TWM426947U - Interleaved dc-dc converter - Google Patents

Abstract

An interleaved DC-DC converter for fuel cells is disclosed. The interleaved DC-DC converter comprises an input capacitor, a first converter unit, a second converter unit, and an output capacitor. A high voltage ratio and low ripple DC power can be provided for a load by using the interleaved structure of the first converter unit and the second converter unit.

Description

M426947 V. New Description: [New Technology Field] The present invention relates to an interleaved DC-to-DC converter, and in particular to an interleaved DC-to-DC converter that can be used in a fuel cell. [Prior Art] In recent years, due to the global energy crisis and environmental awareness, fuel cells, one of the alternative energy sources, have received increasing attention in the near future. A fuel cell is a clean and pollution-free energy source. Its energy is generated by the reverse reaction of electrolyzed water. After the reaction, only water is produced, so the degree of environmental pollution is relatively low, and the fuel cell is used as a power source in hybrid electric power. Among the electric vehicles, distributed power generation systems, portable power supplies and stationary power supplies, proton exchange membrane fuel cells are most commonly used because of their advantages: (1) they have a lower operating temperature and therefore can be quickly Start and shut down, and react quickly to changes in load; (2) have lower operating pressure and therefore are safer; (3) can be easily modularized; (4) have lower emission ratio ( Emission Ratio) and higher conversion ratio ° Although the proton exchange membrane fuel cell has the above advantages, it has the effect of activation loss, ohmic polarization and concentration loss, resulting in an increase in output voltage with load. The output voltage drops, that is, the output power of the fuel cell increases with loading, and the output voltage gradually decreases, but the output Current is gradually increased, so that a low voltage, high current output of the device. If the 3 M426947 boosts the low voltage output from the fuel cell to a high voltage and sends it to the DC link, it can be used in a wider range of applications. In order to raise the fuel cell voltage output to the required potential and the output voltage is not unstable with load fluctuations, it is necessary to use technology to adjust the fuel cell energy so that the output voltage can be maintained at a stable value. In other words, a good DC-to-DC converter can enhance the application of fuel cells, so it is quite helpful for the development of alternative energy. φ [New content] Therefore, one aspect of the present invention is to provide an interleaved DC-to-DC converter. The interleaved DC-to-DC converter includes an input capacitor, a first converter unit, a second converter unit, and an output capacitor. The high boost ratio and low chopped DC power output can be generated to the load by the structure of the interleaved first converter unit and the second converter unit. The two ends of the input capacitor are electrically connected to the voltage input point and the voltage reference point, respectively. Both ends of the output capacitor are electrically connected to a voltage output point and a voltage φ reference point, respectively. The first converter unit includes a first switch and a second switch. The first open relationship is controlled by the first control signal, and one end of the first switch is electrically connected to the voltage input point by the first inductor, and the other end of the first switch is electrically connected to the voltage reference point, and the first switch and the first switch An inductor is electrically connected to the anode of the first diode. The second open relationship is controlled by the second control signal, one end of the second switch is electrically connected to the voltage input point by the second inductor, the other end of the second switch is electrically connected to the voltage reference point, and the second switch and the second switch The two inductors are electrically connected to the positive pole of the first diode and the positive 4 M426947 of the second diode through the first capacitor, wherein the cathode of the second diode is electrically connected to the voltage output point. The second converter unit includes a third switch and a fourth switch. The third open relationship is controlled by the third control signal, and one end of the third switch is electrically connected to the voltage input point through the third inductor, and the other end of the third switch is electrically connected to the voltage reference point, and the third switch and the third switch The three inductors are electrically connected to the anode of the third diode. The fourth open relationship is controlled by the fourth control signal. One end of the fourth switch is electrically connected to the voltage input point by the fourth inductor, and the other end of the fourth φ switch is electrically connected to the voltage reference point, and the fourth The second capacitor is electrically connected to the anode of the third diode and the cathode of the fourth diode, and the cathode of the fourth diode is electrically connected to the voltage output point. According to an embodiment of the invention, the first control signal can be in phase with the fourth control signal, and the second control signal can be in phase with the third control signal. In addition, as long as the second converter unit voltage chopping phase shifts to the appropriate phase and the first converter unit output voltage chopping waveform is interleaved to produce Φ to reduce the output voltage chopping effect, the associated control signals are not limited to the same phase. According to another embodiment of the present invention, the voltage input point and the voltage reference point may be connected in parallel with the fuel cell, and the voltage output point and the voltage reference point may be connected in parallel with the load. According to still another embodiment of the present invention, the first control signal, the second control signal, the third control signal, and the fourth control signal are generated by the microprocessor. Therefore, the interleaved DC-to-DC converter proposed in this paper can reduce the chopping of the output voltage and provide a high boost ratio output voltage by parallelizing and interleaving the two converter units. Furthermore, since the 5 M426947 parallel structure of the two converter units allows the current to be dispersed in four branches', the current stress of the switch and the inductor can be reduced, so that the high output current of the fuel cell at the time of heavy load can be withstood. [Embodiment] The present invention therefore proposes an interleaved DC-to-DC converter for a fuel cell, comprising an input capacitor, a first converter unit, a second converter unit, and an output capacitor. The high boost ratio and low chopped DC power output can be generated by the interleaved first converter unit and the second converter unit structure. As shown in FIG. 1, the interleaved DC-to-DC converter 120 can be used to boost the output voltage of the fuel cell 110, and supply the load 130 to a high boost ratio and a low chopping DC power output to enable the fuel cell. The applications are more complete. The interleaved DC-to-DC converter 120 can be controlled by various control signals sl-s4 of the microprocessor 140. For example, the microprocessor 140 can utilize the PIC18F8720 for closed loop control. • Further, Figure 2 is a circuit diagram of the interleaved DC-to-DC converter of Figure 1. The interleaved DC-to-DC converter 120 includes an input capacitor Ci, a first converter unit 121, a second converter unit 122, and an output capacitor Co. By the configuration of the interleaved first converter unit 121 and the second converter unit 122, a high boost ratio and a low chopping output voltage Vo can be generated for the load. Both ends of the input capacitor Ci are electrically connected to the voltage input point P and the voltage reference point G, respectively. The input capacitor Ci is connected in parallel with the fuel cell 110 to obtain the input voltage Vi, that is, the input voltage Vi is the potential difference between the voltage input point P and the voltage 6 M426947 voltage reference point G. Both ends of the output capacitor Co are electrically connected to the voltage output point Q and the voltage reference point G, respectively. The output capacitor Co is connected in parallel with the load 130 to provide an output voltage Vo, that is, the output voltage Vo is a potential difference between the voltage output point Q and the voltage reference point G. The first converter unit 121 includes a first switch S1 and a second switch S2. The first switch S1 is controlled by the first control signal si, and one end of the first switch S1' is electrically connected to the voltage input point P by the first inductor L1, and the other end of the first switch S1 is connected with the voltage reference point G. The electrical connection is electrically connected, and the first switch S1 and the first inductor L1 are electrically connected to the anode of the first diode D1. The second switch S2 is controlled by the second control signal s2, one end of the second switch S2 is electrically connected to the voltage input point P through the second inductor L2, and the other end of the second switch S2 is electrically connected to the voltage reference point G. And the second switch S2 and the second inductor L2 are electrically connected to the anode of the first diode D1 and the cathode of the second diode D2 by the first capacitor C1, wherein the cathode of the second diode D2 It is electrically connected to the voltage output point Q. φ and the second converter unit 122 includes a third switch S3 and a fourth switch S4. The third switch S3 is controlled by the third control signal S3. One end of the third switch S3 is electrically connected to the voltage input point P through the third inductor L3, and the other end of the third switch S3 is electrically connected to the voltage reference point G. The third switch S3 and the third inductor L3 are electrically connected to the anode of the third diode D3. The fourth switch S4 is controlled by the fourth control signal s4, and one end of the fourth switch S4 is electrically connected to the voltage input point P through the fourth inductor L4, and the other end of the fourth switch S4 is electrically connected to the voltage reference point G. Connected, and the fourth switch S4 and the fourth inductor L4 are electrically connected to the cathode of the third diode 7 M426947 D3 and the anode of the fourth diode D4 by the second capacitor C2, wherein the fourth diode The negative electrode of D4 is electrically connected to the voltage output point Q. Therefore, as can be seen from FIG. 2, the interleaved DC-to-DC converter of the present invention has a simple circuit structure and can achieve a very high boost ratio with a low duty cycle, thereby reducing the conduction of each switch. Loss and switching losses further increase overall converter efficiency. The operation principle of the first converter unit 121 or the second converter unit 122 in the circuit of the entire interleaved DC-DC converter can be divided into four operation modes, and the following φ will be first in the first converter unit 121. For example, the equivalent circuits in the operation of each mode are shown in FIGS. 3A to 3D, respectively. The equivalent circuit of the operation mode 1 and the operation mode 3 is as shown in FIGS. 3A and 3C. At this time, the first switch S1 and the second switch S2 are in an on state, and the input voltage Vi is pressed across the first inductor L1 and the second inductor L2. Therefore, the current of the two inductors increases linearly and stores energy, and the load current is provided by the output capacitor Co. The change of the inductor currents iL1 and iL2 can be expressed by the formula (1). V = L ^hL = L (1) • dt dt The equivalent circuit of operation mode 2 is shown in Fig. 3B. At this time, the first switch S1 is turned off, the second switch S2 is turned on, and the inductor current L1 is turned on the first two poles. Body D1, at this time, the first inductor L1 voltage releases energy to the first capacitor cn, and the first capacitor C1 is charged, and the second inductor L2 continues to perform the energy storage operation. At this time, the inductor current iL1 can be changed by the formula (2) Said. ~=H1 (2) dt Lx The equivalent circuit of operation mode 4 is shown in Figure 3D. At this time, the first switch 8 M426947 S1 is turned on, the second switch S2 is turned off, and the current of the second inductor L2 is turned on to the second diode. The body D2, at this time, the second inductor L2 and the first capacitor C1 simultaneously release energy to the output capacitor Co and the load, and the inductor current change iL2 at this time can be expressed by the formula (3). diL2 = Κ + Ki ~ V〇(3) dt L2 Through the above four modes of operation, only the voltage VC1 of the first capacitor C1 is an unknown variable, from the circuit architecture and KVL theorem, the first inductor L1, φ the second inductor L2 and the The voltage across the diode D1 and the voltage VC1 of the first capacitor C1 should be zero, and the average voltage of the first inductor L1 and the second inductor L2 is zero at steady state, so the first two poles can be known. The average voltage of the body D1 is the voltage VC1 of the first capacitor C1, and the voltage waveform of the first diode D1 is as shown in FIG. 4, so the voltage VC1 of the first capacitor C1 can be expressed by the formula (4). v =^- (4) vc\ r Dl, avg 2 know the voltage of the first capacitor C1, and then formulate (1) to (3) with the voltage volt-second balance theorem, then we can get the formula (5). Then, the equation (4) is substituted into the equation (6), so that the voltage gain of the first converter unit 121 can be derived as shown in the equation (7), where T is the switching period, D is the duty cycle, and f is the switching frequency. .

V -V V "~~^x(l-D)T + -^DT = 0 (5)

A A ν^ν〇Ι2Κ{ι-ρ)ΤΛρτ = ο (6)

L' L 9 M426947 V〇 =

_2ζ_ lD (7) It can be known from equation (7) that the interleaved DC-DC converter of the present invention can achieve the same boost ratio with a lower duty cycle, and the cross-voltage of the switch can be made due to the relationship of adding the first capacitor. It is reduced to half of the output voltage, which can be known from the operating mode 2 and the operating mode 4, respectively, by the switch crossover of equations (8) and (9). v = v = - (8) (isl, max Cl ^ V - V = ^ 2 - (9) dsijmdx Cl ^ ^ The output power and input power of the first converter unit 121 can be expressed by equations (10) and (11), respectively. Indicates p (10)

〇 RP = ^./. = ^x(/il+/, 2) (11) If L = L1 = L2, then (12) assumes that the first converter unit 121 has no power loss, then Po = Pi ( 13) M426947 V^2Il =

=l-D R 4V2 _/_

(\-D)2R (14) 2Vt

(lD)2R Although the iL1 and iL2 waveforms have a complementary relationship, the maximum and minimum inductor currents are the same, so the relationship between the inductance and the current of the Li and the small is the same as equation (15). (16) is shown. • T -J 1^1 2Vi VDT 1 1 (15) iLUmax - 上人1 _ 2 (\-D)2R 2LX τ - j A'ii VDT l (16) 乂Zl,min —^ (lD)2R 2L And the condition that the first converter unit 121 can operate in the continuous current mode is Iu, min and lL2, min is at least greater than zero, so the boundary condition of the continuous and discontinuous inductor current is

Ll,min

So

A

2V. VDT (lD)2R 2LXD(lD)2R ^4/~ (17) (18) Since the maximum and minimum inductor currents of the first inductor L1 and the second inductor L2 are the same, they are II 1 and II 2 The minimum inductance value is the same, so if the converter is operated in continuous current mode, the inductors L1 and L2 must be at least equal to or equal to the mathematical function D(1_D)2 of equation (18). When the D value is 1/3, the mathematical function D(lD)2 will have a maximum value, which means that the maximum value M426947 has a D value of i/3 when the value of (18) is generated, so when the §}* inductance is set d substitute ι/g into equation (18), and multiply the calculated inductance value by 125 times the margin value to ensure that the inductor current can actually operate in the current continuous mode. According to an embodiment of the present invention, the light load and the heavy load have load resistance values of 2,020 Ω and 450 Ω, respectively. Therefore, the switching frequency is l5\Hz, the duty cycle of the heavy load is about 0.85, and the substitution type (18) is available. In the light load, the current is required to be continued, and the minimum inductance value is 6.23 mH, and at the time of heavy load, it is 179. μΗ, so 260 μΗ can be selected according to the embodiment, so that it can be in continuous current conduction mode under heavy load. ... The output capacitor current changes as shown in Figure 5 ic. As shown, it can be seen from Fig. 5 that the amount of change in capacitance charge is Δβ.

V〇DTFL =CoAV〇 (19), the voltage chopping ratio can be expressed as (20)

AV0 DT V〇a is therefore (21) R0f (AV0/V0) Therefore, the capacitance value can be determined according to the voltage chopping ratio. From the equation (21), the output capacitance c〇 is proportional to the duty cycle d. That is, the designed output capacitor C must be greater than the capacitor value required when the duty cycle is at its maximum. Therefore, according to an embodiment of the present invention, the set voltage chopping ratio is 5%, and the substituting type (21) can obtain the round-out capacitance c〇 is 2.5 μΡ, so that 15 traits can be selected, so that the voltage chopping ratio can be low. At 5%. By describing the disclosure of each operation mode, the control signals, the inductances and the current and voltage waveforms of the respective capacitors in the circuit can be plotted in Figure 5, and the input voltage chopping and current chopping. It can be expressed as equations (22) and (23).

From =(么ϋ_!)(1-浑1 LL η η = ^L{lD)T, LnG{L^L2} (22) • AVC0=IoDT (23), the interleaved DC proposed by the present invention Two sets of converter circuits are used for the DC converter, and the current is distributed in four branches due to the upper and lower staggered parallel configuration of the two converter units, so that the current stress of the switch and the inductor can be reduced, in other words, it is lowered. The voltage chopping is controlled by the control signal to control the switches of the first converter unit and the second converter unit, so that the output voltage of the first converter unit can be chopped with the output voltage of the second converter unit. Offset, the two sets of voltage chopping output are phase-shifted, and the output voltage ripple is reduced. According to one embodiment of the present invention, the output voltage of the fuel cell is about 26 to 43 V (this is the input voltage of the interleaved DC-to-DC converter), and the output voltage to the load is raised to 300 V. At a load of 2,020 Ω, the output power is about 43 W, and when the load is 450 Ω, the output power is about 200 W. Fig. 6 is a waveform diagram showing the output voltage of the interleaved DC-DC converter of the above embodiment. From Fig. 6, the improvement of the chopping waveform in the output voltage of the interleaved DC-to-DC converter of the present invention can be seen. In the sixth picture of detail 13, the peak-to-peak voltage is about 9.5V, and the voltage-to-wave ratio is three. Therefore, according to the above-mentioned new embodiment, the present invention can provide a high rise. The voltage ratio of the voltage is divided by the interleaved circuit structure to reduce the ripple of the output voltage. And because of the circuit structure, the current is dispersed into four shunts, so that the current stress of the switch = fins can be reduced. Therefore, the novel interleaved DC-to-electric converter can enhance various applications of the fuel cell, and thus is of considerable benefit to the alternative development. ", it is worth mentioning that the present invention uses the first converter unit, a control signal and a second control signal remain unchanged, and the second converter unit has a third control signal and a fourth signal to the microprocessor. The adjustment control causes phase shift of the output voltage chopping waveform of the first converter unit, and further interleaves with the output voltage chopping waveform of the first to the converter unit to reduce the voltage chopping value, no recognition, phase output control or non-in-phase output control As long as the second converter single 弋 涟 涟 涟 phase shift to the appropriate phase 汲 and the first converter unit output power = wave waveform staggered, thereby producing a reduced output voltage chopping effect, a feasible implementation of the creation scope protection . The present invention has been disclosed in the above embodiments, but it is not intended to be used by any person skilled in the art. The attached towel should be subject to the definition of Patent Park. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, advantages and embodiments of the drawings are as follows: M426947 FIG. 1 is an interlaced according to an embodiment of the present invention. Functional block diagram of a DC-to-DC converter. Figure 2 is a circuit diagram of the interleaved DC-to-DC converter of Figure 1. 'The 3A-3D diagram shows the four modes of the first converter unit in the interleaved DC-DC converter of Fig. 2. Fig. 4 is a diagram showing voltage waveforms in four modes of the first converter unit in the interleaved DC-DC converter of Fig. 2. • Figure 5 shows the waveforms of the control signals, voltages, and currents of the interleaved DC-to-DC converter in Figure 2. Figure 6 is a waveform diagram showing the output voltage of an interleaved DC-to-DC converter in accordance with an embodiment of the present invention. [Main component symbol description] 110 Fuel cell Ci: Input capacitor 120 Interleaved DC-to-DC converter Co Output capacitor 121 First converter unit Cl First capacitor 122 Second converter unit C2 Second capacitor 130 Load D1 First two Pole body 140 Microprocessor D2 Second diode S1: First switch D3 Third diode S2: Second switch D4 Fourth diode S3: Third switch LI First inductance S4: Fourth switch L2 Two inductors si * First control signal L3 Third inductance 15 M426947 L4 : Fourth inductance Vi : Input voltage Vo : Output voltage s2 : Second control signal s3 : Third control signal s4 : Fourth control signal P : Voltage input point Q: voltage output point G: voltage reference point

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Claims (1)

M426947 VI. Application for Patent Park: 1. An interleaved DC-to-DC converter comprising: an input capacitor with two voltage terminals and a voltage reference-point electrically connected; a first converter unit The first switch is controlled by a first control signal, and one end of the first switch is connected to the voltage input point by a first inductor. The other end of the first switch and the voltage reference point Electrically connected, and the first switch and the first inductor are electrically connected to a positive pole of a first diode; and the second switch is controlled by a second control signal, the first switch One end is electrically connected to the voltage input point by a second inductor. The other end of the second switch is electrically connected to the voltage reference point. The second _ and the second inductor are coupled by a first capacitor. The anode of the first diode and the second diode are electrically connected; wherein the cathode of the second diode is electrically connected to a voltage output point; and the second converter unit comprises: The switch is 'controlled' - the third control signal, The first-end by - the third inductance _ input point electrical, the surface technology 'the other end of the second switch and the electrical age test point: _ and the third switch and the third inductance between - The first pole of the first pole is electrically connected; and the four gates are closed, and the four H' is controlled by a fourth control signal. One of the fourth switches is connected to the voltage input point by a fourth inductor. The other end of the fourth switch is electrically connected to the voltage reference point, and the fourth switch and the fourth inductor are connected by a second capacitor and the third and second diodes of the third diode The positive pole of the body is electrically connected, wherein the negative pole of the fourth diode is electrically connected to the voltage output point; and an output capacitor is electrically connected to the voltage output point and the voltage reference point respectively. 2. The interleaved DC-to-DC converter of claim 1, wherein the first control signal is in phase with the fourth control signal. 3. The interleaved DC-to-DC converter of claim 1, wherein the second control signal is in phase with the third control signal. 4. The interleaved DC-to-DC converter of claim 1, wherein the voltage input point is in parallel with the voltage reference point and a fuel cell. 5. The interleaved DC-to-DC converter of claim 1, wherein the voltage output point is in parallel with the voltage reference point and a load. 6. The interleaved DC-to-DC converter of claim 1, wherein the first control signal, the second control signal, the third control signal, and the fourth control signal are generated by a microprocessor. 18