DC / DC conversion unit with wide voltage regulation capability

Abstract

The invention discloses a DC / DC conversion unit with wide voltage regulation capability. The DC / DC conversion unit comprises a first switch tube S1, a second switch tube S2, an input filter capacitor Ci, an output filter capacitor Co, a resonant inductor Lr, a first primary side resonant capacitor Cp1, a second primary side resonant capacitor Cp2, a first secondary side resonant capacitor Cs1, a second secondary side resonant capacitor Cs2, a first clamping diode Dp1, a second clamping diode Dp2, a first diode D1 and a second diode D2. And a third diode D3 and a fourth diode D4. The DC / DC conversion unit can realize soft switching in a full load range in a wide output voltage range, the positive and negative voltage pulse width time in the frequency modulation process is fixed, the control method is simple, the working flux density of the transformer can be effectively reduced, the size of the transformer is further reduced, and the DC / DC conversion unit is very suitable for an electric vehicle charging scene.

Description

Technical Field

[0001] The present invention belongs to the field of power electronic converters and relates to a DC / DC conversion unit, and in particular to a DC / DC conversion unit with wide voltage regulation capability and a wide range voltage regulation method. Background Art

[0002] With the continuous development of renewable energy around the world, electric vehicles have become a key strategy to address climate change and promote sustainable development. As an important part of the energy structure transformation, electric vehicles are a strategic measure to promote the development of social economy in a greener and more sustainable direction, and their market share continues to expand. However, the diversification of the electric vehicle market has also brought new challenges. Electric vehicles of different models and brands require different voltage levels to meet their charging and operation needs. Therefore, a DC / DC converter with wide voltage regulation capability is required to achieve DC voltage output and realize flexible voltage regulation in the DC power supply system to meet the charging needs of different models. The traditional DC / DC voltage regulation ideas mainly include adjusting the switching frequency and adjusting the duty cycle of the switching device. CN 100421342C adjusts the output voltage by changing the conduction frequency of its input switch tube, but when the switching frequency is too high, the DC / DC converter may lose soft switching, resulting in reduced efficiency, and the output voltage performance is poor when the switching frequency is too low. CN 112928919 A ​​adds an additional active switch device on the secondary side and realizes voltage regulation through the conduction duty cycle of the secondary side switch device. However, this method requires additional active devices, which makes the circuit structure and control method complicated, and increases the volume and cost of the system.

[0003] In summary, there is an urgent need for a DC / DC conversion unit with wide voltage regulation capability to meet current needs. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a DC / DC conversion unit with wide voltage regulation capability. The DC / DC conversion unit of the present invention adjusts the output voltage by adjusting the switching frequency, and can achieve soft switching within a full load range within a wider output voltage range.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A DC / DC conversion unit with wide voltage regulation capability, comprising a half-bridge unit, a DC capacitor, a resonant inductor L r , primary resonant capacitor, secondary resonant capacitor, clamping diode, transformer and rectifier unit, where:

[0007] The half-bridge unit includes a first switch tube S1 and a second switch tube S2;

[0008] The DC capacitor includes the input filter capacitor C i and output filter capacitor C o ;

[0009] The primary resonant capacitor includes a first primary resonant capacitor C p1 and the second primary resonant capacitor C p2 ;

[0010] The secondary side resonant capacitor includes a first secondary side resonant capacitor C s1 and the second secondary resonant capacitor C s2 ;

[0011] The clamping diode includes a first clamping diode D p1 and the second clamping diode D p2 ;

[0012] The rectifying unit includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4;

[0013] The positive electrode of the input terminal passes through the input filter capacitor C i The positive electrode is connected to the collector of the first switch tube S1 and the first primary resonant capacitor C p1 The positive pole of the input terminal is connected to the negative pole of the input filter capacitor C i The negative electrode is connected to the emitter of the second switch tube S2 and the second primary resonant capacitor C p2 The negative pole of the input filter capacitor C i The two ends of constitute the DC input terminal;

[0014] The first clamping diode D p1 The positive electrode is connected to the first primary resonant capacitor C p1 The positive electrode of the first clamping diode D p1 The negative electrode is connected to the first primary resonant capacitor C p1 The negative electrode;

[0015] The second clamping diode D p2 The positive pole is connected to the second primary resonant capacitor C p2 The anode of the second clamping diode D p1 The negative pole is connected to the second primary resonant capacitor C p2 The negative electrode;

[0016] The transformer primary side has the same name end through the resonant inductor L r The middle node of the first switch tube S1 and the second switch tube S2 is connected, and the other end is connected to the first primary resonant capacitor C p1 With the second primary resonant capacitor C p2 The intermediate node of

[0017] The same-name end of the secondary side of the transformer is connected to the middle node of the first diode D1 and the third diode D3, and the other end is connected to the middle node of the second diode D2 and the fourth diode D4;

[0018] The first secondary resonant capacitor C s1 One end of the first secondary resonant capacitor C is connected to the cathode of the second diode D2. s1 The other end is connected to the anode of the second diode D2;

[0019] The second secondary resonant capacitor C s2 One end of is connected to the cathode of the fourth diode D4, and the other end of is connected to the anode of the fourth diode D4;

[0020] The positive electrode of the output terminal is connected to the output filter capacitor C o The positive electrode of the output terminal is connected to the cathode of the first diode D1 and the cathode of the second diode D2, and the negative electrode of the output terminal is connected to the output filter capacitor C o The cathode of is connected to the anode of the third diode D3 and the anode of the fourth diode D4.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] Compared with the existing frequency modulation and duty cycle DC / DC voltage regulation schemes, the DC / DC conversion unit with wide voltage regulation capability of the present invention can realize soft switching within a wide output voltage range within the full load range. At the same time, the positive and negative voltage pulse widths in the frequency modulation process are fixed, the control method is simple, and the working magnetic flux density of the transformer can be effectively reduced, thereby reducing the size of the transformer. Therefore, the DC transformer of the present invention has the characteristics of small size, high efficiency, and wide voltage regulation range, and is very suitable for electric vehicle charging scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the DC / DC conversion unit with wide voltage regulation capability according to the present invention, U i is the DC input voltage, I i is the DC input current, U o is the DC output voltage, I o is the DC output current;

[0024] Figure 2 A schematic diagram of typical driving and voltage and current waveforms of a DC / DC conversion unit with wide voltage regulation capability according to the present invention;

[0025] Figure 3 A schematic diagram of a current path of the topological structure of the circuit of the present invention working in a first switching mode;

[0026] Figure 4A schematic diagram of a current path of the topological structure of the circuit of the present invention working in the second switching mode;

[0027] Figure 5 A schematic diagram of a current path of the topological structure of the circuit of the present invention working in a third switching mode;

[0028] Figure 6 It is a simulation waveform diagram of the resonant current and output voltage of the topological structure of the circuit of the present invention;

[0029] Figure 7 The derived schematic diagram of the topological structure proposed by the present invention is Figure 1 ;

[0030] Figure 8 The derived schematic diagram of the topological structure proposed by the present invention is Figure 2 ;

[0031] Fig. 9 The derived schematic diagram of the topological structure proposed by the present invention is Figure 3 . DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0033] The present invention provides a DC / DC conversion unit with wide voltage regulation capability, such as Figure 1 As shown, the input voltage of the DC / DC conversion unit is U i , the output voltage is U o , including half-bridge unit, DC capacitor, resonant inductor L r , primary resonant capacitor, secondary resonant capacitor, clamping diode, transformer and rectifier unit, where:

[0034] The half-bridge unit includes a first switch tube S1 and a second switch tube S2;

[0035] The DC capacitor includes the input filter capacitor C i and output filter capacitor C o ;

[0036] The primary resonant capacitor includes a first primary resonant capacitor C p1 and the second primary resonant capacitor C p2 ;

[0037] The secondary side resonant capacitor includes a first secondary side resonant capacitor C s1 and the second secondary resonant capacitor C s2 ;

[0038] The clamping diode includes a first clamping diode D p1 and the second clamping diode D p2 ;

[0039] The rectifying unit includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4;

[0040] The positive electrode of the input terminal passes through the input filter capacitor C i The positive electrode is connected to the collector of the first switch tube S1 and the first primary resonant capacitor C p1 The positive pole of the input terminal is connected to the negative pole of the input filter capacitor C i The negative electrode is connected to the emitter of the second switch tube S2 and the second primary resonant capacitor C p2 The negative pole of the input filter capacitor C i The two ends of constitute the DC input terminal;

[0041] The first clamping diode D p1 The positive electrode is connected to the first primary resonant capacitor C p1 The positive electrode of the first clamping diode D p1 The negative electrode is connected to the first primary resonant capacitor C p1 The negative electrode;

[0042] The second clamping diode D p2 The positive pole is connected to the second primary resonant capacitor C p2 The anode of the second clamping diode D p1 The negative pole is connected to the second primary resonant capacitor C p2 The negative electrode;

[0043] The transformer primary side has the same name end through the resonant inductor L r The middle node of the first switch tube S1 and the second switch tube S2 is connected, and the other end is connected to the first primary resonant capacitor C p1 With the second primary resonant capacitor C p2 The intermediate node of

[0044] The same-name end of the secondary side of the transformer is connected to the middle node of the first diode D1 and the third diode D3, and the other end is connected to the middle node of the second diode D2 and the fourth diode D4;

[0045] The first secondary resonant capacitor C s1 One end of the first secondary resonant capacitor C is connected to the cathode of the second diode D2. s1 The other end is connected to the anode of the second diode D2;

[0046] The second secondary resonant capacitor C s2 One end of is connected to the cathode of the fourth diode D4, and the other end of is connected to the anode of the fourth diode D4;

[0047] The positive electrode of the output terminal is connected to the cathode of the first diode D1 and the cathode of the second diode D2 through the output filter capacitor C o The positive electrode of the capacitor, and the negative electrode of the output terminal is connected to the anode of the third diode D3 and the anode of the fourth diode D4 through the negative electrode of the output filter capacitor C o The negative electrode of the capacitor.

[0048] In the present invention, the half-bridge unit is a two-level half-bridge structure, a three-level half-bridge structure or a series half-bridge structure.

[0049] In the present invention, the rectifying unit is a full-bridge rectifying structure, a voltage doubler rectifying structure, a multi-voltage doubler rectifying structure or a bidirectional power device.

[0050] The present invention also provides an operation control method for the above-mentioned DC / DC conversion unit with wide voltage regulation ability, and the method includes the following steps:

[0051] As Figure 2 to Figure 5 shown, the first switching tube S1 and the second switching tube S2 operate complementarily with a duty cycle of 50%. Assuming a control period is T and the time is t0≤t≤t6, where t0≤t≤t3 is the first half cycle and t3≤t≤t6 is the second half cycle, then there are:

[0052] I. The first half cycle

[0053] Set t0 as the initial moment and the starting point of a control period. At the initial moment t0, the first switching tube S1 is turned on;

[0054] The first switching mode: when t0≤t<t1, at the moment t0, the first switching tube S1 is in the on state, the second switching tube S2 is in the off state, the first rectifying diode D1 is turned on, the second rectifying diode D2, the third rectifying diode D3 and the fourth rectifying diode D4 are reverse-biased and turned off, the primary resonant capacitor and the secondary resonant capacitor are connected in series to form an equivalent resonant capacitor, and the resonant inductor L r starts to resonate with the equivalent resonant capacitor, and the primary side current i p of the transformer increases from zero according to the sine function law;

[0055] The second switching mode: when t1≤t<t2, at the moment t1, the voltage u p1 of the first primary resonant capacitor C Cp1 drops to 0, the first clamping diode D p1 is turned on, the first primary resonant capacitor C p1 and the second primary resonant capacitor C p2The voltage remains unchanged; the first switching transistor S1 is in the conducting state, and the second switching transistor S2 is in the off state; the first rectifying diode D1 conducts, and the second rectifying diode D2, the third rectifying diode D3, and the fourth rectifying diode D4 are reverse-biased and turn off; the voltage of the primary winding of the transformer is u p is nU o , and the current i p of the primary side of the transformer decreases linearly from I p (t1);

[0056] The third switching mode: when t2 ≤ t < t3, at the moment t2, the current i s of the secondary side of the transformer decreases linearly to zero, and the secondary diode turns off with zero current;

[0057] II. The second half cycle

[0058] The control period waveform of the second half cycle is symmetric to that of the first half cycle, and the specific control method is as follows:

[0059] The moment t3: t3 is the starting point of the second half control period. At this time, the current of the secondary side of the transformer, that is, the current flowing through the resonant inductor L r is zero. At this time, the third switching transistor S2 is turned on, and the voltages of the first primary resonant capacitor C p1 and the second primary resonant capacitor C p2 are equal to zero and the voltage across the output filter capacitor C o respectively, which is U o ;

[0060] The fourth switching mode: when t3 ≤ t < t4, at the moment t3, the first switching transistor S1 is in the off state, the second switching transistor S2 is in the on state, the third rectifying diode D3 conducts, the first rectifying diode D1, the second rectifying diode D2, and the fourth rectifying diode D4 are reverse-biased and turn off. The primary resonant capacitor and the secondary resonant capacitor are connected in series to form an equivalent resonant capacitor, and the resonant inductor L r resonates with the equivalent resonant capacitor, and the current i p of the primary side of the transformer starts to increase from zero according to the sine function law;

[0061] The fifth switching mode: when t4 ≤ t < t5, at the moment t4, the voltage u p2 of the second primary resonant capacitor C Cp2 drops to 0, the second clamping diode D p2 conducts, and the first primary resonant capacitor C p1 and the second primary resonant capacitor C p2The voltage remains unchanged; the first switching transistor S1 is in the off state, and the second switching transistor S2 is in the on state; the second rectifier diode D2 and the third rectifier diode D3 are conducting, and the first rectifier diode D1 and the fourth rectifier diode D4 are reverse-biased and turned off; the primary winding voltage u of the transformer p is nU o , and the primary current i of the transformer p decreases linearly from I p (t1);

[0062] Sixth switching mode: when t5 ≤ t < t6, at the moment of t5, the current i s of the secondary side of the transformer decreases linearly to zero, and the secondary side diode realizes zero-current turn-off.

[0063] In the present invention, the DC / DC conversion unit with wide voltage regulation ability has the characteristics of a power source, and the transmission power of the DC / DC conversion unit is as follows:

[0064]

[0065] where f s is the switching frequency, U i is the input voltage, and C p is the capacitance value of the primary resonant capacitor.

[0066] In the present invention, the output voltage of the DCDC conversion unit with wide voltage regulation ability is as follows:

[0067]

[0068] where f s is the switching frequency, U i is the input voltage, C p is the capacitance value of the primary resonant capacitor, and R is the load resistance value.

[0069] In the present invention, the output voltage of the DC / DC conversion unit with wide voltage regulation ability can be adjusted within a relatively wide range by adjusting the switching frequency.

[0070] From Figure 6 it can be seen that the DC / DC conversion unit of the present invention can achieve a wide range of output from 200V to 1000V, and the output voltage is smoothly switched.

[0071] From Figure 7 it can be seen that by replacing the diodes D1 - D4 in the rectification unit with active power devices, the control and wide range adjustment of the output voltage can still be achieved.

[0072] From Figure 8It can be seen that replacing the two-level half-bridge on the primary side of the transformer with a three-level NPC half-bridge can still achieve control and wide-range regulation of the output voltage.

[0073] Depend on Fig. 9 It can be seen that replacing the two-level half-bridge on the primary side of the transformer with a series half-bridge structure can still achieve control and wide range adjustment of the output voltage.

Claims

1. A DC / DC conversion unit with wide voltage regulation capability, characterized in that The DC / DC conversion unit includes a half-bridge unit, a DC capacitor, a resonant inductor L r , primary resonant capacitor, secondary resonant capacitor, clamping diode, transformer and rectifier unit, where: The half-bridge unit includes a first switch tube S1 and a second switch tube S2; The DC capacitor includes the input filter capacitor C i and output filter capacitor C o ; The primary resonant capacitor includes a first primary resonant capacitor C p1 and the second primary resonant capacitor C p2 ; The secondary side resonant capacitor includes a first secondary side resonant capacitor C s1 and the second secondary resonant capacitor C s2 ; The clamping diode includes a first clamping diode D p1 and the second clamping diode D p2 ; The rectifying unit includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4; The positive electrode of the input terminal passes through the input filter capacitor C i The positive electrode is connected to the collector of the first switch tube S1 and the first primary resonant capacitor C p1 The positive pole of the input terminal is connected to the negative pole of the input filter capacitor C i The negative electrode is connected to the emitter of the second switch tube S2 and the second primary resonant capacitor C p2 The negative pole of the input filter capacitor C i The two ends of constitute the DC input terminal; The first clamping diode D p1 The positive electrode is connected to the first primary resonant capacitor C p1 The positive electrode of the first clamping diode D p1 The negative electrode is connected to the first primary resonant capacitor C p1 The negative electrode; The second clamping diode D p2 The positive pole is connected to the second primary resonant capacitor C p2 The anode of the second clamping diode D p1 The negative pole is connected to the second primary resonant capacitor C p2 The negative electrode; The transformer primary side has the same name end through the resonant inductor L r The middle node of the first switch tube S1 and the second switch tube S2 is connected, and the other end is connected to the first primary resonant capacitor C p1 With the second primary resonant capacitor C p2 The intermediate node of The same-name end of the secondary side of the transformer is connected to the middle node of the first diode D1 and the third diode D3, and the other end is connected to the middle node of the second diode D2 and the fourth diode D4; The first secondary resonant capacitor C s1 One end of the first secondary resonant capacitor C is connected to the cathode of the second diode D2. s1 The other end is connected to the anode of the second diode D2; The second secondary resonant capacitor C s2 One end of is connected to the cathode of the fourth diode D4, and the other end of is connected to the anode of the fourth diode D4; The positive electrode of the output terminal is connected to the output filter capacitor C o The positive electrode of the output terminal is connected to the cathode of the first diode D1 and the cathode of the second diode D2, and the negative electrode of the output terminal is connected to the output filter capacitor C o The cathode of is connected to the anode of the third diode D3 and the anode of the fourth diode D4.

2. The DC / DC conversion unit with wide voltage regulation capability according to claim 1, characterized in that The half-bridge unit is a two-level half-bridge structure, a three-level half-bridge structure or a series half-bridge structure.

3. The DC / DC conversion unit with wide voltage regulation capability according to claim 1, characterized in that The rectifier unit is a full-bridge rectifier structure, a double voltage rectifier structure, a multi-voltage rectifier structure or a bidirectional power device.

4. An operation control method of a DC / DC conversion unit with wide voltage regulation capability as claimed in any one of claims 1 to 3, characterized in that The method comprises the following steps: The first switch tube S1 and the second switch tube S2 operate complementary with a 50% duty cycle. Assume a control period of T, the time is t0≤t≤t6, where t0≤t≤t3 is the first half period, and t3≤t≤t6 is the second half period, then:

1. The first half of the cycle Set t0 as the initial time and the starting point of a control cycle. At the initial time t0, the first switch tube S1 is turned on; The first switching mode: when \(t_0\leq t \lt t_1\), at the moment \(t_0\), the first switching transistor \(S1\) is in the conducting state, the second switching transistor \(S2\) is in the off state, the first rectifying diode \(D1\) is conducting, and the second rectifying diode \(D2\), the third rectifying diode \(D3\) and the fourth rectifying diode \(D4\) are turned off under the reverse voltage. The primary resonant capacitor and the secondary resonant capacitor are connected in series to form an equivalent resonant capacitor, and the resonant inductor \(L\) r starts to resonate with the equivalent resonant capacitor, and the primary side current \(i\) p increases from zero according to the sine function law; Second switching mode: when t1 ≤ t < t2, at the moment of t1, the voltage u p1 of the first primary resonant capacitor C Cp1 drops to 0, the first clamping diode D p1 conducts, and the voltage of the first primary resonant capacitor C p1 and that of the second primary resonant capacitor C p2 remains unchanged; the first switching transistor S1 is in the on state, and the second switching transistor S2 is in the off state; the first rectifying diode D1 conducts, and the second rectifying diode D2, the third rectifying diode D3, and the fourth rectifying diode D4 are reverse-biased and turn off; the voltage u p of the primary winding of the transformer is nU o , and the primary current i p of the transformer drops linearly from I p (t1); The third switching mode: when t2 ≤ t < t3, at the moment of t2, the value of the current i in the secondary side of the transformer linearly decreases to zero, and the secondary side diode realizes zero-current turn-off; s ​ Second half of the cycle The control cycle waveform of the second half cycle is symmetrical with the control cycle of the first half cycle. The specific control method is as follows: Time t3: t3 is the starting point of the second half of the control cycle. At this time, the secondary current of the transformer flows through the resonant inductor L r The value of is zero, at this time, the third switch tube S2 is turned on, and the first primary resonant capacitor C p1 voltage and the second primary resonant capacitor C p2 The voltage is equal to zero and the output filter capacitor C o Voltage across the terminals U o ; Fourth switching mode: when t3 ≤ t < t4, at the moment of t3, the first switching transistor S1 is in the off state, the second switching transistor S2 is in the on state, the third rectifying diode D3 is conducting, the first rectifying diode D1, the second rectifying diode D2 and the fourth rectifying diode D4 are turned off under the reverse voltage, the primary resonant capacitor and the secondary resonant capacitor are connected in series to form an equivalent resonant capacitor, and the resonant inductor L r starts to resonate with the equivalent resonant capacitor, and the primary side current i p increases from zero according to the sine function law; Fifth switching mode: when t4 ≤ t < t5, at the moment t4, the voltage u of the second primary resonant capacitor C p2 drops to 0, the second clamping diode D Cp2 conducts, and the voltage of the first primary resonant capacitor C p2 and that of the second primary resonant capacitor C p1 remain unchanged; the first switching transistor S1 is in the off state, and the second switching transistor S2 is in the on state; the second rectifying diode D2 and the third rectifying diode D3 conduct, and the first rectifying diode D1 and the fourth rectifying diode D4 are reverse-biased and turn off; the voltage u of the primary winding of the transformer p is nU o , and the primary current i of the transformer p drops linearly from I p (t1);​​ Sixth switching mode: when t5 ≤ t < t6, at the moment of t5, the value of the secondary current i of the transformer linearly decreases to zero, and the secondary diode realizes zero-current turn-off. s The value linearly decreases to zero, and the secondary diode achieves zero-current turn-off.

5. The operation control method of the DC / DC conversion unit with wide voltage regulation capability according to claim 4, characterized in that The DC / DC conversion unit has the characteristics of a power source, and the transmission power of the DC / DC conversion unit is: Among them, f s is the switching frequency, U i is the input voltage, C p is the capacitance of the primary resonant capacitor.

6. The operation control method of the DC / DC conversion unit with wide voltage regulation capability according to claim 4, characterized in that The output voltage of the DCDC conversion unit is: Among them, f s is the switching frequency, U i is the input voltage, C p is the primary resonant capacitor value, and R is the load resistance value.

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