Power Supply Control Device

Abstract

This power supply control device is to be applied to a vehicle provided with an electrical device, a relay connected to the electrical device, a first power source that enables operation of the relay, and a second power source that discharges electricity to the electrical device through the relay. The power supply control device comprises: a DCDC converter that supplies power from the second power source to the relay and that serves as a backup for the first power source; a third power source that is charged by the first power source and that outputs the charged power to the relay; and a control unit that controls operations of the DCDC converter and the second power source. The control unit turns the DCDC converter off when the voltage of the third power source is equal to or higher than a first threshold value, and turns the DCDC converter on when the voltage of the third power source is equal to or lower than a second threshold value that is lower than the first threshold value.

Description

[Technical Field]

[0001] The present invention relates to a power supply control device. [Background technology]

[0002] Conventionally, configurations for backing up a power supply mounted on a vehicle have been known. For example, a configuration has been disclosed in which a DC-DC converter is used to generate a backup power supply in an in-vehicle system with low current consumption (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-348769 Summary of the Invention [Problem to be solved by the invention]

[0004] When a DC-DC converter is operated, electrical noise such as EMI (Electro Magnetic Interference) is generated in electrical equipment, which may affect electrical equipment that uses wireless communication such as radios and televisions. Therefore, an object of the present invention is to provide a power supply control device that can suppress electrical noise caused by the operation of a DC-DC converter. [Means for solving the problem]

[0005] The power supply control device of the present invention is applied to a vehicle equipped with an electrical device, a relay connected to the electrical device, a first power supply that enables the relay to operate, and a second power supply that discharges power to the electrical device via the relay. The power supply control device includes a DC-DC converter that supplies power from the second power supply to the relay as a backup for the first power supply, a third power supply that is charged by the first power supply and outputs the charged power to the relay, and a control unit that controls the operation of the DC-DC converter and the second power supply. The control unit turns off the DC-DC converter when the voltage of the third power supply is equal to or higher than a first threshold, and turns on the DC-DC converter when the voltage of the third power supply is equal to or lower than a second threshold that is lower than the first threshold. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a power supply control device that can suppress electrical noise caused by the operation of a DC-DC converter used as a component of a backup power supply. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a circuit diagram of a vehicle electrical system to which a power supply control device according to an embodiment of the present invention is applied; [Figure 2] 1. FIG. 4 is a graph showing charging (boosting) and discharging (decreasing) of a capacitor that forms a third power supply in the power supply control device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a vehicle electrical system to which a power supply control device according to the present invention is applied will be described with reference to FIG.

[0009] The vehicle electrical system 100 includes an inverter 101, which is an electrical device, a relay 102 connected to the inverter 101, a lead battery 110 (an example of a first power source) that operates the relay 102 with a first power P1, a lithium ion battery 120 (an example of a second power source) that discharges to the inverter 101 via the relay 102, and a power supply control device 10. Examples of the electrical devices include a radio or television that uses wireless communication, as well as a car navigation system. The vehicle may be an EV, HV, PHV, PHEV, or FCV (hereinafter also referred to as an "EV or the like").

[0010] The DC-DC converter 11 is capable of outputting a second power P2 supplied from the lithium ion battery 120 for excitation to operate the relay 102. The second power P2 is a backup function in case the first power P1 of the lead battery 110 fails, and is therefore configured as a circuit capable of charging the capacitor 12 instead of the lead battery 110.

[0011] The relay 102 can switch a large DC current, for example, by normally open operation, in which the contacts are closed only when power is applied. If the relay 102 is disconnected due to an unexpected interruption of the excitation current, the large DC current will be momentarily interrupted, generating a high voltage that may damage the inverter 101. Therefore, the relay 102 must prevent the excitation current from being unexpectedly interrupted. The power supply control device 10 is provided with a backup power supply to prevent such an event.

[0012] If the lead battery 110 that supplies the excitation current to the relay 102 fails due to a dead battery or other reason, the second power P2 connected to the lead battery 110 via an OR circuit formed by diodes 4 and 2 is supplied as a backup in place of the failed first power P1. However, if the first power P1 fails, it takes several tens of milliseconds for the DC-DC converter 11 to be turned on and for the second power P2 to be sufficiently supplied. As a result, the excitation current of the relay 102 is not interrupted, and the third power P3 is supplied from the capacitor 12, so that the ON state due to the excitation of the relay 102 continues.

[0013] However, the third power P3 from the capacitor 12 can only be sustained for a few seconds at most. In contrast, if the DC-DC converter 11 is turned on, the second power P2 can be supplied without delay from the lithium ion battery 120. Here, the MPU 13 detects that the lead battery 110 has failed due to a dead battery or the like, and turns on the DC-DC converter 11. As a result, the second power P2 is supplied from the lithium ion battery 120, which has sufficient capacity.

[0014] A latching relay is suitable for the relay 102. A latching relay does not require a continuous flow of excitation current, and can maintain its state by adding a signal current only when switching, resulting in a greater power saving effect. The first power P1 is power for keeping the relay 102 ON. The voltage of the first power P1 is, for example, 12V to 13.8V, and turns on the transistor 8 to form an excitation drive circuit. The transistor 8 is opened and closed by a relay control signal from the MPU 13 (an example of a control unit).

[0015] The power supply control device 10 has a DC-DC converter 11, a capacitor 12 (an example of a third power supply), a control unit (e.g., a micro-processing unit, hereinafter also referred to as "MPU") 13, a notification unit 14, an input unit 15, a cell voltage measurement IC (CCIC) 17, and a power supply IC 18. A BAT terminal of the power supply IC 18 is connected to the positive terminal of a lead battery 110, and power is constantly supplied via a diode 1. An IG terminal 19 of the power supply IC 18 is connected to a vehicle operation means (not shown) and receives an operation signal.

[0016] The MPU (control unit) 13 is a type of processor also called a microprocessor, and is implemented on a microchip. The MPU 13 measures the voltage of the lead battery 110 related to the first power P1 and the voltage related to the second power P2 supplied from the lithium ion battery 120, and controls the operations of the relay 102, the lithium ion battery 120, and the DC-DC converter 11 according to the measurement results.

[0017] MPU 13 is the core of power supply control device 10, and in the case of a one-chip microcomputer with a minimum drive power of 7V, for example, the circuit configuration is such that power is always supplied stably and reliably from lead battery 110 via diode 1 and power supply IC 18. However, power supply control device 10 also assumes the possibility of a failure of lead battery 110. In the event of a failure of lead battery 110, the circuit configuration of diodes 2 to 4 will back up the failed lead battery 110 as will be described later.

[0018] 2 under conditions described below, thereby controlling the operation of the lithium ion battery 120. The MPU 13 turns on the DC-DC converter 11 when the voltage of the third power P3 is equal to or lower than a second threshold V2 (10 V) that is lower than the first threshold V1 (11 V).

[0019] The MPU 13 alternately repeats a charging state and a charging pause state so that the capacitor 12 is intermittently charged from the lithium ion battery 120. That is, the circuit is configured so that the second power P2 supplied from the lithium ion battery 120 can charge the capacitor 12 as a backup function in case the lead battery 110 fails.

[0020] The cell voltage measurement IC (hereinafter also referred to as "CCIC") 17 not only measures the cell voltages of the multiple cells that make up the lithium-ion battery 120, but many also function as a cell controller that equalizes the voltages of each cell. The CCIC 17 is charged to a high voltage, but its high-voltage section is insulated by the isolated photocouplers 5 and 6 and the isolated communication IC 7 while exchanging control signals with the MPU 13. This circuit configuration also protects the 7V-powered single-chip microcontroller from high-voltage shocks.

[0021] The DC-DC converter 11 can output a second power P2 from the lithium ion battery 120 to the relay 102 as a backup for the lead battery 110. The second power P2 is power for keeping the relay 102 ON as a backup for a failed lead battery 110. The voltage of the second power P2 is, for example, 10 to 11 V.

[0022] The capacitor 12 is charged by the lead battery 110 and is configured to output a third power P3 to the relay 102. The third power P3 is used as a backup for the failed lead battery 110 until the DC-DC converter 11 is started, and is used to keep the relay 102 ON. The voltage of the third power P3 is, for example, 10V to 11V.

[0023] 1, the MPU 13 controls the operation of the DC-DC converter 11 and the lithium-ion battery 120 while exchanging control signals with the CCIC 17 and others. The MPU 13 performs voltage measurement (S1) to monitor the backup voltage in preparation for a possible failure of the lead battery 110, relay control (S2), shutdown control of the DC / DC converter (S3), shutdown control of the CCIC (S4), and voltage measurement (S5) to monitor the lead battery voltage. The lithium-ion battery 120 may be replaced by, for example, a nickel-metal hydride battery, and the lead battery 110 may be replaced by, for example, a nickel-metal hydride battery or an alkaline battery.

[0024] The operation of the power supply control device 10 will be described with reference to Figures 1 and 2. Figure 2 is a graph showing the charging (boosting) and discharging (bucking) of the capacitor 12. When the DC-DC converter 11 is turned on to charge the capacitor 12, the MPU 13 turns off the DC-DC converter 11 to stop charging the capacitor 12 if the voltage of the second power P2 is equal to or higher than the first threshold V1.

[0025] 2, the first threshold V1 is, for example, 11 V. When the voltage of the capacitor 12, i.e., the voltage of the third power P3, is equal to or lower than a second threshold V2 (for example, 10 V) that is lower than the first threshold V1, the MPU 13 turns on the DC-DC converter 11 to resume charging of the capacitor 12.

[0026] Furthermore, the MPU 13 alternately switches the capacitor 12 between a charging state and a charging pause state, thereby intermittently charging the capacitor 12 from the lithium ion battery 120. That is, the circuit of Fig. 1 is configured so that the second power P2 supplied from the lithium ion battery 120 can charge the capacitor 12 as a backup function in case the lead battery 110 fails.

[0027] Furthermore, if the lead battery 110 that supplies the excitation current to the relay 102 fails due to a dead battery or the like, the third power P3 is instantaneously supplied to the lead battery 110 from the capacitor 12 that is connected to the OR circuit of the diodes 2 and 4 in place of the failed first power P1, thereby keeping the relay 102 in the ON state.

[0028] Furthermore, the MPU 13 turns off the DC-DC converter 11 when the voltage of the third power P3 is equal to or higher than the first threshold V1, and turns on the DC-DC converter 11 when the voltage of the third power P3 is equal to or lower than the second threshold V2.

[0029] The notification unit 14 notifies of an abnormality in the lead battery 110 when the second power P2 is output for more than a predetermined time. An abnormality in the lead battery 110 may be, for example, a failure or a disconnection. The notification unit 14 outputs the abnormality via an output device such as a monitor or speaker mounted on the vehicle. The input unit 15 allows input for changing the first threshold value V1 and the second threshold value V2.

[0030] Unless the lead battery 110 fails or the like, the contacts of the relay 102 are always kept closed by the first power P1 from the lead battery 110. The first power P1 is power for keeping the relay 102 ON, and its voltage is set to 12 V. The lithium ion battery 120 supplies power to the inverter 101 via the relay 102 in the ON state.

[0031] The lithium ion battery 120 outputs a second power P2 stepped down by the DC-DC converter 11 under the control of the MPU 13. The lithium ion battery 120 does not discharge to the DC-DC converter 11 until the lead battery 110 fails. The second power P2 is a power for keeping the relay 102 ON as a backup for the failed lead battery 110, and its voltage is set between 10V and 11V.

[0032] The voltage value (10V to 11V) of the second power P2 is set lower than the voltage value (12V) of the first power P1. The path for supplying the excitation current to the relay 102 forms an OR circuit by connecting the cathodes of two diodes 2 and 4. The first power P1 is supplied to the anode of one diode 2 of this OR circuit, and the second power P2 is supplied to the anode of the other diode 4. Therefore, this OR circuit backs up the first power P1 with the second power P2, preventing a power outage of the excitation current of the relay 102.

[0033] The capacitor 12 is charged by the second power P2, which is the output of the DC-DC converter 11. The capacitor 12 outputs a third power P3 to the relay 102. The third power P3 is a power for keeping the relay 102 ON until the DC-DC converter 11 starts up as a backup for the failed lead battery 110, and its voltage is set between 10 and 11 V.

[0034] The capacitor 12 is charged by the second power P2 output from the DC-DC converter 11 while being boosted from the second threshold V2 of 10 V to the first threshold V1 of 11 V in a short time, for example, of a few seconds. After that, the DC-DC converter 11 is turned off based on the control of the MPU 13, and the charging of the capacitor 12 by the second power P2 stops. Therefore, the capacitor 12 is discharged while the voltage gradually drops from the first threshold V1 of 11 V to the second threshold V2 of 10 V over a few minutes due to natural discharge or the like.

[0035] When the voltage value of the capacitor 12 drops, the DC-DC converter 11 is turned on (restarted) based on the control of the MPU 13. As a result, the capacitor 12 is again charged by the second power P2 while the voltage is increased from the second threshold V2 of 10 V to the first threshold V1 of 11 V in a short period of time, for example, a few seconds.

[0036] Only for this short period of a few seconds does discharge from the lead battery 110 to the capacitor 12 resume. As a result, discharge from the lead battery 110 to the capacitor 12 is performed only for the short period of time while the voltage value of the capacitor 12 rises from 10V to 11V.

[0037] When the first power P1 is cut off due to a failure of the lead battery 110, first, the third power P3 is supplied from the capacitor 12 to the relay 102. Next, the second power P2 is supplied from the DC-DC converter 11 to the relay 102. That is, for a short time until the DC-DC converter 11 starts up, the capacitor 12 functions as a backup power source for the lead battery 110. Thereafter, the lithium ion battery 120 functions as a backup power source for the lead battery 110.

[0038] 2, the DC-DC converter 11 is activated for only a very short time. Therefore, the EMI noise caused by the operation of the DC-DC converter 11 is generated for only a very short time, and the EMI noise does not have much effect on in-vehicle devices such as radios and televisions.

[0039] Next, the operation and effects of the power supply control device 10 will be described. [1] The lead battery 110 supplies a first power P1. The first power P1 is supplied for excitation to operate the relay 102, for driving the MPU 13, which is similar to a computer, and for driving part of the electrical equipment. The part of the electrical equipment referred to here may be considered to be a 12V electrical component. On the other hand, the lithium ion battery 120 is, for example, a 40V storage battery configured in a series-parallel configuration. The capacitor 12 is charged by the lead battery 110 and is configured to be able to output a third power P3 for excitation to operate the relay 102.

[0040] The second power P2, which has a certain capacity, replaces the first power P1 of the lead battery 110, and continues to energize the relay 102 to keep it in the ON state, drive the MPU 13, and drive the inverter 101 for a long time. A second threshold V2 (10V) is set at a level that detects a failure of the lead battery 110 (12V to 13.8V). In this state, for example, in the case of an electric vehicle or the like, the vehicle should continue to be driven even if it is not necessary to drive, and the lead battery 110 should be charged, or the lead battery 110 should be replaced with a new one at a repair shop or the like, or supplementary charging should be performed.

[0041] In this way, in addition to when the lead battery 110 fails due to a dead battery or the like, only charging is output intermittently for a very short time to replenish the voltage drop due to natural discharge of the capacitor 12, as shown in Figure 2. If the DC-DC converter 11 is turned on only for such a short time, the electrical noise generated by it is considered to be tolerable.

[0042] In other words, during normal operation of a vehicle equipped with the power supply control device 10, the DC-DC converter 11 is mostly turned off as shown in Fig. 2, so no electrical noise is generated. Therefore, the power supply control device 10 can suppress electrical noise caused by the operation of the DC-DC converter 11 used as a component of the backup power supply.

[0043] [2] In [1] above, the power supply control device 10 is applied to a vehicle equipped with a normally open type relay 102, which is highly versatile and configured so that the contacts are closed only when power is applied. In such a power supply control device 10, if a failure occurs in the electrical system, the ON state caused by the excitation of the relay 102 can no longer be maintained. The relay 102 is inserted between the lithium ion battery 120 and the inverter 101, and is basically safe because it cuts off the main current, such as a large DC current, by normally open operation, for example.

[0044] [3] In [1] above, the power supply control device 10 may be applied to a vehicle equipped with a normally closed type relay 102 (same reference numeral) that is configured so that the contacts are open only when power is applied. Such a power supply control device 10 can be easily realized by reprogramming the MPU 13 to reverse the relay control logic and output it. Alternatively, this can be easily realized by reconfiguring the circuit to reverse the ON / OFF operation using the excitation drive circuit with the transistor 8, or by inserting a NOT operation circuit (not shown) to reverse the ON / OFF operation of the excitation circuit.

[0045] Furthermore, the operation type of the relay 102 (same symbol) may be a latch type, which can maintain operation after switching without an excitation current by inputting only a switching signal. In this case, the excitation drive circuit using the transistor 8 is not necessary, and the program can be changed so that the relay control logic of the MPU 13 outputs only a switching signal and the ON / OFF state of the relay 102 is monitored by the MPU 13. In this way, the power supply control device 10 can be applied to a wide range of embodiments without limiting the operation type of the relay 102.

[0046] [4] In any of the above [1] to [3], the power supply control device 10 further includes a notification unit 14 that notifies predetermined information. When the second power P2 of the DC-DC converter 11 is output for a predetermined time or longer, the notification unit 14 notifies, for example, a vehicle occupant that an abnormality has occurred in the lead battery 110. With this configuration, for example, a vehicle occupant can recognize that an abnormality has occurred in the lead battery 110.

[0047] Furthermore, if an abnormality occurs in the lead battery 110, the vehicle occupant can take action, such as consulting a vehicle repair shop. If the normal state continues and there is no abnormality in the lead battery 110, the second power P2 from the lithium ion battery 120 is only output intermittently for a very short time to replenish the voltage drop due to natural discharge of the capacitor 12, as shown in Fig. 2. On the other hand, if an abnormality occurs in the lead battery 110, the notification unit 14 will notify the vehicle occupant, for example, so that the vehicle occupant can discover the abnormality early and prevent the situation from becoming serious.

[0048] [5] In any of the above [1] to [4], the MPU 13 operates on the first power P1. The MPU 13 is often a one-chip microcomputer with a minimum drive power of 7V, for example. Also, the first power P1 from the lead battery 110 is often supplied at 12V to 13.8V. In such cases, the second power P2 from the lithium ion battery 120 (e.g., 40V) is too high a voltage to drive the MPU 13 (e.g., about 10V), and therefore a DC voltage conversion function is required.

[0049] Therefore, the power supply control device 10 directly operates the MPU 13 using the first power P1, which does not require the intervention of a DC voltage conversion function, which is simpler and easier. As a result, the power supply control device 10 can reduce the opportunities for the DC-DC converter 11 to operate, thereby suppressing electrical noise caused by that operation.

[0050] The power supply control device 10 configured as described above can be operated by the lead battery 110 without receiving power from the lithium ion battery 120 unless the lead battery 110 fails. As a result, the DC-DC converter 11 operates less frequently, thereby suppressing electrical noise caused by its operation.

[0051] [6] In any of the above [1] to [5], the device further includes an input unit 15 that can change at least one of the first threshold V1 (11 V) and the second threshold V2 (10 V). With this configuration, at least one of the first threshold V1 and the second threshold V2 can be changed in consideration of the frequency of ON / OFF control of the DC-DC converter 11 by the MPU 13. The advantages of changing this are as follows.

[0052] If the power supply control device 10 changes the threshold value to a lower value, the DC-DC converter 11 operates less frequently, thereby suppressing electrical noise caused by the operation of the DC-DC converter 11. In this way, the threshold value can be changed to a lower value if the conditions are met to ease the backup system for the lead battery 110 while maintaining the availability of the inverter 101.

[0053] The following are examples of conditions that may be considered to relax the backup system for the lead battery 110. Current EVs and the like are equipped with not only the lithium-ion battery 120 but also the lead battery 110, which has a much lower voltage and smaller capacity. This lead battery 110 is still indispensable as a power source for electrical components other than the main motor, and although it may not be possible to reduce its use suddenly, it is possible that the degree of dependence on it may be gradually reduced with expected technological innovation.

[0054] As a specific example of reducing the dependency, first, if not only the lights powered by the lead battery 110 are replaced with LEDs but also the relay 102 is replaced with a latching type, the excitation current becomes unnecessary, and energy saving for the lead battery 110 is promoted, thereby reducing the dependency on the battery. Also, since an EV does not have an internal combustion engine that generates heat, the installation environment of the lead battery 110 becomes low temperature. As a result, deterioration of the lead battery 110 is suppressed and reliability is improved.

[0055] Furthermore, it is conceivable that the lead battery 110 itself will become more highly functional. Alternatively, it is conceivable that the power supply voltage of in-vehicle electrical equipment will gradually be unified from the current rated output of 12V to 13.8V of the lead battery 110 to a voltage that matches the specifications of the lithium-ion battery 120. If the degree of dependence on the lead battery 110 is reduced in this way, it is preferable that the power supply control device 10 applied to an EV or the like allows a worker at a repair shop to change the above threshold value to a lower value via the input unit 15. [Explanation of symbols]

[0056] 1 to 4: diodes, 5, 6: isolated photocouplers, 7: isolated communication IC, 8: transistor, 10: power supply control device, 11: DC-DC converter, 12: capacitor (an example of a third power supply), 13: MPU (an example of a control unit), 14: alarm unit, 15: input unit, 17: cell voltage measurement IC (CCIC), 18: power supply IC, 19: IG terminal, 100: vehicle electrical system, 101: inverter (and other electrical equipment using wireless communication), 102: relay, 110: lead battery (an example of a first power supply), 120: lithium-ion battery (an example of a second power supply), P1: first power: power (voltage 12V to 13.8V) for keeping the relay 102 ON, P2: second power: power (voltage 10 to 11V) for keeping the relay 102 ON as a backup for a failed lead battery 110, P3 Third power: Power (voltage 10 to 11 V) used as a backup for the failed lead battery 110 until the DC-DC converter 11 starts up, to keep the relay 102 ON. V1: First threshold (11 V), V2: Second threshold (10 V)

Claims

1. Electrical equipment and a relay connected to the electrical device; a first power source for enabling the relay; a second power source that discharges to the electrical device through the relay; A power supply control device applied to a vehicle equipped with a DC-DC converter that supplies power from the second power supply to the relay as a backup for the first power supply; a third power source that is charged by the first power source and outputs the charged power to the relay; a control unit that controls operations of the DC-DC converter and the second power supply; and The control unit When the voltage of the third power supply is equal to or higher than a first threshold, the DC-DC converter is turned off; When the voltage of the third power supply is equal to or lower than a second threshold value that is lower than the first threshold value, the DC-DC converter is turned on. Power control device.

2. The present invention is applied to a vehicle having a relay configured to close contacts only when energized. The power supply control device according to claim 1 .

3. The present invention is applied to a vehicle having a relay configured such that the contacts are open only when the relay is energized. The power supply control device according to claim 1 .

4. Further comprising a notification unit that notifies predetermined information, The notification unit notifies of an abnormality in the first power supply when the DC-DC converter is turned on for a predetermined time or longer. The power supply control device according to any one of claims 1 to 3.

5. The control unit is operated by the first power source. The power supply control device according to any one of claims 1 to 3.

6. further comprising an input unit capable of changing at least one of the first threshold value and the second threshold value; The power supply control device according to any one of claims 1 to 3.

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