JPH0611106B2 - Electronic device switch circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switch circuit of an electronic device for turning on / off a power source of the electronic device.

(Prior Art) As a power switch to turn on / off the power of electronic equipment,
In addition to mechanical snap switches that have been generally used in the past, electronic snap switches have been widely adopted.

FIG. 2 is a connection diagram of a conventional switch circuit of such an electronic device. This circuit is used in the power switch of portable telephones.

In the figure, a switching transistor Tr ₂ is inserted between the power supply 1 and the load 2. A driving element Tr ₁ is provided to turn on / off the switching transistor Tr ₂ . Further, a logic control circuit 3 is provided so as to supply a control current for on / off driving to this drive element.

In this circuit, the transistor Tr ₁ is off state, the base current I _B2 to the transistor Tr ₂ does not flow, the transistor Tr ₂ is turned off.

Here, when the control current I _B1 is supplied from the logic control circuit 3 to the transistor Tr ₁ via the base resistor R1, the transistor Tr ₁ is turned on. by this,
Predetermined base current I _B2 flows through the transistor Tr ₂ via the resistor R2, the transistor Tr ₂ is turned on. Then, the load current I _L is supplied from the power supply 1 to the load ₂ through the transistor Tr ₂ .

At this time, the base current I _B2 of the transistor Tr _2, when the amplification factor of the transistor Tr ₁ and H _FE1 given by the following equation.

The load current _{I L} of I _B2 = H _FE1 × I _BI The transistor Tr _2, when the gain of the Tonranjisuta Tr ₂ and H _FE2 is expressed by the following equation.

I _L = H _FE2 × I _B2 Therefore, in this switch circuit, the transistor Tr
_The power W consumed by the base current I _B2 of 2 passing through the resistor R2 is lost.

(Problems to be Solved by the Invention) In a portable telephone, when the power is turned on, a microprocessor (not shown) performs an operation of reading information required for communication from a read-only memory.
At this time, the portable telephone instantly consumes a large current. However, after that, it operates with a relatively small load current.

In the electronic device having the property that the load current instantaneously increases in this way, the logic control circuit 3 causes the transistor Tr ₁ to pass the maximum load current I _L.
Was designed to supply a sufficiently large control current I _B1 . However, in such a method, even when the consumed current I _L flowing through the load 2 is small, the base current I _B2 of the transistor Tr ₂ flows as in the case of operating at maximum power consumption, so that the power consumption in the switch circuit is large. Becomes
This has been a disadvantageous factor in reducing the power consumption of the entire device.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a switch circuit for an electronic device whose power consumption is reduced.

(Means for Solving Problems) A switch circuit for an electronic device according to the present invention includes a power supply, a load, and
A switching element inserted between the power source and the load, a plurality of driving elements each connected to the switching element to drive the switching element on / off, and an on-state of the plurality of driving elements. A logic control circuit that supplies a control current for off driving, and this logic control circuit selectively controls the drive elements when the power consumption of the load temporarily increases or decreases. A current is supplied to control an on-current flowing through the switching element.

(Operation) The above circuit supplies a large amount of control current to the switching element when the power consumption of the load is temporarily increased, and supplies a small amount of the control current in the normal case. This control is performed by using two or more drive elements and selectively supplying a control current to them. As a result, the control current is increased or decreased substantially in steps, and the power consumption during normal times can be reduced.

(Embodiment) FIG. 1 is a wiring diagram of a switch circuit of an electronic device according to the present invention.

In the figure, a switching element, for example, a switching transistor Tr ₂ is inserted between the current 1 and the load 2. On the other hand, two drive elements, for example, a transistor Tr ₁ and a transistor Tr ₃ are connected in parallel to drive the switching transistor Tr ₂ on / off. These transistors Tr ₁ and T
The collector of r ₃ is connected to the base of the transistor Tr ₂ via the resistor R2. Also, the transistor Tr ₁
The base of is connected to the logic control circuit 3 via a resistor R3. Further, the base of the transistor Tr ₃ is connected to the logic control circuit 3 via the resistor R4.

That is, when comparing the circuit of this embodiment and the conventional example of FIG. 2, the switching Toraji static Tr _2, characterized in that as driven by two drive elements (transistor Tr ₁ and the transistor Tr ₃₎ ing.

Further, the logic control circuit 3 is connected to a detection line 4 that detects an increase / decrease in the load current I _L of the load 2.

The switch circuit having the above configuration operates as follows.

First, when both the transistors Tr ₁ and Tr ₃ are in the off state, the switching transistor Tr ₂ is in the off state, as already described in FIG.

Next, when the power is turned on, the logic control circuit 3 supplies the high-level control currents 5 and 6 to the transistor Tr ₁ and the transistor Tr ₃ . As a result, the transistors Tr ₁ and Tr ₃ are turned on at the same time, and the base current I _B2 flows through the transistor Tr ₂ . here,
If H _FE1 is the amplification factor of the transistor Tr ₁ and H _FE3 is the amplification factor of the transistor Tr ₃ , I _B2 is given by the following equation.

I _B2 = H _FE1 × I _B1 + H _FE3 × I _B3 Therefore, if the amplification factor of the transistor Tr ₂ is H _FE2 , the load current I _L flowing through it can be calculated by the following formula.

I _L = H _FE2 × I _B2 Therefore, the power consumption W consumed by this switch circuit is as follows.

W = ▲ I ² _B2 ▼ × R2 = (H _FE1 × I _B1 × H _FE3 × I _B3 ) ² × R2 Now, the logic control circuit 3 consumes the power I of the load 2.
_L is monitored via the detection line 4. Then, when the consumption current I _L decreases, the control current I _B3 supplied to the transistor Tr ₃ is decreased to a low level. As a result, the current I ′ _B2 at the base of the transistor Tr ₂ is as follows: I ′ _B2 = H _FE1 × I _B1 At the same time, the load current I _L becomes as follows.

I ′ _L = H _FE2 × I ′ _{B2 As} a result of the above, the power consumption W consumed by the resistor R2 is given by the following equation.

W = ▲ I ² _B2 ▼ × R2 = (H _FE1 × I _B1 ) ² × R2 As described above, in the circuit of this embodiment, the logic control circuit 3 includes the two driving transistors Tr ₁ and Tr ₃ . When the load current is increased, both of them are selectively turned on and off, and both are turned on. When the load current is decreased, one driving transistor Tr ₃ is turned off to reduce power consumption. In this way, the on-current of the switching transistor Tr ₂ is controlled.

The present invention is not limited to the above embodiments.

(Effects of the Invention) According to the switch circuit of the present invention described above, power consumption by the switch circuit can be sufficiently reduced except when a large current is temporarily supplied to the load. Therefore, especially when a large amount of power is temporarily supplied from the power supply,
This is effective in reducing power consumption for electronic devices that operate with a small load current.

[Brief description of drawings]

FIG. 1 is a connection diagram of an embodiment of a switch circuit of an electronic device according to the present invention, and FIG. 2 is a connection diagram of a switch circuit of a conventional electronic device. 1 ...... Power, 2 ...... load, 3 ...... logic control circuit, 4 ...... detection _line, Tr 1, Tr ₃ ...... driving element, Tr ₂ ...... switching element.

Claims (1)

[Claims] 1. A power supply, a load, a switching element inserted between the power supply and the load, and a plurality of switching elements each connected to the switching element to drive the switching element on and off. A drive element and a logic control circuit that supplies a control current for ON / OFF drive to each of the plurality of drive elements, and this logic control circuit, when the power consumption of the load temporarily increases or decreases, A switch circuit of an electronic device, wherein a control current is selectively supplied to the plurality of drive elements to control an on-current flowing through the switching element.