CN201479001U - Optimized DC-DC converter and circuit - Google Patents

Abstract

The utility model provides an optimized DC-DC converter and a circuit. The optimized DC-DC converter comprises a voltage input end, a voltage output end, a power conversion unit, a control unit, a feedback resistance R1 and a feedback resistance R2, wherein the power conversion unit is arranged between the voltage input end and the voltage output end, and the control unit is used for controlling the power converter; the first end of the feedback resistance R1 is connected to the voltage output end, and the second end thereof is connected to the control unit; and one end of the feedback resistance R2 is grounded, and the other end thereof is connected to the second end of the feedback resistance R1. The converter also comprises a feedforward capacitor Cff which is connected with the feedback resistance R1 in parallel. The feedback resistance R1 is connected with the feedforward capacitor Cff in parallel, so that the response bandwidth and phase margin of the DC-DC converter are improved, and thereby, the transient response is optimized.

Description

A kind of DC-DC transducer and circuit of optimization

Technical field

The utility model relates to field of electric control, especially relates to a kind of direct voltage-direct voltage of optimizing transient response (DC-DC) transducer and circuit.

Background technology

The DC-DC transducer is exactly the power converter that certain direct voltage is converted to another kind of direct voltage, and at present, the DC-DC transducer has been widely used in the products such as mobile phone, MP3, digital camera, portable electronic device.

Be illustrated in figure 1 as the structure chart of a DC-DC transducer in the prior art, this transducer comprises voltage input end 101, voltage output end 102, pulse-width modulation (Pulse Width Modulation, PWM) controller 103, K switch 1, K2, filter inductance L, filter capacitor C4 and feedback compensation circuit 104 (shown in the frame of broken lines), wherein, PWM controller 103 has comprised internal error amplifier 105, and feedback compensation circuit 104 comprises feedback resistance R1, R2, building-out capacitor C1, C2, C3, compensating resistance R3 and R4.The operation principle of this DC-DC transducer is the logical and disconnected of the control signal control switch K1, the K2 that are sent by PWM controller 103, and gather output voltage signals by feedback compensation circuit 104 and compare with the internal reference voltage of PWM controller 103 time that thereby control switch K1, K2 are logical and break, realize the conversion of direct voltage.

The number of electronic components of this DC-DC transducer is too much, is unfavorable for large-scale production, also can increase the time of debugging simultaneously, the most important thing is, when the transient response of DC-DC transducer does not meet system requirements, can't adjust accordingly and optimize.

Regulating circuit output was to carry out the ability of respective change when the transient response of so-called DC-DC transducer referred to that this DC-DC transducer changes to load.Suppose that a certain a certain moment of DC-DC transducer is output as 3.3V/5A, this moment current break to 10A, according to the conservation of energy, uprise moment at electric current, voltage falls immediately.The function of transient response is exactly when current break, in time that requires and voltage falling amplitude, output voltage is adjusted to rated value 3.3V.Two indexs weighing transient response are voltage overshoot and recovery time, as shown in Figure 2.

Be illustrated in figure 3 as the structure chart of another kind of DC-DC transducer in the prior art, different with Fig. 1 is, this DC-DC transducer all is built into building-out capacitor C1, C2, C3, compensating resistance R3 and R4 in the PWM controller, forms a PWM controller 201 with built-in compensator.Though this DC-DC transducer has reduced the quantity of exterior electrical components, but fail to solve when the transient response of DC-DC transducer does not meet system requirements the problem that can't adjust accordingly and optimize.

Chinese patent application number is that 200680014187.4 utility application discloses the apparatus and method of a kind of compensating load electric capacity to the influence of power governor, it realizes that by increasing amplifier unit and some Resistor-Capacitor Units the specific embodiment mode sees also Fig. 4 and Fig. 5 to the adjustment and the optimization of DC-DC transducer transient response.

But above-mentioned prior art need increase many components and parts, and it realizes the circuit more complicated, thereby causes production cost to increase.

The utility model content

At above-mentioned defective, the purpose of the utility model embodiment is to provide a kind of DC-DC transducer and circuit of optimization, is used for solving method too complicated, the cost problem of higher of prior art to the adjustment and the optimization of DC-DC transducer transient response.

To achieve these goals, the utility model embodiment has proposed a kind of direct voltage-direct voltage DC-DC transducer, comprise voltage input end, voltage output end, power conversion unit, control unit, feedback resistance R1 and feedback resistance R2, described power conversion unit is arranged between described voltage input end and the described voltage output end, described control unit is used to control described power converter, first end of described feedback resistance R1 is connected to described voltage output end, its second end is connected to described control unit, described feedback resistance R2 one end ground connection, the other end connects second end of described feedback resistance R1, in addition, this transducer also comprises a feed-forward capacitance Cff, described feed-forward capacitance Cff and described feedback resistance R1 are in parallel, and described feed-forward capacitance Cff is used to improve the responsive bandwidth and the phase margin of described DC-DC transducer.

Preferably, feed-forward capacitance Cff is the adjustable variable capacitor of capacitance in the present embodiment.

Preferably, control unit is in pulse-width modulation PWM controller, the pulse wave frequency modulation(FM) PFM controller one or both in the present embodiment.

Preferably, the capacitance of feed-forward capacitance Cff satisfies following formula in the present embodiment:

$f_{\_\mathrm{noCff}}=\sqrt{\left(\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009201550018E00011.png,H2009201550018E00062.png"\; state="\{\{state\}\}">R</figure-callout>}1\&times;\mathrm{Cff}}\right)\left[\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{Cff}}(\frac{1}{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009201550018E00072.png"\; state="\{\{state\}\}">R</figure-callout>}2}+\frac{1}{R1})\right]}$

The cross-over frequency of described DC-DC transducer when wherein f_nocff is described feed-forward capacitance Cff not in parallel.

To achieve these goals, the utility model embodiment also proposes a kind of feedback circuit of DC-DC transducer, comprise voltage output end, error amplifier, feedback resistance R1, R2, first end of described feedback resistance R1 is connected to described voltage output end, its second end is connected to described error amplifier, described feedback resistance R2 one end ground connection, the other end connects second end of described feedback resistance R1, this feedback circuit also comprises a feed-forward capacitance Cff, and described feed-forward capacitance Cff and described feedback resistance R1 are in parallel.

Preferably, feed-forward capacitance Cff is the adjustable variable capacitor of capacitance in the present embodiment.

Preferably, the capacitance of feed-forward capacitance Cff satisfies following formula in the present embodiment:

$f_{\_\mathrm{noCff}}=\sqrt{\left(\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009201550018E00011.png,H2009201550018E00062.png"\; state="\{\{state\}\}">R</figure-callout>}1\&times;\mathrm{Cff}}\right)\left[\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{Cff}}(\frac{1}{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009201550018E00072.png"\; state="\{\{state\}\}">R</figure-callout>}2}+\frac{1}{R1})\right]}$

The cross-over frequency of described DC-DC transducer when wherein f_nocff is described feed-forward capacitance Cff not in parallel.

When the utility model embodiment does not meet system requirements for the transient response when the DC-DC transducer, come transducer is adjusted accordingly and optimized by means simply and easily, the inventor is feed-forward capacitance in parallel on the feedback resistance R1 of former DC-DC transducer, this feed-forward capacitance can improve the responsive bandwidth and the phase margin of DC-DC transducer, thereby optimizes the transient response of DC-DC transducer.This scheme is not only simple, and with low cost.

Description of drawings

In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is embodiment more of the present utility model, for those of ordinary skills, do not paying under the prerequisite of creating work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is the structure chart of a kind of DC-DC transducer in the prior art;

Fig. 2 is the index schematic diagram of DC-DC transducer transient response in the prior art;

Fig. 3 is the structure chart of another kind of DC-DC transducer in the prior art;

The circuit diagram that has the error amplifier of variable gain buffer in Fig. 4 prior art;

The circuit diagram that has the error amplifier of variable attenuation buffer in Fig. 5 prior art;

Responsive bandwidth and phase margin schematic diagram that Fig. 6 provides for the utility model embodiment;

The structure chart of a kind of DC-DC transducer that Fig. 7 provides for the utility model embodiment one;

Fig. 8 is the schematic diagram of a first order pole circuit and gain and phase place;

Fig. 9 is the schematic diagram of a simple zero circuit and gain and phase place;

Figure 10 is responsive bandwidth and the phase margin schematic diagram that has increased DC-DC transducer behind the feed-forward capacitance Cff;

Figure 11 is the load current and the output voltage waveform of DC-DC transducer when not increasing feed-forward capacitance Cff;

Figure 12 is the load current and the output voltage waveform of DC-DC transducer behind the increase feed-forward capacitance Cff;

The structure chart of a kind of DC-DC transducer that Figure 13 provides for the utility model embodiment two;

The circuit diagram of a kind of feedback circuit that Figure 14 provides for the utility model embodiment three.

Embodiment

In order to make the purpose of this utility model, technical scheme and advantage clearer,, the utility model is described in further details below in conjunction with embodiment and accompanying drawing.At this, exemplary embodiment of the present utility model and explanation thereof are used to explain the utility model, but not as to qualification of the present utility model.

The core of the utility model embodiment is electric capacity and DC-DC transducer internal feedback resistance R 1 are in parallel, with the responsive bandwidth and the phase margin of raising DC-DC transducer, thus the transient response of optimization DC-DC transducer.In order to understand the utility model better, below simply introduce earlier responsive bandwidth and phase margin:

Be illustrated in figure 6 as responsive bandwidth and phase margin schematic diagram that the utility model embodiment provides:

What responsive bandwidth reflected is the response speed of DC-DC transducer to the load variations of friction speed, as shown in Figure 6, frequency is more little, it is big more to gain, the frequency that also is load variations is more little, and the DC-DC transducer can very fast adjusting, and when the frequency of load variations during greater than 10K, gain is 0, and promptly the DC-DC transducer is for the not response of variation faster than 10K.

What phase margin reflected is the stability of DC-DC transducer, and enough phase margins can guarantee that the DC-DC transducer when fast-changing load is adjusted, wild effects such as concussion can not occur.Phase margin is the absolute value of the difference of phase margin and 0 °, and phase margin then is that system gain is 0 o'clock a phase value, is-45 ° such as the phase margin among Fig. 6, and phase margin then is 45 °.Studies show that to have only phase margin greater than 35 °, it is stable that system could keep.

Embodiment one

Be illustrated in figure 7 as the structure chart of a kind of DC-DC transducer that the utility model embodiment one provides.This circuit comprises voltage input end 701, voltage output end 702, power conversion unit 703, control unit 704, feedback resistance R1, feedback resistance R2 and feed-forward capacitance Cff.

Power conversion unit 703 is arranged between voltage input end 701 and the voltage output end 702, and 704 of control units are connected to power conversion unit 703; The end of feedback resistance R1 is connected to voltage output end 702, and the other end then is connected to node 705; And the end of feedback resistance R2 is connected to node 705, other end ground connection; Feed-forward capacitance Cff and feedback resistance R1 are in parallel, and draw the input that a tie-in line is connected to control unit 704 at node 705 simultaneously.

Each element is by above-mentioned connection, constituted a complete DC-DC change-over circuit, its output voltage information by the voltage divider feedback voltage output 702 that is made of feedback resistance R1 and R2 is given control unit 704, comes power controlling converting unit 703 to carry out the conversion of direct voltage by control unit 704 then.

In the present embodiment, in order to obtain better transient response, the inventor is feed-forward capacitance Cff in parallel on feedback resistance R1, and the adding of this feed-forward capacitance Cff makes the responsive bandwidth of whole DC-DC change-over circuit and phase margin be improved.

Responsive bandwidth and the phase margin how feed-forward capacitance Cff is improved a DC-DC change-over circuit is illustrated below:

At first, the notion of pole and zero under the simple declaration: components and parts simple combination such as capacitance-resistance and inductance just can be produced pole and zero, be illustrated in figure 8 as the schematic diagram of a first order pole circuit and gain and phase place.The first order pole circuit is that gain in 0 to the corner frequency fc scope is a horizontal line from frequency as seen from the figure, through descending with-per ten octaves of 20dB/ (dB/dec) behind the corner frequency fc, when being in corner frequency fc, the phase place of output signal input relatively is-45 °, and when frequency during much larger than corner frequency fc, this phase place can reach-90 °.

Be illustrated in figure 9 as the schematic diagram of a simple zero circuit and gain and phase place.The simple zero circuit is that gain in 0 to the corner frequency fc scope is a horizontal line from frequency as seen from the figure, through rising with+per ten octaves of 20dB/ (dB/dec) behind the corner frequency fc, maximum phase can reach+and 90 °.

After current feed appearance Cff and feedback resistance R1 were in parallel, itself and feedback resistance R1 had increased a zero point together, make gain curve be risen at corner frequency fz place, wherein:

$f_Z=\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009201550018E00011.png,H2009201550018E00062.png"\; state="\{\{state\}\}">R</figure-callout>}1\&times;\mathrm{Cff}}$

Simultaneously, feed-forward capacitance Cff has increased a limit with feedback resistance R1, R2 again, and it makes gain curve descend at frequency f p place, and simultaneously, it has also guaranteed enough phase margins for the DC-DC transducer, wherein:

$f_p=\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{Cff}}(\frac{1}{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009201550018E00072.png"\; state="\{\{state\}\}">R</figure-callout>}2}+\frac{1}{R1})$

Suppose the responsive bandwidth and the phase margin schematic diagram of Fig. 6 DC-DC transducer when not increasing feed-forward capacitance Cff, Figure 10 is responsive bandwidth and the phase margin schematic diagram that has increased DC-DC transducer behind the feed-forward capacitance Cff so.As shown in figure 10, line segment 1001 is to have increased the gain curve after the zero point, it is in propradation, line segment 1002 then is to have increased the trend of DC-DC transducer gain curve after the limit, when frequency arrived 15Khz, gain reduced to zero at last, as seen increased feed-forward capacitance Cff after, the responsive bandwidth of DC-DC transducer has been increased to 15Khz by original 10Khz, and promptly this DC-DC transducer can respond the load variations of faster speed.

See the phase margin figure among Figure 10 again, increased feed-forward capacitance Cff after, the phase margin of DC-DC transducer has been increased to 90 ° by original 45 °, makes the stability of DC-DC transducer of present embodiment be further enhanced.

Because the responsive bandwidth of DC-DC transducer is improved, therefore among Figure 10 greater than the load variations speed of fz, the DC-DC transducer can have shorter recovery time and littler voltage overshoot, and because the phase margin of DC-DC transducer is improved, the stability when it recovers also is further enhanced.

Illustrate that with a measured waveform figure the utility model embodiment advantage: Figure 11 is the load current and the output voltage waveform of DC-DC transducer when not increasing feed-forward capacitance Cff below, Figure 12 is the load current and the output voltage waveform of DC-DC transducer behind the increase feed-forward capacitance Cff.As seen from the figure, Δ t recovery time of transducer has dropped to 14us from 68us behind the increase feed-forward capacitance Cff, and overshoot voltage Δ v has then dropped to 377mv from 900mv, and as seen its transient response has obtained great optimization than before.In addition, behind the increase feed-forward capacitance Cff, the output voltage waveforms of DC-DC transducer is steady than before a lot, so its stability also is improved.

Certainly, the beneficial effect that obtains behind the above-mentioned adding feed-forward capacitance Cff is to be based upon on the basis of choosing suitable Cff value, in order to obtain the capacitance of suitable feed-forward capacitance Cff, the transient response of the DC-DC transducer in the time of can measuring described feed-forward capacitance Cff not in parallel, obtain the cross-over frequency f_nocff of DC-DC transducer, the acquisition of this measuring process and cross-over frequency can be finished by oscilloscope.The following formula of resistance substitution of f_nocff and feedback resistance R1 and feedback resistance R2 just then, to obtain the capacitance of feed-forward capacitance Cff:

$f_{\_\mathrm{noCff}}=\sqrt{\left(\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009201550018E00011.png,H2009201550018E00062.png"\; state="\{\{state\}\}">R</figure-callout>}1\&times;\mathrm{Cff}}\right)\left[\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{Cff}}(\frac{1}{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009201550018E00072.png"\; state="\{\{state\}\}">R</figure-callout>}2}+\frac{1}{R1})\right]}$

Embodiment two

Present embodiment is to the further specifying of embodiment one, as shown in figure 13 the structure chart of a kind of DC-DC transducer that provides for the utility model embodiment two.This DC-DC transducer comprises voltage input end 1301, voltage output end 1302, PWM controller 1303, K switch 1, K2, filter inductance L, filter capacitor C4, feedback resistance R1, feedback resistance R2 and feed-forward capacitance Cff, wherein PWM controller 1303 comprises error amplifier 1304, building-out capacitor C1, C2, C3 and compensating resistance R3, R4 again, and the annexation of its each element as shown in FIG..

K switch 1, K2, filter inductance L and filter capacitor C4 constitute the Power Conversion unit together in the present embodiment, and it is subjected to the control of PWM controller 1303.In the present embodiment, error amplifier 1304, building-out capacitor C1, C2, C3 and compensating resistance R3, R4 are built in the PWM controller 1303, and they make a control chip together, thereby have reduced the quantity of external devices, are convenient to large-scale production and debugging.

Be being connected of feedback resistance R1, feedback resistance R2 and feed-forward capacitance Cff and PWM controller 1303 that inverting input that a tie-in line is connected to error amplifiers 1304 in the PWM controller 1303 realizes by drawing from node 1305, the non-inverting input of error amplifier 1304 then connects reference voltage VREF.

As an embodiment of the present utility model, feed-forward capacitance Cff is the adjustable variable capacitance of capacitance, like this, and when the transient response of DC-DC converter does not meet the demands, can not need to change feed-forward capacitance Cff, and the capacitance of directly adjusting feed-forward capacitance Cff gets final product.

As an embodiment of the present utility model, PWM controller 1303 also can be substituted by the PFM controller, perhaps finishes controlled function together in conjunction with the PFM controller.

Embodiment three

The circuit diagram of a kind of feedback circuit that provides for the utility model embodiment three as shown in figure 14.This feedback compensation circuit comprises voltage output end 1401, error amplifier 1402, feedback resistance R1, R2 and feed-forward capacitance Cff, wherein a feedback resistance R1 and an end are connected to voltage output end, the other end is connected to the inverting input of error amplifier 1402, the non-inverting input of error amplifier 1402 then connects reference power source VREF, feedback resistance R2 one end ground connection in addition, the other end is connected to node 1403, and feed-forward capacitance Cff then is in parallel with feedback resistance R1.

The feedback circuit of present embodiment has increased a feed-forward capacitance Cff with respect to feedback circuit of the prior art, this feed-forward capacitance Cff and feedback resistance R1 have increased a zero point for the DC-DC changer system, simultaneously its again with feedback resistance R1, R2 together for the DC-DC changer system has increased a limit, thereby improved the responsive bandwidth and the phase margin of DC-DC converter.Concrete analysis can not repeat them here referring to embodiment one.

As an embodiment of the present utility model, feed-forward capacitance Cff can be the adjustable variable capacitance of capacitance, like this, and when the transient response of DC-DC converter does not meet the demands, can not need to change feed-forward capacitance Cff, and the capacitance of directly adjusting feed-forward capacitance Cff gets final product.

As an embodiment of the present utility model, for fixing system, the value of feed-forward capacitance Cff is that certain restriction is arranged, in order to obtain the capacitance of suitable feed-forward capacitance Cff, the transient response of the DC-DC transducer in the time of can measuring described feed-forward capacitance Cff not in parallel, obtain the cross-over frequency f_nocff of DC-DC transducer, the acquisition of this measuring process and cross-over frequency can be finished by oscilloscope.The following formula of resistance substitution of f_nocff and feedback resistance R1 and feedback resistance R2 just then, to obtain the capacitance of feed-forward capacitance Cff:

$f_{\_\mathrm{noCff}}=\sqrt{\left(\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009201550018E00011.png,H2009201550018E00062.png"\; state="\{\{state\}\}">R</figure-callout>}1\&times;\mathrm{Cff}}\right)\left[\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{Cff}}(\frac{1}{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009201550018E00072.png"\; state="\{\{state\}\}">R</figure-callout>}2}+\frac{1}{R1})\right]}$

Above-described embodiment; the purpose of this utility model, technical scheme and beneficial effect are further described; institute is understood that; the above only is an embodiment of the present utility model; and be not used in and limit protection range of the present utility model; all within spirit of the present utility model and principle, any modification of being made, be equal to replacement, improvement etc., all should be included within the protection range of the present utility model.

Claims (7)

1. the DC-DC transducer of an optimization, comprise voltage input end, voltage output end, power conversion unit, control unit, feedback resistance R1 and feedback resistance R2, described power conversion unit is arranged between described voltage input end and the described voltage output end, described control unit is used to control described power conversion unit, first end of described feedback resistance R1 is connected to described voltage output end, its second end is connected to described control unit, described feedback resistance R2 one end ground connection, the other end connects second end of described feedback resistance R1, it is characterized in that, also comprise a feed-forward capacitance Cff, described feed-forward capacitance Cff and described feedback resistance R1 are in parallel, and described feed-forward capacitance Cff is used to improve the responsive bandwidth and the phase margin of described DC-DC transducer.

2. the DC-DC transducer of optimization as claimed in claim 1 is characterized in that, described feed-forward capacitance Cff is the adjustable variable capacitor of capacitance.

3. the DC-DC transducer of optimization as claimed in claim 1 is characterized in that, described control unit is one or both in pulse-width modulation PWM controller, the pulse wave frequency modulation(FM) PFM controller.

4. as the DC-DC transducer of the arbitrary described optimization of claim 1 to 3, it is characterized in that the capacitance of described feed-forward capacitance Cff satisfies following formula:

$f\_\mathrm{noCff}=\sqrt{\left(\frac{1}{2\mathrm{\&pi;}\&times;R1\&times;\mathrm{Cff}}\right)\left[\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{Cff}}(\frac{1}{R2}+\frac{1}{R1})\right]}$

The cross-over frequency of described DC-DC transducer when wherein f_nocff is described feed-forward capacitance Cff not in parallel.

5. the feedback circuit of a DC-DC transducer, comprise voltage output end, error amplifier, feedback resistance R1, R2, first end of described feedback resistance R1 is connected to described voltage output end, its second end is connected to described error amplifier, described feedback resistance R2 one end ground connection, the other end connects second end of described feedback resistance R1, it is characterized in that, also comprise a feed-forward capacitance Cff, described feed-forward capacitance Cff and described feedback resistance R1 are in parallel.

6. feedback circuit as claimed in claim 5 is characterized in that, described feed-forward capacitance Cff is the adjustable variable capacitor of capacitance.

7. as claim 5 or 6 described feedback circuits, it is characterized in that the capacitance of described feed-forward capacitance Cff satisfies following formula:

$f\_\mathrm{noCff}=\sqrt{\left(\frac{1}{2\mathrm{\&pi;}\&times;R1\&times;\mathrm{Cff}}\right)\left[\frac{1}{2\mathrm{\&pi;}\&times;\mathrm{Cff}}(\frac{1}{R2}+\frac{1}{R1})\right]}$

The cross-over frequency of described DC-DC transducer when wherein f_nocff is described feed-forward capacitance Cff not in parallel.

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