Electric power supply unit and electric power supply controlling method

1. Field of the Invention

The present invention belongs to the technical field of electric power supply units and electric power supply controlling methods utilizing a plurality of electric power supply lines.

2. Related Background Art

In an audio amplifier for automobile use, it is known that a voltage of an in-vehicle battery is boosted with a DC-DC converter to increase an audio output as described in Japanese Patent Application Laid-open No. Hei-9-291843.

However, there is a case where a current-carrying capacity of a standard electrical wiring in a vehicle, which is 10 amperes for example, is not enough for an audio amplifier utilizing a DC-DC converter. In this case, it is necessary to use a dedicated wiring 120 having a large current-carrying capacity, such as 20 amperes, as described in FIG. 1 . The audio amplifier described in FIG. 1 has a power amplifier unit 110 connected to an in-vehicle battery 1 through a connector 102 . The power amplifier unit 110 is provided with: a pair of power amplifiers 111 A and 11 B; a DC-DC converter circuit 112 supplying a power supply voltage to the power amplifiers 111 A and 111 B; and an on-off detecting circuit 116 for controlling operations of the power amplifiers 111 A and 111 B by detecting on-off status of an accessory switch 6 . Therefore, it is necessary to install the dedicated wiring 120 for passing a current from the battery 1 , in a vehicle, and to use a fuse and a connector capable of being used for a current having a large capacity. Thus, complicated work and special components are needed.

An object of the present invention is to provide an electric power supply unit and electric power supply controlling method capable of easily increasing a capacity of a working current.

The above object of the present invention can be achieved by an electric power supply unit of the present invention. The electric power supply unit is provided with: a first electric power supply circuit in which an electric current is supplied from a first power supply line; a second electric power supply circuit in which an electric current is supplied from a second power supply line; and a controlling device which controls operations of both the first electric power supply circuit and the second electric power supply circuit so as to correlate to each other.

The above object of the present invention can be achieved by an electric power supply controlling method of the present invention. The method is provided with the processes of: controlling an operation of a first electric power supply circuit in which an electric current is supplied from a first power supply line so as to keep its voltage at a predetermined value; controlling an operation of a second electric power supply circuit in which an electric current is supplied from a second power supply line so as to keep its voltage at approximately same value as that of the first electric power supply circuit; detecting an on-off states of the second power supply line; controlling the operations of the first electric power supply circuit and the second electric power supply circuit so as to turn the circuits on when an on-status of the second power supply line is detected; and controlling the operations of the circuits so as to turn the circuits off when an off-status of the second power supply line is detected.

The above object of the present invention can be achieved by an electric power supply controlling method of the present invention. The method is provided with: a first controlling process of controlling an operation of a first electric power supply circuit in which an electric current is supplied from a first power supply line so as to keep its voltage at a predetermined value; a second controlling process of controlling an operation of a second electric power supply circuit in which an electric current is supplied from a second power supply line so as to keep its voltage at approximately same value as that of the first electric power supply circuit; a detecting process of detecting an on-off states of the second power supply line; a third controlling process of controlling the operations of the first electric power supply circuit and the second electric power supply circuit so as to turn the circuits on when an on-status of the second power supply line is detected; a fourth controlling process of controlling the operations of the circuits so as to turn the circuits off when an off-status of the second power supply line is detected; a determining process of determining whether or not the first and second controlling processes are necessary; and a switching process of switching between the implementation and the termination of the first and second controlling processes in response to a determination result in the determining process.

FIG. 1 is a block diagram showing the structure of a conventional electric power supply unit;

FIG. 2 is a block diagram showing the structure of an audio amplifier to which an electric power supply unit of a preferred embodiment of the present invention is applied;

FIG. 3 is a circuit diagram of the audio amplifier; and

FIG. 4 is a flow chart indicating an operation in the audio amplifier.

Referring to FIGS. 2 to 4 , a preferred embodiment of the present invention will be described. In the preferred embodiment, an electric power supply unit of the present invention is applied to an audio amplifier for automobile use.

FIG. 2 is a block diagram showing the structure of the audio amplifier to which the electric power supply unit of the preferred embodiment is applied. FIG. 3 is a circuit diagram indicating of a specific structure of the audio amplifier.

As shown in FIG. 2 , the audio amplifier has a power amplifier unit 10 connected to a in-vehicle battery 1 through a connector 2 . The power amplifier unit 10 is connected to the battery 1 through both of a backup line 4 and an accessory line 5 . A fuse whose rated capacity is 10 amperes is connected to each line. An accessory switch 6 , which is operated through an ignition key cylinder mounted in a vehicle, is inserted in the accessory line 5 .

As shown in FIG. 2 , the power amplifier 10 is provided with: a pair of power amplifiers 11 A, 11 B; DC-DC converter circuits 12 A, 12 B which supplies a power supply voltage to the power amplifiers 11 A, 11 B; a voltage control circuit 14 controlling an output voltage of the DC-DC converter circuits 12 A, 12 B; a delay-inhibiting circuit 15 for inhibiting a delay of an operation when turning off the accessory switch 6 ; and an on-off detecting circuit 16 for detecting on-off status of the accessory switch 6 . The DC-DC converter circuit 12 A is connected to the backup line 4 , and the DC-DC converter circuit 12 B is connected to the accessory line 5 , through a connector 2 respectively.

As shown in FIG. 3 , the DC-DC converters 12 A and 12 B comprises the same circuit as a general DC-DC converter, and have switching elements 12 a and 12 b respectively.

As shown in FIG. 3 , voltage control circuit 14 is provided with: a pulse control circuit 14 a which applies a control pulse to the switching element 12 a of the DC-DC converter 12 A; a pulse control circuit 14 b which applies a control pulse to the switching element 12 b of the DC-DC converter 12 B; a voltage comparator circuit 14 c ; and a voltage comparator circuit 14 d . Diodes D 2 and D 3 are connected in parallel in the direction opposite to each other between output lines of the DC-DC converter circuits 12 A and 12 B.

As shown in FIG. 3 , the delay-inhibiting circuit 15 has a backflow-inhibiting diode D 1 for inhibiting backflow of current when the accessory switch 6 is turned off. The on-off detecting circuit 16 has: resistors R 1 and R 2 which divide voltage of the accessory line 5 ; and a transistor Q 1 which is turned off or turned on in response to divided voltage.

An operation of the audio amplifier of the preferred embodiment will be described hereinafter.

In the audio amplifier of the preferred embodiment, by operating the DC-DC converter circuits 12 A and 12 B, the voltages supplied through the backup line 4 and the accessory line 5 are increased to a preset voltage which is preset higher than the voltage of the battery 1 , and then the preset voltage is applied to the power amplifiers 11 A and 11 B. It is possible to operate the audio amplifier without operating the DC-DC converter circuits 12 A and 12 B. In this case, the voltage of the battery 1 is applied to the power amplifiers 11 A and 11 B. Thus, it is possible to switch the operational status of the DC-DC converter circuits 12 A and 12 B between on and off. When operating the DC-DC converter circuits 12 A and 12 B, by increasing power supply voltage, it is possible to obtain larger audio output than that in the case of turning off the DC-DC converter circuits 12 A and 12 B.

The voltage control circuit 14 controls the DC-DC converter circuits 12 A and 12 B so as to suppress a voltage difference between output voltages of the DC-DC converter circuits 12 A and 12 B.

As shown in FIG. 3 , the voltage comparator circuit 14 c detects variations in an output voltage of the DC-DC converter circuit 12 A with respect to a regulated voltage which is regulated with a Zener diode 14 e . Then, the voltage comparator circuit 14 c provides comparison results to the pulse control circuit 14 a . The pulse control circuit 14 a controls the DC-DC converter circuit 12 A so as to keep its output voltage constant by outputting pulses to the switching element 12 a in response to the comparison results.

The voltage comparator circuit 14 d compares the output voltage of the DC-DC converter circuit 12 A with that of the DC-DC converter circuit 12 B. Then, the voltage comparator circuit 14 d provides comparison results to the pulse control circuit 14 b . The pulse control circuit 14 b controls the DC-DC converter circuit 12 B so as to keep its output voltage identical to that of the DC-DC converter circuit 12 A by outputting pulses to the switching elements 12 b in response to the comparison results.

By the above-explained operations, when operating the DC-DC converter circuits 12 A and 12 B, the voltage control circuit 14 controls the DC-DC converter circuits 12 A and 12 B so as to keep the output voltage of the DC-DC converter circuit 12 A and 12 B at an identical value which is set in advance. Therefore, it is possible to operate two power amplifiers under the same conditions all the time.

The diodes D 2 and D 3 in the voltage control circuit 14 have the function of keeping the voltage of output lines of the DC-DC converter circuit 12 A and 12 B at an approximately constant value when the DC-DC converter circuits 12 A and 12 B are not operated. When the DC-DC converter circuits 12 A and 12 B are not operated, the voltage of the battery is directly applied to the power amplifiers 11 A and 11 B in substance.

The delay inhibiting circuit 15 inhibits electrical charge, which is charged in a capacitor C 1 of the DC-DC converter 12 B, from flowing into the accessory line 5 when the accessory switch 6 is off. Further, it is possible to establish a ground for the accessory line 5 certainly by use of the resistors R 1 and R 2 . Therefore, it is possible to detect rapidly that the accessory switch 6 becomes off in the on-off detecting circuit 16 which is described later.

The on-off detecting circuit 16 detects an on-off status of the accessory switch 6 . When the accessory switch 6 becomes on, the transistor Q 1 turns on and outputs an L signal as a detecting signal. When the accessory switch 6 becomes off, the transistor Q 1 turns off and outputs an H signal as a detecting signal. As shown in FIG. 2 , the detecting signal is supplied to the power amplifiers 11 A, 11 B and the voltage control circuit 14 , so that it is possible to switch the operational statuses of the power amplifiers 11 A, 11 B and the voltage control circuit 14 in response to the on-off status of the accessory switch 6 .

FIG. 4 is a flowchart diagram indicating a flow of operation of the audio amplifier. When the present invention has a configuration shown in FIGS. 2 and 3 , substantially same operation as the processing shown in FIG. 4 is executed. However, the processing shown in FIG. 4 can be executed by use of a computer.

FIG. 4 indicates the operation in the case of switching the accessory switch 6 in the order of: off, on, and off. When the accessory switch 6 is switched from off to on, the on-off detecting circuit 16 detects that the accessory switch 6 becomes on (step S 1 ). At this time, DC-DC converters 12 A and 12 B are not operated. When the power amplifiers 11 A and 11 B receive a detecting signal from the on-off detecting circuit 16 , the power amplifiers 11 A and 11 B are operated (step S 2 ). Then, it is determined whether or not the audio output is larger than a constant value (step S 3 ). This determination can be done based on whether or not the level of input signal to the power amplifiers 11 A and 11 B is greater than a constant value.

In step S 3 , when it is determined that the audio output is not greater than the constant value, the DC-DC converters 12 A and 12 B becomes inoperative (step S 4 ). Further, the voltage control circuit 14 becomes inoperative (step S 5 ), and the processing goes to step S 8 . On the other hand, in step S 3 , when it is determined that the audio output is greater than the constant value, the DC-DC converters 12 A and 12 B becomes operative (step S 6 ). Then, the voltage control circuit 14 becomes operative (step S 7 ), and the processing goes to step S 8 .

In step S 8 , when the on-off detecting circuit 16 detects that the accessory switch 6 becomes off, the audio amplifier turns off (step S 9 ). Then, the operation indicated in FIG. 4 is terminated. In step S 8 , when the on-off detecting circuit 16 detects that the accessory switch 6 becomes on, the processing returns to step S 3 .

Thus, the DC-DC converter circuits 12 A, 12 B and the voltage control circuit 14 are continuously controlled so as to be switched from on to off, or from off to on in response to the magnitude of the audio output until the accessory switch 6 is off.

As explained above, according to the electric power supply unit of the preferred embodiment, since currents are supplied from the backup line and accessory line previously provided in a vehicle, the current capacity can be increased without having dedicated lines. Therefore, it is unnecessary to do work operations for having dedicated lines. In addition, it is unnecessary to use special components. Accordingly, it is possible to increase the audio output very easily.

Since the electric power supply unit comprises: the DC-DC converter circuit 12 A in which a current is supplied from the backup line 4 ; the DC-DC converter circuit 12 B in which a current is supplied from the accessory line 5 ; and the voltage control circuit 14 which control the operations of the DC-DC converter circuit 12 A and the DC-DC converter circuit 12 B, it is possible to control the voltage of the two DC-DC converter circuits appropriately.

In the embodiment, the electric power supply unit works as a part of the audio amplifier for automobile use. An electric power supply unit of the present invention is not limited to an equipment for automobile use or an audio equipment. Further, in the embodiment, the backup line and the accessory line as two power line systems are connected to one battery. However, a battery connected to each electric line can be provided separately. In addition, an electric power source for supplying electric power to a plurality of power supply line systems is not limited to a battery. For example, a commercial power source can be used.

The entire disclosure of Japanese Patent Application No. 2002-321977 filed on Nov. 6, 2002 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.