TW202336747A - Low-dropout regulator - Google Patents

Abstract

A low-dropout voltage regulator is provided. The error amplifier generates first and second control currents according to the output voltage and a reference voltage. The high-side driver is coupled between the error amplifier and a control terminal of the high-side switch, and provides a high-side driving current according to the first and second control currents. The high-side current sensor is coupled to the high-side switch and generates a high-side sense current. The high-side driving voltage adjustment circuit is coupled to the control terminal of the high-side switch and receives a high-side sense current to adjust a driving voltage of the high-side switch. A low-side switch is coupled between the output terminal and the ground terminal. The low-side driver is coupled between the error amplifier and the control terminal of the low-side switch, and provides a low-side driving current according to the first and second control currents.

Description

Low dropout voltage regulator

The present invention relates to a voltage adjustment circuit, and in particular to a low voltage drop voltage regulator.

Existing voltage regulators used in memories (such as Double Data Rate Synchronous Dynamic Random Access Memory (DDR SDRAM)) need to continuously provide stable large currents (such as 1~3 amps (A)) and output voltage to the memory, and can provide multiple different outputs (multi rail) through multiple adjustment circuits and low-dropout voltage regulators. Moreover, when the output needs to be stabilized quickly during load pumping, the voltage regulator must avoid excessive peak-to-peak changes in the output voltage.

Referring to Figure 1, Figure 1 is a schematic diagram of an existing low voltage dropout regulator. The low voltage dropout regulator 110 is coupled to the memory 120 and the output capacitor 121 . The low voltage dropout regulator 110 is used to provide the output voltage VTT to the memory 120 . The low voltage dropout regulator 110 includes a first-stage amplifier 111 , a second-stage amplifier 112 , a second-stage amplifier 115 , a resistor 113 , a resistor 116 , a capacitor 114 , a capacitor 117 , a transistor 118 and a transistor 119 . The low-dropout voltage regulator 110 can provide the supply current I_source or the drain current I_sink by turning on the transistor 118 or the transistor 119 and operating it in the saturation region (ie, the transistor switch is used as a variable resistor). output current and maintain the output voltage VTT. In steady state or load pumping, the transistor 119 operates in a state providing high impedance, and the transistor 118 conducts in a saturation region state according to the output current requirement to continuously provide the supply current I_source. When the load is unloaded or transferred to light load, the transistor 118 operates in a state providing high impedance, and the transistor 119 conducts in a saturation region state according to the output current requirement to enhance (extract) the bleed current I_sink. When the load changes, the output voltage will oscillate and produce large peak-to-peak. To quickly return the output voltage to a stable value, the solutions adopted in the existing technology are to generate a larger supply current I_source or a drain current I_sink, or to use a larger output capacitor 121, or both methods in parallel.

However, the above method of generating a larger supply current I_source or a leakage current I_sink requires the use of at least two stages of amplifiers as shown in Figure 1, which have a larger gain, resulting in changes in the output voltage due to Voltage overshoot (overshoot) or voltage undershoot (undershoot) causes the output voltage to produce a larger peak (peak) or larger voltage drop (drop) oscillation. Moreover, larger gains require larger compensation capacitors 114 and 117 . Using a larger output capacitor 121 will lead to an increase in circuit area, which is not conducive to reduction in manufacturing cost and reduction in circuit size.

In view of this, the low voltage drop voltage regulator of the present invention can achieve effective voltage stabilization without using a secondary amplifier and/or a large capacitor, and the compensation capacitance of the high-side switch and the low-side switch can also be reduced.

According to an embodiment of the present invention, the low-dropout voltage regulator of the present invention includes an error amplifier, a high-side switch, a high-side driver, a high-side current sensor, a high-side drive voltage adjustment circuit, a low-side switch, and a low-side driver. The error amplifier is coupled to the output terminal and generates a first control current and a second control current according to the output voltage and the reference voltage. The high-side switch is coupled between the input voltage source and the output terminal. The high-side driver is coupled between the error amplifier and the control terminal of the high-side switch, and provides a high-side driving current according to the first control current and the second control current. The high-side current sensor is coupled to the high-side switch and generates a high-side sensing current. The high-side driving voltage adjustment circuit is coupled to the control terminal of the high-side switch and receives the high-side sensing current to adjust the driving voltage of the high-side switch. The low-side switch is coupled between the output terminal and the ground terminal. The low-side driver is coupled between the error amplifier and the control terminal of the low-side switch, and provides a low-side driving current according to the first control current and the second control current.

In one embodiment, the low-dropout voltage regulator further includes a low-side current sensor and a low-side driving voltage adjustment circuit. The low-side current sensor is coupled to the low-side switch and generates a low-side sensing current. The low-side driving voltage adjustment circuit is coupled to the control terminal of the low-side switch and receives the low-side sensing current to adjust the driving voltage of the low-side switch.

In one embodiment, the error amplifier is further coupled to the high-side current sensor and the low-side current sensor, and adjusts the first control current and the second control current according to the high-side sensing current and the low-side sensing current.

In one embodiment, the magnitude relationship between the first control current and the second control current determines the flow direction of the high-side driving current and the low-side driving current.

In one embodiment, the high-side driver includes a first current mirror, a second current mirror, a third current mirror, a fourth current mirror and a high-side output terminal. The first current mirror is coupled to the error amplifier and receives the first control current. The second current mirror is coupled to the error amplifier and receives the second control current. The third current mirror includes the first transistor. The control terminal of the first transistor is coupled to the first current mirror, and the first terminal of the first transistor is coupled to the operating voltage. The fourth current mirror includes a second transistor. The second transistor is coupled between the first current mirror and the third current mirror, and the control terminal of the second transistor is coupled to the second current mirror. The second transistor turns on or off the path between the first current mirror and the third current mirror according to the current difference between the first control current and the second control current. The high-side output terminal is coupled to the second terminal of the first transistor in the second current mirror and the third current mirror.

In one embodiment, the low-side driver includes fifth, sixth, seventh and eighth current mirrors and a low-side output terminal. The fifth current mirror is coupled to the error amplifier and receives the second control current. The sixth current mirror is coupled to the error amplifier and receives the first control current. The seventh current mirror includes a third transistor. The control terminal of the third transistor is coupled to the fifth current mirror, and the first terminal of the third transistor is coupled to the operating voltage. The eighth current mirror includes a fourth transistor. The fourth transistor is coupled between the fifth current mirror and the seventh current mirror, and the control terminal of the fourth transistor is coupled to the sixth current mirror. The fourth transistor turns on or off the path between the fifth current mirror and the seventh current mirror according to the current difference between the first control current and the second control current. The low-side output terminal is coupled to the second terminal of the third transistor in the sixth current mirror and the seventh current mirror.

Based on the above, the low dropout voltage regulator of the present invention can effectively sense the load change at the output end through the error amplifier, the high-side current sensor and the low-side current sensor to dynamically adjust the output voltage to achieve effective stabilization. pressure effect.

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, embodiments are given below and described in detail with reference to the accompanying drawings.

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numbers are used in the drawings and description to refer to the same or similar parts.

FIG. 2 is a schematic diagram of a low voltage drop voltage regulator according to an embodiment of the present invention. Referring to Figure 2, a low-dropout regulator (LDO) 200 includes an error amplifier (error amplifier) 210, a high-side driver 220, a low-side driver 230, a high-side current sensor 240, and a high-side driving voltage adjustment. Circuit 250, compensation capacitor 251, low-side current sensor 260, low-side driving voltage adjustment circuit 270, compensation capacitor 271, high-side switch 280 and low-side switch 290. In this embodiment, the high-side switch 280 and the low-side switch 290 may be N-type Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), but are not limited thereto. The output terminal of the low voltage dropout regulator 200 is coupled to the output capacitor 301 and the memory 300 as a load. The memory 300 is, for example, a Double Data Rate Synchronous Dynamic Random Access Memory (DDR SDRAM), but is not limited thereto. In this embodiment, the low voltage dropout regulator 200 may be disposed in a power supply for providing power to the memory 300 and provide the output voltage VTT to the memory 300 .

The first input terminal of the error amplifier 210 is coupled to the reference voltage VREF, and the second input terminal is coupled to the output terminal of the low-dropout voltage regulator 200 to receive the output voltage VTT. The power terminal of the error amplifier 210 can also be coupled to the high-side current sensor 240 and the low-side current sensor 260 to receive the feedback currents I_SU1 and I_SD1. The first output terminal and the second output terminal of the error amplifier 210 are coupled to the first input terminal and the second input terminal of the high-side driver 220, and are also coupled to the first input terminal and the second input terminal of the low-side driver 230, so as to The first control current I_VTT and the second control current I_ref are provided to the high-side driver 220 and the low-side driver 230 .

The output terminal of the high-side driver 220 is coupled to the control terminal of the high-side switch 280 to provide the high-side driving current I_d1 (I_d1=I_VTT-I_ref) to the control terminal of the high-side switch 280 . The compensation capacitor 251 is coupled to the control terminal of the high-side switch 280 to stabilize the driving current I_d1. The high-side driving voltage adjustment circuit 250 is coupled to the high-side current sensor 240 and coupled to the control end of the high-side switch 280 through the compensation capacitor 251 to receive the high-side sensing current I_SU2 to adjust the driving voltage V_gHS of the high-side switch 280 . The output terminal of the low-side driver 230 is coupled to the control terminal of the low-side switch 290 to provide the low-side driving current I_d2 (I_d2=I_ref-I_VTT) to the control terminal of the low-side switch 290 . The compensation capacitor 271 is coupled to the control terminal of the low-side switch 290 to stabilize the driving current I_d2. The low-side driving voltage adjustment circuit 270 is coupled to the low-side current sensor 260 and coupled to the control terminal of the low-side switch 290 through the compensation capacitor 271 to receive the low-side sensing current I_SD2 to adjust the driving voltage V_gLS of the low-side switch 290 . The high-side driving voltage adjustment circuit 250 and the low-side driving voltage adjustment circuit 270 may respectively be a variable resistor or a variable resistance circuit including a current mirror.

The first terminal of the high-side switch 280 is coupled to the input voltage VIN, and the second terminal of the high-side switch 280 is coupled to the output terminal of the low-dropout voltage regulator 200 and the first terminal of the low-side switch 290 . The first terminal of the low-side switch 290 is coupled to the output terminal of the low-dropout regulator 200 , and the second terminal of the low-side switch 290 is coupled to the ground voltage.

In this embodiment, the error amplifier 210 is a transconductance amplifier for receiving an input voltage and outputting a current. The error amplifier 210 can generate the first control current I_VTT and the second control current I_ref according to the output voltage VTT voltage and the reference voltage VREF and transmit them to the high-side driver 220 and the low-side driver 230 at the same time to utilize the first control current I_VTT and the second control current I_VTT. The magnitude relationship (current difference) of the current I_ref is used to control the on/off of the high-side switch 280 and the low-side switch 290 .

In this embodiment, the high-side current sensor 240 and the low-side current sensor 260 are respectively coupled to the high-side switch 280 and the low-side switch 290 to respectively provide the first feedback current I_SU1 and the second feedback current I_SD1 to the error The amplifier 210 adjusts the current magnitudes of the first control current I_VTT and the second control current I_ref, and further determines the high-side driving current I_d1 (I_d1=I_VTT-I_ref) to turn on the high-side switch 280 and the low-side turning on the low-side switch 290 Driving current I_d2 (I_d2=I_ref-I_VTT).

In this embodiment, the high-side driving voltage adjustment circuit 250 and the low-side driving voltage adjustment circuit 270 respectively receive the high-side sensing current I_SU2 and the low-side sensing current I_SD2 to adjust the high-side driving voltage adjustment circuit 250 and the low-side sensing current I_SD2 respectively. The variable resistor in the driving voltage adjustment circuit 270 changes the driving voltages V_gHS and V_gLS of the high-side switch 280 and the low-side switch 290 when they are turned on. As the driving voltages V_gHS and V_gLS of the high-side switch 280 and the low-side switch 290 are adjusted when they are turned on, the on-resistances (R_onHS and R_onLS) of the high-side switch 280 and the low-side switch 290 will also change accordingly. Therefore, the current magnitudes of the supply current I_source and the drain current I_sink respectively provided by the high-side switch 280 and the low-side switch 290 are adjusted accordingly, thereby suppressing the ringing effect problem when the output voltage VTT changes.

FIG. 3 is a schematic diagram of changes in voltage signal, current signal and resistance according to an embodiment of the present invention. Referring to FIG. 2 and FIG. 3 , FIG. 3 illustrates an operating example embodiment of the low voltage dropout regulator 200 of FIG. 2 . The unit of voltage on the vertical axis in Figure 3 may be millivolts (mV), the unit of current may be microamperes (uA), the unit of resistance may be ohms (ohm), and the unit of time may be milliseconds (ms). Before time t1, when the load condition of the memory 300 is light load, the driving voltages V_gHS and V_gLS are maintained at constant values through the first control current I_VTT and the second control current I_ref, so that the high-side switch 280 is turned on and the low-side switch 280 is turned on. Switch 290 is off. The on-resistance R_onLS of the low-side switch 290 is maintained in the high-resistance state, and the on-resistance R_onHS of the high-side switch 280 is maintained in the low-resistance state. The supply current I_source is a fixed low current value, and the bleed current I_sink is zero current, thereby providing an output current. The high-side sensing current I_SU2 is a fixed low current value, and the low-side sensing current I_SD2 is zero current. In this way, the low voltage dropout regulator 200 can stably provide output current to the memory 300 .

At time t1, the memory 300 draws current, and the output voltage VTT provided by the low-dropout voltage regulator 200 begins to decrease, causing the error between the output voltage VTT and the reference voltage VREF to become larger. In this regard, an increase in the current value of the first control current I_VTT will cause a corresponding increase in the driving voltage V_gHS, and a decrease in the on-resistance R_onHS of the high-side switch 280 will cause an increase in the current (supply current I_source) flowing through the high-side switch 280 . In this way, the first feedback current I_SU1 and the high-side sensing current I_SU2 will increase, and the driving voltage V_gHS will be compensated through feedback, so that the ringing effect of the output voltage VTT will not be too large.

At time t2, since the voltage value of the output voltage VTT begins to rise, the voltage difference between the output voltage VTT and the reference voltage VREF gradually decreases, causing the current difference between the first control current I_VTT and the second control current I_ref to become Small. At the same time, the current value of the first control current I_VTT decreases, causing the voltage value of the driving voltage V_gHS to decrease. As a result, the on-resistance R_onHS of the high-side switch 280 is slightly increased, which reduces the current flowing through the high-side switch 280 , causing the current value of the high-side sensing current I_SU2 to slightly decrease between time t2 and time t3, and V_gHS With the reduction, the ringing effect of the output voltage VTT will not be too large.

At time t3, due to the load pumping relationship, the output voltage VTT in the load pumping state is lower than the output voltage VTT in the light load state, and the system enters a steady state. At time t4, when the load condition of the memory 300 changes to a light load state, the output voltage VTT rises because the output current is still in a heavy load state. In this regard, the current value of the first control current I_VTT affected by this will start to decrease and the voltage value of the driving voltage V_gHS will start to decrease, causing the current value of the high-side sensing current I_SU2 to start between time t4 and time t5 decline. At time t5, when the reference voltage VREF is less than or equal to the output voltage VTT, the first control current I_VTT will be less than the second control current I_ref. As a result, the high-side switch 280 will be turned off, and the low-side switch 290 will be turned on, so that the current value of the drain current I_sink is generated between time t6 and time t7 to drain the excess output current.

At time t6, since the voltage value of the output voltage VTT begins to decrease, the voltage difference between the output voltage VTT and the reference voltage VREF gradually decreases. At the same time, the current value of the first control current I_VTT decreases, and the current value of the second control current I_REF decreases. The bleed current I_sink continues to bleed excess output current, and the supply current I_source continues to decrease. At time t7, the reference voltage VREF is greater than or equal to the output voltage VTT, and the first control current I_VTT is greater than or equal to the second control current I_ref, so that the current supply state of the low-dropout regulator 200 returns to the same as time t1. At time t8, the driving voltage V_Ghs and the on-resistance R_onHS of the high-side switch 280 are adjusted to a balanced state, and the system returns to a steady state.

4A to 4C are circuit schematic diagrams of a low voltage drop regulator according to an embodiment of the present invention. Referring to FIGS. 4A to 4C , the low voltage dropout regulator 400 of FIGS. 4A to 4C can be a detailed circuit example of the low voltage dropout regulator 200 of the embodiment of FIG. 2 . The low voltage dropout regulator 400 includes transistors 403~404, a resistor 407, a capacitor 408, an output terminal 409, an error amplifier 410, a high-side driver 420, a low-side driver 430, a high-side current sensor 440, and a high-side driving voltage adjustment. circuit 450, compensation capacitors 451, 471, low-side current sensor 460 and low-side driving voltage adjustment circuit 470.

In this embodiment, the transistors 403 to 406 may be, for example, N-type MOSFETs, but are not limited thereto. The first terminal of the transistor 403 receives the input voltage VIN, the control terminal is coupled to the high-side output terminal 428 of the high-side driver 420, and is coupled to the high-side driving voltage adjustment circuit 450 through the compensation capacitor 451. The second terminal of the transistor 403 is coupled to the output terminal 409 of the low-voltage dropout regulator 400 , the control terminal is coupled to the low-side output terminal 438 of the low-side driver 430 , and the low-side driving voltage adjustment circuit 470 is coupled to the compensation capacitor 471 . The second terminal of the transistor 404 is coupled to the ground voltage. The transistors 405 and 406 are respectively coupled with the common gate and source of the transistors 403 and 404 to serve as current sensing components to respectively generate the high-side current sensing signal SENSU and the low-side current sensing signal SENSD. One end of the resistor 407 is coupled to the output terminal 409 of the low voltage dropout regulator 400, and the other end of the resistor 407 is coupled to the ground voltage. One end of the capacitor 408 is coupled to the output terminal 409 of the low voltage dropout regulator 400, and the other end of the capacitor 408 is coupled to the ground voltage.

The error amplifier 410 includes transistors 411 and 412 and a current source 413 . The transistors 411 and 412 may be, for example, P-type MOSFETs. The control terminal of the transistor 411 is coupled to the output terminal 409 of the low voltage dropout regulator 400 . The control terminals of the transistors 411 and 412 respectively receive the output voltage VTT and the reference voltage VREF. The first ends of the transistors 411 and 412 are coupled to the current source 413 and can also receive the first feedback current I_SU1 and the second feedback current I_SD1 provided by the high-side current sensor 440 and the low-side current sensor 460 . The second terminals of the transistors 411 and 412 respectively provide the first control current I_VTT and the second control current I_ref.

The high-side driver 420 includes current mirrors CM1 to CM4 and a high-side output terminal 428 . The high-side output terminal 428 is coupled to CM2 and CM3 to provide the high-side driving current I_d1 according to the first control current I_VTT and the second control current I_ref. Current mirror CM1 includes transistors 401, 425. The first terminal of the transistor 401 is coupled to the error amplifier 410 to receive the first control current I_VTT, and the first terminal of the transistor 425 provides a replicated first control current I_VTT. The first terminal of the transistor 401 is coupled to the control terminal through the node VNU. Current mirror CM2 includes transistors 402, 426, 427. The first terminal of the transistor 402 is coupled to the error amplifier 410 to receive the second control current I_ref, and the first terminals of the transistors 426 and 427 respectively provide replicated second control currents I_ref. The first terminal of the transistor 402 is coupled to the control terminal through the node VDU.

Current mirror CM3 includes transistors 421 and 422 . The control terminal of the transistor 421 is coupled to the control terminal of the transistor 422 and the first terminal of the transistor 425 through the node VFASTU. The first terminals of the transistors 421 and 422 are coupled to the operating voltage VDD. The second terminal of the transistor 421 is coupled to the current mirror CM4. The second terminal of the transistor 422 is coupled to the high-side output terminal 428 and the first terminal of the transistor 427 of the current mirror CM2.

Current mirror CM4 includes transistors 423 and 424 . The control terminal of the transistor 423 is coupled to the control terminal and the second terminal of the transistor 424 through the node VPU. The first terminal of the transistor 423 is coupled to the second terminal of the transistor 421 of the current mirror CM3. The second terminal of the transistor 423 is coupled to the transistor 425 of the current mirror CM1. The first terminal of the transistor 424 is coupled to the operating voltage VDD. The second terminal of the transistor 424 is coupled to the first terminal of the transistor 426 of the current mirror CM2.

Since the voltage of the node VPU is determined by the current difference between the first control current I_VTT copied by the current mirror CM1 and the second control current I_ref copied by the current mirror CM2, the transistor 423 can be controlled to turn on or off the current mirror CM1 accordingly. path to current mirror CM3. When the first control current I_VTT is greater than the second control current I_ref, causing the control terminal voltage of the transistor 423 to be less than the turn-on voltage of the transistor, the transistor 423 is turned off, and the pull-down current copied by the current mirror CM1 passes through the node VFASTU to push the transistor The control terminal voltage of 422 is pulled down to completely turn on the transistor 422, so that the voltage of the high-side output terminal 428 is equal to the operating voltage VDD, thereby generating a large high-side driving current I_d1 to quickly turn on the transistor 403.

The transistors 401 to 402 and 425 to 427 can be, for example, N-type MOSFETs, and the transistors 421 to 424 can be, for example, P-type MOSFETs, but the invention is not limited thereto.

The low-side driver 430 includes current mirrors CM5 ~ CM8 and a low-side output terminal 438 . The low-side output terminal 438 is coupled to CM6 and CM7 to provide the low-side driving current I_d2 according to the first control current I_VTT and the second control current I_ref. Current mirror CM5 includes transistors 402, 435. The first terminal of the transistor 402 is coupled to the error amplifier 410 to receive the second control current I_ref, and the first terminal of the transistor 435 provides a replicated second control current I_ref. Current mirror CM6 includes transistors 401, 436, 437. The first terminal of the transistor 401 is coupled to the error amplifier 410 to receive the first control current I_VTT, and the first terminals of the transistors 436 and 437 respectively provide replicated first control currents I_VTT.

Current mirror CM7 includes transistors 431 and 432 . The control terminal of the transistor 431 is coupled to the control terminal of the transistor 432 and the first terminal of the transistor 435 through the node VFASTD. The first terminals of the transistors 431 and 432 are coupled to the operating voltage VDD. The second terminal of the transistor 431 is coupled to the current mirror CM8. The second terminal of the transistor 432 is coupled to the low-side output terminal 438 and the first terminal of the transistor 437 of the current mirror CM6.

Current mirror CM8 includes transistors 433 and 434 . The control terminal of the transistor 433 is coupled to the control terminal and the second terminal of the transistor 434 through the node VPD. The second terminal of the transistor 433 is coupled to the transistor 435 of the current mirror CM5. The first terminal of the transistor 434 is coupled to the operating voltage VDD. The second terminal of the transistor 434 is coupled to the first terminal of the transistor 436 of the current mirror CM6.

Since the voltage of voltage VPD is determined by the current difference between the first control current I_VTT copied by current mirror CM6 and the second control current I_ref copied by current mirror CM5, the transistor 434 can be controlled to turn on or off the current mirror CM6 accordingly. Path to current mirror CM7. When the second control current I_ref is greater than the first control current I_VTT, causing the control terminal voltage of the transistor 433 to be less than the turn-on voltage of the transistor, the transistor 433 is turned off, and the pull-down current copied by the current mirror CM5 passes through the node VFASTD and turns the transistor The control terminal voltage of 432 is pulled down to completely turn on the transistor 432, so that the voltage of the low-side output terminal 438 is equal to the operating voltage VDD, thereby generating a large low-side driving current I_d2 to quickly turn on the transistor 404.

The transistors 401 to 402 and 435 to 437 can be, for example, N-type MOSFETs, and the transistors 431 to 434 can be, for example, P-type MOSFETs, but the invention is not limited thereto.

In this embodiment, the high-side current sensor 440 and the low-side current sensor 460 may be a combination of transistors 405 and 406 combined with a current mirror structure, but the invention is not limited thereto. The high-side current sensor 440 obtains the high-side sensing signal SENSU related to the supply current I_source flowing through the transistor 403 from the transistor 405 . The first feedback current I_SU1 and the high-side sensing current I_SU2 are output to the error amplifier 410 and the high-side driving voltage adjustment circuit 450 through the second terminals of the transistors 445 and 446 respectively. The low-side current sensor 460 obtains the low-side sensing signal SENSD from the transistor 406 related to the bleed current I_sink flowing through the transistor 404 . Then, the second feedback current I_SD1 is output to the error amplifier 410 through the second terminal coupling of the transistors 461 and 462, and the low-side sensing current I_SD2 is output to the low-side driving voltage adjustment circuit 470.

In this embodiment, the high-side driving voltage adjustment circuit 450 includes transistors 452, 453 and a resistor 454. The first terminal of the transistor 452 receives the high-side sensing current I_SU2 and is coupled to the control terminals of the transistors 452 and 453, so that the on-resistance of the transistor 453 changes according to the high-side sensing current I_SU2. The second terminal of the transistor 452 is coupled to the ground voltage. The transistor 453 and the resistor 454 are coupled in parallel between one end of the compensation capacitor 451 and the ground voltage.

In this embodiment, the low-side driving voltage adjustment circuit 470 includes transistors 472, 473 and a resistor 474. The first terminal of the transistor 472 receives the low-side sensing current I_SD2, and is coupled to the control terminals of the transistors 472 and 473, so that the on-resistance of the transistor 473 changes according to the low-side sensing current I_SD2. The second terminal of transistor 472 is coupled to the ground voltage. The transistor 473 and the resistor 474 are coupled in parallel between one end of the compensation capacitor 471 and the ground voltage.

FIG. 5 is a schematic diagram of changes in voltage signals and current signals according to an embodiment of the present invention. Referring to FIG. 4A to FIG. 4C and FIG. 5 , the timing of this embodiment is corresponding to the operation example embodiment of FIG. 3 , so the waveforms of the output voltage VTT, the driving voltages V_gHS, V_gLS, the first control current I_VTT and the second control current I_ref The changes are the same as in Figure 3. The unit of voltage on the vertical axis in FIG. 5 may be millivolts (mV), the unit of current may be microamperes (uA), and the unit of time may be milliseconds (ms).

At time t1, the external load draws current from the output terminal, causing the output voltage VTT to drop, and the voltage VPU to drop accordingly. Between time t1 and time t2, voltage VPU is lower than voltage VFASTU, and current mirror CM4 is turned off. Voltage VFASTU turns transistor 422 fully on to produce a large supply current I_source. At time t2, the voltage VPU is higher than the voltage VFASTU, and the current mirror CM4 is turned on, causing the high-side driver 420 to control the transistor 422 to provide the supply current I_sink. Between time t3 and time t4, the external load draws steadily.

At time t4, the external load is removed, causing the output voltage VTT to rise, and the voltage VFASTD to rise accordingly. Between time t5 and time t6, the voltage VPD is lower than the voltage VFASTD, and the current mirror CM8 is turned off. Voltage VFASTD turns transistor 432 fully on to produce a large bleed current Isink. Between time t6 and time t7, the voltage VPD is higher than the voltage VFASTD, and the current mirror CM8 is turned on, causing the low-side driver 430 to control the transistor 432 to provide the leakage current Isink.

Before time t5 and after time t7, the first control current I_VTT is greater than the second control current I_ref. Since the result of subtracting the first control current I_VTT from the second control current I_ref is greater than 0, the voltage VPU is pulled up by the positive current. In high-side driver 420, current mirror CM4 is turned on. The first control current I_VTT is output to the high-side output terminal 428 of the high-side driver 420 through current mirrors CM1 and CM3 through current replication. The second control current I_ref is output to the high-side output terminal 428 of the high-side driver 420 through the current mirror CM2 through current replication. Since the result of subtracting the first control current I_VTT from the second control current I_ref is greater than 0, the driving current output by the high-side driver 420 is greater than 0, so the transistor 403 is operated in the operating saturation region. Since the result of subtracting the second control current I_ref from the first control current I_VTT is less than 0, the voltage VPD is pulled down by the negative current, and the voltage VFASTD is pulled up. In low-side driver 430, current mirrors CM7, CM8 are turned off. The first control current I_VTT is output to the low-side output terminal 438 of the low-side driver 430 through the current mirror CM6 through current replication. Since the first control current I_VTT is a pull-down current, the driving current output by the low-side driver 430 is less than 0, so the transistor 404 is turned off.

At time t7, the first control current I_VTT is greater than or equal to the second control current I_ref, so that the current supply state returns to the state between time t1 and time t5.

In summary, the low-dropout voltage regulator of the present invention can sense load changes at the output end through an error amplifier, a high-side current sensor and a low-side current sensor, and can be used with a high-side current sensor and a low-side current sensor. The side current sensor 260 is used to dynamically adjust the conduction state of the high-side switch 280 and the low-side switch 290 to achieve an effective voltage stabilization effect.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention. Scope.

111: First stage amplifier 112, 115: Second stage amplifier 113, 116, 407, 454, 474: Resistor 114, 117, 408: Capacitor 118, 119, 401~406, 411~412, 421~427, 431~437, 441~446, 452, 453, 461~466, 472, 473: Transistor 121:Output capacitor 200, 110, 400: Low dropout voltage regulator 210, 410: Error amplifier 220, 420: High-side driver 230, 430: Low-side driver 240, 440: High-side current sensor 250, 450: High-side drive voltage adjustment circuit 251, 271, 451, 471: Compensation capacitor 260, 460: Low-side current sensor 270, 470: Low-side drive voltage adjustment circuit 280: High side switch 290: Low side switch 300, 120: memory 301: Output capacitor 409: Output terminal 413, 447, 448, 467, 468: current source 428: High side output terminal 438: Low side output terminal CM1~CM8: current mirror VREF: reference voltage I_VTT: first control current I_ref: second control current I_d1: high-side drive current I_d2: low-side drive current I_SU2: high side sensing current I_SD2: low-side sensing current V_gHS, V_gLD: driving voltage I_SU1: first feedback current I_SD1: second feedback current I_source: supply current I_sink: drain current VTT: output voltage R_onLS, R_onHS: on resistance VND, VNU: node VPD, VPU, VFASTD, VFASTU: node/voltage VIN: input voltage SENSU: high-side sensing signal SENSD: low-side sensing signal

Figure 1 is a schematic diagram of an existing low-dropout voltage regulator. FIG. 2 is a schematic diagram of a low voltage drop voltage regulator according to an embodiment of the present invention. FIG. 3 is a schematic diagram of changes in voltage signal, current signal and transistor switch resistance according to an embodiment of the present invention. 4A to 4C are circuit schematic diagrams of a low voltage drop regulator according to an embodiment of the present invention. FIG. 5 is a schematic diagram of changes in control voltage and control current according to an embodiment of the present invention.

200:Low dropout voltage regulator

210: Error amplifier

220: High-side driver

230: Low-side driver

240: High-side current sensor

250: High-side drive voltage adjustment circuit

251: Compensation capacitor

260: Low-side current sensor

270: Low-side drive voltage adjustment circuit

271: Compensation capacitor

280: High side switch

290: Low side switch

300:Memory

301: Capacitor

VREF: reference voltage

I_VTT: first control current

I_ref: second control current

I_d1: high-side drive current

I_d2: low-side drive current

I_SU2: high side sensing current

I_SD2: low-side sensing current

V_gHS, V_gLD: driving voltage

I_SU1: first feedback current

I_SD1: second feedback current

I_source: supply current

I_sink: drain current

Claims (6)

A low voltage dropout regulator has an output terminal and provides an output voltage, wherein the low voltage dropout regulator includes: an error amplifier coupled to the output terminal and generating a first control current and a second control current according to the output voltage and a reference voltage; a high-side switch coupled between an input voltage source and the output terminal; a high-side driver coupled between the error amplifier and the control terminal of the high-side switch, and providing a high-side drive current according to the first control current and the second control current; a high-side current sensor coupled to the high-side switch and generating a high-side sensing current; a high-side driving voltage adjustment circuit coupled to the control terminal of the high-side switch and receiving the high-side sensing current to adjust a driving voltage of the high-side switch; a low-side switch coupled between the output terminal and a ground terminal; and A low-side driver is coupled between the error amplifier and the control terminal of the low-side switch, and provides a low-side driving current according to the first control current and the second control current. A low-dropout voltage regulator as described in claim 1, further comprising: a low-side current sensor coupled to the low-side switch and generating a low-side sensing current; and A low-side driving voltage adjustment circuit is coupled to the control terminal of the low-side switch and receives the low-side sensing current to adjust a driving voltage of the low-side switch. The low-dropout voltage regulator of claim 2, wherein the error amplifier is further coupled to the high-side current sensor and a low-side current sensor, and based on the high-side sensing current and the low-side sensing The current adjusts the first control current and the second control current. The low voltage dropout voltage regulator of claim 1, wherein the relationship between the first control current and the second control current determines the flow direction of the high-side driving current and the low-side driving current. The low-dropout voltage regulator of claim 1, wherein the high-side driver includes: a first current mirror coupled to the error amplifier and receiving the first control current; a second current mirror coupled to the error amplifier and receiving the second control current; a third current mirror, including a first transistor, wherein the control terminal of the first transistor is coupled to the first current mirror, and the first terminal of the first transistor is coupled to an operating voltage; a fourth current mirror, including a second transistor, wherein the second transistor is coupled between the first current mirror and the third current mirror, and the control terminal of the second transistor is coupled to the second current Mirror, the second transistor turns on or off the path between the first current mirror and the third current mirror according to the current difference between the first control current and the second control current; and A high-side output terminal is coupled to the second terminal of the first transistor in the second current mirror and the third current mirror. The low-dropout voltage regulator of claim 1, wherein the low-side driver includes: a fifth current mirror coupled to the error amplifier and receiving the second control current; a sixth current mirror coupled to the error amplifier and receiving the first control current; a seventh current mirror, including a third transistor, wherein the control terminal of the third transistor is coupled to the fifth current mirror, and the first terminal of the third transistor is coupled to the operating voltage; An eighth current mirror, including a fourth transistor, wherein the fourth transistor is coupled between the fifth current mirror and the seventh current mirror, and the control terminal of the fourth transistor is coupled to the sixth current Mirror, the fourth transistor turns on or off the path between the sixth current mirror and the seventh current mirror according to the current difference between the first control current and the second control current; and A low-side output terminal is coupled to the second terminal of the third transistor in the sixth current mirror and the seventh current mirror.

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