CN114710036A - A high-efficiency boost converter for small UPS and its control method - Google Patents

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

A high-efficiency boost converter for small UPS and its control method

technical field

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

Background technique

The DC/DC converter in a small and lightweight uninterruptible power supply (UPS) generally uses fewer large-capacity batteries in series as the input DC voltage source, so the battery voltage in this UPS is lower, and the inverter in the UPS Then a high DC input voltage is required. Usually this kind of small UPS adopts a push-pull circuit (Push-Pull) to realize a high DC voltage for the post-stage inverter to work, but the design of the push-pull circuit is complicated and the cost is also high. Due to the intermittent primary current and large current ripple, the battery will heat up seriously and affect its life; two switching tubes are used, and the input of low voltage and high current makes the circuit loss larger; in order to achieve a high boost ratio, the The step-up transformer has leakage inductance, which brings losses, and a filter inductor is required for the secondary. Obviously, the circuit cost of this solution is also higher.

In order to solve the above problems, scholars have proposed various high-gain transformerless DC converters. Compared with the push-pull circuit, the transformerless high-gain converter has no high-frequency transformer, and has the advantages of small size, low cost and high efficiency, and is especially suitable for small UPS. When the duty cycle D of the traditional boost converter exceeds 0.8, the current stress and on-state loss of the inductance and the switch tube increase seriously, and the conversion efficiency decreases significantly. Therefore, the voltage gain G of the conventional Boost converter generally does not exceed 5. Scholars from various countries have introduced boost networks such as switched inductors, switched capacitors, quasi-Z sources or Boost into traditional Boost converters, and have come up with a variety of transformerless high-gain Boost schemes. Most of these schemes can realize single-stage conversion of energy, and the conversion efficiency is high, but the voltage gain usually does not exceed twice that of the traditional Boost converter. To this end, scholars further propose a high-gain scheme based on boost network expansion. Although the scheme of expanding the boosting network can significantly improve the boosting capability, the volume and weight of the converter will also increase significantly due to the increase in the number of energy storage elements. Increasing the switching frequency of the converter can effectively reduce the volume and weight of the energy storage element and improve the power density, but the switching loss of the power tube will also increase sharply, and the conversion efficiency will be seriously reduced. The introduction of soft switching technology can effectively solve these problems. To this end, scholars have further proposed a number of high-gain converters based on the boost network to extend the ZVS. However, these topologies generally have the following problems: (1) the number of diodes is large and the structure is complex; (2) some switches still work in a hard switching state, and it is difficult to further improve the efficiency; (3) the voltage stress of the switches is high, and it is necessary to use High withstand voltage semiconductor devices lead to large on-state loss and high cost; (4) there is a phenomenon of duty cycle loss.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a high-efficiency boost converter for a small UPS and a control method thereof. The converter has continuous input current, small current ripple, does not affect the service life of the battery, and has a high performance. Voltage gain, able to boost lower battery voltage to higher load voltage at lower duty cycle, less power devices and lower voltage stress, lower rated voltage power with lower price and better performance The device, using the proposed control method, can achieve soft switching in the entire load variation range, while further reducing the on-state loss, ensuring that the system has high operating efficiency.

In order to achieve the above purpose, the proposed scheme is as follows:

A control method for a high-efficiency boost converter for a small UPS, wherein two ports of the high-efficiency boost converter are respectively connected to a battery and a load, and the high-efficiency boost converter includes:

First switch S ₁ , second switch S ₂ , first capacitor C ₁ , second capacitor C ₂ , third capacitor C ₃ , fourth capacitor C ₄ , fifth capacitor C ₅ , first diode D _1. A second diode D ₂ , a first inductor L ₁ , a second inductor L ₂ and a third inductor L ₃ ;

The anode of the battery is connected to the first end of the first inductor L ₁ ; the second end of the first inductor L ₁ is connected to the drain of the first switch tube S ₁ and the second switch tube S The source of ₂ , the second end of the second capacitor C2, and the _second end of the _third capacitor C3 are connected; the drain of the _second switch tube S2 is connected to the second end of the _second inductor L2. The first end is connected to the first end of the first capacitor C ₁ ; the second end of the second inductor L ₂ is connected to the first end of the second capacitor C ₂ and the first diode D ₁ The anode of the _first diode D1 is connected to the first end of the _third inductor L3 and the first end of the fourth capacitor _C4; the first end of the _third inductor L3 is connected to the The two terminals are connected to the first terminal of the _third capacitor C3 and the anode of the _second diode D2 _; the cathode of the second diode D2 is connected to the first terminal of the fifth capacitor _C5 terminal, the positive pole of the load is connected; the negative pole of the load and the negative pole of the battery, the source pole of the _first switch tube S1, the second terminal of the first capacitor _C1 , the fourth capacitor The second end of _C4 and the second end of the fifth capacitor _C5 are connected;

The control method includes the following steps:

S1. Compare the output voltage sampling value u _o of the high-efficiency boost converter with the reference value u _{o, ref} to obtain an error signal u _{o, e} ;

S2. the error signal _{u o, e} is sent to the output voltage controller to obtain the adjustment signal ur;

S3. Obtain the output current sampling value i _o of the high-efficiency boost converter, and adjust the switching frequency f _s according to the following rules:

Among them, ΔI=-i _L2,peak -i _L3,peak -i _L1,val , U _in is the input voltage; L ₁ is the first inductance; L ₃ is the third inductance; U _o is the output voltage; I _o,max is the maximum value of the output average current; ΔI is the current margin, i _L1,val is the valley value of the first inductor current i _L1 , -i _L2,peak and -i _L3,peak are the _second inductor L2 and the third respectively Reverse current peak value _of inductor L3.

S4. the adjustment signal ur and the unipolar triangular carrier wave uc of the switching frequency fs are intersected to generate the drive signal _{ugs , S1 of} the _first switch tube S1; _{ugs , S1} are reversed to generate the second _The drive signal _{ugs,S2 of the switch tube S2} .

Further, the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ are designed as follows:

Among them, D is the duty ratio of the driving signal of the _first switch tube S1; δ% is the percentage of the maximum current ripple allowed by the _first inductor L1 to the maximum average current of the _first inductor L1; P _o,max is the output power The maximum value of ; f _s,min is the minimum switching frequency.

Compared with the prior art, a high-efficiency boost converter for a small UPS and a control method thereof proposed by the present invention can make the battery have a smaller output current ripple without affecting its service life, and can be used in The entire load variation range ensures that the UPS system has high operating efficiency, and the implementation method is relatively simple and the cost is low.

Description of drawings

1 is a schematic diagram of the circuit structure of a high-efficiency boost converter for a small UPS provided by the present invention;

2 is a block diagram of a system control strategy of a high-efficiency boost converter for a small UPS provided by the present invention;

3 is a modal analysis diagram of a high-efficiency boost converter for small UPS provided by the present invention;

4 is an experimental waveform diagram of the steady-state characteristics of a high-efficiency boost converter for a small UPS provided by the present invention;

5 shows the current i L1 of the first inductor L ₁ , the current i _L1 of the second The experimental waveforms of the reverse current _- i _L2 of the inductor L2 and the output voltage u _o ;

FIG. 6 is the measured efficiency curve under different load conditions when a high-efficiency boost converter for a small UPS according to an embodiment of the present invention adopts the traditional PWM control method (f _s =110kHz) and the control method proposed by the present invention .

Detailed ways

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. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

FIG. 1 shows a high-efficiency boost converter for a small UPS provided by the present invention. Including: first switch S ₁ , second switch S ₂ , first capacitor C ₁ , second capacitor C ₂ , third capacitor C ₃ , fourth capacitor C ₄ , fifth capacitor C ₅ , first diode tube D ₁ , second diode D ₂ , first inductor L ₁ , second inductor L ₂ and third inductor L ₃ ; the anode of the battery is connected to the first end of the first inductor L ₁ ; The second end of the _first inductor L1, the drain of the _first switch S1, the source of the _second switch S2, the second end of the _second capacitor C2, the The second end of the _three capacitors C3 is connected; the drain of the _second switch tube S2 is connected to the first end of the _second inductor L2 and the first end of the first capacitor _C1 ; The second end of the _second inductor L2 is connected to the first end of the _second capacitor C2 and the anode of the _first diode D1 _; the cathode of the first diode D1 is connected to the third The first end _of the inductor L3 and the first end of the fourth capacitor _C4 are connected; the second end of the _third inductor L3 is connected to the first end of the _third capacitor C3, the second two _The anode of the pole tube D2 is connected; the cathode of the _second diode D2 is connected to the first end of the fifth capacitor _C5 and the positive pole of the load; the negative pole of the load and the negative pole of the battery are connected , The source of the _first switch tube S1, the second end of the first capacitor _C1 , the second end of the fourth capacitor _C4 , and the second end of the fifth capacitor _C5 are connected.

According to FIG. 2 , the control strategy block diagram includes 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 It is used to obtain the output voltage u _o of the load, and generate a voltage control signal to realize the constant voltage control of the load; the frequency control branch is used to obtain the output current i _o of the load, and generate a frequency control signal, which is used for When changing, adjust the switching frequency.

The steps are:

S1. Compare the output voltage sampling value u _o with the reference value u _o,ref to obtain an error signal u _o,e ;

S2. the error signal _{u o, e} is sent to the output voltage controller to obtain the adjustment signal ur;

S3. Obtain the output current sampling value i _o , and select the following switching frequency f _s according to the switching frequency table;

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. the adjustment signal ur and the unipolar triangular carrier wave uc of the switching frequency fs are intersected to generate the drive signal _{ugs , S1 of} the _first switch tube S1; _{ugs , S1} are reversed to generate the second _The drive signal _{ugs,S2 of the switch tube S2} .

The working process of a high-efficiency boost converter for a small UPS shown in FIG. 1 will be described below.

In order to simplify the analysis, the following assumptions are made: the first switch S ₁ , the second switch S ₂ , the first diode D ₁ , the second diode D ₂ , the first capacitor C ₁ , the second capacitor C ₂ , The third capacitor C ₃ , the fourth capacitor C ₄ , the fifth capacitor C ₅ , the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ are all ideal devices; the first capacitor C ₁ , the second capacitor C _2. The third capacitor C ₃ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ are large enough to ignore the voltage ripple; the body diodes of the first switch S ₁ and the second switch S ₂ are D _S1 and D respectively _S2 .

Based on the above assumptions, after entering a steady state, the waveform of the high-efficiency boost converter for a small UPS in one switching cycle can be divided into four modes. The equivalent circuit diagrams of each mode are shown in Fig. 3(a)-(d) respectively.

Before time t ₀ , the body diode D _S1 of the _first switch transistor S1 has been turned on for freewheeling.

(1) Mode 1, t ₀ ~ t ₁ stage: (the equivalent circuit is shown in Figure 3(a))

At time t ₀ , the first switch tube S ₁ is turned on at zero voltage, and its body diode D _S1 is naturally turned off. In this mode, the second switch S ₂ , the first diode D ₁ , and the second diode D ₂ are all reverse biased; the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ Both withstand forward voltage; the first inductor current i _L1 increases linearly, and the currents of the second inductor L ₂ and the third inductor L ₃ first decrease linearly in the reverse direction to zero, and then increase linearly in the forward direction. At this point, there are:

Wherein, U _C1 , U _C2 , U _C3 and U _C4 are the terminal voltages of the first capacitor C ₁ , the second capacitor C ₂ , the third capacitor C ₃ , and the fourth capacitor C ₄ respectively, U _in is the input voltage, L ₂ is the second inductor.

(2) Mode 2, t ₁ ~ t ₂ stage: (the equivalent circuit is shown in Figure 3(b))

At time t ₁ , the first switch tube S ₁ is turned off, and mode 2 starts. At the moment when the _first switch S1 is turned off, the currents of the _first inductor L1, the _second inductor L2, and the _third inductor L3 all flow into the node m, forcing the body diode D _S2 of the _second switch S2 to conduct Freewheeling; at the same time, the first diode D ₁ and the second diode D ₂ are forward biased; the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ are all subjected to reverse voltage, which The currents both decrease linearly in the positive direction. At this point, there are:

(3) Mode 3, stage t ₂ ~ t ₃ : (the equivalent circuit is shown in Figure 3(c))

At time t ₂ , the second switch tube S ₂ is turned on at zero voltage, and its body diode D _S2 is naturally turned off, and mode 3 starts. In this mode, the first inductor current i _L1 continues to decrease linearly in the forward direction, while the currents of the second inductor L ₂ and the third inductor L ₃ decrease in the forward direction to zero and then increase linearly in the reverse direction. Its current expression is the same as formula (2).

(4) Mode 4, stage t ₃ ~ t ₄ : (the equivalent circuit is shown in Figure 3(d))

At time _t3 , the _second switch tube S2 is turned off, and mode 4 starts. The first inductor current i _L1 flows into the node m; the currents of the second inductor L ₂ and the third inductor L ₃ both flow out of the node m, and the body diode D _S1 of the first switch transistor S ₁ conducts freewheeling. The current expressions of the first inductance L ₁ , the second inductance L ₂ and the third inductance L ₃ are similar to equation (1). _At time t4, the first switching transistor S ₁ is turned on at zero voltage, and the next switching cycle is entered.

Ignoring the dead time, according to the volt-second balance of each inductor, we can get:

In addition, from Figure 3(c), we can get:

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

It can be seen that when the duty ratio D=0.8, the voltage gain G=13, which is more than twice the voltage gain of the traditional boost converter, indicating that the high-efficiency boost converter for small UPS proposed by the present invention has Extremely strong boost capability, so it can boost the lower terminal voltage of the battery to a higher load voltage with a lower duty cycle.

In addition, it can be seen from the modal analysis that the first switch S 1 , the second switch S 2 , the first diode D 1 and the second switch S ₁ , the second switch S ₂ , the first diode D ₁ and the second switch in the high-efficiency boost converter for small UPS proposed by the present invention _The voltage stress of diode D2 is:

Wherein, U _S1 is the voltage stress borne by the _first switch S1, U _S2 is the voltage stress borne by the _second switch S2, U _D1 is the voltage stress borne by the _first diode D1, and U _D2 is the second _Voltage stress experienced by diode D2.

It can be seen that the first switch S ₁ , the second switch S ₂ , the first diode D ₁ and the second diode D ₂ have the same voltage stress, which is about 1/3 of the output voltage, so it can be Use power devices with low voltage ratings. Due to the relatively lower price of power devices with lower voltage ratings and lower on-state resistance or forward voltage drop, cost and on-state losses are correspondingly lower.

The voltage stress of the first capacitor C ₁ , the second capacitor C ₂ , the third capacitor C ₃ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ is:

U _C5 = U _o (11)

Wherein, U _C5 is the terminal voltage of the fifth capacitor _C5 .

The effective current values of the first inductor L ₁ , the second inductor L ₂ and the third inductor L ₃ are respectively:

Among them, I _L1,rms , I _L2,rms , I _L3,rms are the RMS currents of the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ , respectively; I _L1 , I _L2 are the first inductors, respectively The current average value of L ₁ and the second inductor L ₂ ; ΔI _L1 and ΔI _L2 are the current peak-to-peak values of the first inductor L ₁ and the second inductor L ₂ , respectively.

The RMS currents of the _first switch S1 and the _second switch S2 are respectively:

Wherein, I _S1,rms and I _S2,rms are the RMS currents of the first switch tube S ₁ and the second switch tube S ₂ respectively, and I _o is the output current.

In order to ensure that a high-efficiency boost converter for a small UPS shown in FIG. 1 realizes Zero Voltage Switching (ZVS), it is necessary to make the first inductor L ₁ work in the current continuous mode, and the second inductor L ₂ and The third inductors L ₃ all work in a current bidirectional flow mode, and can satisfy: -i _L2,peak -i _L3,peak -i _L1,val >0 under the maximum load condition. To this end, the present invention provides a design method for the first inductance L ₁ , the second inductance L ₂ and the third inductance L ₃ :

The forward voltage borne by the first inductor L ₁ , the second inductor L ₂ and the third inductor L ₃ is:

In the formula, U _L1 is the terminal voltage of the first inductor L ₁ ; U _L2 is the terminal voltage of the second inductor L ₂ ; U _L3 is the terminal voltage of the third inductor L ₃ .

The current peak-to-peak values of the first inductor L ₁ , the second inductor L ₂ and the third inductor L ₃ are:

In the formula, ΔI _L3 is the current peak-to-peak value of the third inductor L ₃ , and T _s is the switching period.

Soft switching current conditions:

ΔI _L1 +ΔI _L2 +ΔI _L3 ≥2(I _L1 +I _L2 +I _L3 ) (16)

In the formula, IL3 is the current average value of the _third inductor _L3 .

Arranged:

In the formula, I _in is the average value of the input current.

Generally speaking, the _first inductance L1 of the Boost converter can be designed so that the current peak-to-peak value ΔI _L1 does not exceed δ% of its maximum average current I _L1,max , where δ%=30%. At this point, there are:

In order to reliably achieve soft switching over the entire range of operating conditions, it is necessary to ensure that equation (17) still holds under the condition of the maximum output current I _o,max . Therefore, combining equations (15) and (17), we can get:

In the formula: ΔI＝-i _L2,peak -i _L3,peak -i _L1,val , which is called the current margin. The larger ΔI is, the larger the current used to extract the electric charge of the junction capacitance of the switch transistor in the dead zone T _d is, and the easier it is to realize the ZVS of the first switch transistor S ₁ . However, the current peak-to-peak value and the effective value of the second inductor L ₂ and the third inductor L ₃ are correspondingly larger, resulting in increased copper loss, iron loss, on-state loss and turn-off loss of the switch. Considering the trade-off, ΔI generally takes 4A to be more appropriate, that is, it can easily realize soft switching without causing large additional losses.

As mentioned above, in order to realize the soft switching of all switches under the whole operating conditions, the second inductor L ₂ and the third inductor L ₃ need to be designed under the maximum load. This leads to the conventional constant switching frequency PWM control, under light load conditions, the current peak-to-peak value of the second inductor L ₂ and the third inductor L ₃ is much larger than the value required to satisfy the soft switching condition, thereby seriously reducing the conversion efficiency.

To this end, the present invention proposes a control method for a high-efficiency boost converter for a small UPS, that is, in each switching cycle, the switching frequency table shown in Table 1 is consulted, and according to the size of the real-time sampled load, Determine the current switching frequency and maintain the peak-to-peak current of the second inductor L ₂ and the third inductor L ₃ within an appropriate range, so that the system can achieve soft switching and have a small on-state loss, so that the entire work can be achieved. It has high operating efficiency within the range. The calculation methods of the switching frequencies f _s1 to f _s4 in the switching frequency table shown in Table 1 are as follows:

Specific embodiments of the present invention are given below. Its design indicators are shown in Table 2.

Table 2 Design Indicators

Substituting the parameters shown in Table 2 into equation (18), we can get:

The first inductance L ₁ =200μH is actually taken.

Substituting L ₁ =200μH, ΔI≈4A and the parameters shown in Table 2 into equation (19), we can get:

The second inductance L ₂ =25μH is actually taken.

Therefore, according to 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

In order to verify a high-efficiency boost converter for small UPS and its control method, an experimental prototype was made based on the parameters shown in Table 4.

Table 4 The main circuit parameters of the experimental prototype

Figure 4(a) is the experimental waveform of the driving signal _ugs,S1 of the first switch tube, the first inductor current i _L1 , the battery voltage u _in and the output voltage u _o ; Figure 4(b) is the driving of the second switch tube The experimental waveforms of the signal u _gs,S2 , the second inductor current-i _La2 and the third inductor current-i _L3 ; Figure 4(c) shows the first capacitor C ₁ , the second capacitor C ₂ , the third capacitor C ₃ and the third The experimental waveform of the voltage across the four capacitors _C4 ; Fig. 4(d) is the driving signal u _gs,S1 of the first switch tube, the drain-source voltage u _S1 of the first switch tube, and the driving signal u of the second switch tube _{gs, S2} , the experimental waveform of the drain-source voltage u _S2 of the second switch tube; Figure 4(e) shows the terminal voltage u _D1 of the first diode and the first diode at full load (output power is 250W) The experimental waveforms of the current i _D1 of the second diode, the terminal voltage u _D2 of the second diode, and the current i _D2 of the second diode; Fig. 4(f) is the light load (the output power is 50W) of the first diode The experimental waveforms of the terminal voltage u _D1 , the current i _D1 of the first diode, the terminal voltage u _D2 of the second diode, and the current i _D2 of the second diode.

It can be seen from Figures 4(a) and 4(b) that the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ all work in the current continuous mode; the second inductor current i _L2 and the third inductor current i _L3 is equal, and -i _L2,peak -i _L3,peak -i _L1,val >0; the measured value of the effective duty cycle is D _eff ≈ 0.76, which is very close to the theoretical value D _eff =0.75. It can be seen from FIG. 4( c ) that the voltage stresses of the first capacitor C ₁ , the second capacitor C ₂ , the third capacitor C ₃ and the fourth capacitor C ₄ are U _C1 =160V, U _C2 =120V, U _C3 =240V, U _C4 =280V, which are basically consistent with the theoretical value. It can be seen from Figure ₄ (d) that the _first switch S1 and the _first switch S2 work complementary _; the voltage stress of the first switch S1 and the first switch S2 is U _S1 =U _S2 =160V , which is basically consistent with the theoretical value; before the positive voltage of the driving signals u _{gs, S1} , u _{gs, S2} arrives, the terminal voltages u _S1 and u _S2 of the first switch tube S ₁ and the second switch tube S ₂ have both dropped to zero, This shows that both achieve zero-voltage turn-on. It can be seen from Figures 4(e) and 4(f) that: under full load conditions, the turn-off currents of the first diode D ₁ and the second diode D ₂ are small (1A), which are approximately natural turn-offs; Under the condition of light load, the two completely realize the natural turn-off; the voltage stress is relatively low, which is U _D1 =U _D2 =160V, which is basically consistent with the theoretical value.

Figure 5 shows the experimental waveforms of the first inductor current i _L1 , the second inductor reverse current -i _L2 and the output voltage u _o when the output power of the converter is switched from a heavy load (250W) to a light load (40W). It can be seen that after the load switching, the output voltage u _o becomes stable again after 1.16ms (U _o =400V), and the switching frequency f _s changes from 110kHz to 270kHz, the duty cycle D is almost unchanged, and the current margin ΔI= -i _L3,peak -i _L2,peak -i _L1,val are kept within the design range of 4A, thus verifying the feasibility of the proposed control strategy.

Fig. 6 shows the high efficiency of a small UPS described in this paper when the input voltage U _in =40V and the output voltage U _o =400V, when the traditional PWM control mode (f _s =110kHz) and the control mode of the present invention are adopted respectively. Measured efficiency curves of the boost converter under different load conditions. It can be seen that the measured full-load efficiency of the two control methods is the same, both are 96.44%; however, compared with the traditional PWM control method, the measured efficiency of the system under the control method under light load (50W) operation is improved by 88.86% was 92.61%.

It can be seen from the above experimental results that a high-efficiency boost converter for small UPS and its control method proposed by the present invention can change the switching frequency according to the size of the load, adjust the second inductance L ₂ (the third inductance L 2 ) ₃ ) current peak-to-peak value, thereby ensuring that the _first switching transistor S1 and the _second switching transistor S2 realize soft switching and have less on-state loss. Compared with the traditional PWM modulation strategy, the light-load efficiency has been significantly improved, and the implementation method is relatively simple.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass non-exclusive inclusion such that a process, method, article or device comprising a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention, but are not intended to limit it. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims (2)

1. A control method for a high-efficiency boost converter for a small UPS, wherein the two ports of the high-efficiency boost converter are respectively connected to a battery and a load, and the high-efficiency boost converter is include: First switch S ₁ , second switch S ₂ , first capacitor C ₁ , second capacitor C ₂ , third capacitor C ₃ , fourth capacitor C ₄ , fifth capacitor C ₅ , first diode D _1. A second diode D ₂ , a first inductor L ₁ , a second inductor L ₂ and a third inductor L ₃ ; The anode of the battery is connected to the first end of the first inductor L ₁ ; the second end of the first inductor L ₁ is connected to the drain of the first switch tube S ₁ and the second switch tube S The source of ₂ , the second end of the second capacitor C2, and the _second end of the _third capacitor C3 are connected; the drain of the _second switch tube S2 is connected to the second end of the _second inductor L2. The first end is connected to the first end of the first capacitor C ₁ ; the second end of the second inductor L ₂ is connected to the first end of the second capacitor C ₂ and the first diode D ₁ The anode of the _first diode D1 is connected to the first end of the _third inductor L3 and the first end of the fourth capacitor _C4; the first end of the _third inductor L3 is connected to the The two terminals are connected to the first terminal of the _third capacitor C3 and the anode of the _second diode D2 _; the cathode of the second diode D2 is connected to the first terminal of the fifth capacitor _C5 terminal, the positive pole of the load is connected; the negative pole of the load and the negative pole of the battery, the source pole of the _first switch tube S1, the second terminal of the first capacitor _C1 , the fourth capacitor The second end of _C4 and the second end of the fifth capacitor _C5 are connected; The control method includes the following steps: S1. Compare the output voltage sampling value u _o of the high-efficiency boost converter with the reference value u _{o, ref} to obtain an error signal u _{o, e} ; S2. the error signal _{u o, e} is sent to the output voltage controller to obtain the adjustment signal ur; S3. Obtain the output current sampling value i _o , and adjust the switching frequency f _s according to the following rules:

Among them, ΔI=-i _L2,peak -i _L3,peak -i _L1,val , U _in is the input voltage; L ₁ is the first inductance; L ₃ is the third inductance; U _o is the output voltage; I _o,max is the maximum value of the output average current; ΔI is the current margin, i _L1,val is the valley value of the first inductor current i _L1 , -i _L2,peak and -i _L3,peak are the _second inductor L2 and the third respectively Reverse current peak value _of inductor L3. S4. the adjustment signal ur and the unipolar triangular carrier wave uc of the switching frequency fs are intersected to generate the drive signal _{ugs , S1 of} the _first switch tube S1; _{ugs , S1} are reversed to generate the second _The drive signal _{ugs,S2 of the switch tube S2} . 2 . The control method according to claim 1 , wherein the designs of the first inductor L ₁ , the second inductor L ₂ , and the third inductor L ₃ are as follows: 3 .

Among them, D is the duty ratio of the driving signal of the _first switch tube S1; δ% is the percentage of the maximum current ripple allowed by the _first inductor L1 to the maximum average current of the _first inductor L1; P _o,max is the output power The maximum value of ; f _s,min is the minimum switching frequency.

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