Power supply circuit

Abstract

Power supply circuit. Achieving high power conversion efficiency without damaging the rectifier components. An RF signal is input to the rectifier circuit (13) for rectification to obtain a DC signal (DC1). The DC signal (DC1) is set by the output unit (14) to a DC signal (DC2) with a current (voltage) and form suitable for charging the battery (100), and output to the battery side. In the power supply circuit (1), the strength of the RF signal and the voltage and current of the DC signal (DC1) are identified, and the DC signal (DC2) output from the output unit is controlled. A DC input monitoring circuit (16) is provided to monitor the voltage and current values ​​of the DC signal (DC1). The output unit and the battery are considered as virtual load resistors when viewed from the rectifier circuit side of their predecessor. The power conversion efficiency from the RF signal to the DC signal (DC2) depends on the load resistor. The output adjustment unit (17) compares the identified load resistor with the value of the load resistor at which the conversion efficiency reaches its peak, and controls the increase or decrease of the current of the DC signal (DC2) accordingly.

Description

Technical Field

[0001] Embodiments of this disclosure relate to a power supply circuit that supplies a load with a DC signal generated based on a received high-frequency signal. Background Technology

[0002] Power supply circuits (rectenna devices) that output DC power from power input via wireless means such as microwaves (RF power) are used for various applications, such as battery charging. In this case, the input RF signal is rectified to obtain a DC signal, which is then output by a DC-DC converter at the desired voltage or current. Since the strength of the input RF signal is not constant and varies significantly depending on the conditions, the conversion efficiency from the input RF power to the output DC power in such a power supply circuit typically varies considerably depending on the conditions as well.

[0003] In this case, it is preferable to maintain the conversion efficiency as high as possible. Therefore, for example, Patent Document 1 describes a technique where the output of the rectifier circuit to which the input RF signal is received is temporarily open-circuited, the rectified output voltage is monitored at this time, and the output DC output voltage is determined accordingly to maximize the conversion efficiency. Patent Document 1 also describes that the voltage with the highest conversion efficiency is approximately half of the voltage in this case (open-circuit voltage). That is, even if the RF power varies, by measuring the open-circuit voltage in this way and then controlling and outputting the DC voltage, a stable and high conversion efficiency can be obtained. Therefore, Patent Document 2 describes a structure for controlling the DC output.

[0004] Patent Document 1: Japanese Patent No. 6152919

[0005] Patent Document 2: Japanese Patent Application Publication No. 2011-62022 Summary of the Invention

[0006] In the technology described in Patent Document 1, when the output of the rectifier circuit is temporarily open-circuited as described above, the rectifier components may be damaged when the input RF power is large. Furthermore, since the DC output is temporarily stopped when the output of the rectifier circuit is open-circuited for this control, the output efficiency is substantially reduced. Therefore, in a power supply circuit that outputs DC power from received RF power, a technology is required that can achieve high conversion efficiency without causing damage to the rectifier components.

[0007] The power supply circuit disclosed herein outputs a DC signal generated based on a received high-frequency signal to a load. The power supply circuit includes: a rectifier circuit that rectifies the high-frequency signal to output a first DC signal; an output unit that outputs a second DC signal obtained by converting the first DC signal through a DC-DC converter as the DC signal; and an output adjustment unit that identifies a control parameter based on the output state of the first DC signal and controls the increase or decrease of the current of the second DC signal output from the output unit according to the control parameter, thereby increasing the power conversion efficiency from the high-frequency signal to the DC signal.

[0008] According to the power supply circuit disclosed herein, a high power conversion efficiency can be obtained without causing damage to the rectifier components. Attached Figure Description

[0009] Figure 1 This is a diagram showing the structure of the power supply circuit according to the first embodiment.

[0010] Figure 2 This is a graph showing the relationship between power conversion efficiency and load resistance in the power supply circuit of the first embodiment.

[0011] Figure 3 This is a diagram showing the structure of the output adjustment section in the power supply circuit of the first embodiment.

[0012] Figure 4 This is a flowchart illustrating the operation of the output adjustment unit in the power supply circuit of the first embodiment.

[0013] Figure 5 This is a diagram showing an example of the structure of the output section in the power supply circuit of the first embodiment.

[0014] Figure 6 This is a graph showing the relationship between the power conversion efficiency and the first output voltage in the power supply circuit of the second embodiment.

[0015] Figure 7 This is a diagram showing the structure of the output adjustment section in the power supply circuit of the second embodiment.

[0016] Figure 8 This is a flowchart illustrating the operation of the output adjustment unit in the power supply circuit of the second embodiment.

[0017] Figure 9 This is a graph showing the relationship between the power conversion efficiency and the first output current in the power supply circuit of the third embodiment.

[0018] Figure 10 This is a diagram showing the structure of the output adjustment section in the power supply circuit of the third embodiment.

[0019] Figure 11 This is a flowchart illustrating the operation of the output adjustment unit in the power supply circuit of the third embodiment.

[0020] Figure 12 This is a diagram showing the structure of the power supply circuit according to the fourth embodiment.

[0021] Figure 13 This is a diagram showing the structure of the output adjustment section in the power supply circuit of the fourth embodiment.

[0022] Figure 14 These are two examples of the elapsed time of the first output voltage in the power supply circuit of the fourth and fifth embodiments.

[0023] Figure 15 This is a flowchart illustrating the operation of the output adjustment unit in the power supply circuit of the fourth embodiment.

[0024] Figure 16 This is a diagram showing the structure of the power supply circuit according to the fifth embodiment.

[0025] Figure 17 This is a diagram showing the structure of the output adjustment section in the power supply circuit of the fifth embodiment.

[0026] Figure 18 This is a flowchart illustrating the operation of the output adjustment unit in the power supply circuit of the fifth embodiment.

[0027] Label Explanation

[0028] 1, 2, 3: Power supply circuit; 11: Antenna; 12: Matching circuit; 13: Rectifier circuit; 14: Output section; 15: RF input monitoring circuit; 16: DC input monitoring circuit; 17, 27, 28, 37, 38: Output adjustment section; 31: Switch; 32: Waveform measurement section; 81A~81D: FET; 82: Inductor; 83: Capacitor; 84: Resistor; 85: Switch control section; 100: Battery (Storage battery: Load); 141: DC-DC converter; 142: Output conversion circuit; 171, 271, 281, 371, 381: Control section; 172: Division circuit; 173, 272, 282, 372: Storage section. Detailed Implementation

[0029] Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the power supply circuit of this disclosure, a first DC signal, which is the output of the rectifier circuit, is output as a second DC signal converted by a DC-DC converter. Specifically, control parameters identified based on the output state of the first DC signal are set, and the output unit is controlled accordingly to increase the power conversion efficiency from the input high-frequency signal to the output DC signal. Multiple such control parameters can be set.

[0030] (First Embodiment)

[0031] Figure 1 The overall structure of the power supply circuit 1 according to the first embodiment (disclosed) is shown. Here, the output (load) of the power supply circuit 1 is set as a battery (rechargeable battery) 100, and the power supply circuit 1 serves as a charging circuit for the battery 100. Here, an RF input as microwave is received by the antenna 11. The strength of this RF input (RF signal) is not fixed and varies depending on the situation.

[0032] The received RF input (RF signal) is rectified by the matching circuit 12 (RF0: high-frequency signal) used for impedance matching of antenna 11, and then input to rectifier circuit 13 to obtain a DC signal (DC1: first DC signal). DC1 is converted into a DC signal DC2 suitable for charging current (voltage) of battery 100 by output unit 14 and output to battery 100. Output unit 14 consists of DC-DC converter 141 and output conversion circuit 142, which converts the DC signal output by DC-DC converter 141 into a DC output (DC2: second DC signal) suitable for charging battery 100. In practice, DC-DC converter 141 and output conversion circuit 142 are integrated and controlled. The structure of output unit 14 is the same as that described in Patent Document 2, for example; details will be described later.

[0033] The above structure is the same as that of conventional charging devices using rectifier antenna circuits. Here, in the power supply circuit 1, the strength (power value) of RF0, the voltage and current of DC1 are identified, thereby controlling the DC2 output from the output unit 14. Therefore, the power supply circuit 1 includes: an RF input monitoring circuit 15 that monitors the power of RF0; and a DC input monitoring circuit 16 that monitors the voltage and current values ​​of DC1. Based on these measurement results, the output adjustment unit 17 controls the output unit 14 to control the current value of DC2 output from the output unit 14 in a manner that maximizes the conversion efficiency of the power converted from RF0 to DC2. Thus, in this power supply circuit 1, even when the strength of RF0 changes, a high conversion efficiency can always be maintained.

[0034] The following is a detailed explanation of this action. Here, as... Figure 1 As shown, the output unit 14 and the battery 100 can be considered as a virtual load resistance RL when viewed from the rectifier circuit 13 or DC input monitoring circuit 16 in front of them. In this power supply circuit 1, the aforementioned control parameter is set to the value of this load resistance RL. The conversion efficiency η of the power converted from RF0 to DC2 depends on RL. Figure 2 The results were obtained by measuring the dependence of η on RL when the power PRF of RF0 is 500mW, 1000mW, and 1500mW. According to the results, there exists an RL (RL0) that maximizes the conversion efficiency η, and RL0 depends on PRF. Figure 2 The characteristics are obtained according to each PRF value, but the PRF can also be identified by the RF input monitoring circuit 15. On the other hand, Figure 1 RL in the rectifier circuit 13 becomes the voltage / current of the output DC1, and therefore can be identified by the DC input monitoring circuit 16.

[0035] Therefore, if the current PRF is known, the output adjustment unit 17 can match the RL identified as described above with the current PRF. Figure 2 By comparing the value of RL (RL0: optimal load resistance) at which the conversion efficiency η reaches its peak value, the increase or decrease of the current of DC2 can be controlled accordingly. Figure 3 The structure of the output adjustment unit 17 used here is shown in detail. A control unit 171 is provided here to issue signals for controlling the output unit 14. The control unit 171 is input with the current PRF value from the RF input monitoring circuit 15 and the current RL value obtained by the division circuit 172 using the current DC1 voltage VL and current IL obtained from the DC input monitoring circuit 16. Furthermore, a storage unit 173 is provided, which stores the optimal RL value RL0 for each PRF as a lookup table. The control unit 171 can identify the optimal load resistance RL0 corresponding to the currently identified PRF based on this lookup table. In fact, the storage unit 173 stores multiple discrete values ​​of RL0 for each PRF, but the control unit 171 can identify the RL0 corresponding to the identified current PRF by appropriately performing interpolation processing using the current PRF value and the values ​​of each PRF in the lookup table.

[0036] Figure 4is a flowchart illustrating the operation of the control unit 171 at this time. First, the control unit 171 obtains the current PRF value from the RF input monitoring circuit 15 (S11), and identifies the corresponding optimum load resistance RL0 as described above (S12). Next, the control unit 171 obtains the current RL value from the DC input monitoring circuit 16 side (the division circuit 172) (S13).

[0037] The control unit 171 controls the output unit 14 according to the magnitude relationship between the current RL value and RL0. Specifically, when RL < RL0 (S14: Yes), control is performed to reduce the output current from the output unit 14 (S15). As a result, the subsequent RL becomes larger than the current RL, that is, RL approaches RL0. Conversely, when RL > RL0 (S16: Yes), control is performed to increase the output current from the output unit 14 (S17). As a result, the subsequent RL becomes smaller than the current RL, that is, RL approaches RL0. The increase and decrease values of these currents are appropriately set according to the fluctuation state of RF0, so that overshoot and undershoot are less likely to occur. In addition, the above operation can be performed, for example, at fixed time intervals corresponding to the time constant of the temporal variation of RF0.

[0038] Therefore, through the above operation, in this power supply circuit 1, even when the intensity of RF0 fluctuates, the state where the conversion efficiency η is high is maintained (close to Figure 2 the maximum value in the state). At this time, the current PRF value and RL can be identified in a state where DC1 is supplied. Therefore, the output current to the battery 100 is always supplied, and there is no disadvantage (such as damage to the rectifying element) that occurs when the output current is temporarily stopped.

[0039] Figure 5 is a circuit diagram schematically showing an example of the configuration of the output unit 14 that implements this operation. This circuit simplifies the charging IC described in Patent Document 2. Here, as shown in the figure, FETs (Field Effect Transistors) 81A to 81D, an inductor 82, a capacitor 83, a resistor 84, and a switch control unit 85 that controls the switching of each FET are provided. Here, the portion surrounded by the dashed line (FETs 81A and 81B, inductor 82, capacitor 83, and switch control unit 85) operates as a well-known DC-DC converter 141 for converting the voltage of the input DC0. That is, DC1, which is a DC voltage, is pulsed by the on-off operation of the FETs 81A and 81B, and then stepped up (stepped down) using the inductor 82 and the capacitor 83. At this time, the switch control unit 85 controls the duty ratio of the pulses, whereby the voltage can be controlled.

[0040] On the other hand, the switch control unit 85 also controls the on / off state of FETs 81C and 81D. When FET 81C is turned on and FET 81D is turned off, the output of the DC-DC converter directly becomes the output DC2 of the output unit 14. Conversely, when FET 81C is turned off and FET 81D is turned on, the output of the DC-DC converter is output via resistor 84. Therefore, compared to the above situation, the output current of the output unit 14 can be reduced.

[0041] Therefore, by setting multiple resistors 84 and FETs 81D connected to them, the output current can be adjusted. Furthermore, since the switch control unit 85 also controls the DC-DC converter 141, the current value of DC1 can also be adjusted by adjusting its output voltage.

[0042] In addition to adjusting DC1 corresponding to RL as described above, the switch control unit 85 can also control the charging current, which is particularly preferred during the charging of the battery 100, as described in Patent Document 2. That is, during the initial stage of charging the battery 100, it can be charged with a constant current (constant current charging), and when the potential of the battery 100 reaches a fixed value, it can then be charged with a fixed voltage (constant voltage charging). Then, charging can be stopped after the current value of DC2 becomes lower than a fixed value.

[0043] Such control can be appropriately set according to the purpose of the power supply circuit 1 (the connected load). In any case, compared with the technology described in Patent Document 1, it is possible to control the output current without opening the output of the rectifier circuit 13. Therefore, damage to the rectifier components is less likely to occur, and continuous output current can be achieved.

[0044] (Second Implementation)

[0045] exist Figure 1 In the structure, the virtual load resistance RL is used as a control parameter to adjust the increase or decrease of the output current from the output unit 14. Other measured values ​​can also be used as the control parameter to perform the same control. In the semiconductor device of the second embodiment, this control parameter can be set to the voltage VL (first output voltage) of DC1 (first DC signal). Figure 2 Similarly, Figure 6 The results were obtained by measuring the dependence of η on VL when the power PRF of RF0 was 500mW, 1000mW, and 1500mW. In this characteristic, there also exists a VL (VL0: optimal voltage) that maximizes the conversion efficiency η, and VL0 depends on PRF. Therefore, the same control can be achieved using VL.

[0046] Figure 7 and Figure 3Correspondingly, the alternative in this case is shown. Figure 1 The structure of the output adjustment unit 27 used in the output adjustment unit 17 is as described above. Here, only VL is used. In addition, the lookup table stored in the storage unit 272 is composed of the optimal VL value VL0 for each PRF. Figure 6 The peak value of VL is composed of VL.

[0047] and Figure 4 Correspondingly in Figure 8 The diagram shows the operation of the control unit 271 in this situation. In this operation, the control unit 271 will... Figure 4 The RL(RL0) is replaced by VL(VL0). In this case, Figure 4 When performing the action, not only VL (Variable Level) but also IL (Input Level) is required. Conversely, in... Figure 8 In the actions, the same control can be performed using only VL, thus simplifying... Figure 1 The structure of the DC input monitoring circuit 16 in the circuit makes the power supply circuit inexpensive. On the other hand, since only VL information is used, more optimized control can be achieved if the aforementioned output adjustment unit 17, which uses IL in conjunction with VL, is used.

[0048] (Third Implementation)

[0049] In the second embodiment, the voltage VL (first output voltage) of DC1 (first DC signal) is used as the control parameter. In contrast, in the third embodiment, the current IL (first output current) of DC1 (first DC signal), obtained from the DC input monitoring circuit 16 in the same way as VL, is used instead of VL. Therefore, in the second embodiment, the DC input monitoring circuit 16 only needs to identify the voltage VL of DC1, while in this case, the DC input monitoring circuit 16 only needs to identify the current IL of DC1, thus simplifying the structure of the DC input monitoring circuit 16 in the same way.

[0050] Figure 9 Is with Figure 6 The results were obtained by measuring the dependence of η on IL under this condition. In this characteristic, there also exists an IL (IL0: optimal current) that maximizes the conversion efficiency η, and IL0 depends on the PRF. Therefore, the same control can be achieved using IL. Furthermore, Figure 10 and Figure 3 Correspondingly, the alternative in this case is shown. Figure 1 The structure of the output adjustment unit 28 used in the output adjustment unit 17 is as described above. Here, a control unit 281 is used, which, as described above, uses only IL to control the output unit 14. Furthermore, the lookup table stored in the storage unit 282 is composed of the optimal IL value IL0 for each PRF. Figure 9 The peak value of IL is composed of IL.

[0051] and Figure 4 , Figure 8 Correspondingly in Figure 11 The image shows the operation of the control unit 281 in this situation. In this operation, it is assumed that... Figure 8 The voltage VL (VL0) in the equation is replaced by the current IL (IL0). Figure 8 Steps S22, S23, S24, and S26 are changed to Figure 11 Steps S22A, S23A, S24A, and S26A are described above. Here, as the control parameter changes from voltage to current, the current magnitude relationship in steps S24A and S26A is reversed compared to the voltage magnitude relationship in steps S24 and S26. Without any other changes, the output current from the output unit 14 is controlled in the same way to maintain a high conversion efficiency η.

[0052] The specific conditions (voltage VL, current IL) of the first DC signal DC1 vary depending on the received high-frequency signal, antenna 11, matching circuit 12, etc. In this case, it is possible to appropriately set which of VL (second embodiment) or IL (third embodiment) is used to control the output current based on these conditions.

[0053] (Fourth implementation)

[0054] Furthermore, information related to the waveform of the voltage VL of DC1 can also be used as the control parameter mentioned above. This information includes the elapsed time (rise time) of VL from the start of RF0 power supply when DC1 is disconnected. In the power supply circuit 2 of the fourth embodiment, control is performed using this rise time. In this example, similar to the technology described in Patent Document 1, a switch for controlling the on / off state of DC1 is used, but even with high RF power, control is performed to avoid damage to the rectifier components. Moreover, compared to the technology described in Patent Document 1, the time for disconnecting DC1 is only a short initial period, and DC1 remains continuously on during subsequent continuous control of the output current.

[0055] Figure 12 Is with Figure 1A diagram corresponding to the structure of the power supply circuit 2 is shown. Here, similar to the technology described in Patent Document 1, a switch 31 is provided at the output of the DC input monitoring circuit 16. Therefore, the first output voltage VL can be measured both when the switch 31 is on and off. Furthermore, a waveform measurement unit 32 is provided to monitor the waveform of VL with high time resolution, enabling the identification of t1 (described later). The output adjustment unit 37 controls the output unit 14 based on the measurement results of the waveform measurement unit 32. In this case, unlike the power supply circuit 1 described above, the RF input monitoring circuit 15 is not required.

[0056] also, Figure 13 and Figure 3 The structure of the output adjustment unit 37 in this case is shown accordingly. Here, there are: a control unit 371, which controls the switch 31 and the output unit 14 according to the VL (elapsed time) identified by the waveform measurement unit 32; and a storage unit 372, which stores the data (lookup table) required for control.

[0057] Figure 14 The following diagram illustrates the elapsed time of the DC1 voltage (first output voltage) VL, as identified by the waveform measurement unit 32 in the power supply circuit 2, for cases with a large PRF (1) and a small PRF (2). In the initial state (elapsed time = 0), switch 31 is open. In this case, VL (in this case, the open-circuit output voltage) rises from 0 due to the start of RF0 input (power supply). Here, the case with a large PRF (1) corresponds to the situation where the rectifier element of the rectifier circuit 13 may be damaged if no control is performed, while the case with a small PRF (2) corresponds to the situation where such damage is unlikely.

[0058] Figure 15 This is a flowchart illustrating the operation of the control unit 371 in this situation. Here, the initial state (S31) is the point in time when power supply to RF0 begins with switch 31 open. Then, as... Figure 14 As shown in (1) or (2), the open-circuit output voltage VL increases over time.

[0059] Here, the allowable voltage (maximum open-circuit output voltage) Vlimit of VL is set, and it is identified whether VL has reached Vlimit (S32). As described above, in (1), if VL rises to reach Vlimt and continues to be in the open state of switch 31 as shown by the dashed line, VL becomes too large, and the rectifier element may be damaged. Therefore, after VL reaches Vlimt (S32: Yes), the control unit 371 turns on switch 31 and identifies the elapsed time (rise time) t1 up to this point (S33). At this time, by supplying current, a voltage drop occurs, so VL is lower than Vlimit.

[0060] When the PRF is large, t1 is small (shorter rise time); when the PRF is small, t1 is large (longer rise time). That is, t1 can be used instead of PRF.

[0061] Here, in the storage unit 372, instead of the lookup table corresponding to the relationship between PRF and RL0 in the power supply circuit 1, a lookup table is stored representing the optimal (highest conversion efficiency) VL value, i.e., the optimal voltage VLS, for each rise time t1. Therefore, the control unit 371 can identify the VLS corresponding to the identified t1 (S34). Therefore, similar to the case of the first embodiment, control can be performed to reduce the output current when VL is less than VLS and to increase the output current when VL is greater than VLS (S35). At this time, similar to the technology described in Patent Document 1, initially, the switch 31 is open, but after t1, the switch 31 remains on.

[0062] On the other hand, in this case, when both PRF and VL are small, VL sometimes fails to reach Vlimit even after sufficient time. Figure 14 (2) is a diagram illustrating this situation. In this case, a timeout period tTO is preset, and it is determined whether the elapsed time up to the present has reached tTO (S36). If the elapsed time has reached tTO (S36: Yes), switch 31 is turned on regardless of the value of VL, and VL at that time point is identified as the limit open-circuit output voltage V0 (S37). Similar to the technology described in Patent Document 1, if the subsequent VL is set to V0 / 2 (S38), the conversion efficiency can be improved. That is, in this case, since the PRF is small, even if switch 31 is turned off, the rectifier element will not be damaged, and the subsequent actual operation is the same as in Patent Document 1.

[0063] In the above operation, switch 31 is initially turned off only to identify the rise time t1 or the limit open-circuit output voltage V0. At this time, since Vlimit is set, the rectifier elements in rectifier circuit 13 cannot be damaged. Furthermore, in the subsequent control of output current (S35, S38), since switch 31 is turned on, the time for switch 31 to turn off is short. In addition, the timing for identifying t1 or V0 or its start (S31) can be appropriately performed according to the time constant corresponding to the variation of RF0 over a longer time scale. In this case, the output current control (S35, S38) is performed in a way that increases the conversion efficiency of the output corresponding to the variation of RF0 over a shorter time scale.

[0064] (Fifth Embodiment)

[0065] Similar to the fourth embodiment, the control parameters described above are used... Figure 14 The rise time of VL in the equation can be set, but it can also be configured to not use a switch when performing the rise action at this time. Figure 16 Is with Figure 12 A diagram corresponding to this fifth embodiment of the power supply circuit 3 is shown. Here, since the switch 31 is not used, the output adjustment unit 38 does not perform the on / off operation of the switch 31 in the power supply circuit 2.

[0066] Instead, the output adjustment unit 38 performs an operation that minimizes the current of DC2, essentially equivalent to the case where DC1 is not input to the output unit 14 (initial control operation). Furthermore, regarding operations other than this, similar to the power supply circuit 2 described above, the operation of controlling the current value of DC2 based on the rise time (control parameter) (normal control operation) is performed after switching from the initial control operation. In the normal control operation, the current value of DC2 is set to be larger compared to the case of the initial control operation.

[0067] The current value of DC2 (minimum setting value IL20 for the second DC signal) set in the initial control operation is not substantially different from the operation of forcibly disconnecting DC1 input to output unit 14 in the power supply circuit 2 described above, but it does not need to be zero; for example, it is set to 10mA. Therefore, starting from the state where DC2 is set in this way (a state substantially equivalent to the state where DC1 is disconnected), the elapsed time of VL from the state where RF0 is input (power supply has started) is... Figure 14 Same. Figure 14 In the first case, the voltage VL at the origin (when power is initially supplied) is zero. Conversely, in the second case, the voltage VL at the origin is not strictly zero, but in this case, the voltage VL at the origin becomes the basis for identification. Figure 14 The IL20 is set in such a way that the change in VL is negligible. Therefore, the operation of the power supply circuit 2 described above can also be performed in the same way.

[0068] Figure 17 and Figure 13Correspondingly, the structure of the output adjustment unit 38 used in this case is shown. Here, a control unit 381 is provided, which controls only the output unit 14 based on VL (elapsed time) identified by the waveform measurement unit 32; and a storage unit 372. In this power supply circuit 3, when IL20 = 0, the operation of the power supply circuit 3 is in principle the same as the operation of the power supply circuit 2 described above. However, in this case, compared to the timing control of the DC2 current control performed by the output adjustment unit, the timing control of turning the switch 31 on and off in the power supply circuit 2 can be performed with higher precision. On the other hand, the timing control accuracy of the power supply circuit 3 is worse than that of the power supply circuit 2, but since the same control can be performed without using the switch 31, the power supply circuit 3 can be made inexpensive.

[0069] In this case, as a lookup table stored in storage unit 372, as long as Figure 14 The characteristics shown are essentially the same as those in the power supply circuit 2 described above, so the same lookup table as that used in the power supply circuit 2 can be used. Alternatively, by setting IL20 (≠0) as described above... Figure 14 If the characteristics shown have changed, a lookup table that utilizes the newly optimized parameters based on the change can be used.

[0070] Figure 18 This is a flowchart illustrating the operation of the control unit 381 in this situation. Here, with... Figure 15 Compared to the flowchart, the actions of minimizing the output current (initial control action) (S31A) in the initial state instead of opening switch 31 (S31), and switching from the initial control action to the normal control action (S33A, S37A) instead of opening switch 31 (S33, S37), are different. Other actions are the same as... Figure 15 The actions remain unchanged. The Vlimit settings are also the same.

[0071] Besides the examples mentioned above, any quantity identified based on the rectified DC signal and used in power conversion efficiency control can be used as the aforementioned control parameter. Correspondingly, the contents of the lookup table stored in the storage unit can also be appropriately set. Furthermore, in the examples above, RL0 was set as the point where the conversion efficiency η becomes maximum. Figure 2 ), VL0 ( Figure 6 However, these values ​​may not necessarily correspond to the maximum value of the conversion efficiency η, and can also be used as points where the desired conversion efficiency η can be obtained.

[0072] Furthermore, the present invention is not limited to the above-described embodiments, and it is understood that appropriate modifications can be made to each embodiment within the scope of the technical concept of the present invention.

Claims

1. A power supply circuit that outputs a DC signal generated based on a received high-frequency signal to a load, characterized in that, have: A rectifier circuit that rectifies the high-frequency signal to output a first DC signal; The output unit outputs a second DC signal obtained by converting the first DC signal through a DC-DC converter as the DC signal. as well as The output adjustment unit identifies control parameters based on the output state of the first DC signal, and controls the increase or decrease of the current of the second DC signal output from the output unit based on the control parameters, thereby increasing the power conversion efficiency from the high-frequency signal to the DC signal.

2. The power supply circuit according to claim 1, characterized in that, The control parameter is the load resistance observed from the rectifier circuit via the output section when viewing the load side. The power supply circuit has a storage unit that stores a lookup table representing the relationship between the value of an optimal load resistor and the high-frequency power. The optimal load resistor is the load resistor that improves the power conversion efficiency, and the high-frequency power is the power of the high-frequency signal. The output adjustment unit identifies the current high-frequency power and the load resistance, and controls the output unit according to the lookup table, such that when the load resistance is higher than the optimal load resistance corresponding to the identified high-frequency power, the current of the second DC signal is increased, and when the load resistance is lower than the optimal load resistance corresponding to the identified high-frequency power, the current of the second DC signal is decreased.

3. The power supply circuit according to claim 1, characterized in that, The control parameter is a first output voltage, which is the voltage of a first DC signal when the DC signal is supplied to the load side via the output section. The power supply circuit has a storage unit that stores a lookup table representing the relationship between an optimal voltage value and high-frequency power. The optimal voltage is the first output voltage that improves the power conversion efficiency, and the high-frequency power is the power of the high-frequency signal. The output adjustment unit identifies the current high-frequency power and the first output voltage, and controls the output unit according to the lookup table, such that when the first output voltage is higher than the optimal voltage corresponding to the identified high-frequency power, the current of the second DC signal is increased, and when the first output voltage is lower than the optimal voltage corresponding to the identified high-frequency power, the current of the second DC signal is decreased.

4. The power supply circuit according to claim 1, characterized in that, The control parameter is the first output current, which is the current of the first DC signal when the DC signal is supplied to the load side via the output section. The power supply circuit has a storage unit that stores a lookup table representing the relationship between an optimal current value and high-frequency power. The optimal current is the first output current that improves the power conversion efficiency, and the high-frequency power is the power of the high-frequency signal. The output adjustment unit identifies the current high-frequency power and the first output current, and controls the output unit according to the lookup table, such that when the first output current is higher than the optimal current corresponding to the identified high-frequency power, the current of the second DC signal is reduced, and when the first output current is lower than the optimal current corresponding to the identified high-frequency power, the current of the second DC signal is increased.

5. The power supply circuit according to claim 1, characterized in that, The power supply circuit has a switch that controls the on / off state of the first DC signal between the rectifier circuit and the output section. Identify the first output voltage, wherein the first output voltage is the voltage of the first DC signal output from the rectifier circuit. A maximum open-circuit output voltage is set as the maximum value of the open-circuit output voltage, where the open-circuit output voltage is the voltage of the first DC signal when the switch is open. The control parameter is the rise time from when the switch is turned off, from when the high-frequency signal is supplied until the open-circuit output voltage reaches the maximum open-circuit output voltage. The power supply circuit has a storage unit that stores a lookup table representing the relationship between the optimal voltage value and the rise time, wherein the optimal voltage is the first output voltage that improves the power conversion efficiency when the switch is turned on. The output adjustment unit identifies the rise time and the current first output voltage, and controls the output unit according to the lookup table, such that when the first output voltage is higher than the optimal voltage corresponding to the identified rise time, the current of the second DC signal is increased, and when the first output voltage is lower than the optimal voltage corresponding to the identified rise time, the current of the second DC signal is decreased.

6. The power supply circuit according to claim 1, characterized in that, Identify the first output voltage, wherein the first output voltage is the voltage of the first DC signal output from the rectifier circuit. The output adjustment unit is configured to switch between two actions: a normal control action and an initial control action. The normal control action involves controlling the increase or decrease of the current of the second DC signal based on the identified control parameters. The initial control action involves controlling the current of the second DC signal to a fixed value smaller than that in the normal control action, regardless of the control parameters. A maximum open-circuit output voltage is set as the maximum value of the open-circuit output voltage, wherein this open-circuit output voltage is the voltage of the first DC signal at the time of the initial control action. The control parameter is the rise time from the time the high-frequency signal is supplied until the open-circuit output voltage reaches the maximum open-circuit output voltage when the initial control action is executed. The power supply circuit has a storage unit that stores a lookup table representing the relationship between the value of an optimal voltage and the rise time, wherein the optimal voltage is the first output voltage that improves the power conversion efficiency when performing the normal control operation. When performing the normal control operation, the output adjustment unit identifies the rise time and the current first output voltage, and controls the output unit according to the lookup table, such that when the first output voltage is higher than the optimal voltage corresponding to the identified rise time, the current of the second DC signal is increased, and when the first output voltage is lower than the optimal voltage corresponding to the identified rise time, the current of the second DC signal is decreased.

7. The power supply circuit according to any one of claims 1 to 6, characterized in that, The load is a battery, and the DC signal is used as the charging current.

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