JP2008165686A - Variable regulator and power amplifier device using the variable regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable regulator, capable of ensuring a phase tolerance of an amplifier according to output power supply voltage or current without needing addition of phase compensation capacity. <P>SOLUTION: In the variable regulator adapted to detect output voltage Vout by resistors R1 and R2, and stabilize output voltage of a driver transistor 201 by an amplifier 202 so that the detected voltage follows input signal voltage Vin, a current source switching circuit 211 adjusts the output current of the amplifier 202 according to the level of the input signal voltage Vin detected by a level detection circuit 211. According to this, phase compensation of the regulator can be performed without adding a capacitor for phase compensation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power supply circuit that supplies power supply voltage and current to various electronic devices, and more particularly to a variable regulator that adjusts the power supply voltage and current according to an input signal voltage.

FIG. 8 shows a conventional variable regulator used for power supply.
In the P-channel MOSFET driver transistor Q1, the power supply voltage VDD is applied to the source, and the output voltage Vout is supplied from the drain to the load 800. The output voltage Vout is divided by the feedback resistors R1 and R2, and the connection point potential between the feedback resistors R1 and R2 is input as a feedback voltage to the non-inverting input terminal (+) of the amplifier A1. The input signal voltage Vin is applied to the inverting input terminal (−) of the amplifier A1, and the output of the amplifier A1 is connected to the gate of the driver transistor Q1.

  The amplifier A1 operates as an inverting amplifier with respect to the input signal voltage Vin. When the feedback voltage rises above the input signal voltage Vin, the gate voltage to the driver transistor Q1 is lowered, and when the feedback voltage falls below the input signal voltage Vin, the driver A1. Increase the gate voltage to transistor Q1. With this operation, the output voltage Vout is controlled so that the feedback voltage becomes equal to the input signal voltage Vin.

  That is, in the power supply circuit of FIG. 8, the input signal voltage Vin is converted to (1 + R1 / R2) times and output to the load 800. If the input signal voltage Vin is a constant reference voltage, a constant voltage is supplied to the load 800 as the output voltage Vout.

FIG. 9 shows another conventional example.
In the variable regulator of FIG. 9, the configuration of the driver transistor Q1, the feedback resistors R1 and R2, and the inverting amplifier A1 of the P-channel MOSFET is the same as that of the regulator of FIG. Reference numeral 901 denotes a reference voltage generation circuit that generates an input signal voltage Vin.

The difference is that a resistor R3 is provided at the connection point between the feedback resistor R1 and the feedback resistor R2, and one terminal of the resistor R3 is input as a feedback voltage to the non-inverting input terminal (+) of the amplifier A1. Further, a capacitor C1 is provided at the non-inverting input terminal (+), and one terminal of the capacitor C1 is connected to the output voltage Vout, thereby forming a phase compensation circuit of R3 + R1 // C1. Further, a current detection circuit 902 for detecting the output current of the output voltage Vout is provided, an N channel MOSFET is provided at both ends of the resistor R3, a current detection circuit 902 is provided, an N channel MOSFET Q2 is provided at both ends of the resistor R3, and the N channel MOSFET Q2 The gate is controlled by the output of the current detection circuit 902.
Japanese Patent Laid-Open No. 2002-297248 (FIG. 1)

  In the variable regulator described with reference to FIG. 8, when the variable range (high dynamic range) of the input signal voltage Vin is large, the negative feedback amplifier A1 oscillates with the magnitude of the output voltage Vout (output current Iout). There is a problem that it is easy (the phase margin is insufficient).

  In order to prevent such oscillation in the amplifier A1 having a large dynamic range (to ensure the phase margin), a variable regulator shown in FIG. 9 is known. More specifically, when the current flowing from the output voltage Vout to the load 800 increases due to the fluctuation of the load 800 and the current output from the driver transistor Q1 increases, the frequency at which the phase delay is caused by the driver transistor Q1 moves to the high frequency side. To do. In contrast, when the current flowing from the output voltage Vout to the load 800 decreases and the current output from the driver transistor Q1 decreases, the frequency at which the phase delay is caused by the driver transistor Q1 moves to the low frequency side. When the current detection circuit 902 determines that the value is equal to or greater than the predetermined value, the N-channel MOSFET Q2 is turned on to short-circuit the resistor R3, thereby reducing the time constant.

  By doing this, even if the frequency at which the phase delay is caused by the driver transistor Q1 moves to the high frequency side, the frequency at which the phase compensation is performed can be moved to the high frequency side by switching the time constant. The margin can be increased.

However, in order to prevent the oscillation of the negative feedback amplifier, the variable regulator shown in FIG. 9 requires a phase compensation capacitor, which increases the chip area.
The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a variable regulator that does not require a phase compensation capacitor and ensures the phase margin of an amplifier in accordance with the output power supply voltage and current. And

  According to a first aspect of the present invention, a variable regulator includes a driver transistor connected between a DC power supply voltage and an output to a load, and an output voltage applied to the load with respect to a level of an input signal voltage is predetermined. Voltage control means for adjusting the impedance of the driver transistor so as to have a voltage gain of, and current source switching means for switching the current of the output stage of the voltage control means in accordance with the input signal voltage or the current flowing through the driver transistor; It is provided with.

  A variable regulator according to a second aspect of the present invention is the variable regulator according to the first aspect, wherein the voltage control means includes a feedback resistor that detects the output voltage, a feedback voltage generated by the feedback resistor, and levels of the input signal voltage. An amplifier that is input and drives the driver transistor, the current source switching means detecting a level of the input signal voltage, and a current output from the amplifier according to the output of the level detection circuit And a current source switching circuit for switching the source.

  A variable regulator according to a third aspect of the present invention is the variable regulator according to the first aspect, wherein the voltage control means receives a feedback resistor for detecting the output voltage, a feedback voltage generated by the feedback resistor, and the input signal voltage. And an amplifier for driving the driver transistor, wherein the current source switching means detects a current flowing through the driver transistor, and outputs a current source of the amplifier according to the output of the current detection circuit. And a current source switching circuit for switching.

  A variable regulator according to a fourth aspect of the present invention is the variable regulator according to the second or third aspect, wherein the driver transistor is an N-channel MOSFET having a drain connected to the power supply side and a source connected to the load side, or It is an NPN transistor, and the amplifier is a non-inverting amplifier.

  According to a fifth aspect of the present invention, there is provided a power amplifying apparatus comprising the variable regulator according to any one of the first to fourth aspects, and a power amplifying unit to which power is supplied from the variable regulator. To do.

  As described above, according to the variable regulator of the present invention, the amplifier output is switched by switching the current of the amplifier output in accordance with the output current of the driver transistor or the input signal voltage level of the amplifier without newly providing a phase compensation circuit. By adjusting the resistance, the feedback rate of the amplifier is adjusted, and the phase margin deteriorated by the output current of the driver transistor can be improved.

  In addition, according to the power amplifying device of the present invention, the current at the amplifier output is reduced at low power, and the feedback factor is adjusted by increasing the resistance value of the amplifier output. Increase efficiency.

Embodiments of the present invention will be described below with reference to FIGS.
(Embodiment 1)
1 to 3 show a variable regulator according to a first embodiment of the present invention.

FIG. 1 shows the entire variable regulator. A voltage control unit 200, a driver transistor 201, and a current source switching unit 210 are provided.
The driver transistor 201 is a P-channel MOSFET, and the power supply voltage VDD is applied to the source, and the output voltage Vout is applied to the load 300 from the drain.

  The voltage control means 200 includes an amplifier 202 and feedback resistors R1 and R2. The feedback resistors R1 and R2 are provided so as to divide the output voltage Vout of the variable regulator. In the amplifier 202, the input signal voltage Vin is input to the inverting terminal (−), and the output of the amplifier 202 is connected to the gate of the driver transistor 201, which is a P-channel MOSFET, to control the driver transistor 201. The non-inverting terminal (+) of the amplifier 202 is connected to a connection point between feedback resistors R1 and R2 that determines the gain (hereinafter, the potential at this connection point is referred to as a feedback voltage).

  The current source switching unit 210 includes a level detection circuit 211 and a current source switching circuit 212. The level detection circuit 211 detects whether the voltage level input from the input signal voltage Vin exceeds a predetermined level. When the level detection circuit 211 exceeds a predetermined level, the current source switching circuit 212 receives a switching signal and adjusts the current value of the constant current output from the amplifier 202.

Next, an operation when the level detection circuit 211 exceeds a predetermined level will be described.
A state where the level detection circuit 211 exceeds a predetermined level is a state where the output voltage Vout is high. That is, since a high voltage is supplied to the load 300, the current output from the driver transistor 201 increases. When the current increases, the frequency at which the phase delay is caused by the driver transistor 201 moves to the high frequency side. Thus, in order to recover the phase delay and supply a stable signal to the output voltage Vout, it is necessary to reduce the time constant and shift the phase compensation to the high frequency side. When the level detection circuit 211 exceeds a predetermined level, the control signal reduces the gate resistance of the driver transistor 201 to lower the time constant, thereby increasing the output current of the amplifier 202 to lower the output resistance of the amplifier 202 and causing a phase delay. To provide a stable signal.

An operation when the level detection circuit 211 is equal to or less than a predetermined value will be described.
When the level detection circuit 211 is equal to or lower than the predetermined value, the output voltage Vout is in a low state, so that a low voltage is supplied to the load 300, the current output from the driver transistor 201 is reduced, and a small current state is obtained. As a result, phase advance is caused by the driver transistor 201, and the frequency shifts to the low frequency side. In order to recover the phase advance by increasing the time constant, the output current of the amplifier 202 is decreased to increase the output resistance of the amplifier 202, and the phase advance is recovered.

FIG. 2 shows an internal circuit of the amplifier 202.
Note that the switch means SWP and SWN operated by the switching signal S1 and the related parts correspond to the current switching circuit 213 in FIG.

  In general, a variable regulator outputs from a large current to a small current by the driver transistor 201. In particular, in order to avoid a decrease in the output voltage Vout due to the ON resistance of the driver transistor 201 at a large current, the driver transistor 201 A relatively large transistor size is required. As a matter of course, when the transistor size of the driver transistor 201 is increased, the characteristics contradict with the wide band due to the parasitic capacitance of the transistor. However, by reducing the output resistance of the amplifier 202 and reducing the resistance viewed from the gate side of the driver transistor 201, a wide band can be achieved.

  In the example shown in FIG. 2, in order to reduce the output resistance of the amplifier 202 when the output current of the driver transistor 201 is large, the mirror ratio of the output of the amplifier 202 is increased (constant current is increased) to lower the resistance. For example, when the output current of the driver transistor 201 is small, the mirror ratio of the transistors QP1 and QP2A, the transistor QN1 and the transistor QN2A is configured, and the level of the input signal voltage Vin exceeds a certain threshold in the level detection circuit 211 The switch means SWP and SWN are connected to each other by the switching signal S1, and the output resistance of the amplifier 202 is lowered by increasing the output current of the amplifier 202 by increasing the mirror ratio by QP1 and QP2A + QP2B and QN1 and QN2A + QN2B. That is, the loop ratio of the amplifier 202 is changed by changing the mirror ratio of the output transistor of the amplifier 202 to optimize the loop characteristics.

  Further, when the output current of the driver transistor 201 is small, the switch means SWP and SWN are turned off, the mirror ratio of the output transistor of the amplifier 202 is reduced, and the output current of the amplifier 202 is reduced. A variable regulator that switches when the driver transistor 201 has a small current, switches the loop gain between a large current and a small current, optimizes the feedback rate according to the magnitude of the regulator voltage (the magnitude of the output current), and supplies a stable output It can be provided. Further, by reducing the output current of the amplifier 202 when the driver transistor 201 has a small current, the current consumption can be reduced at the same time.

  Note that the switching is performed by setting several threshold voltages of the level detection circuit 211 according to the voltage level of the input signal voltage Vin, and changing the output current (mirror ratio) of the amplifier 202 according to the set several voltages. It is good also as a structure switched to n pieces.

FIG. 3 shows a specific circuit of the level detection circuit 211.
The input signal voltage Vin is applied to the base of one transistor Q11 of the NPN transistors Q11 and Q12 forming a differential pair, and the threshold voltage Vth is applied to the other base. When the input signal voltage Vin exceeds the threshold voltage Vth, the NPN transistor Q11 on the input signal voltage Vin side is turned on, and the PNP transistor Q13 is turned on to output the switching signal S1. The threshold voltage Vth is arbitrarily set to control the output of the switching signal S1. In addition, n NPN transistors that form a differential pair with the NPN transistor connected to the base of the input signal voltage Vin are provided, and n PNP transistors that output the switching signal S1 are provided to set the respective threshold voltages Vth + A. Thus, the mirror ratio may be switched to n.

(Embodiment 2)
4 and 5 show a variable regulator according to the second embodiment of the present invention.
In addition, the same code | symbol is attached | subjected to the thing of the same structure as the variable regulator shown in FIG. 1, and description is abbreviate | omitted.

  In the first embodiment, the current switching unit 210 operates in accordance with the voltage level of the input signal voltage Vin. However, the current switching unit 210 of the second embodiment includes a current detection circuit 213 that detects the output current of the driver transistor 201. The only difference from Embodiment 1 is that it operates according to the output.

  According to this configuration, a switching signal can be generated by the current detection circuit 213 according to the output current of the driver transistor 201, and the mirror ratio of the output transistor of the amplifier 202 can be controlled by the current switching circuit 212.

  Since the feedback ratio can be adjusted by switching the mirror ratio of the output transistor of the amplifier 202 depending on the output current value of the driver transistor 201, optimum adjustment (mirror ratio switching) can be performed depending on the load 300.

FIG. 5 shows a specific circuit of the current detection circuit 213.
The gate width of the driver transistor 201: W = A and the gate width of the N-channel MOS FST constituting the mirror: W = A / n. The threshold voltage is adjusted by setting n arbitrarily and the resistance value connected to the drain. To output a switching signal. Also, n driver MOSFETs 201 and n-channel MOSFETs constituting mirrors are provided, and the gate width is arbitrarily set to output n switching signals, and the mirror ratio of the output of the amplifier 202 is switched to n. It is good also as composition to do.

(Embodiment 3)
FIG. 6 shows a variable regulator according to the third embodiment of the present invention.
In addition, the same code | symbol is attached | subjected to the thing of the same structure as the variable regulator shown in FIG. 1, and description is abbreviate | omitted.

  The variable regulator of the third embodiment is different from the variable regulators of the first and second embodiments in that the driver transistor is an N-channel MOSFET and the input to the amplifier is reversed. In order to clarify these differences, a driver transistor 204 and an amplifier 203 are used. An NPN transistor may be used instead of the N-channel MOSFET.

  According to this configuration, the amplifier 203 operates as a non-inverting amplifier with respect to the input signal voltage Vin. When the feedback voltage rises above the input signal voltage Vin, Vgs to the driver transistor 204 is raised, and the feedback voltage falls below the input signal voltage Vin. Then, Vgs of the driver transistor 204 is lowered. With the above operation, the output voltage Vout is controlled so that the feedback voltage becomes equal to the input signal voltage Vin. That is, the variable regulator converts the input signal voltage Vin to (1 + R1 / R2) times and outputs it to the load 300.

  In the case of forming a transistor, in general, when the N-channel MOSFET has the same on-resistance as the P-channel MOSFET, the diffusion area can be reduced and the parasitic capacitance can be further reduced. Therefore, when the driver transistor is configured in the IC, the N-channel MOSFET can reduce the area of the IC if the characteristics are comparable.

  The operation for optimizing the feedback rate in the output current of the driver transistor is the same as that of the variable regulator in the first embodiment shown in FIG. 1, and the reduction of the current consumption at the time of the low output current and the optimization of the feedback rate are performed simultaneously. it can.

In the third embodiment, the variable regulator having the configuration of the first embodiment is used. However, the same can be applied to other embodiments.
(Embodiment 4)
FIG. 7 shows a power amplifying device using the variable regulator of the first embodiment.

Components having the same configuration as the variable regulator of the first embodiment shown in FIG.
The difference from the first embodiment is that a power amplifier 301 is provided instead of the load 300 that provides the output voltage Vout. The power amplifier 301 is supplied with power from the variable regulator, amplifies the high frequency input signal RFin, and outputs a high frequency output signal RFout. Since the output voltage Vout is applied as the power source of the power amplifier 301, the output power of the power amplifier 301 is controlled according to the level of the output voltage Vout.

  According to this configuration, the power amplifier 301 to which power is supplied from the output voltage Vout of the variable regulator can provide transmission power that stabilizes a wireless transmitter signal. Further, the power amplifier 301 at the time of a small output voltage (small transmission power) has a low current, and the power efficiency at the time of small transmission power can be improved.

  In the fourth embodiment, the variable regulator having the configuration of the first embodiment is used, but variable regulators of other embodiments can be used.

  The variable regulator of the present invention and the power amplifying device using the variable regulator are useful for supplying power to various electronic devices. The power amplifying device using the variable regulator is low as a power amplifier using a polar modulation method, for example. This is useful for current consumption systems.

Configuration diagram of variable regulator of embodiment 1 of the present invention Specific circuit diagram of switching of current source of amplifier output of same embodiment Specific circuit diagram of level detection of the embodiment Configuration diagram of variable regulator of embodiment 2 of the present invention Specific circuit diagram of current detection of the same embodiment Configuration diagram of variable regulator according to Embodiment 3 of the present invention Configuration diagram of a power amplifying device using the variable regulator of the present invention Circuit diagram of variable regulator of first conventional example Circuit diagram of second conventional variable regulator

Explanation of symbols

200 Voltage control means 201 Driver transistor (P-channel MOSFET)
202 amplifier 203 amplifier 204 driver transistor (N-channel MOSFET)
210 Current source switching means 211 Level detection circuit 212 Current source switching circuit 213 Current detection circuit 300 Load 301 Power amplifier VDD Power supply voltage Vin Input signal voltage Vout Output voltage R1, R2 Feedback resistance QP1, QP2A, QP2B PNP transistor SWP switch means QN1, QN2A, QN2B NPN transistor SWN switch means

Claims (5)

A driver transistor connected between the DC power supply voltage and the output to the load;
Voltage control means for adjusting the impedance of the driver transistor so that the output voltage applied to the load has a predetermined voltage gain with respect to the level of the input signal voltage;
A variable regulator comprising: a current source switching unit that switches a current of an output stage of the voltage control unit according to the input signal voltage or a current flowing through the driver transistor. The voltage control means includes
A feedback resistor for detecting the output voltage;
A feedback voltage generated by the feedback resistor and an amplifier that receives the input signal voltage and drives the driver transistor, and the current source switching means includes:
A level detection circuit for detecting a level of the input signal voltage;
The variable regulator according to claim 1, further comprising: a current source switching circuit that switches a current source of the output of the amplifier according to an output of the level detection circuit. The voltage control means includes
A feedback resistor for detecting the output voltage;
A feedback voltage generated by the feedback resistor and an amplifier that receives the input signal voltage and drives the driver transistor, and the current source switching means includes:
A current detection circuit for detecting a current flowing through the driver transistor;
The variable regulator according to claim 1, further comprising: a current source switching circuit that switches a current source of the amplifier output in accordance with an output of the current detection circuit. The driver transistor is
An N-channel MOSFET having a drain connected to the power supply side and a source connected to the load side, or an NPN transistor,
The variable regulator according to claim 2, wherein the amplifier is a non-inverting amplifier. The variable regulator according to any one of claims 1 to 4,
A power amplifying device comprising power amplifying means to which power is supplied from the variable regulator.

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