CN201708696U - Buck converter circuit applicable to the continuous change of voltage of output power supply - Google Patents

Abstract

The utility model belongs to the technical field of electronic devices, in particular to a buck converter circuit applicable to the continuous change of the voltage of an output power supply. The input end of the circuit is a unit gain feedback amplifier formed by a dual differential input single-end output amplifier. The amplifier extracts the difference between feedback voltage and reference voltage and sends the same to a post compensator network. Compared with a positive input end which directly adds the reference voltage to the compensator network in a general DC-DC Buck converter, the buck converter circuit applicable to the continuous change of the voltage of output power supply eliminates the error introduced by a feedforward path from the positive input end of the compensator to the output, so that the output of the buck converter can accurately follow the signal amplitude, produce a voltage in continuous time and in proportion with signals and supply the same to the power supply for signal amplification and power output.

Description

A kind of output supply voltage continually varying Buck converter circuit that is applicable to

Technical field

The utility model belongs to technical field of electronic devices, is specifically related to the design that a kind of power supply output can be followed input reference voltage continually varying Buck (the step-down switching power supply of non-isolation) converter circuit.

Background technology

For improving the efficient of electronic product, in some application of power supply, need to produce and to follow signal continually varying power supply.Such as in the Shu class A amplifier A that power management and audio-frequency power amplifier are integrated, the power supply of audio frequency power amplifier is exactly the signal that changes with audio frequency.Reference voltage is directly inputted to the anode of compensator in the general DC-DC Buck converter circuit, when reference voltage changes with certain frequency, the compensator positive input terminal can make the relative input reference voltage of output of transducer that certain margin of error is arranged to the feedforward path of output, and can accurately not follow reference voltage.

The circuit that is applicable to output supply voltage continually varying Buck converter that the utility model proposes adds the unit gain feedback amplifier at reference voltage input terminal.Give the compensator network of back level by the difference of this amplifier taking-up feedback voltage and reference voltage, removed the feedforward path of compensator positive input terminal to its output, make the output of Buck converter can accurately follow the signal of variation, adapt to the design needs of supply voltage continually varying Buck converter.

Summary of the invention

The purpose of this utility model is at the application need that needs the supply voltage continuous variable, proposes a kind of circuit that is applicable to output supply voltage continually varying Buck converter.

The circuit of the Buck converter that the utility model proposes comprises the unit gain feedback amplifier, compensator, comparator, drive circuit, power switch, outer filter inductance L of sheet and capacitor C; Described unit gain feedback amplifier is imported single-ended output amplifier by two difference and is connected into, two groups of differential input ends that this pair difference is imported single output amplifier are respectively in1+, in1-and in2+, in2-, input in2+ is linked to each other by resistance R with in2-, and described amplifier output is fed back to input in2-end form the unit gain feedback, input in2+ termination common mode electrical level Vcm, input in1+ and in1-meet feedback voltage Vfb and input reference voltage Vref respectively.The negative terminal of compensator is received in the output of described amplifier, the positive termination common mode electrical level Vcm of compensator.The negative terminal of comparator is received in the output of compensator, the positive termination triangular wave clock of comparator, and the pulse width modulating signal that comparator produces is received drive circuit.The drive signal power controlling pipe MP that drive circuit produces, the grid of MN, the source termination input voltage Vg of MP pipe, the source end ground connection of MN pipe, MP, the drain terminal of MN pipe are connected together and link to each other with inductance L one end, and the inductance L other end links to each other with capacitor C and produces output voltage V o, capacitor C other end ground connection, Vo powers to external loading.Feedback resistive network Rf1, the end of Rf2 connect Vo and ground respectively, and the other end interconnects the generation feedback voltage Vfb.

The circuit of the Buck converter that the utility model proposes, input are that two difference are imported the unit gain feedback amplifier that single-ended output amplifier is connected into.Give the compensator network of back level by the difference of this amplifier taking-up feedback voltage and reference voltage, compare with the positive input terminal that in the general DC-DC Buck converter reference voltage directly is added in compensator network, removed because the compensator positive input terminal arrives the leading zero point that the feedforward path of its output is introduced, make the output of Buck converter can accurately follow the reference voltage of input, produce the continually varying supply voltage.

Description of drawings

Fig. 1 is the overall structure block diagram of the Buck converter in the utility model.

Fig. 2 imports single output amplifier for the two difference of unit gain feedback

Fig. 3 imports the circuit diagram of single output amplifier for two difference.

Fig. 4 is a compensator network.

The overall structure block diagram of Fig. 5 Buck converter during for no input amplifier.

Fig. 6 is Buck converter small-signal block diagram during for no input amplifier.

Fig. 7 is Buck converter small-signal block diagram when input amplifier is arranged.

Embodiment

Below in conjunction with accompanying drawing and example the utility model is elaborated.

As shown in Figure 1, a kind of output supply voltage continually varying Buck converter circuit that is applicable to comprises the unit gain feedback amplifier, compensator, comparator, drive circuit, power switch, outer filter inductance of sheet and electric capacity.Two groups of differential input ends that two difference are imported single output amplifier are respectively in1+, in1-and in2+, in2-, input in2+ is linked to each other by resistance R with in2-, and amplifier output is fed back to input in2-end form the unit gain feedback, input in2+ termination common mode electrical level Vcm, input in1+ and in1-meet feedback voltage Vfb and input reference voltage Vref respectively.The negative terminal of compensator is received in the output of amplifier, the positive termination common mode electrical level Vcm of compensator.The negative terminal of comparator is received in the output of compensator, the positive termination triangular wave clock of comparator, and the pulse width modulating signal that comparator produces is received drive circuit.The drive signal power controlling pipe MP that drive circuit produces, the grid of MN, the source termination input voltage Vg of MP pipe, the source end ground connection of MN pipe, MP, the drain terminal of MN pipe are connected together and link to each other with inductance L one end, and the inductance L other end links to each other with capacitor C and produces output voltage V o, capacitor C other end ground connection, Vo powers to external loading.Feedback resistive network Rf1, the end of Rf2 connect Vo and ground respectively, and the other end interconnects the generation feedback voltage Vfb.

As shown in Figure 2, feedback circuit figure for input unity gain amplifier in the utility model, two groups of differential input ends that two difference are imported single output amplifier are respectively in1+, in1-and in2+, in2-links to each other with in2-input in2+ by resistance R, and amplifier output is fed back to input in2-end formation unit feedback, in2+ termination common mode electrical level Vcm, amplifier output can be expressed as

V ₁＝(V _fb-V _ref)+V _cm

The margin of error that so just can take out feedback voltage and reference voltage is sent in the compensator.

As shown in Figure 3, import single-ended output amplifier circuit figure for two difference in the utility model.Power tube M1, M2, M3, the grid of M4 pipe are respectively four input in1-, in1+, in2-, in2+.Current source I1 one terminates to power supply Vdd, the drain terminal of another termination power tube M5 pipe, the grid of power tube M5 pipe and drain electrode is connected together and with power tube M6, M7, the grid of M8 link to each other to form current mirror, power tube M5, M6, M7, the source of M8 pipe terminates to ground.Power tube M1, the source end of M2 pipe links to each other with the drain terminal of power tube M6 pipe, power tube M3, the source end of M4 pipe links to each other power tube M1 with the drain terminal of power tube M7 pipe, the drain terminal of M3 pipe is connected together and links to each other with the drain terminal of power tube M9 pipe, the grid of power tube M9 pipe form current mirror with missing together and linking to each other with the grid of power tube M10 pipe, the drain terminal of power tube M10 pipe and power tube M2, and the drain terminal of M4 pipe is continuous, power tube M9, the source of M10 terminates to power supply Vdd.The grid of power tube M11 pipe is received the drain terminal of power tube M10 pipe, and source electrode meets Vdd, and drain electrode links to each other with M8 pipe drain terminal, and building-out capacitor C is connected between the grid and drain electrode of power tube M11 pipe, and the drain terminal of power tube M11 pipe is output.

As shown in Figure 4, be compensator network in the utility model, an end of capacitor C 1 links to each other with an end of resistance R 1 and meets feedback signal Vfb, and the other end of capacitor C 1 is received an end of resistance R 2.Resistance R 1, the other end of R2 links to each other with the negative terminal of amplifier, one end of capacitor C 2 links to each other with an end of resistance R 3 and receives the negative terminal of amplifier, the two ends that the other end of capacitor C 2 and resistance R 3 is received capacitor C 3 respectively, and the end points that capacitor C 2 links to each other with C3 connects the output of amplifier.Input reference voltage connects the anode of amplifier.

Order $Z_1=R1//(R2+\frac{1}{\mathrm{sC}1}),$ $Z_2=\frac{1}{\mathrm{sC}2}//(R3+\frac{1}{\mathrm{sC}3})$

Then $V_2=\frac{Z_2}{Z_1}(\mathrm{Vref}-\mathrm{Vfb})+\mathrm{Vref}$

If as shown in Figure 5, no input amplifier, reference voltage Vref is directly received the compensator anode, and feedback voltage Vfb connects the compensator negative terminal, the same Fig. 1 of remaining circuit annexation, then Deng Xiao Buck converter small-signal block diagram is as shown in Figure 6.

Wherein, H ₁Be the margin of error of reference voltage and feedback voltage small-signal transfer function, H to the compensator output ₂Be the small-signal transfer function of reference voltage to the compensator output, H ₃Be small-signal transfer function from the comparator negative input end to feedback signal Vfb.

H ₁＝Z ₂/Z ₁

H ₂＝1

H ₃Be comparator, drive circuit, power stage, the transfer function of filter and feedback resistive network is long-pending.

Be respectively input reference voltage, feedback voltage, the small-signal amount of output voltage.

The relation of feedback voltage and reference voltage during the derivation closed loop:

$H_3[({\hat{v}}_{\mathrm{ref}}-{\hat{v}}_{\mathrm{fb}})H_1+H_2{\hat{v}}_{\mathrm{ref}}]={\hat{v}}_{\mathrm{fb}}$

Put in order:

${\hat{v}}_{\mathrm{fb}}=\frac{H_1{H}_3+H_2{H}_3}{1+H_1{H}_3}{\hat{v}}_{\mathrm{ref}}$

${\hat{v}}_o=\frac{R_{f1}+R_{f2}}{R_{f2}}{\hat{v}}_{\mathrm{fb}}=\frac{R_{f1}+R_{f2}}{R_{f2}}\frac{H_1{H}_3+H_2{H}_3}{1+H_1{H}_3}{\hat{v}}_{\mathrm{ref}}$

Because H ₂H ₃Even the influence of item is loop gain H ₁H ₃＞＞1,

Also with

There is certain error.

Buck converter small-signal block diagram takes out owing to added the unit feedback amplifier of the single output of two difference inputs before compensator as shown in Figure 7 when adding input amplifier in the utility model

With

Difference send into the negative terminal of compensator again, removed the feedforward path transfer function H of compensator anode to its output ₂Influence, can obtain:

${\hat{v}}_{\mathrm{fb}}=\frac{H_1{H}_3}{1+H_1{H}_3}{\hat{v}}_{\mathrm{ref}}$

${\hat{v}}_o=\frac{R_{f1}+R_{f2}}{R_{f2}}{\hat{v}}_{\mathrm{fb}}=\frac{R_{f1}+R_{f2}}{R_{f2}}\frac{H_1{H}_3}{1+H_1{H}_3}{\hat{v}}_{\mathrm{ref}}$

As loop gain H ₁H ₃＞＞1,

Make the output of Buck converter can accurately follow the signal that amplifies a certain proportion of variation, adapt to the design needs of output supply voltage continually varying Buck converter.

Claims (3)

1. one kind is applicable to output supply voltage continually varying Buck converter circuit, it is characterized in that comprising the unit gain feedback amplifier, compensator, comparator, drive circuit, power switch, outer filter inductance L of sheet and capacitor C; Described unit gain feedback amplifier is imported single-ended output amplifier by two difference and is connected into, two groups of differential input ends that this pair difference is imported single output amplifier are respectively in1+, in1-and in2+, in2-, input in2+ links to each other by resistance R with in2-, and described amplifier output is fed back to input in2-form the unit gain feedback, input in2+ meets common mode electrical level Vcm, and input in1+ and in1-meet feedback voltage Vfb and input reference voltage Vref respectively; The negative terminal of compensator is received in the output of described amplifier, the positive termination common mode electrical level Vcm of compensator; The negative terminal of comparator is received in the output of compensator, the positive termination triangular wave clock of comparator, and the pulse width modulating signal that comparator produces is received drive circuit; Drive signal power controlling pipe MP that drive circuit produces and the grid of power tube MN, the source termination input voltage Vg of power tube MP, the source end ground connection of power tube MN pipe, the drain terminal of power tube MP and power tube MN is connected together and links to each other with inductance L one end; The inductance L other end links to each other with capacitor C and produces output voltage V o, capacitor C other end ground connection, and Vo powers to external loading; Feedback resistive network Rf1, the end of Rf2 connect Vo and ground respectively, and the other end interconnects the generation feedback voltage Vfb.

2. output supply voltage continually varying Buck converter circuit according to claim 1 is characterized in that: described pair of difference imported in the single-ended output amplifier circuit power tube M1, M2, M3, the grid of M4 pipe are respectively four input in1-, in1+, in2-, in2+; Current source I1 one terminates to power supply Vdd, the drain terminal of another termination power tube M5 pipe, the grid of power tube M5 pipe and drain electrode is connected together and with power tube M6, M7, the grid of M8 link to each other to form current mirror, power tube M5, M6, M7, the source of M8 pipe terminates to ground; Power tube M1, the source end of M2 pipe links to each other with the drain terminal of power tube M6 pipe, power tube M3, the source end of M4 pipe links to each other with the drain terminal of power tube M7 pipe, power tube M1, the drain terminal of M3 pipe is connected together and links to each other with the drain terminal of power tube M9 pipe, and the grid of power tube M9 pipe form current mirror with missing together and linking to each other with the grid of power tube M10 pipe; The drain terminal of power tube M10 pipe and power tube M2, the drain terminal of M4 pipe links to each other, power tube M9, the source of M10 terminates to power supply Vdd; The grid of power tube M11 pipe is received the drain terminal of power tube M10 pipe, and source electrode meets Vdd, and drain electrode links to each other with M8 pipe drain terminal, and building-out capacitor C is connected between the grid and drain electrode of power tube M11 pipe, and the drain terminal of power tube M11 pipe is output.

3. output supply voltage continually varying Buck converter circuit according to claim 1, it is characterized in that: in the described compensator, one end of capacitor C 1 links to each other with an end of resistance R 1 and meets feedback signal Vfb, and the other end of capacitor C 1 is received an end of resistance R 2; Resistance R 1, the other end of R2 links to each other with the negative terminal of amplifier, one end of capacitor C 2 links to each other with an end of resistance R 3 and receives the negative terminal of amplifier, the two ends that the other end of the other end of capacitor C 2 and resistance R 3 is received capacitor C 3 respectively, and the end points that capacitor C 2 links to each other with C3 connects the output of amplifier; Input reference voltage connects the anode of amplifier.

Images