DC / DC converter and hydrogen fuel cell power system

Abstract

This invention discloses a DC / DC converter, including a DC / DC conversion module and a main control unit. The DC / DC conversion module includes a DC / DC conversion circuit and a conversion control unit. The DC / DC conversion circuit includes a boost converter circuit and an LLC resonant circuit, with the output of the boost converter circuit connected to the input of the LLC resonant circuit. The main control unit is communicatively connected to the DC / DC conversion module and is configured to control the conversion control unit based on the comparison result between the input voltage and the target voltage of the DC / DC converter. The conversion control unit configures the operating state of the DC / DC conversion circuit according to the control of the main control unit, so that the DC / DC converter outputs the target voltage. This invention can boost or buck the input voltage in real time, meeting the requirement of wide-range adjustment of input and output voltage. This invention also provides a hydrogen fuel cell power system.

Description

Technical Field

[0001] This invention relates to the field of voltage conversion technology, and more particularly to a DC / DC converter and a hydrogen fuel cell power system. Background Technology

[0002] With the development of new energy technologies, hydrogen fuel cells, as a clean new energy source, are widely used in electric vehicles and electric forklifts. When hydrogen fuel cells are used as a power source for electric vehicles or electric forklifts, a power battery needs to be added as a power source. Since the output voltage of hydrogen fuel cells is always fluctuating, its output voltage range is wide. However, since there is no unified standard for power batteries, there are multiple voltage platforms. When it is necessary to connect hydrogen fuel cells and power batteries, DC / DC converters are indispensable components. During the energy interaction between hydrogen fuel cells and power batteries, the output voltage of hydrogen fuel cells and the input voltage required by power batteries may interleave. Therefore, DC / DC converters should also have buck-boost interleaving capabilities. However, most DC / DC converters on the market at present are boost DC / DC converters with Boost circuit design or buck DC / DC converters with Buck circuit design, which cannot simultaneously meet the buck-boost requirements.

[0003] Therefore, it is particularly necessary to design a DC / DC converter that can solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a DC / DC converter and a hydrogen fuel cell power system that can boost or buck the input voltage in real time, thus meeting the requirement of wide-range adjustment of input and output voltage.

[0005] To achieve the above objectives, this invention discloses a DC / DC converter, including a DC / DC conversion module and a main control unit. The DC / DC conversion module includes a DC / DC conversion circuit and a conversion control unit. The DC / DC conversion circuit includes a boost converter circuit and an LLC resonant circuit, with the output terminal of the boost converter circuit connected to the input terminal of the LLC resonant circuit. The main control unit is communicatively connected to the DC / DC conversion module and is configured to control the conversion control unit based on a comparison between the input voltage and the target voltage of the DC / DC converter. The conversion control unit configures the operating state of the DC / DC conversion circuit according to the control of the main control unit, so that the DC / DC converter outputs the target voltage.

[0006] Optionally, the DC / DC converter includes at least two or more of the DC / DC conversion modules connected in parallel.

[0007] Optionally, the DC / DC converter further includes a temperature monitoring module, which is electrically connected to the main control unit and is used to monitor the temperature of the power components of the DC / DC converter module.

[0008] Optionally, the DC / DC converter also includes a housing and a fan disposed within the housing. The DC / DC conversion module, the main control unit, and the temperature monitoring module are installed within the housing. The fan is electrically connected to the main control unit. An air outlet and an air inlet are respectively opened on the two side walls of the housing opposite to the front and back of the fan.

[0009] Optionally, the DC / DC converter further includes a first pre-charge protection circuit, which is connected in series with the positive input terminal of the DC / DC converter module. The first pre-charge protection circuit includes a first pre-charge resistor, a first switch, and a second switch. The first pre-charge resistor is connected in series with the first switch, and the second switch is connected in parallel with the first pre-charge resistor and the first switch.

[0010] Optionally, the DC / DC converter further includes a second pre-charge protection circuit, which is connected in series with the positive output terminal of the DC / DC converter module. The second pre-charge protection circuit includes a second pre-charge resistor, a fourth switch, and a fifth switch. The second pre-charge resistor is connected in series with the fourth switch, and the fifth switch is connected in parallel with the second pre-charge resistor and the fourth switch.

[0011] Optionally, the DC / DC converter further includes a first voltage sampling circuit, a second voltage sampling circuit, a third voltage sampling circuit, and a fourth voltage sampling circuit;

[0012] The positive terminals of the first voltage sampling circuit and the second voltage sampling circuit are respectively connected to the two ends of the first pre-charge protection circuit, and the negative terminals of the first voltage sampling circuit and the second voltage sampling circuit are connected to the negative input terminal of the DC / DC conversion module.

[0013] The positive terminals of the third voltage sampling circuit and the fourth voltage sampling circuit are respectively connected to the two ends of the second pre-charge protection circuit, and the negative terminals of the third voltage sampling circuit and the fourth voltage sampling circuit are connected to the negative output terminal of the DC / DC converter module.

[0014] Optionally, the system further includes a first current sampling circuit and a second current sampling circuit. The first current sampling circuit is connected to the positive input terminal of the DC / DC converter module and is used to detect the input current of the DC / DC converter module. The second current sampling circuit is connected to the positive output terminal of the DC / DC converter module and is used to detect the output current of the DC / DC converter module.

[0015] Optionally, the DC / DC converter further includes a discharge unit, which is connected across the positive and negative input terminals of the DC / DC converter module. The discharge unit includes a third switch and a discharge resistor connected in series with the third switch.

[0016] To achieve the above objectives, the present invention also provides a hydrogen fuel cell power system, including a hydrogen fuel cell stack, a power battery, and a DC / DC converter as described above. The hydrogen fuel cell stack is electrically connected to the input terminal of the DC / DC converter, and the output terminal of the DC / DC converter is electrically connected to the power battery.

[0017] The DC / DC converter circuit of this invention includes a Boost converter circuit and an LLC resonant circuit. The Boost converter circuit first boosts the input voltage, and then the operating frequency of the LLC resonant circuit adjusts the output voltage of the Boost converter circuit to achieve a stable boost or buck output of the input voltage. The main control unit can obtain the comparison result between the input voltage and the target voltage of the DC / DC converter, and control the converter control unit according to the comparison result. The converter control unit then configures the operating state of the DC / DC converter circuit to enable the DC / DC converter to output the target voltage. It can perform real-time configuration of the DC / DC converter circuit according to the unstable comparison result between the input voltage and the target voltage to adapt to the situation where the output voltage of the hydrogen fuel cell stack and the input voltage required by the power battery intersect, and realize the function of wide-range adjustment of input and output voltage. Attached Figure Description

[0018] Figure 1 This is a structural block diagram of a DC / DC converter according to an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a DC / DC conversion circuit according to an embodiment of the present invention.

[0020] Figure 3 This is an equivalent circuit diagram of the LLC resonant circuit in an embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of a DC / DC converter according to an embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the hydrogen fuel cell power system according to an embodiment of the present invention. Detailed Implementation

[0023] To explain in detail the technical content, structural features, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0024] Please see Figure 1 and Figure 2 This invention discloses a DC / DC converter 1, including a DC / DC conversion module 11 and a main control unit 12. The DC / DC conversion module 11 includes a DC / DC conversion circuit 112 and a conversion control unit 111. The DC / DC conversion circuit 112 includes a boost circuit 1121 and an LLC resonant circuit 1122. The output terminal of the boost circuit 1121 is connected to the input terminal of the LLC resonant circuit 1122. The main control unit 12 is communicatively connected to the DC / DC conversion module 11. The main control unit 12 is configured to control the conversion control unit 111 according to the comparison result between the input voltage of the DC / DC converter 1 and the target voltage. The conversion control unit 111 configures the operating state of the DC / DC conversion circuit 112 according to the control of the main control unit 12, so that the DC / DC converter 1 outputs the target voltage.

[0025] The DC / DC converter circuit 112 of this invention includes a boost circuit 1121 and an LLC resonant circuit 1122. The boost circuit 1121 first boosts the input voltage, and then the operating frequency of the LLC resonant circuit 1122 adjusts the output voltage of the boost circuit 1121 to achieve a stable boost or buck output of the input voltage. The main control unit 12 can obtain the comparison result between the input voltage and the target voltage of the DC / DC converter 1, and control the conversion control unit 111 according to the comparison result. The conversion control unit 111 then configures the operating state of the DC / DC converter circuit 112 so that the DC / DC converter 1 outputs the target voltage. It can perform real-time configuration of the DC / DC converter circuit 112 according to the unstable comparison result between the input voltage and the target voltage to adapt to the situation where the output voltage of the hydrogen fuel cell stack 2 and the input voltage required by the power battery 3 intersect, and realize the function of wide range adjustment of input and output voltage.

[0026] Please see Figure 2Specifically, the Boost circuit 1121 includes a first inductor L1, a first capacitor C1, a second capacitor C2, a first diode D1, and a first switching transistor Q1. The first capacitor C1 is connected across the positive and negative terminals of the input power supply. One end of C1 is connected to the input terminal of the first inductor L1. The output terminal of the first inductor L1 is connected to the input terminal of the first diode D1 and the input terminal of the first switching transistor Q1. The output terminal of the first diode D1 is connected to one end of the second capacitor C2. The other end of the second capacitor C2 is connected to the output terminal of the first switching transistor Q1. The output terminal of the first switching transistor Q1 is connected to the other end of the first capacitor C1. The Boost converter circuit 1121 can be divided into charging mode and discharging mode during operation. In charging mode, the first switch Q1 is turned on and the first diode D1 is turned off. At this time, the input current flows through the first inductor L1 and the first capacitor C1. The input power supply stores energy in the first inductor L1 and the first capacitor C1, and the second capacitor C2 discharges. In discharging mode, the first switch Q1 is turned off and the first diode D1 is turned on. The first inductor L1 and the first capacitor C1 release energy, and the second capacitor C2 receives energy from the first inductor L1, the first capacitor C1 and the input power supply. Therefore, the voltage across its terminals increases.

[0027] Please see Figure 2 Specifically, the LLC resonant circuit 1122 may include an inverter bridge 1123, a resonant unit 1124, and a rectifier unit 1125. The inverter bridge 1123 is a full-bridge structure, including four switching transistors Q2 to Q5, with capacitors C3 to C6 and diodes D2 to D5 connected in parallel to each transistor. The resonant unit 1124 includes a resonant inductor Lr, a resonant capacitor Cr, a magnetizing inductor Lm, and a transformer T1. The rectifier unit 1125 is a half-wave rectifier circuit, including rectifier diodes D6 and D7, an output capacitor Cout, and a resistor Rl connected in parallel with the output capacitor Cout. The equivalent circuit of the LLC resonant circuit 1122 is as follows: Figure 3 As shown, when the equivalent load Rac changes, the equivalent impedances of Zr and Zo can be changed by adjusting the operating frequency, thereby changing the voltage division ratio and adjusting the output voltage to stabilize the output voltage.

[0028] By setting the transformer T1 in the LLC resonant circuit 1122, the input and output terminals of the DC / DC converter circuit 112 can be isolated, thereby improving safety and reliability.

[0029] Furthermore, the conversion control unit 111 controls the conduction of switching transistors Q1 to Q5 to achieve the purpose of configuring the working state of the DC / DC conversion circuit 112.

[0030] Please see Figure 1In some embodiments, the DC / DC converter 1 includes at least two or more DC / DC conversion modules 11 connected in parallel. By using multiple DC / DC conversion modules 11 in parallel, the market demand for products with different power specifications can be met. Moreover, each DC / DC conversion module 11 operates independently, avoiding the impact of a failure in one DC / DC conversion module 11 on the other DC / DC conversion modules. The main control unit 12 can collect the operating status information of each DC / DC conversion module 11 in real time to make corresponding adjustments.

[0031] Please see Figure 1 In some embodiments, the DC / DC converter 1 further includes a temperature monitoring module 13, which is electrically connected to the main control unit 12. The temperature monitoring module 13 is used to monitor the temperature of the power components in the DC / DC converter module 11. By monitoring the temperature of the power components in the DC / DC converter module 11 through the temperature monitoring module 13, the temperature can be fed back to the main control unit 12 in real time, so that the main control unit 12 can take corresponding measures to deal with the module with excessively high temperature and avoid burning out the DC / DC converter module 11.

[0032] Please see Figure 1 and Figure 4 In some embodiments, the DC / DC converter 1 further includes a housing 14 and a fan 15 disposed within the housing 14. The DC / DC conversion module 11, the main control unit 12, and the temperature monitoring module 13 are installed within the housing 14. The fan 15 is electrically connected to the main control unit 12. An air outlet 142 and an air inlet 141 are respectively opened on the two side walls of the housing 14 and the opposite side of the fan 15. An air duct with low wind resistance can be formed between the air outlet 142 and the air inlet 141, making the heat dissipation efficiency of the DC / DC converter 1 higher. The main control unit 12 can be connected to the fan 15 through a fan drive circuit. When the temperature monitoring module 13 shows that the temperature is too high, the fan 15 can be driven by the main control unit 12.

[0033] Specifically, the front and back sides of the fan 15 are the air outlet and air inlet sides, respectively, that is, the air outlet side is opposite to the air outlet 142, and the air inlet side is opposite to the air inlet 141.

[0034] Please see Figure 1 and Figure 5 In some embodiments, the DC / DC converter 1 further includes a first pre-charge protection circuit 113, which is connected in series with the positive input terminal of the DC / DC converter module 11. The first pre-charge protection circuit 113 includes a first pre-charge resistor R1, a first switch K1, and a second switch K2. The first pre-charge resistor R1 is connected in series with the first switch K1, and the second switch K2 is connected in parallel with the first pre-charge resistor R1 and the first switch K1.

[0035] Please see Figure 1 and Figure 5 Specifically, the DC / DC converter 1 also includes a second pre-charge protection circuit 114, which is connected in series to the positive output terminal of the DC / DC converter module 11. The second pre-charge protection circuit 114 includes a second pre-charge resistor R2, a fourth switch K4 and a fifth switch K5. The second pre-charge resistor R2 and the fourth switch K4 are connected in series, and the fifth switch K5 is connected in parallel with the second pre-charge resistor R2 and the fourth switch K4.

[0036] The first pre-charge protection circuit 113 and the second pre-charge protection circuit 114 can prevent damage to the DC / DC converter module 11 due to a sudden increase in the input and output voltages.

[0037] Please see Figure 5 Furthermore, the DC / DC converter 1 also includes a first voltage acquisition circuit 16, a second voltage acquisition circuit 17, a third voltage sampling circuit 18, and a fourth voltage sampling circuit 19; the positive terminals of the first voltage acquisition circuit 16 and the second voltage acquisition circuit 17 are respectively connected to the two ends of the first pre-charge protection circuit 113, and the negative terminals of the first voltage sampling circuit 16 and the second voltage sampling circuit 17 are connected to the negative input terminal of the DC / DC converter module 11; the positive terminals of the third voltage sampling circuit 18 and the fourth voltage sampling circuit 19 are respectively connected to the two ends of the second pre-charge protection circuit 114, and the negative terminals of the third voltage sampling circuit 18 and the fourth voltage sampling circuit 19 are connected to the negative output terminal of the DC / DC converter module 11.

[0038] The voltages detected by the first voltage acquisition circuit 16, the second voltage acquisition circuit 17, the third voltage sampling circuit 18, and the fourth voltage sampling circuit 19 are V1, V2, V3, and V4, respectively. V1 is the voltage at the input terminal of the first pre-charge protection circuit 113, V2 is the voltage at the input terminal of the DC / DC conversion module 11, V3 is the voltage at the output terminal of the DC / DC conversion module 11, and V4 is the voltage at the input terminal of the second pre-charge protection circuit 114. During output pre-charge, first check if the V4 voltage is normal. If abnormal, report a fault directly. If normal, close the fourth switch K4. After a preset time, check if the V3 voltage reaches the preset ratio of the V4 voltage. If yes, open the fourth switch K4 and close the fifth switch K5, completing the output pre-charge. If not, open the fourth switch K4 and report a pre-charge failure fault. Similarly, during input pre-charge, first check if the V1 voltage is normal. If abnormal, report a fault directly. If normal, close the first switch K1. After a preset time, check if the V2 voltage reaches the preset ratio of the V1 voltage. If yes, open the first switch K1 and close the second switch K2, completing the input pre-charge. If not, open the first switch K1 and report a pre-charge failure fault.

[0039] Please see Figure 5 In some embodiments, the DC / DC converter 1 further includes a first current sampling circuit 116 and a second current sampling circuit 117. The first current sampling circuit 116 is connected to the positive input terminal of the DC / DC converter module 11 and is used to detect the input current of the DC / DC converter module 11. The second current sampling circuit 117 is connected to the positive output terminal of the DC / DC converter module 11 and is used to detect the output current of the DC / DC converter module 11. The main control unit 12 can acquire the input and output currents collected by the first and second current sampling circuits 116 and 117 to calculate the input and output power, which is used to calculate the efficiency of the DC / DC converter 1. It can also monitor the magnitude of the input and output currents to prevent excessive current.

[0040] Please see Figure 5 In some embodiments, the DC / DC converter 1 further includes a discharge unit 115, which is connected across the positive and negative input terminals of the DC / DC converter module 11. The discharge unit 115 includes a third switch K3 and a discharge resistor R3 connected in series with the third switch K3. After the DC / DC converter 1 has finished working in the hydrogen fuel cell power system, the DC / DC converter 1 is disconnected from the power battery 3 and the hydrogen fuel cell stack 2 is shut down. At this time, there will be a small amount of residual hydrogen and oxygen inside the hydrogen fuel cell stack 2. Therefore, the hydrogen fuel cell stack 2 is still reacting and has residual electrical energy. By closing the second switch K2 and the third switch K3, the discharge resistor R3 can form a circuit with the hydrogen fuel cell stack 2, and the residual electrical energy on the hydrogen fuel cell stack 2 can be consumed in the form of heat. This can prevent internal carbonization in the hydrogen fuel cell stack 2 and extend its service life.

[0041] Specifically, the first switch K1, the second switch K2, the third switch K3, the fourth switch K4, and the fifth switch K5 can be relays, and the main control unit 12 can control the first switch K1, the second switch K2, the third switch K3, the fourth switch K4, and the fifth switch K5 through the switch control circuit.

[0042] Furthermore, the main control unit 12 and the DC / DC converter module 11 are connected via a CAN communication circuit.

[0043] Please see Figure 5 This application also provides a hydrogen fuel cell power system, including a hydrogen fuel cell stack 2, a power battery 3, and a DC / DC converter 1 as described above. The hydrogen fuel cell stack 2 is electrically connected to the input terminal of the DC / DC converter 1, and the output terminal of the DC / DC converter 1 is electrically connected to the power battery 3.

[0044] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A DC / DC converter, characterized in that, include: DC / DC conversion module, the DC / DC conversion module including DC / DC conversion circuit and conversion control unit; The DC / DC converter circuit includes a boost circuit and an LLC resonant circuit. The output terminal of the boost circuit is connected to the input terminal of the LLC resonant circuit. The voltage output by the boost circuit is divided by adjusting the operating frequency of the LLC resonant circuit to achieve boost output or buck output. A main control unit is communicatively connected to the DC / DC converter module. The main control unit is configured to control the converter module based on the comparison result of the unstable input voltage and the target voltage of the DC / DC converter. The conversion control unit configures the operating state of the DC / DC conversion circuit in real time according to the control of the main control unit, so that the DC / DC converter outputs the target voltage; The DC / DC converter further includes a discharge unit, which is connected across the positive and negative input terminals of the DC / DC converter module. The discharge unit includes a third switch and a discharge resistor connected in series with the third switch.

2. The DC / DC converter according to claim 1, characterized in that, It includes at least two or more of the DC / DC conversion modules connected in parallel.

3. The DC / DC converter according to claim 1, characterized in that, It also includes a temperature monitoring module, which is electrically connected to the main control unit and is used to monitor the temperature of the power components of the DC / DC converter module.

4. The DC / DC converter according to claim 3, characterized in that, It also includes a housing and a fan disposed within the housing. The DC / DC converter module, the main control unit, and the temperature monitoring module are installed inside the housing. The fan is electrically connected to the main control unit. An air outlet and an air inlet are respectively opened on the two side walls of the housing opposite to the front and back of the fan.

5. The DC / DC converter according to claim 1, characterized in that, It also includes a first pre-charge protection circuit, which is connected in series to the positive input terminal of the DC / DC converter module. The first pre-charge protection circuit includes a first pre-charge resistor, a first switch, and a second switch. The first pre-charge resistor is connected in series with the first switch, and the second switch is connected in parallel with the first pre-charge resistor and the first switch.

6. The DC / DC converter according to claim 5, characterized in that, It also includes a second pre-charge protection circuit, which is connected in series to the positive output terminal of the DC / DC converter module. The second pre-charge protection circuit includes a second pre-charge resistor, a fourth switch and a fifth switch. The second pre-charge resistor is connected in series with the fourth switch, and the fifth switch is connected in parallel with the second pre-charge resistor and the fourth switch.

7. The DC / DC converter according to claim 6, characterized in that, It also includes a first voltage sampling circuit, a second voltage sampling circuit, a third voltage sampling circuit, and a fourth voltage sampling circuit; The positive terminals of the first voltage sampling circuit and the second voltage sampling circuit are respectively connected to the two ends of the first pre-charge protection circuit, and the negative terminals of the first voltage sampling circuit and the second voltage sampling circuit are connected to the negative input terminal of the DC / DC conversion module. The positive terminals of the third voltage sampling circuit and the fourth voltage sampling circuit are respectively connected to the two ends of the second pre-charge protection circuit, and the negative terminals of the third voltage sampling circuit and the fourth voltage sampling circuit are connected to the negative output terminal of the DC / DC converter module.

8. The DC / DC converter according to claim 1, characterized in that, It also includes a first current sampling circuit and a second current sampling circuit. The first current sampling circuit is connected to the positive input terminal of the DC / DC converter module and is used to detect the input current of the DC / DC converter module. The second current sampling circuit is connected to the positive output terminal of the DC / DC converter module and is used to detect the output current of the DC / DC converter module.

9. A hydrogen fuel cell power system, characterized in that, It includes a hydrogen fuel cell stack, a power battery, and a DC / DC converter as described in any one of claims 1-8, wherein the hydrogen fuel cell stack is electrically connected to the input terminal of the DC / DC converter, and the output terminal of the DC / DC converter is electrically connected to the power battery.

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