CN103840666B - The fixing ON time controller of Switching Power Supply with inductive current slope-compensation - Google Patents

Abstract

The present invention relates to the fixing ON time controller of a kind of Switching Power Supply with inductive current slope-compensation, described Switching Power Supply includes switch mosfet pipe and filter inductance, described fixing ON time controller includes rest-set flip-flop, time delays device and comparator, described time delays device is connected with rest-set flip-flop, the outfan of described rest-set flip-flop is connected with switch mosfet pipe, the input of rest-set flip-flop is connected with the outfan of comparator, one input of described comparator is connected with the outfan of Switching Power Supply, another input connects DC offset correction circuit, described DC offset correction circuit includes subtractor, inductor current feedback bypass and reference voltage, described subtractor one end is connected with comparator, the other end connects inductor current feedback bypass and reference voltage respectively.Compared with prior art, the present invention has the advantages such as the accurate control that can realize output voltage.

Description

The fixing ON time controller of Switching Power Supply with inductive current slope-compensation

Technical field

The present invention relates to a kind of Switching Power Supply, especially relate to the fixing ON time controller of a kind of Switching Power Supply with inductive current slope-compensation.

Background technology

Along with developing rapidly of mobile equipment, DC-to-dc chopper and Switching Power Supply as they power-supply management systems must are fulfilled for techniques below demand: (1) output voltage is low；(2) output voltage precision is high；(3) volume is little；(4), during output loading transition, the transient overshoot of output voltage is little.Stable state and the dynamic characteristic of Switching Power Supply are proposed higher requirement by above demand, and the control method of Switching Power Supply is proposed new challenge.Wherein, traditional fixing ON time control method meets the basic demand of stability, dynamic property and simplicity due to it, and is widely used in Switching Power Supply, and traditional fixing ON time controller is as shown in Figure 1.But, this control method has one disadvantage in that to be exactly there is DC offset problem, due to some electronic equipment, such as computer, the required precision of power supply is high, and the characteristic controlled due to fixing ON time, output voltage is naturally larger than reference voltage, thus necessarily causes existing between the meansigma methods of output voltage and reference voltage direct current biasing.Therefore, traditional fixing ON time control method is difficult to meet output voltage high precision technology index.

Summary of the invention

Defect that the purpose of the present invention is contemplated to overcome above-mentioned prior art to exist and provide a kind of Switching Power Supply with inductive current slope-compensation to fix ON time controller.

The purpose of the present invention can be achieved through the following technical solutions:

A kind of Switching Power Supply with inductive current slope-compensation fixes ON time controller, described Switching Power Supply includes switch mosfet pipe and filter inductance, described fixing ON time controller includes rest-set flip-flop, time delays device and comparator, described time delays device is connected with rest-set flip-flop, the outfan of described rest-set flip-flop is connected with switch mosfet pipe, the input of rest-set flip-flop is connected with the outfan of comparator, one input of described comparator is connected with the outfan of Switching Power Supply, another input connects DC offset correction circuit, described DC offset correction circuit includes subtractor, inductor current feedback bypass and reference voltage, described subtractor one end is connected with comparator, the other end connects inductor current feedback bypass and reference voltage respectively.

Described inductor current feedback bypass includes the differentiator, proportioner and the absolute calculators that are sequentially connected with, and described differentiator is connected with filter inductance, and described absolute calculators is connected with subtractor.

Compared with prior art, the method have the advantages that

1) digital processing chip is only needed just can to obtain the compensation dosage needed, DC-offset correction, thus realizing the accurate control of output voltage；

2) owing to feedback branch simply changes reference voltage, it still is able to the advantage keeping traditional output voltage.

Accompanying drawing explanation

Fig. 1 is traditional fixing ON time control principle drawing；

Fig. 2 is the structural representation of the present invention；

Fig. 3 is the steady state output voltage waveform of traditional control circuit；

Fig. 4 is the steady state output voltage waveform of the present invention；

Fig. 5 is traditional control circuit stable state Output simulation waveform；

Fig. 6 is the stable state Output simulation waveform of the present invention；

Fig. 7 is traditional and the present invention load current Io transient response curve when rising to (jump and drop) a times.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.The present embodiment is carried out premised on technical solution of the present invention, gives detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

As in figure 2 it is shown, the fixing ON time controller of a kind of Switching Power Supply with inductive current slope-compensation, described Switching Power Supply includes the equivalent series resistance r of switch mosfet pipe S, Power Diode Pumped D, filter inductance L, filter capacitor C, filter capacitor_ESRWith load R, filter inductance electric current is i_L, filter capacitor voltage is v_c, the voltage of equivalent series resistance is v_ESR, load current is i_o；nullDescribed fixing ON time controller includes rest-set flip-flop 1、Time delays device 2 and comparator 3，Described time delays device 2 is connected with rest-set flip-flop 1，The outfan of described rest-set flip-flop 1 is connected with switch mosfet pipe S，The input of rest-set flip-flop 1 is connected with the outfan of comparator 3，3 one inputs of described comparator are connected with the outfan of Switching Power Supply，Another input connects DC offset correction circuit 4，Described DC offset correction circuit 4 includes subtractor、Inductor current feedback bypass and reference voltage，Described subtractor one end is connected with comparator，The other end connects inductor current feedback bypass and reference voltage respectively，Described inductor current feedback bypass includes the differentiator being sequentially connected with、Proportioner and absolute calculators，Described differentiator is connected with filter inductance，Described absolute calculators is connected with subtractor.

The average output voltage of traditional fixing ON time controller is:

$V_{\mathrm{oDC}\_\mathrm{con}}=V_{\mathrm{ref}}+\frac{1}{2}{T}_{\mathrm{on}}{r}_{\mathrm{ESR}}\frac{V_{\mathrm{in}}-V_{\mathrm{oDC}\_\mathrm{con}}}{L}---\left(1\right)$

The average output voltage of the fixing ON time controller of the present invention is:

$V_{\mathrm{oDC}\_\mathrm{pro}}=V_{\mathrm{ref}}-k\frac{V_{\mathrm{oDC}\_\mathrm{pro}}}{L}+\frac{1}{2}{T}_{\mathrm{on}}{r}_{\mathrm{ESR}}\frac{V_{\mathrm{in}}-V_{\mathrm{oDC}\_\mathrm{pro}}}{L}---\left(2\right)$

Wherein,

$k=\frac{1}{2}{T}_{\mathrm{on}}{r}_{\mathrm{ESR}}\frac{V_{\mathrm{in}}-V_{\mathrm{oDC}\_\mathrm{pro}}}{V_{\mathrm{oDC}\_\mathrm{pro}}}=\frac{1}{2}{T}_{\mathrm{on}}{r}_{\mathrm{ESR}}\frac{V_{\mathrm{in}}-V_{\mathrm{ref}}}{V_{\mathrm{ref}}}---\left(3\right)$

In formula, T_onFor fixing ON time, T_offFor switch OFF time, T_sFor switch periods.

Equivalent series resistance r when filter capacitor_ESRTime bigger, the ripple of output voltage is mainly by r_ESRRipple determine, and the ripple of capacitance voltage is negligible.

Average output voltage V is controlled by traditional fixing ON time_{oDC_con}Formula is it can be seen that traditional average output voltage V_{oDC_con}With the reference voltage V wanted_refBetween there is direct current biasing amount 1/2T_onr_ESR(V_in-V_oDC_{_con})/L, the principle controlled according to fixing ON time is it can be seen that the minima of output voltage waveforms of this control method is reference voltage, so that average output voltage is equal to the reference voltage V wanted_ref, it is possible to obtaining relatively small actual reference voltage by compensating, making the waveform of output voltage move down certain compensation dosage, thus reaching the purpose of DC-offset correction.And (the V in direct current biasing amount_in-V_{oD_}C_con)/L is precisely the slope that inductive current rises, it can thus be appreciated that by reference voltage V to wanting of the slope of inductive current_refCompensate, thus obtaining new control circuit.

The present invention is based on the equivalent series resistance r of filter capacitor_ESRWhen bigger, first obtain the expression formula of the direct current biasing amount that traditional fixing ON time controls, according to this expression formula, bypassed by the inductor current feedback of the present invention, make inductive current successively through differential, ratio and absolute value link, feed back to the reference voltage V wanted_refThe actual reference voltage V that upper formation is new_ref-new, and the new actual reference voltage Vr formed_ef-newLess than the reference voltage V wanted_ref, so that average output voltage can be equal to the reference voltage V wanted_ref。

In the present invention, by the reference voltage V wanted_refAfter compensating, forming new reference voltage, this compensation way simply changes reference voltage, thus having reached the purpose of DC-offset correction, is still able to the advantage keeping traditional fixing ON time control method simultaneously.

The curve comparative result that traditional fixing ON time controller and the present invention obtain is such as shown in Fig. 3～Fig. 7.In Fig. 3～Fig. 7, v_{o_con}: traditional fixing ON time controls output voltage；v_{o_pro}: output voltage of the present invention: V_{oDC_con}: traditional fixing ON time controls average output voltage；V_{oDC_pro}: average output voltage of the present invention；i_{o_con}Load current, i is controlled for traditional fixing ON time_{o_pro}For being with the fixing ON time of balanced control to control load current.

Claims (1)

1. null1. the fixing ON time controller of the Switching Power Supply with inductive current slope-compensation，Described Switching Power Supply includes switch mosfet pipe and filter inductance，Described fixing ON time controller includes rest-set flip-flop、Time delays device and comparator，Described time delays device is connected with rest-set flip-flop，The outfan of described rest-set flip-flop is connected with switch mosfet pipe，The input of rest-set flip-flop is connected with the outfan of comparator，It is characterized in that，One input of described comparator is connected with the outfan of Switching Power Supply，Another input connects DC offset correction circuit，Described DC offset correction circuit includes subtractor、Inductor current feedback bypass and reference voltage，Described subtractor one end is connected with comparator，The other end connects inductor current feedback bypass and reference voltage respectively，Described inductor current feedback bypass includes the differentiator being sequentially connected with、Proportioner and absolute calculators，Described differentiator is connected with filter inductance，Described absolute calculators is connected with subtractor.