JP2010074913A - Power supply system, and vehicle mounted with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply system capable of stably supplying power to an electric load at low power consumption, and to provide a vehicle mounted with the power supply system. <P>SOLUTION: The power supply system includes: a switching power supply circuit 30 for stepping-down the DC voltage VH from a high voltage battery 10 for outputting the voltage VL1 to a power supply line SPL1; an auxiliary battery 20 connected to the power supply line SPL1 for being charged with the input voltage VL1; a step-down chopper circuit 40 for stepping-down the voltage VL1 from the power supply line SPL1 down to voltage VL2 for outputting to a power supply line SPL2; and a second auxiliary machine 130 connected to the power supply line SPL2 for being driven with the input voltage VL2. The voltage VL2 is an operation voltage lower limit where the normal operation of the second auxiliary machine 130 is guaranteed. When a voltage reduction occurs during the stop of a vehicle or in the voltage VL2, the step-down chopper circuit 40 stops a step-down operation, to supply the voltage VL1 supplied to the power supply line SPL1 directly to the power supply line SPL2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply system for supplying electric power to an electric load and a vehicle equipped with the same, and particularly to a power supply system that outputs a sub power supply system obtained by converting a voltage of a single main power supply, and is connected to the sub power supply system. The present invention relates to a configuration for stably supplying power to an electric load with low power consumption.

  Recently, attention has been focused on hybrid vehicles and electric vehicles that are driven by the driving force of an electric motor as environmentally friendly vehicles. These electric vehicles are equipped with a power supply system for supplying electric power to an electric motor as a drive source.

  In this power supply system, in addition to a main power supply for supplying power to the electric motor, a configuration having a sub power supply system in which the voltage of the main power supply is converted to supply power to an electric load has been proposed. According to this, a high voltage battery is used as the main power supply, and the sub power supply system is configured by a step-down converter that steps down the voltage of the main power supply to a voltage corresponding to the rated voltage of the electric load.

As such a step-down converter, for example, Japanese Patent Laid-Open No. 9-322531 (Patent Document 1) discloses switching means for switching a DC voltage on the input side based on a control signal into a pulse signal, and a DC voltage on the input side. Is supplied as a power supply voltage, and has a control means for generating a control signal when the power supply voltage is equal to or higher than a predetermined minimum operating voltage, and a smoothing coil for smoothing the pulse signal. There is disclosed a step-down chopper circuit provided with smoothing means for sending the output voltage as an output voltage to the output side. According to this, when the DC voltage on the input side is converted into a pulse signal and then smoothed by the smoothing coil, the induced voltage generated in the coil that is electromagnetically coupled to the smoothing coil is rectified and smoothed, and the input side DC voltage is rectified and smoothed. It is added to the DC voltage. Therefore, a voltage several V higher than the DC voltage is supplied as the power supply voltage for the control means. Therefore, even if the DC voltage is lowered, the power supply voltage supplied to the control means is in a range where the control means operates normally.
JP-A-9-322531 JP 2003-254208 A JP 2004-229477 A

  According to the step-down chopper circuit described in Patent Document 1 described above, even if the DC voltage on the input side decreases, the control means using the DC voltage as the power supply voltage can operate normally.

  However, in the step-down chopper circuit described in Patent Document 1 described above, the control means is supplied with a voltage several V higher than the DC voltage as the power supply voltage, so the power consumption of the control means is derived from the DC voltage. There has been a problem of increasing according to the amount of addition of. As a result, while the normal operation of the step-down chopper circuit is ensured, the power loss due to the step-down chopper circuit is increased, which is not suitable for low power consumption.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a power supply system capable of stably supplying power to an electric load with low power consumption and a vehicle equipped with the same. It is to be.

  According to an aspect of the present invention, a power supply system includes a power supply circuit that outputs a first voltage to a first power supply line, a power storage unit that is connected to the first power supply line and is charged by receiving the first voltage. A voltage conversion circuit having a step-down function for stepping down the first voltage from the first power supply line to the second voltage and outputting it to the second power supply line; and receiving the second voltage connected to the second power supply line And an electric load to be driven. The electric load has the second voltage as an operating voltage lower limit value that ensures normal operation. The power supply system further includes voltage drop protection means for stopping the step-down operation in the voltage conversion circuit and fixing the voltage conversion ratio to about 1 when the step-down function of the voltage conversion circuit is impaired.

  Preferably, the voltage drop protection means detects that the step-down function of the voltage conversion circuit is impaired when the voltage of the second power supply line falls below the second voltage.

  Preferably, the voltage drop protection means detects that the step-down function of the voltage conversion circuit is impaired when the power supply circuit is stopped.

  Preferably, the voltage conversion circuit includes a chopper circuit including at least a switching element connected between the first power supply line and the second power supply line. The power supply system further includes a control unit that sets a duty ratio at which the voltage of the second power supply line becomes the second voltage and performs switching control of the switching element. The voltage drop protection means maintains the switching element in an ON state when the voltage step-down function of the voltage conversion circuit is impaired.

  Preferably, the electric load includes a wireless device. The control means sets the switching frequency of the switching element to a frequency different from the use frequency of the wireless device.

  According to another aspect of the present invention, the power supply circuit includes a switching power supply that steps down the power supply voltage from the power supply and outputs the first voltage to the first power supply line. The vehicle includes any one of the power supply systems described above and a rotating electrical machine that drives the wheels by receiving power supplied from the power supply.

  Preferably, the electric load includes a vehicle control device.

  According to the present invention, in a power supply system that outputs a sub power supply system obtained by converting the voltage of the main power supply, it is possible to stably supply power to the electric load connected to the sub power supply system with low power consumption.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a schematic configuration diagram of an electric vehicle equipped with a power supply system according to an embodiment of the present invention.

  Referring to FIG. 1, the vehicle according to the embodiment of the present invention is typically a hybrid vehicle, and is equipped with an internal combustion engine (not shown) and motor M1, and the driving force from each is set to an optimum ratio. Drive under control. Further, the vehicle is equipped with a high voltage battery 10 for supplying electric power to the motor M1. The high voltage battery 10 is a main battery of the motor M1 for driving the vehicle, and is made of, for example, a nickel metal hydride or lithium ion battery. Note that the high-voltage battery 10 may be configured with a large-capacity capacitor for power storage such as an electric double layer capacitor instead of such a secondary battery.

  Boost converter 12 boosts voltage VH between power supply line PL1 and ground line SL1, and outputs the boosted voltage between power supply line PL2 and ground line SL2. Inverter 14 receives a DC voltage between power supply line PL2 and ground line SL1 as a power supply voltage, and is subjected to switching control so as to generate a three-phase AC current. Then, the motor M1 is driven by the inverter 14, and a differential gear and wheels (not shown) are rotated by the motor M1.

(Auxiliary load)
The vehicle further includes an auxiliary battery 20, a plurality of auxiliary loads 110 and 130, and a DC / DC converter 100 connected to power supply line PL1 and ground line SL1.

  DC / DC converter 100 steps down voltage VH between power supply line PL1 and ground line SL1 to a plurality of different voltages VL1 and VL2 and supplies them to a plurality of auxiliary loads and auxiliary battery 20 respectively. To do.

  Specifically, the DC / DC converter 100 steps down the voltage VH to the voltage VL1 and supplies it to the power supply line SPL1. The auxiliary battery 20 and the first auxiliary device 110 are connected to the power line SPL1.

  The auxiliary battery 20 constitutes the “power storage unit” in the present invention, and is composed of, for example, a lead storage battery. Auxiliary battery 20 is charged with DC power from power supply line SPL1 and supplies the stored power to first auxiliary device 110. That is, the auxiliary battery 20 also functions as a power buffer for compensating for an imbalance between the output power of the DC / DC converter 100 and the demand power of the first auxiliary device 110.

  The first auxiliary machine 110 operates by receiving the supply of the voltage VL1 from the power supply line SPL1. The first auxiliary machine 110 is a general term for auxiliary loads that operate at the same voltage as the output voltage (for example, 12 V) of the auxiliary battery 20.

  Furthermore, the DC / DC converter 100 steps down the voltage VH2 to a voltage VL2 lower than the voltage VL1 and supplies it to the power supply line SPL2. A second auxiliary machine 130 is connected to the power supply line SPL2.

  The second auxiliary machine 130 is a general term for auxiliary loads that operate at a lower voltage (for example, 9 V) than the output voltage of the auxiliary machine battery 20. As an example, an engine control ECU (Electronic Control Unit), a hybrid A control ECU, a control unit in an IPM (intelligent power module) of the inverter 14 and the boost converter 12, and a plurality of ECUs such as a battery control ECU are included. The second auxiliary machine 130 includes a car navigation system, a car audio, an interior light, and the like. These are auxiliary machine loads for providing a comfortable indoor environment to the vehicle occupant.

  Here, in the present embodiment, voltage VL2 supplied to power supply line SPL2 is the lower limit value of the operating voltage at which the normal operation of second auxiliary machine 130 is guaranteed. As a result, unlike the first auxiliary device 110 connected to the power supply line SPL1, the second auxiliary device 130 operates by receiving a voltage at the operating voltage lower limit level that is lower than the output voltage of the auxiliary battery 20. To do. As a result, the power consumption of the second auxiliary machine 130 is suppressed to a lower power than that of the first auxiliary machine 110.

  Further, in the power supply line SPL1, the voltage VL1 may decrease due to a rapid increase in power consumption of the first auxiliary device 110. Further, the decrease in the voltage VL1 may occur depending on the degree of deterioration of the auxiliary battery 20. Therefore, when the first auxiliary machine 110 and the second auxiliary machine 130 are connected in parallel to the power supply line SPL1, the operating voltage of the second auxiliary machine 130 is guaranteed against the decrease in the voltage VL1. The voltage guarantee circuit must be provided inside each electric load constituting the second auxiliary machine 130.

  On the other hand, in the present embodiment, the step-down chopper circuit 40 connected between the power supply line SPL1 and the power supply line SPL2 functions as a voltage guarantee circuit in an integrated manner. An increase in loss can be suppressed by installing the guarantee circuit. As a result, efficient and stable power feeding to the second auxiliary machine 130 is possible.

  Note that both the power saving and the stabilization of the operation in the second auxiliary machine 130 are as follows. The voltage drop protection function of the step-down chopper circuit 40, which will be described later, stably supplies a voltage to the power supply line SPL2. Is ensured by.

  Control device 50 performs step-up control of step-up converter 12 and switching control of inverter 14 and step-down control of DC / DC converter 100. The control device 50 may be realized by a plurality of ECUs included in the second auxiliary machine 130 communicating with each other control information.

(Configuration of DC / DC converter)
FIG. 2 is a circuit diagram showing the configuration of the DC / DC converter 100 of FIG.

  Referring to FIG. 2, DC / DC converter 100 includes a switching power supply circuit 30 and a step-down chopper circuit 40.

  The switching power supply circuit 30 rectifies the AC current generated on the secondary side of the transformer Tr, the bridge circuit that receives the power from the high-voltage battery 10 and generates AC current, the primary side that receives power from the bridge circuit, and the like. A rectifier circuit.

  The bridge circuit includes a transistor Q1 having a collector connected to the high voltage battery 10, a transistor Q2 having a collector connected to the emitter of the transistor Q1, a transistor Q2 having an emitter connected to the ground line SL1, and a collector connected to the high voltage battery 10. Transistor Q3, and a transistor Q4 having a collector connected to the emitter of transistor Q3 and an emitter connected to ground line SL1. The bases of the transistors Q1 to Q4 are subjected to switching control when a control signal instructing a step-down operation is given by the control device 50 of FIG.

  The transformer Tr has a primary coil L2 having one end connected to the emitter of the transistor Q1 and the other end connected to the emitter of the transistor Q3, secondary coils L3 and L4 connected in series, and a primary coil L2. And an iron core that electromagnetically couples the secondary coils L3 and L4.

  The rectifier circuit includes diodes D5 and D6, a coil L5, and a smoothing capacitor C2. The cathodes of the diodes D5 and D6 are both connected to one end of the coil L5. The anode of the diode D5 is connected to one end of the secondary coil L3. The anode of the diode D6 is connected to one end of the secondary coil L4. Both the other end of secondary coil L3 and the other end of secondary coil L4 are connected to ground line SL2. The other end of coil L5 is connected to power supply line SPL1. Smoothing capacitor C2 is connected between power supply line SPL1 and ground line SL2.

  The switching power supply circuit 30 switches the DC input voltage VH from the high-voltage battery 10 by the switching operation of the transistors Q1 to Q4 connected to the primary coil L2 of the transformer Tr, and outputs the switching output to the secondary coil of the transformer Tr. Take out to L3 and L4. The voltage appearing in the secondary coil accompanying the switching operation of the transistor is rectified by the rectifier circuit, converted to the DC voltage VL1 by the smoothing capacitor C2, and output to the power supply line SPL1.

  Step-down chopper circuit 40 includes transistors Q7 and Q8 which are switching elements, diodes D7 and D8, coils L7 and L8, and smoothing capacitors C3 and C4.

  Transistors Q7 and Q8 are connected in series between power supply line SPL1 and ground line SL2. The collector of transistor Q7 is connected to power supply line SPL1, and the emitter of transistor Q8 is connected to ground line SL2. Further, diodes D7 and D8 for passing a current from the emitter side to the collector side are connected between the collector and emitter of the transistors Q7 and Q8, respectively.

  One end of coil L7 is connected to the collector of transistor Q7, and the other end is connected to power supply line SPL1. One end of coil L8 is connected to an intermediate point between transistors Q7 and Q8, that is, the emitter of transistor Q7 and the collector of transistor Q8, and the other end is connected to power supply line SPL2. The bases of the transistors Q7 and Q8 are subjected to switching control when a control signal instructing a step-down operation is given by the control device 50 of FIG.

  Smoothing capacitor C3 is connected between power supply line SPL1 and ground line SL2. Smoothing capacitor C4 is connected between power supply line SPL2 and ground line SL2.

  The step-down chopper circuit 40 steps down the DC voltage VL1 output from the switching power supply circuit 30 to the voltage VL2 in accordance with a control signal from the control device 50, and supplies the voltage VL2 to the power supply line SPL2.

  More specifically, step-down chopper circuit 40 turns on / off transistor Q7 at a predetermined duty ratio and maintains transistor Q8 in an off state based on a control signal from control device 50 during step-down operation. Let In the ON period of transistor Q7, a charging current flows from power supply line SPL1 to power supply line SPL2 through transistor Q7 and coil L8 in this order. Subsequently, when the transistor Q7 transitions from the on state to the off state, a magnetic flux is generated so as to prevent a current change in the coil L8, so that the charging current continues to flow through the diode D8, the coil L8, and the power supply line SPL2 in order. On the other hand, in terms of electrical energy, DC power is supplied only through the power supply line SPL1 and the ground line SL2 only during the on-period of the transistor Q7. Therefore, if the charging current is kept constant, The average voltage of the DC power supplied from the chopper circuit 40 to the power supply line SPL2 is a value obtained by multiplying the DC voltage VL1 between the power supply line SPL1 and the ground line SL2 by the duty ratio.

  Smoothing capacitor C4 smoothes the DC voltage output to power supply line SPL2, and supplies the smoothed DC voltage VL2 to second auxiliary device 130 (FIG. 1).

  Further, when the step-down chopper circuit 40 loses its step-down function, the DC voltage VL1 supplied from the power supply line SPL1 from the switching power supply circuit 30 or the auxiliary battery 20 in accordance with a control signal from the control device 50. Is directly supplied to the power supply line SPL2 (ie, without being stepped down).

  More specifically, step-down chopper circuit 40 stops the step-down operation, maintains transistor Q7 in an on state, and maintains transistor Q8 in an off state based on a control signal from control device 50. As a result, the voltage conversion ratio in step-down chopper circuit 40 is approximately 1, and the voltage of DC power supplied from step-down chopper circuit 40 to power supply line SPL2 and ground line SL2 is approximately equal to voltage VL1 of power supply line SPL1. .

  Thus, in addition to the step-down function for stepping down the DC power received from the switching power supply circuit 30, the step-down chopper circuit 40 directly applies the voltage VL1 output to the power line SPL1 when the step-down function is impaired. And a voltage drop protection function to be supplied to the power supply line SPL2. As a result, as described below, DC / DC converter 100 according to the present embodiment can stably supply the operating voltage lower limit value of second auxiliary machine 130 to power supply line SPL2. As a result, the second auxiliary machine 130 can be stably operated with low power consumption.

  FIG. 3 is a diagram for explaining a voltage conversion operation executed by the DC / DC converter 100 of FIG.

  Referring to FIG. 3, in a normal time when the step-down function of step-down chopper circuit 40 is not impaired, the DC power supplied from high-voltage battery 10 is supplied from switching power supply circuit 30 as shown by line LN1 in the drawing. Is stepped down to the voltage VL1 and supplied to the power supply line SPL1 and the auxiliary battery 20. Then, the DC power after step-down is further stepped down to voltage VL2 in step-down chopper circuit 40 as shown by line LN2 in the figure and supplied to power supply line SPL2.

  As described above, the DC / DC converter 100 is configured to have a two-step voltage step-down function so that two DC / DC converters connected in parallel to the power supply line PL1 and the ground line SL1 are integrated. Can do. As a result, the power supply system can be reduced in size.

  Further, as described above, the voltage VL2 supplied to the power supply line SPL2 corresponds to the lower limit value of the operating voltage of the second auxiliary machine 130, so that the power consumption in the second auxiliary machine 130 can be reduced.

  On the other hand, when the switching power supply circuit 30 performs a switching operation even when the vehicle is stopped, a large current consumption is driven by the DC / DC converter 100. From the viewpoint of power saving, the vehicle is stopped. Therefore, it is desirable to stop the switching operation of the switching power supply circuit 30. In this case, since the power supply from the switching power supply circuit 30 to the power supply line SPL1 is cut off, the first auxiliary machine 110 connected to the power supply line SPL1 operates by receiving the supply of electric power from the auxiliary battery 20.

  On the other hand, in second auxiliary device 130 connected to power supply line SPL2, the power supply to power supply line SPL2 is interrupted because the step-down function for stepping down DC power received from switching power supply circuit 30 is impaired. , May not work properly.

  Therefore, in the present embodiment, when it is determined that the step-down function of the step-down chopper circuit 40 is impaired by the switching power supply circuit 30 being stopped, as shown by the line LN3 in FIG. 4, the step-down chopper circuit The step-down operation of 40 is stopped, and the DC power from the auxiliary battery 20 is supplied to the power supply line SPL2 with the voltage conversion ratio fixed at approximately 1. According to this, even when the switching power supply circuit 30 is stopped, it is possible to suppress the voltage VL2 of the power supply line SPL2 from falling below the operating voltage lower limit value of the second auxiliary machine 130. As a result, the stable operation of the second auxiliary machine 130 can be ensured while suppressing the power consumption of the DC / DC converter 100 while the vehicle is stopped.

  In this specification, a control mode in which the step-down operation is performed so that the power output from the switching power supply circuit 30 to the power supply line SPL1 is stepped down and supplied to the power supply line SPL2 is referred to as a “normal mode”. In contrast, when the switching operation of the switching power supply circuit 30 is stopped, the power output from the auxiliary battery 20 to the power supply line SPL1 in place of the switching power supply circuit 30 is fixed at a voltage conversion ratio of approximately 1, and the power is supplied. A control mode in which the step-down operation is stopped so as to be supplied to the line SPL2 is also referred to as a “backup mode”.

  Even when the normal mode is being executed, if the step-down function of the step-down chopper circuit 40 is impaired due to an abnormality in the switching control of the transistor Q7 or Q8, the voltage VL2 of the power supply line SPL2 is lowered and the second compensation is performed. The operating voltage lower limit value of the machine 130 may be lower.

  Therefore, in the present embodiment, when it is detected that the voltage VL2 of the power supply line SPL2 is lower than the predetermined threshold value Vth, the step-down operation of the step-down chopper circuit 40 is stopped and the line LN4 in FIG. As shown in FIG. 5, the DC power from the switching power supply circuit 30 is supplied to the power supply line SPL2 with the voltage conversion ratio fixed to approximately 1. According to this, it is possible to avoid that the power supply to the second auxiliary machine 130 is immediately interrupted when the abnormality of the step-down chopper circuit 40 is detected. As a result, a fail-safe function that ensures the safety of the vehicle when an abnormality is detected is ensured.

  In the present specification, when the voltage drop of the power supply line SPL2 is detected, the power output from the switching power supply circuit 30 to the power supply line SPL1 is supplied to the power supply line SPL2 with the voltage conversion ratio fixed to approximately 1. The control mode for stopping the step-down operation is also referred to as “fail-safe mode”.

  FIG. 6 is a diagram illustrating an example of temporal changes in the voltages VL1 and VL2 of the power supply lines SPL1 and SPL2.

  Referring to FIG. 6, it is assumed that the vehicle is stopped during the period from time t1 to time t2. In this period, since the switching operation of the switching power supply circuit 30 is stopped, the step-down chopper circuit 40 executes the backup mode (FIG. 4). In this backup mode, DC power from the auxiliary battery 20 is directly supplied to the power supply line SPL2. Therefore, voltage VL2 of power supply line SPL2 is maintained at the output voltage (for example, 12V) of auxiliary battery 20 in the same manner as voltage VL1 of power supply line SPL1.

  Next, when the vehicle enters the system start-up state (IG on state) at time t2, the switching power supply circuit 30 operates, so that the voltage VL1 of the power supply line SPL1 is a voltage obtained by stepping down the output voltage VH from the high-voltage battery 10. (For example, 14V). At time t3, when the step-down chopper circuit 40 operates and starts executing the normal mode (FIG. 3), the voltage VL2 of the power supply line SPL2 is reduced to a voltage (for example, 9V) obtained by stepping down the voltage VL1 of the power supply line SPL1. Maintained.

  When the vehicle is in a system stop state (IG off state) at time t4, the step-down chopper circuit 40 switches from the normal mode to the backup mode again.

  As described above, the step-down chopper circuit 40 executes the switching between the normal mode and the backup mode, so that the power line SPL2 has the lower operating voltage of the second auxiliary device 130 regardless of whether the vehicle is stopped or traveling. The corresponding voltage is supplied stably. As a result, power saving and stable operation of the second auxiliary machine 130 can be realized.

  On the other hand, when the step-down function of the step-down chopper circuit 40 is impaired during execution of the normal mode, a voltage drop occurs on the power supply line SPL2 as shown at time t7 in the drawing. In this case, it is detected that voltage VL2 of power supply line SPL2 has fallen below a predetermined threshold value Vth, and step-down chopper circuit 40 is switched from the normal mode to the failsafe mode (FIG. 5). As a result, the voltage VL1 of the power supply line SPL1 is directly supplied to the power supply line SPL2, so that the voltage VL2 rises to a level equivalent to the voltage VL1. As a result, the stable operation of the second auxiliary machine 130 can be guaranteed even after the abnormality of the step-down chopper circuit 40 is detected.

  FIG. 7 is a diagram illustrating an example of temporal changes in the voltages VL1 and VL2 of the power supply lines SPL1 and SPL2 when the normal mode (FIG. 3) is being executed.

  Referring to FIG. 7, voltage VL <b> 1 of power supply line SPL <b> 1 has a fluctuation range due to a rapid increase in power consumption of first auxiliary machine 110 and a deterioration state of auxiliary battery 20. On the other hand, the voltage VL2 supplied to the power supply line SPL2 is maintained at the operating voltage lower limit value of the second auxiliary machine 130 by the step-down function of the step-down chopper circuit 40.

  Thus, by maintaining the voltage VL2 of the power supply line SPL2 at the operating voltage lower limit value of the second auxiliary machine 130, the current consumption of the second auxiliary machine 130 can be reduced. Specifically, the relationship as shown in FIG. 8 is established between the operating voltage of the electric load and the current consumption. According to FIG. 8, the current consumption increases as the operating voltage increases with the protection voltage (the minimum voltage necessary for the operation of the electric load) as the lower limit. In such a relationship, the operating voltage of the second auxiliary machine 130 is maintained at the operating voltage lower limit value as indicated by a point P1 in the figure, so that the current consumption can be reduced.

  As described above, according to the power supply system according to the present embodiment, it is possible to realize both the power saving of the electric load and the stabilization of the operation. As a result, the energy efficiency of the vehicle can be improved while ensuring the running performance of the vehicle and a comfortable in-vehicle environment.

  1 and FIG. 2, the switching power supply circuit 30 corresponds to a “power supply circuit”, the auxiliary battery 20 corresponds to a “power storage unit”, and the step-down voltage is related to the embodiment of the present invention shown in FIGS. The chopper circuit 40 corresponds to a “voltage conversion circuit”, and the second auxiliary machine 130 corresponds to an “electric load”.

The above processing can be summarized as a processing flow as shown in FIG.
(flowchart)
FIG. 9 is a flowchart for illustrating a control structure of a program executed by control device 50 (FIG. 1) for controlling step-down chopper circuit 40 according to the embodiment of the present invention.

  Referring to FIG. 9, control device 50 determines whether or not the vehicle is in a system activation state (IG on state) (step S01). When the vehicle is not in the system activation state (NO in step S01), control device 50 sets step-down chopper circuit 40 (FIG. 2) to the backup mode (FIG. 4). In this case, step-down chopper circuit 40 stops the step-down operation, maintains transistor Q7 in the on state, and maintains transistor Q8 in the off state based on the control signal from control device 50 (step S08). . As a result, the voltage conversion ratio in the step-down chopper circuit 40 becomes substantially 1, and a voltage substantially equal to the voltage VL1 of the power supply line SPL1 is supplied from the step-down chopper circuit 40 to the power supply line SPL2.

  On the other hand, when the vehicle is in the system activation state (YES in step S01), control device 50 operates switching power supply circuit 30 (FIG. 2) and high voltage battery 10 (FIG. 1). ) Is stepped down to voltage VL1 and supplied to power supply line SPL1 (step S02).

  Next, control device 50 obtains voltage VL1 of power supply line SPL1 based on a detection signal input from a voltage sensor (not shown) arranged between power supply line SPL1 and ground line SL2. Control device 50 acquires voltage VL2 of power supply line SPL2 based on a detection signal input from a voltage sensor (not shown) arranged between power supply line SPL2 and ground line SL2 (step S03). . Then, control device 50 determines whether or not voltage VL1 of power supply line SPL1 is higher than a predetermined reference value Vst1 (step S04). The predetermined reference value Vst1 is a voltage for determining whether or not the step-down function of the switching power supply circuit 30 is normal, and is slightly higher than the output voltage of the auxiliary battery 20 in the present embodiment. The voltage is preset (for example, 13V).

  When voltage VL1 of power supply line SPL1 is equal to or lower than predetermined reference value Vst1 (NO in step S04), control device 50 determines that the step-down function of switching power supply circuit 30 has been impaired and performs voltage conversion operation. This process is terminated.

  In contrast, when voltage VL1 of power supply line SPL1 is higher than predetermined reference value Vst1 (YES in step S04), control device 50 determines that the step-down function of switching power supply circuit 30 is normal. Then, the step-down chopper circuit 40 is operated (step S05).

  At this time, control device 50 determines whether or not voltage VL2 of power supply line SPL2 is lower than a predetermined threshold value Vth (step S06). If voltage VL2 of power supply line SPL2 is equal to or higher than predetermined threshold value Vth (step S06). In the case of NO), the step-down chopper circuit 40 is set to the normal mode (FIG. 3). In this case, the step-down chopper circuit 40 turns on / off the transistor Q7 with a predetermined duty ratio based on the control signal from the control device 50, and maintains the transistor Q8 in the off state (step S07). As a result, the average voltage of the DC power supplied from the step-down chopper circuit 40 to the power supply line SPL2 is a value obtained by multiplying the voltage VL1 of the power supply line SPL1 by the duty ratio.

  On the other hand, when voltage VL2 of power supply line SPL2 is lower than predetermined threshold Vth (YES in step S06), control device 50 determines that the step-down function of step-down chopper circuit 40 is impaired. The step-down chopper circuit 40 is set to the fail-safe mode (FIG. 5). In this case, step-down chopper circuit 40 stops the step-down operation, maintains transistor Q7 in the on state, and maintains transistor Q8 in the off state based on the control signal from control device 50 (step S08). . As a result, the voltage conversion ratio in the step-down chopper circuit 40 becomes substantially 1, and a voltage substantially equal to the voltage VL1 of the power supply line SPL1 is supplied from the step-down chopper circuit 40 to the power supply line SPL2.

(Example of change)
For the switching power supply circuit 30 and the step-down chopper circuit 40 shown in FIG. 2, the switching frequency for turning on / off each transistor is set to the use of a radio device (for example, a radio receiver such as a car audio) mounted on the vehicle. By setting the frequency different from the frequency, it is possible to prevent electrical noise generated during the switching operation from being mixed into the communication signal of the wireless device and causing the wireless device to generate noise.

  FIG. 10 is a diagram illustrating an example of the switching frequency in the switching power supply circuit 30 and the step-down chopper circuit 40.

  Referring to FIG. 10, the switching frequency of the switching power supply circuit 30 is set on the low frequency side with the use frequency of the wireless device (for example, about several hundred to several thousand kHz in the case of a radio receiver) interposed therebetween, The switching frequency of the step-down chopper circuit 40 is set on the high frequency side. Note that these switching frequencies can be set to appropriate values in consideration of the balance with switching loss and the like within a range that does not overlap with the frequency used by the wireless device.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic configuration diagram of an electric vehicle equipped with a power supply system according to an embodiment of the present invention. FIG. 2 is a circuit diagram illustrating a configuration of the DC / DC converter of FIG. 1. It is a figure for demonstrating the voltage conversion operation | movement performed with the DC / DC converter of FIG. It is a figure for demonstrating the voltage conversion operation | movement performed with a DC / DC converter at the time of execution of backup mode. It is a figure for demonstrating the voltage conversion operation | movement performed with a DC / DC converter at the time of execution of fail safe mode. It is a figure which shows the time change of the voltage of a power supply line. It is a figure which shows an example of the voltage change of a power supply line when the step-down chopper circuit is performing normal mode. It is a figure for demonstrating the relationship between the operating voltage of an electrical load, and consumption current. It is a flowchart for demonstrating the control structure of the program performed with the control apparatus which controls the pressure | voltage fall chopper circuit according to embodiment of this invention. It is a figure which shows an example of the switching frequency in a switching power supply circuit and a step-down chopper circuit.

Explanation of symbols

  10 High Voltage Battery, 12 Boost Converter, 14 Inverter, 20 Auxiliary Battery, 30 Switching Power Supply Circuit, 40 Step-down Chopper Circuit, 50 Control Device, 100 DC / DC Converter, 110 First Auxiliary Machine, 130 Second Auxiliary Machine, C2 ~ C4 smoothing capacitor, D1-D8 diode, L1-L8 coil, PL1, PL2, SPL1, SPL2 power line, Q1-Q8 transistor, SL1, SL2 ground line.

Claims (7)

A power supply circuit for outputting a first voltage to the first power supply line;
A power storage unit connected to the first power supply line and charged by receiving the first voltage;
A voltage conversion circuit having a step-down function of stepping down the first voltage from the first power supply line to a second voltage and outputting it to a second power supply line;
An electrical load connected to the second power supply line and driven by receiving the second voltage;
The electrical load has the second voltage as an operating voltage lower limit value that ensures normal operation,
A power supply system further comprising voltage drop protection means for stopping a step-down operation in the voltage conversion circuit and fixing a voltage conversion ratio to approximately 1 when the step-down function of the voltage conversion circuit is impaired.   2. The power supply system according to claim 1, wherein the voltage drop protection unit detects that a step-down function of the voltage conversion circuit is impaired when a voltage of the second power supply line falls below the second voltage. .   2. The power supply system according to claim 1, wherein the voltage drop protection unit detects that the step-down function of the voltage conversion circuit is impaired when the power supply circuit is stopped. The voltage conversion circuit includes a chopper circuit including at least a switching element connected between the first power supply line and the second power supply line,
Control means for controlling the switching of the switching element by setting a duty ratio at which the voltage of the second power supply line becomes the second voltage;
The power supply system according to any one of claims 1 to 3, wherein the voltage drop protection means maintains the switching element in an on state when a step-down function of the voltage conversion circuit is impaired. The electrical load includes a wireless device,
The power supply system according to claim 4, wherein the control unit sets a switching frequency of the switching element to a frequency different from a use frequency of the wireless device. The power supply circuit includes a switching power supply that steps down a power supply voltage from a power supply and outputs the first voltage to the first power supply line,
The power supply system according to any one of claims 1 to 5,
A vehicle comprising: a rotating electric machine that drives wheels by receiving power from the power source.   The vehicle according to claim 6, wherein the electric load includes a control device for the vehicle.

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