JP2005215843A - Voltage variation type regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage variation type regulator whose output precision is high, and whose costs are low. <P>SOLUTION: This regulator IC1 is provided with a power source 2 being the generation source of an internal reference voltage (Vref), a comparator 3, and a power transistor 4. A terminal a (pin) for input voltage, a pin b for output voltage, a pin c for output voltage adjustment, and a pin d for ground are installed in the periphery of the package of the regulator IC1. As regards an external resistance, only one R3 being a fixed resistance is connected between an adjustment pin c and ground. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a voltage variable regulator that outputs a variable voltage using a single external resistor.

  As the power supply circuit is made into an IC, a three-terminal regulator capable of obtaining various output voltages as a stabilized power supply is used in various fields. In digital home appliances and personal computer (PC) peripheral devices, power supply voltages (for example, 5 V, 3.3 V, 2 V, 2 V, and so on) that have been generally used in the past due to recent advances in semiconductor processes and higher device operation speeds. 0.5V, etc.) cannot be handled, and a finer voltage is required. For this reason, it has become necessary to design the regulator while adjusting the output voltage of the regulator to be used in units of 0.1 V at the design stage of the device.

  In the case of a regulator with a fixed output voltage, it is possible to adjust the output voltage to a predetermined voltage (constant voltage) before shipping in the semiconductor IC manufacturing process. However, it is difficult to adjust the output voltage to a different voltage at the design stage of the corresponding device with respect to the regulator whose output voltage has been adjusted once. Further, a regulator that generates an output voltage other than a general output voltage is handled as a custom product, and there is a problem that the cost of a single regulator increases.

  Thus, when an output voltage different from a general-purpose output voltage is required for the power supply circuit of the corresponding device, an output voltage variable regulator is used. FIG. 3 is a circuit diagram illustrating an example of a variable output voltage regulator. In FIG. 3, the regulator IC 1 is provided with a power source 2, a comparator 3, and a power transistor (control element) 4 that are sources of an internal reference voltage (Vref).

  A power supply 2 for supplying an internal reference voltage (Vref) is connected to a non-inverting input terminal (+ terminal) of the comparator 3. The inverting input terminal (− terminal) of the comparator 3 is connected to the adjustment pin c. The output terminal of the comparator 3 is connected to the base of the power transistor 4. The power transistor 4 (control element) has a collector connected to an input voltage terminal a and an emitter connected to an output voltage terminal b.

  Also, there is an input voltage terminal, that is, an input voltage pin (hereinafter referred to as a pin) a (pin symbol VCC, where VCC is an input voltage Vi supplied to the regulator IC around the regulator IC1 package. Voltage b), an output voltage pin b (pin symbol VOUT), an output voltage adjustment pin (pin symbol ADJ), and a ground pin d (pin symbol GND). R1 and R2 are external resistors and divide the output voltage. The resistor R1 is connected between the pin b and the pin c, and the resistor R2 is connected between the pin c and the ground.

In the case of the regulator of FIG. 3, when the output voltage of the comparator 3 is applied to the base of the power transistor 4, the input voltage Vi (for example, a constant voltage of DC 5V) is applied to the input pin a of the regulator IC1. Then, a current flows through the collector of the power transistor 4 and the power transistor 4 becomes conductive. A predetermined current flows through the emitter of the power transistor 4, and an output voltage is obtained from the output pin b of the regulator IC1. In this case, the output voltage (V0) is expressed by the following equation (1): Output voltage (V0) = Vref (V) · {(R1 + R2) / R2}
= Vref (V). {1+ (R1 / R2)} (1)
Determined by.

  Patent Document 1 describes another form of variable voltage regulator. In this voltage variable regulator, instead of the voltage dividing resistors R1 and R2 in FIG. 3, a variable resistor is connected and the voltage dividing ratio of the resistor is changed by moving the slider.

JP-A-9-138207

  In the example of FIG. 3, two external resistors R1 and R2 are connected to the regulator IC1. The resistance value of the external resistor may vary due to minute differences such as materials and parts processing of each lot in the manufacturing process. Also, the resistance value may fluctuate due to the influence of ambient temperature and wiring impedance. For this reason, for example, in a generally used resistor (carbon film resistance, thick film chip resistance, etc.), an error of (± 5%) in the resistance value with respect to the reference value is allowed. Therefore, there is a problem that the output voltage (V0) fluctuates due to the resistance values of the resistors R1 and R2 to be connected.

  Therefore, more accurate resistors (metal film resistors, precision chip resistors) are used in high frequency circuits, etc., but they are expensive and cannot be used in circuits that require cost reduction such as power supply circuits. there were. Furthermore, since the resistance value of the external resistor is greatly affected by the change in the ambient temperature as described above, there is a restriction that the peripheral components that involve heat dissipation must be reduced.

  Further, since the technique described in Patent Document 1 uses a variable resistor, there is a problem that a driving component for moving the slider is required, and the configuration becomes complicated. Furthermore, since it is necessary to precisely adjust the resistance value for determining the voltage dividing ratio, there is a problem that complicated processing is required.

  The present invention has been made in view of such problems of the prior art, and its purpose is to reduce the number of external parts (cost reduction and space saving) and to increase the accuracy of the output voltage. It is to provide a variable voltage regulator that can be realized.

  The variable voltage regulator of the present invention that achieves the above object is provided with at least an input voltage terminal, an output voltage terminal, and an output voltage adjustment terminal in a regulator IC having a reference voltage source inside. A voltage variable regulator that outputs a voltage different from the reference voltage from the output voltage terminal, wherein a single fixed resistor is connected to the output voltage adjustment terminal.

  According to the present invention, a control element connected to the input voltage terminal and the output voltage terminal is provided in the regulator IC, and the control element is formed based on the voltage of the reference voltage generation source. It is characterized by being controlled by a signal.

  In the present invention, the regulator IC includes a terminal to which a voltage from the reference voltage generation source is applied, and a terminal to which a signal from a connection point between two built-in series-connected resistors is input. And a control unit is controlled by an output signal from the comparator.

  The present invention is characterized in that an operational amplifier is used as the comparator.

  Further, the present invention is characterized in that a voltage obtained by stepping down the reference voltage is output based on a voltage division ratio between two resistors connected in series and the single fixed resistor.

  Further, the present invention is characterized in that one end of the two resistors connected in series is connected to the terminal of the output voltage, and the other end is connected to the terminal for adjusting the output voltage.

  The present invention is characterized in that a voltage obtained by boosting the reference voltage is output based on a voltage division ratio between the two resistors connected in series and the single fixed resistor.

  Also, the present invention is characterized in that one end of the two resistors connected in series is connected to the ground, and the other end is connected to the output voltage adjusting terminal.

  According to the present invention, the control element is a power transistor.

  Further, the present invention has a configuration in which different output voltages can be obtained with respect to the same reference voltage by changing connection of resistors having different resistance values to the output voltage adjusting terminals as the fixed resistors. Features.

  The variable voltage regulator according to the present invention has the following special effects. (1) The number of parts can be reduced. Since there is only one external resistor, the number of external resistors is reduced as compared with the conventional one, so that the cost can be reduced and the mounting board can be saved. (2) The voltage output accuracy can be improved. Since the conventional variable output voltage regulator requires two external resistors, variations in the external resistors (two) affect the accuracy of the output voltage in addition to the voltage output accuracy of the regulator IC alone. ing.

  Actually, since the ambient temperature and the impedance of the wiring pattern on the substrate of the regulator IC and the external resistor are also affected, the output voltage range tends to expand with respect to the design value. On the other hand, in the present invention, since there is only one external resistor, the influence of the ambient temperature is small, and the influence of the impedance of the wiring pattern is reduced, so that the accuracy of the output voltage can be improved. . In addition, in an LSI such as a CPU, DSP, or memory used in equipment, the power supply voltage usage range is typically VCC ± 10%. Recently, with the miniaturization of semiconductor processes, the power supply voltage range is becoming narrower, and taking into account the surrounding temperature change and wiring impedance, it is difficult to cope with the conventional voltage output variable regulator. In the present invention, a single fixed resistor is used as the external resistor, and a fine response can be made by changing the connection of fixed resistors having different resistance values.

  The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an example of an embodiment of the present invention. In FIG. 1, the same parts as those in the conventional example of FIG. In the example of FIG. 1, as compared with the conventional example shown in FIG. 3, some of the two external resistors connected to the regulator IC 1 are formed in the regulator IC 1. The external resistor is different in that only one of the fixed resistors R3 is connected between the adjustment pin c and the ground. In addition, although the operational amplifier (operational amplifier) is used as the comparator 3 in the example of FIG. 1, other types of comparison circuits, for example, a logic operation circuit or a transistor circuit can also be used.

In the example of FIG. 1, a series circuit of resistors R1 and R2 is connected between the emitter of the power transistor 4 and the adjustment pin c of the regulator IC1. Then, the connection point of both resistors is connected to the inverting input terminal (− terminal) of the comparator 3. In this example, it is configured as a step-down variable regulator, and the output voltage V0 of the regulator IC1 is expressed by the following equation (2): V0 = Vref (V) · {(R1 + R2 + R3) / (R2 + R3)}
= Vref (V). {1+ [R1 / (R2 + R3)]} (2)
It becomes.

  Here, for example, if Vref = 1.5 V, R1 = 10 KΩ, R2 = 3 KΩ, and R3 = 0Ω, the output voltage V0 is V0 = 1.5 × {(10) / (3 + 0)} = 5V. In the circuit of FIG. 1, it is clear from the equation (2) that the output voltage V0 is lower than 5 V by increasing the resistance value of the external resistor R3. That is, a variable voltage regulator that reduces the output voltage by increasing the resistance value of the external resistor R3 is configured.

  FIG. 2 is a circuit diagram showing an example according to another embodiment of the present invention. In the example of FIG. 2, the external resistor R3 is connected between the output pin b and the adjustment pin c. A series circuit of resistors R1 and R2 formed inside the regulator IC1 is connected between the adjustment pin c and the ground. The resistor R2 may be connected to the ground pin d. Also in the example of FIG. 2, the connection point of the resistors R <b> 1 and R <b> 2 is connected to the inverting input terminal (− terminal) of the comparator 3 as in FIG. 1.

The output voltage V0 of the regulator IC1 in FIG. 2 is expressed by the following equation (3): V0 = Vref (V) · {(R1 + R2 + R3) / (R2)}
= Vref (V) · {1 + [(R1 + R3) / (R2)] (3)
It becomes. The example of FIG. 2 constitutes a step-up variable regulator.

  In FIG. 2, for example, assuming that Vref = 1.5V, R1 = 10KΩ, R2 = 3KΩ, and R3 = 0Ω, the output voltage V0 is V0 = 1.5 × (10 + 0) / 3 = 5V from equation (3). Become. Here, when the resistance R3 is increased, the output voltage V0 increases from the equation (3). That is, a variable voltage regulator that boosts the output voltage by increasing the resistance value of the external resistor R3 is configured.

  Next, an example of the present invention will be described in comparison with a conventional example. FIG. 5 is an explanatory diagram showing an example of characteristics of a conventional example. FIG. 5 shows an internal reference voltage Vref (V), external resistors R1 (Ω), R2 (Ω), an output voltage V0 (V), and an accuracy V0 + α of the design value with respect to the output voltage in the circuit diagram shown in FIG. (%), Remark items are set.

  For the internal reference voltage Vref (V), a minimum voltage of 1.455 V, which is −3% with respect to the design value of 1.5 V, is set. Also, ± 0% (standard value) is set for the design value of 1.5V. Furthermore, + 45% of 1.545V is set with respect to the design value of 1.5V. Next, for the external resistor R1, the design value 10KΩ, −5% 9.5KΩ, and + 5% 10.5KΩ for the standard value and ± 3% of each internal reference voltage Vref (V), respectively. Set. That is, a resistance value in a range of ± 5%, which is an allowable value for the design value (accuracy of a commonly used resistor), is set.

  The resistance value of the external resistor R2 sets parameters in more detail. That is, the resistance value of the resistor R2 is set to the design value of each internal reference voltage Vref (V) and the ± 3% of the design value of the external resistor R1, and the range of ± 5% thereof. A design value of 7.5 KΩ and a resistance value within a range of ± 5% are set. Therefore, the resistance value of the external resistor R2 is set to a design value of 7.5 KΩ with respect to the nine combinations of the internal reference voltage Vref (V) and three combinations for each resistance value of the external resistor R1. And 7.125 KΩ and 7.875 KΩ which are ± 5% of the range.

  The output voltage V0 describes the result calculated by the equation (1) for each resistance value of the external resistor R2. As the output accuracy, a result obtained by calculating a deviation with respect to the design value of 3.5 V by ±% is described. In the example of FIG. 5, the accuracy of the output voltage V0 is 3.210V (−8.28%) for the minimum voltage and 3.822V (+ 9.20%) for the maximum voltage with respect to the design value of 3.5V. Yes.

  FIG. 4 is an explanatory diagram showing characteristics corresponding to the circuit diagram of FIG. In this example, the internal reference voltage Vref (V), the resistors R1 (Ω) and R2 (Ω) formed in the regulator IC, the external resistor R3 (Ω), the output voltage V0 (V), and the design output voltage The accuracy V0 + α (%) and remark items are set.

  As for the internal reference voltage Vref (V), similarly to the example of FIG. 5, ± 0% (standard value), ± 3% of 1.545 V, and 1.455 V are set with respect to the design value of 1.5 V. The design value of the resistor R1 formed inside the regulator IC is 10 KΩ, but it is within the range of ± 3% of the voltage output accuracy in accordance with the internal reference voltage Vref (V) when the regulator IC is manufactured. The tolerance is formed to be ± 0%. Similarly, the resistance value of the resistor R2 formed in the regulator IC is a designed value of 3 KΩ, but in this case as well, the tolerance is ± 0%.

  The resistance value of the external resistor R3 has a design value of 4.5 KΩ, and a standard value of ± 0% of the design value and a tolerance value (accuracy of commonly used resistors) in the range of ± 5% Set the resistance value. These resistance values correspond to ± 0% (standard value) and ± 3% (allowable value) of the internal reference voltage Vref (V), respectively. Accordingly, the output voltage (V0) has nine values with respect to the internal reference voltage Vref (V).

  4 is intended for the step-down variable regulator shown in FIG. 1. As described above, when the resistance value of the external resistor R3 increases, the output voltage (V0) decreases, and the resistance value of the external resistor R3 becomes smaller. When it decreases, the output voltage (V0) increases. Therefore, in the example of FIG. 4, when the internal reference voltage Vref is small at −3% of the design value and the resistance value of the external resistor R3 is large at + 5% of the design value, the output voltage (V0) is the lowest value. 3.338V. In this case, the output accuracy is -4.61%. When the internal reference voltage Vref is large at + 3% of the design value and the resistance value of the external resistor R3 is small at -5% of the design value, the output voltage (V0) is the maximum value of 3.669V. . In this case, the output accuracy is + 4.82%.

  The conventional example shown in FIG. 5 is compared with the present invention shown in FIG. 4 when the design value of the output voltage (V0) is 3.5V. In the conventional example, the minimum voltage is 3.210 V (−8.28% with respect to the design value), and the maximum voltage is 3.822 V (+ 9.20% with respect to the design value). On the other hand, in the present invention, the minimum voltage is 3.338V (−4.61% with respect to the design value), and the maximum voltage is 3.669V (+ 4.82% with respect to the design value). Therefore, the present invention can provide an output accuracy that is approximately twice that of the conventional example.

  The embodiment of the present invention has been described above. The present invention is not limited to these examples, and various modifications are possible. For example, as the fixed resistor R3, the same reference voltage Vref can be obtained by connecting a resistor (5 KΩ, 3 KΩ, etc.) having a resistance value different from 4.5 KΩ described in FIG. 4 to the output voltage adjusting terminal c. For example, a different output voltage (V0) can be obtained.

  As described above, according to the present invention, a voltage variable regulator with high output accuracy and low cost can be provided.

It is a circuit diagram showing an embodiment of the present invention. It is a circuit diagram which shows other embodiment of this invention. It is a circuit diagram which shows a prior art example. It is explanatory drawing of this invention. It is explanatory drawing of a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Regulator IC, 2 ... Power supply of an internal reference voltage, 3 ... Comparator, 4 ... Power transistor, a ... Input voltage pin, b ... Output voltage pin, c. ..Output voltage adjustment pins, d ... grounding pins

Claims (10)

A regulator IC having a reference voltage generation source therein is provided with at least an input voltage terminal, an output voltage terminal, and an output voltage adjustment terminal, and a voltage different from the reference voltage is applied from the output voltage terminal. A variable voltage regulator for output, wherein a single fixed resistor is connected to the output voltage adjusting terminal. A control element connected to the input voltage terminal and the output voltage terminal is provided in the regulator IC, and the control element is controlled by a signal formed based on the voltage of the reference voltage generation source. The voltage variable regulator according to claim 1, wherein: Provided inside the regulator IC is a comparator having a terminal to which a voltage from the reference voltage generation source is applied and a terminal to which a signal from a connection point between two built-in series-connected resistors is input, The voltage variable regulator according to claim 2, wherein the control element is controlled by an output signal from a comparator. The voltage variable regulator according to claim 3, wherein an operational amplifier is used as the comparator. The voltage obtained by stepping down the reference voltage is output based on a voltage division ratio between the two resistors connected in series and the single fixed resistor. The voltage variable regulator described. 6. The voltage variable regulator according to claim 5, wherein one end of the two resistors connected in series is connected to the terminal of the output voltage, and the other end is connected to the terminal for adjusting the output voltage. . The voltage obtained by boosting the reference voltage is output based on a voltage dividing ratio between the two resistors connected in series and the single fixed resistor. The voltage variable regulator described. 8. The variable voltage regulator according to claim 7, wherein one end of the two resistors connected in series is connected to the ground, and the other end is connected to the output voltage adjusting terminal. 9. The voltage variable regulator according to claim 1, wherein the control element is a power transistor. The configuration is characterized in that, as the fixed resistor, a resistor having a different resistance value is connected to the output voltage adjusting terminal so that different output voltages can be obtained with respect to the same reference voltage. The voltage variable regulator according to any one of claims 1 to 9.

Images