TWM487465U - Low-dropout voltage regulator - Google Patents

Description

Low dropout linear regulator

This new type relates to a low-dropout linear regulator, especially a low-dropout linear regulator with a wide range of output currents and a good phase margin (Phase Margin).

Traditionally, there are two common voltage conversion circuits: switching regulators and linear regulators. The linear regulators commonly used in buck applications are low dropout regulators (low drop). Out regulator, LDO regulator). The linear regulator has the ability to provide a stable output voltage. The low-dropout linear regulator is widely used because the output voltage can be very close to the input voltage, which saves the power consumption of the power transistor, so that the battery life can be maintained for a long time. Used in a variety of portable electronic products, such as Walkman, digital cameras, mobile phones, notebook computers, and more.

Please refer to FIG. 1 for a schematic diagram of a conventional low dropout regulator 100. The low-dropout voltage regulator 100 includes an error amplifier 110, a frequency compensation circuit 120, a transmission component 130, a voltage sensing circuit 140, and an output capacitor Cout. The load 150 is electrically connected to the transmission component 130. The working principle is mainly to detect the output voltage Vout by the voltage sensing circuit 140 and generate a feedback voltage Vfb, so that the error amplifier 110 is different according to the feedback voltage Vfb and the reference voltage Vref. The frequency compensation circuit 120 is controlled and the transmission element 120 is further controlled to produce a stable output voltage. The output capacitor Cout is used to temporarily provide a large amount of current required by the load when the load current Iload suddenly changes to improve the transient response of the output voltage.

The prior art architecture is a one-pass system that determines the amount of compensation by detecting the output voltage. When the output voltage is high, the output current must be reduced, which in turn reduces the output voltage. When the output voltage is low, the output current must be increased to increase the output voltage. Therefore, by detecting the output voltage, the amount of compensation, that is, the amount of compensation or adjustment of the output current, can be known.

In general, a good phase margin (Phase Margin) has been an important issue in the design of low-dropout linear regulators, which involves the stability of the return system. The stability of the system is determined by the phase margin parameter. In prior art systems, the phase margin was affected by the output current. If the current range is very wide, for example, it sometimes needs to operate at an output current of 100nA, and sometimes it needs to operate at an output current of 100mA. In this case, the phase margin is difficult to consider in two cases. At this time, the frequency compensation circuit 120 cannot be matched. Therefore, it is difficult to apply the output current of all cases with a single frequency compensation circuit 120, and frequency compensation is performed, so that a good phase margin cannot be generated.

In view of this, the present invention provides a low dropout linear regulator to overcome the problems or shortcomings encountered in the prior art, so that the low dropout linear regulator can be applied to a wide range of output currents with good phase margins.

A low dropout linear regulator according to an embodiment of the present invention includes: an error amplifier, a frequency compensation circuit, a transmission element, a voltage sensing circuit, and a current sensing circuit. The error amplifier is used to generate a voltage according to a reference voltage and a feedback voltage. a control signal; the voltage sensing circuit is configured to sense an output voltage to generate the feedback voltage; the current sensing circuit is configured to sense an output current, and is turned on or off according to the magnitude of the output current; the frequency compensation circuit And the error amplifier is configured to output a frequency compensation signal according to the control signal and the output current; the transmission component is coupled to the frequency compensation circuit and the current sensing circuit for compensating the signal according to the frequency, To generate the output voltage.

Low-dropout regulators are widely used in a variety of portable electronic products because of their low production cost, simple circuit and low noise, which provide stable output voltage. This creation determines the current output current range by means of current detection, thereby adjusting the resistance value of the frequency compensation circuit to determine the compensation amount. Through this creation, the low dropout linear regulator can be applied to a wide range of output currents with good phase margins.

The above description of the present invention and the following description of the embodiments are intended to demonstrate and explain the spirit and principles of the present invention, and to provide a further explanation of the scope of the patent application of the present invention.

100‧‧‧Low Dropout Regulator

110‧‧‧Error amplifier

120‧‧‧ frequency compensation circuit

130‧‧‧Transmission components

140‧‧‧ voltage sensing circuit

150‧‧‧load

Cload‧‧‧ output capacitor

Vout‧‧‧ output voltage

Iload‧‧‧ load current

Vref‧‧‧reference voltage

Vfb‧‧‧ feedback voltage

200‧‧‧Low Dropout Regulator

210‧‧‧Error amplifier

220‧‧‧ frequency compensation circuit

230‧‧‧Transmission components

240‧‧‧ voltage sensing circuit

250‧‧‧load

260‧‧‧ Current sensing circuit

211‧‧‧current source

212‧‧‧First transistor

213‧‧‧second transistor

214‧‧‧ Third transistor

215‧‧‧ Fourth transistor

221‧‧‧ fifth transistor

222‧‧‧ sixth transistor

223‧‧‧ seventh transistor

224‧‧‧First resistance

225‧‧‧second resistance

226‧‧‧ Capacitance

231‧‧‧ eighth transistor

241‧‧‧First voltage divider resistor

242‧‧‧Second voltage divider resistor

261‧‧‧Ninth transistor

262‧‧‧ Third resistor

263‧‧‧buffer

Figure 1 is a block diagram of a low voltage drop linear regulator of the prior art.

FIG. 2 is a circuit block diagram of the low dropout linear regulator disclosed in the present embodiment.

FIG. 3 is a detailed block diagram of the low dropout linear regulator disclosed in the present embodiment.

FIG. 4 is a circuit simulation diagram of the low dropout linear regulator disclosed in the present embodiment.

The detailed features and advantages of the present invention are described in detail below in the embodiments, which are sufficient for any skilled person to understand the technical content of the present invention and implement it. The objects and advantages associated with the present invention can be readily understood by those skilled in the art from the disclosure, the scope of the application, and the drawings. The following examples are intended to further illustrate the scope of this creation, but do not limit the scope of the creation in any way.

Certain terms are used throughout the description and claims to refer to particular elements. Those skilled in the art will appreciate that a hardware manufacturer may refer to the same component by a different noun. The scope of the present specification and the patent application do not use the difference in the name as the means for distinguishing the elements, but the difference in function of the elements as the criterion for distinguishing. As used in the specification and the scope of the patent application, "include" is an open term and should be interpreted as "including but not limited to". "Substantially" means that within the range of acceptable errors, those skilled in the art will be able to solve the technical problems within a certain error range, substantially achieving the technical effects. In addition, the term "coupled" is used herein to include any direct and indirect electrical coupling means. Therefore, if a first device is coupled to a second device, the first device can be directly electrically coupled to the second device, or electrically coupled indirectly through other devices or coupling means. Connected to the second device. The description of the specification is intended to be illustrative of the preferred embodiments of the invention. The scope of protection of this application is subject to the definition of the scope of the appended claims.

It is also to be understood that the terms "comprises", "comprising" or "comprising" or any other variations are intended to encompass a non-exclusive inclusion, such that a process, method, article, or Other elements not explicitly listed, or elements that are inherent to such a process, method, commodity, or system. An element that is defined by the phrase "comprising a ..." does not exclude the presence of additional equivalent elements in the process, method, item, or system including the element, without further limitation.

FIG. 2 is a circuit block diagram of the low dropout linear regulator disclosed in the present embodiment.

The low dropout regulator 200 includes an error amplifier 210, a frequency compensation circuit 220, a transmission component 230, a voltage sensing circuit 240, and a current sensing circuit 260. There is also an output capacitor Cout, and the load 250 is electrically connected to the transmission element 230.

In an embodiment, the error amplifier 210 is configured to generate a control signal according to a reference voltage Vref and a feedback voltage Vfb. The current sensing circuit 260 is configured to sense an output current and is turned on or off according to the magnitude of the output current; the voltage sensing circuit 240 is configured to sense an output voltage Vout to generate the feedback voltage Vfb; The frequency compensation circuit 220 is coupled to the error amplifier 210 for outputting a frequency compensation signal according to the control signal and the output current. The transmission component 230 is coupled to the frequency compensation circuit and the current sensing circuit. The signal is compensated according to the frequency to generate the output voltage Vout. Two signal paths are provided in the frequency compensation circuit 220, and are switched by a switch. When the output current is large, the switch is turned on in response and switched to the first path. When the output current is small, the switch is turned off and switched to the second path. Wherein the equivalent resistance of the first path is the equivalent resistance of the second path.

In a specific embodiment, the frequency compensation circuit 220 is provided with a switch, a first resistor and a second resistor, wherein the first resistor and the second resistor are connected in series to form a second path, and the switch is connected in series with the first resistor. Form a first path. The switch is turned on or off in response to the magnitude of the output current.

The output capacitor Cout is used to temporarily supply a large amount of current required by the load when the load current Iload suddenly changes to improve the transient response of the output voltage.

"Fig. 3" is the low-dropout linear regulator disclosed in the present embodiment. Detailed block diagram.

In an exemplary embodiment, the error amplifier 210 includes a current source 211, a first transistor 212, a second transistor 213, a third transistor 214, and a fourth transistor 215, wherein the first transistor The second transistor 213 is electrically connected to the current source 211, the second transistor 213 is electrically connected to the first transistor 212, and the fourth transistor 215 is electrically connected to the third transistor 214. Sexual connection.

In one embodiment, the first transistor 212 and the third transistor 214 are P-type MOS field effect transistors, and the second transistor 213 and the fourth transistor 215 are N-type MOS field-effect transistors. Therefore, the gate of the first transistor 212 receives the reference voltage Vref, the source of the first transistor 212 is electrically connected to the current source 211, and the drain of the first transistor 212 and the gate of the second transistor 213 are electrically connected. connection. The drain of the second transistor 213 is electrically connected to the gate, and the source of the second transistor 213 is electrically connected to the ground. The source of the third transistor 214 is electrically connected to the current source 211, and the gate of the third transistor 214 receives the feedback voltage, that is, electrically connected to the voltage sensing circuit 240, and the drain of the third transistor 214 is It is electrically connected to the drain of the fourth transistor 215. The gate of the fourth transistor 215 is electrically connected to the gate of the second transistor 213, and the source of the fourth transistor 215 is electrically connected to the ground.

In a typical embodiment, the frequency compensation circuit 220 includes a fifth transistor 221, a sixth transistor 222, a seventh transistor 223, a first resistor 224, a second resistor 225, and a capacitor 226. The fifth transistor 221 is electrically connected to the sixth transistor 222. The seventh transistor 223 is connected in series with the first resistor 224. The first resistor 224 is connected in series with the second resistor 225. Second resistor 225 in series

In one embodiment, the fifth transistor 221 is a P-type MOS field effect transistor, and the sixth transistor 222 and the seventh transistor 223 are N-type MOS field-effect transistors. Therefore, the fifth crystal The source of the body 221 is electrically connected to the power supply terminal, the gate of the fifth transistor 221 receives the output current of the current sensing circuit 260, and the drain of the fifth transistor 221 is electrically connected to the gate. The drain of the sixth transistor 222 is electrically connected to the drain of the fifth transistor 221, and the gate of the sixth transistor 222 is used as an output terminal for outputting a frequency compensation signal, that is, with the third transistor 214. The drain of the pole or the fourth transistor is electrically connected, and the source of the sixth transistor 222 is electrically connected to the power terminal. The gate of the seventh transistor 223 receives the output of the current sensing circuit 260. The drain of the seventh transistor 223 is electrically connected to the gate of the sixth transistor 222, and the drain of the seventh transistor 223 is electrically connected to the first end of the first resistor 224, and the source of the seventh transistor 223 The second end of the second resistor 225 is electrically connected to the first end of the second resistor 225, the second end of the second resistor 225 is electrically connected to the first end of the capacitor 226, and the second end of the capacitor 226 is connected to the ground. end.

In a typical embodiment, the transmission element 230 transmission element is an eighth transistor 231. In one embodiment, the eighth transistor 231 is a P-type MOS field effect transistor. Therefore, the source of the eighth transistor 231 is electrically connected to the power supply terminal, the gate of the eighth transistor 231 outputs a voltage, and the drain of the eighth transistor 231 is electrically connected to the voltage sensing circuit 240.

In a typical embodiment, voltage sensing circuit 240 includes a plurality of voltage dividing resistors. In one embodiment, the voltage sensing circuit 240 includes a first voltage dividing resistor 241 and a second voltage dividing resistor 242, which are connected in series with each other. The voltage sensing circuit 240 is configured to sense the output voltage Vout, and divide the output voltage Vout and output it to the error amplifier 210, that is, to the gate of the third transistor 214.

In a typical embodiment, current sensing circuit 260 includes a ninth transistor 261, a third resistor 262, and a buffer 263. The third resistor 262 is electrically connected to the ninth transistor 261, and the buffer 263 is electrically connected to the third resistor 262.

In one embodiment, the ninth transistor 261 is a P-type MOS field effect transistor. Therefore, the source of the ninth transistor 261 is electrically connected to the power supply terminal, the gate of the ninth transistor 261 is electrically connected to the gate terminal of the eighth transistor 231, and the drain of the ninth transistor 261 is respectively connected to the second The first end of the resistor 263 and the first end of the buffer 263 are electrically connected, the second end of the second resistor 263 is electrically connected to the ground end, and the second end of the buffer 263 is connected to the seventh end of the frequency compensation circuit 220. The gate of the crystal 223 is electrically connected.

In a typical embodiment, the aspect ratio of the ninth transistor 261 is proportional to the aspect ratio of the eighth transistor 231, and thus the current sensed by the ninth transistor 261 and the eighth transistor 231 The sensed current is proportional.

When the load current Iload is small, the ninth transistor 261 is not turned on, and the seventh transistor 223 is also in a non-conducting state. At this time, the first resistor 224 and the second resistor 225 form a series path to form a relatively large equivalent resistance. Therefore, in this case, it can be applied when the load current Iload is small.

When the load current Iload becomes large, the ninth transistor 261 is turned on, and the seventh transistor 223 is also turned on by the action of the buffer 263. At this time, the signal does not pass through the first resistor 224 but passes through. The path of the seventh transistor 223 and the second resistor 225 passes. At this time, there is only the second resistor 225, thus forming a relatively small equivalent resistance. Therefore, in this case, it can be applied when the load current Iload is large.

In one embodiment, a smaller load current Iload refers to a current of less than 100 mA, and a larger load current Iload refers to a current greater than 100 mA. Therefore, the ninth transistor 261 is turned on at a current of more than 100 mA.

In other words, the seventh transistor 223 and the first resistor in the frequency compensation circuit 220 224 and the second resistor 225 form two paths. When the seventh transistor 223 is not turned on, the signal passes through the first path formed by the first resistor 224 and the second resistor 225. When the seventh transistor 223 is turned on, the signal passes through the seventh transistor 223. A second path formed with the second resistor 225. Therefore, the seventh transistor 223 is turned on in response to the conduction of the ninth transistor 261, and is used as a path switching switch.

The current sensing circuit 260 detects the current output current and becomes conductive or non-conductive according to the state of the current output current. When the output current is large, the current sensing circuit 260 becomes conductive, that is, the ninth transistor 261 is turned on. When the output current is small, the current sensing circuit 260 becomes non-conductive, that is, the ninth transistor 261 is not turned on. Therefore, when the output current is large, the signal passes through the first path formed by the first resistor 224 and the second resistor 225, and the equivalent resistance is large. When the output current is small, the signal passes through the seventh power. The second path formed by the crystal 223 and the second resistor 225 has a smaller equivalent resistance. Therefore, by switching the conduction path through the seventh transistor 223, the magnitude of the equivalent resistance value can be changed, thereby making the frequency compensation circuit 220 applicable to different ranges of output currents.

The foregoing detailed circuit is exemplified. Of course, those skilled in the art can understand that there are other specific ways of the foregoing circuit. Therefore, the functions of the low-dropout linear regulator disclosed in FIG. 2 are all in this creation. range.

"Fig. 4" is a circuit simulation diagram of the low-dropout linear regulator disclosed in the present embodiment, which is performed using an analog software. As can be seen from the figure, when the output current is large, the Rzero value is small, That is, the signal will pass through the second path formed by the seventh transistor 223 and the second resistor 225, and the equivalent resistance is small. When the output current is small, the Rzero value is large, and the signal passes through the first path formed by the first resistor 224 and the second resistor 225, and the equivalent resistance is large. So can To use a wide range of output currents, regardless of high current or small current have good phase margins.

Low-dropout regulators are widely used in a variety of portable electronic products because of their low production cost, simple circuit and low noise, which provide stable output voltage. This creation determines the current output current range by means of current detection, thereby adjusting the resistance value of the frequency compensation circuit to determine the compensation amount. Through this creation, the low dropout linear regulator can be applied to a wide range of output currents with good phase margins.

Although the present invention has been disclosed above in the foregoing embodiments, it is not intended to limit the present invention. The changes and refinements that are made without departing from the spirit and scope of this creation are within the scope of patent protection of this creation. Please refer to the attached patent application scope for the scope of protection defined by this creation.

Cload‧‧‧ output capacitor

Vout‧‧‧ output voltage

Iload‧‧‧ load current

Vref‧‧‧reference voltage

Vfb‧‧‧ feedback voltage

200‧‧‧Low Dropout Regulator

210‧‧‧Error amplifier

220‧‧‧ frequency compensation circuit

230‧‧‧Transmission components

240‧‧‧ voltage sensing circuit

250‧‧‧load

260‧‧‧ Current sensing circuit

Claims (9)

A low-dropout linear regulator includes: an error amplifier for generating a control signal according to a reference voltage and a feedback voltage; and a voltage sensing circuit for sensing an output voltage to generate the feedback a current sensing circuit for sensing an output current and turning on or off according to the magnitude of the output current; a frequency compensation circuit coupled to the error amplifier for outputting the signal according to the control signal The magnitude of the current outputs a frequency compensation signal; and a transmission component coupled to the frequency compensation circuit and the current sensing circuit for compensating the signal according to the frequency to generate the output voltage. The low-dropout linear regulator of claim 1, further comprising an output capacitor electrically connected to the transmission component. The low-dropout linear regulator of claim 1, wherein the error amplifier comprises: a current source, a first transistor, a second transistor, a third transistor, and a fourth transistor, wherein The first transistor and the third transistor are electrically connected to the current source, and the second transistor is electrically connected to the first transistor, and the fourth transistor is electrically connected to the third transistor. The low-voltage drop linear regulator of claim 1, wherein the frequency compensation circuit comprises: a fifth transistor, a sixth transistor, a seventh transistor, a first resistor, a second resistor, and a capacitor, wherein the fifth transistor is electrically connected to the sixth transistor, the seventh transistor is connected in series with the first resistor, the first resistor is connected in series with the second resistor, and the capacitor is connected in series with the second resistor . A low-dropout linear regulator as claimed in claim 1, wherein the transmission element is a transistor. A low-dropout linear regulator as claimed in claim 5, wherein the electro-crystalline system is a P-type gold-oxygen half field effect transistor. The low dropout linear regulator of claim 1, wherein the voltage sensing circuit comprises a plurality of voltage dividing resistors. The low-dropout linear regulator of claim 7, wherein the voltage dividing resistor comprises a first voltage dividing resistor and a second voltage dividing resistor connected in series with the first voltage dividing resistor. The low-voltage drop linear regulator of claim 1, wherein the current sensing circuit comprises a ninth transistor, a third resistor, and a buffer, wherein the third resistor is electrically connected to the ninth transistor The buffer is electrically connected to the third resistor.