A DC / DC conversion unit with wide voltage regulation capability

Abstract

The application discloses a DC / DC conversion unit with wide voltage regulation capability, which comprises a first switch tube S1, a second switch tube S2, an input filter capacitor C i , an output filter capacitor C o , a resonant inductor L r , a first primary side resonant capacitor C p1 , a second primary side resonant capacitor C p2 , a first secondary side resonant capacitor C s1 , a second secondary side resonant capacitor C s2 , a first clamping diode D p1 , a second clamping diode D p2 , a first diode D1, a second diode D2, 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 is fixed during the frequency modulation process, the control method is simple, the working magnetic density of the transformer can be effectively reduced, the volume of the transformer is reduced, and the DC / DC conversion unit is very suitable for electric vehicle charging scenes.

Description

TECHNICAL FIELD

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

[0002] With the continuous development of global renewable energy, electric vehicles have become a key strategy to combat climate change and promote sustainable development. As an important part of energy structure transformation, electric vehicles are a strategic measure to promote social and economic development in a more green and sustainable direction, and their market share is expanding. However, the diversification of the electric vehicle market also presents new challenges. Different models and brands of electric vehicles require different voltage levels to meet their charging and operating needs. Therefore, DC / DC converters with wide voltage regulation capability are needed to achieve DC voltage output and flexible voltage regulation in DC power systems to meet the charging needs of different vehicle models. Traditional DC / DC voltage regulation methods mainly include adjusting the switching frequency and adjusting the duty cycle of the switching device. CN 100421342C adjusts the output voltage by changing the on-off frequency of the input switching tube, but when the switching frequency is too high, the DC / DC converter may lose soft switching, resulting in reduced efficiency, and when the switching frequency is too low, the output voltage performance is poor. CN 112928919 A adds additional active switching devices on the secondary side to achieve voltage regulation by the on-off duty cycle of the secondary side switching device, but this method requires additional active devices, making the circuit structure and control method more complex and increasing the size 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

[0004] To overcome the above-mentioned deficiencies in the prior art, the application provides a DC / DC conversion unit with wide voltage regulation capability. The DC / DC conversion unit of the application uses switching frequency adjustment to achieve output voltage regulation, and can achieve soft switching in the full load range within a wide output voltage range.

[0005] The purpose of the application is achieved by 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 , a primary resonant capacitor, a secondary resonant capacitor, a clamping diode, a transformer, and a rectifier unit, wherein:

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

[0008] The direct current capacitor includes an input filter capacitor C i and an output filter capacitor C o ;

[0009] The primary side resonance capacitor includes a first primary side resonance capacitor C p1 and a second primary side resonance capacitor C p2 ;

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

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

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

[0013] The positive pole of the input end is connected to the collector of the first switch tube S1 and the positive pole of the first primary side resonance capacitor C i respectively through the positive pole of the input filter capacitor C p1 , and the negative pole of the input end is connected to the emitter of the second switch tube S2 and the negative pole of the second primary side resonance capacitor C i respectively through the negative pole of the input filter capacitor C p2 , and the two ends of the input filter capacitor C i constitute a direct current input end;

[0014] The positive pole of the first clamping diode D p1 is connected to the positive pole of the first primary side resonance capacitor C p1 , and the negative pole of the first clamping diode D p1 is connected to the negative pole of the first primary side resonance capacitor C p1 ;

[0015] The positive pole of the second clamping diode D p2 is connected to the positive pole of the second primary side resonance capacitor C p2 , and the negative pole of the second clamping diode D p1 is connected to the negative pole of the second primary side resonance capacitor C p2 ;

[0016] The same-named end of the primary side of the transformer is connected to the middle node of the first switch tube S1 and the second switch tube S2 through the resonance inductor L r , and the other end is connected to the middle node of the first primary side resonance capacitor C p1 and the second primary side resonance capacitor C p2 ;

[0017] The secondary side of the transformer is connected to the midpoint between the first diode D1 and the third diode D3, and the other end is connected to the midpoint between the second diode D2 and the fourth diode D4.

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

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

[0020] The positive terminal of the output is connected to the output filter capacitor C. o The positive terminal is connected to the cathode of the first diode D1 and the cathode of the second diode D2, and the negative terminal of the output terminal is connected to the output filter capacitor C. o The negative terminal 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 to existing DC / DC voltage regulation schemes that rely on frequency and duty cycle adjustment, the DC / DC converter unit of this invention, with its wide voltage regulation capability, can achieve soft switching across the entire load range within a wider output voltage range. Simultaneously, the pulse width and time of the positive and negative voltages are fixed during frequency regulation, simplifying the control method and effectively reducing the transformer's operating magnetic flux density, thereby reducing the transformer's size. Therefore, the DC transformer of this invention features small size, high efficiency, and a wide voltage regulation range, making it highly suitable for electric vehicle charging scenarios. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the DC / DC converter unit with wide voltage regulation capability described in this invention. i I is the DC input voltage. i U is the DC input current. o For DC output voltage, I o This is the DC output current;

[0024] Figure 2 This is a schematic diagram of typical drive and voltage / current waveforms of the DC / DC converter unit with wide voltage regulation capability described in this invention.

[0025] Figure 3 This is a schematic diagram of the current path of the circuit topology described in this invention operating in the first switching mode.

[0026] Figure 4This is a schematic diagram of the current path of the circuit topology described in this invention operating in the second switching mode;

[0027] Figure 5 This is a schematic diagram of the current path of the circuit topology described in this invention operating in the third switching mode;

[0028] Figure 6 The simulation waveforms of the resonant current and output voltage of the circuit topology described in this invention are shown.

[0029] Figure 7 This is a derived illustration of the topology proposed in this invention. Figure 1 ;

[0030] Figure 8 This is a derived illustration of the topology proposed in this invention. Figure 2 ;

[0031] Figure 9 This is a derived illustration of the topology proposed in this invention. Figure 3 . Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0033] This invention provides a DC / DC converter unit with wide voltage regulation capability, such as... Figure 1 As shown, the input voltage of the DC / DC converter unit is U. i The output voltage is U o Includes half-bridge unit, DC capacitor, resonant inductor L r The components include a primary resonant capacitor, a secondary resonant capacitor, a clamping diode, a transformer, and a rectifier unit, among which:

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

[0035] DC capacitors include the input filter capacitor C. i and output filter capacitor C o ;

[0036] The primary-side resonant capacitor includes the first primary-side resonant capacitor C. p1 Second primary resonant capacitor C p2 ;

[0037] The secondary resonant capacitor includes the first secondary resonant capacitor C. s1 Secondary resonant capacitor C s2 ;

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

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

[0040] The positive pole of the input end is connected to the anode of the input filter capacitor C i respectively, and the negative pole of the input end is connected to the cathode of the input filter capacitor C p1 respectively. i The positive pole of the input end is connected to the anode of the input filter capacitor C p2 respectively, and the negative pole of the input end is connected to the cathode of the input filter capacitor C i ;

[0041] The positive pole of the first clamping diode D p1 is connected to the anode of the first primary resonant capacitor C p1 , and the negative pole of the first clamping diode D p1 is connected to the cathode of the first primary resonant capacitor C p1 ;

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

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

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

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

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

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

[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 rectification unit is a full-bridge rectification structure, a voltage-doubling rectification structure, a multi-voltage-doubling rectification 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. The method includes the following steps:

[0051] As Figures 2-5 shown, the first switching tube S1 and the second switching tube S2 operate complementaryly with a 50% duty cycle. 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 rectifier diode D1 is turned on, the second rectifier diode D2, the third rectifier diode D3 and the fourth rectifier diode D4 are reverse-biased and turned off, the primary resonance capacitor and the secondary resonance capacitor are connected in series to form an equivalent resonance capacitor, and the resonance inductor L r and the equivalent resonance capacitor start to resonate, and the primary side current i p 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 resonance capacitor C Cp1 drops to 0, the first clamping diode D p1 is turned on, the first primary resonance capacitor C p1 and the second primary resonance capacitor C p2The voltage of the transformer primary side remains unchanged; the first switch S1 is in the on state, and the second switch S2 is in the off state; the first rectifier diode D1 is on, and the second rectifier diode D2, the third rectifier diode D3, and the fourth rectifier diode D4 bear reverse voltage and are off; the voltage u p is nU o , the transformer primary side current i p decreases linearly from I p (t1) to zero;

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

[0057] II. Second half cycle

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

[0059] Moment t3: t3 is the starting point of the second half control cycle, at this moment, the value of the transformer secondary side current i r flowing through the resonant inductor L p1 is zero, at this moment, the third switch S2 is turned on, the voltage of the first primary resonant capacitor C p2 and the voltage of the second primary resonant capacitor C o are respectively equal to zero and the voltage U o across the output filter capacitor C r ;

[0060] The fourth switch mode: when t3≤t<t4, at the moment t3, the first switch S1 is in the off state, the second switch S2 is in the on state, the third rectifier diode D3 is on, the first rectifier diode D1, the second rectifier diode D2, and the fourth rectifier diode D4 bear reverse voltage and are off, the primary resonant capacitor and the secondary resonant capacitor form an equivalent resonant capacitor in series, the resonant inductor L p and the equivalent resonant capacitor start to resonate, and the transformer primary side current i p2 increases from zero according to a sinusoidal function;

[0061] The fifth switch mode: when t4≤t<t5, at the moment t4, the voltage u Cp2 of the second primary resonant capacitor C p2 decreases to 0, the second clamping diode D p1 is on, the first 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 rectifying diode D2 and the third rectifying diode D3 are conducting, and the first rectifying diode D1 and the fourth rectifying diode D4 are reverse-biased and turned 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);

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

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

[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:

[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 can be 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 regulation of the output voltage can still be achieved.

[0072] From Figure 8It can be seen that the three-level NPC half-bridge replaces the two-level half-bridge of the primary side of the transformer, and the control and wide-range adjustment of the output voltage can still be realized.

[0073] By Figure 9 It can be seen that the series half-bridge structure replaces the two-level half-bridge of the primary side of the transformer, and the control and wide-range adjustment of the output voltage can still be realized.

Claims

1. A method of operating a DC / DC conversion unit having a wide voltage regulation capability, characterized by, The method utilizes a DC / DC conversion unit for wide voltage regulation, the DC / DC conversion unit comprising a half-bridge unit, a direct-current capacitor, a resonant inductor L r , a primary resonant capacitor, a secondary resonant capacitor, a clamping diode, a transformer and a rectification unit, wherein: The half-bridge unit comprises a first switch S1 and a second switch S2; The direct current capacitor comprises an input filter capacitor C i and an output filter capacitor C o ; The primary side resonance capacitor includes a first primary side resonance capacitor C p1 and a second primary side resonance capacitor C p2 ; The secondary side resonant capacitor includes a first secondary side resonant capacitor C s1 and a second secondary side resonant capacitor C s2 ; The clamping diode comprises a first clamping diode D p1 and a second clamping diode D p2 ; The rectifier unit comprises a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4; The positive pole of the input end is connected with the collector of the first switch tube S1 and the positive pole of the first primary side resonance capacitor C i The positive pole of the input end is connected with the collector of the first switch tube S1 and the positive pole of the first primary side resonance capacitor C p1 The negative pole of the input end is connected with the emitter of the second switch tube S2 and the negative pole of the second primary side resonance capacitor C i The negative pole of the input end is connected with the emitter of the second switch tube S2 and the negative pole of the second primary side resonance capacitor C p2 The negative pole of the input end is connected with the emitter of the second switch tube S2 and the negative pole of the second primary side resonance capacitor C i The two ends of the input filter capacitor C a first clamp diode D p1 a cathode of the first clamp diode D is connected to a negative pole of the first primary resonant capacitor C p1 a positive pole of the first clamp diode D is connected to a positive pole of the first primary resonant capacitor C p1 a anode of the first clamp diode D is connected to a positive pole of the first primary resonant capacitor C p1 a negative pole of the first clamp diode D is connected to a negative pole of the first primary resonant capacitor C the cathode of the second clamp diode D p2 the anode of the second clamp diode D p2 the cathode of the second clamp diode D p1 the anode of the second clamp diode D p2 the cathode of the second clamp diode D The primary side same name end of the transformer is connected with the resonant inductor L r The intermediate node of connecting the first switch tube S1 and the second switch tube S2, the other end is connected with the first primary side resonant capacitor C p1 The intermediate node of connecting the first switch tube S1 and the second switch tube S2, the other end is connected with the first primary side resonant capacitor C p2 The intermediate node of connecting the first switch tube S1 and the second switch tube S2, the other end is connected with the first primary side resonant capacitor C The transformer secondary side connects the intermediate node of the first diode D1 and the third diode D3 at one end, and connects the intermediate node of the second diode D2 and the fourth diode D4 at the other end; One end of the first secondary side resonance capacitor C s1 is connected to the cathode of the second diode D2, and the other end of the first secondary side resonance capacitor C s1 is connected to the anode of the second diode D2. The second sub-edge resonance capacitor C s2 one end is connected with the cathode of the fourth diode D4, and the other end is connected with the anode of the fourth diode D4; The positive pole of the output end is connected with the anode of the first diode D1 and the anode of the second diode D2 through the output filter capacitor C o The negative pole of the output end is connected with the cathode of the third diode D3 and the cathode of the fourth diode D4 through the output filter capacitor C o The negative pole of the output end is connected with the cathode of the third diode D3 and the cathode of the fourth diode D4 through the output filter capacitor C The method comprises the following steps: The first switch S1 and the second switch S2 are operated complementarily with a duty cycle of 50%, and a control period is T, and the time is t0≤t≤t6, wherein t0≤t≤t3 is the first half period, and t3≤t≤t6 is the second half period, and the following conditions are met: I. The first half period t0 is set as the initial time, and is the starting point of a control period, and the first switch S1 is turned on at the initial time t0; The first switch mode: when t0≤t<t1, at t0 moment, the first switch tube S1 is in the conducting state, the second switch tube S2 is in the off state, the first rectifier diode D1 is turned on, the second rectifier diode D2, the third rectifier diode D3 and the fourth rectifier diode D4 bear reverse voltage and are turned off, the primary side resonant capacitor and the secondary side resonant capacitor are connected in series to form an equivalent resonant capacitor, and the resonant inductor L r The equivalent resonant capacitor starts to resonate with the transformer primary side current i p Increases according to the sine function law from zero; Second switching mode: when t1 ≤ t < t2, at time t1, the voltage u of the first primary resonant capacitor C p1 drops to 0, the first clamping diode D Cp1 conducts, and the voltage of the first primary resonant capacitor C p1 and that of the second primary resonant capacitor C p1 remain 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 of the primary winding of the transformer p is nU o , and the current i of the primary side of the transformer p drops linearly from I p (t1);​​ The third switch mode: when t2≤t<t3, at t2 moment, the value of transformer secondary side current i s linearly decreases to zero, and the secondary side diode realizes zero-current turn-off. II. The second half period The control period waveform of the second half period is symmetrical to that of the first half period, and the specific control method is as follows: Time t3: t3 is the start of the second half of the control period, at this time the transformer secondary side current, that is, the current through the resonant inductor L r is zero, at this time the second switch S2 is turned on, the first primary side resonant capacitor C p1 Voltage and the second primary side resonant capacitor C p2 Voltage is equal to zero and the output filter capacitor C o The voltage U o ; The fourth switch mode: when t3≤t<t4, at t3 moment, the first switch tube S1 is in the off state, the second switch tube S2 is in the on state, the third rectifier diode D3 is conducted, the first rectifier diode D1, the second rectifier diode D2 and the fourth rectifier diode D4 bear reverse voltage and are turned off, the primary side resonant capacitor and the secondary side resonant capacitor are connected in series to form an equivalent resonant capacitor, and the resonant inductor L r The equivalent resonant capacitor starts to resonate with the transformer primary side current i p Increases according to the sine function rule from zero. The fifth switch mode: t4≤t<t5, the second primary side resonant capacitor C p2 Voltage u Cp2 Down to 0, the second clamping diode D p2 Conduct, the first primary side resonant capacitor C p1 And the voltage of the second primary side resonant capacitor C p2 Remains unchanged; the first switch S1 is in the off state, and the second switch S2 is in the on state; the second rectifier diode D2 and the third rectifier diode D3 are on, and the first rectifier diode D1 and the fourth rectifier diode D4 are off under reverse voltage; the primary side winding voltage u p Of the transformer is nU o , the primary side current i p Of the transformer is I p (t1) decreases linearly; The sixth switch mode: when t5≤t<t6, at t5 moment, the transformer secondary side current i s linearly decreases to zero, and the secondary side diode realizes zero-current turn-off.

2. The operation control method of a DC / DC conversion unit having a wide voltage regulation capability according to claim 1, characterized by, 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 operation control method of a DC / DC conversion unit having a wide voltage regulation capability according to claim 1, characterized by, 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. The operation control method of a DC / DC conversion unit having a wide voltage regulation capability according to claim 1, characterized by, The DC / DC conversion unit has the characteristics of a power source, and the transmission power of the DC / DC conversion unit is: wherein, is the switching frequency, is the input voltage, is the primary resonant capacitance value.

5. The operation control method of a DC / DC conversion unit having a wide voltage regulation capability according to claim 1, characterized by, The output voltage of the DC / DC conversion unit is: wherein, is the switching frequency, is the input voltage, is the primary resonant capacitance value, is the load resistance value.

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