JP2007140755A - Voltage regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage regulator with low fluctuation of output voltage against fluctuation of input voltage. <P>SOLUTION: The voltage regulator is constructed in such a way that a circuit for compensating the output voltage with feedback control by detecting the difference of the output voltage and target voltage works by the output voltage of the voltage regulator so that capacitive coupling does not exist between the input voltage and output voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a voltage regulator circuit, and more particularly to a technique for reducing fluctuations in output voltage with respect to fluctuations in input voltage.

Technical background

  In recent years, power consumption has increased with the increase in functionality and circuit scale of electronic devices. An increase in power consumption leads to an increase in power supply voltage fluctuation. In addition, the number of circuits that perform intermittent operation increases from the viewpoint of energy saving, and the power supply voltage varies greatly at the timing of the intermittent operation. Since the voltage regulator operates using the power supply voltage that varies greatly due to these causes as an input, the output voltage varies. The fluctuation of the output voltage of the voltage regulator has various adverse effects on a circuit that operates using the output voltage of the voltage regulator as a power source. A decrease in voltage causes malfunction, and an increase causes breakdown of the breakdown voltage. Furthermore, the continuous voltage fluctuation causes an increase in jitter due to fluctuations in delay time.

  Due to these factors, a voltage regulator is required in which the fluctuation of the output voltage is small relative to the fluctuation of the input voltage (see, for example, Patent Document 1). In general, the ratio of the output voltage fluctuation to the input voltage fluctuation is called PSRR (power supply rejection ratio), and the smaller the PSRR, the better.

  FIG. 15 shows a block diagram of a conventional voltage regulator. A power supply 1, a reference voltage circuit 2, output voltage dividing resistors 3 and 4, an operational amplifier 5, and an output transistor 6, and a phase compensation capacitor 8 for preventing oscillation are provided between the gate and the output terminal of the output transistor 6. Connected between.

  FIG. 16 is an equivalent circuit of the voltage regulator circuit of FIG. When the voltage of the power source 1 is VDD, the resistance values of the dividing resistors 3 and 4 are R3 and R4, the threshold voltage of the output transistor 6 is Vth, and the capacitance of the phase compensation capacitor 8 is C8, the output voltage Vout is expressed by the following equation. .

Vout = (R3 + R4) / ((1 / jωC8) + R3 + R4) × (VDD−Vth) (1)
From Expression (1), it can be seen that the output voltage Vout depends on the power supply voltage VDD.
JP 2000-284843 A

  In the conventional circuit configuration, the output voltage fluctuates according to the fluctuation of the input voltage by inserting the phase compensation capacitor 8 for securing the phase margin.

  The present invention solves the above-described problems and provides a voltage regulator circuit in which the fluctuation of the output voltage is small with respect to the fluctuation of the input voltage.

  According to the voltage regulator of the present invention, the feedback control system circuit for correcting the output voltage by detecting the difference between the fed back output voltage and the target voltage of the output voltage is operated with the output voltage of the voltage regulator.

  According to the voltage regulator of the present invention, the power supply of the circuit of the feedback control system is configured to be obtained from the output voltage of the voltage regulator. Therefore, even if the input voltage varies, the output voltage varies depending on the phase compensation capacitor. Absent.

  A circuit that detects the difference between the output voltage and the target voltage and performs feedback control is configured to operate with the output voltage, and the phase compensation capacitance element is feedback-controlled by detecting the difference between the output voltage and the target voltage. By connecting between the intermediate node and the output terminal of the circuit, there is no capacitive coupling between the input power supply terminal and the output terminal, and the voltage regulator circuit is configured so that the output voltage does not fluctuate due to the fluctuation of the input voltage.

  FIG. 1 is a block diagram showing a first embodiment of a voltage regulator according to the present invention. Power supply 1, output transistor 6, output voltage dividing resistors 3 and 4, constant current source 11 and voltage detection transistor 51 constituting a voltage detection circuit, phase compensation capacitors 81 and 82 for preventing oscillation, output The constant current source 12 that controls the gate of the transistor 6 and the control transistor 52 are configured. A circuit for detecting a difference between the output voltage and the target voltage and performing feedback control is configured by a voltage detection circuit.

  The voltage detection circuit uses the threshold voltage of the N-channel MOS transistor that constitutes the voltage detection transistor 51. The detection voltage can be freely set by adjusting the current of the constant current source 11. The output transistor 6 is configured by a P-channel MOS transistor so that the GND-output voltage is constant.

  The phase compensation capacitors 81 and 82 may be only one or both may be connected.

  According to the voltage regulator of the present invention as described above, the power supply of the circuit of the feedback control system is configured to be obtained from the output voltage of the voltage regulator. Therefore, even if the input voltage varies, the output voltage is reduced by the phase compensation capacitor. It is possible to provide a voltage regulator with stable output without fluctuation.

  FIG. 2 is a block diagram showing a second embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 1, the voltage detection circuit is used to make the GND-output voltage constant, but the output transistor 6 is an N-channel MOS transistor.

  Since the output transistor 6 is an N-channel MOS transistor, it is necessary to add a circuit for inverting logic, a constant current source 13 and a logic inverting transistor 53 to the voltage detection circuit. However, the addition of this circuit is a feedback. This has the effect of increasing the gain of the circuit and improving the characteristics.

  Further, since the output transistor 6 is an N-channel type MOS transistor, there is no capacitive coupling due to the parasitic capacitance of the MOS transistor between the output transistor 6 and the power supply, so that a higher PSRR characteristic than the circuit of FIG. 1 can be obtained.

  FIG. 3 is a block diagram showing a third embodiment of the voltage regulator of the present invention. Like the voltage regulator of FIG. 2, the output transistor 6 is composed of an N-channel MOS transistor and is suitable for a circuit that requires high PSRR characteristics. However, the area of the output transistor 6 is reduced by reducing the number of elements used as compared with FIG. . Suitable for semiconductor devices that prioritize reduction in area.

  FIG. 4 is a block diagram showing a fourth embodiment of the voltage regulator of the present invention. The basic circuit configuration is the same as that of the voltage regulator of FIG. 2, but the input voltage-output voltage is configured to be constant.

  FIG. 5 is a block diagram showing a fifth embodiment of the voltage regulator of the present invention. As in the voltage regulator of FIG. 4, the voltage detection circuit is used to make the input voltage-output voltage constant, but the output transistor 6 is a P-channel MOS transistor. By adopting this configuration, the parasitic capacitance of the MOS transistor does not exist between the ground and GND, so that a higher PSRR characteristic than the circuit shown in FIG. 4 can be obtained.

  FIG. 6 is a block diagram showing a sixth embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 1, the voltage detection circuit is used to make the GND-output voltage constant, but the output transistor 6 is a P-channel MOS transistor. 1 is different from the circuit shown in FIG. 1 in that the threshold voltage of the P-channel MOS transistor is used for the voltage detection unit of the voltage detection circuit. The detection voltage can be freely set by adjusting the current of the constant current source 11.

  FIG. 7 is a block diagram showing a seventh embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 6, a voltage regulator circuit that uses a voltage detection circuit that uses the threshold voltage of a P-channel MOS transistor as a detection voltage so that the GND-output voltage is constant, and the output transistor is an N-channel type. It is composed of MOS transistors. A circuit for inverting logic, a constant current source 13 and a logic inverting transistor 53 are added to the voltage detection circuit. This circuit is suitable for a circuit that requires higher PSRR characteristics than the circuit shown in FIG.

  FIG. 8 is a block diagram showing an eighth embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 4, a circuit for detecting the difference between the output voltage and the target voltage and performing feedback control is configured by a voltage detection circuit so that the voltage between the input voltage and the output is constant. 4 is different from the circuit shown in FIG. 4 in that a threshold voltage of a P-channel MOS transistor is used for the voltage detection transistor 51 of the voltage detection circuit.

  FIG. 9 is a block diagram showing a ninth embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 8, a voltage regulator is configured such that a P-channel MOS transistor is used as the voltage detection transistor 51 of the voltage detection circuit and the threshold voltage is used as a detection voltage so that the input voltage-output voltage is constant. Circuit. A circuit for inverting logic, a constant current source 13 and a logic inverting transistor 53 are added to the voltage detection circuit. The output transistor 6 is a P-channel MOS transistor. This circuit is suitable for a circuit that requires higher PSRR characteristics than the circuit shown in FIG.

  FIG. 10 is a block diagram showing a tenth embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 9, a voltage detection circuit using a voltage detection circuit that uses the threshold voltage of a P-channel MOS transistor as a detection voltage so that the voltage between the input voltage and the output is constant. It is composed of channel type MOS transistors. Although it is suitable for a circuit that requires high PSRR characteristics as in FIG. 9, the area used is reduced by reducing the number of elements used in FIG. Suitable for semiconductor devices that prioritize reduction in area.

  FIG. 11 is a block diagram showing an eleventh embodiment of the voltage regulator of the present invention. In the voltage regulator circuit configured so that the GND-output voltage is constant, the output transistor 6 is configured by a P-channel MOS transistor. A voltage detection circuit that detects a difference from the target voltage and performs feedback control is configured by the operational amplifier 5. By setting the power supply for driving the operational amplifier 5 to the output voltage Vout, the output of the operational amplifier does not fluctuate due to fluctuations in the input power supply, and PSRR deterioration of the output Vout of the voltage regulator does not occur.

  Since a high gain can be easily obtained by using the operational amplifier 5, it is easy to reduce an error from the target voltage.

  If the reference voltage circuit 2 is formed between Vout and GND that is not affected by fluctuations in the input power supply, higher PSRR characteristics can be obtained. In such a circuit configuration, the startup circuit 9 needs to be added to the operational amplifier 5 because it may not start normally when the power is turned on.

  FIG. 12 is a block diagram showing a twelfth embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 11, the voltage regulator circuit is configured such that the GND-output voltage is constant using the operational amplifier 5, but the output transistor 6 is configured of an N-channel MOS transistor.

  There is no capacitive coupling due to the parasitic capacitance of the MOS transistor between the input power supply VDD and the output Vout, which is suitable for applications requiring high PSRR characteristics.

  FIG. 13 is a block diagram showing a thirteenth embodiment of the voltage regulator of the present invention. A circuit that detects a difference between the output voltage and the target voltage and performs feedback control is configured by the operational amplifier 5 so that the voltage between the input voltage and the output is constant.

  FIG. 14 is a block diagram showing a fourteenth embodiment of the voltage regulator of the present invention. Similar to the voltage regulator of FIG. 13, the voltage regulator circuit is configured such that the input voltage-output voltage is constant using an operational amplifier, but the output transistor 6 is configured by a P-channel MOS transistor.

  There is no capacitive coupling due to the parasitic capacitance of the MOS transistor between the input power supply VDD and the output Vout, which is suitable for applications requiring high PSRR characteristics.

1 is a block diagram illustrating a first embodiment of a voltage regulator according to the present invention. It is a block diagram which shows the 2nd Example of the voltage regulator of this invention. It is a block diagram which shows the 3rd Example of the voltage regulator of this invention. It is a block diagram which shows the 4th Example of the voltage regulator of this invention. It is a block diagram which shows the 5th Example of the voltage regulator of this invention. It is a block diagram which shows the 6th Example of the voltage regulator of this invention. It is a block diagram which shows the 7th Example of the voltage regulator of this invention. It is a block diagram which shows the 8th Example of the voltage regulator of this invention. It is a block diagram which shows the 9th Example of the voltage regulator of this invention. It is a block diagram which shows the 10th Example of the voltage regulator of this invention. It is a block diagram which shows the 11th Example of the voltage regulator of this invention. It is a block diagram which shows the 12th Example of the voltage regulator of this invention. It is a block diagram which shows the 13th Example of the voltage regulator of this invention. It is a block diagram which shows the 14th Example of the voltage regulator of this invention. It is a block diagram of the conventional voltage regulator. It is the equivalent circuit schematic of the output part of the conventional voltage regulator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply 2 Reference voltage circuit 3, 4 Output voltage dividing resistor 5 Operational amplifier 6 Output transistor 7 Output load 8 Phase compensation capacitor 9 Startup circuit 11, 12, 13 Detection voltage adjustment required constant current source 51 Voltage detection transistor 52 Control transistor 53 Logic Inverting transistors 81 and 82 Capacitors for phase compensation

Claims (6)

  A voltage regulator composed of a feedback circuit that feedback-controls an output voltage of an output terminal and an output transistor that is controlled by the feedback circuit and holds the output voltage constant, wherein the power supply of the feedback circuit is an output voltage .   The voltage regulator according to claim 1, wherein the feedback circuit is a voltage detection circuit including a constant current source and a transistor.   The voltage regulator according to claim 1, wherein the feedback circuit includes a reference voltage circuit and an operational amplifier.   The voltage regulator according to claim 3, wherein the voltage regulator is configured to generate the reference voltage circuit from the output voltage.   The voltage regulator circuit according to claim 3, wherein a startup circuit is added to the operational amplifier.   6. The voltage regulator according to claim 1, further comprising a phase compensation capacitive element provided in the feedback circuit, wherein a power source of the phase compensation capacitive element is an output voltage.

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