply, it is possible to detect a bidirectional current using the current transformer 81. This makes it possible for the current detection unit 331 to accurately detect a current regardless of whether a pulsed DC current flows in the positive or negative direction on the primary side of the current transformer 81. In the current detection unit 31 according to this embodiment, it is possible to finely adjust the characteristics when detecting the current flowing through the current transformer 81 in each of the two directions.

[0092] In the current detection unit 331 according to this embodiment, in the secondary circuit of the current transformer 81 (current-voltage conversion unit 382 in this embodiment), the detection resistor (first detection resistor 231, second detection resistor 212) and the reset resistor (first reset resistor 211, second reset resistor 411) are switched according to the direction of the current. As a result, the current I CT2 The sense resistor and the reset resistor are switched according to the direction of the

[0093] Therefore, in the current detection unit 331, it is possible to make the resistance value of the detection resistor different during forward operation and during reverse operation, and it is possible to select a resistor having an optimum resistance value as the detection resistor during each operation. This makes it possible to finely adjust the characteristics during each operation by changing the resistance value.

[0094] In addition, in the current detection unit 331, it is possible to make the resistance value of the reset resistor different between forward operation and reverse operation, and it is possible to select a resistor having an optimum resistance value as the reset resistor for each operation. This makes it possible to finely adjust the characteristics for each operation by changing the resistance value. Furthermore, by switching the reset resistor during each operation, it is possible to avoid nonlinear characteristics in the relationship between the load current and the peak value of the detected voltage during light load, for example, which are caused by biased magnetism of the current transformer (a phenomenon that occurs when reset is not performed sufficiently).

[0095] Here, the example of FIG. 5 according to the second embodiment is configured to include a second reset resistor 411 and a second switch element 412 for switching the reset resistor during reverse operation, as compared to the example of FIG. 2 according to the first embodiment. For example, in the period T off2 Even when the distance is short, the configuration shown in FIG. 5 according to the second embodiment is effective. Furthermore, for example, even when the charging current of the DC power supply 11 during reverse operation is large, the configuration shown in FIG. 5 according to the second embodiment is effective. Thus, the current detection unit 331 shown in FIG. 5 according to the second embodiment has a larger number of components than the example in FIG. 2 according to the first embodiment, but has a wider range of usable current or voltage. In this embodiment, for the sake of convenience, similar circuit elements (e.g., resistors, etc.) are denoted by the same symbols in the examples of Figures 2 and 5, but different values ​​may be used for the characteristics (e.g., resistance value, etc.) of each circuit element.

[0096] Here, for example, a semiconductor switch element such as an N-channel MOS-FET or an NPN transistor, a mechanical switch element, or a photocoupler may be used as the second switch element 412. In addition, any driving method may be used as a driving method for these switch elements.

[0097] Third embodiment In the third embodiment, differences from the second embodiment will be described in detail, and detailed description of similarities to the second embodiment will be omitted.

[0098] [Current detection section] FIG. 9 is a diagram showing a configuration of a current detection unit 611 according to the third embodiment. 9, for convenience of explanation, the same components as those of the current detection unit 331 shown in FIG. 5 are denoted by the same reference numerals, and detailed explanations thereof will be omitted. The current detection unit 611 is a specific example of the current detection unit 331 . The positive voltage level shift circuit 631 is a specific example of the positive voltage level shift circuit 251 .

[0099] 9, the positive voltage level shift circuit 631 includes a resistor 651, a resistor 652, and a capacitor 653. In the positive voltage level shift circuit 631, the resistors 651 to 652 and the capacitor 653 are connected to a power supply voltage (voltage V dd ) is used to create a circuit that combines a high-pass filter and a DC bias circuit.

[0100] Specifically, the power supply voltage (V dd ) and ground terminal 53, resistors 651 and 652 are connected in series. A point between the resistor 651 and the resistor 652 and a point between the second detection resistor 212 and the second switch element 412 are connected via a capacitor 653 . In addition, the point between the resistor 651 and the resistor 652 is a second detection voltage V CS2 The signal is connected to the control circuit 341 so as to be input to the control circuit 341.

[0101] Here, the voltage appearing across the second detection resistor 212 is a negative voltage. Therefore, in the positive voltage level shift circuit 631, the DC component of this voltage is cut by a capacitor and the positive power supply is DC biased to produce the second detection voltage V CS2 As a result, the control circuit 341 receives the second detection voltage V CS2 A positive voltage is input.

[0102] [Waveform during reverse operation] In FIG. 10, (H1) to (L1) are diagrams showing operational waveforms of each unit according to the third embodiment. FIG. 10(H1) shows an operational waveform 2012 indicating the on and off timing of the FET 22 and the FET 23. FIG. 10(I1) shows an operational waveform 2012 indicating the on and off timing of the FET 21 and the FET 24. FIG. 10(J1) shows the primary current I CT1 The operating waveform 2013 is shown. FIG. 10(K1) shows the first detection voltage V CS1 The operating waveform 2014 is shown. FIG. 10(L1) shows the second detection voltage V CS2 The operating waveform 2015 is shown.

[0103] In this embodiment, there are four modes depending on the combination of on / off timings of the four FETs 21 to 24. These four modes are similar to the four modes shown in FIG.

[0104] In the case of using a high-pass filter and a DC bias circuit in the positive voltage level shift circuit 631 as in this embodiment, the detection waveform is as shown in Fig. 10(L1). This detection waveform is different from the waveform when the polarity is inverted by the inverting amplifier circuit as shown in Fig. 7(L), for example. From such an operating waveform, the method according to the present embodiment mainly detects the second detection voltage V CS2 It is assumed that the pulse is stopped and protection is provided when the pulse falls below a certain threshold, but the present invention is not limited to this.

[0105] [Regarding the third embodiment] As described above, the power system 301 according to this embodiment can provide the same effects as those of the second embodiment.

[0106] (Regarding the above embodiment) <Configuration example> One configuration example (examples in Figures 2, 3, 5 and 9) is a current detection circuit (circuits of current detection units 31, 31a, 331, 611 in the examples of Figures 2, 3, 5 and 9) that uses a current transformer (current transformer 81 in the examples of Figures 2, 3, 5 and 9) to detect the value of the switching current using a detection resistor, and detects the value of the switching current by switching between the detection resistor and the reset resistor depending on the direction of the switching current flowing on the primary side of the current transformer.

[0107] As one configuration example (example of FIG. 2), the current detection circuit includes a first diode (diode 232 in the example of FIG. 2), a second diode (diode 214 in the example of FIG. 2), a first reset resistor (first reset resistor 211 in the example of FIG. 2), a first detection resistor (first detection resistor 231 in the example of FIG. 2), a second detection resistor (second detection resistor 212 in the example of FIG. 2), a first switch element (first switch element 213 in the example of FIG. 2), and a positive voltage level shift circuit (positive voltage level shift circuit 251 in the example of FIG. 2). A series connection circuit of a first diode and a first detection resistor is connected in parallel to the secondary winding of the current transformer (secondary winding 92 in the example of FIG. 2). A series connection circuit of a second diode and a first reset resistor is connected in parallel to the secondary winding of the current transformer. A series connection circuit of a first switch element and a second detection resistor is connected in parallel with the first reset resistor. The first diode is connected in a direction such that it is conductive when the switching current flows in a predetermined direction (forward direction in the example of FIG. 2). The second diode is connected in a direction that blocks conduction when the switching current flows in the predetermined direction. The positive voltage level shift circuit converts the sensed negative voltage to a positive voltage level using the parallel combination of the second sense resistor and the first reset resistor.

[0108] As one configuration example (the example of FIG. 2), in the current detection circuit, the first switch element is made non-conductive when the switching current is a current flowing in a predetermined direction. When the switching current flows in a direction opposite to the predetermined direction, the first switch element is made conductive.

[0109] As one configuration example (the example in FIG. 2), in a current detection circuit, when current on the primary side of a current transformer flows in both positive and negative directions, not only when the switching current is a current flowing in the opposite direction to a specified direction, but also when the switching current is a current flowing in a specified direction, the first switch element is made conductive, so that the first detection resistor is used as a detection resistor for current flowing in the specified direction, and the second detection resistor is used as a reset resistor.

[0110] As one configuration example (the example of FIG. 5), the current detection circuit includes a first diode (diode 232 in the example of FIG. 5), a second diode (diode 214 in the example of FIG. 5), a first reset resistor (first reset resistor 211 in the example of FIG. 5), a second reset resistor (second reset resistor 411 in the example of FIG. 5), a first detection resistor (first detection resistor 231 in the example of FIG. 5), a second detection resistor (second detection resistor 212 in the example of FIG. 5), a first switch element (first switch element 213 in the example of FIG. 5), a second switch element (second switch element 412 in the example of FIG. 5), and a positive voltage level shift circuit (positive voltage level shift circuit 251 in the example of FIG. 5). A series connection circuit of a first diode and a second reset resistor is connected in parallel to the secondary winding of the current transformer (secondary winding 92 in the example of FIG. 5). A series connection circuit of a second switch element and a first detection resistor is connected in parallel to the second reset resistor. A series connection circuit of a second diode and a first reset resistor is connected in parallel to the secondary winding of the current transformer. A series connection circuit of a first switch element and a second detection resistor is connected in parallel with the first reset resistor. The first diode is connected in a direction such that it is conductive when the switching current flows in a predetermined direction (forward direction in the example of FIG. 5). The second diode is connected in a direction that blocks conduction when the switching current flows in the predetermined direction. A positive voltage level shift circuit converts the sensed voltage to a positive voltage level using a second sense resistor.

[0111] As one configuration example (the example of FIG. 5), in a current detection circuit, when a switching current flows in a predetermined direction, the first switch element is made non-conductive and the second switch element is made conductive. When the switching current flows in a direction opposite to the predetermined direction (negative direction in the example of FIG. 5), the first switch element is made conductive and the second switch element is made non-conductive.

[0112] As one configuration example (the example in FIG. 5), in a current detection circuit, when current on the primary side of the current transformer flows in both positive and negative directions, both the first switch element and the second switch element are made conductive, and during forward operation, the first detection resistor is used as the detection resistor and the second detection resistor is used as the reset resistor, while during reverse operation, the first detection resistor is used as the reset resistor and the second detection resistor is used as the detection resistor.

[0113] As one configuration example (the example of FIG. 3, which may also be applied to FIG. 5), in a current detection circuit (in the example of FIG. 3, current detection unit 31a), a positive voltage level shift circuit (in the example of FIG. 3, positive voltage level shift circuit 251a) includes an operational amplifier.

[0114] As one configuration example (example of FIG. 9), in a current detection circuit (current detection unit 611 in the example of FIG. 9), a positive voltage level shift circuit (positive voltage level shift circuit 631 in the example of FIG. 9) includes a high-pass filter and a DC bias circuit.

[0115] As one configuration example (the example of FIG. 2), in the current detection circuit, the positive voltage level shift circuit includes an amplifier circuit using a transistor.

[0116] As one configuration example (the examples of FIG. 2, FIG. 3, FIG. 5, and FIG. 9), in the current detection circuit, the first switch element is a semiconductor switch element.

[0117] As one configuration example (the examples of FIG. 5 and FIG. 9), in the current detection circuit, the second switch element is a semiconductor switch element.

[0118] One configuration example (the examples in FIGS. 1 and 4) is a power conversion device (the DC-DC converter 2, 302 in the examples in FIGS. 1 and 4) having a current detection circuit.

[0119] As one configuration example (the examples of FIGS. 1 and 4), a power conversion device performs bidirectional operation.

[0120] One configuration example (the examples of FIGS. 1 and 4) is a power system (the power system 1, 301 in the examples of FIGS. 1 and 4) including a power conversion device.

[0121] The functions of any of the components in any of the above-described devices may be realized by a processor. For example, each process in the embodiment may be realized by a processor that operates based on information such as a program and a computer-readable recording medium that stores information such as a program. Here, the functions of each part of the processor may be realized by, for example, individual hardware, or the functions of each part may be realized by integrated hardware. For example, the processor may include hardware, and the hardware may include at least one of a circuit for processing digital signals and a circuit for processing analog signals. For example, the processor may be configured using one or more circuit devices mounted on a circuit board, or one or both of one or more circuit elements. An IC (Integrated Circuit) or the like may be used as the circuit device, and a resistor or a capacitor or the like may be used as the circuit element.

[0122] Here, the processor may be, for example, a CPU. However, the processor is not limited to a CPU, and various processors such as a GPU (Graphics Processing Unit) or a DSP (Digital Signal Processor) may be used. The processor may be, for example, a hardware circuit using an ASIC (Application Specific Integrated Circuit). The processor may be, for example, a plurality of CPUs, or a hardware circuit using a plurality of ASICs. The processor may be, for example, a combination of a plurality of CPUs and a hardware circuit using a plurality of ASICs. The processor may include, for example, one or more of an amplifier circuit or a filter circuit that processes an analog signal.

[0123] Although the embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of this disclosure are also included. [Explanation of symbols]

[0124] 1, 301...power system, 2, 302...DC-DC converter, 11, 28...DC power supply, 12-15, 21-24...FET, 16...transformer, 17, 26, 653...capacitor, 25...choke coil, 27, 272-273, 651-652...resistor, 31, 31a, 331, 611...current detection unit, 32...HV voltage detection unit, 33...LV voltage detection unit, 41, 341...control circuit, 51, 53...ground terminal, 61, 91...primary winding, 62, 92...secondary winding, 63, 93...core, 81...current transformer, 82, 382...current-voltage conversion unit, 111...external microcomputer, 211...first Reset resistor, 212...second detection resistor, 213...first switch element, 214, 232...diode, 231...first detection resistor, 251, 251a, 631...positive voltage level shift circuit, 271...operational amplifier, 411...second reset resistor, 412...second switch element, 511, 531...reference power supply, 512, 532...error amplifier, 513...slope voltage source, 514...adder, 515...comparator, 516, 533...reference pulse generator, 517, 534...pulse generation unit, 551...short circuit current protection unit, 552...NOR circuit, 1011 to 1022, 2011 to 2015...operation waveform

Claims

1. A current detection circuit that detects a value of a switching current by a detection resistor using a current transformer, a circuit for detecting a value of the switching current by switching between the detection resistor and the reset resistor depending on a flow direction of the switching current flowing through the primary side of the current transformer; a first diode, a second diode, a first reset resistor, a first detection resistor, a second detection resistor, a first switch element, and a positive voltage level shift circuit; a series connection circuit of the first diode and the first detection resistor is connected in parallel to a secondary winding of the current transformer, a series-connected circuit of the second diode and the first reset resistor is connected in parallel to a secondary winding of the current transformer, a series connection circuit of the first switch element and the second detection resistor is connected in parallel with the first reset resistor; the first diode is connected in a direction such that it is conductive when the switching current flows in a predetermined direction; the second diode is connected in a direction that prevents conduction when the switching current flows in the predetermined direction; the positive voltage level shift circuit converts a negative voltage detected using a parallel connection of the second detection resistor and the first reset resistor into a positive voltage level; Current sensing circuit.

2. making the first switch element non-conductive when the switching current is a current flowing in the predetermined direction; making the first switch element conductive when the switching current is a current flowing in a direction opposite to the predetermined direction; 2. The current sensing circuit of claim 1.

3. When the current on the primary side of the current transformer flows in both positive and negative directions, By conducting the first switch element not only when the switching current is a current flowing in the opposite direction to the predetermined direction but also when the switching current is a current flowing in the predetermined direction, the first detection resistor is used as a detection resistor for the current flowing in the predetermined direction, and the second detection resistor is used as a reset resistor.

2. The current sensing circuit of claim 1.

4. A current detection circuit that uses a current transformer to detect a value of a switching current through a detection resistor, comprising: a circuit for detecting a value of the switching current by switching between the detection resistor and the reset resistor depending on a flow direction of the switching current flowing through the primary side of the current transformer; a first diode, a second diode, a first reset resistor, a second reset resistor, a first detection resistor, a second detection resistor, a first switch element, a second switch element, and a positive voltage level shift circuit; a series-connected circuit of the first diode and the second reset resistor is connected in parallel to a secondary winding of the current transformer; a series connection circuit of the second switch element and the first detection resistor is connected in parallel to the second reset resistor; a series-connected circuit of the second diode and the first reset resistor is connected in parallel to a secondary winding of the current transformer, a series connection circuit of the first switch element and the second detection resistor is connected in parallel with the first reset resistor; the first diode is connected in a direction such that it is conductive when the switching current flows in a predetermined direction; the second diode is connected in a direction that prevents conduction when the switching current flows in the predetermined direction; the positive voltage level shift circuit converts the voltage sensed using the second sense resistor to a positive voltage level; Current sensing circuit.

5. When the switching current is a current flowing in the predetermined direction, the first switch element is made non-conductive and the second switch element is made conductive; when the switching current is a current flowing in a direction opposite to the predetermined direction, the first switch element is made conductive and the second switch element is made non-conductive.

5. The current detection circuit according to claim 4.

6. when a current on the primary side of the current transformer flows in both positive and negative directions, both the first switch element and the second switch element are made conductive, and the first detection resistor is used as a detection resistor and the second detection resistor is used as a reset resistor during forward operation, while the first detection resistor is used as a reset resistor and the second detection resistor is used as a detection resistor during reverse operation.

6. The current detection circuit according to claim 4 or 5.

7. The positive voltage level shift circuit includes an operational amplifier. The current detection circuit according to any one of claims 1 to 6.

8. The positive voltage level shift circuit includes a high-pass filter and a DC bias circuit. The current detection circuit according to any one of claims 1 to 6.

9. The positive voltage level shift circuit includes an amplifier circuit using a transistor. The current detection circuit according to any one of claims 1 to 6.

10. The first switch element is a semiconductor switch element. The current detection circuit according to any one of claims 1 to 9.

11. The second switch element is a semiconductor switch element.

7. The current detection circuit according to claim 4, wherein the first and second input terminals are connected to the first and second input terminals.

12. A current detection circuit according to any one of claims 1 to 11, Power conversion equipment.

13. The power converter according to claim 12, Power system.

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