JP2005086937A - Power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply circuit which copes with all used areas and which has low power consumption and little influence on broadcasting receivers. <P>SOLUTION: The power supply circuit includes a switching duty decision/frequency switching deciding circuit 4a, which sets the switching frequency Fs of switching elements Q1, Q2, Q3 and Q4 to 45 [KHz] which is 1/2 of the fundamental frequency 90 [KHz], and outputs the frequency so that the carrier frequency interval for an AM radio broadcasting can be, for example, used in the area of 9 [kHz] as in Japan, if destination information informed from an ECU 5 through a transmitting circuit 4c is not "U.S.A". Also, if the destination information is for U.S.A., the switching duty decision/frequency switching deciding circuit 4a sets the switching frequency Fs of the switching elements Q1, Q2, Q3 and Q4 to 30 [kHz] which is 1/3 of the fundamental frequency 90 [KHz], and outputs the frequency, so that the AM radio broadcasting can be utilized in U.S.A., where the carrier frequency interval is 10 [kHz]. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply circuit mounted on a vehicle device or the like.

  Conventionally, a DC / DC converter is a part of a vehicle power supply circuit for converting the voltage of a direct current power supply, and is driven by a combination of an electric vehicle (EV: Electric Vehicles) that is driven by a motor or an engine and a motor. It is widely used in vehicle devices that drive using a motor, such as hybrid electric vehicles (HEV). In such a DC / DC converter, the switching frequency of the switching elements constituting the DC / DC converter is set to AM so that noise is generated in the AM radio broadcast receiver mounted on the vehicle and the passenger does not feel uncomfortable. It is set to an integer multiple of the carrier frequency interval for radio broadcasting. Specifically, both in the region where the carrier frequency interval for AM radio broadcasting is 10 [KHz], such as the United States, and in the region where the carrier frequency interval for AM radio broadcasting is 9 [KHz], as in Japan. The switching frequency is set to 90 [KHz], which is the least common multiple of both carrier frequency intervals so that it can be used.

On the other hand, electric vehicles (EV) and hybrid vehicles (HEV) are attracting attention as environmental protection measures, and travel using motors that run on high-voltage electricity to realize a low-pollution and energy-efficient transportation system. It is a vehicle developed for the purpose of doing so, and further improvement in energy efficiency (fuel consumption) is required. Therefore, it has been proposed to reduce the power consumed by the DC / DC converter by lowering the switching frequency of the switching elements constituting the DC / DC converter. As a technique for continuously changing the switching frequency of the switching elements constituting the DC / DC converter, a technique such as the power supply device described in Patent Document 1 is known (see, for example, Patent Document 1). .)
JP 2001-320876 A

By the way, the current switching frequency is set to 90 [KHz] which is the least common multiple of the carrier frequency intervals for AM radio broadcasting in a plurality of regions. However, in order to reduce the power consumed by the DC / DC converter. In order to reduce the switching frequency, two methods are conceivable.
The first method is a method of setting a frequency lower than 90 [KHz], which is a common multiple of AM radio broadcast carrier frequency intervals for each region. However, in this case, the vehicle has to be manufactured individually for each region where the vehicle is used, and there is a problem that the production efficiency is deteriorated and the cost of the vehicle itself is increased.

  The second method is a method of switching the switching frequency for each region used. However, even in this case, it is necessary to respond with good responsiveness to the carrier frequency intervals for AM radio broadcasts in a plurality of areas where the vehicle is used without deteriorating the production efficiency or increasing the cost of the vehicle itself. Furthermore, when switching the frequency, if the frequency is continuously changed as in the prior art, harmonics of the switching frequency are generated in the AM radio broadcast band, and noise is output to the AM radio broadcast receiver output. For example, there is a problem that the merchantability of the vehicle is lowered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a power supply circuit that can be applied to all regions to be used, has low power consumption, and has little influence on a broadcast receiver.

  In order to solve the above-described problem, a power supply circuit according to the invention of claim 1 includes a power storage device (for example, a high voltage battery B1 in an embodiment described later) and a load (for example, described later) by converting the voltage of the power storage device. Destination information defining a region to be used in a power supply circuit including a voltage converter (for example, a DC / DC converter 1 of the embodiment described later) that supplies the low-voltage battery B2 and the electrical load 6) of the embodiment. And a frequency setting means for setting a switching frequency of the switching elements constituting the voltage converter (for example, a control unit 4 of an embodiment to be described later).

  The power supply circuit having the above configuration is different for each region by the frequency setting means setting the switching frequency of the switching element constituting the voltage converter based on the destination information defining the region to be used. The voltage converter can be operated at a switching frequency corresponding to the broadcast carrier frequency interval.

  A power supply circuit according to a second aspect of the present invention is the power supply circuit according to the first aspect, wherein the switching frequency is set to the least common multiple of the broadcast carrier frequency intervals of all the regions used, and the destination It is characterized in that it is set to 1 / integer of the base frequency specified by one in common with the ground information.

  The power supply circuit having the above configuration sets, for example, one base frequency commonly specified in the destination information to the least common multiple of the broadcast carrier frequency intervals of all the regions used, and By setting the frequency of 1 / integer as the switching frequency, the switching frequency of the voltage converter can easily correspond to the broadcast carrier frequency interval in any region.

  A power supply circuit according to a third aspect of the present invention is the power supply circuit according to the first or second aspect, wherein when the frequency setting means sets the switching frequency, the power supply circuit is arbitrarily selected from the base frequency. The frequency is directly changed to a frequency corresponding to the ground information.

  In the power supply circuit having the above configuration, when the frequency setting unit changes the switching frequency from the base frequency to a frequency corresponding to any destination information, by directly changing the frequency without continuously changing, It is possible to prevent the harmonics of the switching frequency from being generated in the broadcast band.

  A power supply circuit according to a fourth aspect of the present invention is the power supply circuit according to any one of the first to third aspects, wherein the destination information is acquired from an external control means (for example, an ECU 5 in an embodiment described later). Communication means (for example, a communication circuit 4c in an embodiment described later) and current detection means (for example, a current sensor 2 in an embodiment described later) for detecting a current flowing through the load, and between the control means The switching frequency is set to the base frequency when an abnormal communication occurs or when the amount of current flowing through the load is a predetermined value or more.

  In the power supply circuit having the above configuration, when the frequency setting means has some problem in communication with the external control means for acquiring destination information, or the amount of current flowing through the load of the voltage converter Even if the current value is within the normal range but cannot be operated with the switching frequency of the voltage converter lowered, for example, the current value that saturates the transformer provided in the voltage converter, the switching frequency By setting to the base frequency, the operation of the voltage converter can be continued. Specifically, for example, at a switching frequency of 30 [KHz], the transformer saturates when the amount of current flowing through the load is 30 to 40 [A], but at a switching frequency of 90 [KHz], which is the base frequency, 120 [A]. The amount of current flowing through the load can be allowed.

According to the power supply circuit of claim 1, the voltage converter can be operated at a switching frequency corresponding to a broadcasting carrier frequency interval different for each region. Even if the voltage converter is not operated with the least common multiple of the interval, the voltage converter is operated by setting the switching frequency to the common multiple of the broadcasting carrier frequency interval of each region lower than the frequency of the least common multiple. An effect is obtained that a power supply circuit that operates with power consumption can be realized.
In addition, according to the power supply circuit of the second aspect, the switching frequency of the voltage converter can be easily adapted to the broadcast carrier frequency interval in any region, so that the responsiveness is fast and the power consumption is low. The power supply circuit can be realized.

Furthermore, according to the power supply circuit of claim 3, since it is possible to prevent the harmonics of the switching frequency from being generated in the broadcast band, the power consumption is low and the cost is low. Thus, it is possible to realize a power supply circuit that is less affected by the above.
Further, according to the power supply circuit of the fourth aspect, since the operation of the voltage converter can be continued, there is an effect that it is possible to guarantee the power supply to other devices mounted on the vehicle, for example. can get.

  Embodiments of the present invention will be described below with reference to the drawings.

(overall structure)
FIG. 1 is a block diagram showing a configuration of a power supply circuit according to an embodiment of the present invention. Note that the power supply circuit of the present embodiment is particularly useful when mounted on a vehicle such as an electric vehicle (EV) or a hybrid vehicle (HEV: Hybrid Electric Vehicles). A case where the circuit is mounted on an EV or HEV will be described.
In FIG. 1, a DC / DC converter 1 is a full-bridge type DC / DC converter (voltage converter) that steps up or steps down an input voltage and outputs it. In this embodiment, the DC / DC converter 1 steps down the input voltage. And output a downverter.

  The DC / DC converter 1 will be described in detail. The DC / DC converter 1 steps down the power input from the input terminal by the high-voltage battery B1 that stores power for driving the vehicle driving motor. The positive side terminal and the negative side terminal of the high voltage battery B1 are connected to an H bridge constituted by switching elements Q1, Q2, Q3, Q4 via a fuse H inserted for overcurrent protection. .

That is, the positive terminal of the high voltage battery B1 is connected to the switching elements Q1 and Q3 via the fuse H, while the negative terminal of the high voltage battery B1 is connected to the switching elements Q2 and Q4. It is connected to the.
Further, the connection point between the switching element Q1 and the switching element Q2 constituting the H bridge is connected to one terminal of the primary winding M1 of the transformer T1. On the other hand, a connection point between the switching element Q3 and the switching element Q4 constituting the H bridge is connected to the other terminal of the primary winding M1 of the transformer T1.

  The switching elements Q1 and Q3 are switching elements that conduct in the direction in which current flows from the positive terminal side of the high-voltage battery B1. Switching elements Q2 and Q4 are switching elements that conduct in a direction in which current flows toward the negative terminal side of high-voltage battery B1. Further, the switching elements Q1, Q2, Q3, and Q4 include free wheeling diodes WD1, WD2, WD3, and WD4 that conduct in the opposite direction to the conduction direction of the switching elements Q1, Q2, Q3, and Q4, respectively. It is connected. Further, the voltage conversion operation of the DC / DC converter 1 is controlled at the control terminals of the switching elements Q1, Q2, Q3, Q4 (for example, the gate terminals when the switching elements Q1, Q2, Q3, Q4 are FETs or IGBTs). Control lines are connected from the control unit 4.

  On the other hand, one terminal of the secondary winding M2 of the transformer T1 is connected to an anode terminal of a rectifier diode D1 for rectifying the electric power induced in the secondary winding M2 of the transformer T1. Further, the other terminal of the secondary winding M2 of the transformer T1 also has a rectifier diode for rectifying the electric power induced in the secondary winding M2 of the transformer T1 in the direction opposite to the electric power rectified by the rectifier diode D1. The anode terminal of D2 is connected. The cathode terminal of the rectifier diode D1 and the cathode terminal of the rectifier diode D2 are connected to each other, the connection point between the cathode terminal of the rectifier diode D1 and the cathode terminal of the rectifier diode D2, and the secondary winding M2 of the transformer T1. A capacitor C1 for smoothing the output voltage is connected between the intermediate taps of the first and second coils, and a coil for smoothing the output voltage is similarly connected to a connection point between the rectifier diodes D1 and D2 and the capacitor C1. One terminal of L1 is connected.

  The other terminal of the coil L1 and the intermediate tap of the transformer T1 form the output of the DC / DC converter 1. Specifically, the other terminal of the coil L1 is output as one output terminal of the DC / DC converter 1 via the current sensor 2 that measures the output current of the DC / DC converter 1, and an intermediate tap of the transformer T1. Is output as the other output terminal of the DC / DC converter 1. The output current Iout of the DC / DC converter 1 detected by the current sensor 2 is input to the control unit 4. Further, a voltage sensor 3 for measuring the output voltage of the DC / DC converter 1 is connected to the output terminal of the DC / DC converter 1, and the output voltage Vout of the DC / DC converter 1 detected by the voltage sensor 3 is also It is input to the control unit 4.

  Further, the control unit 4 performs DC / DC so that the output current Iout of the DC / DC converter 1 detected by the current sensor 2 and the output voltage Vout of the DC / DC converter 1 detected by the voltage sensor 3 become target values. A switching duty determination / frequency switching determination circuit 4a for generating an ON / OFF signal for designating energization rates of the switching elements Q1, Q2, Q3, Q4 constituting the converter 1, and a switching duty determination / frequency switching determination circuit 4a. A drive circuit 4b that controls conduction and interruption of the switching elements Q1, Q2, Q3, and Q4 based on the ON / OFF signal to be output is provided.

  Further, the destination information defining the area where the vehicle equipped with the power supply circuit of this embodiment is used is communicated to the control unit 4 via the communication circuit 4c to the switching duty determination / frequency switching determination circuit 4a. ECU (Electronic Control Unit) 5 to be notified by is connected. The ECU 5 is a control means mounted on the vehicle for controlling the vehicle, and the switching duty determination / frequency switching determination circuit 4a acquires the destination information set in the ECU 5 at the time of shipment from the factory, for example, from the ECU 5. At the same time, based on the destination information, the frequency of the ON / OFF signal (switching frequency Fs of the switching elements Q1, Q2, Q3, Q4) to be output to the drive circuit 4b is set. Details of the operation of the control unit 4 will be described later.

  On the other hand, the output terminal of the DC / DC converter 1 includes a low-voltage battery B2 that stores the power stepped down by the DC / DC converter 1, and a wiper or a light that operates by the power stepped down by the DC / DC converter 1. An electrical load 6 that is a vehicle auxiliary machine is connected in parallel. Accordingly, the EV or HEV equipped with the DC / DC converter 1 of this embodiment drives the traveling motor with the electric power of the high voltage battery B1, and travels while charging the high voltage battery B1 by the regenerative operation of the traveling motor. can do.

  At the same time, the low-voltage battery B2 is charged while the power stored in the high-voltage battery B1 is stepped down by the DC / DC converter 1, and the power stored in the low-voltage battery B2 is used for vehicles such as wipers and lights. The vehicle can travel while operating the electrical load 6 that is an auxiliary machine. As the high voltage battery B1, for example, a 144 [V] battery can be used, and as the low voltage battery B2, for example, a 12 [V] battery can be used.

(Switching frequency setting control)
Next, the switching frequency setting control operation of the power supply circuit of this embodiment will be described with reference to the drawings. FIG. 2 is a flowchart showing the switching frequency setting control operation by the control unit 4 of the power supply circuit of this embodiment.
In FIG. 2, the switching duty determination / frequency switching determination circuit 4a of the control unit 4 first determines that the output current Iout of the DC / DC converter 1 detected by the current sensor 2 is a specified value 1 (for example, the specified value 1 is a low voltage battery). It is determined whether or not there is no abnormality in the communication between the ECU 5 and the control unit 4 (the maximum current 30 [A] is sufficient to charge the B2 and the electric load 6 operates) (step B2). S1).

  In step S1, if the output current Iout of the DC / DC converter 1 is greater than the specified value 1 or if there is an abnormality in communication between the ECU 5 and the control unit 4 (NO in step S1), the notification notified from the ECU 5 Since there are cases where the ground information is unknown, for example, an AM radio broadcast carrier frequency interval of 10 [KHz] such as the United States and an AM radio broadcast carrier frequency interval of 9 [KHz] such as Japan. The switching duty determination / frequency switching determination circuit 4a determines the frequency of the ON / OFF signal to be output to the drive circuit 4b (switching frequency Fs of the switching elements Q1, Q2, Q3, and Q4). The base frequency 90 [KHz], which is the least common multiple of both carrier frequency intervals, is set and output (step S2). .

  As a result, when there is some problem in communication between the ECU 5 and the control unit 4, or the amount of current flowing through the load of the DC / DC converter 1 is within a normal range, the switching frequency Fs of the DC / DC converter 1 is Even when the current value is impossible to operate with a low value, for example, the current value that causes the transformer T1 to be saturated, the switching frequency Fs is set to 90 [KHz], which is the base frequency. The operation of the converter 1 can be continued. Specifically, for example, at the switching frequency Fs = 30 [KHz], the current amount flowing through the load is Iout = 30 to 40 [A] and the transformer T1 is saturated. However, the switching frequency Fs = 90 [base frequency] In KHz], the amount of current flowing through the load can be allowed up to Iout = 120 [A].

On the other hand, when the output current Iout of the DC / DC converter 1 detected by the current sensor 2 is equal to or less than the specified value 1 in step S1 and there is no abnormality in communication between the ECU 5 and the control unit 4 (YES in step S1) The switching duty determination / frequency switching determination circuit 4a confirms the destination information notified from the ECU 5 through the communication circuit 4c, and determines whether the destination information is “US” (step S3). .
In step S3, when the destination information is not “US” (NO in step S3), the switching duty determination / frequency switching determination circuit 4a has a carrier frequency interval for AM radio broadcasting of 9 [ The frequency of the ON / OFF signal output to the drive circuit 4b (the switching frequency Fs of the switching elements Q1, Q2, Q3, and Q4) is half of the base frequency 90 [KHz] so that it can be used in the area of KHz]. Is set to 45 [KHz] and output (step S4).

  If the destination information is “US” in step S3 (YES in step S3), the switching duty determination / frequency switching determination circuit 4a determines that the carrier frequency interval for AM radio broadcasting is 10 [KHz]. The frequency of the ON / OFF signal output to the drive circuit 4b (the switching frequency Fs of the switching elements Q1, Q2, Q3, and Q4) is 1/3 of the base frequency 90 [KHz]. [KHz] and output (step S5). As described above, based on the destination information, the switching frequency is set to a common multiple of the carrier frequency interval for AM radio broadcasting in each region, for example, 45 [KHz] or 30 [KHz] lower than the base frequency 90 [KHz]. Thus, by operating the DC / DC converter 1, it is possible to realize an electric power supply circuit that operates with low power consumption.

  The device for storing the electric power for driving the traveling motor is not limited to the high voltage battery B1, and any device can be used as long as it is a power storage device (energy storage device) including a capacitor or the like that can store DC power. Also good. Similarly, a device for supplying low-voltage DC power to the low-voltage drive electrical load 6 or the like is not limited to the low-voltage battery B2, but is a power storage device (energy storage device) including a capacitor or the like that can store DC power. Anything can be used.

  As described above, according to the power supply circuit of the present embodiment, the switching duty determination / frequency switching determination circuit 4a is in the case where the destination information notified from the ECU 5 via the communication circuit 4c is not “US”. For example, the switching frequency Fs of the switching elements Q1, Q2, Q3, and Q4 is set to a base frequency of 90 [KHz] so that the carrier frequency interval for AM radio broadcasting is 9 [KHz] as in Japan. The output is set to 45 [KHz] which is a half. When the destination information is “USA”, the switching frequency Fs of the switching elements Q1, Q2, Q3, Q4 is set so that the carrier frequency interval for AM radio broadcasting is 10 [KHz]. The output is set to 30 [KHz], which is one third of the base frequency 90 [KHz].

Accordingly, the voltage converter can be operated at a switching frequency corresponding to a different carrier frequency interval for AM radio broadcasting in each region, so that the switching frequency is the base frequency of the least common multiple of the carrier frequency intervals for AM radio broadcasting in a plurality of regions. Even if the DC / DC converter 1 is not operated at 90 [KHz], the DC / DC converter 1 is operated by setting the switching frequency to a common multiple of the broadcast carrier frequency interval of each region lower than the base frequency. As a result, it is possible to realize a power supply circuit that operates with low power consumption. In particular, when the power supply circuit is mounted on the vehicle as in the present embodiment, the switching elements Q1, Q2 are reduced when the load current is small, such as during the spring or autumn day, when the air conditioning requirements in the passenger compartment are reduced. By lowering the switching frequency Fs of Q3 and Q4, the power consumption of the power supply circuit can be reduced.
Moreover, since the switching frequency of the DC / DC converter 1 can be set to 1 / integer of the base frequency, it is possible to easily cope with the broadcast carrier frequency interval in any region, so that the responsiveness Therefore, it is possible to achieve an effect of realizing a power supply circuit that is fast and consumes low power.

Furthermore, when the switching frequency is changed from the base frequency to the frequency corresponding to the desired destination information, the switching frequency harmonics are generated in the AM radio broadcast band by directly changing the frequency without continuously changing it. Can be prevented. Therefore, it is possible to achieve an effect of realizing a power supply circuit with low power consumption, low cost, and less influence on the AM radio broadcast receiver.
Further, when there is some problem in communication with the ECU 5 that acquires the destination information, or the amount of current flowing through the load of the DC / DC converter 1 (for example, the low voltage battery B2 or the electrical load 6) is within a normal range. However, even when the current value is such that the switching frequency of the DC / DC converter 1 cannot be lowered, for example, the current value at which the transformer T1 is saturated, the switching frequency is set to the base frequency. Since the operation of the DC / DC converter 1 can be continued, for example, it is possible to guarantee the power supply to other devices mounted on the vehicle.

Specifically, when explaining the carrier frequency band and carrier frequency interval for AM radio broadcasting in each country, AM radio broadcasting in each country
(1) United States: carrier frequency band = 530 to 1710 [KHz], carrier frequency interval = 10 [KHz].
(2) Japan: Carrier frequency band = 522 to 1629 [KHz], carrier frequency interval = 9 [KHz].
(3) European countries: carrier frequency band = 531-1602 [KHz], carrier frequency interval = 9 [KHz].
(4) Asian countries: carrier frequency band = 531-1602 [KHz], carrier frequency interval = 9 [KHz].
It is operated with the specification. Therefore, the power supply circuit of the present embodiment has an effect that it can be used satisfactorily with little influence on the AM radio broadcast receiver even when used in any of the above-mentioned areas.

It is a block diagram which shows the structure of the electric power supply circuit in one Example of this invention. It is a flowchart which shows the switching frequency setting control operation by the control part of the electric power supply circuit of the Example.

Explanation of symbols

1 DC / DC converter (voltage converter)
2 Current sensor (current detection means)
4 Control unit (frequency setting means)
4c Communication circuit (communication means)
5 ECU (control means)
6 Electrical load (load)
B1 High voltage battery (power storage device)
B2 Low voltage battery (load)

Claims (4)

In a power supply circuit comprising a power storage device and a voltage converter that converts the voltage of the power storage device and supplies the converted voltage to a load.
A power supply circuit comprising frequency setting means for setting a switching frequency of a switching element constituting the voltage converter based on destination information defining a region to be used. The switching frequency is set to the least common multiple of the broadcast carrier frequency intervals of all the regions used, and is set to an integral fraction of the base frequency specified as one common to the destination information. The power supply circuit according to claim 1. The frequency setting means, when setting the switching frequency, directly changes the frequency from the base frequency to a frequency corresponding to any destination information. Power supply circuit. A communication means for acquiring the destination information from an external control means;
Current detection means for detecting a current flowing through the load,
The switching frequency is set to the base frequency when communication with the control unit is abnormal or when the amount of current flowing through the load is a predetermined value or more. A power supply circuit according to any one of the above.

Images