JP4609414B2 - Vehicle power generation control device - Google Patents

Description

  The present invention relates to a vehicular power generation control device that changes an adjustment voltage of a vehicular generator based on a signal sent from an external control device.

  Conventionally, a vehicular generator in which only an output terminal for taking out an output current is exposed to the outside is known (for example, refer to Patent Documents 1 to 3). Generally, in a vehicular generator, a minute AC voltage is generated in the armature winding only by rotating the rotor without applying an exciting current to the field winding. This is due to the magnetization remaining in the field pole constituting the rotor. In the vehicle power generation control device provided in the above-described vehicle generator, the minute voltage induced in the armature winding is detected to activate the power supply circuit, and the switching element is intermittently controlled to control the excitation current. Thus, the output voltage is adjusted.

In recent years, in order to respond to the environment, improvements have been made to improve fuel efficiency. For example, in a vehicular generator, a terminal for inputting a command signal sent from an external control device is provided, and when the vehicle is accelerated, the adjustment voltage is reduced to suppress power generation, and when the vehicle is decelerated, the adjustment voltage is increased to increase the regenerative power. For example, an improvement method for reducing the load on the engine by power generation by changing the adjustment voltage from the outside is considered.
Japanese Patent Laid-Open No. 6-276696 (page 3-5, FIG. 1-6) JP-A-6-284598 (page 3-5, FIG. 1-3) JP 2002-125398 A (page 5-6, FIG. 1-7)

  By the way, in order to capture the signal sent from the external control device into the vehicle power generation control device provided in the vehicle power generator having only the output terminal as disclosed in Patent Documents 1 to 3, the vehicle power generator There are many structural changes because it is necessary to add an input terminal for connecting the signal line to the vehicle power generation control device and to add a structure around the input terminal such as a connector, etc. There was a problem that the cost would increase significantly. In addition, when a structure using a connector is used and an opening is provided in the rear cover, foreign objects such as metal pieces and mud enter through the opening, and water and oil enter the environment, resulting in environmental resistance. There was a problem of lowering. In order to improve the environmental resistance and ensure reliability, it is necessary to have a special structure to prevent the intrusion of foreign matter and water, etc., and it is also necessary to ensure the waterproofness of the mating part of the connector As a result, the cost further increases.

  The present invention has been created in view of the above points, and an object of the present invention is to add a function of changing the adjustment voltage, and to suppress an increase in cost and prevent a decrease in environmental resistance. An object of the present invention is to provide a vehicular power generation control device.

  In order to solve the above-described problem, the vehicle power generation control device of the present invention changes the adjustment voltage of the vehicle generator based on a signal sent from the external control device, and outputs the output of the vehicle generator. The adjustment voltage control means for adjusting the terminal voltage to match the adjustment voltage, the frequency of the signal superimposed on the voltage of the output terminal of the vehicle generator is compared with a predetermined frequency, and the frequency of the superimposed signal Adjustment voltage changing means for changing the adjustment voltage from the first value to the second value when the frequency is higher than a predetermined frequency. In this way, the output terminal of the vehicular generator is used, a signal is superimposed on the output terminal from the external control device, and the adjustment voltage is changed when the signal is detected on the vehicular generator side. This eliminates the need to add a structure for inputting signals using a connector or to provide an opening in the rear cover of a vehicular generator, etc., so there is no need to add or change the structure, minimizing cost increases. In addition, it is possible to add a function of changing the adjustment voltage while maintaining the same environmental resistance performance as before.

  The adjustment voltage changing unit described above preferably includes a high-frequency passage unit that allows a high-frequency signal superimposed on the voltage of the output terminal to pass therethrough. Thereby, the high frequency signal sent from the external control device can be detected regardless of the magnitude of the direct current component of the output voltage of the vehicular generator. Specifically, the high-frequency signal outputs the output voltage that changes from the transient state to the steady state when the adjustment voltage is changed, or the output voltage that changes transiently when the electrical load is turned on and off. Since it is superimposed following the voltage, the signal sent from the external control device can be accurately taken in by passing only the component of the high-frequency signal by the high-frequency passage means.

  Further, the adjustment voltage changing means described above has a frequency discriminating means for comparing the frequency of the signal output from the high frequency passing means with a predetermined frequency, and the predetermined frequency is an electric noise generated by the vehicle generator itself. It is desirable that the frequency be set higher than the frequency generated by the voltage oscillation. As a result, the frequency of the high-frequency signal used for changing the adjustment voltage is set higher than the predetermined frequency, and the predetermined frequency is set higher than the frequency of the voltage vibration of the electric noise generated by the vehicle generator itself. By doing so, it is possible to prevent malfunction due to electric noise generated by the vehicle generator itself.

  Further, it is desirable that the first value described above is set to a voltage for normally charging the battery, and the second value is set to a charging voltage lower than the first value. As a result, it is possible to reduce the engine load by reducing the adjustment voltage during vehicle acceleration to suppress power generation.

  Moreover, it is desirable that the adjustment voltage changing unit described above includes a band-pass unit that passes a high-frequency signal superimposed on the voltage of the output terminal. Thereby, the high frequency signal sent from the external control device can be detected regardless of the magnitude of the direct current component of the output voltage of the vehicular generator. Specifically, the high-frequency signal outputs the output voltage that changes from the transient state to the steady state when the adjustment voltage is changed, or the output voltage that changes transiently when the electrical load is turned on and off. Since it is superposed following the voltage, the signal transmitted from the external control device can be accurately taken in by passing only the component of the high-frequency signal by the band-pass means.

  Further, the adjustment voltage changing means described above has a frequency discrimination means for comparing the frequency of the signal output from the band-pass means with a predetermined frequency, and the predetermined frequency is an electric noise generated by the vehicle generator itself. It is desirable that the frequency be set higher than the frequency generated by the voltage oscillation. As a result, the frequency of the high-frequency signal used for changing the adjustment voltage is set higher than the predetermined frequency, and the predetermined frequency is set higher than the frequency of the voltage vibration of the electric noise generated by the vehicle generator itself. By doing so, it is possible to prevent malfunction due to electric noise generated by the vehicle generator itself.

  In addition, it is desirable that the above-described band passing means removes signals in a predetermined frequency band or higher than a predetermined frequency. Thereby, the frequency component more than the high frequency signal for changing the adjustment voltage of the generator for vehicles can be removed, and the malfunction by the noise from the apparatus connected to the communication line, or induction noise can be prevented.

  Further, it is desirable that the first value described above is set to a voltage for normally charging the battery, and the second value is set to a charging voltage different from the first value. As a result, the adjustment voltage can be lowered during vehicle acceleration to suppress power generation and the engine load can be reduced, or the adjustment voltage can be raised during vehicle deceleration to accumulate regenerative power in the battery.

  The frequency discriminating means described above has a first frequency discriminating circuit for discriminating the first predetermined frequency and a second frequency discriminating circuit for discriminating the second predetermined frequency, and the high frequency signal is the first frequency discriminating circuit. A plurality of second values are set when the frequency is between the predetermined frequency and the second predetermined frequency and when the high-frequency signal is equal to or higher than the second predetermined frequency, and one is set to a charging voltage lower than the first value. It is desirable that the other is set to a charging voltage higher than the first value. As a result, a plurality of high-frequency signals can be allocated, and the engine voltage is reduced by lowering the adjustment voltage during vehicle acceleration to suppress power generation, and the regenerative power is increased by increasing the adjustment voltage during vehicle deceleration. Can accumulate.

  Hereinafter, a vehicle power generation control device according to an embodiment to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a vehicular generator in which a vehicular power generation control device according to an embodiment is built, and a connection state between the vehicular generator and a battery or an external control device is also shown. Yes.

  As shown in FIG. 1, the vehicular generator 1 includes an excitation winding 11, an armature winding 12, a rectifier 13, a capacitor 14, and a vehicular power generation control device 2. The exciting winding 11 is wound around a field pole (not shown) to form a rotor, and is energized to generate a field. The armature winding 12 is a multiphase winding (for example, a three-phase winding) and is wound around an armature core to constitute an armature. The armature winding 12 generates an electromotive force due to a change in the magnetic field generated by the excitation winding 11. An AC output induced in the armature winding 12 is supplied to the rectifier 13. The rectifier 13 performs full-wave rectification on the AC output of the armature winding 12. The output of the rectifier 13 is taken out as the output of the vehicle generator 1 and supplied to the battery 3 and an electric load (not shown). The capacitor 14 is provided between the output terminal (hereinafter referred to as “B terminal”) and the E terminal (ground terminal) of the vehicle generator 1 in order to suppress electrical noise included in the output of the vehicle generator 1. Connected. The output of the vehicular generator 1 changes in accordance with the number of rotations of the rotor and the energization amount of the excitation current flowing through the excitation winding 11, and this excitation current is controlled by the vehicular power generation control device 2.

  The vehicle power generation control device 2 includes a power supply starting circuit 21, a power supply circuit 22, an adjustment voltage control circuit 23, a switch element 24, a freewheeling diode 25, and an adjustment voltage changing circuit 26. The power start circuit 21 receives the phase voltage of the armature winding 12. The power supply circuit 22 is activated by a signal output from the power supply activation circuit 21 and supplies an operating voltage to each circuit in the vehicle power generation control device 2. The adjustment voltage control circuit 23 is an adjustment voltage control means, and is connected to the B terminal of the vehicular generator 1 and generates a control signal for controlling the on / off operation of the switch element 24 (details will be described later).

  The switch element 24 is configured using a power transistor, the base is connected to the output terminal of the adjustment voltage control circuit 23, the collector is connected to the B terminal of the vehicle generator 1 via the freewheeling diode 25, and the emitter Is grounded. The excitation winding 11 is connected to the collector of the switch element 24. When the switch element 24 is turned on, an excitation current flows through the excitation winding 11, and when the switch element 24 is turned off, the current is stopped. The freewheeling diode 25 is connected in parallel with the exciting winding 11 and recirculates the current flowing through the exciting winding 11 when the switch element 24 is turned off.

  The adjustment voltage changing circuit 26 is an adjustment voltage changing means, and is connected to the B terminal of the vehicle generator 1. In order to change the adjustment voltage, a positive input terminal of the voltage comparator 231 in the adjustment voltage control circuit 23. (Details will be described later). The adjustment voltage control circuit 23 includes a voltage comparator 231, resistors 232, 233, 234, and 235 and a capacitor 236. A reference voltage V1 corresponding to an adjustment voltage (for example, 14V), which is a voltage obtained by dividing the operating voltage Vcc generated by the power supply circuit 22 with resistors 232 and 233, is applied to the positive input terminal of the voltage comparator 231. The A voltage V2 obtained by dividing the B terminal voltage by resistors 234 and 235 to detect the B terminal voltage of the vehicle generator 1 is applied to the negative input terminal of the voltage comparator 231. The capacitor 236 is connected to the negative input terminal of the voltage comparator 231, removes noise included in the B terminal voltage, and stabilizes the on / off control of the switch element 24.

The adjustment voltage changing circuit 26 includes a high-frequency pass filter (HPF) 261, a frequency discrimination circuit 262, a transistor 263, and a resistor 264. The high-frequency pass filter 261 is a CR filter as a high-frequency pass means composed of, for example, a capacitor and a resistor, is connected to the B terminal, and passes a high-frequency signal superimposed on the B terminal voltage. The frequency discriminating circuit 262 is a frequency discriminating unit and compares the frequency (input frequency) of the signal that has passed through the high-frequency pass filter 261 with a predetermined frequency f _A. When the input frequency is lower than the predetermined frequency f _A , a low level signal is output. Conversely, when the input frequency is higher than the predetermined frequency f _A , a high level signal is output. The base of the transistor 263 is connected to the output terminal of the frequency discriminating circuit 262, the collector is connected to the plus input terminal of the voltage comparator 231 via the resistor 264, and the emitter is grounded.

  As shown in FIG. 1, the external control device 4 includes a signal output circuit 41 and a switch element 42. The signal output circuit 41 has an output terminal connected to the B terminal in order to superimpose a high-frequency signal on the B terminal voltage of the vehicle generator 1. The switch element 42 is for controlling whether or not a high-frequency signal is output by the signal output circuit 41. For example, a high frequency signal is output from the signal output circuit 41 when the switch element 42 is turned on, and the output of the high frequency signal from the signal output circuit 41 is stopped when the switch element 42 is turned off.

  The vehicle generator 1 of this embodiment has such a configuration, and the operation thereof will be described next. When the engine rotates, the magnetizing force remaining in the field pole (not shown) constituting the rotor of the vehicular generator 1 acts on the armature winding 12, so that no exciting current flows through the exciting winding 11. Also, a minute voltage is generated in the armature winding 12. The power supply starting circuit 21 detects this minute voltage and puts the power supply circuit 22 into an operating state. In the voltage comparator 231 of the adjustment voltage control circuit 23, when the input voltage V2 is lower than the reference voltage V1, the output becomes high level. Accordingly, the switch element 24 is turned on, and the exciting current is supplied to the exciting winding 11. By supplying the excitation current, the magnetizing force of the field pole is increased and the voltage generated in the armature winding 12 is increased. When the generated voltage further rises and the input voltage V2 linked to the B terminal voltage of the vehicular generator 1 reaches the reference voltage V1 (voltage corresponding to the adjustment voltage 14V), the output of the voltage comparator 231 changes to a low level. . Therefore, the switch element 24 is turned off, and the excitation current is reduced. Such control is repeated, and the B terminal voltage of the vehicular generator 1 is adjusted to a predetermined adjustment voltage (first value, for example, 14 V).

  Next, the operation when the adjustment voltage is changed by the external control device 4 will be described. While the switch element 42 in the external control device 4 is on, the signal output circuit 41 generates a high-frequency signal (for example, an oscillation signal having a frequency of 5 MHz and a peak-to-peak amplitude of 200 mV) as a B terminal voltage of the vehicle generator 1. Superimpose. The frequency of the high-frequency signal is superimposed on the B terminal voltage when the switch element 24 is turned on and off in the excitation circuit composed of the excitation winding 11 and the freewheeling diode 25 and the switch element 24 connected in parallel thereto. The frequency is set higher than the switching noise. The frequency of the high-frequency signal is set to a frequency higher than the commutation noise that is synchronized with the rotational speed of the vehicular generator 1 that is generated when the rectification operation is performed by the rectifier 13. The frequency of the high-frequency signal is set in this way because the magnitude of the switching noise and commutation noise is the capacitor 14 connected between the B terminal and the E terminal (in order to prevent noise disturbance of the in-vehicle device). Used), and is damped while vibrating over time (specifically, a voltage oscillation that attenuates about several tens of kHz to several hundreds of kHz). This is to prevent the adjustment voltage changing circuit 26 from malfunctioning due to voltage vibration of electrical noise.

When a high-frequency signal superimposed on the B terminal voltage of the vehicle generator 1 is input to the adjustment voltage changing circuit 26, only a high-frequency component corresponding to the high-frequency signal is passed by the high-frequency pass filter 261. The signal that has passed through the high-frequency pass filter 261 is compared with a predetermined frequency f _A (for example, 1 MHz) by the frequency discrimination circuit 262. The predetermined frequency f _A is set to a frequency higher than the voltage vibration of the electric noise generated by the vehicle generator 1 itself. Therefore, the vehicle generator 1 does not respond to the voltage vibration of the electric noise generated by itself. Since the high frequency signal (5 MHz) sent from the external control device 4 is higher than the predetermined frequency f _A , a high level signal is output from the frequency discrimination circuit 262 and the transistor 263 is turned on. Thereby, since the resistor 233 and the resistor 264 are connected in parallel, the reference voltage is changed to V1 ′ (voltage lower than the reference voltage V1 divided by the resistors 232 and 233), and the adjustment voltage is changed from 14V. It is changed to a lower voltage (second value), for example 12.5V. Therefore, the B terminal voltage of the vehicular generator 1 is adjusted to match the low adjustment voltage. When the transmission of the high frequency signal from the external control device 4 is stopped, the B terminal voltage of the vehicular generator 1 returns to a predetermined adjustment voltage (14V).

In this way, the high-frequency signal is transmitted from the external control device 4 and superimposed on the B terminal voltage, and the frequency of the signal superimposed with this high-frequency signal is compared with the predetermined frequency f _A to adjust the vehicle generator 1. The voltage can be changed. This eliminates the need to add a structure for inputting a signal using a connector or to provide an opening in the rear cover or the like of the vehicular generator 1, thereby minimizing the increase in cost because there is no need to add or change the structure. It is possible to add a function of changing the adjustment voltage while maintaining the same environmental resistance as before.

  Further, since the adjustment voltage changing circuit 26 includes a high-frequency pass filter 261 that allows a high-frequency signal superimposed on the B terminal voltage to pass therethrough, an external control is performed regardless of the magnitude of the DC component of the output voltage of the vehicle generator 1. A high-frequency signal sent from the device 4 can be detected. Specifically, the high-frequency signal outputs the output voltage that changes from the transient state to the steady state when the adjustment voltage is changed, or the output voltage that changes transiently when the electrical load is turned on and off. Since the voltage is superimposed following the voltage, the signal transmitted from the external control device 4 can be accurately taken in by passing only the component of the high-frequency signal using the high-frequency pass filter 261.

In addition, the frequency of the high-frequency signal used for changing the adjustment voltage is set to be higher than the predetermined frequency f _A , and this predetermined frequency is set to be higher than the frequency of the voltage fluctuation of the electric noise generated by the vehicle generator 1 itself. By setting it high, it is possible to prevent malfunction due to electric noise generated by the vehicle generator 1 itself.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. In the embodiment described above, the case where the normal adjustment voltage (14V) is changed to the low adjustment voltage (12.5V) has been described, but conversely, the adjustment voltage may be changed to a higher adjustment voltage. For example, as shown in FIG. 2, when the output terminal of the adjustment voltage changing circuit 26A (one end of the resistor 264) is connected to the negative input terminal of the voltage comparator 231, and a high frequency signal is sent from the external control device 4 The transistor 263 is turned on to connect the resistor 235 and the resistor 264 in parallel. In this case, since the voltage appearing at the connection point between the resistor 235 and the resistor 264 is lower than the voltage detected at these connection points using only the resistor 234 and the resistor 235, a high adjustment voltage (for example, 16V) It becomes possible to change to.

  When such a high adjustment voltage is set, overcharge of the battery 3 is a concern, and as shown in FIG. 2, the adjustment voltage changing circuit 26A includes a high-frequency pass filter included in the adjustment voltage changing circuit 26 of FIG. 261 is changed to a band pass filter (BPF) 261A. In recent years, devices using high-frequency (for example, millimeter wave) technology have been installed to detect obstacles around the vehicle and improve safety, in order to avoid malfunctions due to high-frequency signals emitted by such devices. In addition, it is desirable to remove such unnecessary high-frequency signals at the input stage in advance.

  FIG. 3 is a diagram illustrating another modification of the vehicle power generation control device. The vehicle power generation control device 2B shown in FIG. 3 includes a power supply starting circuit 21, a power supply circuit 22, an adjustment voltage control circuit 23, a switch element 24, a freewheeling diode 25, and an adjustment voltage changing circuit 26B. The adjustment voltage changing circuit 26B is an adjustment voltage changing means, and is connected to both the positive input terminal and the negative input terminal of the voltage comparator 231 in the adjustment voltage control circuit 23 in order to change the adjustment voltage. The adjustment voltage changing circuit 26B includes a band-pass filter (BPF) 261A, a frequency discriminating circuit 262A, transistors 263a and 263b, resistors 264a and 264b, AND circuits 265 and 266, and an inverter circuit 267.

The frequency discriminating circuit 262A is frequency discriminating means, and the frequency (input frequency) of the signal that has passed through the band-pass filter 261A, the first predetermined frequency f _A and the second predetermined frequency f _B (f _A <f _B ). And compare. The comparison between the input frequency and the first predetermined frequency f _A is performed by the first frequency discriminating circuit 262a. When the input frequency is lower than the first predetermined frequency f _A , a low level signal is output. On the other hand, when the frequency is higher than the first predetermined frequency f _A , a high level signal is output. The comparison between the input frequency and the second predetermined frequency f _B is performed by the second frequency discriminating circuit 262b. When the input frequency is lower than the second predetermined frequency f _B , a low level signal is output. On the other hand, when the frequency is higher than the second predetermined frequency f _B , a high level signal is output.

The AND circuit 265 has one input terminal connected to the output terminal of the first frequency discrimination circuit 262a, and the other input terminal connected to the output terminal of the second frequency discrimination circuit 262b via the inverter circuit 267. . Therefore, when the input frequency is between the first predetermined frequency f _A and the second predetermined frequency f _B , the output of the AND circuit 265 becomes high level and the transistor 263a is turned on. As a result, the resistor 264a is connected in parallel to the resistor 233 in the adjustment voltage control circuit 23, and the adjustment voltage is changed to a low value.

The AND circuit 266 has one input terminal connected to the output terminal of the first frequency discrimination circuit 262a and the other input terminal connected to the output terminal of the second frequency discrimination circuit 262b. Therefore, when the input frequency is equal to or higher than the second predetermined frequency f _B , the output of the AND circuit 266 becomes high level and the transistor 263b is turned on. Accordingly, the resistor 264b is connected in parallel to the resistor 235 in the adjustment voltage control circuit 23, and the adjustment voltage is changed to a high value.

As described above, the vehicle power generation control device 2B shown in FIG. 3 can set two types of adjustment voltages, for example, when the vehicle is accelerated, the frequency of the input signal is set to the first predetermined frequency f _A and the first adjustment frequency f _A. 2 is set between two predetermined frequencies f _B to reduce the engine load by suppressing the power generation by lowering the adjustment voltage, and the frequency of the input signal is set to be equal to or higher than the second predetermined frequency f _B when the vehicle is decelerated. Thus, the regenerative power can be stored in the battery 3 by increasing the adjustment voltage.

It is a figure which shows the structure of the generator for vehicles with which the power generation control apparatus for vehicles of one Embodiment was incorporated. It is a figure which shows the structure of the generator for vehicles with which the vehicle power generation control apparatus of the modification was incorporated. It is a figure which shows the other modification of the electric power generation control apparatus for vehicles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle generator 2, 2A, 2B Vehicle power generation control device 3 Battery 4 External control device 11 Excitation winding 12 Armature winding 13 Rectifier 14 Capacitor 21 Power supply starting circuit 22 Power supply circuit 23 Adjustment voltage control circuit 24, 42 Switch Element 25 Freewheeling diode 26, 26A, 26B Adjustment voltage changing circuit 41 Signal output circuit

Claims (9)

In the vehicle power generation control device that changes the adjustment voltage of the vehicle generator based on the signal sent from the external control device,
Adjustment voltage control means for adjusting the voltage of the output terminal of the vehicle generator to match the adjustment voltage;
The frequency of the signal superimposed on the voltage of the output terminal of the vehicle generator is compared with a predetermined frequency, and when the frequency of the superimposed signal is higher than the predetermined frequency, the adjustment voltage is set to a first value. Adjusting voltage changing means for changing from 1 to the second value;
A vehicle power generation control device comprising: In claim 1,
The vehicular power generation control device, wherein the adjustment voltage changing unit includes a high-frequency passage unit that allows a high-frequency signal superimposed on the voltage of the output terminal to pass therethrough. In claim 2,
The adjustment voltage changing means includes frequency discrimination means for comparing the frequency of the signal output from the high-frequency passage means with the predetermined frequency,
The vehicle power generation control device, wherein the predetermined frequency is set to be higher than a frequency generated by voltage oscillation of electrical noise generated by the vehicle generator itself. In claim 3,
The first value is set to a voltage that normally charges the battery;
The vehicle power generation control device, wherein the second value is set to a charging voltage lower than the first value. In claim 1,
The power generation control device for a vehicle according to claim 1, wherein the adjustment voltage changing means includes band passing means for passing a high frequency signal superimposed on the voltage of the output terminal. In claim 5,
The adjustment voltage changing unit includes a frequency determining unit that compares the frequency of the signal output from the band-pass unit with the predetermined frequency;
The vehicle power generation control device, wherein the predetermined frequency is set to be higher than a frequency generated by voltage oscillation of electrical noise generated by the vehicle generator itself. In claim 6,
The vehicle power generation control device according to claim 1, wherein the band passing means removes a signal having a predetermined frequency band or higher than the predetermined frequency. In claim 7,
The first value is set to a voltage that normally charges the battery;
The power generation control device for a vehicle, wherein the second value is set to a charging voltage different from the first value. In claim 8,
The frequency discriminating unit includes a first frequency discriminating circuit that discriminates a first predetermined frequency, and a second frequency discriminating circuit that discriminates a second predetermined frequency,
When the high-frequency signal is between the first predetermined frequency and the second predetermined frequency, and when the high-frequency signal is equal to or higher than the second predetermined frequency, a plurality of the second values are set, One of these is set to a charging voltage lower than the first value, and the other is set to a charging voltage higher than the first value.

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