CN100514245C - Voltage regulator - Google Patents

Abstract

A voltage regulator includes a voltage regulating unit and an overdrive unit. The voltage regulating unit outputs corresponding output voltage according to the input voltage. The overdrive unit comprises a voltage comparison circuit, which is coupled to the output end of the voltage regulator and is used for comparing the output voltage of the voltage regulator with a reference voltage and outputting an overdrive signal; the overdrive circuit is coupled between the voltage comparison circuit and the input end of the voltage regulation unit and regulates the input voltage of the voltage regulation unit according to the overdrive signal, wherein if the output voltage is greater than the reference voltage, the overdrive signal is a low logic level, and the input voltage is a normal level; if the output voltage is less than the reference voltage, the overdrive signal is a high logic level, and the overdrive unit increases the level of the input voltage.

Description

Voltage Regulator

technical field

The present invention relates to a voltage regulator, and more particularly to a voltage regulator capable of adjusting an input voltage in real time to maintain an output voltage level.

Background technique

Traditional voltage regulators usually output a stable voltage when the load is not considered. However, when the load current changes instantaneously, the output voltage will drop suddenly because it cannot provide enough driving current in real time. Especially when it is required to provide a large current driving capability, such as a source driver of a liquid crystal panel (LCD panel source driver), this phenomenon of voltage slump is more obvious.

Fig. 1 is a voltage regulator according to conventional technology. The voltage regulator 100 includes a voltage generator 110 and a voltage regulation unit 120 . The voltage generator 110 uses the common node of the current source I _REF and the resistor R13 to provide the input voltage INT to the negative input terminal of the operational amplifier 122 . Due to the Principle of Virtual Short Circuit, the voltage at the common node of the resistor R11 and the resistor R12 is equal to the input voltage INT. At this moment, the common node of the resistor R11 and the P-type transistor (PMOS transistor) P11 generates the output voltage OUT. The function of the capacitor _CL is to stabilize the output voltage OUT of the voltage regulator 100 so that it will not fluctuate drastically due to the instantaneous change of the load current 130 . As shown in FIG. 1 , when the load current I _L coupled to the traditional voltage regulator 100 changes more instantaneously, the phenomenon of the output voltage OUT suddenly dropping is more obvious. Therefore, the voltage regulator 100 must effectively improve the driving capability of the voltage regulation unit 120 when the output voltage OUT drops suddenly.

Contents of the invention

One of the objectives of the present invention is to provide a voltage regulator that can adjust the level of the input voltage to improve the driving capability of the voltage regulator when the output voltage drops suddenly due to load current fluctuations.

One of the objectives of the present invention is to provide a voltage regulator, which is suitable for driving a large current load, and adjusts the driving capability of the voltage regulator in real time according to the level change of the output voltage to maintain the level of the output voltage.

To achieve the above and other objectives, the present invention provides a voltage regulator, which includes a voltage regulation unit and an overdrive unit. The voltage regulation unit generates a corresponding output voltage according to the input voltage. The overdrive unit is coupled between the input end of the voltage adjustment unit and the output end of the voltage adjustment unit, and adjusts the input voltage according to the comparison result between the output voltage and the reference voltage. The overdrive unit includes a voltage comparator circuit coupled to the output terminal of the voltage regulator for comparing the output voltage of the voltage regulator with a reference voltage and outputting an overdrive signal; and an overdrive circuit coupled to the voltage comparator circuit Between the input terminal of the voltage regulation unit and according to the overdrive signal, the input voltage of the voltage regulation unit is adjusted, wherein if the output voltage is greater than the reference voltage, the overdrive signal is a low logic level, and the input voltage is a normal level ; If the output voltage is lower than the reference voltage, the overdrive signal is at a high logic level, and the overdrive unit increases the level of the input voltage.

Wherein, if the output voltage does not correspond to the reference voltage, the input voltage is adjusted so that the output voltage corresponds to the reference voltage.

The present invention utilizes the principle of overdrive to adjust the input voltage of the voltage regulator in real time according to the level change of the output voltage, so as to maintain sufficient driving capability, so that the voltage drop caused by the change of the load of the voltage regulator can be quickly recovered . Therefore, the voltage regulator of the present invention can be applied to loads requiring a relatively large driving current, such as a source driver of a liquid crystal display panel.

In order to make the above and other objects, features and advantages of the present invention more comprehensible, preferred embodiments of the present invention will be described in detail below together with the accompanying drawings.

Description of drawings

FIG. 1 is a voltage regulator according to conventional technology.

FIG. 2 is a circuit block diagram of a voltage regulator according to an embodiment of the invention.

FIG. 3 is a circuit diagram of a voltage regulating unit according to another embodiment of the present invention.

FIG. 4 is a circuit diagram of a voltage regulating unit according to another embodiment of the present invention.

FIG. 5 is a circuit diagram of a voltage generating circuit according to an embodiment of the present invention.

FIG. 6 is a circuit diagram of an overdrive circuit according to an embodiment of the present invention.

Description of main component symbols

VDD: working voltage

GND: ground terminal

INT: input voltage

OUT: output voltage

C _L : Capacitance

I _L : load current

I _REF , I ₅₁ , I ₆₁ ~I ₆₄ : current source

R11～R13, R31, R32, R41, R42: resistance

R51～R53, R61～R65: resistance

REV: reference voltage

P11, P31, P51: PMOS transistors

N41, N51: NMOS transistors

OD: overdrive signal

S61～S64: switch

VB1, VB2: DC bias voltage

100, 200: voltage regulator

110: Voltage generator

120: Voltage regulation unit

122, 322, 422: operational amplifiers

130, 330, 430: load

210: Overdrive unit

220, 420: voltage regulation unit

212: Voltage generating circuit

214: Comparator

215: Voltage comparison circuit

216: Overdrive circuit

Detailed ways

FIG. 2 is a circuit block diagram of a voltage regulator according to an embodiment of the invention. The voltage regulator 200 includes an overdrive unit 210 and a voltage regulation unit 220 . Wherein, the voltage regulating unit 220 generates an output voltage OUT according to the input voltage INT, and the output voltage OUT has a predetermined proportional relationship with the input voltage INT, and the proportional relationship can be determined by the circuit structure of the voltage regulating unit 220 .

The overdrive unit 210 is coupled between the input terminal and the output terminal of the voltage adjustment unit 220 , and adjusts the input voltage INT according to the comparison result between the output voltage OUT and the reference voltage REV. The overdrive unit 210 includes a voltage comparison circuit 215 and an overdrive circuit 216. The voltage comparison circuit 215 is coupled to the output terminal of the voltage regulator 200 for comparing the output voltage OUT with the reference voltage REV, and outputs an overdrive signal OD to the overdrive drive circuit 216 . The overdrive circuit 216 is coupled between the voltage comparison circuit 215 and the input terminal of the voltage adjustment unit 220 , and adjusts the input voltage INT according to the above-mentioned overdrive signal OD. When the load (load current or load capacitance) of the output voltage OUT changes instantaneously, the voltage sag phenomenon of the output voltage OUT is reduced.

In this embodiment, the voltage comparison circuit 215 includes a voltage generation circuit 212 and a comparator 214 . The voltage generating circuit 212 is used to generate the above-mentioned reference voltage REV, and the comparator 214 is used to compare the output voltage OUT with the reference voltage REV, and output the overdrive signal OD according to the comparison result. In this embodiment, if the output voltage OUT is greater than the reference voltage REV, the comparator 214 outputs an overdrive signal OD of a low logic level; if the output voltage OUT is smaller than the reference voltage REV, the comparator 214 outputs an overdrive signal OD of a high logic level. Drive signal OD.

Next, the voltage adjustment unit 220 of this embodiment will be further described. FIG. 3 is a circuit diagram of a voltage regulating unit according to another embodiment of the present invention. The voltage regulation unit 220 is coupled between the overdrive unit 210 and the load 330 , and generates an output voltage OUT to the load 330 according to the input voltage INT output by the overdrive circuit 210 .

In this embodiment, the voltage regulating unit 220 includes an operational amplifier 322, a P-type transistor P31, a resistor R31, a resistor R32, and a capacitor C _L . The negative input terminal of the operational amplifier 322 is coupled to the input voltage INT, and the positive input terminal thereof is coupled to the common node of the resistors R31 and R32. The P-type transistor P31 is coupled between the operating voltage VDD and the resistor R31 , and the gate of the P-type transistor P31 is coupled to the output terminal of the operational amplifier 322 . Because the operational amplifier 322 has a virtual short-circuit characteristic, the voltage level of the positive input terminal of the operational amplifier 322 will change with the voltage level of the negative input terminal (the output voltage INT). Therefore, the output voltage OUT can be equal to INT*(1+R31/R32), INT in the above formula represents the voltage value of the input voltage INT, and R31 and R32 represent the resistance values of the resistors R31 and R32 respectively. Therefore, as long as the ratio of the resistors R31 and R32 is adjusted, the relative relationship between the output voltage OUT and the input voltage INT can be adjusted. The function of the capacitor C _L is to stabilize the output voltage OUT of the voltage regulator 220 so that it will not fluctuate violently due to the instantaneous change of the load current _IL .

In this embodiment, when the voltage comparator circuit 215 is balanced in a steady state, the output voltage OUT is higher than the reference voltage REV, the overdrive signal OD is at a low logic level, and the load 330 is represented by the equivalent load current IL. When the load 330 changes instantaneously, the output voltage OUT will have a voltage drop phenomenon. When the output voltage OUT is lower than the reference voltage REV, the overdrive signal OD turns to a high logic level, so the overdrive unit 210 will increase the input voltage INT, thereby increasing the driving capability of the operational amplifier 322, so that the P-type transistor P31 is turned on The current rises rapidly. And the voltage value of the output voltage OUT is rapidly increased through a higher current conduction capability, reducing the phenomenon of the output voltage OUT slump. When the output voltage OUT returns to be higher than the reference voltage REV, the overdrive signal OD returns to a low logic level, and the overdrive unit 210 adjusts the input voltage INT to the original voltage level.

FIG. 4 is a circuit diagram of a voltage regulating unit according to another embodiment of the present invention. The voltage regulation unit 420 is coupled between the overdrive unit 210 and the load 430 . The voltage regulation unit 420 includes an operational amplifier 422 , an N-type transistor (NMOS transistor) N41 , and resistors R41 and R42 . The resistors R41 and R42 are coupled in series between the working voltage VDD and the N-type transistor N41 , and the common node of the resistors R41 and R42 is coupled to the positive input terminal of the operational amplifier 422 . Therefore, the voltage level of the common node of the resistors R41, R42 is equal to the input voltage INT. The output voltage OUT can be equal to the working voltage VDD minus the bias voltage on the resistors R41 and R42. Those skilled in the art should be able to easily deduce the relative relationship between the output voltage OUT and the input voltage INT in FIG. 4 through the disclosure of the present invention, which will not be repeated here.

The main difference between the load 430 in this embodiment and the load 330 in FIG. 3 is that the current direction of the load current _IL is different. It only shows that the voltage regulating circuit of this embodiment is applicable to different types of loads, and the applicable loads of the present invention are not limited to the equivalent circuit forms of the above loads 330 and 430 .

Next, the implementation of the voltage generating circuit 212 in this embodiment will be further described. FIG. 5 is a circuit diagram of a voltage generating circuit according to the present embodiment. Only three different voltage generation circuits are listed in Figure 5 (Figure 5(a)-Figure 5(c)), but the present invention is not limited thereto, as long as the method that can generate a stable voltage source is applicable to this implementation Example voltage generating circuit.

In FIG. 5(a), the voltage value of the reference voltage REV can be adjusted by controlling the current value output from the current source _I51 to the resistor R51. In FIG. 5(b), the P-type transistor P51 is used to replace the current source I51. By controlling the bias voltage _VB1 , the conduction current of the P-type transistor P51 can be controlled, and further, the common node between the resistor R52 and the P-type transistor P51 can be controlled. generated reference voltage REV. In FIG. 5( c ), the resistor R53 and the N-type transistor N51 are coupled in series between the working voltage VDD and the ground terminal GND, and the voltage value of the reference voltage REV can be adjusted by controlling the voltage value of the bias voltage VB2 . Those with ordinary knowledge in the technical field should be able to easily deduce the operation details and principle of the circuit in FIG. 5 through the disclosure of the present invention, which will not be repeated here.

FIG. 6 is a circuit diagram of an overdrive circuit according to the present embodiment. In this embodiment, only three implementations of the overdrive circuit 216 are listed (FIG. 6(a)-FIG. 6(c)), and the present invention is not limited thereto, as long as the input voltage INT can be adjusted according to the overdrive signal OD circuit. In the example of FIG. 6( a )- FIG. 6( c ), the switches S61 - S64 are selectively turned on or opened according to the overdrive signal OD to adjust the input voltage INT. Next, the circuit structure of FIG. 6(a)-FIG. 6(c) will be further described.

In FIG. 6( a ), the overdrive circuit 216 includes resistors R61 , R62 , switches S61 , S62 and a current source I ₆₁ . The resistors R61 and R62 are coupled in series between the current source _I61 and the ground terminal GND. One terminal of the switch S61 is coupled to the common node of the current source _I61 and the resistor R61 , and the other terminal of the switch S61 is coupled to the output terminal of the overdrive circuit 216 . One end of the switch S62 is coupled to the common node of the resistors R61 and R62 , and the other end of the switch S62 is coupled to the output end of the overdrive circuit 216 . The output terminal of the overdrive circuit 216 is used to generate the input voltage INT.

Wherein, the switches S61 and S62 are turned on or not according to the overdrive signal OD output by the voltage comparator circuit 215 . Please refer to the embodiment in FIG. 3 , in a normal state, the output voltage OUT can be made higher than the reference voltage REV, the switch S61 is open, and the switch S62 is turned on. When the output voltage OUT is lower than the reference voltage REV due to load variation, the switch S61 is turned on and the switch S62 is opened. When the output voltage OUT is higher than the reference voltage REV, it returns to the normal state, that is, the switch S62 is turned on and the switch S61 is opened. The input voltage INT changes according to the conduction state of the switches S61, S62. When the switch S61 is turned on, the input voltage INT is relatively large, and when the switch S62 is turned on, the input voltage INT is obviously smaller, because there is only a voltage difference between the resistor R62 and the ground terminal. The voltage level of the input voltage INT can be adjusted by controlling the conduction states of the switches S61 and S62. In the example shown in FIG. 4 , under normal conditions, the output voltage OUT can be lower than the reference voltage REV, the switch S61 is turned on, and the switch S62 is opened. When the output voltage OUT is higher than the reference voltage REV due to load variation, the switch S62 is turned on and the switch S61 is opened. When the output voltage OUT is lower than the reference voltage REV, it returns to the normal state, that is, the switch S61 is turned on, and the switch S62 is opened.

In FIG. 6(b), the resistor R63 and the resistor R64 are coupled in series between the current source _I62 and the ground terminal GND, and the switch S63 is coupled to both ends of the resistor R63. Please refer to the embodiment in FIG. 3 , under normal conditions, the output voltage OUT can be made greater than the reference voltage REV, and the switch S63 is turned on under normal conditions. When the output voltage OUT is lower than the reference voltage REV due to load variation, the switch S63 is opened, and the input voltage INT rises accordingly. Taking the embodiment of FIG. 4 as an illustration, under normal conditions, the output voltage OUT can be lower than the reference voltage REV, and the switch S63 is open under normal conditions. When the output voltage OUT is greater than the reference voltage REV due to load variation, the switch S63 is turned on, and the input voltage INT drops accordingly.

In FIG. 6( c ), the current source I ₆₃ is coupled to the resistor R65 , one end of the switch S64 is coupled to the current source I ₆₄ , and the other end of the switch S64 is coupled to the common node of the current source I ₆₃ and the resistor R65 . Please refer to the embodiment of FIG. 3 , under normal conditions, the output voltage OUT can be made greater than the reference voltage REV, and the switch S64 is open under normal conditions. When the output voltage OUT is lower than the reference voltage REV due to load variation, the switch S64 is turned on, and the currents of the current sources I ₆₃ and I ₆₄ both flow through the resistor R65 . Therefore, the input voltage INT rises accordingly. Taking the embodiment of FIG. 4 as an illustration, under normal conditions, the output voltage OUT can be lower than the reference voltage REV, and the switch S64 is turned on under normal conditions. When the output voltage OUT is greater than the reference voltage REV due to load variation, the switch S64 is open, and only the current from the current source _I63 flows through the resistor R65. Therefore, the input voltage INT drops accordingly.

The above-mentioned embodiment of Fig. 6 (a)-(c) has illustrated that in several cases, according to different circuit structures of the overdrive circuit, the preset relationship between the reference voltage and the output voltage is adjusted to reduce the impact of the load change on the output voltage Impact. Only by setting an appropriate reference voltage and matching the corresponding overdrive circuit structure, when the load changes, not only can the situation of output voltage sag be reduced, but also the situation of voltage swell can be reduced, so that the voltage regulator has more stable output voltage. The above-mentioned Figure 6 (a)-(c) is only an embodiment of the present invention, and does not limit the circuit structure of the overdrive circuit of the present invention. Those with ordinary knowledge in the technical field should be able to Other feasible circuit structures can be deduced easily, so we won't repeat them here.

In another embodiment of the present invention, the principle of resistive voltage division can also be used to generate multiple voltage levels according to the comparison result between the output voltage OUT and the reference voltage REV. Using the above-described plurality of voltage levels, the input voltage INT of the voltage regulator 200 is varied. At the same time, the variation range of the input voltage can also be adjusted according to the variation range of the output voltage OUT, so as to maintain the stability of the output voltage OUT. Those who have ordinary knowledge in the technical field can easily deduce the embodiment of using the resistor voltage divider as the input voltage INT through the disclosure of the present invention, which will not be repeated here.

The invention utilizes the principle of overdrive. When the output voltage of the voltage regulator changes due to transient changes in the load current, the voltage level of the input voltage is adjusted in real time to improve the driving capability of the voltage regulator and reduce the impact of load changes on the output voltage. Impact.

Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection of the present invention The scope is as defined by the appended claims.

Claims (12)

1. A voltage regulator comprising: a voltage regulating unit, generating an output voltage according to an input voltage; and an overdrive unit, coupled between the input terminal of the voltage regulation unit and the output terminal of the voltage regulation unit, and adjusts the input voltage according to a comparison result between the output voltage and a reference voltage, wherein the overdrive unit including a voltage comparator circuit, coupled to the output terminal of the voltage regulator, for comparing the output voltage of the voltage regulator with the reference voltage, and outputting an overdrive signal; and an overdrive circuit, coupled to the voltage between the comparison circuit and the input terminal of the voltage regulation unit, and adjust the input voltage of the voltage regulation unit according to the overdrive signal, Wherein if the output voltage is greater than the reference voltage, the overdrive signal is a low logic level, and the input voltage is a normal level; if the output voltage is lower than the reference voltage, the overdrive signal is a high logic level, The overdrive unit increases the level of the input voltage. 2. The voltage regulator as claimed in claim 1, wherein the voltage regulation unit comprises: An operational amplifier has a positive input terminal, a negative input terminal, and an output terminal, and the negative input terminal of the operational amplifier is coupled to the input voltage; A P-type transistor, the P-type transistor is coupled between an operating voltage and a first resistor, and the gate of the P-type transistor is coupled to the output terminal of the operational amplifier; a second resistor, coupled between the other end of the first resistor and a ground terminal, and the common node of the first resistor and the second resistor is coupled to the positive input terminal of the operational amplifier; and a capacitor coupled between the output terminal of the voltage regulation unit and a ground terminal; Wherein, the negative input terminal of the operational amplifier is the input terminal of the voltage regulation unit, and the common node of the P-type transistor and the first resistor is the output terminal of the voltage regulation unit, and generates the output voltage. 3. The voltage regulator as claimed in claim 2, wherein if the output voltage is lower than the reference voltage, the input voltage is increased. 4. The voltage regulator as claimed in claim 1, wherein the voltage regulation unit comprises: An operational amplifier has a positive input terminal, a negative input terminal, and an output terminal, and the negative input terminal of the operational amplifier is coupled to the input voltage; An N-type transistor, the N-type transistor is coupled between a first resistor and a ground terminal, and the gate of the N-type transistor is coupled to the output terminal of the operational amplifier; a second resistor, coupled between an operating voltage and the other end of the first resistor, and the common node of the first resistor and the second resistor is coupled to the positive input terminal of the operational amplifier; and a capacitor coupled between the output terminal of the voltage regulation unit and a ground terminal; Wherein, the negative input end of the operational amplifier is the input end of the voltage adjustment unit, and the common node between the N-type transistor and the first resistor is the output end of the voltage adjustment unit, and generates the output voltage. 5. The voltage regulator as claimed in claim 4, wherein if the output voltage is greater than the reference voltage, the input voltage is decreased. 6. The voltage regulator as claimed in claim 1, wherein the voltage comparison circuit comprises: a voltage generating circuit for generating the reference voltage; and A comparator is used to compare the output voltage of the voltage regulator with the reference voltage, and output an overdrive signal to the overdrive circuit. 7. The voltage regulator as claimed in claim 6, wherein the voltage generating circuit comprises: a resistor, one end of which is coupled to a ground; and A P-type transistor, coupled between an operating voltage and the other end of the resistor, the gate of the P-type transistor is coupled to a DC bias voltage, and the common node of the P-type transistor and the resistor outputs the reference voltage . 8. The voltage regulator as claimed in claim 6, wherein the voltage generating circuit comprises: a current source; and A resistor is coupled between the current source and a ground terminal, and a common node of the resistor and the current source outputs the reference voltage. 9. The voltage regulator as claimed in claim 6, wherein the voltage generating circuit comprises: a resistor, one end of which is coupled to an operating voltage; and An N-type transistor, coupled between the other end of the resistor and a ground terminal, the gate of the N-type transistor is coupled to a DC bias voltage, and the common node of the N-type transistor and the resistor outputs the reference voltage . 10. The voltage regulator as claimed in claim 1, wherein the overdrive circuit comprises: a current source; A first resistor and a second resistor are coupled in series between the current source and a ground terminal; a first switch, one end of the first switch is coupled to the common node of the current source and the first resistor, and the other end of the first switch is coupled to the output end of the overdrive circuit; and a second switch, one end of the second switch is coupled to the common node of the first resistor and the second resistor, and the other end of the second switch is coupled to the output end of the overdrive circuit; Wherein, if the output voltage is greater than the reference voltage, the first switch is open and the second switch is turned on; if the output voltage is lower than the reference voltage, the first switch is turned on, the second switch is open, and the The output end of the overdrive circuit outputs the input voltage of the voltage regulation unit. 11. The voltage regulator as claimed in claim 1, wherein the overdrive circuit comprises: a current source; A first resistor and a second resistor are coupled in series between the current source and a ground terminal; and A switch, one end of the switch is coupled to the common node of the current source and the first resistor, the other end of the switch is coupled to the common node of the first resistor and the second resistor, and the current source and the first resistor The common node of the resistors is the output end of the overdrive circuit; Wherein, if the output voltage is greater than the reference voltage, the switch is turned on; if the output voltage is lower than the reference voltage, the switch is open, and the output terminal of the overdrive circuit outputs the input voltage of the voltage regulation unit. 12. The voltage regulator as claimed in claim 1, wherein the overdrive circuit comprises: a first current source; a second current source; a resistor coupled between the first current source and a ground; and a switch, one end of the switch is coupled to the second current source, and the other end of the switch is coupled to the common node of the first current source and the resistor; Wherein, if the output voltage is higher than the reference voltage, the switch is open, and if the output voltage is lower than the reference voltage, the switch is turned on, and the output terminal of the overdrive circuit outputs the input voltage of the voltage adjustment unit.

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