CN101710741A - Method and device for smoothing pulse current - Google Patents

Abstract

The invention discloses a pulse current smoothing method and device with good smoothing effect and little voltage fluctuation, wherein the device includes a current detection circuit, a power conversion circuit and an energy storage capacitor; the current detection circuit is used to detect power supply Current size; the power supply change circuit is used to take power from the power supply circuit and charge the energy storage capacitor when the power supply current is less than the preset charging start-up current, and to charge the energy storage capacitor when the power supply current is greater than the preset discharge start-up current. The capacitor takes electricity and supplies power to the power-consuming circuit; the charging start-up current is smaller than the discharge start-up current. Further, the power conversion circuit is a buck-boost DC/DC converter capable of changing the direction of input and output, including four electronic switches and an inductor, wherein the first electronic switch and the second electronic switch form a set of push-pull structures, The third electronic switch and the fourth electronic switch form another set of push-pull structures, and the two ends of the inductance are respectively connected to midpoints of the two push-pull structures.

Description

A pulse current smoothing method and device

technical field

The invention relates to a technique for reducing the ratio of the peak current to the average current of a power supply, in particular to a method and device for smoothing pulse current.

Background technique

The peak current of many electrical equipment is much larger than the average current when working. In the prior art, capacitors or passive components (or passive devices) such as inductors and capacitors are usually used to smooth the pulse current and reduce the operating current. peak-to-average ratio. The above-mentioned method is relatively simple to operate, but the compensation effect is not good, and a large-capacity capacitor is usually required to store electric energy. Moreover, the charging and discharging of the capacitor will inevitably bring about fluctuations in the power supply voltage, resulting in instability of the power supply voltage.

Contents of the invention

The technical problem to be solved by the present invention is to provide a pulse current smoothing method and device with better smoothing effect than the prior art.

In order to solve the above technical problems, the pulse current smoothing method of the present invention comprises the following steps:

Detect the magnitude of the supply current;

When the power supply current is less than the preset charging start-up current, power is taken from the power supply circuit to charge the preset energy storage capacitor;

When the power supply current is greater than the preset discharge starting current, power is taken from the energy storage capacitor to supply power to the power consumption circuit, that is, the power supply current is supplemented at this time;

Wherein, the charging start-up current is smaller than the discharge start-up current.

Further, the charging start-up current is smaller than the average working current of the power consumption circuit, and the discharge start-up current is greater than the average work current of the power consumption circuit.

Further, the method of the present invention further includes: when charging the energy storage capacitor, boosting the energy storage capacitor so that it can store more electric energy.

Further, the method of the present invention further includes: when taking power from the energy storage capacitor, performing step-down processing on the energy storage capacitor, so that it can release the stored electric energy as much as possible.

In order to solve the above technical problems, the pulse current smoothing device of the present invention includes a current detection circuit, a power conversion circuit and an energy storage capacitor;

Wherein, the current detection circuit is used to detect the magnitude of the supply current;

The power supply variation circuit is used to take power from the power supply circuit to charge the energy storage capacitor when the supply current is less than the preset charging startup current; Capacitors can take power to supply power to the power circuit;

Wherein, the charging start-up current is smaller than the discharge start-up current.

Further, the charging start-up current is smaller than the average working current of the power consumption circuit, and the discharge start-up current is greater than the average work current of the power consumption circuit.

Further, the power conversion circuit may be formed by parallel connection of two DC/DC converters, ie DC/DC converters, in opposite directions of energy transmission.

Further, the power conversion circuit can also mainly include a buck-boost DC/DC converter capable of changing the direction of input and output, and the buck-boost DC/DC converter capable of changing the direction of input and output includes four switches and a Inductance, the four switches are the first switch, the second switch, the third switch and the fourth switch, wherein the first switch and the second switch form a set of push-pull structures, and the third switch and the fourth switch form another set Push-pull structure; one end of the inductor is connected between the first switch and the second switch, and the other end is connected between the third switch and the fourth switch.

Furthermore, the four switches are all electronic switches.

Then, by controlling the switching state and timing of each switch, it is possible to control the input and output directions and the conversion of boost and buck, and it is possible to adjust the current and voltage by controlling the duty cycle of the switch.

Still further, the four electronic switches are all MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide-Semiconductor Field-Effect Transistor).

The beneficial effects of the present invention are:

The present invention adopts an active pulse current smoothing scheme. Compared with the traditional passive pulse current smoothing scheme, a capacitor with a smaller capacity can be used to achieve a better smoothing effect, that is, to achieve a smaller current peak-to-average ratio, and only cause very small voltage fluctuations.

Since the present invention performs boosting treatment when charging the energy storage capacitor, when there is no pulse output, the charging of the energy storage capacitor is not affected by the input or output voltage, but only restricted by the withstand voltage of the components, and can store more energy. At the same time, since the voltage reduction process is performed when the energy storage capacitor is discharged, the stored electricity can be released as much as possible during the discharge.

In addition, by adopting the solution of the present invention, the charging current can be preset through the circuit, and the peak current during charging will not be formed.

Description of drawings

Fig. 1 is a schematic diagram of the application scene of the pulse current smoothing device of the present invention;

Fig. 2 is a schematic diagram of the working principle of the pulse current smoothing device of the present invention;

Fig. 3 is a structural schematic diagram of a buck-boost DC/DC converter capable of changing the input and output directions adopted in the present invention;

Fig. 4 is a schematic diagram of the connection relationship between the buck-boost DC/DC converter and the energy storage capacitor capable of changing the direction of input and output;

Fig. 5 is a schematic diagram of the working principle of the buck-boost DC/DC converter capable of changing the direction of input and output when stepping down;

Fig. 6 is a schematic diagram of a typical step-down DC/DC converter;

Fig. 7 is a schematic diagram of the working principle of the buck-boost DC/DC converter capable of changing the direction of input and output when boosting;

Fig. 8 is a schematic diagram of a typical step-up DC/DC converter;

Fig. 9 is a schematic diagram of the circuit structure of a pulse current smoothing device according to a specific example of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

The core principle of the invention is to use an active control circuit to charge and discharge the energy storage capacitor to achieve dynamic and smooth pulse current. Its working process is that when the pulse power circuit is in the pulse gap, it absorbs current from the power supply circuit through a buck-boost DC/DC converter (hereinafter referred to as DC/DC) that can change the direction of input and output, and the energy storage capacitor Charge. When the electric circuit is in the pulse peak current, the energy in the energy storage capacitor is discharged through the DC/DC. The advantage of this is that when storing energy, the DC/DC can actively charge the capacitor to increase the voltage to store more energy and achieve a reasonable voltage tolerance value of the capacitor without being affected by the working voltage; when releasing energy, Through the DC/DC active discharge, the energy in the energy storage capacitor can be fully released without being limited by the fluctuation of the working voltage.

The pulse current smoothing method of the present invention specifically comprises the following steps:

Detect the magnitude of the supply current;

If the supply current is less than the preset charging start-up current, the electric energy is extracted from the power supply circuit, and the preset energy storage capacitor is charged, and when the energy storage capacitor is charged, the energy storage capacitor is boosted;

If the power supply current is greater than the preset discharge start current, power is taken from the energy storage capacitor to supply power to the power-consuming circuit, that is, to supplement the power supply current, and when power is taken from the energy storage capacitor, the energy storage capacitor is stepped down deal with;

Wherein, the charging starting current is smaller than the average working current of the electric circuit, and the discharging starting current is larger than the average working current of the electric circuit.

The application scene of the pulse current smoothing device of the present invention is shown in Figure 1. Inserting the pulse current smoothing device of the present invention between the power supply circuit and the pulse power circuit (circuits with various high peak current or peak power) can reduce the impact on the power supply circuit. peak current requirements.

The pulse current smoothing device 2 of the present invention is inserted between the power supply circuit 1 and the power consumption circuit 3. After adding the device of the present invention, the pulse current or peak current of the power consumption circuit is smoothed by the device of the present invention. From the perspective of the power supply circuit, the power consumption circuit works The current is uniform and the fluctuation is small.

The working principle of the pulse current smoothing device of the present invention is shown in FIG. 2 . The current detection circuit 4 detects the power supply current, and when the power supply current is less than the charging start set value, the power conversion circuit 5 is started to charge the energy storage capacitor 6; when the power supply current is greater than the discharge start set value, the power conversion circuit 5 is started, Energy is taken from the energy storage capacitor 6 to supplement the supply current. The power conversion circuit 5 is a DC/DC converter capable of changing the direction of input and output, and realizing step-up and step-down. There are two main benefits of using a DC/DC converter with boost and step-down functions: one is that when the voltage across the energy storage capacitor goes from high to low during discharge, it can work well, and Fully release energy; in addition, it can charge from a lower voltage to a higher set value when charging, and obtain higher efficiency.

The present invention is mainly composed of a current detection circuit 4 , a power conversion circuit 5 and an energy storage capacitor 6 . When working, the working mode of the power conversion circuit is determined according to the current detection situation. When the supply current is less than the charging start set value, the power conversion circuit 5 takes power from the power supply circuit to charge the energy storage capacitor 6; when the current is greater than the discharge start set value, the power conversion circuit 5 takes power from the energy storage capacitor 6, Supply power to the electrical circuit. The setting value is optimally designed according to the characteristics of the power consumption circuit. The setting values for charge start and discharge start are different, and the set value for charge start is smaller than the set value for discharge start.

Usually, the charging start-up current is smaller than the average working current of the power consumption circuit (the energy consumption and efficiency loss of the pulse current smoothing device of the present invention need to be considered during actual operation), while the discharge start-up current is greater than the average work current of the power consumption circuit. The difference between the charging start-up current and discharge start-up current and the average working current of the power consumption current can be two to three times the fluctuation of the average working current of the power consumption circuit (such as environmental influences, changes in application status, etc.), and the influence of noise and.

In the present invention, the power conversion circuit needs to be specially designed, not only to be able to charge the energy storage capacitor, but also to be able to take power from the energy storage capacitor to supply power to the power consumption circuit. Therefore, the power conversion circuit needs to have a bidirectional conversion capability that can control and change the direction of input and output , at the same time, in order to improve the efficiency of charging and discharging the energy storage capacitor, it is necessary to step up and step down. Boosting the energy storage capacitor can ensure that it can be charged to the design value when charging. The design value is usually higher than the power supply voltage to store enough energy, and reducing the voltage of the energy storage capacitor can ensure that it works at the lowest possible voltage when discharging. To release the energy stored in the energy storage capacitor as much as possible.

Two typical DC/DC converters with work enabling control are connected in parallel according to the opposite direction of energy transmission, which can be used as the power converter proposed by the present invention.

The present invention also proposes a special power converter: a buck-boost DC/DC converter capable of changing the direction of input and output, which has more advantages in cost. The topology and principle of the buck-boost DC/DC converter that can change the direction of input and output are shown in Figure 3. This is a completely symmetrical structure that can realize both left-to-right power conversion and right-to-right power conversion. to left power conversion.

Its core includes four switches SW1-SW4 and an inductor L. In the embodiment of the present invention, the four switches are all electronic switches, and the four electronic switches are implemented by metal oxide semiconductor field effect transistors MOSFET. Among them, the first electronic switch SW1 and the second electronic switch SW2 form a set of push-pull structures, the third electronic switch SW3 and the fourth electronic switch SW4 form another set of push-pull structures, and the inductance L is used to connect the two sets of push-pull structures. The points are connected, that is, one end of the inductor L is connected between the first electronic switch SW1 and the second electronic switch SW2, and the other end is connected between the third electronic switch SW3 and the fourth electronic switch SW4. Because the structure of the buck-boost DC/DC converter that can change the direction of input and output is completely symmetrical, it is only necessary to control the switching state and timing of each electronic switch to control the direction of input and output and the transformation of boost and buck , and can regulate the current and voltage by controlling the duty cycle of the electronic switch.

In the device of the present invention, the DC/DC converter is interposed between the power consumption circuit and the energy storage capacitor, and the basic connection mode of the DC/DC converter and the energy storage capacitor is shown in FIG. 3 .

The working mode of the buck-boost DC/DC converter capable of changing the direction of input and output when stepping down is shown in Figure 5, and the direction of energy transfer is from left to right. Wherein the first electronic switch SW1, the second electronic switch SW2 and the inductor L constitute a typical synchronous switch step-down DC/DC converter. Wherein the third electronic switch SW3 is open, and the fourth electronic switch SW4 is closed. In Fig. 6, Vin represents the input terminal, which refers to the port providing energy to the DC/DC converter; Vout represents the energy output port of the DC/DC converter. The same symbols in other figures have the same meanings.

The principle of a typical step-down DC/DC converter is shown in Figure 6. SW in the figure is an electronic switch, usually a MOSFET. D is a diode, which is passively turned on and plays the role of freewheeling. This diode is replaced by an electronic switch in a synchronous switching type DC/DC converter, enabling higher efficiency.

The working mode of the buck-boost DC/DC converter capable of changing the direction of input and output during boosting is shown in Figure 7, and the direction of energy transfer is from left to right. The third electronic switch SW3, the fourth electronic switch SW4 and the inductor L constitute a typical synchronous switch step-up DC/DC converter. Wherein the first electronic switch SW1 is closed, and the second electronic switch SW2 is open. Schematic diagram of synchronous switch boost mode:

The principle of a typical step-up DC/DC converter is shown in Figure 8.

SW in Figure 8 is an electronic switch, usually using a MOSFET. D is a diode, which is passively turned on and acts as a rectifier. This diode is replaced by an electronic switch in a synchronous switching type DC/DC converter, enabling higher efficiency.

Fig. 9 is a schematic diagram of the circuit structure of a pulse current smoothing device according to a specific example of the present invention. As shown in the figure, the circuit of the pulse current smoothing device of the present invention includes a current sensor, a power detection circuit, a buck-boost DC/DC converter capable of changing the direction of input and output, and an energy storage capacitor. Among them, the buck-boost DC/DC converter capable of changing the direction of input and output is equipped with corresponding control logic and pulse width modulation circuit.

The four electronic switches SW1-SW4 and the inductance L in Fig. 9 are power conversion parts, which perform energy conversion between the power consumption circuit and the energy storage capacitor C. The operational amplifier CSA and the sampling resistor connected to it form a current sensor. A voltage error amplifier, a current error amplifier, a sawtooth wave generator and a comparator connected to it form a PWM (pulse width modulation) circuit, which generates a PWM modulation signal for controlling the duty cycle of the converter. Control logic and four other comparators control the converter's operating mode based on current and voltage states.

Compared with the traditional passive type, the present invention can achieve better smoothing effect with smaller capacity capacitors, that is, smaller current peak-to-average ratio, and very small voltage fluctuation.

The formula for storing energy from a capacitor is as follows:

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; C</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

In the formula, E represents the stored energy; C represents the capacity of the capacitor; v represents the charging voltage.

Therefore, the energy released by the capacitor through the process of discharging the smooth pulse current is:

ΔE=E ₀ -E ₁

$\mathrm{<span\; class="notranslate">\; \&Delta;E</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="v"\; filenames="H2009102108429E00032.png"\; state="\{\{state\}\}">v</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; C\&Delta;v</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="v"\; filenames="H2009102108429E00032.png"\; state="\{\{state\}\}">v</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>$

Δv=v ₀ -v ₁

In the formula, ΔE represents the released energy, which is the difference between the stored energy E ₀ of the capacitor at the beginning of discharge and the stored energy E ₁ of the capacitor at the end of discharge; C represents the capacity of the capacitor; V ₀ represents the charging voltage at both ends of the capacitor at the beginning of discharge ; V ₁ represents the charging voltage across the capacitor when the discharge is terminated.

For example, a conventional 5V power supply, the circuit fluctuates according to the voltage with a tolerance of 5%. After adopting the technical solution of the present invention, the highest charging voltage is doubled, and the residual voltage of the energy storage capacitor at the end of discharge is estimated to be 3V, so the energy that can be released is increased by 18 times. After deducting the efficiency loss of the DC/DC converter, if it is estimated at 90% efficiency, there are still 16 times the benefits. At the same time, the output voltage fluctuation is only the ripple of the DC/DC converter, and there is no voltage drop caused by capacitor discharge, so the output voltage accuracy is higher.

At the same time, when there is no pulse output, the charging of the energy storage capacitor is not affected by the input or output voltage, but is only restricted by the withstand voltage of the components, and more energy can be stored. The charging current can be preset through the circuit, and the peak current during charging will not be formed.

For example, in the data card application of the USB interface, because of the GSM working and pulse mode, its peak current often reaches 2A, while the power supply of the USB interface can only provide 500mA according to the specification. In order to ensure a small peak current and voltage, the previous design is to connect a large capacitor of tens or even hundreds of millifarads in parallel on the power line. The high price and large size bring troubles to the data card design. However, after adopting the technical solution of the present invention, the capacity of the capacitor can be reduced by dozens of times. With the development of semiconductor technology, the cost of DC/DC devices is decreasing day by day, and the application scenarios of the present invention will be broader.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be noted that the above descriptions are only specific embodiments of the present invention, and those skilled in the art can understand the present invention. Various changes and modifications of the invention can be made without departing from the spirit and scope of the invention. In this way, if these modifications and variations of the present invention fall within the scope of the technical solutions described in the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims (10)

1. A pulse current smoothing method is characterized in that comprising the steps: Detect the magnitude of the supply current; When the power supply current is less than the preset charging start-up current, power is taken from the power supply circuit to charge the preset energy storage capacitor; When the power supply current is greater than the preset discharge starting current, power is taken from the energy storage capacitor to supply power to the power consumption circuit, that is, the power supply current is supplemented at this time; Wherein, the charging start-up current is smaller than the discharge start-up current. 2. The pulse current smoothing method according to claim 1, characterized in that: The charging start-up current is smaller than the average working current of the power consumption circuit, and the discharge start-up current is greater than the average work current of the power consumption circuit. 3. the pulse current smoothing method according to claim 1 or 2, is characterized in that, the method also comprises: When charging the energy storage capacitor, the energy storage capacitor is boosted. 4. the pulse current smoothing method according to claim 1 or 2, is characterized in that, the method also comprises: When taking power from the energy storage capacitor, step-down processing is performed on the energy storage capacitor. 5. A pulse current smoothing device, characterized in that: The device includes a current detection circuit, a power conversion circuit and an energy storage capacitor; Wherein, the current detection circuit is used to detect the magnitude of the supply current; The power supply variation circuit is used to take power from the power supply circuit to charge the energy storage capacitor when the supply current is less than the preset charging startup current; Capacitors can take power to supply power to the power circuit; Wherein, the charging start-up current is smaller than the discharge start-up current. 6. The pulse current smoothing device according to claim 5, characterized in that: The charging start-up current is smaller than the average working current of the power consumption circuit, and the discharge start-up current is greater than the average work current of the power consumption circuit. 7. The pulse current smoothing device according to claim 5 or 6, characterized in that: The power conversion circuit is formed by parallel connection of two DC/DC converters in opposite directions of energy transmission. 8. The pulse current smoothing device according to claim 5 or 6, characterized in that: The power conversion circuit mainly includes a buck-boost DC/DC converter capable of changing the direction of input and output; The buck-boost DC/DC converter capable of changing the direction of input and output includes four switches and an inductor, and the four switches are a first switch, a second switch, a third switch and a fourth switch; Wherein the first switch and the second switch form a set of push-pull structures, and the third switch and the fourth switch form another set of push-pull structures; One end of the inductor is connected between the first switch and the second switch, and the other end is connected between the third switch and the fourth switch. 9. The pulse current smoothing device according to claim 8, characterized in that: The four switches are all electronic switches. 10. The pulse current smoothing device according to claim 9, characterized in that: The four electronic switches are metal oxide semiconductor field effect transistors.

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