JP2014063288A - Current generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current generation circuit capable of adjusting output currents or an output voltage to a target value, and minimizing the temperature dependency of the output currents or the output voltage without increasing power consumption and a startup time.SOLUTION: A current generation circuit capable of minimizing the temperature characteristics of an output voltage or currents, and adjusting an output value to a target value includes: one current source 10 having one current adjustment circuit 11 for outputting currents IC31 having temperature characteristics in a first direction; the other current source 20 having the other current adjustment circuit 22 for outputting currents IC32/n having temperature characteristics in a second direction which is reverse to the first direction; and a current addition circuit 30 for adding the respective currents IC31 and IC32/n generated by the two current sources 10 and 20 by a rate n:1 to minimize temperature dependency, in which the two current adjustment circuits 11 and 22 respectively owned by the two current source 10 and 20 are simultaneously adjusted on the basis of the output value and the target value.

Description

  The present invention relates to a current generation circuit, and more particularly to a current generation circuit capable of minimizing temperature characteristics.

  Generally, in a current generation circuit capable of supplying a constant current or a constant voltage, it is required to consider temperature characteristics with respect to an ambient temperature or a component temperature of about −30 ° C. to 85 ° C. Therefore, it is known to perform temperature compensation so that the voltage or current that is the output of the current generation circuit does not vary from a desired set value due to temperature characteristics.

  For example, the constant current circuit described in Patent Document 1 is a constant current circuit that can generate and supply a plurality of constant currents with high accuracy, in which fluctuations in output values due to manufacturing processes and temperature characteristics are reduced. is there. This constant current circuit cancels the temperature coefficient of the output current of the transistors constituting the circuit, and by selecting the temperature coefficient of the resistor inserted in series with the PMOS transistor between the power supply voltage and the ground voltage, The temperature coefficient with respect to the drain current of the transistor can be made very small. The variation in resistance value and temperature coefficient of the resistor is about ± 5% in resistance value and about ± 5% in temperature coefficient (−30 ° C. to 85 ° C.). The range of current variation can be managed. Therefore, the constant current circuit can obtain a highly accurate reference current value by appropriately selecting the temperature coefficient of the resistance described above.

  The constant current circuit described in Patent Document 2 is a constant current circuit that performs temperature compensation by adding outputs of current sources having temperature characteristics in different directions. The constant current output of the constant current circuit is passed through the load resistance to output a stable voltage. The temperature-compensated constant voltage output enables driving with a low voltage of 1 V or less such as a nickel-cadmium battery. The constant voltage circuit includes a battery 1, a band gap current mirror type constant current source circuit 3 that outputs a collector current IC9 of a transistor Q9 having a positive temperature coefficient, and a negative voltage defined by a base-emitter voltage VBEQ7 of the transistor Q7. A current source circuit 5 that outputs a collector current IC8 of a transistor Q8 having a temperature coefficient of λ and a load resistance element R0. At node N0, collector current IC9 and collector current IC8 are added. The temperature coefficients of both currents are offset, and the current at the node N0 has no temperature dependence. The load resistance element R0 converts this current into a voltage and outputs it as an output voltage Vout.

  FIG. 1 is a block diagram for explaining the configuration of a conventional current generation circuit. The current generation circuit 5 shown in FIG. 1 minimizes the temperature characteristic of the output voltage or current and outputs it to the output terminal OUT4. The current generation circuit 5 includes two sets of current sources 1 and 2 and a current addition circuit 3 that adds the currents IC11 and IC12 / n output from the current sources 1 and 2 and outputs the result to the output terminal OUT4. It is prepared for.

FIG. 2 is a temperature characteristic diagram of the generated current for explaining the operation of the current generating circuit shown in FIG.
As shown in FIG. 2, the output IC 11 of the current source 1 has a positive temperature characteristic in which the current value increases as the temperature rises. Conversely, the output IC 12 of the current source 2 has a negative temperature characteristic in which the current value greatly decreases as the temperature rises. Here, the current adding circuit 3 adds the current IC11 having a positive temperature characteristic and the current IC12 having a temperature characteristic that is -n times that of the current IC11 at a ratio of n: 1. In other words, by setting IC13 = IC11 + IC12 / n shown to be output from the output terminal 4 of FIG. 1, the current adding circuit 3 causes the current IC11 and IC12 to act on the current IC11 and IC12 in the opposite directions n times. And the current IC13 with the temperature dependence minimized can be generated. As a result, the current generation circuit 5 outputs a current IC13 having no temperature dependency from the output terminal OUT4.

JP 2006-109349 A JP-A-5-241672

  However, in the constant current circuit described in Patent Document 1 described above, in order to reduce the temperature coefficient of the drain current of the PMOS transistor, the temperature of the resistor inserted in series with the PMOS transistor is between the power supply voltage and the ground voltage. It is necessary to select a resistor having an appropriate temperature characteristic so as to cancel out by the coefficient. The process of selecting a resistor having an appropriate temperature characteristic is not automatically performed in the constant current circuit manufacturing process. Therefore, there is a drawback that an automatic temperature compensation function for a constant current circuit that is mass-produced including variations in temperature characteristics due to various factors is scarce.

Further, the constant current circuit described in Patent Document 2 does not consider the influence of process variations and the like, and the collector currents IC8 and IC9 added at the node N0 may deviate from the original target values.
Further, the conventional constant current circuit 5 shown in FIGS. 1 and 2 does not consider the influence of process variations and the like, and the generated current IC 13 may deviate from the original target value. Further, when an adjustment circuit (not shown) is added to the subsequent stage of the output terminal OUT4 of the current adding circuit 3 in order to reduce the influence of variation, there arises a problem that current consumption and startup time increase.

  Another configuration is also conceivable in which only one side of the current IC 11 or the current IC 12 in FIG. 1 is adjusted inside the current source 1 or the current source 2. In this case, the current value of the IC 13 at a certain temperature can be brought close to the target value without increasing the current consumption and the startup time. However, in this case, the ratio of adding IC11 and IC12 that has been set to eliminate the temperature characteristic is lost, which causes a problem that temperature dependency occurs in the IC13.

  The present invention has been made in view of such a problem. The object of the present invention is to adjust the output current or the output voltage to the target value without increasing the power consumption and the start-up time, and to adjust the output current or the output voltage. An object of the present invention is to provide a current generation circuit capable of minimizing voltage temperature dependency.

  The present invention has been made to achieve such an object, and the invention according to claim 1 can minimize the temperature characteristic of the output voltage or current and adjust the output value to the target value. In the current generation circuit, one current source (10) having one current adjustment circuit (11) and outputting a current (IC31) having a temperature characteristic in the first direction, and the other current adjustment circuit (22) are provided. The other current source (20) for outputting a current (IC32 / n) having a temperature characteristic in a second direction opposite to the first direction, and the two current sources (10, 20). A current adding circuit (30) that adds the currents (IC31, IC32 / n) generated in step 1 at a rate (n: 1) that minimizes temperature dependence, and the two current sources (10, 20) Two current regulation circuits (11, 22) each having Characterized in that it is possible to adjust at the same time based on the output value and the target value. (See Figs. 3 and 4)

According to a second aspect of the present invention, in the first aspect of the present invention, the two current adjustment circuits (11, 22) are configured to generate currents (10, 20) generated by the two current sources (10, 20). IC31, IC32 / n) can be adjusted while maintaining the minimization ratio. (See Figs. 3 and 4)
According to a third aspect of the present invention, there is provided the control circuit according to the first or second aspect, further comprising a control circuit (40) for adjusting the two current adjusting circuits (11, 22). .

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the control circuit (40) sets the current value (IC33) added by the current addition circuit (30) to a desired value. The two current adjustment circuits (11, 22) can be adjusted in conjunction with each other so as to be close to each other. (See Figs. 3 and 4)

  According to the present invention, it is possible to realize a current generation circuit that can adjust the output current or the output voltage to the target value and minimize the temperature dependency of the output current or the output voltage without increasing the power consumption and the startup time. it can.

It is a block block diagram for demonstrating the structure of the conventional electric current generation circuit. FIG. 2 is a temperature characteristic diagram of generated current for explaining the operation of the current generating circuit shown in FIG. 1. It is a circuit diagram for demonstrating the structure of the Example of the current generation circuit which concerns on this invention. FIG. 4 is a temperature characteristic diagram of a generated current for explaining the operation of the embodiment of the current generating circuit shown in FIG. 3.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 3 is a circuit diagram for explaining a configuration of an embodiment of the current generating circuit according to the present invention. The current generation circuit 100 shown in FIG. 3 minimizes the temperature characteristic of the output voltage or current, adjusts the output value to match the target value, and outputs it to the output terminal OUT50. The current generation circuit 100 includes two sets of current sources 10 and 20, current adjustment circuits 11 and 22 included in the current sources 10 and 20, and current ICs 31 and 22 that are adjusted and output by the current adjustment circuits 11 and 22, respectively. The current adding circuit 30 adds the ICs 32 / n and outputs them to the output terminal OUT50, and the control circuit 40 that adjusts the current adjusting circuits 11 and 22. Further, the control circuit 40 can adjust the output current values of the current adjustment circuits 11 and 22 based on the output value of the output terminal OUT50 and the target value. While the current source 10 outputs the current IC31, the reason why the current source 20 outputs IC32 / n, which is 1 / n of the IC32, and the setting method thereof are as follows.

  The current IC32 having a positive temperature characteristic and the current IC32 having a temperature characteristic that is -n times that of the current IC31 are added at an appropriate ratio to cancel the positive and negative temperature characteristics. As for the setting method, it can be considered that the sizes of the NMOS transistors M1 and M2 are set to n: 1. That is, when the current IC32 flows through the drain of the NMOS transistor M1, the current flowing through the NMOS transistor M2 having a magnitude 1 / n that of the NMOS transistor M1 is IC32 / n.

  One current source 10 has one current adjustment circuit 11 and outputs a current IC 31 having a first direction, that is, a positive temperature characteristic. In the current source 10, an NMOS transistor M3 and a current adjusting circuit 11 are interposed in series between the power supply voltage VCC and the ground voltage G. The output of the operational amplifier 12 is connected to the gate of the NMOS transistor M3, the negative input terminal of the operational amplifier 12 is connected to the connection point between the source of the NMOS transistor M3 and the current adjustment circuit 11, and the positive input terminal of the operational amplifier 12 is connected to the positive input terminal. A reference voltage VREF is applied. The NMOS transistors M3 and M4 have their drains and gates connected in common. An NMOS transistor M4 is connected to the NMOS transistor M3 as a current mirror. When the current IC 31 flows through the source of the NMOS transistor M 3 by the adjustment of the current adjustment circuit 11, the IC 31 having the same value is output from the source of the NMOS transistor M 4 and input to the current addition circuit 30.

  The other current source 20 has the other current adjustment circuit 12 and outputs a current IC 32 / n having a second direction opposite to the first direction, that is, a negative temperature characteristic. In the current source 20, an NMOS transistor M 1, a PMOS transistor Q 3, and a current adjustment circuit 22 are inserted in series between the power supply voltage VCC and the ground voltage G. Further, an NMOS transistor Q1, a PMOS transistor Q2, and a PNP transistor Bip3 are inserted in series between the power supply voltage VCC and the ground voltage G. The drains and gates of the NMOS transistors M1, M2, and Q1 are commonly connected. The gates of the PMOS transistors Q2 and Q3 are connected in common. The NMOS transistor M1 and the PMOS transistor Q3 are connected in a current mirror manner to the NMOS transistor Q1 and the PMOS transistor Q2.

  A current IC 32 set by the current adjustment circuit 22 flows through a series path formed by the NMOS transistor M1, the PMOS transistor Q3, and the current adjustment circuit 22. The current IC32 having the same value as that of the current IC32 also flows through the series path formed by the NMOS transistor Q1, the PMOS transistor Q2, and the PNP transistor Bip3. Further, for example, an IC32 / n current flows through the NMOS transistor M2. The current of the IC 32 / n is output from the source of the NMOS transistor M2, and becomes the current IC33 by joining with the IC 31 at the junction X. The current IC33 = IC31 + IC32 / n is input to the current adding circuit 30.

  Note that a current IC32 flows through the drain of the NMOS transistor M1 in accordance with the resistance value of the variable resistor VR2 by the current adjusting circuit 22. As described above, the current IC 32 / n is set to flow through the source of the NMOS transistor M2 according to the size ratio between the NMOS transistors M1 and M2.

  In the current adding circuit 30, a PMOS transistor Q4 is interposed between the junction X of the current IC 32 / n and the current IC 31 and the ground voltage G. The PMOS transistor Q4 and the PMOS transistor Q5 have their drains and gates connected in common and are current mirror connected. The source of the PMOS transistor Q5 is connected to the output terminal OUT50 of the current adding circuit 30. The drains of the PMOS transistors Q4 and Q5 are connected to the ground voltage G. Therefore, a current having the same value as that of the IC 33 flowing through the PMOS transistor Q4 is generated at the source of the PMOS transistor Q5 and output from the output terminal OUT50.

  In the current adding circuit 30, the current IC31 and IC32 / n generated by the two current sources 10 and 20 are added at such a rate that the positive and negative temperature dependences are canceled and minimized. Since the temperature characteristic of the current IC32 is -n times the temperature characteristic of the current IC31, the temperature characteristic is minimized when the current value IC33 = IC31 + IC32 / n added by the current addition circuit 30 is reached. Thus, the ratio of the current to be added is optimally set according to the directionality and degree of the positive and negative temperature characteristics of each of the currents IC31 and IC32.

  The control circuit 40 can simultaneously adjust the two current adjustment circuits 11 and 22 included in the two current sources 10 and 20 based on the output value and the target value. That is, the control circuit 40 can adjust the two current adjustment circuits 11 and 22 in conjunction with each other so that the current value IC33 added by the current addition circuit 30 approaches a desired value. The two current adjustment circuits 11 and 22 can adjust the currents IC31 and IC32 / n generated by the two current sources 10 and 20 while maintaining a ratio of minimizing the currents.

  These two current adjustment circuits 11 and 22 can individually adjust the currents IC31 and IC32 / n output from the current sources 10 and 20, and the current value IC33 added by the current addition circuit 30 can be set to a desired value. Adjust to get closer to the value. The operation of the current generation circuit 100 will be described below.

  FIG. 4 is a temperature characteristic diagram of the generated current for explaining the operation of the embodiment of the current generating circuit according to the present invention. The output IC 31 of the one current source 10 has a positive temperature characteristic of 1000 ppm / deg in which the current value increases as the temperature rises. Conversely, the output IC 32 of the other current source 20 has a negative temperature characteristic −4000 ppm / deg in which the current value decreases as the temperature rises. That is, the output IC 31 of one current source 10 and the output IC 32 of the other current source 20 have a relationship in the opposite direction between the temperature characteristics. Here, the current adding circuit 30 adds the current IC 31 having a positive temperature characteristic and the current IC 32 / n having a temperature characteristic -4 times that of the current IC 31 at a ratio of 4 to 1. In other words, by setting n = 4 and setting current IC31 = IC32 / 4, the current addition circuit 30 cancels the temperature characteristic that acts four times in the reverse direction, and the current IC33 with minimized temperature dependence is obtained. Can be generated. As a result, the temperature characteristics of the current IC 33 are minimized with respect to the entire temperature, and the current value approaches a constant value. If the temperature characteristics of the current IC31 and IC32 / 4 illustrated here are as shown in the temperature characteristic diagram of FIG. 4, the current IC33 has no temperature dependency with respect to a temperature change over −40 to 120 ° C. .

  However, at this time, when the current values of the currents IC31 and IC32 / 4 deviate from the target values due to process variations or the like, the current IC33 generated by adding the currents IC31 and IC32 / 4 also deviates from the target value. In this case, the control circuit 40 correlates and adjusts the two current adjustment circuits 11 and 22 at the same time. These two current adjustment circuits 11 and 22 can individually adjust the currents IC31 and IC32 / 4 output from the current sources 10 and 20 so as to have an appropriate addition ratio as necessary. That is, the control circuit 40 designates currents IC31 and IC32 / 4 output from the two current adjustment circuits 11 and 22 by specifying an appropriate ratio in order to bring the current value IC33 close to a desired value. Adjust to 30. That is, the control circuit 40 adjusts the currents IC31 and IC32 / 4 to the target values by interlockingly adjusting the adjustment circuit 31 and the adjustment circuit 32. As a result, the current IC33 generated by adding the currents IC31 and IC32 / 4 is also adjusted to the target value.

In the following, the operation procedure for adjusting the currents IC31, IC32 / 4, and IC33 to the target values by interlocking the adjustment circuit 11 and the adjustment circuit 12 will be described in detail.
(1) When the current values of the currents IC31 and IC32 / 4 become smaller than the target value due to process variations or the like, the current IC33 also becomes smaller than the target value. In this case, while the control circuit 40 monitors the value of the current IC 33 output from the output terminal OUT50, the current adjustment circuits 11 and 22 have the variable resistors VR1 and VR2, respectively, and the resistance values have the same ratio. Adjust to decrease. When the monitored current IC 33 approaches the target value, the control circuit 40 determines the resistance values of the variable resistors VR1 and VR2 as adjustment values and ends the adjustment of the current value.

(2) On the contrary, when the current values of the currents IC31 and IC32 / 4 become larger than the target value due to process variations or the like, the current IC33 also becomes larger than the target value. In this case, while monitoring the current IC 33 output from the output terminal OUT50, the current adjustment circuits 11 and 22 adjust the variable resistors VR1 and VR2, respectively, so that the respective resistance values increase at the same rate. When the monitored current IC 33 approaches the target value, the control circuit 40 determines the resistance values of the variable resistors VR1 and VR2 as adjustment values and ends the adjustment of the current value.

According to the present embodiment, it is possible to realize a current generation circuit that can adjust the output current or the output voltage to the target value without increasing the power consumption and the start-up time and minimize the temperature dependence of the output current or the output voltage. Can do.
In the current generation circuit 100 illustrated in FIG. 3, one control circuit 40 adjusts the currents IC31 and IC32 / 4 at the same time by adjusting the resistance values of the variable resistors VR1 and VR2 at the same rate of change. Although it is a structure, it is not limited to the structure. Other configurations may be used as long as the variable resistors VR1 and VR2 can be interlocked and adjusted at the same ratio.

  In addition, the current generation circuit 100 illustrated in FIG. 3 has a configuration in which the currents IC31 and IC32 / 4 are adjusted and adjusted by the variable resistors VR1 and VR2, but the configuration is not limited thereto. Other configurations may be used as long as they can be adjusted simultaneously while maintaining the ratio between the current IC31 and IC32 / 4.

  For example, an equivalent function can be realized by adjusting the size ratio between the pMOS transistors M1 and M2 and the size ratio between the pMOS transistors M3 and M4. Specifically, in the same integrated circuit or the like, pMOS transistors corresponding to M1, M2, M3, and M4 are formed in redundant combinations with different size ratios in stages. Then, the circuit configuration is configured so that the size ratio between M1 and M2 and the size ratio between M3 and M4 can be switched by the size ratio selection switch. If the control circuit 40 appropriately switches and controls the size ratio selection switch, the current IC31 and IC32 / 4 can be adjusted in conjunction with each other.

  In the current generation circuit 100 illustrated in FIG. 4, the output current IC31 having a temperature characteristic of 1000 ppm / deg and the current IC32 having a temperature characteristic of −4000 ppm / deg are added at a ratio of 4: 1. That is, since IC31 has a ratio four times that of IC32, it has been described that the current IC31 and IC32 / 4 are added. However, this is only an example. In other words, the currents IC31 and IC32 are temperature characteristics in opposite directions, and by adding the two currents IC31 and IC32 at an appropriate ratio, the positive and negative temperature characteristics are offset, and the current IC33 Any setting value that can minimize the temperature dependence is acceptable.

1, 2, 10, 20 Current source 3, 30 Current addition circuit 5, 100 Current generation circuit 11, 22 Current adjustment circuit 12 Operational amplifier 40 Control circuit

Claims (4)

In the current generation circuit that can minimize the temperature characteristic of the output voltage or current and adjust the output value to the target value,
One current source having one current adjustment circuit and outputting a current having a temperature characteristic in the first direction;
The other current source having the other current adjustment circuit and outputting a current having a temperature characteristic in a second direction opposite to the first direction;
A current addition circuit that adds each current generated by the two current sources at a rate that minimizes temperature dependence;
A current generation circuit characterized in that two current adjustment circuits respectively included in the two current sources can be adjusted simultaneously based on the output value and the target value.   2. The current generation circuit according to claim 1, wherein the two current adjustment circuits are capable of adjusting the currents generated by the two current sources while maintaining the minimization ratio.   The current generation circuit according to claim 1, further comprising a control circuit for adjusting the two current adjustment circuits.   4. The current according to claim 3, wherein the control circuit is capable of adjusting the two current adjustment circuits in conjunction with each other so that the value of the current added by the current addition circuit approaches a desired value. 5. Generation circuit.

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