Working frequency ripple wave inhibition method and device thereof for LLC converter
Technical field
The present invention relates to converter technical field, particularly, relate in particular to a kind of working frequency ripple wave inhibition method for LLC converter and device thereof.
Background technology
Power resonant converter is to take resonant circuit as basic transformation unit, while utilizing circuit generation resonance, curtage is zero passage periodically, makes switching device open or turn-off under no-voltage or zero current condition, thereby realize soft switch, reach the object that reduces switching loss.
As shown in Figure 1, it is the enforcement schematic diagram of LLC controlled resonant converter, and described LLC converter comprises: the main power conversion circuit of LLC, digital signal processor, output voltage sampling circuit, output current sample circuit and former limit isolated drive circuit.
Digital signal processor obtains the output voltage that output voltage sampling circuit provides, after digital filtering is processed, it is poor that desired value and output voltage are done, this difference is by digital PI (Proportional Integral, ratio regulates and integral adjustment) adjusting of controller, produce the digital quantity with the corresponding frequency of regulation voltage, this digital quantity is used as the periodic quantity of the inner ePWM module of digital signal processor, and digital quantity is revised the period register of corresponding ePWM module accordingly, make ePWM module generate the PFM control signal of corresponding frequencies, this PFM signal is after the isolated drive circuit of former limit, be loaded into converter switches pipe Q1, Q2, the driving signal end of Q3 and Q4, thereby control turning on and off of these switching tubes, and then make the target voltage of LLC controlled resonant converter stable output.
At present, Switching Power Supply has small-sized, light weight and feature being widely used in electronic equipment efficiently.Along with the develop rapidly of power electronic technology and the appearance of high frequency switching device, Switching Power Supply is gradually towards high frequency, integrated and modular future development, Switching Power Supply realizes the cost that Digital Control can be saved hardware circuit gradually, and its precision is higher, realize fast, and there is the advantages such as control is flexible.Known ground, improve switching frequency and can reduce device volume, the power density of raising equipment and reliability, and can reduce switching noise, controlled resonant converter is owing to realizing soft switch, thereby can effectively reduce switching loss, switching frequency is further improved, so current, in HF power conversion field, obtain paying attention to widely and studying.
Under this background, people require also more and more higher for precision and the low working frequency ripple wave of switch power source output voltage.Wherein, working frequency ripple wave is converter when carrying out AC-DC conversion, the alternating component that AC power is inevitably brought in rectifying and wave-filtering link in DC quantity.Particularly, the input voltage of converter is electric main, frequency is conventionally at 50Hz, after processing, the current rectifying and wave filtering circuit of converter conventionally contains interchange low-frequency ripple in the direct voltage of output, its frequency is two times of ac power frequency of input, and this alternating current component being superimposed upon in DC quantity is just referred to as working frequency ripple wave.
LLC controlled resonant converter prime AC-DC converter converts the alternating voltage of input to high-voltage dc voltage by rectifying and wave-filtering and PFC circuit of power factor correction, working frequency ripple wave has superposeed in this high voltage direct current output, when carrying out DCDC conversion, working frequency ripple wave is inevitably added on the output voltage of LLC converter.Working frequency ripple wave in visible LLC converter output voltage be by the rectification ripple of inputting through LLC converter and be delivered to output, wherein, the size of working frequency ripple wave depends on the capacity of rectifying and wave-filtering electric capacity and the regulating power of feedback loop.
In prior art, it for the method for the inhibition working frequency ripple wave of converter, is mainly to take the mode of filter method: the working frequency ripple wave that adds filter circuit to be mingled with filtering output voltage at power output end.Described filter circuit adopts RC filter circuit or LC filter circuit conventionally, passes through to calculate rational resistance, capacitance, sensibility reciprocal, thereby can effectively suppress to a certain extent the size of working frequency ripple wave when specific design.But due to the restriction of converter volume, the filter inductance size that LC filter circuit uses cannot be done greatly as much as possible, therefore cannot as often as possible reduce working frequency ripple wave; In addition, in concrete use, the filter capacitor of RC filter circuit is when being increased to a certain degree, and it has reduced reducing the successful of working frequency ripple wave, and the mode of this increase hardware had both increased cost simultaneously, had also increased the requirement of application space.
Therefore, how providing a kind of working frequency ripple wave inhibition method for LLC converter of taking into account design cost, small product size and complex circuit designs degree is a technical problem urgently to be resolved hurrily.
Summary of the invention
Inventor's discovery, in order effectively to suppress the secondary working frequency ripple wave on output voltage, digital PI controller should possess the ability of the disturbance of good anti-secondary working frequency ripple wave, now just requires digital PI controller to have enough gains to secondary working frequency ripple wave.And LLC controlled resonant converter is because the feature of its topological structure, system is controlled the amplitude-versus-frequency curve of lower open-loop transfer function by digital PI controller, for example, near 100Hz frequency (two frequencys multiplication of input voltage frequency), gain very little, digital PI controller can not be controlled secondary working frequency ripple wave well; And LLC controlled resonant converter output area is larger, adopt traditional control method to be difficult to, when solving working frequency ripple wave problem, can guarantee that again whole working range loop characteristics meets the demands.
Based on this, the embodiment of the present invention provides a kind of working frequency ripple wave inhibition method for LLC converter and device thereof, it adds ripple control loop back path on digital principal voltage ring PI control loop basis, in order to improve near the gain of principal voltage loop back path frequency power frequency, thereby reach the object that suppresses working frequency ripple wave.
In order to reach object of the present invention, the present invention realizes by the following technical solutions:
A kind of working frequency ripple wave inhibition method for LLC converter, wherein: using Voltage loop as master control, and increase ripple ring and control by way of compensation, wherein:
Described ripple ring: the output voltage sampling is carried out to the first digital filtering processing, by process the output voltage average value and the output voltage sampled value that obtain through described the first digital filtering, do poor first difference that obtains, and described the first difference is carried out obtaining ripple ring regulation voltage after low-pass filtering and ratio amplification processing, and obtain direct current biasing amount after described ripple ring regulation voltage being carried out to the second digital filtering processing, described ripple ring regulation voltage and this direct current biasing amount are done to the poor ripple loop voltag output signal that obtains;
Described Voltage loop: described ripple loop voltag output signal is superimposed to default output voltage benchmark, be used for improving system work band gain, and revised output voltage benchmark and the output voltage sampling are done to poor second difference that obtains, and carry out the adjusting of PI control loop according to this second difference, calculate the switching frequency of former limit power tube.
Preferably, adopt following discretization calculation expression to obtain described output voltage average value V
avg (n):
V
avg(n)=a1V
avg(n-1)+a2V
sample(n)+a2V
sample(n-1);
Wherein:
V
sample (n)represent output voltage sampled value the n time;
V
sample (n-1)represent output voltage sampled value the n-1 time;
V
avg (n)represent the output voltage average value obtaining for the n time;
V
avg (n-1)represent the output voltage average value obtaining for the n-1 time;
A1, a2 are the first digital filtering operation parameter.
Preferably, adopt following discretization calculation expression to obtain described the first difference V
delta (n):
V
delta(n)=V
avg(n)-V
sample(n)。
Preferably, adopt following discretization calculation expression to obtain ripple ring regulation voltage V
ripple:
V
ripple(n)=K1V
ripple(n-1)+K2V
delta(n)+K3V
delta(n-1);
Wherein:
V
ripple (n)the end value that represents the n time execution low-pass filtering of ripple control device and ratio amplification computing;
V
ripple (n-1)the end value that represents the n-1 time execution low-pass filtering of ripple control device and ratio amplification computing;
V
delta (n)the first difference that represents the n time output voltage average value and output voltage sampled value;
V
delta (n-1)the first difference that represents the n-1 time output voltage average value and output voltage sampled value;
K1, K2, K3 are that after Digital Discrete, ripple ring is controlled parameter.
Preferably, adopt following discretization calculation expression to obtain described direct current biasing amount V
rippleavg:
V
rippleavg(n)=b1V
rippleavg(n-1)+b2V
ripple(n)+b2V
ripple(n-1);
Wherein:
V
rippleavg (n)represent n direct current biasing amount;
V
rippleavg (n-1)represent n-1 direct current biasing amount;
B1, b2 are the second filtering operation parameter.
Preferably, adopt following discretization calculation expression to obtain ripple loop voltag output signal V
ripplepiout:
V
ripplepiout(n)=V
ripple(n)-V
rippleavg(n);
Wherein, V
ripplepiout (n)the ripple loop voltag output signal that represents n output.
Preferably, by ripple loop voltag output signal V
ripplepioutoutput voltage benchmark V is added to
setobtain revised output voltage benchmark V
refcalculation expression be:
V
ref=V
ripplepiout+V
set;
And, by revised output voltage benchmark V
refwith the output voltage V sampling
samplebe the poor second difference V that obtains
errcalculation expression be:
V
err=V
ref-V
sample。
Preferably, adopt following discretization calculation expression, and according to described the second difference V
errcarry out the adjusting of PI control loop, calculate the switching frequency digital signal V of former limit power tube
piout:
V
piout(n)=V
piout(n-1)+c2V
err(n)+c3V
err(n-1);
Wherein:
C2, c3 represents output-voltage loop Digital Discrete calculating parameter.
Preferably, after calculating the switching frequency of former limit power tube, the switching frequency calculating is carried out to upper and lower amplitude limiting processing, and give corresponding PWM register by the switching frequency assignment after amplitude limiting processing, to produce the waveform of corresponding frequencies.
A LLC convertor device, it comprises: as the Voltage loop loop of master control and the ripple loop back path of controlling as compensation, wherein:
Described ripple loop back path, for the output voltage sampling is carried out to the first digital filtering processing, by process the output voltage average value and the output voltage sampled value that obtain through described the first digital filtering, do poor first difference that obtains, and described the first difference is carried out obtaining ripple ring regulation voltage after low-pass filtering and ratio amplification processing, and obtain direct current biasing amount after described ripple ring regulation voltage being carried out to the second digital filtering processing, described ripple ring regulation voltage and this direct current biasing amount are done to the poor ripple loop voltag output signal that obtains;
Described Voltage loop loop, for described ripple loop voltag output signal is superimposed to default output voltage benchmark, be used for improving system work band gain, and revised output voltage benchmark and the output voltage sampling are done to poor second difference that obtains, and carry out the adjusting of PI control loop according to this second difference, calculate the switching frequency of former limit power tube.
A kind of working frequency ripple wave inhibition method based on numerically controlled LLC converter that the present invention proposes, by increasing system power frequency times band gain, improve the regulating power of system to power frequency section, thereby reached the beneficial effect that reduces ripple and improve output voltage quality.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of LLC converter in prior art;
The digital loop control block diagram of the working frequency ripple wave inhibition method for LLC converter that Fig. 2 provides for the embodiment of the present invention;
Fig. 3 is ripple ring algorithm structure figure in the embodiment of the present invention;
Fig. 4 calculates LLC switching frequency subroutine flow chart in the embodiment of the present invention;
Fig. 5 upgrades PWM register interrupts subroutine flow chart in the embodiment of the present invention.
The realization of the object of the invention, functional characteristics and excellent effect, be described further below in conjunction with specific embodiment and accompanying drawing.
Embodiment
Below in conjunction with the drawings and specific embodiments, technical scheme of the present invention is described in further detail, so that those skilled in the art can better understand the present invention also, can be implemented, but illustrated embodiment is not as a limitation of the invention.
Shown in figure 2, a kind of working frequency ripple wave inhibition method for LLC converter that the embodiment of the present invention provides, wherein: in digital loop control structure, using Voltage loop as master control, and increase ripple ring and control by way of compensation, wherein:
Described ripple ring: the output voltage sampling is carried out to the first digital filtering processing, by process the output voltage average value and the output voltage sampled value that obtain through described the first digital filtering, do poor first difference that obtains, and described the first difference is carried out obtaining ripple ring regulation voltage after low-pass filtering and ratio amplification processing, and obtain direct current biasing amount after described ripple ring regulation voltage being carried out to the second digital filtering processing, described ripple ring regulation voltage and this direct current biasing amount are done to the poor ripple loop voltag output signal that obtains;
Described Voltage loop: described ripple loop voltag output signal is superimposed to default output voltage benchmark, be used for improving system work band gain, and revised output voltage benchmark and the output voltage sampling are done to poor second difference that obtains, and carry out the adjusting of PI control loop according to this second difference, calculate the switching frequency of former limit power tube.
Continuation is with reference to figure 2, and wherein, Pv (s) is the transfer function of the output voltage of LLC converter to switching frequency, and to those skilled in the art, this transfer function can obtain by the method for emulation or test its model; H (s) is output voltage sampling circuit transfer function; Filter1 (s) is low-pass filter circuit transfer function, for carrying out the first digital filtering, processes, and makes output voltage sampled value with working frequency ripple wave after this filter function, becomes the output voltage average value that does not contain power frequency component; Gr (s) is ripple ring controller transfer function; Filter2 (s) is the transfer function that ripple ring controller output signal is carried out to filtering, for carrying out the second digital filtering, processes, and obtains the direct current biasing amount in ripple ring control signal; Gc (s) is the Voltage loop controller of LLC converter, can adopt traditional PI control mode, for revised output voltage benchmark and the output voltage sampling are done to poor second difference that obtains, and carry out according to this second difference the switching frequency that PI regulates the former limit of calculating power tube.
In the present embodiment, the specific works process that digital loop is controlled is as follows:
1, by ADC analog to digital converter, the analog quantity of the output voltage sampling is converted into digital quantity, in certain embodiments, can also the analog quantity of the output voltage sampling and output current be converted into digital quantity by ADC analog to digital converter.
2, output voltage fiducial value and the output voltage that samples are done poor, input signal as LLC converter master control loop-Voltage loop, through PI regulating and controlling, calculate the switching frequency of former limit power tube, and preferably, can to the switching frequency calculating, carry out upper and lower amplitude limiting processing according to system hardware parameter, prevent that the switching frequency calculating from exceeding the working range that hardware can bear.
3, on the basis of step 2, add the compensation control mode of ripple ring, increase the gain of loop power frequency section, improve the inhibition ability of closed-loop system to power-frequency voltage signal.Wherein, ripple ring structure as shown in Figure 3.
The concrete control strategy of ripple ring is as follows:
A, the output voltage V that sampling is obtained
samplecarry out digital filtering operation, eliminate power frequency fluctuation, obtain output voltage average value V
avg.In the present embodiment, to V
sampledigital filtering operation transfer function be Filter1 (s), preferably, obtain described output voltage average value V
avg (n)discretization calculation expression be:
V
avg(n)=a1V
avg(n-1)+a2V
sample(n)+a2V
sample(n-1);
Wherein:
V
sample (n)represent output voltage sampled value the n time;
V
sample (n-1)represent output voltage sampled value the n-1 time;
V
avg (n)represent the output voltage average value obtaining for the n time;
V
avg (n-1)represent the output voltage average value obtaining for the n-1 time;
A1, a2 are the first digital filtering operation parameter.
B, by output voltage average value V
avgwith output voltage sampled value V
samplecarry out subtraction, the first difference of acquisition, is exactly the alternating current component V in output voltage
delta(comprising working frequency ripple wave, each harmonic etc.).
Preferably, obtain described the first difference V
delta (n)discretization calculation expression be:
V
delta(n)=V
avg(n)-V
sample(n)。
Wherein, V
delta (n)the poor result of doing that represents the n time output voltage average value and output voltage sampled value.
C, V
deltaas the input of ripple ring controller Gr (s), through loop, calculate, obtain ripple ring regulation voltage V
ripple, wherein, it mainly carries out low-pass filtering and ratio amplification processing ripple ring controller Gr (s).
Preferably, obtain ripple ring regulation voltage V
ripplediscretization calculation expression be:
V
ripple(n)=K1V
ripple(n-1)+K2V
delta(n)+K3V
delta(n-1);
Wherein:
V
ripple (n)the end value that represents the n time execution low-pass filtering of ripple control device and ratio amplification computing;
V
ripple (n-1)the end value that represents the n-1 time execution low-pass filtering of ripple control device and ratio amplification computing;
V
delta (n)the first difference that represents the n time output voltage average value and output voltage sampled value;
V
delta (n-1)the first difference that represents the n-1 time output voltage average value and output voltage sampled value;
K1, K2, K3 are that after Digital Discrete, ripple ring is controlled parameter.
D, by the ripple ring regulation voltage V obtaining
ripple, contain direct current biasing, need carry out filtering processing to it.Processing mode is to ripple ring regulation voltage V
ripplecarry out digital filtering operation, obtaining direct current biasing amount is V
rippleavg.In the present embodiment, to V
rippledigital filtering operation transfer function be Filter2 (s).
Preferably, obtain described direct current biasing amount V
rippleavgdiscretization calculation expression be:
V
rippleavg(n)=b1V
rippleavg(n-1)+b2V
ripple(n)+b2V
ripple(n-1);
Wherein:
V
rippleavg (n)represent n direct current biasing amount;
V
rippleavg (n-1)represent n-1 direct current biasing amount;
B1, b2 are the second filtering operation parameter.
E, the ripple ring regulation voltage V that ripple ring controller is exported
ripplewith filtered direct current biasing amount V
rippleavgcarry out subtraction, obtain ripple loop voltag output signal V
ripplepioutthereby, reach the object of filtering direct current biasing.
Preferably, obtain ripple loop voltag output signal V
ripplepioutdiscretization calculation expression be:
V
ripplepiout(n)=V
ripple(n)-V
rippleavg(n);
Wherein, V
ripplepiout (n)the ripple loop voltag output signal that represents n output.
F, the ripple loop voltag output signal V that ripple ring is exported
ripplepioutoutput voltage benchmark V is added to
set, for improving system work band gain.
Preferably, by ripple loop voltag output signal V
ripplepioutoutput voltage benchmark V is added to
setobtain revised output voltage benchmark V
refcalculation expression be:
V
ref=V
ripplepiout+V
set。
4, by the output voltage benchmark V calculating in above-mentioned steps
refthe output voltage V obtaining with sampling
samplecalculate the second difference V
err.Wherein, by revised output voltage benchmark V
refwith the output voltage V sampling
samplebe the poor second difference V that obtains
errcalculation expression be:
V
err=V
ref-V
sample。
5, by error signal V
erras Voltage loop adjuster Gc (s) input, obtain digital signal V
piout.Voltage loop controller Gc (s) regulates control by error signal being carried out to suitable PI.
Preferably, adopt following discretization calculation expression, and according to described the second difference V
errcarry out the adjusting of PI control loop, calculate the switching frequency digital signal V of former limit power tube
piout:
V
piout(n)=V
piout(n-1)+c2V
err(n)+c3V
err(n-1);
Wherein:
V
err (n-1)it is the second difference calculating for the n-1 time;
V
piout (n)be that the n time Voltage loop controller regulates calculating end value;
V
piout (n-1)be that the n-1 time Voltage loop controller regulates calculating end value;
C2, c3 represents output-voltage loop Digital Discrete calculating parameter.
Compute switch frequency interruption subroutine as shown in Figure 4.
6, after calculating the switching frequency of former limit power tube, the switching frequency calculating is carried out to upper and lower amplitude limiting processing, prevent that the switching frequency calculating from exceeding the working range that hardware can bear.
7, by the switching frequency assignment after amplitude limiting processing, give corresponding PWM register, to produce the waveform of corresponding frequencies.
Particularly, the flow chart of renewal PWM register interrupts subprogram as shown in Figure 5.
Be exactly more than the step that this control method is implemented, finally by digital signal processor, improve the inhibition ability of closed-loop system to power frequency section voltage, reduce to export working frequency ripple wave.In practical application, adopt the present invention, with respect to prior art, its output voltage working frequency ripple wave is greatly improved, and its amplitude has reduced 60%~70%.
Accordingly, the embodiment of the present invention also provides a kind of LLC convertor device, and shown in figure 2, it comprises: as the Voltage loop loop of master control and the ripple loop back path of controlling as compensation, wherein:
Described ripple loop back path, for the output voltage sampling is done to carry out the first digital filtering processing, by process the output voltage average value and the output voltage sampled value that obtain through described the first digital filtering, do poor first difference that obtains, and described the first difference is carried out obtaining ripple ring regulation voltage after low-pass filtering and ratio amplification processing, and obtain direct current biasing amount after described ripple ring regulation voltage being carried out to the second digital filtering processing, described ripple ring regulation voltage and this direct current biasing amount are done to the poor ripple loop voltag output signal that obtains;
Described Voltage loop loop, for described ripple loop voltag output signal is superimposed to default output voltage benchmark, be used for improving system work band gain, and revised output voltage benchmark and the output voltage sampling are done to poor second difference that obtains, and carry out the adjusting of PI control loop according to this second difference, calculate the switching frequency of former limit power tube.
The working frequency ripple wave inhibition of specific implementation step carry out to(for) described LLC convertor device, please continue to refer to above, no longer repeats herein.
The foregoing is only the preferred embodiments of the present invention; not thereby limit the scope of the claims of the present invention; every equivalent structure or conversion of equivalent flow process that utilizes specification of the present invention and accompanying drawing content to do; or be directly or indirectly used in other relevant technical fields, be all in like manner included in scope of patent protection of the present invention.