JPH10290526A - Power unit for on-vehicle computer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a peripheral device for personal computer, such as the PC card, etc., normally usable for an on-vehicle computer. SOLUTION: In a power unit which generates a constant DC voltage by means of a switching regulator 40 and supplies the voltage to an on-vehicle computer, a comparator 54 discriminates whether or not the power supply to the regulator 40 is discontinued (turned off) from the input voltage VACC to the regulator 40. When the comparator 54 discriminates the turning-off of the power supply, the power supply voltage Vcc to the on-vehicle computer is quickly lowered and, at the same time, the operation of the regulator 40 is stopped for a prescribed period of time by outputting a high-level signal from an AND circuit 60 during a fixed period of time (T2-T1) after a fixed period of time (T1) required for data backup has elapsed from the discrimination of the turning-off of the power supply by operating timers 56 and 58. Consequently, a PC card becomes usable for the on-vehicle computer, because the fluctuating characteristic of the power supply voltage when the power unit is turned off can be matched to the power supply standard of the PC card.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for receiving a power supply from a vehicle power supply and supplying a constant voltage to a vehicle computer.

[0002]

2. Description of the Related Art Conventionally, for example, a navigation device that displays a road map and a scheduled route on a display device to guide a vehicle occupant to travel has been proposed.
2. Description of the Related Art A vehicle equipped with a computer for information processing is known.

[0003] In recent years, such computers (vehicle-mounted computers) mounted on vehicles include, for example, PCs.
MCIA (Personal Computer Memory Card Internatio)
It is demanded to be able to use a peripheral device for function expansion (hereinafter, referred to as a personal computer peripheral device) used in a general-purpose personal computer, such as a PC card conforming to the nal association (nalAssociation) standard.

However, in the conventional vehicle-mounted computer, there is a problem that the change characteristic of the power supply voltage does not conform to the power supply standard of the personal computer peripheral device, and the personal computer peripheral device cannot be used in the vehicle-mounted computer. . For example, in the PCMCIA standard, as shown in FIG. 4, the fall time tpf until the power supply voltage Vcc changes from 90% of the rated voltage V90 to 10% of the rated voltage V10 when the power is turned off, and the power supply voltage Vcc is used. PC with decline
The time from when the card temporarily stops operating until the power supply voltage Vcc rises and the PC card restarts operation (off time when the power supply voltage Vcc becomes equal to or less than Voff) toff, and after the power is turned on, the power supply voltage Vcc is rated to the rated value. The rise time tpf until the voltage value changes from 10% voltage value V10 to 90% of the rated voltage value V90 is specified to be a predetermined time. Therefore, a power supply for supplying power to a PC card conforming to the PCMCIA standard must be configured to satisfy the power supply standard.

[0005] However, the power supply of the vehicle-mounted computer is
Since the output voltage of the vehicle-mounted power supply (generally a battery) varies greatly depending on the operating state of other devices such as an engine and an air conditioner, and the instantaneous interruption of the vehicle-mounted power supply tends to occur, a large capacitance is required for the power supply voltage stabilizing capacitor. The use of the power supply prevents a sudden change in the power supply voltage inside the vehicle-mounted computer.

As a result, in a vehicle-mounted computer, the fall time of the power supply voltage after the power supply is cut off is prolonged, and when a personal computer peripheral device such as a PC card is used, the power supply standard cannot be satisfied. There was a problem that it could not operate normally.

The present invention has been made in view of such a problem, and has as its object to enable a vehicle-mounted computer to normally use a personal computer peripheral device such as a PC card.

[0008]

According to the first aspect of the present invention, there is provided a power supply device for an in-vehicle computer which receives a power supply from an in-vehicle power supply and generates a constant DC voltage. A constant voltage power supply circuit for generating and supplying the DC constant voltage to the in-vehicle computer is provided.

Then, the power cutoff detecting means detects the cutoff of the power supply from the vehicle-mounted power supply to the constant voltage power supply circuit, and when the cutoff of the power supply is detected by the power cutoff detecting means, the voltage drop characteristic control means. Discharges the charge accumulated in the constant voltage supply path from the constant voltage power supply to the on-board computer,
The supply voltage to the in-vehicle computer is reduced at a predetermined slope.

When the power cutoff detecting means detects the cutoff of the power supply from the onboard power supply to the constant voltage power supply circuit, the constant voltage supply prohibiting means sets the time during which the onboard computer stops operating as the supply voltage decreases. Until the time reaches a predetermined time, the operation of the constant voltage power supply circuit is stopped.

Therefore, according to the power supply device of the present invention, the power supply from the vehicle-mounted power supply to the constant-voltage power supply circuit is cut off, and the fall time when the supply voltage from the constant-voltage power supply circuit to the vehicle-mounted computer decreases is reduced. Even when the power supply cutoff time is short (for example, when the power supply is momentarily interrupted), the constant voltage supply prohibition means can control the on-board computer. The operation can be stopped for a certain time or more.

Therefore, according to the power supply device of the present invention, even when the on-vehicle computer is provided with a personal computer peripheral device such as the PC card, the supply voltage from the constant voltage power supply circuit to the on-vehicle computer is reduced. Characteristic, specifically, the fall time when the power is turned off (the fall time tpf described above in the case of a PC card) and the operation stop time of the in-vehicle computer after the power is cut off (the off time toff in the case of a PC card). Can be adapted to the power supply standard of the personal computer peripheral device provided in the in-vehicle computer, and the in-vehicle computer can use the personal computer peripheral device without any problem.

Therefore, according to the present invention, the functions of the on-vehicle computer can be expanded easily and without significantly increasing the cost by using the peripheral device for the personal computer. Here, the voltage drop characteristic control means determines the fall time during which the power supply from the vehicle-mounted power supply to the constant-voltage power supply circuit is cut off and the supply voltage from the constant-voltage power supply circuit to the vehicle-mounted computer falls to the power supply standard of the vehicle-mounted computer. It is for adaptation. For this purpose, the voltage drop characteristic control means may be configured so as to immediately reduce the supply voltage to the on-vehicle computer when the power supply cutoff detection means detects the cutoff of the power supply.

However, when the voltage drop characteristic control means is configured in this way, the on-board computer stops operating promptly due to the drop in the supply voltage, and the data used so far cannot be backed up. is there. Therefore, the voltage drop characteristic control means is described in claim 2
As described in, when the power supply cutoff is detected by the power supply cutoff detection means, thereafter, a timekeeping means for clocking a backup time required for the vehicle-mounted computer to back up data is provided. It is desirable that the supply voltage to the in-vehicle computer is reduced after the time is measured.

That is, the on-board computer is generally configured so that when the power supply voltage is reduced, the data used so far is written to the backup RAM or the like (ie, backed up) before the operation stops. Therefore, after the power supply cutoff is detected by the power supply cutoff detecting means and the supply voltage from the constant voltage power supply circuit to the onboard computer begins to drop, the onboard computer must wait for the data backup to complete. The control to lower the voltage is prohibited. With this configuration of the voltage drop characteristic control means, the data backup before the operation of the vehicle-mounted computer is stopped can be reliably executed, and the function of the vehicle-mounted computer is not reduced.

The power cutoff detecting means only needs to be able to detect the cutoff of the power supply from the vehicle-mounted power supply to the constant voltage power supply circuit. For example, when the output voltage from the constant voltage power supply circuit falls below a predetermined voltage, It may be configured to detect interruption of supply. However, when the power cutoff detecting means is configured in this way, the operation stop of the constant voltage power supply circuit (in other words, a decrease in the supply voltage to the onboard computer) due to the cutoff of the power supply from the onboard power supply to the constant voltage power supply circuit is promptly made. Can no longer be detected.

Therefore, the power supply cutoff detecting means is configured to cut off the power supply when the input voltage from the vehicle-mounted power supply to the constant voltage power supply circuit becomes equal to or lower than a predetermined determination voltage. Is desirably configured to detect In other words, if the power cutoff detecting means is configured as described above, the constant voltage power supply circuit can detect the cutoff of the power supply just before stopping the operation due to the cutoff of the power supply from the vehicle-mounted power supply. By operating the control means promptly, it becomes possible to control the lowering characteristic (fall time) of the supply voltage to the in-vehicle computer better.

Further, in particular, the voltage drop characteristic control means and the constant voltage supply prohibiting means are provided with a voltage drop characteristic of the supply voltage to the vehicle-mounted computer and an operation stop time of the constant voltage supply circuit, respectively. , PCMCIA standard compliant P
If it is configured to conform to the power standard of C card, PC
It is preferable because various functions such as a memory, a modem, and a hard disk, which are put into practical use as a card, can be added to the vehicle-mounted computer very easily, and the functions of the vehicle-mounted computer can be more easily expanded.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a block diagram showing the configuration of the entire vehicle navigation apparatus according to the embodiment to which the present invention is applied.

As shown in FIG. 2, the navigation device of the present embodiment receives a transmission radio wave from an artificial satellite, detects a current position and a traveling speed of a vehicle, a GPS receiver 2, and stores a road map and facility information. A CD-ROM changer 4 for selectively reading map data and facility information from the plurality of CD-ROMs provided, and a display device 6 for displaying travel guidance images such as road maps, scheduled travel routes, and facility information. .
The display device 6 includes a display unit 6a such as a CRT and an LCD.
An operation unit 6b for operation input arranged around the display screen of the display unit 6a. In addition, navigation devices include
A wireless telephone terminal device (hereinafter referred to as telephone terminal) 8 for reading road conditions and the like from various information terminals using a public telephone line is also provided. These units are connected to a vehicle-mounted computer 10 for navigation.

The in-vehicle computer 10 includes an arithmetic processing unit 20 including a CPU and the like, and includes a GPS receiver 2, a CD-RO
The M changer 4 and the telephone terminal 8 are connected to the arithmetic processing unit 20 via dedicated interfaces I / Fs 12, 14, and 16, respectively. The on-vehicle computer 10 has a video RAM (VRAM) 22, VR for storing the image data for display generated by the arithmetic processing unit 20.
A video signal output unit 24 that converts image data stored in the AM 22 into a video signal for display and outputs the video signal, and an arithmetic processing unit 20
Is provided with an audio signal output unit 26 that converts the audio data for audio guidance generated by the above into an analog audio signal and outputs the analog audio signal to audio equipment such as an amplifier and a speaker separately mounted on the vehicle. Further, the vehicle-mounted computer 10 is provided with a PC card mounting unit 28 so that a PC card 30 conforming to the PCMCIA standard can be used.
Connected to the built-in interface.

The arithmetic processing unit 20 is connected to the GPS receiver 2
From the CD-ROM changer 4 to read out map data including the current location, display a road map including the current location on the display unit 6a, and guide the driver on a planned route. In addition to executing navigation control, it reads various information such as road conditions from a desired information terminal via a telephone terminal 8 in accordance with a command input from a driver or the like via an operation unit 6b, or a PC card mounting unit. A predetermined data processing is performed by accessing the PC card 30 attached to the PC card 28.

For this reason, according to the navigation device of this embodiment, the vehicle occupant, for example,
By installing a memory card such as a flash memory as the PC card 30, the telephone number of the information terminal from which information is read out via the telephone terminal 8 can be stored in the memory card, or various data stored in the memory card can be stored. Can be read.

Next, the in-vehicle computer 10 receives a power supply from the battery 32 as an in-vehicle power supply, generates a DC constant voltage, and uses the same as the internal power supply voltage Vcc of the in-vehicle computer 10. And a power supply unit 34 for supplying each functional circuit inside the vehicle-mounted computer 10.

The power supply unit 34 is used when the accessory switch 36, which is one of the key switches of the vehicle, is turned on (that is, when the vehicle power supply is turned on). When the accessory switch 36 is turned off, the generation of the DC constant voltage is stopped, and the power supply to each of the functional circuits is cut off.

For this reason, the battery voltage VACC (hereinafter, referred to as a first battery voltage) is input to the power supply unit 34 via the accessory switch 36. In this embodiment, the internal power supply voltage Vcc when the power supply is turned off is set. In order to control the change characteristics, the battery 32 is controlled separately from the first battery voltage VACC.
The battery voltage VBT (hereinafter, referred to as a second battery voltage) is directly input from the battery 32 via a power supply path directly connected to the power supply.

Hereinafter, the configuration of the power supply section 34 will be described with reference to FIG. The power supply unit 34 corresponds to the power supply device of the present invention, and includes a switching regulator 40 as a constant voltage power supply circuit for receiving the first battery voltage VACC and generating a DC constant voltage, and a first battery voltage VACC.
And a power supply control unit 50 that detects a cutoff of power supply from the battery 32 to the switching regulator 40 from the voltage level of the power supply and controls a change characteristic of the internal power supply voltage Vcc.

The DC constant voltage generated by the switching regulator 40 is supplied as an internal power supply voltage Vcc to each of the above-described functional circuits. For this purpose, a constant voltage supply path includes disturbance noise superimposed on the constant voltage supply path. A capacitor Co for noise absorption and voltage stabilization is connected so that each functional circuit does not malfunction.

For this reason, the switching regulator 40
Even if the supply of the first battery voltage VACC to the switching regulator 40 is interrupted and the switching regulator 40 stops operating, the internal power supply voltage Vcc will slowly decrease. The power supply standard of the PC card 30 cannot be satisfied.

Therefore, in this embodiment, when the power supply is turned off, the electric charge stored in the constant voltage supply path (particularly, the capacitor Co) is discharged in order to quickly lower the internal power supply voltage Vcc in accordance with the power supply standard of the PC card 30. A discharge circuit including a resistor Ro and a switching element (in this embodiment, an NPN transistor Tr1) is provided. Note that N
The PN transistor Tr1 has a collector connected to a constant voltage supply path via a resistor Ro, and an emitter grounded to a ground line.

Therefore, when a high-level signal (approximately 0.7 V or more) is applied to the base of the NPN transistor Tr1 when the power is off, the NPN transistor Tr1 is turned on, and the charges accumulated in the constant voltage supply path are discharged. It will be discharged. Since the time constant of this discharge is determined by the resistance value of the resistor Ro and the capacitance between the constant voltage supply path and the ground line, if the NPN transistor Tr1 is turned on when the switching regulator 40 stops operating and the power supply is turned off, Internal power supply voltage Vcc decreases at a slope corresponding to this time constant.

Next, the power control unit 50 controls the second battery voltage VBT reference electrode 2 directly supplied from the battery 32.
0, 22a, and 22b receive a reference potential to generate a constant voltage for driving an internal circuit. A constant voltage circuit 5 divides the constant voltage to determine whether to cut off the power supply to the switching regulator 40. Voltage dividing resistors R1 and R2 for generating the reference voltage VSR, and the voltage dividing resistors R1 and R2.
2 and the first battery voltage VAC
C and the first battery voltage VACC becomes equal to the reference voltage VSR.
When the power supply voltage falls below, it is determined that the power supply to the switching regulator 40 has been cut off (that is, the power supply has been turned off).
The comparator 54 outputs a level detection signal S1.
Incidentally, the comparator 54 corresponds to the power cutoff detecting means of the present invention.

The output of the comparator 54 is
6 and 58, each of the timers 56 and 58 measures a certain period of time T1, T2 (T1 <T2) when the high level detection signal S1 is output from the comparator 54, and After the lapse of T1 and T2, the high-level signal S
2 and S3 are output. The output signal S2 from the timer 56 is inverted and input to the AND circuit 60,
The output signal S3 from 8 is input to the AND circuit 60 as it is. As a result, the output signal S from the AND circuit 60
4 indicates that the output signal S2 from the timer 56 is at the low level,
When the output signal S3 from the timer 58 is at the high level, it goes to the high level. The output signal S4 from the AND circuit 60 is input to the base of the NPN transistor Tr1 and the switching regulator 40.
The switching regulator 40 includes an AND circuit 60.
When the output signal S4 is at the high level, the operation is stopped regardless of the voltage level of the first battery voltage VACC.

Here, the timer 56 is for measuring a predetermined time T1 set in advance corresponding to a backup time required for the arithmetic processing unit 20 to back up data. Functions as a timing means. Further, the timer 58 is for securing an off time toff between the time when the PC card 30 is once turned off and the time when the PC card 30 is turned on in accordance with the decrease of the internal power supply voltage Vcc. 30 power supply standards.

In this embodiment, when the output signal S2 from the timer 56 is at a low level and the output signal S3 from the timer 58 is at a high level, the AND circuit 60
A high level signal S4 is output, and the NPN transistor Tr1 is turned on by the signal S4, and the operation of the switching regulator 40 is stopped.

Accordingly, in the power supply section 34 of the present embodiment, as shown in FIG. 3, the first battery voltage VACC is changed to the reference voltage VSR by the turning off of the accessory switch 36 or the instantaneous interruption of the power supply due to the activation of other equipment. And the comparator 5
When power-off is detected at time 4 (time points t1 and t5), when a certain time T1 has elapsed thereafter (time points t2 and t6),
The NPN transistor Tr1 is turned on, and the electric charge accumulated in the constant voltage supply path is discharged.

As a result, according to this embodiment, when the power is turned off, the fall time of the internal power supply voltage Vcc after the power is turned off can be shortened while the data is backed up in the arithmetic processing unit 20. The fall time tpf defined by the PCMCIA standard can be satisfied. That is,
In the conventional power supply device not provided with the power supply control unit 50 and the discharge circuit, the accessory switch 36 is turned off as shown by a dotted line after time t5 in FIG. 3, the first battery voltage VACC decreases, and the switching regulator Even if the operation stops, the internal power supply voltage Vcc decreases slowly due to the capacity of the constant voltage supply path, and the fall time tpf 'cannot satisfy the power supply standard of the PC card 30.
Although the C card 30 cannot be used, according to the present embodiment, the fall time of the internal power supply voltage Vcc when the power is off can be reduced by operating the discharge circuit including the NPN transistor Tr1 and the resistor Ro. Therefore, the time can be adapted to the power supply standard of the PC card 30.

Further, in the power supply section 34 of this embodiment,
As shown in FIG. 3, as described above, the NPN transistor Tr
1 to start discharging the electric charges accumulated in the constant voltage supply path (time points t2 and t6).
As a result, the output signal S4 from the AND circuit 60 becomes High level until it is detected that the elapsed time after the power-off detection has reached the predetermined time T2 (time points t4 and t7), and the switching regulator 40 Operation is stopped.

For this reason, according to the present embodiment, even if the first battery voltage VACC becomes lower than the reference voltage VSR and then recovers in a short time due to an instantaneous interruption of the power supply or the like, after the time t3 in FIG. As shown by the dotted line, switching regulator 40 does not operate and internal power supply voltage Vcc does not immediately rise. That is, according to the present embodiment, the internal power supply voltage Vcc recovers in a short time, for example, when the power supply is momentarily interrupted, even though the fall time tpf of the internal power supply voltage Vcc when the power is off is shortened. PC card 3
An off time toff of 0 can be ensured.

Therefore, according to the present embodiment, in the vehicle-mounted computer 10, the change characteristic of the internal power supply voltage Vcc is
It is possible to conform to the power supply standard of the PC card 30 specified by the MCIA standard, and the PC card 30 mounted on the PC card mounting section 28 can operate normally.

In this embodiment, the power control unit 50 is
By operating using the second battery voltage VBT directly input from the battery 32 instead of the first battery voltage VACC input to the switching regulator 40, the first battery voltage VACC is used as a reference in each of the timers 56 and 58. The time from when the voltage becomes equal to or lower than the voltage VSR (that is, when the power is turned off) is measured. For this reason, it is possible to prevent the time from the return of the first battery voltage VACC until the switching regulator 40 starts operating from becoming unnecessarily long.

That is, when the power supply control unit 50 is operated using the first battery voltage VACC, it is not possible to measure the operation stop time of the switching regulator 40 using the timer 58 when the power supply is turned off. However, in order to secure the operation stop time of the switching regulator 40, it is necessary to measure the time using the timer 58, and for that purpose, it is necessary to start the timer 58 after the first battery voltage VACC recovers. There is. Then, regardless of the actual operation stop time of the switching regulator 40, the switching regulator 40 operates after a certain period of time has elapsed after the return of the first battery voltage VACC. Startup is delayed. On the other hand, according to the present embodiment, the switching regulator 40 is controlled by the timer 58.
Since such an operation stop time can be accurately monitored, such a problem can be prevented.

In this embodiment, the NPN transistor T
Discharge circuit composed of r1 and resistor Ro and timers 56 and 58
AND circuit 6 that operates a discharge circuit in response to a signal from
The operation of “0” realizes the voltage drop characteristic control means, and is determined by a timer 58 that measures the operation stop time of the switching regulator 40 and an operation of an AND circuit that receives a signal from the timer 58 and stops the operation of the switching regulator 40. Voltage supply inhibiting means is realized.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and can take various aspects. For example, in the above embodiment,
The on-vehicle computer used for controlling the car navigation system has been described as an example. However, the power supply device of the present invention is not limited to such an on-vehicle computer for navigation. Applicable to

In the above-described embodiment, the power supply device for supplying power to the PC card 30 conforming to the PCMCIA standard is described in accordance with the power supply standard. Since the off time varies depending on the standard of the personal computer peripheral device provided in the on-vehicle computer, the timers 56 and 58 measure the time T1, T
2 and the like may be set in accordance with the power supply standard of the in-vehicle computer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of a power supply unit built in a vehicle-mounted computer according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of the entire vehicle navigation apparatus according to the embodiment.

FIG. 3 is a time chart illustrating an operation of the power supply unit according to the embodiment.

FIG. 4 is an explanatory diagram illustrating a power supply standard of a PC card conforming to the PCMCIA standard.

[Explanation of symbols]

10: on-board computer 20: arithmetic processing unit 28
... PC card mounting unit 30 ... PC card 32 ... Battery 34 ... Power supply unit 36 ... Accessory switch 40 ... Switching regulator 50 ... Power supply control unit 52 ... Constant voltage circuit 54 ... Comparator 56,58 ... Timer 60 ... And circuit Tr1 ...
NPN transistor Ro, R1, R2 ... resistance

Claims (4)

[Claims] 1. A power supply device, comprising: a constant-voltage power supply circuit that receives a power supply from a vehicle-mounted power supply and generates a DC constant voltage; and supplies the DC constant voltage to a vehicle-mounted computer. Power cutoff detecting means for detecting cutoff of power supply to the circuit; and when the cutoff of power supply is detected by the power cutoff detecting means, the power supply is stored in a constant voltage supply path from the constant voltage power supply to a vehicle-mounted computer. Voltage drop characteristic control means for discharging the charged electric charge to reduce the supply voltage to the on-vehicle computer at a predetermined gradient; and when the power supply cutoff detecting means detects the cutoff of the power supply, The constant voltage supply prohibition for stopping the operation of the constant voltage power supply circuit until the time when the operation of the on-board computer stops due to the decrease in the supply voltage to the computer reaches a predetermined time. Means for changing the supply voltage from the constant voltage power supply circuit to the in-vehicle computer according to a power supply standard of the in-vehicle computer. 2. The voltage drop characteristic control means, when the power supply cutoff is detected by the power supply cutoff detection means,
After that, the in-vehicle computer includes a time-measuring unit that measures a backup time required for backing up data, and when the backup time is measured by the time-measuring unit, the supply voltage to the in-vehicle computer is reduced. The power supply device for a vehicle-mounted computer according to claim 1. 3. The power supply cutoff detecting means detects the cutoff of the power supply when an input voltage from the vehicle-mounted power supply to the constant voltage power supply circuit becomes equal to or lower than a predetermined determination voltage. The power supply device for an in-vehicle computer according to claim 1 or 2. 4. The voltage drop characteristic control means and the constant voltage supply prohibiting means, wherein the voltage drop characteristic of the supply voltage and the operation stop time of the constant voltage supply circuit are respectively PCMCI.
4. The power supply device for a vehicle-mounted computer according to claim 1, wherein the power supply device is configured to conform to a power supply standard of a PC card conforming to the A standard.