CN105137200A - Monitoring device of CCM Buck-Boost convertor output capacitor and method thereof - Google Patents

Abstract

The invention discloses a monitoring device of a CCM Buck-Boost convertor output capacitor and a method thereof. The device comprises a Buck-Boost convertor main power circuit, a driving circuit, a display unit and a signal processing module. The signal processing module comprises a power circuit control unit, a switch frequency fs calculating unit, a duty ratio D calculating unit, an output voltage trigger sampling unit, a capacitor ESR and a C calculating unit. The method is characterized in that through detecting a PWM driving pulse signal of a switch tube, a duty ratio is obtained via the duty ratio D calculating unit; a switch frequency of a convertor is obtained via the switch frequency fs calculating unit; the output voltage trigger sampling unit, on one hand, detects an output voltage average value and on the other hand triggers an instantaneous value of an output voltage acquired through sampling; the above data is sent to the capacitor ESR and the C calculating unit so as to obtain current ESR and C values of an output filtering capacitor in the Buck-Boost convertor. By using the device and the method of the invention, a current sensor is not needed, and normal work of the convertor is not influenced and a basis is provided for life prediction of the capacitor and a power supply.

Description

The monitoring device of CCM buck-boost converter output capacitance and method

Technical field

The invention belongs to the monitoring technical field in electrical energy changer, particularly the monitoring device of a kind of CCM buck (Buck-Boost) transducer output capacitance ESR and C and method.

Background technology

Due to advantages such as efficiency are high, volume is little, Switching Power Supply is applied very extensive in daily productive life.Generally speaking, in order to obtain comparatively stable output voltage, the effective filter away high frequency noise of electric capacity must be adopted.After transducer work a period of time, capacitance (the Capacitance of electric capacity, and equivalent series resistance (EquivalentSeriesResistance C), ESR) can change, compare with resistance ESR with initatial capacitance value C, when this variable quantity is larger, can think that this electric capacity lost efficacy, the inefficacy of electric capacity will cause the operation troubles of power supply and system.Step-down (Buck), boosting (Boost), buck (Buck-Boost) transducer are three kinds of switching power converters the most basic, and other transducer all can be developed by these three kinds of transducers.Wherein, CCM (ContinuousCurrentMode, continuous current mode) One Buck-Boost converter body widely uses in fields such as computer power supply, communication power supply, Aero-Space, therefore monitor ESR and C of the output filter capacitor of CCMBuck-Boost transducer, predict that its life-span is extremely important.

Chinese scholars has done certain research to the parameter monitoring of electrochemical capacitor in Switching Power Supply in recent years, mainly can be divided into two classes, is respectively off-line type and online.But using during off-line type monitoring electrochemical capacitor needs arrestment to run.Although and online monitoring need not run by arrestment, it is except can utilizing existing switching tube current detection signal except Controlled in Current Mode and Based, need to increase current sensor with the electric current such as Detection capacitance, inductance.

Summary of the invention

The object of the present invention is to provide monitoring device and the method for a kind of CCM buck-boost converter output capacitance ESR and C, can the change of capacitance C of Real-Time Monitoring equivalent series resistance ESR and electric capacity, Accurate Prediction is carried out to the life-span of electrochemical capacitor and power supply.

The technical solution realizing the object of the invention is: a kind of monitoring device of CCM buck-boost converter output capacitance, comprise One Buck-Boost converter body main power circuit, driving circuit, display unit and signal processing module, described signal processing module comprises power circuit control module, switching frequency f _scomputing unit, dutycycle D computing unit, output voltage trigger sampling unit, electric capacity ESR and C computing unit;

Described One Buck-Boost converter body main power circuit comprises input voltage source V _in, switching tube Q _b, sustained diode _b, filter inductance L, output filter capacitor and load R _l, described output filter capacitor comprises equivalent series resistance ESR and electric capacity C, wherein switching tube Q _bdrain electrode, voltage source V _inpositive pole connect, filter inductance L one end respectively with switching tube Q _bdrain electrode and sustained diode _bnegative electrode connect, the filter inductance L other end and voltage source V _innegative pole connect, sustained diode _banode respectively with one end, the load R of equivalent series resistance ESR _lone end connect, the other end of equivalent series resistance ESR is connected with one end of electric capacity C, the other end of electric capacity C and load R _lthe other end all and voltage source V _innegative pole connect, load R _ltwo ends are output voltage v _o;

The input end of described power circuit control module respectively with the voltage source V of One Buck-Boost converter body main power circuit _inwith output voltage v _oconnect, the pwm signal of power circuit control module output terminal accesses switching frequency f respectively _scomputing unit and dutycycle D computing unit, the output voltage v of One Buck-Boost converter body main power circuit _oall access output voltage with the pwm signal of power circuit control module output terminal and trigger sampling unit, switching frequency f _sthe output terminal that computing unit, dutycycle D computing unit, output voltage trigger sampling unit all accesses electric capacity ESR and C computing unit, the output terminal access display unit of electric capacity ESR and C computing unit;

The input end of described driving circuit is connected with the pwm signal of power circuit control module output terminal, the output terminal access switching tube Q of driving circuit _bgrid.

A monitoring method of CCM buck-boost converter output capacitance ESR and C, comprises the following steps:

Step 1, creates power circuit control module, switching frequency f in signal processing module _scomputing unit, dutycycle D computing unit, output voltage trigger sampling unit, electric capacity ESR and C computing unit;

Step 2, the power circuit control module of signal processing module gathers the output voltage v of One Buck-Boost converter body main power circuit _owith input voltage source V _in, obtain pwm signal and through driving circuit driving switch pipe Q _b;

Step 3, the pwm signal that power circuit control module exports sends into switching frequency f respectively _scomputing unit and dutycycle D computing unit, through switching frequency f _scomputing unit process draws the switching frequency f that transducer is current _s, draw through the process of dutycycle D computing unit the dutycycle D that transducer is current;

Step 4, the output voltage v of the pwm signal that power circuit control module exports and One Buck-Boost converter body main power circuit _osend into output voltage simultaneously and trigger sampling unit, trigger through output voltage the instantaneous value v that sampling unit process obtains output voltage _o(0), v _o(DT _s/ 2), v _o[(1+D) T _s/ 2] and the mean value V of output voltage _o; T _sfor the converter switches cycle, D is the dutycycle of transducer, v _o(0) be the instantaneous output voltage that pwm signal rising edge time is corresponding, v _o(DT _s/ 2) be the instantaneous output voltage that the mid point moment between pwm signal rising edge and negative edge is corresponding, v _o[(1+D) T _s/ 2] be instantaneous output voltage that the mid point moment between pwm signal negative edge and rising edge is corresponding;

Step 5, by the switching frequency f obtained _s, dutycycle D and output voltage instantaneous value v _o(0), v _o(DT _s/ 2), v _o[(1+D) T _s/ 2] and the mean value V of output voltage _ofeeding electric capacity ESR and C computing unit carry out overall treatment, obtain the value of the current equivalent series resistance ESR and electric capacity C of output filter capacitor in One Buck-Boost converter body;

Step 6, the value of the equivalent series resistance ESR of gained and electric capacity C is sent into display unit and is shown in real time by electric capacity ESR and C computing unit.

Compared with prior art, its remarkable advantage is in the present invention: (1) does not affect the normal work of transducer; (2) ESR and the C value of on-line monitoring electric capacity, for the life prediction of electric capacity and power supply provides foundation; (3) without the need to current sensor and auxiliary circuit Detection capacitance electric current thereof, the difficulty of parameter monitoring is reduced.

Accompanying drawing explanation

Fig. 1 is the work wave in the CCMBuck-Boost converter switches cycle.

Fig. 2 is the structural representation of the monitoring device of CCM buck-boost converter output capacitance ESR and C of the present invention.

Wherein: V _in-input voltage, I _in-input current, i _l-inductive current, i _c-capacitance current, I _o-output current, v _o-output voltage, V _o-output voltage average value, Q _b-switching tube, D _b-diode, L-inductance, C-output filter capacitor value, ESR-equivalent series impedance, R _l-load, V _gs-switching tube Q _bdriving voltage, D-dutycycle, t-time, T _s-converter switches the cycle, f _s-converter switches frequency, Δ I _l-inductive current ripple peak-to-peak value, v _eSRvoltage on-equivalent series resistance, v _cvoltage on-electric capacity.

Embodiment

Below in conjunction with drawings and the specific embodiments, further description is made to the present invention.

The present invention designs the device and method that a kind of on-line monitoring works in buck (Buck-Boost) transducer output filter capacitor ESR and C of continuous current mode pattern (ContinuousConductionMode, CCM).

1, theory deduction:

Fig. 1 is the work wave in the CCMBuck-Boost converter switches cycle.As switching tube Q _bduring conducting, diode D _bcut-off, the voltage at inductance L two ends is V _in, its inductive current i _lwith V _inthe slope of/L linearly rises.As diode D _bduring shutoff, inductive current i _lby diode D _bafterflow, now the voltage at inductance L two ends is-V _o, inductive current i _lwith V _othe slope of/L declines.Because One Buck-Boost converter body is operated in CCM pattern, therefore before switch periods terminates, inductive current i _ldo not drop to zero.Inductive current i _lmean value in a switch periods is

Inductive current i _lexpression formula is in one cycle as follows:

$i_L\left(t\right)=\left\{\begin{array}{cc}\frac{V_{in}}{L}t-\frac{V_o(1-D)}{2{\mathrm{Lf}}_s}+\frac{I_o}{1-D}& 0\&le;t<{\mathrm{DT}}_s\\ -\frac{V_o}{L}t+\frac{V_o(1+D)}{2{\mathrm{Lf}}_s}+\frac{I_o}{1-D}& {\mathrm{DT}}_s\&le;t<T_s\end{array}\right.---\left(1\right)$

Wherein V _infor input voltage, V _ofor output voltage average value, L is inductance value, f _sfor the switching frequency of One Buck-Boost converter body, D is the dutycycle of switching tube, T _sfor the switch periods of One Buck-Boost converter body, t is the time.

Capacitance current i _cexpression formula be:

$i_C\left(t\right)=\left\{\begin{array}{cc}-I_o& 0\&le;t<{\mathrm{DT}}_s\\ -\frac{V_o}{L}t+\frac{V_o(1+D)}{2{\mathrm{Lf}}_s}+\frac{I_{o}D}{1-D}& {\mathrm{DT}}_s\&le;t<T_s\end{array}\right.---\left(2\right)$

Capacitance current i _cpressure drop on electric capacity C and equivalent series resistance ESR is respectively v _c(t) and v _eSR(t), its waveform as composition graphs 1, the voltage v on equivalent series resistance ESR _eSR(t) waveform and capacitance current i _ct () waveform shape is consistent,

Its expression formula is:

$v_{ESR}\left(t\right)=ESR\&CenterDot;i_C\left(t\right)=\left\{\begin{array}{cc}-ESR\&CenterDot;I_o& 0\&le;t<{\mathrm{DT}}_s\\ ESR\&CenterDot;\&lsqb;-\frac{V_o}{L}t+\frac{V_o(1+D)}{2{\mathrm{Lf}}_s}+\frac{I_{o}D}{1-D}\&rsqb;& {\mathrm{DT}}_s\&le;t<T_s\end{array}\right.---\left(3\right)$

Capacitance voltage v _c(t) and capacitance current i _cthe relation of (t) as shown in the formula:

$v_C\left(t\right)=\left\{\begin{array}{cc}{V}_C\left(0\right)+\frac{1}{C}{\&Integral;}_0^t{i}_C\left(t\right)dt=V_C\left(0\right)-\frac{I_o}{C}t& 0\&le;t<{\mathrm{DT}}_s\\ \begin{array}{c}{V}_C\left(0\right)+\frac{1}{C}{\&Integral;}_0^{{\mathrm{DT}}_S}{i}_C\left(t\right)dt+\frac{1}{C}{\&Integral;}_{{\mathrm{DT}}_s}^t{i}_C\left(t\right)dt=V_C\left(0\right)-\frac{V_o}{2LC}{t}^2\\ +\&lsqb;\frac{V_o(1+D)}{2{\mathrm{LCf}}_s}+\frac{I_{o}D}{C(1-D)}\&rsqb;t-\frac{{\mathrm{DV}}_o}{2{{\mathrm{LCf}}_s}^2}-\frac{I_{o}D}{C(1-D)f_s}\end{array}& {\mathrm{DT}}_s\&le;t<T_s\end{array}\right.---\left(4\right)$

Wherein V _c(0) be capacitance voltage corresponding to zero moment.

Obviously, the voltage DC component on equivalent series resistance ESR is 0, i.e. v _eSRt () mean value in switch periods is 0, therefore, by the switch periods T of formula (4) at transducer _sinside average, be output voltage average value V _o, be shown below:

$\begin{array}{c}{V}_o=\frac{1}{T_s}{\&Integral;}_0^{T_s}{v}_C\left(t\right)dt\\ =\frac{1}{T_s}\{{\&Integral;}_0^{{\mathrm{DT}}_s}\&lsqb;V_C\left(0\right)-\frac{I_o}{C}t\&rsqb;dt+{\&Integral;}_{{\mathrm{DT}}_s}^{T_s}\{V_C\left(0\right)-\frac{V_o}{2LC}{t}^2+\&lsqb;\frac{V_o(1+D)}{2{\mathrm{LCf}}_s}+\frac{I_{o}D}{C(1-D)}\&rsqb;t-\frac{{\mathrm{DV}}_o}{2{{\mathrm{LCf}}_s}^2}-\frac{I_{0}D}{C(1-D)f_s}\left\}dt\right\}\\ =V_C\left(0\right)+\frac{V_o{(1-D)}^3}{12{{\mathrm{LCf}}_s}^2}-\frac{I_{o}D}{2{\mathrm{Cf}}_s}\end{array}---\left(5\right)$

Can (5) be obtained by formula:

$V_C\left(0\right)=V_o-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_s^2}+\frac{I_{o}D}{2{\mathrm{Cf}}_s}---\left(6\right)$

As can be seen from accompanying drawing 1, the voltage on electric capacity C is capacitance voltage v _c(t) and ESR voltage v _eSRthe resultant voltage of (t), this voltage and capacitance current i _c, electric capacity C, equivalent series resistance ESR etc. are relevant, in side circuit, according to the ripple current i detecting gained _c(t) and resultant voltage v _c(t)+v _eSRt the information of () instead can release electric capacity C and equivalent series resistance ESR value.For this reason, high spot reviews 0 moment, DT _s/ 2 and (1+D) T _s/ 2 three moment point.

Capacitance voltage v _c(t) and equivalent series resistance ESR voltage v _eSRt the resultant voltage of () is output voltage instantaneous value v _ot (), according to formula (3), formula (4) and formula (6), can obtain:

$\begin{array}{c}{v}_o\left(t\right)=v_{ESR}\left(t\right)+v_C\left(t\right)\\ =\left\{\begin{array}{cc}-ESR\&CenterDot;I_o-\frac{I_o}{C}t+V_o-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_s^2}+\frac{I_{o}D}{2{\mathrm{Cf}}_s}& 0\&le;t<{\mathrm{DT}}_s\\ \begin{array}{c}ESR\&CenterDot;\&lsqb;-\frac{V_o}{L}t+\frac{V_o(1+D)}{2{\mathrm{Lf}}_s}+\frac{I_{o}D}{1-D}\&rsqb;-\frac{V_o}{2LC}{t}^2+\&lsqb;\frac{V_o(1+D)}{2{\mathrm{LCf}}_s}+\frac{I_{o}D}{C(1-D)}\&rsqb;t\\ -\frac{{\mathrm{DV}}_o}{2{\mathrm{LCf}}_s^2}-\frac{I_{o}D}{C(1-D)f_s}+V_o-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_s^2}+\frac{I_{o}D}{2{\mathrm{Cf}}_s}\end{array}& {\mathrm{DT}}_s\&le;t<T_s\end{array}\right.\end{array}---\left(7\right)$

Output voltage according to formula (7) expresses formula, removes direct current mean value V _othe AC compounent of output voltage can be obtained as follows:

$\begin{array}{c}{\tilde{v}}_o\left(t\right)=v_o\left(t\right)-V_o\\ =\left\{\begin{array}{cc}-ESR\&CenterDot;I_o-\frac{I_o}{C}t-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_s^2}+\frac{I_{o}D}{2{\mathrm{Cf}}_s}& 0\&le;t<{\mathrm{DT}}_s\\ \begin{array}{c}ESR\&CenterDot;\&lsqb;-\frac{V_o}{L}t+\frac{V_o(1+D)}{2{\mathrm{Lf}}_s}+\frac{I_{o}D}{1-D}\&rsqb;-\frac{V_o}{2LC}{t}^2+\&lsqb;\frac{V_o(1+D)}{2{\mathrm{LCf}}_s}+\frac{I_{o}D}{C(1-D)}\&rsqb;t-\\ \frac{{\mathrm{DV}}_o}{2{\mathrm{LCf}}_s^2}-\frac{I_{o}D}{C(1-D)f_s}-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_s^2}+\frac{I_{o}D}{2{\mathrm{Cf}}_s}\end{array}& {\mathrm{DT}}_s\&le;t<T_s\end{array}\right.\end{array}---\left(8\right)$

0 moment, DT _s/ 2 and (1+D) T _s/ 2 moment, the AC compounent of output voltage be respectively:

${\tilde{v}}_o\left(0\right)=-ESR\&CenterDot;I_o-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_s^2}+\frac{I_{o}D}{2{\mathrm{Cf}}_s}---\left(9\right)$

${\tilde{v}}_o\left(\frac{{\mathrm{DT}}_s}{2}\right)=-ESR\&CenterDot;I_o-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_S^2}---\left(10\right)$

${\tilde{v}}_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;=ESR\&CenterDot;\frac{I_{o}D}{1-D}+\frac{V_o{(1-D)}^2}{8{\mathrm{LCf}}_s^2}-\frac{V_o{(1-D)}^3}{12{\mathrm{LCf}}_s^2}---\left(11\right)$

Can obtain according to formula (9), formula (10) and formula (11):

$\begin{array}{c}C=\frac{V_o{(1-D)}^3}{24{{\mathrm{Lf}}_s}^2\{(1-D){\tilde{v}}_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;+D{\tilde{v}}_o\left(\frac{{\mathrm{DT}}_s}{2}\right)\}}\\ =\frac{V_o{(1-D)}^3}{24{\mathrm{Lf}}_s^2\left\{(1-D)\right\{v_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;-V_o\}+D\&lsqb;v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)-V_o\&rsqb;\}}\end{array}---\left(12\right)$

$\begin{array}{c}ESR=\frac{12{\mathrm{Lf}}_{s}D\&lsqb;2(1-D){\tilde{v}}_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;+3{\tilde{v}}_o\left(\frac{{\mathrm{DT}}_s}{2}\right)\&rsqb;\&CenterDot;\&lsqb;(1-D){\tilde{v}}_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;+D{\tilde{v}}_o\left(\frac{{\mathrm{DT}}_s}{2}\right)\&rsqb;}{V_o{(1-D)}^3\&lsqb;{\tilde{v}}_o\left(0\right)-{\tilde{v}}_o\left(\frac{{\mathrm{DT}}_s}{2}\right)\&rsqb;}\\ =\frac{12{\mathrm{Lf}}_{s}D\left\{2(1-D)\right\{v_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;-V_o\}+3\&lsqb;v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)-V_o\&rsqb;\}\&CenterDot;\left\{(1-D)\right\{v_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;-V_o\}+D\&lsqb;v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)-V_o\&rsqb;\}}{V_o{(1-D)}^3\&lsqb;v_o\left(0\right)-v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)\&rsqb;}\end{array}---\left(13\right)$

In formula, ESR is the resistance of equivalent series resistance, and C is the capacitance of electric capacity, and L is inductance value, f _sfor converter switches frequency, T _sfor the converter switches cycle, V _ofor output voltage average value, D is the dutycycle of transducer, v _o(0) be the instantaneous output voltage that pwm signal rising edge time is corresponding, for the instantaneous output voltage that the mid point moment between pwm signal rising edge and negative edge is corresponding, for the instantaneous output voltage that the mid point moment between pwm signal negative edge and rising edge is corresponding.

Based on formula (12) and formula (13), the monitoring method of CCMBuck-Boost transducer output filter capacitor ESR and C can be obtained.

2, the monitoring device of CCM buck-boost converter output capacitance ESR and C of the present invention and method

Composition graphs 2, the monitoring device of CCM buck-boost converter output capacitance ESR and C of the present invention, comprise One Buck-Boost converter body main power circuit 1, driving circuit 3, display unit 8 and signal processing module, described signal processing module comprises power circuit control module 2, switching frequency f _scomputing unit 4, dutycycle D computing unit 5, output voltage trigger sampling unit 6, electric capacity ESR and C computing unit 7;

Described One Buck-Boost converter body main power circuit comprises input voltage source V _in, switching tube Q _b, sustained diode _b, filter inductance L, output filter capacitor and load R _l, described output filter capacitor comprises equivalent series resistance ESR and electric capacity C, wherein switching tube Q _bdrain electrode and voltage source V _inpositive pole connect, filter inductance L one end respectively with switching tube Q _bsource electrode and sustained diode _bnegative electrode connect, the filter inductance L other end and voltage source V _innegative pole connect, sustained diode _banode respectively with one end and the load R of equivalent series resistance ESR _lone end connect, the other end of equivalent series resistance ESR is connected with one end of electric capacity C, the other end of electric capacity C and load R _lthe other end all and voltage source V _innegative pole connect, load R _ltwo ends are output voltage V _o.

The input end of described power circuit control module 2 respectively with the voltage source V of One Buck-Boost converter body main power circuit 1 _inwith output voltage v _oconnect, the pwm signal of power circuit control module 2 output terminal accesses switching frequency f respectively _scomputing unit 4 and dutycycle D computing unit 5, the output voltage V of One Buck-Boost converter body main power circuit 1 _oall access output voltage with the pwm signal of power circuit control module 2 output terminal and trigger sampling unit 6, switching frequency f _sthe output terminal that computing unit 4, dutycycle D computing unit 5, output voltage trigger sampling unit 6 all accesses electric capacity ESR and C computing unit 7, the output terminal access display unit 8 of electric capacity ESR and C computing unit 7; The input end of described driving circuit 3 is connected with the pwm signal of power circuit control module 2 output terminal, the output terminal access switching tube Q of driving circuit 3 _bgrid.Described signal processing module is dsp chip TMS320F28335; Described display unit 8 is 1602 LCDs.

Based on the monitoring method of the monitoring device of CCM buck-boost converter output capacitance ESR and C of the present invention, comprise the following steps:

Step 1, creates power circuit control module 2, switching frequency f in signal processing module _scomputing unit 4, dutycycle D computing unit 5, output voltage trigger sampling unit 6, electric capacity ESR and electric capacity C computing unit 7;

Step 2, the power circuit control module 2 of signal processing module gathers the output voltage v of One Buck-Boost converter body main power circuit 1 _owith input voltage V _in, obtain pwm signal and through driving circuit 3 driving switch pipe Q _b;

Step 3, the pwm signal that power circuit control module 2 exports sends into switching frequency f _scomputing unit 4 and dutycycle D computing unit 5, through switching frequency f _scomputing unit 4 process draws the switching frequency f that transducer is current _s, draw through dutycycle D computing unit 5 process the dutycycle D that transducer is current;

Step 4, the output voltage v of the pwm signal that power circuit control module 2 exports and One Buck-Boost converter body main power circuit 1 _osend into output voltage simultaneously and trigger sampling unit 6, trigger through output voltage the instantaneous value v that sampling unit 6 process obtains output voltage _o(0), v _o(DT _s/ 2), v _o[(1+D) T _s/ 2] and the mean value V of output voltage _o;

Step 5, by the switching frequency f obtained _s, dutycycle D and output voltage instantaneous value v _o(0), v _o(DT _s/ 2), v _o[(1+D) T _s/ 2] and the mean value V of output voltage _ofeeding electric capacity ESR and C computing unit 7 carry out overall treatment, obtain the value of output filter capacitor capacitance present C in One Buck-Boost converter body according to formula (12), obtain the value of the current equivalent series resistance ESR of output filter capacitor in One Buck-Boost converter body according to formula (13);

Step 6, the value of the equivalent series resistance ESR of gained and electric capacity C is sent into display unit 8 and is shown in real time by electric capacity ESR and C computing unit 7.

The present invention is directed to the output filter capacitor of CCMBuck-Boost transducer, design a kind of output filter capacitor equivalent series resistance ESR of efficient stable and the on-Line Monitor Device of electric capacity C and method, the method can be monitored the parameter ESR of electric capacity and C when not affecting circuit normally works, for the life prediction of electric capacity and power supply provides foundation, and without the need to capacitance current detecting portion, convenient realization, has important actual application value.

Claims (5)

1. the monitoring device of a CCM buck-boost converter output capacitance, it is characterized in that, comprise One Buck-Boost converter body main power circuit (1), driving circuit (3), display unit (8) and signal processing module, described signal processing module comprises power circuit control module (2), switching frequency f _scomputing unit (4), dutycycle D computing unit (5), output voltage trigger sampling unit (6), electric capacity ESR and C computing unit (7);

Described One Buck-Boost converter body main power circuit (1) comprises input voltage source V _in, switching tube Q _b, sustained diode _b, filter inductance L, output filter capacitor and load R _l, described output filter capacitor comprises equivalent series resistance ESR and electric capacity C, wherein switching tube Q _bdrain electrode and voltage source V _inpositive pole connect, filter inductance L one end respectively with switching tube Q _bsource electrode, sustained diode _bnegative electrode connect, the filter inductance L other end and voltage source V _innegative pole connect, sustained diode _banode respectively with one end, the load R of equivalent series resistance ESR _lone end connect, the other end of equivalent series resistance ESR is connected with one end of electric capacity C, the other end of electric capacity C and load R _lthe other end all and voltage source V _innegative pole connect, load R _ltwo ends are output voltage v _o;

The input end of described power circuit control module (2) respectively with the voltage source V of One Buck-Boost converter body main power circuit (1) _inwith output voltage v _oconnect, the pwm signal of power circuit control module (2) output terminal accesses switching frequency f respectively _scomputing unit (4) and dutycycle D computing unit (5), the output voltage v of One Buck-Boost converter body main power circuit (1) _oall access output voltage with the pwm signal of power circuit control module (2) output terminal and trigger sampling unit (6), switching frequency f _sthe output terminal that computing unit (4), dutycycle D computing unit (5), output voltage trigger sampling unit (6) all accesses electric capacity ESR and C computing unit (7), output terminal access display unit (8) of electric capacity ESR and C computing unit (7);

The input end of described driving circuit (3) is connected with the pwm signal of power circuit control module (2) output terminal, the output terminal access switching tube Q of driving circuit (3) _bgrid.

2. the monitoring device of CCM buck-boost converter output capacitance according to claim 1, is characterized in that, described signal processing module is dsp chip TMS320F28335.

3. the monitoring device of CCM buck-boost converter output capacitance according to claim 1, is characterized in that, described display unit (8) is 1602 LCDs.

4. a monitoring method for CCM buck-boost converter output capacitance, is characterized in that, comprises the following steps:

Step 1, creates power circuit control module (2), switching frequency f in signal processing module _scomputing unit (4), dutycycle D computing unit (5), output voltage trigger sampling unit (6), electric capacity ESR and C computing unit (7);

Step 2, the power circuit control module (2) of signal processing module gathers the output voltage v of One Buck-Boost converter body main power circuit (1) _owith input voltage source V _in, obtain pwm signal and through driving circuit (3) driving switch pipe Q _b

Step 3, the pwm signal that power circuit control module (2) exports sends into switching frequency f respectively _scomputing unit (4) and dutycycle D computing unit (5), through switching frequency f _scomputing unit (4) process draws the switching frequency f that transducer is current _s, draw through dutycycle D computing unit (5) process the dutycycle D that transducer is current;

Step 4, the output voltage v of the pwm signal that power circuit control module (2) exports and One Buck-Boost converter body main power circuit (1) _osend into output voltage simultaneously and trigger sampling unit (6), trigger through output voltage the instantaneous value v that sampling unit (6) process obtains output voltage _o(0), v _o(DT _s/ 2), v _o[(1+D) T _s/ 2] and the mean value V of output voltage _o; T _sfor the converter switches cycle, D is the dutycycle of transducer, v _o(0) be the instantaneous output voltage that pwm signal rising edge time is corresponding, v _o(DT _s/ 2) be the instantaneous output voltage that the mid point moment between pwm signal rising edge and negative edge is corresponding, v _o[(1+D) T _s/ 2] be instantaneous output voltage that the mid point moment between pwm signal negative edge and rising edge is corresponding;

Step 5, by the switching frequency f obtained _s, dutycycle D and output voltage instantaneous value v _o(0), v _o(DT _s/ 2), v _o[(1+D) T _s/ 2] and the mean value V of output voltage _ofeeding electric capacity ESR and C computing unit (7) carry out overall treatment, obtain the value of the current equivalent series resistance ESR and electric capacity C of output filter capacitor in One Buck-Boost converter body;

Step 6, the value of the equivalent series resistance ESR of gained and electric capacity C is sent into display unit (8) and is shown in real time by electric capacity ESR and C computing unit (7).

5. the monitoring method of CCM buck converter output capacitance according to claim 4, is characterized in that, the formula of the computing unit of ESR and C described in step 5 (7) overall treatment is as follows:

$ESR=\frac{12{\mathrm{Lf}}_{s}D\left\{2(1-D)\right\{v_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;-V_o\}+3\&lsqb;v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)-V_o\&rsqb;\}\&CenterDot;\left\{(1-D)\right\{v_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;-V_o\}+D\&lsqb;v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)-V_o\&rsqb;\}}{V_o{(1-D)}^3\&lsqb;v_o\left(0\right)-v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)\&rsqb;}$

$C=\frac{V_o{(1-D)}^3}{24{\mathrm{Lf}}_s^2\left\{(1-D)\right\{v_o\&lsqb;\frac{(1+D)T_s}{2}\&rsqb;-V_o\}+D\&lsqb;v_o\left(\frac{{\mathrm{DT}}_s}{2}\right)-V_o\&rsqb;\}}$

In formula, ESR is the resistance of equivalent series resistance, and C is the capacitance of electric capacity, and L is inductance value, f _sfor converter switches frequency, T _sfor the converter switches cycle, V _ofor output voltage average value, D is the dutycycle of transducer, v _o(0) be the instantaneous output voltage that pwm signal rising edge time is corresponding, for the instantaneous output voltage that the mid point moment between pwm signal rising edge and negative edge is corresponding, for the instantaneous output voltage that the mid point moment between pwm signal negative edge and rising edge is corresponding.