JP2008092648A - Power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the service life of a battery to be used for a power supply circuit by suppressing unnecessary consumption thereof. <P>SOLUTION: In the power supply circuit 1 in which connectors 18 for the battery and an auxiliary battery are connected in parallel via a diode 16 for blocking a current from one side to the other side of each connector, an FET is connected in parallel with the diode 16 connected to the connector 18 of the battery 10 as standard equipment. If the auxiliary battery 12 is not connected, the FET is conducted so that the current from the standard equipment battery 10 is applied to a circuit 14 to be driven while making a detour of the diode 16 having a large internal resistance. Thus, voltage drop due to the diode 16 can be prevented, and consumption of the standard equipment battery 10 is suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power supply circuit of a terminal device such as a communication terminal device that uses a battery as a power source.

  For example, a battery is used in a communication terminal device used in a remote control system or the like. In such a power supply circuit, normally, only a battery provided as a standard is used, but when the battery is consumed and the voltage drops, the battery is charged or the battery is replaced. However, taking the remote control system as an example, the communication terminal device is often not installed in a place where charging is actually possible or inconvenient for charging, and charging is impossible. Therefore, lithium batteries having a long battery life are often used for remote control systems.

Furthermore, since it is not easy to replace the battery depending on the use conditions and use environment of a device such as a communication terminal device, the power supply circuit of these devices is equipped with a plurality of connection connectors so that a spare battery can be connected.
However, when there is a difference between old and new lithium batteries connected to multiple connectors, a potential difference occurs between the batteries, and current flows from the higher voltage to the lower voltage to charge the lower battery. End up. Therefore, a backflow prevention diode is connected to each of the plurality of connection connectors so that such a charging current does not flow.

The power supply circuit shown in FIG. 4 is not described in the patent literature, but is an example of the conventional power supply circuit described above.
As shown in the figure, the conventional power supply circuit 1 is connected in parallel to an operation circuit (referred to as a driven circuit) 14 that uses a standard-equipped standard battery 10 and a spare battery 12 as power sources via connectors 18 respectively. A diode 16 is connected to each power supply circuit to the driven circuit 14 to prevent backflow.
With this configuration, when both the standard battery 10 and the standard battery 10 are connected to the connector 18, even if there is a potential difference between the two batteries, the current flows from the spare battery 12 to the standard battery 10 or vice versa. Can be fed from both batteries 10 and 12 to the driven circuit 14 without backflow.

However, in the conventional power supply circuit 1, both the standard-equipped battery 10 and the spare battery 12 are not necessarily connected to the connector 18, and only one of them may be connected and used. In such a case, the height of the internal resistance of the diode 16 becomes a problem.
In other words, if only one of the batteries 10 and 12 as the power source is connected to the connector 18 of the power circuit, the battery life is not only exhausted early due to the power consumption of the diode 16 which is originally unnecessary, When a DD converter (DC-DC converter) is used in the driven circuit 14 to be fed, for example, as used in a main unit or a sub unit of a remote control system, a voltage drop due to the diode 16 is caused. As a result, the conversion efficiency decreases, and as a result, the current consumption increases. In such a case, there is a problem that the battery life is further exhausted.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a power supply circuit in which a battery and a spare battery are connected in parallel using a backflow prevention diode, and a diode at the time of power feeding. Is to prevent the battery from being depleted and to extend the life of the battery.

The invention according to claim 1 is a power supply circuit, wherein the battery connector and the auxiliary battery connector are each connected in parallel via a diode for blocking current from one side to the other side, and the connector A bypass circuit means connected in parallel to a diode connected to at least one of the two and capable of conducting only in the same direction as the diode; and conduction or non-conduction of the bypass circuit means depending on whether or not a battery is connected in the other connection circuit The continuity control means controls continuity of the bypass circuit when a battery is connected to the other connection circuit.
The invention according to claim 2 is the power supply circuit according to claim 1, wherein the bypass circuit means of the diode is a semiconductor, and the conduction control means detects the voltage of the battery connected to the other connector, Conductivity control is performed on the semiconductor.
According to a third aspect of the present invention, in the power supply circuit according to the second aspect, the semiconductor is an FET, and the conduction control means controls a gate voltage of the semiconductor.

  According to the present invention, it is possible to eliminate the influence of a voltage drop caused by a backflow prevention diode in a power supply circuit in which a battery serving as a power supply and a spare battery can be connected in parallel. In addition, the battery can be prevented from being wasted.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a power supply circuit 1 according to an embodiment of the present invention.
The power supply circuit 1 is basically based on the conventional power supply circuit 1 shown in FIG. 4. However, for example, when the spare battery 12 is not connected, a bypass circuit that bypasses the diode 16 is used. In addition, voltage drop and power consumption due to the diode 16 is avoided.
As shown in the figure, when a FET (electrolytic effect transistor) having a small resistance when conducting is connected in parallel to the diode 16 on the standard equipment battery 10 side and only the standard equipment battery 10 is connected to the connector 18, this FET is turned on. To the state. That is, the power supply circuit 1 is provided with an FET ON / OFF control circuit so that the FET is turned OFF when the spare battery 12 is connected to the connector 18.

  Here, the FET serving as the bypass circuit and its ON / OFF control circuit include a transistor (NPN transistor) T2 for controlling conduction of the gate circuit of the FET and a transistor T3 for controlling conduction of the transistor T2. (NPN transistor) The base of T3 is connected to the connector 18 side of the spare battery 12 via a resistor R3.

That is, in FIG. 1, in the state where the spare battery 12 is not connected to the connector 18 on the spare battery 12 side, the transistor T3 is OFF, so that the current from the standard equipment battery 10 side is the resistor R1, the base and collector of the transistor T2. The transistor T2 is turned on and the transistor T2 is turned on, so that the emitter current flows through the resistor R2, generating a potential there, and turning on the FET.
When the FET is turned on, the current from the standard battery 10 to the driven circuit 14 flows through the FET which is the bypass circuit means, and therefore the voltage drop due to the diode 16 hardly occurs.

In this way, the power supply circuit 1 can supply current to the driven circuit 14 without passing through the diode 16 unless the spare battery 12 is connected to the connector 18. This is convenient when the spare battery 12 is not connected to the terminal 18 and is used only when necessary.
In the power supply circuit 1, when the spare battery 12 is connected to the connector 18, the transistor T3 is turned on. As a result, the transistor T2 is turned off and the FET is also turned off.
Therefore, in this state, the current from the standard battery 10 flows through the diode 16. In this case, the current from the spare battery 12 is also supplied to the driven circuit 14 through the diode 16. The influence of the voltage drop due to the diode 16 is negligible.

In this power supply circuit 1, if a parasitic diode opposite to the diode 16 exists in the FET, if a spare battery 12 is connected later, a charging current may flow from the spare battery 12 to the standard battery 10 through the parasitic diode. There is.
Therefore, it is necessary to remove the influence of this parasitic diode.
FIG. 2 exemplifies the power supply circuit 1 according to the second embodiment in which the countermeasure is taken. Since the basic configuration is the same as that of FIG. 1, the same parts are denoted by the same reference numerals and the description thereof is omitted. To do.
Here, this problem is solved by connecting two FETs in series. In other words, two FETs are connected in series in the opposite direction, and even if a parasitic diode exists, this configuration can cancel the influence of each other, and the charging current flows from the spare battery 12 to the standard battery 10. Can be completely shut off.

In each of the power supply circuits 1 described above, a bypass circuit composed of an FET or the like is inserted in parallel with the diode 16 in the power supply circuit from the standard battery 10 to the driven circuit 14 to reduce the potential drop of the diode 16 in the power supply circuit. The effect is to be eliminated, and the potential drop due to the diode 16 is not taken into consideration for the power supply circuit on the spare battery side.
Therefore, the power supply circuit 1 is premised on that when a battery is connected to the connector 18, it is always connected to a standard battery-side connector.

However, when the battery is actually connected to the connector 18, there is a problem that it is bothersome and error-prone to always select and connect the connector on the standard battery side.
Therefore, even if the battery is connected to either the standard battery side connector or the spare battery side connector, the standby battery 12 side power supply circuit is also composed of an FET or the like in parallel with the diode 16 so that the effect of the present invention can be obtained equally. It is preferable to connect a bypass circuit.

FIG. 3 shows a power supply circuit in which an FET is connected in parallel with the diode 16 in the power supply circuit on the spare battery 12 side in the power supply circuit of FIG.
Since the other configuration of the power supply circuit 1 is the same as that of FIG. 2, the same portions are denoted by the same reference numerals and description thereof is omitted.
By configuring the power supply circuit 1 in this way, regardless of whether the connector 18 is the standard battery 10 or the spare battery 12 side, a battery is connected to any one of the connectors 18 so that the current from the battery is The diode 16 can always be bypassed and supplied to the driven circuit 14.

When batteries are connected to both the standard equipment battery 10 side and the spare battery 12 side, both the FETs are turned off, and all the currents from the batteries 10 and 12 are routed through the diode 16. Is supplied from both the standard equipment battery 10 and the reserve battery 12, the influence of the potential drop due to the diode 16 can be ignored. Therefore, even if a DD converter is connected to the driven circuit 14, there is no influence of the potential drop.
Even in this state, for example, when the voltage of one battery falls below a predetermined level, the bypass circuit operates, and the current from the other battery bypasses the diode 16 and flows to the driven circuit 14. It can contribute to the life extension of the battery.

1 is a power supply circuit according to a first embodiment of the present invention. It is a power supply circuit which concerns on the 2nd Embodiment of this invention. It is a power supply circuit which concerns on the 3rd Embodiment of this invention. It is an example of the conventional power supply circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power supply circuit, 10 ... Standard equipment battery, 12 ... Reserve battery, 14 ... Driven circuit, 16 ... Diode, 18 ... Connector, T2, T3 ... Transistor.

Claims (3)

A power supply circuit in which a battery connector and an auxiliary battery connector are connected in parallel via diodes that block current from one side to the other side,
Detour circuit means connected in parallel to a diode connected to at least one of the connectors and capable of conducting only in the same direction as the diode;
Comprising conduction control means for controlling conduction or non-conduction of the bypass circuit means according to the presence or absence of battery connection in the other connection circuit;
The power supply circuit characterized in that the conduction control means controls conduction of the bypass circuit when a battery is connected to the other connection circuit. The power supply circuit according to claim 1,
The power supply circuit according to claim 1, wherein the bypass circuit means of the diode is a semiconductor, and the conduction control means controls conduction of the semiconductor when detecting a voltage of a battery connected to the other connector.   3. The power supply circuit according to claim 2, wherein the semiconductor is an FET, and the conduction control means controls a gate voltage of the semiconductor.

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