WO2015176582A1

WO2015176582A1 - Dc/dc boost conversion module and circuit

Info

Publication number: WO2015176582A1
Application number: PCT/CN2015/075097
Authority: WO
Inventors: 肖安波
Original assignee: 深圳市长昊机电有限公司
Priority date: 2014-07-01
Filing date: 2015-03-26
Publication date: 2015-11-26
Also published as: CN104092373A; CN104092373B

Abstract

A DC/DC boost conversion module, comprising an inductor (L2), a switching tube (T2), a diode (D2), a capacitor (C2), and a protection unit (F2). The positive electrode of a power input (Vin) is connected to one terminal of the inductor (L2). The other terminal of the inductor (L2) is connected to the positive electrode of the diode (D2) and to the positive electrode of the switching tube (T2). The negative electrode of the diode (D2) is connected to the positive electrode of the capacitor (C2) and to the positive electrode of the output (Vo). The negative electrode of the switching tube (T2) is connected to the negative electrode of the capacitor (C2) and to one terminal of the protection unit (F2). The other terminal of the protection unit (F2) is connected to the negative electrode of the power input (Vin) and to the negative electrode of the output (Vo). The DC/DC boost conversion module can provide effective protection for the circuit and the system when the switching tube becomes ineffective due to short circuits.

Description

DC/DC boost converter module and circuit

Technical field

The invention belongs to the field of electronic technology, and in particular relates to a DC/DC boost converter module and circuit.

Background technique

Figure 1 shows a conventional DC/DC boost converter circuit with input voltage Vin and input current Iin. When the switch T1 is turned on, the inductor L1 current increases. When the switch T1 is turned off, the inductor L1 current passes through the diode. The D1 freewheeling charges the capacitor C1. In this circuit, the output voltage Vo is greater than the input voltage Vin, the input current Iin is greater than the output current Io, and the current flowing through the fuse F1 is equal to Iin.

The fuse F1 plays a protective role in the circuit. Especially when the short circuit of the switch tube T1 in the figure fails, Vin is always applied to the inductor L1, so that the current of the inductor L1 continues to rise until the protection unit F1 is blown. However, there is a defect when the circuit is applied to the photovoltaic product. The input voltage Vin is connected to the PV component PV output. Since the PV module output has a short-circuit current limiting characteristic, the switching transistor T1 will only have a short-circuit failure, and the inductor L1 current will only The short-circuit current rises to the photovoltaic module PV, and the short-circuit current is only about 10% larger than the rated current even under standard illumination, and the fuse F1 cannot be blown at all, nor can it function as a protection system.

As shown in FIG. 2, it is another conventional DC/DC boost converter circuit. The conversion circuit mounts the protection unit at the output end of the boost converter circuit, and functions as an output short circuit protection. The name of 201310381249.7 is a description of "a protection circuit for the output short-circuit of the boosted constant current power supply". However, the circuit in Figure 2 only protects the output short circuit, and cannot be further protected by the short circuit of the semiconductor switch tube T in the circuit.

With the country's emphasis on environmental protection and new energy, photovoltaic power generation systems have been widely developed, and photovoltaic inverters and inverters have also been widely used. On the other hand, we see that due to the PV output current limiting characteristics of the PV modules, the protection unit does not play a protective role, resulting in fire events.

Summary of the invention

It is an object of the embodiments of the present invention to provide a DC/DC boost converter module and circuit, which aims to solve the problem that the existing DC/DC boost converter circuit cannot protect the circuit when the switch tube fails.

The embodiment of the present invention is implemented as follows. A DC/DC boost converter module includes an inductor, a switch tube, a diode, a capacitor, and a protection unit. The anode of the input power source is connected to one end of the inductor, and the inductor is The other end is connected to the anode of the diode and the anode of the switch tube, the cathode of the diode is connected to the anode of the capacitor and the anode of the output, the cathode of the switch tube is connected to the cathode of the capacitor and one end of the protection unit, and the other end of the protection unit is connected to the cathode of the input power source. And the negative pole of the output.

Further, the switch tube is a MOS tube, the anode of the switch tube is a D pole of the MOS tube, and the cathode of the switch tube is an S pole of the MOS tube.

Further, the switching transistor is an insulated gate bipolar transistor IGBT, the positive pole of the switching transistor is the C pole of the IGBT, and the negative pole of the switching transistor is the E pole of the IGBT.

Further, the protection unit is an automatic protection device.

Further, the protection unit is a switching device.

Further, the input power source is at least one group of photovoltaic components.

Further, the input power source is two sets of photovoltaic components.

The present invention also provides a DC/DC boost converter circuit, the apparatus comprising at least two DC/DC boost converter modules, the DC/DC boost converter module being coupled in parallel between the input power source and the output.

Further, the input power of the DC/DC boost converter circuit is four sets of photovoltaic components.

The embodiment of the invention provides a new DC/DC boost converter module and circuit, and the protection unit is placed after the junction of the switch tube and the negative pole of the capacitor, and the input negative pole is connected between the protection unit and the output terminal. Thus, the current If flowing through the protection unit during normal operation is equal to the input current Iin minus the output current Io. Once the switch tube is short-circuited, the current If is equal to Iin, which is greater than the Iin-Io current during normal operation, and the protection unit can be disconnected. Protect circuits and systems.

DRAWINGS

1 is a circuit diagram of a prior art DC/DC boost converter circuit.

2 is a circuit diagram of a conventional DC/DC boost converter circuit with output fuse protection.

3 is a circuit diagram of a DC/DC boost converter module according to Embodiment 1 of the present invention.

4 is a current flow diagram of a DC/DC boost converter module according to Embodiment 1 of the present invention when a switch tube is closed.

FIG. 5 is a current flow diagram of the DC/DC boost converter module according to Embodiment 1 of the present invention when the switch is turned off.

6 is a DC/DC boost converter module according to Embodiment 1 of the present invention, when the switch tube is short-circuited Current trend diagram.

7 is a circuit diagram of a DC/DC boost converter module according to Embodiment 1 of the present invention when two sets of photovoltaic cells are used as inputs.

FIG. 8 is a circuit diagram of a DC/DC boost converter module according to Embodiment 2 of the present invention when four groups of photovoltaic cells are used as inputs.

9 is a circuit diagram of a DC/DC boost converter module according to Embodiment 3 of the present invention.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

As shown in FIG. 3, an embodiment of the present invention provides a DC/DC boost converter module, including an inductor L2, a switch tube T2, a diode D2, a capacitor C2, and a protection unit F2 (using a fuse in this embodiment), and an input power source. The anode of Vin is connected to one end of the inductor L2, the other end of the inductor L2 is connected to the anode of the diode D2 and the anode of the switch tube T2, the cathode of the diode D2 is connected to the anode of the capacitor C2 and the anode of the output, and the cathode of the switch tube T2 is connected to the capacitor C2. One end of the negative electrode and the fuse F2; the other end of the fuse F2 is connected to the negative electrode of the input power source Vin and the negative electrode of the output. The switching tube T2 may be a MOS tube or an IGBT. When the switching tube is a MOS tube, the positive electrode is the D pole of the MOS tube, the negative electrode is the S pole of the MOS tube, and the switching tube is the insulated gate bipolar transistor IGBT, and the positive electrode is the IGBT. C pole, the negative pole is the E pole of the IGBT.

As shown in FIG. 4, when the switch tube T2 is closed, the input voltage is applied across the inductor L2, and the input current Iin is increased. The current flows from the anode of the input power source Vin through the inductor L2, the switch tube T2, and the fuse F2, and Return to the input by the negative pole of the input power. At the same time, the diode D2 is turned off, the capacitor C2 is discharged to maintain the power supply of the load R, and the output voltage Vo is lowered. The discharge current flows from the positive pole of the capacitor C2, passes through the output positive pole, flows through the load R to the output negative pole, and is blown. The device F2 returns to the negative terminal of the capacitor C2. At this stage, the current If flowing through the fuse F2 includes two parts: one is the storage current of the inductor L2 (ie, the input current Iin), and the other is the discharge current of the capacitor C2 (ie, the output current Io), the two current directions. Instead, the actual current If=Iin-Io is made smaller than Iin.

As shown in FIG. 5, when the switch tube T2 is turned off, the current of the inductor L2 cannot be abruptly changed, and the capacitor C2 and the load R are supplied with power through the diode D2. As a result of supplying power to the capacitor C2, the output voltage Vo is raised, and the input current Iin passes through the inductor L2, the diode D2, the capacitor C2, and the fuse F2 reaches the negative terminal of the input power source Vin and the output Vo to form a loop. At the same time, the input current Lin is from the positive pole of the input power source Vin, through the inductor L2, the diode D2, the output positive pole, the load R and the output negative pole, and reaches the negative pole of the input power source Vin to form another loop to realize the power supply of the load R. At this stage, the current If flowing through the fuse F2 is equal to the current charged to the capacitor C2, which is equal to the input current Iin, minus the load R current (also the output current Io), that is, the actual current If=Iin-Io, Iin is smaller.

In summary, during the normal operation of the above-mentioned switching tube T2, the current If through the fuse F2 is equal to the input current Iin minus the output current Io. According to the principle of power balance, Io=Vin*Iin/Vo, so

If=Iin-Iin*Vin/Vo=Iin*(1-Vin/Vo),

It can be seen that if there is no boost, Vo=Vin, If=0; if the boost ratio is doubled, then Vo=2Vin, If=0.5Iin, that is, the current flowing through the fuse is only half of the input current, the circuit It works fine.

When the short circuit of the switch tube T2 fails, as shown in FIG. 6, the switch tube T2 is always in the on state, and the capacitor C2 cannot supply the load R, that is, Io is 0. At this time, the input current Iin flows from the anode of the input power source Vin. Inductor L2, switch tube T2 and fuse F2, and return to the input through the negative pole of the input power supply, If = Iin. Therefore, according to If=Iin*(1-Vin/Vo) during normal operation and If=Iin at the time of failure, the rated current of the fuse can be selected to be less than Iin, so that both the normal operation and the short-circuit failure of the switching tube T2 can be considered at the same time. Time protection.

According to the above circuit operation principle, specifically to the photovoltaic product, the DC/DC boost converter module of the embodiment of the present invention can use at least one set of photovoltaic components as the input power of the DC/DC boost converter module. As shown in Figure 7, the input power to the DC/DC boost converter module is two sets of PV modules PV1 and PV2. The photovoltaic modules PV1 and PV2 merge through respective branch fuses F6, F3, F7, F4 to form an input voltage Vin. The nominal current rating of PV1 and PV2 is 8.0A, the standard illumination short-circuit current is 9A, and F6 and F7 are 10-15A fuses. The maximum open circuit voltage of PV1 and PV2 is 600V, the full load MPPT voltage range is 250~500V, and the output voltage of DC/DC boost converter module is designed to be Vo=500V. At the same time, after the input voltage is greater than 500V, the switch tube T3 stops working, and the output voltage Vo= Vin, If=0. when When the input voltage is equal to 250V, If=Iin*(1-Vin/Vo)=0.5Iin=0.5*8*2=8A, If the input voltage is between 250 and 500Vdc, the input current is 8A, If is 0~8A. Between, that is, the normal operating current is less than 8A, considering the overload factor, F5 can select a fuse of 10~12A. In this way, when the fault occurs in the switch tube T3, if the illumination is weak and the input current Iin is less than 16A, there is no risk for the reactance and loop cable with a rated current of 16A. Once the illumination becomes stronger, the input current Iin is greater than 16A. The fuse F5 of 10~12A is quickly blown to prevent the burnout of the reactance and the cable.

Example 2

As shown in FIG. 8, this embodiment further provides a DC/DC boost converter circuit including at least two DC/DC boost converter modules shown in FIG. 3, and the at least two DC/DC boost converter modules. Parallel between the input supply and the output, that is, the inputs of all DC/DC boost converter modules are connected in parallel to the input supply, and the outputs of all DC/DC boost converter modules are connected in parallel to the output. Four sets of photovoltaic modules PV1, PV2, PV3, and PV4 can be used to form an input voltage Vin after confluence through respective branch fuses. The nominal current rating of PV1, PV2, PV3, and PV4 is 8.0A, the standard illumination short-circuit current is 9A, and the F6 and F7 are 10-15A fuses. The maximum open circuit voltage of PV1 and PV2 is 1000V, and the full load MPPT voltage range is 450~750V. It is assumed that the output voltage of DC/DC boost converter module is Vo=800V. At the same time, after the input voltage is greater than 800V, the switch tubes T4 and T5 stop working and the output voltage Vo=Vin, If1=If2=0. When the input voltage is equal to 450V, If1=If2=0.5*Iin*(1-Vin/Vo)=0.22Iin=0.22*8*4=7A, when the input voltage is between 450 and 800Vdc and the input current Iin is 32A. If is between 0 and 7A, that is, the current through the fuses F9 and F10 during normal operation is less than 7A. Considering the overload factor, the fuses F9 and F10 can select 10A fuses. In this way, when the fault occurs in the fault of the switch tube T4 or T5, if the illumination is weak and the input current Iin is less than 10A, there is no risk for the reactance and loop cable with a rated current of 16A. Once the illumination becomes strong, the input short-circuit current is greater than After 13A, the 10A fuse F9 or F10 is quickly blown to prevent burnout of reactance and cables. In the circuit shown in Figure 8, there are two sets of independent DC/DC voltage conversion modules, and in general, one of the switching tubes T4 or the switching tubes T5 is short-circuited. After such a failure, PV1, PV2, PV3 and PV4 are four. The short-circuit current of the string is simultaneously flowed into the fuse F9 or the fuse F10. For the fuse of 10A, as long as the short-circuit current of each group of PV branches is 3A or more, it can be blown, and it is easier to prevent the expansion of the fault.

The input and output negative connection method of the conventional DC/DC voltage conversion circuit is improved by the embodiment of the present invention, so that the current flowing through the protection unit during normal operation is only the input and output difference current, and the total input current is in the failure mode, and In the case of preventing the diode from being damaged as well, the energy of the output voltage continues to be poured into the DC/DC voltage conversion circuit, causing the system to expand. The DC/DC voltage conversion module and circuit of the embodiments of the present invention enable a conventional DC/DC boost converter circuit to be reliably applied to a photovoltaic product, and avoid short-circuit current of the photovoltaic module after a short-circuit failure of the semiconductor switch transistor. The power unit causes the risk of malfunction and even fire.

Example 3

As shown in Fig. 9, another embodiment of the present invention. The difference between this embodiment and the embodiment 1 is that the protection unit in the first embodiment adopts an automatic protection device (such as a fuse, a fuse, etc.), and in the embodiment, a switching device T6 (such as a contactor, a thyristor SCR, or the like) is used. IGBT, Mos tube, etc., in the DC/DC voltage conversion module shown in Figure 9, the short-circuit failure of the switching tube T3 causes the fault to expand, which may further cause over-temperature or smoke, and the switch can be opened according to these fault phenomena. Device T6, which implements circuit protection.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

A DC/DC boost converter module includes an inductor, a switch tube, a diode, a capacitor, and a protection unit. The anode of the input power source is connected to one end of the inductor, and the other end of the inductor is connected to the anode of the diode and the anode of the switch tube. The cathode of the diode is connected to the anode of the capacitor and the anode of the output, the cathode of the switch tube is connected to the cathode of the capacitor and the end of the protection unit; the other end of the protection unit is connected to the cathode of the input power source and the cathode of the output.
The DC/DC boost converter module according to claim 1, wherein the switch transistor is a MOS transistor, the anode of the switch transistor is a D pole of a MOS transistor, and a cathode of the switch transistor is a MOS transistor. S pole.
The DC/DC boost converter module according to claim 1, wherein the switch transistor is an insulated gate bipolar transistor IGBT, and a positive pole of the switch transistor is a C pole of the IGBT, and the switch transistor is negative. Extremely E-pole of IGBT.
The DC/DC boost converter module of claim 1 wherein said protection unit is an automatic protection device.
The DC/DC boost converter module of claim 1 wherein said protection unit is a switching device.
The DC/DC boost converter module of claim 1 wherein said input power source is at least one set of photovoltaic components.
The DC/DC boost converter module of claim 6 wherein said input power source is two sets of photovoltaic components.
A DC/DC boost converter circuit, characterized in that the device comprises at least two DC/DC boost converter modules according to any one of claims 1 to 7, said at least two DC/DC liters The voltage conversion module is connected in parallel between the input power supply and the output.
The DC/DC boost converter circuit according to claim 8, wherein the input power of the DC/DC boost converter circuit is four sets of photovoltaic components.