JP2005313725A - On-vehicle apparatus and power supply circuit for on-vehicle apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a large capacitance capacitor in a power supply circuit as a measure for power interruption, and to accelerate the rise of the power source supply with respect to the load at the time of application of power in an on-vehicle acoustic device. <P>SOLUTION: The large capacitance capacitor is provided on an output side of a voltage source, and a switch means is provided between the output of the voltage source and a load device. The switch means is controlled so as to be turned on when a predetermined period passes after starting of voltage output from the voltage source, and thereby connection with the load device is done after terminal voltage of the capacitor is sufficiently raised. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

 The present invention relates to a power supply circuit for a vehicle-mounted device.

    An audio signal recording / reproducing apparatus using a compression technique of an audio signal as information has been put into practical use, and a recording medium using a semiconductor memory or a hard disk is available. Furthermore, recently, in-vehicle audio signal recording / reproducing apparatuses using a hard disk as a recording medium have been put into practical use.

An example of an audio signal recording / reproducing apparatus using a hard disk as a recording medium is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-41336.
JP 2002-41336 A

  In-vehicle equipment has a problem with the power supply because it is installed in an automobile. In other words, the power supply in the vehicle is momentarily interrupted by the cranking operation when the engine is started. Here, if the in-vehicle device is, for example, an audio signal recording / playback device using a hard disk, the data on the hard disk may be destroyed if the power is cut off when writing music data to the hard disk. End up. As a result, there arises a problem that audio signal recording is not performed correctly.

  For this reason, in-vehicle audio equipment having a function of writing music data to the hard disk, a large-capacity capacitor is provided in the power supply circuit of the hard disk. A large-capacity capacitor can prevent a voltage drop and prevent destruction of data on the hard disk even when the power supply is cut off.

  On the other hand, in a power supply circuit to which a large-capacity capacitor is connected, the power supply rise time is delayed due to the effect of charging the capacitor. In an in-vehicle acoustic device using a hard disk, calibration processing for setting a write current value at the time of start-up is performed. At this time, if the power supply voltage is not sufficiently stabilized at the specified voltage, a calibration value is set erroneously, and a malfunction that prevents subsequent writing operations from being performed normally occurs. As an example, a hard disk requires a power supply rise time within 5 to 100 ms, but a power supply rise time is about 2 seconds in a circuit connected to a large capacity capacitor. Therefore, when a large-capacity capacitor is provided for instantaneous power interruption, it is necessary to take measures for calibration processing of the hard disk.

  Accordingly, an object of the present invention is to keep the power supply rise time within a specified time required by a load side device (for example, a hard disk) while performing backup at the time of power supply interruption with a large capacity capacitor.

  In the present invention, switch means is provided between the capacitor that receives the output of the voltage source and the load. The switch means connects the load and the voltage source with a delay of a predetermined time from the timing at which the output voltage is supplied from the voltage source. Therefore, after the capacitor is completely charged and the voltage at the capacitor end is sufficiently stabilized, the connection with the load is performed. That is, as viewed from the load, the power supply voltage rises in a sufficiently short time.

  With the above configuration, the rise time of the power supply voltage directly supplied to the load side device can be shortened. Therefore, when the load side device is a hard disk, there is no possibility of erroneous calibration processing. In the event of a momentary power interruption, the influence can be reduced by the large-capacity capacitor.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of an in-vehicle acoustic apparatus having a power supply circuit of the present invention. + B is an output of a generator mounted on the automobile, and is a power output of about + 12V to + 16V connected to an in-vehicle battery. The + B power is supplied to the operation unit and the control unit of the in-vehicle audio apparatus and is also supplied to the DC-DC converter 10 that generates + 5V power such as a hard disk (HDD) or a compact disk (CD) drive.

  The DC-DC converter 10 is a circuit that converts a voltage of + 12V to + 16V into a stable + 5V. A large-capacity capacitor 11 called an electric double layer capacitor of about 1.5 F is connected to the + 5V output of the DC-DC converter 10, and the HDD 13, CD drive 14, memory 15, and HDD / CD control unit 16 are connected via the MOS-FET 12. To be supplied.

  This in-vehicle acoustic device is equipped with an HDD 13 and a CD drive 14, and can record audio CD music on the HDD 13. The flow of processing during recording will be described below. First, a user such as a driver inserts an audio CD into the CD drive 14. When the HDD / CD control unit 16 detects that a CD has been inserted, the HDD / CD control unit 16 notifies the control unit 17 that the CD has been inserted, reproduces the music on the CD, and outputs audio from the speaker 18 via the control unit 17. The control unit 17 displays the CD playback state on the display 20 via the operation unit 19. The user gives a recording instruction with the operation key 21 during CD playback display. When receiving the recording instruction, the operation unit 19 instructs the HDD / CD control unit 16 to record via the control unit 17. The HDD / CD control unit 16 compresses the music data and writes it to the HDD 13 while reproducing the music data read from the CD drive 14. Recording is ended by recording all music data in the CD or by pressing a cancel operation key by the user.

  Reproduction of music recorded on the HDD 13 is instructed to the HDD / CD control unit 16 via the operation unit 19 and the control unit 17 when the user presses the HDD reproduction operation key. The HDD / CD control unit 16 reads music data from the HDD 13, decompresses the compressed music data, converts it into sound, and outputs it from the speaker 18 via the control unit 17.

  If the power is cut off during the data writing of the HDD 13, the data written to the HDD 13 becomes halfway, and the HDD 13 cannot be read correctly thereafter. For this reason, the writing operation to the HDD 13 is performed by dividing into fine units to reduce the possibility of power interruption during writing. However, one write operation may take about 20 ms, and if the power is shut off during this time, the data in the HDD 13 is destroyed. As a countermeasure, a large-capacity capacitor is provided at the output of the DC-DC converter 10. Even when the + B power supply is cut off and the + 5V output of the DC-DC converter 10 is cut off, current can be supplied from the capacitor 11 to the HDD via the MOS-FET 12 to the HDD 13 for about 50 ms. It can be avoided that the power supply to the HDD 13 is cut off.

  FIG. 2 shows a power supply circuit according to an embodiment of the present invention. FIG. 3 is a waveform diagram showing the operation of the embodiment of the present invention. The power-on operation in this embodiment will be described with reference to FIGS.

  C1, C2, and C3 in FIG. 2 are electric double layer capacitors having a capacitance of 4.7 F / withstand voltage of 2.3 V, and correspond to the capacitor 11 in FIG. Since one capacitor cannot satisfy the withstand voltage of +5 V, three capacitors are connected in series. C1, C2, and C3 constitute a 1.6 F capacitor corresponding to one third of the capacity. R1, R2, and R3 are 3.3 kΩ resistors, which are voltage guarantee resistors that apply the same voltage to each electric double layer capacitor, and prevent each electric double layer capacitor from being applied with a voltage higher than the withstand voltage. . R4 is 22 kΩ, C4 is 47 μF, and R5 is about 1 kΩ. These function to adjust the switch time of the MOS-FET 12 (Q1). Q2 is a transistor with a built-in resistor, and when the ON2 signal becomes high level, the gate (G) of Q1 is set to the GND level, and the source (S) -drain (D) of Q1 is made conductive.

  When the HDD / CD unit 30 is turned on, the activation is instructed by setting the activation signal ON1 from the control unit to the DC-DC converter 10 to a high level. Since the output of the DC-DC converter 10 is charged in the capacitors C1, C2, and C3, + 5V takes about 2 seconds to reach the 5V level as shown in the time chart of FIG. The control unit 17 sets the ON2 signal to high level 3 seconds after setting the ON1 signal to high level. When the ON2 signal becomes high level, the transistor Q2 is turned on, and G of the MOS-FET (Q1) gradually becomes GND level by the action of R4, C4 and R5. The gate (G) of Q1 is charged with C4 and is connected to GND via R5 and Q2, and the decrease in the gate (G) voltage is determined by the values of R5 and C4. When C4 = 47 μF and R5 = 1 kΩ, the rise of HDD + 5V is about 10 ms. If the value of R5 or C4 is doubled, the rise time is almost doubled to 20 ms. With these operations, the power supply rise time 5 to 100 ms required by the HDD 13 can be satisfied.

  Note that the time during which Q1 is turned off after Q2 is turned off varies depending on the value of R4. Since the charge of C4 is discharged through R4, the time for the G voltage of Q1 to change from the GND level to + 5V can be delayed. When R4 = 22 kΩ and C4 = 47 μF, the time is about 1.1 s, and when R4 = 10 kΩ, the time is about 0.45 s. Thereby, even if the ON2 signal is turned off, Q1 is turned on for a while, so that the capacitor charge can be supplied to the load such as the HDD 13 or the like.

  FIG. 4 shows a waveform diagram at the time of a power interruption that occurs due to cranking or the like when the engine of the automobile is started. When the + B power supply is momentarily interrupted, + 5V generated by the DC-DC converter 10 from the + B power supply is also in an instantaneous interruption state. At this time, the electric charge stored in the capacitors C1, C2, C3 is supplied to the HDD 13 side via the MOS-FET (Q1). If there is an instantaneous interruption of about 20 ms, the power supply voltage HDD + 5V to the HDD 13 does not fall below the HDD operation lower limit voltage 4.5V, and the write operation of the HDD 13 can be continued.

As described above, according to the present invention, the power backup capacitor can be connected to a circuit that malfunctions when the power supply rise time is slow, such as an HDD, and it is possible to cope with an instantaneous power supply interruption.

1 is a block diagram of an in-vehicle audio device according to an embodiment of the present invention. It is a circuit diagram which shows the power supply circuit concerning the Example of this invention. It is a wave form diagram for demonstrating operation | movement of the Example of this invention. It is a wave form diagram at the time of power supply interruption.

Explanation of symbols

10 DC-DC converter 11 Capacitor 12 MOS-FET
17 Control unit

Claims (5)

A voltage source, a capacitor provided at an output end of the voltage source, a load device, a switch means provided between the load device and the output end, and the switch means at the time of voltage output from the voltage source. And a control circuit for turning on after a predetermined time. The power circuit for an in-vehicle device according to claim 1, wherein the predetermined time is longer than a time required for the voltage at the output terminal of the voltage source based on the capacitor to rise to a predetermined voltage. The load device is a power circuit of the in-vehicle device, which is a hard disk. In-vehicle equipment equipped with at least a load device and a power supply circuit,
The power supply circuit includes a voltage source, a capacitor provided at an output end of the voltage source, and switch means provided between the load device and the output end,
Vehicle-mounted equipment comprising control means for turning on the switch means after a predetermined time from the time of voltage output from the voltage source. The in-vehicle device according to claim 4, wherein the in-vehicle device is an acoustic device including a hard disk as a load device.

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