Power supply circuit

Abstract

To obtain high power conversion efficiency without causing breakdown of a rectifying element.SOLUTION: An RF signal (RF0) is inputted to a rectifying circuit 13 and rectified to obtain a DC signal (DC1). The outputting section 14 converts the DC1 into a DC signal DC2 having a current (voltage) form suitable for charging of the battery 100 and outputs the DC signal LA to the battery 100 side. In the power source circuit 1, the intensity (power) of the RF0 and the voltage and current of the DC1 are recognized, and thereby the DC2 outputted from the outputting unit 14 is controlled. A DC-input monitor circuit 16 for monitoring the voltage and current values of the DC1 is provided. The output unit 14 and the battery 100 can be considered as a virtual load resistance RL when viewed from the rectifier circuit 13 side at the preceding stage. The power conversion η from RF0 to DC2 depends on RL. The power adjustment unit 17 can compare RL recognized as described above with the value of RL at which the conversion rate η peaks, and can control an increase or decrease in the current of the DC2 in accordance with the comparison result.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present disclosure relates to a power supply circuit that supplies a DC signal generated based on a received high-frequency signal to a load. [Background technology]

[0002] Power supply circuits (rectenna devices) that output DC power based on wireless input power (RF power) such as microwaves are used for a variety of applications, such as battery charging. In these applications, the input RF signal is rectified to obtain a DC signal, which is then output at the desired voltage or current by a DC-DC converter. In this case, the strength of the input RF signal is not constant but varies greatly depending on the situation, so in such power supply circuits, the conversion efficiency from the input RF power to the output DC power also generally varies greatly depending on the situation.

[0003] In this case, it is preferable to maintain this conversion efficiency as high as possible. For this reason, for example, Patent Document 1 describes a technology in which the output of a rectifier circuit to which an RF signal is input is temporarily opened, the rectified output voltage is monitored, and the voltage of the DC output is determined accordingly so as to maximize the conversion efficiency. Patent Document 1 also describes that the voltage at which the conversion efficiency is maximized is approximately half the voltage (open-circuit voltage) in this case. In other words, even if the RF power fluctuates, a stable and high conversion efficiency can be obtained by measuring the open-circuit voltage in this manner and then controlling and outputting the DC voltage in this manner. A configuration for controlling the DC output for this purpose is described in Patent Document 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6152919 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-62022 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Document 1, when the output of the rectifier circuit is temporarily disconnected as described above, the rectifier element may be destroyed if the input RF power is large. Furthermore, when the output of the rectifier circuit is disconnected for this control, the DC output is temporarily stopped, so the output efficiency is substantially reduced. For this reason, there is a need for a technology that can achieve high conversion efficiency without causing damage to the rectifier element in a power supply circuit that outputs DC power from received RF power. [Means for solving the problem]

[0006] The power supply circuit of the present disclosure is a power supply circuit that outputs a DC signal generated based on a received high-frequency signal to a load, and includes: a rectifier circuit that rectifies the high-frequency signal to output a first DC signal; an output unit that converts the first DC signal using a DC-DC converter and outputs the second DC signal as the DC signal; and an output adjustment unit that recognizes a control parameter that is recognized according to the output state of the first DC signal, and controls an increase or decrease in the current of the second DC signal output from the output unit according to the control parameter so as to increase the power conversion efficiency from the high-frequency signal to the DC signal. [Effects of the Invention]

[0007] According to the power supply circuit of the present disclosure, high power conversion efficiency can be obtained without causing damage to the rectifying elements. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration of a power supply circuit according to a first embodiment. [Figure 2] FIG. 3 is a diagram showing the relationship between power conversion efficiency and load resistance in the power supply circuit according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing a configuration of an output adjustment unit in the power supply circuit according to the first embodiment. [Figure 4]5 is a flowchart showing the operation of an output adjusting unit in the power supply circuit according to the first embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of a configuration of an output section in the power supply circuit according to the first embodiment. [Figure 6] FIG. 10 is a diagram showing the relationship between power conversion efficiency and a first output voltage in the power supply circuit according to the second embodiment. [Figure 7] FIG. 10 is a diagram showing a configuration of an output adjustment unit in a power supply circuit according to a second embodiment. [Figure 8] 10 is a flowchart showing the operation of an output adjusting unit in the power supply circuit according to the second embodiment. [Figure 9] FIG. 10 is a diagram showing the relationship between power conversion efficiency and a first output current in the power supply circuit according to the third embodiment. [Figure 10] FIG. 10 is a diagram showing a configuration of an output adjustment unit in a power supply circuit according to a third embodiment. [Figure 11] 10 is a flowchart showing the operation of an output adjusting unit in the power supply circuit according to the third embodiment. [Figure 12] FIG. 10 is a diagram illustrating a configuration of a power supply circuit according to a fourth embodiment. [Figure 13] FIG. 10 is a diagram showing a configuration of an output adjustment unit in a power supply circuit according to a fourth embodiment. [Figure 14] 10 shows two examples of the first output voltage over time in the power supply circuits according to the fourth and fifth embodiments. [Figure 15] 10 is a flowchart showing the operation of an output adjusting unit in the power supply circuit according to the fourth embodiment. [Figure 16] FIG. 10 is a diagram illustrating a configuration of a power supply circuit according to a fifth embodiment. [Figure 17] FIG. 10 is a diagram showing a configuration of an output adjustment unit in a power supply circuit according to a fifth embodiment. [Figure 18] 10 is a flowchart showing the operation of an output adjusting unit in the power supply circuit according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. In the power supply circuit of the present disclosure, a first DC signal output from a rectifier circuit is converted by an output unit using a DC-DC converter to a second DC signal, which is then output. In particular, a control parameter recognized according to the output state of the first DC signal is set, and the output unit is controlled according to the control parameter so as to increase the efficiency of power conversion from an input high-frequency signal to an output DC signal. A plurality of such control parameters can be set.

[0010] (First embodiment) 1 shows the overall configuration of a power supply circuit 1 according to a first embodiment (disclosure). Here, the output (load) of this power supply circuit 1 is a battery (storage battery) 100, and this power supply circuit 1 serves as a charging circuit for this battery 100. Here, an RF input, which is a microwave, is received by an antenna 11. The strength of this RF input (RF signal) is not constant but varies depending on the situation.

[0011] The RF signal (RF0: radio frequency signal) after the received RF input (RF signal) passes through a matching circuit 12 for matching the impedance of the antenna 11 is input to a rectifier circuit 13 and rectified to obtain a DC signal (DC1: first DC signal). DC1 is converted by an output unit 14 into a DC signal DC2 having a current (voltage) and form suitable for charging the battery 100, and is output to the battery 100 side. The output unit 14 includes a DC-DC converter 141 and an output conversion circuit 142 that converts the output DC signal into a DC output (DC2: second DC signal) in a form suitable for charging the battery 100. In practice, the DC-DC converter 141 and the output conversion circuit 142 are controlled as an integrated unit. The configuration of the output unit 14 is similar to that described in, for example, Patent Document 2, and will be described in detail later.

[0012] The above configuration is similar to that of a conventionally known charging device using a rectenna circuit. Here, power supply circuit 1 recognizes the intensity (power value) of RF0 and the voltage and current of DC1, and controls DC2 output from output unit 14 accordingly. Therefore, power supply circuit 1 is provided with RF input monitor circuit 15, which monitors the power of RF0, and DC input monitor circuit 16, which monitors the voltage and current values ​​of DC1. Output adjustment unit 17 controls output unit 14 based on these measurement results, controlling the current value of DC2 output from output unit 14 so as to increase the power conversion efficiency from RF0 to DC2. This allows power supply circuit 1 to maintain high conversion efficiency at all times, even when the intensity of RF0 fluctuates.

[0013] This operation will be described in detail below. As shown in FIG. 1, the output unit 14 and battery 100 can be considered as a virtual load resistance RL when viewed from the rectifier circuit 13 or DC input monitor circuit 16 in the preceding stage. In this power supply circuit 1, the control parameter is the value of this load resistance RL. The power conversion efficiency η from RF0 to DC2 depends on RL. FIG. 2 shows the results of measuring the RL dependence of η when the power PRF of RF0 is 500 mW, 1000 mW, and 1500 mW. These results indicate that there exists an RL (RL0) that maximizes the conversion efficiency η, and RL0 depends on PRF. The characteristics in FIG. 2 are obtained for each PRF value, and the PRF can be recognized by the RF input monitor circuit 15. Meanwhile, RL in FIG. 1 is the voltage / current of the output DC1 of the rectifier circuit 13, and can therefore be recognized by the DC input monitor circuit 16.

[0014] Therefore, if the current PRF is known, the output adjustment unit 17 can compare the RL determined as described above with the RL value (RL0: optimal load resistance) at which the conversion efficiency η peaks in the characteristics shown in FIG. 2, and can control the increase or decrease of the DC2 current accordingly. FIG. 3 shows the detailed configuration of the output adjustment unit 17 for this purpose. Here, a control unit 171 is provided that issues a signal to control the output unit 14. The control unit 171 receives the current PRF value from the RF input monitor circuit 15 and the current RL value calculated by a divider circuit 172 using the current DC1 voltage VL and current IL obtained from the DC input monitor circuit 16. A storage unit 173 is also provided that stores the optimal RL value RL0 for each PRF as a lookup table. The control unit 171 can use this lookup table to determine the optimal load resistance RL0 corresponding to the currently determined PRF. In reality, the memory unit 173 stores RL0 for each of a plurality of discrete values ​​of PRF, but the control unit 171 can recognize the RL0 corresponding to the recognized current PRF by appropriately performing interpolation processing using the current PRF value and each PRF value in the lookup table.

[0015] 4 is a flowchart showing the operation of control unit 171 at this time. First, control unit 171 obtains the current PRF value from RF input monitor circuit 15 (S11), and as described above, recognizes the corresponding optimal load resistance RLO (S12). Next, control unit 171 obtains the current R value from DC input monitor circuit 16 (divider circuit 172) (S13).

[0016] The control unit 171 controls the output unit 14 according to the magnitude relationship between the current value of RL and RL0. Specifically, when RL < RL0 (S14: Yes), it controls 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), it controls 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 variation situation of RF0 so that overshoot and undershoot are not likely to occur. Also, the above operation can be performed at a constant time interval according to, for example, the time constant of the temporal variation of RF0.

[0017] Therefore, by the above operation, in this power supply circuit 1, even when the intensity of RF0 fluctuates, a state where the conversion efficiency η is large (a state close to the maximum value in FIG. 2) is maintained. At this time, the current value of the current PRF and RL can be recognized in the state where DC1 is supplied. For this reason, the output current to the battery 100 is constantly supplied, and no adverse effects (such as destruction of the rectifying element) occur when temporarily stopping this output current.

[0018] FIG. 5 is a circuit diagram showing an example of the configuration of the output unit 14 that realizes this operation, simplified. This circuit is a simplification of the charging IC described in Patent Document 2. Here, as shown in the figure, FETs 81A to 81D, an inductor 82, a capacitor 83, a resistor 84, and a switching control unit 85 that controls the switching of each FET are provided. Here, the portion surrounded by the broken line (FETs 81A, 81B, inductor 82, capacitor 83, switching control unit 85) operates as a well-known DC-DC converter 141 that converts the input DC0 voltage. That is, the DC voltage DC1 is pulsed by the on / off operation of FETs 81A and 81B, and then boosted (or bucked) using the inductor 82 and the capacitor 83. At this time, the voltage can be controlled by the switching control unit 85 controlling the duty ratio of the pulse.

[0019] On the other hand, switching control section 85 also controls the on / off of FETs 81C and 81D. When FET 81C is turned on and FET 81D is turned off, the output of the DC-DC converter becomes output DC2 of output section 14 as is, whereas when FET 81C is turned off and FET 81D is turned on, the output of the DC-DC converter is output via resistor 84. For this reason, the output current of output section 14 can be made lower than in the above case.

[0020] Therefore, if multiple types of resistors 84 and FETs 81D connected to them are provided, the output current can be adjusted. Furthermore, since the switching control section 85 also controls the DC-DC converter 141, the current value of DC1 can also be adjusted by adjusting the output voltage of the DC-DC converter 141.

[0021] In addition to adjusting DC1 according to RL as described above, the switching control unit 85 can also control the charging current, which is particularly preferable for charging the battery 100, as described in Patent Document 2. That is, in the initial stage of charging the battery 100, charging can be performed with a constant current (constant current charging), and then, once the potential of the battery 100 reaches a certain value, charging can be performed so that the voltage remains constant (constant voltage charging). Thereafter, once the current value of DC2 falls below a certain value, charging can be stopped.

[0022] Such control can be set appropriately depending on the purpose (connected load) of this power supply circuit 1. In either case, compared to the technology described in Patent Document 1, the output current can be controlled without opening the output of the rectifier circuit 13. This makes it less likely that the rectifier element will be destroyed, and allows current to be output continuously.

[0023] (Second embodiment) In the configuration of FIG. 1, the increase or decrease in the output current from the output unit 14 is adjusted using a virtual load resistance RL as a control parameter. Similar control can also be performed using other measured quantities as the control parameter. In the semiconductor device according to the second embodiment, this control parameter can be the voltage VL (first output voltage) of DC1 (first DC signal). As with FIG. 2, FIG. 6 shows the results of measuring the VL dependence of η when the power PRF of RF0 is 500 mW, 1000 mW, and 1500 mW. In these characteristics, there is also a VL (VL0: optimal voltage) that maximizes the conversion efficiency η, and VL0 depends on PRF. Therefore, similar control can be performed using VL.

[0024] 7 shows the configuration of output adjustment unit 27 used in this case instead of output adjustment unit 17 in FIG. 1, in correspondence with FIG. 3. Here, only VL is used as described above. The lookup table stored in storage unit 272 is configured with the optimum VL value VL0 (peak VL in FIG. 6) for each PRF.

[0025] The operation of the control unit 271 in this case is shown in Figure 8, corresponding to Figure 4. In this operation, RL (RL0) in Figure 4 is replaced with VL (VL0). In this case, while the operation in Figure 4 required not only VL but also IL, the operation in Figure 8 can perform similar control using only VL, which allows the configuration of the DC input monitor circuit 16 in Figure 1 to be simplified and the power supply circuit to be made inexpensive. On the other hand, because only VL is used as information, more optimal control is possible by using the output adjustment unit 17 described above that uses IL in addition to VL.

[0026] (Third embodiment) In the second embodiment, the voltage VL (first output voltage) of DC1 (first DC signal) is used as the control parameter. In contrast to this, in the third embodiment, the current IL (first output current) of DC1 (first DC signal) obtained from the DC input monitor circuit 16 in the same manner as VL is used instead of VL. Therefore, whereas in the second embodiment, the DC input monitor circuit 16 only needs to recognize the voltage VL of DC1, in this case, the DC input monitor circuit 16 only needs to recognize the current IL of DC1, and similarly, the configuration of the DC monitor circuit 16 can be simplified.

[0027] FIG. 9 corresponds to FIG. 6 and shows the results of measuring the IL dependence of η in this case. Even in this characteristic, there exists an IL (IL0: optimal current) that maximizes the conversion efficiency η, and IL0 depends on the PRF. Therefore, similar control can be performed using IL. Also, FIG. 10 corresponds to FIG. 3 and shows the configuration of output adjustment unit 28, which is used in this case instead of output adjustment unit 17 in FIG. 1. Here, control unit 281 is used that controls output unit 14 using only IL as described above. Also, the lookup table stored in memory unit 282 is configured with the optimal IL value IL0 for each PRF (the IL at the peak in FIG. 9).

[0028] The operation of control unit 281 in this case is shown in Figure 11, corresponding to Figures 4 and 8. In this operation, voltage VL (VL0) in Figure 8 is replaced with current IL (IL0), and steps S22, S23, S24, and S26 in Figure 8 are changed to steps S22A, S23A, S24A, and S26A in Figure 11. Here, since the control parameter has been changed from voltage to current, the magnitude relationship of the currents in steps S24A and S26A is reversed from the magnitude relationship of the voltages in steps S24 and S26. There are no other changes, and the output current from output unit 14 is controlled in the same way, maintaining a high conversion efficiency η.

[0029] The specific conditions (voltage VL, current IL) of the first DC signal DC1 vary depending on the received high-frequency signal, the antenna 11, the matching circuit 12, etc. In this case, whether VL (second embodiment) or IL (third embodiment) is used to control the output current can be set appropriately depending on such conditions.

[0030] (Fourth embodiment) Furthermore, information related to the waveform of the voltage VL of DC1 can also be used as the control parameter. Such information includes the time lapse (rise time) of VL after power supply to RF0 begins with DC1 turned off, and the power supply circuit 2 according to the fourth embodiment performs control using this rise time. Furthermore, in this example, similar to the technology described in Patent Document 1, a switch is used to control the on / off of DC1, but control is performed so as not to damage the rectifying element even when the RF power is large. Furthermore, compared to the technology described in Patent Document 1, DC1 is turned off only for a short period of time at the beginning, and DC1 is continuously turned on during subsequent continuous control of the output current.

[0031] FIG. 12 is a diagram showing the configuration of this power supply circuit 2 in correspondence with FIG. 1. Here, similar to the technology described in Patent Document 1, a switch 31 is provided at the output of the DC input monitor circuit 16. Therefore, the first output voltage VL can be measured with the switch 31 in the on and off states. In addition, a waveform measurement unit 32 is provided that monitors the waveform of VL with high time resolution so that t1, which will be described later, can be recognized, and an output adjustment unit 37 controls the output unit 14 in accordance with the measurement results of the waveform measurement unit 32. In this case, unlike the power supply circuit 1 described above, the RF input monitor circuit 15 is not required.

[0032] 13 shows the configuration of the output adjustment unit 37 in this case, corresponding to FIG. 3. Here, a control unit 371 that controls the switch 31 and the output unit 14 in accordance with VL (elapsed time) recognized by the waveform measurement unit 32, and a storage unit 372 that stores data (lookup table) required for control are provided.

[0033] 14 shows the time course of the voltage (first output voltage) VL of DC1 recognized by the waveform measurement unit 32 in this power supply circuit 2 when the PRF is large (1) and small (2). Here, the switch 31 is turned off in the initial state (elapsed time = 0). In this case, when the input (power supply) of RF0 begins, VL (the open circuit output voltage in this case) rises from 0. Here, when the PRF is large (1), the rectifying elements of the rectifier circuit 13 may be destroyed if no control is performed, and when the PRF is small (2), there is no risk of such destruction occurring.

[0034] 15 is a flowchart showing the operation of the control unit 371 in this case. Here, the initial state (S31) is the point in time when power supply to RF0 starts with the switch 31 in the off state. Thereafter, as shown in (1) or (2) of FIG. 14, the open-circuit output voltage VL increases with the elapsed time.

[0035] Here, the allowable voltage (maximum open-circuit output voltage) Vlimit of VL is set, and it is determined whether VL has reached Vlimit (S32). As described above, in (1), if VL rises and reaches Vlimt, and then switch 31 continues to be off as indicated by the dashed line, VL becomes excessive, which may damage the rectifying element. Therefore, when VL reaches Vlimt (S32: Yes), control unit 371 turns on switch 31 and determines the elapsed time (rise time) t1 up to this point (S33). At this time, a voltage drop occurs due to the supply of current, so VL falls below Vlimit.

[0036] t1 is small (short rise time) when the PRF is large, and is large (long rise time) when the PRF is small, i.e., t1 can be used in place of the PRF.

[0037] Here, instead of a lookup table corresponding to the relationship between PRF and RLO in the power supply circuit 1, the storage unit 372 stores a lookup table indicating an optimal voltage VLS, which is the optimal (highest conversion efficiency) VL value for each rise time t1. Therefore, the control unit 371 can recognize the VLS corresponding to the recognized t1 (S34). Therefore, as in the first embodiment, the control unit 371 can perform control such that the output current is reduced when VL is smaller than VLS, and the output current is increased when VL is larger than VLS (S35). At this time, the switch 31 is initially turned off, as in the technique described in Patent Document 1, but the switch 31 is continuously turned on after t1.

[0038] On the other hand, in this case, if the PRF is small and VL is small, VL may not reach Vlimit even after sufficient time has passed. Figure 14 (2) illustrates this situation. In this case, a timeout period tTO is set in advance, and it is determined whether the elapsed time has reached tTO (S36). If the elapsed time reaches tTO (S36: Yes), the switch 31 is turned on regardless of the value of VL, and VL at this time is recognized as the limit open-circuit output voltage V0 (S37). As with the technology described in Patent Document 1, if VL is subsequently set to V0 / 2 (S38), the conversion efficiency can be increased. That is, in this case, because the PRF is small, there is no risk of damaging the rectifying element even if the switch 31 is turned off, and the actual operation thereafter is the same as in Patent Document 1.

[0039] In the above operation, the switch 31 is initially turned off only to recognize the rise time t1 or the limit open circuit output voltage V0. At this time, because Vlimit is set, there is no risk of damaging the rectifying elements in the rectifier circuit 13. Furthermore, in the subsequent control of the output current (S35, S38), the switch 31 is turned on, so the time during which the switch 31 is turned off is short. Furthermore, the operation for recognizing t1 or V0 or its start (S31) may be performed appropriately at a timing corresponding to the time constant of fluctuations in RF0 on a long time scale. In this case, the output current control (S35, S38) is controlled so as to increase the output conversion efficiency corresponding to fluctuations in RF0 on a short time scale.

[0040] (Fifth embodiment) As in the fourth embodiment, the rise time of VL in Fig. 14 is used as the control parameter, but it is also possible to configure the rise operation without using a switch. Fig. 16 is a diagram showing the configuration of such a power supply circuit 3 according to the fifth embodiment, corresponding to Fig. 12. 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.

[0041] Instead, the output adjustment unit 38 performs an operation (initial control operation) that minimizes the current of DC2 to be substantially equivalent to not inputting DC1 to the output unit 14. Other operations are similar to those of the power supply circuit 2, and the initial control operation is replaced by an operation (normal control operation) that controls the current value of DC2 according to the rise time (control parameter). In the normal control operation, the current value of DC2 is made larger than in the initial control operation.

[0042] The current value of DC2 (second DC signal minimum setting value IL20) set in the initial control operation is set so as not to be substantially different from the operation of forcibly turning off DC1 input to the output unit 14 in the power supply circuit 2, but need not be zero and may be, for example, 10 mA. Therefore, the time course of VL from the state in which DC2 is set in this way (a state substantially equivalent to when DC1 is turned off) to the state in which RF0 is input (power supply is started) is the same as that shown in FIG. 14. While the voltage VL at the origin (at the start of power supply) in FIG. 14 was zero, in this case the voltage VL at the origin is not strictly zero. However, IL20 is set so that the voltage VL at the origin in this case is negligible in terms of recognizing the change in VL as shown in FIG. 14. Therefore, the operation of the power supply circuit 2 can be performed in the same manner.

[0043] FIG. 17 shows the configuration of the output adjustment unit 38 used in this case, corresponding to FIG. 13. Here, a control unit 381 that controls only the output unit 14 in accordance with VL (elapsed time) recognized by the waveform measurement unit 32, and a memory unit 372 are provided. When IL20=0 in this power supply circuit 3, the operation of this power supply circuit 3 is essentially the same as the operation of the power supply circuit 2. However, in the power supply circuit 2, the timing of turning on and off the switch 31 can be controlled with higher precision than the timing control by the output adjustment unit to control the current of DC2 in this case. On the other hand, although the precision of this timing control in this power supply circuit 3 is lower than that of the power supply circuit 2, similar control can be performed without using the switch 31, allowing this power supply circuit 3 to be inexpensive.

[0044] In this case, the lookup table stored in storage unit 372 can be the same as that used in power supply device 2, if the characteristics shown in Fig. 14 are substantially the same as those in power supply device 2. Alternatively, if the characteristics shown in Fig. 14 change due to the provision of IL20 (≠0), a lookup table using newly optimized parameters in accordance with this change can be used.

[0045] Fig. 18 is a flowchart showing the operation of the control unit 381 in this case. Here, compared to the flowchart of Fig. 15, the difference is that in the initial state, instead of the switch 31 being turned off (S31), the output current is minimized (initial control operation) (S31A), and thereafter, instead of the switch being turned on (S33, S37), the initial control operation is switched to normal control operation (S33A, S37A), but the other operations are the same as those of Fig. 15. The same is true for setting Vlimit, etc.

[0046] In addition to the above examples, any quantity that can be recognized from the rectified DC signal and used to control the power conversion efficiency can be used as the control parameter. The contents of the look-up table stored in the storage unit can be set appropriately accordingly. In addition, in the above example, RLO (FIG. 2) and VLO (FIG. 6) were set as points at which the conversion efficiency η was maximized, but these do not necessarily correspond to the maximum value of the conversion efficiency η, and may be points at which a desired conversion efficiency η is obtained.

[0047] It is clear that the present invention is not limited to the above-described embodiments, and that the embodiments can be modified as appropriate within the scope of the technical concept of the present invention. [Explanation of symbols]

[0048] 1, 2, 3 power circuit 11 Antenna 12 Matching circuit 13 Rectifier circuit 14 Output section 15 RF input monitor circuit 16 DC input monitor circuit 17, 27, 28, 37, 38 Output adjustment section 31 Switch 32 Waveform measurement section 81A~81D FET 82 Inductor 83 Capacitor 84 Resistance 85 Switching control section 100 Battery (storage battery: load) 141 DC-DC converter 142 Output conversion circuit 171, 271, 281, 371, 381 Control unit 172 Division circuit 173, 272, 282, 372 storage section

Claims

1. A power supply circuit that outputs a DC signal generated based on a received high-frequency signal to a load, a rectifier circuit that rectifies the high-frequency signal and outputs a first DC signal; an output unit that converts the first DC signal using a DC-DC converter into a second DC signal and outputs the second DC signal as the DC signal; an output adjustment unit that recognizes a control parameter that is recognized according to an output state of the first DC signal, and controls an increase or decrease in the current of the second DC signal that is output from the output unit according to the control parameter so as to increase the efficiency of power conversion from the high frequency signal to the DC signal; A power supply circuit comprising:

2. the control parameter is a load resistance when looking from the rectifier circuit to the load side via the output unit, a storage unit that stores a lookup table indicating a relationship between an optimum load resistance value that is the load resistance that increases the power conversion efficiency and a high frequency power that is the power of the high frequency signal; The output adjustment unit recognizes the current high-frequency power and the load resistance, and based on the look-up table, increasing the current of the second DC signal when the load resistance is higher than the optimum load resistance corresponding to the recognized high frequency power; 2. The power supply circuit according to claim 1, wherein the output section is controlled so as to reduce the current of the second DC signal when the load resistance is lower than the optimal load resistance corresponding to the recognized high-frequency power.

3. the control parameter is a first output voltage that is a voltage of the first DC signal when the DC signal is supplied to the load side via the output unit, a storage unit that stores a lookup table indicating a relationship between a value of an optimum voltage that is the first output voltage that increases the power conversion efficiency and a high frequency power that is the power of the high frequency signal; The output adjustment unit recognizes the current high-frequency power and the first output voltage, and adjusts the current high-frequency power and the first output voltage based on the look-up table. increasing the current of the second DC signal when the first output voltage is higher than the optimum voltage corresponding to the recognized high frequency power; 2. The power supply circuit according to claim 1, wherein the output section is controlled so as to reduce the current of the second DC signal when the first output voltage is lower than the optimal voltage corresponding to the recognized high frequency power.

4. the control parameter is a first output current that is a current of the first DC signal when the DC signal is supplied to the load side via the output unit, a storage unit that stores a lookup table indicating a relationship between a value of an optimal current that is the first output current that increases the power conversion efficiency and a high-frequency power that is the power of the high-frequency signal; The output adjustment unit recognizes the current high-frequency power and the first output current, and determines, based on the look-up table, reducing the current of the second DC signal when the first output current is higher than the optimum current corresponding to the recognized high frequency power; 2. The power supply circuit according to claim 1, wherein the output section is controlled so as to increase the current of the second DC signal when the first output current is lower than the optimal current corresponding to the recognized high-frequency power.

5. a switch for controlling on / off of the first DC signal between the rectifier circuit and the output section; a first output voltage, which is the voltage of the first DC signal output from the rectifier circuit, is recognized; a maximum open-circuit output voltage is set, which is a maximum value for an open-circuit output voltage that is a voltage of the first DC signal when the switch is off; the control parameter is a rise time from when the high-frequency signal is supplied to when the switch is turned off until the open-circuit output voltage reaches the maximum open-circuit output voltage, a storage unit that stores a look-up table indicating a relationship between an optimum voltage value, which is the first output voltage that increases the power conversion efficiency when the switch is turned on, and the rise time; The output adjustment unit recognizes the rise time and the current first output voltage, and determines, based on the look-up table, increasing the current of the second DC signal when the first output voltage is higher than the optimum voltage corresponding to the recognized rise time; 2. The power supply circuit according to claim 1, wherein the output section is controlled so as to reduce the current of the second DC signal when the first output voltage is lower than the optimal voltage corresponding to the recognized rise time.

6. a first output voltage, which is the voltage of the first DC signal output from the rectifier circuit, is recognized; the output adjusting unit is configured to switch between two types of operations: a normal control operation for controlling an increase or decrease in the current of the second DC signal in accordance with the recognized control parameter, and an initial control operation for controlling the current of the second DC signal to a constant value smaller than a value in the normal control operation regardless of the control parameter; a maximum open-circuit output voltage that is a maximum value for an open-circuit output voltage that is a voltage of the first DC signal during the initial control operation is set; the control parameter is a rise time from when the high-frequency signal is supplied until when the open-circuit output voltage reaches the maximum open-circuit output voltage when the initial control operation is performed, a storage unit that stores a look-up table indicating a relationship between an optimum voltage value, which is the first output voltage that increases the power conversion efficiency when the normal control operation is performed, and the rise time; When performing the normal control operation, the output adjustment unit recognizes the rise time and the current first output voltage, and determines, based on the look-up table, increasing the current of the second DC signal when the first output voltage is higher than the optimum voltage corresponding to the recognized rise time; 2. The power supply circuit according to claim 1, wherein the output section is controlled so as to reduce the current of the second DC signal when the first output voltage is lower than the optimal voltage corresponding to the recognized rise time.

7. 7. The power supply circuit according to claim 1, wherein the load is a storage battery, and the DC signal is used as a charging current.

Images