CN114710036A

CN114710036A - High-efficiency boost converter for small UPS and control method thereof

Info

Publication number: CN114710036A
Application number: CN202210238988.XA
Authority: CN
Inventors: 秦岭; 刘宇涵; 许兴; 饶家齐; 周磊; 段冰莹; 钱天泓; 田民; 钱娇
Original assignee: Nantong University
Current assignee: Nantong University
Priority date: 2022-03-11
Filing date: 2022-03-11
Publication date: 2022-07-05

Abstract

The invention belongs to the technical field of DC-DC boost converters, and discloses a high-efficiency boost converter for a small UPS and a control method thereof, wherein the converter has continuous input current and small current ripple, and the service life of a storage battery cannot be influenced; the voltage gain is higher, and the lower storage battery voltage can be raised to the higher load voltage under the condition of lower duty ratio; the number of the power devices is small, the voltage stress is low, the low-rated-voltage power devices with lower price and better performance can be adopted, and the cost is lower. By adopting the control method, the boost converter can realize soft switching in the whole load variation range, further reduce the on-state loss, ensure the high operation efficiency of the small UPS and have simpler realization method.

Description

High-efficiency boost converter for small UPS and control method thereof

Technical Field

The invention belongs to the technical field of DC-DC boost converters, and particularly relates to a high-efficiency boost converter for a small UPS and a control method thereof.

Background

In a small-sized light-weight Uninterruptible Power Supply (UPS), a DC/DC converter generally uses a small number of large-capacity storage batteries connected in series as an input DC voltage source, and thus, the battery voltage of the UPS is low, while the inverter of the UPS requires a high DC input voltage. Generally, such a small UPS uses a Push-Pull circuit (Push-Pull) to realize a high dc voltage for the operation of the subsequent inverter, but the Push-Pull circuit is relatively complex in design and high in cost. The primary current is intermittent, so that the current ripple is large, the storage battery can be seriously heated, and the service life of the storage battery is influenced; 2 switching tubes are adopted, and the circuit loss is large due to the input of low-voltage large current; the step-up transformer used to realize the high step-up ratio generates leakage inductance, thereby bringing loss, and a filter inductor is used for the secondary side. Obviously, the circuit cost of this solution is also high.

In order to solve the above problems, researchers have proposed various high-gain transformerless dc converters. Compared with a push-pull circuit, the transformerless high-gain converter has the advantages of no high-frequency transformer, small volume, low cost, high efficiency and the like, and is particularly suitable for a small UPS. When the duty ratio D of the traditional Boost converter exceeds 0.8, the current stress and the on-state loss of an inductor and a switching tube of the traditional Boost converter are seriously increased, and the conversion efficiency is obviously reduced. Therefore, the voltage gain G of a conventional Boost converter does not generally exceed 5. Various scholars introduce Boost networks such as a switch inductor, a switch capacitor, a quasi-Z source or a Boost and the like into a traditional Boost converter respectively to obtain various transformer-free high-gain Boost schemes. Most of the schemes can realize single-stage conversion of energy, the conversion efficiency is high, but the voltage gain is usually not more than twice of that of the traditional Boost converter. To this end, scholars further propose high gain schemes based on boost network expansion. Although the scheme of adopting the extended boost network can obviously improve the boost capability, the volume and the weight of the converter are obviously increased due to the increase of the number of the energy storage elements. The switching frequency of the converter is improved, the volume and the weight of the energy storage element can be effectively reduced, the power density is improved, the switching loss of the power tube is also increased rapidly, and the conversion efficiency is reduced seriously. The introduction of soft switching technology can effectively solve these problems. To this end, researchers have further proposed many ZVS high-gain converters based on boost network extensions. However, these topologies have the following problems in common: (1) the number of diodes is large, and the structure is complex; (2) part of the switch tubes still work in a hard switch state, so that the efficiency is difficult to further improve; (3) the voltage stress of the switching tube is high, and a high-voltage-resistant semiconductor device is needed, so that the on-state loss is high, and the cost is high; (4) there is a loss of duty cycle.

Disclosure of Invention

In view of the above, the present invention provides a high efficiency boost converter for a small UPS and a control method thereof, where the converter has continuous input current, small current ripple, no influence on the service life of a battery, and a high voltage gain, and can boost a low battery voltage to a high load voltage under a low duty ratio condition, the number of power devices is small, the voltage stress is low, and a low rated voltage power device with low price and better performance can be used.

In order to achieve the above object, the following solutions are proposed:

a control method for a high efficiency boost converter of a small UPS, two ports of the high efficiency boost converter being connected to a battery and a load, respectively, the high efficiency boost converter comprising:

first switch tube S₁A second switch tube S₂A first capacitor C₁A second capacitor C₂The third electricityContainer C₃A fourth capacitor C₄A fifth capacitor C₅A first diode D₁A second diode D₂A first inductor L₁A second inductor L₂And a third inductance L₃；

The positive electrode of the storage battery and the first inductor L₁Is connected with the first end of the first connecting pipe; the first inductor L₁And the second end of the first switch tube S₁Drain electrode of (1), the second switching tube S₂Source electrode of, the second capacitor C₂The second terminal of (C), the third capacitor C₃Is connected with the second end of the first end; the second switch tube S₂And the second inductor L₂First terminal of, said first capacitor C₁Is connected with the first end of the first connecting pipe; the second inductor L₂And the second terminal of the second capacitor C₂First terminal of, the first diode D₁The anode of (2) is connected; the first diode D₁And the third inductor L₃First terminal of, the fourth capacitance C₄Is connected with the first end of the first connecting pipe; the third inductor L₃And the second terminal of the third capacitor C₃The first terminal of the second diode D₂The anode of (2) is connected; the second diode D₂And the fifth capacitor C₅The first end of (a) is connected to the positive pole of the load; the negative pole of the load, the negative pole of the storage battery and the first switch tube S₁Source electrode of, the first capacitor C₁Second terminal of, the fourth capacitance C₄Second terminal of, the fifth capacitance C₅Is connected with the second end of the first end;

the control method comprises the following steps:

s1, sampling value u of output voltage of high-efficiency boost converter_oAnd a reference value u_o,refComparing to obtain an error signal u_o,e；

S2, the error signal u is processed_o,eSending to an output voltage controller to obtain a regulation signal u_r；

S3, obtaining an output current sampling value i of the high-efficiency boost converter_oAdjusted according to the following rulesSwitching frequency f_s：

Wherein, Δ I ═ I_L2,peak-i_L3,peak-i_L1,val，U_inIs the input voltage; l is₁A first inductor; l is₃A third inductor; u shape_oIs the output voltage; i is_o,maxIs the maximum value of the output average current; Δ I is the current margin, I_L1,valIs a first inductor current i_L1Trough value of (a) — i_L2,peakAnd-i_L3,peakAre respectively a second inductance L₂And a third inductance L₃The reverse current peak of (2).

S4, adjusting the signal u_rAnd a switching frequency of f_sUnipolar triangular carrier u_cCrossing to generate a first switch tube S₁Drive signal u of_gs,S1(ii) a U is to be_gs,S1Negation is performed to generate a second switch tube S₂Drive signal u of_gs,S2。

Further, the first inductor L₁A second inductor L₂A third inductor L₃The design of (2) is as follows:

wherein D is a first switch tube S₁Duty cycle of the drive signal; delta% is the first inductance L₁Allowable maximum current ripple and first inductor L₁A percentage of maximum average current; p_o,maxIs the maximum value of the output power; f. of_s,minThe lowest switching frequency.

Compared with the prior art, the high-efficiency boost converter for the small UPS and the control method thereof provided by the invention can enable the storage battery to have smaller output current ripple without influencing the service life of the storage battery, can ensure that the UPS system has higher operation efficiency in the whole load change range, and has the advantages of simpler implementation method and lower cost.

Drawings

FIG. 1 is a schematic diagram of a high efficiency boost converter for a small UPS according to the present invention;

FIG. 2 is a block diagram of a system control strategy for a high efficiency boost converter for a small UPS in accordance with the present invention;

FIG. 3 is a diagram illustrating a modal analysis of a high efficiency boost converter for a small UPS in accordance with the present invention;

FIG. 4 is a waveform diagram illustrating steady-state performance testing of a high efficiency boost converter for a small UPS in accordance with the present invention;

FIG. 5 shows an embodiment of the first inductor L when the output power of the high efficiency boost converter for a small UPS is switched from a heavy load (250W) to a light load (40W)₁Current i of_L1A second inductor L₂Reverse current-i of_L2And an output voltage u_oThe experimental waveform of (2);

FIG. 6 shows a high efficiency boost converter for a small UPS employing conventional PWM control scheme (f) according to an embodiment of the present invention_s110kHz) and the control method proposed by the present invention, the measured efficiency curves under different load conditions.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 shows a high efficiency boost converter for a small UPS according to the present invention. The method comprises the following steps: first switch tube S₁A second switch tube S₂A first capacitor C₁A second capacitor C₂A third capacitor C₃A fourth capacitor C₄A fifth capacitor C₅A first diode D₁A second diode D₂A first inductor L₁A second inductor L₂And a third inductance L₃(ii) a The positive electrode of the storage battery and the first inductor L₁Is connected with the first end of the first connecting pipe; the first inductor L₁And the second end of the first switch tube S₁Drain electrode of (1), the second switching tube S₂Source electrode of, the second capacitor C₂The second terminal of (C), the third capacitor C₃Is connected with the second end of the first end; the second switch tube S₂And the second inductor L₂First terminal of, said first capacitor C₁Is connected with the first end of the first connecting pipe; the second inductor L₂And the second terminal of the second capacitor C₂First terminal of, the first diode D₁The anode of (2) is connected; the first diode D₁And the third inductor L₃First terminal of, the fourth capacitance C₄Is connected with the first end of the first connecting pipe; the third inductance L₃And the second terminal of the third capacitor C₃The first terminal of the second diode D₂The anode of (2) is connected; the second diode D₂And the fifth capacitor C₅The first end of (a) is connected to the positive pole of the load; the negative pole of the load, the negative pole of the storage battery and the first switch tube S₁Source electrode of, the first capacitor C₁Second terminal of, the fourth capacitance C₄Second end of, saidFifth capacitor C₅Is connected to the second end of the first housing.

According to fig. 2, the control strategy diagram comprises a voltage control branch, a frequency control branch and a modulation unit, and the voltage control branch and the frequency control branch are connected to the modulation unit; the voltage control branch circuit is used for obtaining the output voltage u of the load_oGenerating a voltage control signal to realize constant voltage control of the load; the frequency control branch circuit is used for acquiring the output current i of the load_oAnd generating a frequency control signal to adjust the switching frequency when the load changes.

The method comprises the following steps:

s1, sampling value u of output voltage_oAnd a reference value u_o,refComparing to obtain an error signal u_o,e；

S3, obtaining an output current sampling value i_oSelecting the following switching frequency f according to the switching frequency table_s；

TABLE 1 switching frequency table

i_o/I_o,max	∈[0,0.2]	∈(0.2,0.4]	∈(0.4,0.6]	∈(0.6,0.8]	∈(0.8,1]
						f_s	f_s1	f_s2	f_s3	f_s4	f_s,min

S4, adjusting the signal u_rAnd a switching frequency of f_sUnipolar triangular carrier u_cCrossing to generate a first switch tube S₁Drive signal u of_gs,S1(ii) a Will u_gs,S1Negation is performed to generate a second switch tube S₂Drive signal u of_gs,S2。

The operation of a high efficiency boost converter for a small UPS shown in fig. 1 is described below.

To simplify the analysis, the following assumptions were made: first switch tube S₁A second switch tube S₂A first diode D₁A second diode D₂A first capacitor C₁A second capacitor C₂A third capacitor C₃A fourth capacitor C₄A fifth capacitor C₅A first inductor L₁A second inductor L₂A third inductor L₃Are all ideal devices; a first capacitor C₁A second capacitor C₂A third capacitor C₃A fourth capacitor C₄A fifth capacitor C₅Large enough that voltage ripple is negligible; first switch tube S₁A second switch tube S₂Respectively of body diodes D_S1、D_S2。

Based on the above assumptions, the waveform of the high-efficiency boost converter for the small UPS in one switching cycle can be divided into 4 modes after the steady state is entered. Equivalent circuit diagrams of the respective modes are shown in fig. 3(a) - (d), respectively.

t₀Before the moment, the first switch tube S₁Body diode D of_S1The freewheeling has been turned on.

(1) Mode 1, t₀～t₁Stage (2): (the equivalent circuit is shown in FIG. 3 (a))

t₀At the moment, the first switch tube S is switched on by zero voltage₁Body diode D thereof_S1And naturally shutting down. In this mode, the second switch tube S₂A first diode D₁A second diode D₂Are all reverse biased; first inductance L₁A second inductor L₂A third inductor L₃Are all subjected to forward voltage; first inductor current i_L1Linearly increasing, second inductance L₂A third inductor L₃The current of (a) is linearly decreased to zero in the reverse direction and then linearly increased in the forward direction. At this time, there are:

wherein, U_C1、U_C2、U_C3And U_C4Are respectively a first capacitor C₁A second capacitor C₂A third capacitor C₃A fourth capacitor C₄Terminal voltage of U_inIs an input voltage, L₂Is a second inductor.

(2) Mode 2, t₁～t₂Stage (2): (the equivalent circuit is shown in FIG. 3 (b))

t₁At all times, the first switch tube S is turned off₁ Modality 2 begins. In the first switch tube S₁At the moment of turn-off, the first inductance L₁A second inductor L₂A third inductor L₃All the current of (2) flows into the node m to force the second switch tube S₂Body diode D of_S2Conducting follow current; at the same time, the first diode D₁A second diode D₂Are all forward biased; first inductance L₁A second inductor L₂A third inductor L₃Are subjected to reverse voltage, and the current of the current is linearly reduced in the forward direction. At this time, there are:

(3) mode 3, t₂～t₃Stage (2): (the equivalent circuit is shown in FIG. 3 (c))

t₂At the moment, the second switch tube S is switched on at zero voltage₂Body diode D thereof_S2Naturally off, modality 3 begins. In this mode, the first inductor current i_L1Continue to decrease linearly in the forward direction, and the second inductance L₂A third inductor L₃Is decreased to zero and then increased linearly in the reverse direction. The current expression is the same as that of the formula (2).

(4) Mode 4, t₃～t₄Stage (2): (the equivalent circuit is shown in FIG. 3 (d))

t₃At the moment, the second switch tube S is turned off₂Modality 4 begins. First inductor current i_L1Flows into node m; second inductance L₂A third inductor L₃Is flowing out of the node m, the first switch tube S₁Body diode D of_S1Conducting the follow current. First inductance L₁A second inductor L₂And a third inductance L₃The current expression of (c) is similar to that of equation (1). t is t₄At the moment, the first switch tube S is switched on by zero voltage₁And entering the next switching period.

Neglecting dead time, according to the volt-second balance of each inductor, the following can be obtained:

further, from fig. 3(c), it can be obtained:

according to equations (3) to (4), the voltage gain of a high-efficiency boost converter for a small UPS according to the present invention can be obtained:

it can be seen that when the duty ratio D is 0.8, the voltage gain G is 13, which is more than 2 times of the voltage gain of the conventional Boost converter, indicating that the high-efficiency Boost converter for the small UPS provided by the present invention has an extremely strong boosting capability, and therefore, the low terminal voltage of the battery can be boosted to the high load voltage with a low duty ratio.

In addition, as can be seen from the modal analysis, the first switch tube S of the high efficiency boost converter for the small UPS of the present invention₁A second switch tube S₂A first diode D₁And a second diode D₂The voltage stress of (a) is:

wherein, U_S1Is a first switch tube S₁Subject to voltage stress, U_S2Is a second switch tube S₂Withstand voltage stress, U_D1Is a first diode D₁Withstand voltage stress, U_D2Is a second diode D₂Withstand voltage stress.

It can be seen that the first switching tube S₁A second switch tube S₂A first diode D₁And a second diode D₂Has the same voltage stress of about 1/3 of the output voltage, so that a power device with low rated voltage can be adopted. Because the price of the power device with low rated voltage is relatively low, and the on-state resistance or the forward conduction voltage drop is lower, the cost and the on-state loss are correspondingly smaller.

A first capacitor C₁A second capacitor C₂A third capacitor C₃A fourth capacitor C₄A fifth capacitor C₅The voltage stress of (a) is:

U_C5＝U_o (11)

wherein, U_C5Is a fifth capacitance C₅The terminal voltage of (c).

First inductance L₁A second inductor L₂And a third inductance L₃The effective values of the currents are respectively:

wherein, I_L1,rms、I_L2,rms、I_L3,rmsAre respectively a first inductance L₁A second inductor L₂A third inductor L₃An effective value of current of; i is_L1、I_L2Are respectively a first inductance L₁A second inductor L₂Average value of current of (a); delta I_L1、ΔI_L2Are respectively a first inductance L₁A second inductor L₂Current peak to peak value.

First switch tube S₁And a second switching tube S₂The effective values of the currents are respectively:

wherein, I_S1,rms、I_S2,rmsAre respectively a first switch tube S₁A second switch tube S₂Effective value of current of_oTo output a current.

In order to ensure that one of the devices shown in FIG. 1 is usedThe high efficiency boost converter of the small UPS realizes Zero Voltage Switching (ZVS), and needs to make the first inductor L₁Operating in current-continuous mode, second inductor L₂And a third inductance L₃All work in the current bidirectional circulation mode, and can satisfy under the maximum load condition: -i_L2,peak-i_L3,peak-i_L1,val>0. Therefore, the invention provides a first inductor L₁A second inductor L₂And a third inductance L₃The design method of (1):

the first inductor L₁A second inductor L₂And a third inductance L₃The forward voltage experienced is:

in the formula of U_L1Is a first inductance L₁A terminal voltage; u shape_L2Is a second inductance L₂A terminal voltage; u shape_L3Is a third inductance L₃And (4) terminal voltage.

The first inductor L₁A second inductor L₂And a third inductance L₃The current peak-to-peak value of (a) is:

in the formula,. DELTA.I_L3Is a third inductance L₃Current peak-to-peak value of, T_sIs a switching cycle.

Soft switching current conditions:

ΔI_L1+ΔI_L2+ΔI_L3≥2(I_L1+I_L2+I_L3) (16)

in the formula I_L3Is a third inductance L₃Average value of the current of (2).

Finishing to obtain:

in the formula I_inIs the average value of the input current.

Generally speaking, the first inductance L of the Boost-type converter₁May be in terms of current peak-to-peak value Δ I_L1Not exceeding its maximum average current I_L1,maxIs designed, where δ% is 30%. At this time, there are:

in order to reliably realize soft switching in the whole operating condition range, the formula (17) needs to be ensured at the maximum output current I_o,maxIs still true. Thus, combining formula (15) and formula (17), one obtains:

in the formula: Δ I ═ I_L2,peak-i_L3,peak-i_L1,valReferred to as current margin. The larger Δ I is used for the dead zone T_dThe larger the current for internally extracting the charge of the junction capacitor of the switching tube, the easier the first switching tube S is to realize₁ZVS of (1). However, the second inductance L₂A third inductor L₃The larger the peak value and the larger the effective value of the current are, the more the copper loss and the iron loss of the switch tube are increased, and the on-state loss and the off-state loss of the switch tube are increased. Considering the trade-off, Δ I is generally taken to be 4A, i.e.: the soft switch can be realized conveniently without causing larger additional loss.

It has been mentioned above that in order to achieve soft switching of all switching tubes under all operating conditions, the second inductor L₂And a third inductance L₃It needs to be designed at maximum load. This results in the second inductance L being at light load conditions in the conventional constant switching frequency PWM control₂And a third inductance L₃The peak-to-peak current value is much larger than the value required to satisfy the soft switching condition, so that the conversion efficiency is seriously reduced.

Therefore, the invention provides a control method for a high-efficiency boost converter of a small UPS, namely, in each switching period, the switching frequency table shown in the table 1 is inquired, the current switching frequency is determined according to the size of the load sampled in real time, and the second inductor L is connected with the first inductor L₂And a third inductance L₃The peak-to-peak current value is maintained in a proper range, so that the system can realize soft switching and has smaller on-state loss, thereby having higher operation efficiency in the whole working range. Switching frequency f in switching frequency table shown in Table 1_s1～f_s4The calculation method of (2) is as follows:

specific examples of the present invention are given below. The design criteria are shown in Table 2.

TABLE 2 design index

By substituting the parameters shown in Table 2 into the formula (18), it is possible to obtain:

actually get the firstAn inductor L₁＝200μH。

Will L₁Formula (19) was substituted with 200 μ H, Δ I ≈ 4A, and parameters shown in table 2, and it is possible to obtain:

actually taking the second inductance L₂＝25μH。

Thus, from equations (20) - (23), the switching frequency table shown in table 3 can be calculated.

TABLE 3 switching frequency under different loads

i_o/I_o,max	∈(0,0.2]	∈(0.2,0.4]	∈(0.4,0.6]	∈(0.6,0.8]	∈(0.8,1]
						f_s(kHz)	270	190	160	130	110

To verify a high efficiency boost converter for a small UPS and a control method thereof, an experimental prototype was made based on the parameters shown in table 4.

Table 4 main circuit parameters of experimental prototype

FIG. 4(a) shows the driving signal u of the first switch tube_gs,S1A first inductor current i_L1Voltage u of storage battery_inAnd an output voltage u_oThe experimental waveform of (2); FIG. 4(b) shows the driving signal u of the second switch tube_gs,S2A second inductor current-i_La2And a third inductor current-i_L3The experimental waveform of (2); FIG. 4(C) shows the first capacitor C₁A second capacitor C₂A third capacitor C₃And a fourth capacitance C₄Experimental waveforms of the voltages at both ends; FIG. 4(d) shows the driving signal u of the first switch tube_gs,S1The voltage u between the drain and the source of the first switch tube_S1A driving signal u of the second switch tube_gs,S2And the voltage u between the drain and the source of the second switch tube_S2The experimental waveform of (2); FIG. 4(e) shows the terminal voltage u of the first diode at full load (output power 250W)_D1Current i of the first diode_D1Terminal voltage u of the second diode_D2Current i of the second diode_D2The experimental waveform of (2); FIG. 4(f) shows the terminal voltage u of the first diode under light load (output power of 50W)_D1Current i of the first diode_D1Terminal voltage u of the second diode_D2Current i of the second diode_D2Experimental waveforms of (4).

As can be seen from fig. 4(a) and 4 (b): first inductance L₁And a second inductance L₂A third inductor L₃All work in a current continuous mode; second inductor current i_L2And a third inductor current i_L3Are equal to, and-i_L2,peak-i_L3,peak-i_L1,val>0; the actual value of the effective duty ratio is D_effAbout 0.76, corresponding to the theoretical value D_eff0.75 is very close. As can be seen from fig. 4 (c): a first capacitor C₁The second electricityContainer C₂A third capacitor C₃And a fourth capacitance C₄Respectively, voltage stress of U_C1＝160V、U_C2＝120V、U_C3＝240V、U _C4280V, all of which are substantially consistent with theoretical values. As can be seen from fig. 4 (d): first switch tube S₁A first switch tube S₂Performing complementary work; first switch tube S₁A first switch tube S₂Has a voltage stress of U_S1＝U _S2160V, which is basically consistent with a theoretical value; drive signal u_gs,S1、u_gs,S2Before the positive pressure comes, the first switch tube S₁A second switch tube S₂Terminal voltage u of_S1、u_S2Both have dropped to zero, indicating that both achieve zero voltage turn-on. As can be seen from fig. 4(e) and 4 (f): under full load condition, the first diode D₁A second diode D₂The turn-off current of (1A) is small, approximately natural turn-off; under the condition of light load, the two are completely naturally turned off; low voltage stress of U_D1＝U _D2160V, which basically coincides with the theoretical value.

FIG. 5 shows the first inductor current i when the output power of the converter is switched from heavy load (250W) to light load (40W)_L1A second inductor reverse current-i_L2And an output voltage u_oExperimental waveforms of (4). It can be seen that: after the load is switched, the voltage u is output_oResume stabilization (U) after 1.16ms _o400V) and a switching frequency f_sThe current margin delta I is-I, the duty ratio D is almost unchanged from 110kHz to 270kHz, and the current margin delta I is equal to-I_L3,peak-i_L2,peak-i_L1,valAnd 4A, thereby verifying the feasibility of the proposed control strategy.

FIG. 6 shows the input voltage U_in40V, output voltage U _o400V, respectively adopting the traditional PWM control mode (f)_s110kHz) and the inventive control scheme, a measured efficiency curve for a high efficiency boost converter for a small UPS under different load conditions is described herein. It can be seen that the actual measured full load efficiency under the two control modes is the same and is 96.44%; however, compared with the conventional PWM control method, the system in the control methodThe actual efficiency is improved from 88.86% to 92.61% when the engine is operated under light load (50W).

From the above experimental results, it can be seen that the high-efficiency boost converter for a small UPS and the control method thereof according to the present invention can change the switching frequency according to the load, and adjust the second inductor L₂(third inductance L₃) So as to ensure the first switching tube S₁And a second switching tube S₂Realize soft switching and have smaller on-state loss. Compared with the traditional PWM (pulse-width modulation) strategy, the light-load efficiency is obviously improved, and the implementation method is simpler.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea, and not to limit it. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall into the protection scope of the present invention.

Claims

1. A method of controlling a high efficiency boost converter for a small UPS, the high efficiency boost converter having two ports connected to a battery and a load, respectively, the high efficiency boost converter comprising:

first switch tube S₁A second switch tube S₂A first capacitor C₁A second capacitor C₂A third capacitor C₃A fourth capacitor C₄A fifth capacitor C₅A first diode D₁A second diode D₂A first inductor L₁A second inductor L₂And a third inductance L₃；

The positive electrode of the storage battery and the first inductor L₁Is connected; the first inductor L₁And the second end of the first switch tube S₁Drain electrode of (1), the second switching tube S₂Source electrode of, the second capacitor C₂The second terminal of (C), the third capacitor C₃Is connected with the second end of the first end; the second switch tube S₂And the second inductor L₂First terminal of, said first capacitor C₁Is connected with the first end of the first connecting pipe; the second inductor L₂And the second terminal of the second capacitor C₂First terminal of, the first diode D₁The anode of (2) is connected; the first diode D₁And the third inductor L₃First terminal of, the fourth capacitance C₄Is connected with the first end of the first connecting pipe; the third inductor L₃And the second terminal of the third capacitor C₃The first terminal of the second diode D₂The anode of (2) is connected; the second diode D₂And the fifth capacitor C₅The first end of (a) is connected to the positive pole of the load; the negative pole of the load, the negative pole of the storage battery and the first switch tube S₁Source electrode of, the first capacitor C₁Second terminal of, the fourth capacitance C₄Second terminal of, the fifth capacitance C₅Is connected with the second end of the first end;

the control method comprises the following steps:

S2, the error signal u is processed_o,eSending to an output voltage controller to obtainTo the regulating signal u_r；

S3, obtaining an output current sampling value i_oThe switching frequency f is adjusted according to the following rule_s：

2. Control method according to claim 1, characterized in that the first inductance L₁A second inductor L₂A third inductor L₃Is provided withThe method comprises the following steps: