JPS63316504A - Constant current circuit device - Google Patents

Abstract

PURPOSE:To decrease a power consumption quantity, to suppress a temperature rise in the circuit and to improve the reliability of an action by decreasing the value of a power source voltage supplied to a current adjusting circuit lower than the value of the power source voltage supplied to a constant current circuit. CONSTITUTION:A current adjusting circuit 3, when a second current IC2, namely, an output current is changed, generates a third current IC3 to cancel the changing part. Based on the third current, a first current IC1 of a constant current circuit 2 is adjusted and an output current IC2 is unified. At such a time, at a current adjusting circuit 3, a current IC4 flows from a low order power source line L2 to the constant current circuit 2 side and a power consumption equivalent to a voltage VCC2 and a current lC4 occurs. Thus, by decreasing the power source voltage supplied to the current adjusting circuit 3, the power consumption quantity is decreased, the temperature rise in the circuit is suppressed and the reliability of the action is improved.

Description

[Detailed Description of the Invention] [Summary] A constant current circuit device, particularly a constant current circuit device integrated within a semiconductor chip,
Regarding a device that obtains a constant output current according to an input current determined by a predetermined reference voltage and resistance, it is possible to reduce power consumption, improve reliability as a device, and reduce circuit scale. A first power supply line with a predetermined voltage, a second power supply line with a predetermined voltage lower than the predetermined voltage, and a voltage/current conversion circuit that converts a predetermined reference voltage into a predetermined current using a resistor.
a constant current circuit that receives voltage supply from the first power supply line and generates a first current corresponding to the magnitude of the predetermined current and a second current corresponding to the magnitude of the first current; ,
The voltage is supplied from the second power supply line, and the second
a current adjustment circuit that generates a third current in a direction that cancels out the change when the current changes and has a magnitude corresponding to the change, and adjusts the first current with the third current; , and is configured to control and output the second current to a constant value based on the first current adjustment by the third current based on the voltage supply from the second power supply line.

[Industrial application field]

The present invention relates to a constant current circuit device, and more particularly to a device integrated in a semiconductor chip and configured to obtain a constant output current in response to an input current determined by a predetermined reference voltage and resistance. The device according to the present invention can be used, for example, as a source of a write current flowing to a head in a magnetic disk device.

[Conventional technology]

FIG. 3 shows in block form the configuration of a constant current circuit device as an example of a conventional type.

In the figure, 31 is a voltage/current conversion circuit, which converts a predetermined current i based on a predetermined reference voltage VRo and a resistor RO.
32 is a constant current circuit, which receives voltage (VCC) from the power line L and outputs a current corresponding to the magnitude of a predetermined current IO. , has a function of outputting an output current I2 to a terminal OUT (in the illustrated example, in the opposite direction) in accordance with the magnitude of the current 11. 33 is a current adjustment circuit, which is at least NPN
The transistor Tr has a collector connected to the above-mentioned power supply line L, and a base and emitter connected to the input/output terminal of the constant current circuit 32.

This current adjustment circuit 33 controls the output current I of the constant current circuit 32.
2 changes, for example, when the output current I2 changes based on a change in the parameter hFE of a transistor (not shown) in the constant current circuit due to temperature, etc., in a direction that cancels out the change and the change. It has a function of generating an adjustment current I3 having a magnitude corresponding to the current, and adjusting the above-mentioned current 11 with this adjustment current. For example, when the current I2 increases slightly, the adjustment current I3 by the current adjustment circuit 33 reduces the current 1 to cancel out the variation. Therefore, the current I.

As the output current I2 decreases, the output current I2 also decreases.
The increases mentioned above are offset. In other words, the current adjustment circuit 3
3 is a circuit that contributes to keeping the output current (2) constant.

[Problem that the invention seeks to solve]

According to the configuration of the conventional device described above, the current adjustment circuit 33
While the transistor Tr is performing its original adjustment function, a current I4 flows from the power supply line L to the constant current circuit 32 through the collector and emitter of the transistor Tr. That is, as this current I4 flows, power corresponding to (voltage VCC x current 14) is consumed in the current adjustment circuit 33, and heat corresponding to the amount of power consumption is generated. This is the amount of power consumption, or heat, that would not have occurred if there was no current adjustment circuit, and is the amount of power consumption, or heat, that would have been generated by providing it to realize the constant current function.

As is known, integrated circuits (ICs) are sensitive to heat, and the increase in temperature within the circuit due to this heat can impair operational reliability, and furthermore, it requires a large space for heat dissipation. Since this is necessary, there is a problem that the circuit scale becomes relatively large.

Therefore, when the above-described constant current circuit device is integrated into a semiconductor chip, it is preferable that the power consumption in the IC be as small as possible from the viewpoint of avoiding such problems.

The present invention was created in view of the problems in the prior art described above, and provides a constant current circuit device that reduces power consumption, improves reliability as a device, and reduces circuit scale. The purpose is to

[Means for solving problems]

The above-described problems in the prior art can be solved by making the value of the power supply voltage supplied to the current adjustment circuit smaller than at least the value of the power supply voltage supplied to the constant current circuit.

Therefore, according to the present invention, as shown in the principle block diagram of FIG. The second predetermined voltage VCC2 is lower than the predetermined voltage.
power supply line L2, and a voltage/current conversion circuit l that converts a predetermined reference voltage VR into a predetermined current ICo using a resistor R.
and receives voltage VCCI from the first power supply line,
a first current IC according to the magnitude of the predetermined current ICo;
I and a second current IC according to the magnitude of the first current
2 and a constant current circuit 2 that receives a voltage VCC2 from a second power supply line, and when the second current changes, the current changes in a direction that cancels out the change and has a thickness that corresponds to the change. a current adjustment circuit 3 that generates a third current IC3 having a voltage of A constant current circuit device is provided which controls and outputs the second current at a constant value based on the first current adjustment using the current.

[Operation] According to the above-described configuration, the current adjustment circuit 3 generates the third current IC3 for canceling the change when the second current IC2, that is, the output current changes, and By adjusting the first current ICI of the constant current circuit 2 based on the current of No. 3, the above-mentioned output current IC2 is adjusted to be constant.

At this time, current IC4 flows from the low-level power supply line L2 to the constant current circuit 2 side in the current adjustment circuit 3, so that (
A power consumption corresponding to the voltage VCC2×current IC4) occurs. However, in this case, as is clear from the comparison with FIG. 3 showing an example of the conventional type, the value of the power supply voltage VCC2 supplied to the current adjustment circuit 3 is smaller than the value of the power supply voltage VCCI supplied to the constant current circuit 2. Since it is reduced from the value,
The amount of power consumption is reduced according to the amount of voltage reduction.

Therefore, the generation of heat within the chip is suppressed by the amount of power consumption reduced, making it possible to prevent a decrease in operational reliability due to temperature rise within the circuit, and also to save space for heat dissipation. Since it is not necessary to make the area wide, it can also contribute to reducing the circuit scale.

〔Example〕

FIG. 2 shows a circuit configuration of a constant current circuit device as an embodiment of the present invention. The device shown in the figure shows a circuit configuration integrated within a semiconductor chip, and the same reference numerals as those shown in FIG. 1 represent the same components.

In the voltage/current conversion circuit 1, the emitters of PNP transistors Tll and T12 are connected to resistors R11 and T12, respectively.
It is connected to the high-level power supply line LL (voltage VCCI = 12V in this embodiment) via R12, and the collector of the transistor Tll is connected to the bases of both transistors and to the collector of the NPN transistor T13. . The collector of transistor TI2 is N
It is connected to the base of the PN transistor T15 and to the collector of the NPN transistor T14. The collector of the transistor T15 is connected to the power supply line L1 via the resistor R15, and the emitter thereof is connected to the base of the transistor T160. The emitter of this transistor T16 is connected to the node N via a resistor RL6. On the other hand, a predetermined reference voltage VR (6V in this embodiment) is input to the base of the transistor T13 via a resistor R13, and its emitter is commonly connected to the emitter of the transistor T14, It is connected to a ground terminal GND (OV) via a current source 10. The base of transistor T14 is resistor R
14, and a resistor R is inserted between the node N and the ground terminal GNDO. In this embodiment, this resistor R is built into the chip, but it may be externally connected to the outside of the chip, for example, via the terminal To (indicated by a broken line).

In the constant current circuit 2, the emitters of PNP transistors T21 and T22 are connected to the power supply line L1 via resistors R21 and R22, respectively.
The collector of is connected to the base of a PNP transistor T23, and is connected to the transistor T23 via a resistor R23.
It is connected to 16 collectors.

The collector of transistor T22 is connected to its base and the base of transistor T21, and is also connected to the emitter of transistor T23.

The collector of this transistor T23 is connected to the base of an NPN transistor T24, and the resistor R, 2
NPN transistor T whose emitter is grounded through 5
It is connected to 25 collectors. Transistor T24
The collector of is connected to the low power supply line L2 (voltage VCC2=5 V in this embodiment), and the emitter thereof is connected to the ground terminal GND via a resistor R24.

In the constant current circuit 2, an NPN transistor
'The collector of T26 is connected to the output terminal 0LIT,
A bias circuit 20 is connected to its base, and its emitter is connected to n NPN transistors T271 to T27.
n collectors. Transistor T27
．． Each emitter of ~T27n is connected to a resistor R27, ~R
27, is connected to the ground terminal GND. In addition, transistors T28 and T29 each have a resistor R
It is connected to the ground terminal GND via 2B and R29. And transistor T25, transistor T27
1-T27. , the bases of transistors T28 and T29 are connected in common and also connected to the emitter of transistor T24.

In the current adjustment circuit 3, the NPN transistor T31
The collector of is connected to the power supply line L2, and the emitter is connected to the collectors of transistors T2B and T29. The base of this transistor T31 is connected to the emitter of an NPN transistor T32, and the collector of the transistor T32 is connected to the aforementioned node N. Resistors R31 and R32 connected in series are inserted between the power supply line L2 and the ground terminal GNDO, and the base of the transistor T32 is connected to the connection point of the resistors.

Next, the operation of the circuit shown in FIG. 2 will be explained.

First, in the voltage/current conversion circuit 1, the transistor TI
L T12 and resistors R11 and R12 constitute a current mirror circuit. Therefore, when the transistor T13 is turned on by the reference voltage VR, the same amount of current 12 as the current 11 flowing through the transistor Tll flows through the transistor TI2.
, the same voltage as the reference voltage, ie, 6V, appears at the node N. A predetermined current IC is generated using this 6V reference voltage and resistor R.

flows. On the other hand, as the current 12 flows, the transistor T15 is turned on, and further the transistor T16 is turned on. As a result, the transistor T21 in the constant current circuit 2 receives the above-mentioned predetermined current IC.

A current ICI flows according to the magnitude of .

In the constant current circuit 2, the transistors T2L and T22 and the resistors R21 and R22 constitute a current mirror circuit. Therefore, on the line side including transistor T22,
A current i3 of the same amount as the current ICI flows through the transistor T21. As this current i3 flows, the transistor T24 turns on, and as a result, the potential of the bases of the transistor T25, transistors T27, ~T27°, transistors 728 and T29 is raised to approximately 1V by the value of the resistor R25, and each transistor All are turned on. Transistor T25 and resistor R
25 are transistors 7271 to T27n and resistor R
271 to R27°, and a current mirror circuit is also formed between transistors T28 and T29 and resistors R28 and R29. Therefore, the same amount of current i3 as the above-mentioned current i3 flows through each transistor. In this case, when the transistor T26 is on, a current n times the current i3 flows through the output terminal OUT as the output current IC2.

That is, the constant current circuit 2 supplies a current ICI corresponding to the magnitude of the above-mentioned predetermined current ICo to the voltage/current conversion circuit 1 side, and also supplies the current ICI (i.e., current i3) to the voltage/current conversion circuit 1 side.
Output current IC2 (i.e. 13Xn) according to the magnitude of
It has the function of supplying to the terminal OUT.

In the current adjustment circuit 3, the transistor T32 is connected to the resistor R.
It is in the on state due to the voltage division ratio of R31 and resistor R32,
Therefore, since a potential of approximately 3V is applied to the base of the transistor T31, the transistor T31 is turned on. As a result, the transistor 72B in the constant current circuit 2 is connected to the power supply line L2 via the transistor T31.
And current IC4 flows to the collector side of T29. In this case, the current IC4 is approximately twice the current i3 described above. Then, as this current IC4 flows, the transistor T3 is transferred from the node N to the transistor T3 depending on the magnitude of the current IC4.
A current IC3 flows through the collector of 2.

Therefore, when the output current IC2 of the constant current circuit 2 changes, the output current I
When C2 changes, the adjustment current IC3 is applied in a direction that cancels out the change and has a magnitude corresponding to the change.
is generated, whereby the current ICI flowing through the transistor T21 is adjusted, and the current i3 is adjusted by the action of the current mirror circuit, and as a result, the output current IC2
is automatically controlled to be constant with respect to ICo.

At this time, the transistor T31 in the current adjustment circuit 3 receives a current IC4 based on the power supply from the low-level power supply line L2.
will flow, and power equivalent to (voltage VCC2 x current IC4) will be consumed in the current adjustment circuit 3 due to this current IC4. However, this amount of power consumption is the amount of power consumed in the configuration shown in FIG. It has been reduced compared to consumption.

In other words, the temperature rise in the circuit is suppressed to the extent that the power consumption in the current adjustment circuit is reduced.
The operational reliability of C can be improved, and it can also contribute to reducing the circuit scale.

〔Effect of the invention〕

As explained above, according to the constant current circuit device of the present invention,
Power consumption of the entire circuit can be reduced.

Additionally, although this device is integrated within a semiconductor chip,
The above-mentioned reduction in power consumption suppresses the temperature rise within the chip, which increases the reliability of circuit operation, and furthermore, reduces the circuit scale because there is no need to take up a large space for heat dissipation. can also contribute.

[Brief explanation of drawings]

Fig. 1 is a principle block diagram of a constant current circuit device according to the present invention, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Fig. 3 is a block diagram showing the configuration of a constant current circuit device as an example of a conventional type. Figure, is. (Explanation of symbols) 1... Voltage/current conversion circuit, 2... Constant current circuit, 3... Current adjustment circuit, ICo, ICI, IC2, IC3, IC4-current, LL
, L2...power supply line, VCCI, VCC2...predetermined voltage, VR...reference voltage, R...resistance, T31. T31...transistor.

Claims (1)

[Claims] 1. A constant current circuit device integrated in a semiconductor chip, comprising: a first power supply line (L1) having a predetermined voltage (VCC1); and a predetermined voltage (VCC2) lower than the predetermined voltage; ), a voltage/current conversion circuit (1) that converts a predetermined reference voltage (VR) into a predetermined current (ICo) using a resistor (R), and the first power supply line A first current (IC1) corresponding to the magnitude of the predetermined current (ICo) and a second current (IC2) corresponding to the magnitude of the first current are supplied. A constant current circuit (2) that generates a voltage (VCC2) supplied from the second power supply line, and when the second current changes, generates a constant current in a direction that cancels out the change and a magnitude corresponding to the change. a current adjustment circuit (3) that generates a third current (IC3) having a current of A constant current circuit device, wherein the second current is controlled to be constant based on the first current adjustment by the third current based on the voltage supply of the constant current circuit device. 2. The current adjustment circuit (3) includes a first transistor (T31) connected between the second power supply line (L2) and the constant current circuit (2); said third current (IC3) when connected to the base and conductive;
A second transistor (T32) that generates from the second power supply line (L2) to the constant current circuit (2
2. The constant current circuit device according to claim 1, wherein the current (IC4) is configured to flow on the side (IC4). 3. The constant current circuit device according to claim 1, wherein the resistor (R) is a resistor built into the semiconductor chip. 4. The constant current circuit device according to claim 1, wherein the resistor (R) is a resistor externally attached to the semiconductor chip.