CN101242141A - High-efficiency and low-noise power supply device and method for converting voltage - Google Patents

Abstract

The invention provides a high-efficiency and low-noise power supply device and a method for converting voltage, comprising the following steps: a switching power supply circuit for converting an input voltage into an intermediate voltage; a low voltage drop stabilizing circuit, which converts the intermediate voltage into an output voltage to provide a load current to a load; and a feedback control circuit for adjusting the noise filtering capability of the low dropout voltage regulator circuit to increase with the increase of the load current. The device of the invention can dynamically and automatically adjust the voltage conversion ratio between the two stages of circuits so as to optimize the efficiency and the noise balance of the whole device.

Description

High-efficiency and low-noise power supply device and method for converting voltage

technical field

The present invention relates to a high-efficiency and low-noise power supply device, in particular to a power supply composed of a switching power supply circuit (Switching Regulator) and a low dropout regulator circuit (LDO, Low Drop Out Regulator). device, and the device can dynamically and automatically adjust the voltage conversion ratio between the two-stage circuits, so as to optimize the efficiency and noise balance of the overall device. In addition, the present invention also proposes a related voltage conversion method.

Background technique

Generally speaking, the switching power supply circuit is more efficient in voltage conversion without wasting energy; the output voltage of the low dropout voltage regulator circuit has lower ripple noise (ripple noise). Therefore, referring to FIG. 1 , a power supply device combining the two is proposed in the prior art, which firstly converts the input voltage Vin into an intermediate voltage Vm, and then converts it into an output voltage Vout. The purpose is to convert the voltage with high efficiency through the first-stage switching power supply circuit (SR) 10, and then pass through the second-stage low-dropout voltage regulator circuit (LDO) 20 to filter the ripple noise in the intermediate voltage Vm News. Under this purpose, in the prior art, Vm is usually designed to be as close as possible to Vout, so that most of the voltage conversion from Vin to Vout is completed in the first-stage switching power supply circuit, so as to improve the conversion as much as possible. efficiency.

The ability of the low-dropout voltage regulator circuit to filter ripple noise is called the power supply rejection ratio (PowerSupply Rejection Ratio, hereinafter referred to as PSRR in this manual). PSRR is related to three factors: the input-to-output voltage drop of the low-dropout voltage regulator circuit value, the load current at the output, and the internal consumption current (quiescent current) of the low dropout regulator circuit. The higher the voltage drop value, the better the PSRR; the higher the load current, the worse the PSRR; the higher the internal consumption current, the better the PSRR. But obviously, if the voltage drop value and internal consumption current increase, it will be unfavorable to the voltage conversion efficiency.

In the prior art, no adaptive design is made for the requirements of the load side. The consideration is very simple, that is, the voltage drop between the intermediate voltage Vm and the output voltage Vout is designed to be as low as possible, that is, the output of the first-stage switching power supply circuit is set to be a constant value. Although this design is simple and has the advantage of high conversion efficiency, the disadvantage is that if the load end is sensitive to noise, this prior art circuit cannot meet the requirements of the load end.

In detail, please refer to Figure 2, which is a conceptual schematic diagram, where the abscissa represents the load current, that is, the output current of the power supply device, and the ordinate represents the measurement. It can be seen from the figure that as the load current (output current) increases, The noise of the intermediate voltage Vm will increase, but the PSRR of the low dropout regulator circuit will decrease. The result of multiplying the two is shown in the third schematic line, the overall noise of the output voltage Vout will increase as the load current increases.

In view of this, it is obvious to provide a power supply device that can dynamically control the conversion efficiency and output noise, and achieve a balance between them according to the requirements of the load end.

Contents of the invention

In view of this, the present invention aims at the deficiencies of the above-mentioned prior art, and proposes a power supply device to solve the aforementioned problems and achieve an optimal balance between conversion efficiency and output noise.

The second object of the present invention is to provide a voltage conversion method suitable for a power supply device.

To achieve the above purpose, in one embodiment of the present invention, a high-efficiency and low-noise power supply device is provided, including: a switching power supply circuit, which converts an input voltage into an intermediate voltage ; a low dropout voltage regulator circuit, which converts the intermediate voltage into an output voltage to provide a load current to a load; and a feedback control circuit, which adjusts the noise filtering capability of the low dropout voltage regulator circuit so that it follows the increases with increasing load current.

In the above embodiment, when the load current increases, the feedback control circuit can increase the voltage drop between the intermediate voltage and the output voltage, or increase the internal consumption current of the low dropout voltage stabilizing circuit.

In addition, according to another embodiment of the present invention, a method for converting voltage is provided, including the following steps: (A) providing a switching power supply circuit, which converts an input voltage into an intermediate voltage; (B) providing a low-dropout voltage regulator circuit, which converts the intermediate voltage into an output voltage to supply a load current to a load; and (C) adjusting the noise filtering capability of the low-dropout voltage regulator circuit so that it increases with the load current And increase.

In the above method, the signal related to the noise filtering capability of the low dropout voltage stabilizing circuit can be: the gate voltage signal of the output stage transistor in the low dropout voltage stabilizing circuit, the OR gate source voltage signal, or the gate drain The voltage signal, or the output voltage signal of the error amplifier in the low dropout regulator circuit, or the load current signal, or the abnormal signal of the load.

The specific embodiments will be described in detail below, so that it is easier to understand the purpose, technical content, characteristics and effects of the present invention.

Description of drawings

FIG. 1 is a schematic circuit diagram of a power supply device in the prior art.

Figure 2 schematically illustrates the disadvantages of the prior art.

3A-3C are used to illustrate the principle of the present invention.

FIG. 4 is a schematic circuit diagram showing one embodiment of the power supply device of the present invention.

5A and 5B illustrate how to use the modulation signal MOD to control the switching power supply circuit.

6, 7 and 8 illustrate more specific embodiments of feedback control circuits, which correspond to low-dropout regulator circuits using PMOS as output-stage transistors.

9A and 9B illustrate the alternatives of components in the embodiments of FIGS. 6 , 7 and 8 .

FIG. 10 and FIG. 11 illustrate another two specific embodiments of the feedback control circuit, which correspond to the low-dropout regulator circuit using NMOS as the output-stage transistor.

FIG. 12 is a schematic circuit diagram showing still another embodiment of the power supply device of the present invention.

FIG. 13 illustrates how to use the modulating signal MOD to control the internal consumption current of the low dropout regulator circuit.

FIG. 14A and FIG. 14B illustrate the method of generating the modulating signal MOD through feedback from the load circuit.

15A and 15B are schematic circuit diagrams showing yet another embodiment of the power supply device of the present invention.

Explanation of symbols in the figure

10 Switching power supply circuit

15 Voltage Summing Circuit

16 voltage subtraction circuit

20 Low drop voltage regulator circuit

30 Feedback control circuit

33 current mirror

42-bit Error Rate (Bit Error Rate, BER) counter

44 Digital to Analog Converter

50 load

EA10, EA20 Error Amplifier

FB Feedback voltage in switching power supply circuit

GM transduction circuit

MOD modulation signal

MOD’ digital modulation signal

Q21, Q22, Q31, Q32, Q33, Q34, Q35 Transistors

R21, R22, R31, R32, R41 resistors

Vin input voltage

Vm intermediate voltage

Vout output voltage

Vref10, Vref20 reference voltage

Detailed ways

Firstly, the concept of the present invention will be described in principle. Please refer to Figures 3A-3C, first explain Figure 3A, one of the basic concepts of the present invention is: when the load current increases, the PSRR of the low-dropout voltage regulator circuit is correspondingly increased to keep the output noise at the load end. Within the acceptable range (the icon is a conceptual illustration, and all the schematic lines are not necessarily straight lines; the overall noise of the output voltage Vout does not need to be a constant value). The way to achieve the result in Fig. 3A, for example, as shown in Fig. 3B, the voltage drop value of the low-dropout voltage regulator circuit increases with the increase of the load current, or as shown in Fig. 3C, the internal consumption current Icc of the low-dropout voltage regulator circuit It increases with the increase of load current, of course, both can be used together, or other methods can be adopted.

Please refer to FIG. 4 , which shows an embodiment of the present invention in a schematic circuit diagram. As shown in the figure, in this embodiment, a feedback control circuit 30 is provided, according to the internal or external signal of the low dropout voltage stabilizing circuit 20 (the icon is for illustration, so only the internal connection is drawn; please refer to Figure 14A for comparison. 14B ), the feedback generates the modulating signal MOD to adjust the output setting of the first-stage switching power supply circuit 10 . As far as the switching power supply circuit 10 is concerned, the method for adjusting its output setting is, for example: adjusting the input of the error amplifier EA10 inside it, as shown in FIGS. The input offset voltage (Input Offset Voltage) and so on. The detailed structure of the switchable power supply circuit is well known to those skilled in the art. Under the disclosure and teaching of the concept of the present invention, those skilled in the art should be able to consider various modulating signal MODs according to the spirit of the present invention. The method for adjusting the output setting of the switching power supply circuit 10 should belong to the scope of the present invention. The point is that according to the modulation signal MOD, the output of the switching power supply circuit 10 is adjusted, so that the intermediate voltage Vm changes according to the modulation signal MOD, and the voltage drop value of the second-stage low-dropout voltage regulator circuit 20 is also adjusted correspondingly. Furthermore, the PSRR of the low dropout regulator circuit 20 is adjusted.

In FIG. 5A and FIG. 5B , the circuits 15 and 16 for adding or subtracting two voltages to output can be realized in many ways, which are well known to those skilled in the art and will not be detailed here. For example, the two voltages can be converted into currents respectively, and the currents can be added or subtracted, and then the currents can be converted into a voltage, and the voltage is the sum/difference of the two voltages.

There are many ways for the feedback control circuit 30 to generate the modulating signal MOD. For example, it can be based on the load current, or the signal of the internal components of the low-dropout voltage regulator circuit 20, or a signal that has a pointer meaning to the PSRR of the low-dropout voltage regulator circuit 20. produce it. Several specific examples are given below for illustration. It should be emphasized that these examples are provided to prove that the present invention can be implemented, but not to limit the scope of the present invention;

The first embodiment of the feedback control circuit 30 can be referred to FIG. 6 , the low dropout voltage stabilizing circuit 20 on the left in the figure is a typical low dropout voltage stabilizing circuit using PMOS as the output stage transistor, and the right side is the feedback control circuit of the present invention 30. By matching the resistances of resistors R21, R22, R31, R32 and transistors Q21 and Q31, the current I1 can be much larger than the current I2, so the energy consumption of the feedback control circuit 30 itself is small. Let the gate-source voltage of the transistor Q21 be Vgs21, and the gate-source voltage of the transistor Q31 be Vgs31, then the current I2 flowing through the transistor Q31 is equal to (Vgs21-Vgs31)/R31, and because the current is very small, Vgs31 is approximately equal to the transistor Q31 The conduction threshold of Q31 is Vth31, so the current I2 is approximately equal to (Vgs21-Vth31)/R31, and the voltage value of the modulating signal MOD (in this example, an analog voltage signal) is equal to

R32*I2=R32(Vgs21-Vth31)/R31

Vth31, R31, and R32 are all fixed values, so the modulation signal MOD is only a function of Vgs21, that is, a function of the load current Iout (Iout≈I1).

The second embodiment of the feedback control circuit 30 can be referred to FIG. 7. The difference between this embodiment and the previous embodiment is that the modulation signal MOD is only a function of the gate-drain voltage Vgd21 of the transistor Q21. Same as the previous example, since the current I2 is very small, Vgs31 is approximately equal to the conduction threshold Vth31 of the PMOS transistor Q31, and Vgs32 is approximately equal to the conduction threshold Vth32 of the NMOS transistor Q32. The gate of the PMOS transistor Q31 is connected to the drain of the transistor Q21, so the current I2 is approximately equal to (Vgd21-Vth31-Vth32)/R31, and the voltage value of the modulation signal MOD (in this example, an analog voltage signal) is equal to

R32*I2=R32(Vgd21-Vth31-Vth32)/R31

Vth31, Vth32, R31, and R32 are all fixed values, so the modulation signal MOD is only a function of Vgd21.

Refer to FIG. 8 for a third embodiment of the feedback control circuit 30. In this embodiment, the modulation signal MOD' is a digital signal. The application of the digital modulation signal MOD' is illustrated as follows: For example, there may be only two operating modes at the load end, and the intermediate voltage Vm only needs to be changed between the two voltage values, so there is no need for continuously changing analog modulation Signal MOD, and only two-level digital modulation signal MOD' is required; at this time, the modulation signal MOD' is not used in the manner shown in Figures 5A and 5B, but is used to control the switching power supply circuit in other ways 10, to adjust the intermediate voltage Vm.

In this embodiment, at the switching point of the MOD output level, I2=Ib, so the voltage across the resistor R31 is equal to Ib*R31. If the current mirror 33 works normally, it means that both the NMOS transistor Q32 and the NMOS transistor Q33 are turned on, that is, the gate voltage Vg21 of the transistor Q21 (that is, the output of the error amplifier EA20) is equal to (Vth32+Ib*R31+Vth33), at this time If Vg21 is slightly increased, the modulation signal MOD' is at a low level because the conduction current of the NMOS transistor Q34 increases. Relatively, if Vg21 is smaller than (Vth32+Ib*R31+Vth33), the conduction current of the NMOS transistor Q34 is smaller than Ib, and the voltage of the modulating signal MOD' rises to a high level. Since Vth32, Ib, R31, and Vth33 are all constant values, the high and low levels of the modulating signal MOD' depend on the gate voltage Vg21 of the transistor Q21:

MOD'=H when Vg21<(Vth32+Ib*R31+Vth33)

MOD'=L when Vg21>(Vth32+Ib*R31+Vth33)

The source follower (transistor Q31 in FIG. 6, transistor Q32 in FIG. 7, and FIG. 8) in the above three embodiment circuits can be replaced by the circuit in FIG. 9A or FIG. 9B, so that the conduction of the transistor can be critical The value is 0, which facilitates the establishment of a simpler functional relationship; in the figure, G, S, and D respectively replace the original gate, source, and drain of the transistor Q31 or Q32, and can be connected to corresponding nodes.

In addition, in the above three embodiments, the output stage transistor of the low dropout voltage stabilizing circuit 20 is a PMOS transistor, but of course, if the output stage transistor of the low dropout voltage stabilizing circuit 20 is an NMOS transistor, the present invention is also feasible; the specific embodiment is shown in Fig. 10. Figure 11. FIG. 10 is similar to FIG. 7, but the output stage transistor is an NMOS transistor Q22, and its gate-source voltage is Vgs22. In this embodiment, the modulation signal MOD is an analog voltage signal, and its voltage value is equal to R32*I2=R32(Vgs22-Vth31-Vth32)/R31. FIG. 11 is similar to FIG. 8, but the output stage transistor is an NMOS transistor Q22, and the NMOS transistor Q32 is changed to a PMOS transistor Q35. In this embodiment, the modulation signal MOD' is a digital signal. When the current mirror 33 works normally, it means that both the transistors Q35 and Q33 are turned on, and when the voltage difference between the supply voltage Vpp and the gate voltage Vg22 of the transistor Q22 (Vpp When -Vg22) is greater than (Vth35+Ib*R31), the conduction current of the NMOS transistor Q34 is greater than Ib, so the modulation signal MOD' is at a low level. Relatively, if (Vpp-Vg22) is less than (Vth35+Ib*R31), the conduction current of the NMOS transistor Q34 is less than Ib, and the voltage of the modulation signal MOD' rises to a high level. Since Vpp, Vth35, Ib, and R31 are all constant values, the high and low levels of the modulating signal MOD' depend on the gate voltage Vg22 of the transistor Q22:

MOD'=H when Vg22>Vpp-(Vth35+Ib*R31)

MOD'＝L when Vg22＜Vpp-(Vth35+Ib*R31)

The supply voltage Vpp provided to the error amplifier EA20 in FIG. 10 and FIG. 11 can directly use the input voltage Vin, or use other voltages higher than Vm.

In FIG. 4 and FIGS. 5A and 5B , the modulation signal MOD feeds back to control the output setting of the first-stage switching power supply circuit 10 to adjust the intermediate voltage Vm. According to FIG. 3C , under the concept of the present invention, the internal consumption current of the low dropout regulator circuit 20 can also be feedback-controlled, as shown in FIG. 12 . Its specific embodiment is shown in FIG. 13 as an example. In this embodiment, the power consumption of the error amplifier EA20 is represented by the current Ics on the path 100, which is originally a constant value Ic without other circuit control. According to the present invention, a transconductance circuit (transconductance) GM can be used to generate a current I3 using the modulation signal MOD, and the current value is equal to the voltage value of the modulation signal MOD divided by the resistor R41. The current Ics is equal to the sum of the fixed value Ic and (MOD/R41). In other words, the current Ics can be increased by increasing the voltage value of MOD, and the current Ics is the main part of the internal consumption current of the low dropout regulator circuit 20 .

In the above-mentioned embodiments, the modulating signal MOD is obtained from the low-dropout regulator circuit 20 , but the present invention is not limited thereto, and the modulating signal MOD can also be fed back from the load end. Because the load end may be various circuits, it is not possible to describe them one by one. Just two examples are shown in Figure 14A and Figure 14B. Assuming that the load end is sensitive to ripple noise, because ripple noise has an oscillating characteristic, it may cause A certain bit error rate (Bit Error Rate, BER) is generated due to the intermittent abnormality between the load terminals. At this time, the bit error rate can be counted and output by the bit error rate counter 42, and then converted by the digital-to-analog converter 44 into The analog voltage signal can be used as the modulating signal MOD; of course, the digital modulating signal MOD' can also be generated through a logic circuit. Under the guidance of this case, those familiar with the technology can design various feedback methods to generate modulation signal MOD or modulation signal MOD' according to the circuit characteristics of the load end. They will not be described in detail here, but they should all belong to The scope of rights of the present invention.

In addition to the above, as shown in Figure 15A and Figure 15B, it is of course also possible to directly detect the current signal and generate the modulation signal MOD (or modulation signal MOD') accordingly, and the detailed method will not be shown here. .

The present invention has been described above with reference to the preferred embodiments, but the above description is only for making those skilled in the art understand the content of the present invention easily, and is not intended to limit the scope of rights of the present invention. As mentioned above, those skilled in the art should immediately conceive of various equivalent changes within the spirit of the invention. For example, in all the embodiments where two elements are directly connected, a circuit that does not affect the meaning of the signal can be inserted between them, such as a delay circuit, a switch circuit, and the like. For another example, the first stage switchable power supply circuit 10 is not limited to a buck, boost or reverse voltage circuit. As another example, in all the embodiments, it is assumed that the load terminal requires a fixed voltage Vout, but if the load terminal requires a variable voltage Vout, the first stage switching power supply circuit can also be adjusted through a digital or analog feedback control mechanism 10 and/or the voltage conversion ratio of the second-stage low-dropout regulator circuit 20 , such as adjusting the input of the error amplifier EA10 and/or the error amplifier EA20 through feedback signals, is also the concept of the present invention. Therefore, all equivalent changes or modifications made according to the concept and spirit of the present invention shall be included in the scope of the patent application of the present invention.

Claims (16)

1. the power supply device of a high efficiency and low noise comprises:

One suitching type power supply circuit, it is converted to an intermediate voltage with an input voltage;

One low-pressure drop voltage-stabilizing circuit, it is converted to an output voltage with this intermediate voltage, to provide load current to a load; And

Feedback control circuit, the noise filter capacity that it adjusts this low-pressure drop voltage-stabilizing circuit makes it increase with this load current.

2. the power supply device of high efficiency as claimed in claim 1 and low noise, wherein when this load current increased, this feedback control circuit improved the pressure drop between intermediate voltage and output voltage.

3. the power supply device of high efficiency as claimed in claim 2 and low noise wherein has an error amplifier in this switching power supply circuit, and this feedback control circuit exports a signal, to adjust an input of this error amplifier.

4. the power supply device of high efficiency as claimed in claim 1 and low noise, wherein when this load current increased, this feedback control circuit improved power consumption stream within this low-pressure drop voltage-stabilizing circuit.

5. the power supply device of high efficiency as claimed in claim 4 and low noise wherein has an error amplifier in this low-pressure drop voltage-stabilizing circuit, and this feedback control circuit exports a signal, to adjust the current sinking of this error amplifier.

6. the power supply device of high efficiency as claimed in claim 1 and low noise, wherein this feedback control circuit extracts signal within this low-pressure drop voltage-stabilizing circuit, and produces the modulation signal, to adjust the noise filter capacity of this low-pressure drop voltage-stabilizing circuit.

7. the power supply device of high efficiency as claimed in claim 6 and low noise, wherein this low-pressure drop voltage-stabilizing circuit comprises an error amplifier and an output stage transistor, the grid of this output stage transistor of the output of this error amplifier control, and wherein this feedback control circuit extracts signal from the grid of this output stage transistor or drain electrode or source electrode or with take up an official post both or above three.

8. the power supply device of high efficiency as claimed in claim 1 and low noise, wherein this feedback control circuit extracts signal from this load, and produces the modulation signal, to adjust the noise filter capacity of this low-pressure drop voltage-stabilizing circuit.

9. the power supply device of high efficiency as claimed in claim 8 and low noise, wherein this feedback control circuit has a bit error rate counter, is electrically connected with load and produces the bit error rate signal.

10. the method for a changing voltage comprises following steps:

One suitching type power supply circuit is provided, and it is converted to an intermediate voltage with an input voltage;

One low-pressure drop voltage-stabilizing circuit is provided, and it is converted to an output voltage with this intermediate voltage, gives a load with the supply load current; And

Adjust the noise filter capacity of this low-pressure drop voltage-stabilizing circuit, it is increased with this load current.

11. the method for changing voltage as claimed in claim 10, wherein this noise filter capacity is represented with the power rejection rate of this low-pressure drop voltage-stabilizing circuit.

12. the method for changing voltage as claimed in claim 10, wherein this step (C) comprises: make the voltage drop value or the in-fighting electric current of this low-pressure drop voltage-stabilizing circuit, increase with this load current.

13. the method for changing voltage as claimed in claim 10, wherein this step (C) comprises:

(C1) the noise filter capacity signal related of extraction and this low-pressure drop voltage-stabilizing circuit;

(C2) produce the modulation signal; And

(C3) this modulation signal is imported this switching power supply circuit, with adjust its output among between voltage.

14. the method for changing voltage as claimed in claim 10, wherein this step (C) comprises:

(C1) the noise filter capacity signal related of extraction and this low-pressure drop voltage-stabilizing circuit;

(C2) produce the modulation signal; And

(C3) this modulation signal is imported this low-pressure drop voltage-stabilizing circuit, to adjust its in-fighting electric current.

15. the method for changing voltage as claimed in claim 13, wherein this low-pressure drop voltage-stabilizing circuit comprises an error amplifier and an output stage transistor, the grid of this output stage transistor of the output of this error amplifier control, and wherein the signal in this step (C1) be the grid voltage signal of this output stage transistor or output voltage signal or the load current signal or the load abnormal signal of door source voltage signal or a drain voltage signal or this error amplifier.

16. the method for changing voltage as claimed in claim 14, wherein this low-pressure drop voltage-stabilizing circuit comprises an error amplifier and an output stage transistor, the grid of this output stage transistor of the output of this error amplifier control, and wherein the signal in this step (C1) be the grid voltage signal of this output stage transistor or output voltage signal or the load current signal or the load abnormal signal of door source voltage signal or a drain voltage signal or this error amplifier.

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