JP5842483B2 - Secondary battery power supply device and in-vehicle device - Google Patents

Description

  The present invention relates to a power supply device for a secondary battery that controls charging and discharging of a secondary battery as a backup power supply, and an on-vehicle device including the power supply device for the secondary battery.

  Generally, for example, in order to construct a backup system for an in-vehicle communication module mounted on a vehicle and communicating with an information center, a charging circuit for a secondary battery as a backup power source and a discharging circuit using the secondary battery as a power source These two circuits need to be configured.

JP 2004-96826 A

However, in the case of the above configuration, the number of parts for configuring the two circuits is large, and the printed wiring also needs to secure each power supply path. is there.
On the other hand, various methods such as a control method used in both directions of charge control and discharge control as in Patent Document 1 have been proposed as conventional techniques, but there is a problem that the control becomes complicated. That is, two control units are required for the DC-DC converter for charging and for the DC-DC converter for discharging. Even when the controller unit is shared, the voltage detection unit, current detection unit, and FET drive unit Since two circuits and a configuration for switching between the two circuits are necessary, the circuit becomes complicated and the cost is increased as a whole.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a secondary battery power supply device and an in-vehicle device capable of reducing the number of parts by simplifying the configuration.

According to the first aspect of the present invention, at the time of charging, the secondary battery can be charged with the target charging voltage by operating the charging control circuit and linearly controlling the energizing current of the first energizing element. On the other hand, at the time of discharging, the voltage of the secondary battery is transformed to the power supply voltage by operating the discharge control circuit to control on / off of the first energization element and the second energization element to form a DC-DC converter. Can do. In this case, since the first energization element is also used for charging and discharging, the number of parts can be reduced and the cost can be reduced.
According to invention of Claim 2, a DC-DC converter can be easily comprised by PWM control.
According to the invention of claim 3, since the current-voltage conversion circuit can be used in common for charge control and discharge control, the number of parts can be further reduced.

According to the invention of claim 4, when the power supply from the vehicle battery is cut off, the secondary battery can function reliably as a backup power source.
According to the invention of claim 5, by using a lithium ion battery having a high charging capability, it is possible to increase the time that can be backed up.
According to the invention of claim 6, since the on-voltage of the power MOSFET is low, it can be applied even when the difference between the power supply voltage and the voltage of the secondary battery is small.
According to invention of Claim 7, even if it is a case where the electric power feeding from a vehicle battery to an onboard equipment is cut off, an onboard equipment can be operated reliably.
According to invention of Claim 8, even if it is a case where the electric power feeding from a vehicle battery to an onboard equipment is cut off, an emergency call system can be operated reliably.

Schematic which shows typically the electric constitution of the power supply device in one Embodiment of this invention. Schematic diagram showing the configuration of the in-vehicle communication module

Hereinafter, an embodiment in which the present invention is applied to an in-vehicle communication module for emergency notification will be described with reference to the drawings.
FIG. 2 is a schematic diagram showing the configuration of an in-vehicle communication module (hereinafter referred to as “DCM”, which corresponds to an in-vehicle device). The DCM 1 is supplied with power from the vehicle battery 2, and a step-down DC-DC converter 3 (corresponding to a stabilized power supply) provided therein generates a stabilized DC 5 V (corresponding to a power supply voltage) from the power supply voltage of the vehicle battery 2. doing. The DC 5 V from the step-down DC-DC converter 3 functions as a power source for the DCM body 4 and also functions as a charging power source for a lithium ion battery 5 (corresponding to a secondary battery) connected in parallel to the DCM body 4. The lithium ion battery 5 is mounted as a backup power source for enabling emergency communication by supplying power to the DCM body 4 and operating it when the vehicle battery 2 cannot be used due to an accident or the like. In order to charge the lithium ion battery 5, the power supply device 6 generates a predetermined charging voltage (for example, 4.2 V) from DC 5 V by a charging function and supplies power to the lithium ion battery 5. In order to function as a backup power source, DC5V is generated from the voltage (for example, 3.7V) of the lithium ion battery 5 by a discharging function and is supplied to the DCM body 4.

  FIG. 1 is an electronic circuit diagram schematically showing a power supply device 6 and shows only main parts related to the present invention. A region surrounded by a broken line indicates that the area is constituted by the IC 7 and schematically shows a function constituted by an electronic circuit (not shown). The power supply device 6 includes a charge control circuit based on a linear control method and a discharge control circuit based on a synchronous rectification step-up DC-DC converter. The power supply device shares electronic components of a bidirectional control circuit. It is characterized by having formed. That is, the TOP-FET 8 (corresponding to the first energization element) which is a P-channel power MOSFET constituting the discharge control circuit is configured as follows so as to be used also as an FET constituting the charge control circuit. ing.

That is, the DC5V power supply line 9 is connected to the ground line 13 through a series circuit including a resistor 10 and a resistor 11 and a smoothing capacitor 12, and through a resistor 14, a TOP-FET 8, and an inductor 15. The lithium ion battery 5 is connected.
A detection voltage is output from a common connection point of the resistor 10 and the resistor 11, and the detection voltage is connected to be input to a first error amplifier circuit 16 schematically shown by an operational amplifier. The first error amplification circuit 16 amplifies the difference voltage between the detection voltage and the reference voltage 17 and outputs the amplified voltage to the controller 18.
A current-voltage conversion circuit 19 schematically shown by an operational amplifier is connected to both ends of the resistor 14. The current-voltage conversion circuit 19 converts a current flowing through the resistor 14 into a voltage, and is connected to a selection circuit 20 schematically indicated by a contact. The selection circuit 20 selectively outputs the voltage from the current-voltage conversion circuit 19 to the controller 18 or the second error amplification circuit 21.

The gate of the TOP-FET 8 is connected to the source via the resistor 22 and to the output terminal of the controller 18. The second error amplifier circuit 21 amplifies the voltage difference between the voltage from the current-voltage conversion circuit 19 and the reference voltage 23 in a state selected by the selection circuit 20 and outputs the amplified voltage to the base of the transistor 24.
A common connection point between the drain of the TOP-FET 8 and one end of the inductor 15 is connected to the ground line 13 via a BOTTOM-FET 20 (corresponding to a second energization element) which is an N-channel power MOSFET. The gate of the BOTTOM-FET 20 is connected to the output terminal of the controller 18.

  The other end of the inductor 15 is connected to the ground line 13 via a series circuit including a smoothing capacitor 25, a resistor 26 and a resistor 27. A detection voltage is output from a common connection point between the resistor 26 and the resistor 27, and the detection voltage is connected to be input to a third error amplification circuit 28 schematically shown by an operational amplifier. The third error amplifier circuit 28 amplifies the difference voltage between the detection voltage and the reference voltage 29 and outputs the amplified voltage to the base of the transistor 24. The collector of the transistor 24 is connected to the gate of the TOP-FET 8.

  The first to third error amplification circuits 16, 21, 28, the current-voltage conversion circuit 19, the selection circuit 20, the transistor 24, and the controller 18 are configured by an IC 7. The selection circuit 20 normally connects the current-voltage conversion circuit 19 to the second error amplification circuit 21, and the current-voltage conversion circuit 19 is connected to the controller 18 when an emergency notification ON signal is received from an external emergency notification device. Switch to connect to. The circuit constituting the IC 7 is not limited to the electronic circuit schematically shown in FIG.

In the above circuit, the object of the present invention is achieved by switching the gate of the TOP-FET 8 between the charge mode and the discharge mode.
(In charge mode)
In the charging mode, the current / voltage conversion circuit 19 is connected to the second error amplification circuit 21 by the selection circuit 19, and 4.2V is generated by the charge control function by the linear control method of the power supply device 6 to generate lithium ions. Charge the battery 5. In this case, the controller 18 keeps the BOTTOM-FET 20 in the OFF state, so that the BOTTOM-FET 20 is disconnected from the charge control circuit and becomes irrelevant. Further, since the inductor 15 operates with a direct current, it is only necessary to consider it as a direct current resistance, and the inductor component does not affect the circuit.

Here, regarding the charging current, the TOP-FET 8 is linearly controlled by the second error amplifying circuit 21 so that the detected voltage becomes the reference voltage 23, that is, the charging current becomes the target current. In addition, the charging voltage is linearly controlled by the third error amplification circuit 28 so that the detection voltage becomes the reference voltage 29, that is, the charging voltage becomes the target voltage. Constant voltage-constant current charging for the lithium ion battery 5 can be realized by such linear control.
As described above, in a normal state, the communication module power supply (DC5V) generated by the step-down DC-DC converter 3 from the power supply voltage from the vehicle battery 2 is used as an input power supply, and the constant voltage and constant current are 4 by the linear control method. The 2V lithium ion battery 5 is charged. However, the charging function is stopped when the lithium ion battery 5 is almost fully charged.

(During discharge mode)
If there is an accident in the vehicle, the vehicle battery 2 may not be used, so when receiving an emergency call on signal from the emergency call device, if charging is in progress, stop charging and then switch to discharge mode. The lithium ion battery 5 is operated as a backup power source by the discharge control function by the synchronous rectification step-up DC-DC converter of the device 6. In this case, the current-voltage conversion circuit 19 is connected to the controller 18 by switching the selection circuit 20 in response to the reception of the emergency notification ON signal. The controller 18 detects the voltage change from the current-voltage conversion circuit 19 and performs PWM (Pulse Width Modulation) control alternately on the TOP-FET 8 and the BOTTOM-FET 20 based on the timing at which the discharge current from the lithium ion battery 5 flows. Thus, the discharge function by the step-up DC-DC converter is operated. Thereby, the voltage of the power supply line 9 is controlled to be DC 5V.
As described above, the DCM main body 4 can be operated by operating the lithium ion battery 5 as a backup power source even in a state where power is not supplied from the vehicle battery 2.
If there is no problem after confirming the connection of the vehicle battery 2, the discharge mode is turned off, and an emergency call may be made by operating the communication module with DC 5 V generated from the vehicle battery 2 by the step-down DC-DC converter.

According to such an embodiment, the following effects can be produced.
Since the charge control circuit based on the linear control method in the charge mode and the discharge control circuit based on the synchronous rectification step-up DC-DC converter in the discharge mode are combined to form a bidirectional circuit, the power supply device 6 can be easily configured. Can be configured. In this case, since the current-voltage conversion circuit 19 in the charge mode and the discharge mode is used in common, the power supply device 6 can be configured more simply. In addition, since the circuit components share the TOP-FET 8 and the smoothing capacitors 12 and 25, the cost can be reduced by reducing the number of components. Furthermore, since the power supply device 6 has a common path, the pattern width of the printed wiring can be increased, and the resistance can be reduced.

(Other embodiments)
The present invention is not limited to the above embodiment, and can be modified or expanded as follows.
The vehicle battery 2 may be confirmed at the time of emergency notification, and the discharge mode may be made to function if there is a problem. If there is a problem with the vehicle battery 2, the step-up DC-DC converter with the lithium ion battery 5 as an input is turned on in the discharge mode to generate the power source DC5V of the DCM 1. With this power source DC5V, DCM1 operates and can make an emergency call.
As the secondary battery, a lead storage battery, a nickel metal hydride battery, or the like may be used.
The output voltage from the step-down DC-DC converter 3, that is, the voltage of the DCM main body 4 is not limited to 5V, and the charging voltage of the lithium ion battery 5 is not limited to 4.2V.
Depending on the relationship between the DCM body 4 and the voltage of the secondary battery, the function of the step-up DC-DC converter may be replaced with a step-down DC-DC converter or a step-up / step-down converter.
The present invention may be applied for theft tracking when the vehicle battery 2 is removed.
You may make it apply this invention to vehicle equipment other than DCM.

  In the drawings, 1 is a vehicle-mounted communication module (vehicle-mounted device), 2 is a vehicle battery, 5 is a lithium ion battery (secondary battery), 6 is a power supply device, 8 is a TOP-FET (first energization element), and 19 is a current. A voltage conversion circuit 20 is a BOTTOM-FET (second energization element).

Claims (8)

A stabilized power supply that generates a stabilized power supply voltage from a power supply voltage of the vehicle battery, and a secondary battery that functions as a backup power supply with a predetermined charging voltage obtained by transforming the power supply voltage when charging, and at the time of backup In the secondary battery power supply device that transforms the voltage of the secondary battery to the power supply voltage,
A first energization element that electrically connects the stabilized power source and the secondary battery in response to being turned on;
An inductor interposed between the first energization element and the secondary battery;
A second energization element that connects the secondary battery to a ground line via the inductor when turned on;
A charge control circuit that linearly controls an energization current of the first energization element so as to generate a target charging voltage from the power supply voltage during charging;
A discharge control circuit that transforms the voltage of the secondary battery into the power supply voltage by controlling on / off of the first energization element and the second energization element during discharge;
A selection circuit that selects and operates the charge control circuit in a normal time, and selects and operates the discharge control circuit according to an external command;
A power supply device for a secondary battery, comprising:   2. The secondary battery according to claim 1, wherein the discharge control circuit transforms the voltage of the secondary battery into the power supply voltage by PWM control of the first energization element and the second energization element. Battery power supply. A current-voltage conversion circuit that converts a current flowing through the first energization element into a voltage;
3. The power supply device for a secondary battery according to claim 1, wherein the charge control circuit and the discharge control circuit execute charge control and discharge control based on the voltage converted by the current-voltage conversion circuit. .   The secondary circuit according to any one of claims 1 to 3, wherein the selection circuit determines that a command has been received when a signal indicating the possibility that power supply from the vehicle battery has been cut off from the outside is received. Battery power supply.   The secondary battery power supply device according to claim 1, wherein the secondary battery is a lithium ion battery.   The secondary battery power supply device according to claim 1, wherein the first energization element is a power MOSFET.   A vehicle-mounted device comprising the secondary battery power supply device according to any one of claims 1 to 6. The signal indicating the possibility that power supply from the vehicle battery has been cut off is an emergency call on signal from the emergency call device,
8. The vehicle-mounted device according to claim 7, wherein an emergency call is transmitted to an information center when the emergency call on signal is received.

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