A high-power inductive load dual-tube Buck-Boost converter and its three-mode switching method

Abstract

The invention discloses a high-power inductive load dual-tube Buck-Boost converter, comprising a DC bus, a first IGBT tube S1, a second IGBT tube S2, a first diode D1, a second diode D2, a filter inductor Lf, an output filter capacitor Co and an inductive load; the positive terminal of the DC bus is connected to the collector of the first IGBT tube S1, and the negative terminal of the DC bus is connected to the anode of the first diode D1, the lower terminal of the output filter capacitor Co and the lower terminal of the inductive load; the emitter of the first IGBT tube S1 is connected to the cathode of the first diode D1 and the left terminal of the filter inductor; the collector of the second IGBT tube S2 is connected to the anode of the second diode D2 and the right terminal of the filter inductor; the cathode of the second diode D2 is connected to the upper terminal of the output filter capacitor Co and the upper terminal of the inductive load; a corresponding three-mode switching method is also disclosed; taking into account the application scenario of the high-power inductive load in detail, the modal stability switching of the dual-tube Buck-Boost converter in the process of generating the inductive load current pulse is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronics, and in particular relates to a three-mode switching method for a high-power inductive load dual-tube Buck-Boost circuit. Background Art

[0002] The dual-tube Buck-Boost converter has become a widely used DC / DC converter in recent years due to its advantages such as low switching loss and wide output voltage gain conversion range. The dual-tube Buck-Boost converter device with high-power inductive load has also become the core component of equipment such as strong magnetic field generators and geophysical detection magnetic field transmitters.

[0003] Large inductive loads have large time constants and high power levels. In the process of the inductive load current reaching a steady state and generating the required magnetic field, the output voltage range of the dual-tube Buck-Boost converter is wide, and there is a process of unidirectional increase in voltage gain and unidirectional decrease in voltage gain. Therefore, this places high demands on the stability of the dual-tube Buck-Boost converter during the mode switching process. Since the existing dual-tube Buck-Boost converter mode switching strategy does not take into account the application scenarios of high-power inductive loads in detail, the output voltage is unstable due to a series of factors such as gain jump and control loop instability during the mode switching process. Therefore, how to make the dual-tube Buck-Boost converter switch mode stably in the process of generating inductive load current pulses is a problem that urgently needs to be solved. Summary of the invention

[0004] The present invention aims to solve the problem that the existing dual-tube Buck-Boost converter mode switching strategy does not take into account the application scenario of high-power inductive load in detail, and the output voltage is unstable due to a series of factors such as gain jump and control loop instability during the mode switching process.

[0005] In view of the above problems, the technical solution adopted by the present invention is: a high-power inductive load dual-tube Buck-Boost converter, including a DC bus, a first IGBT tube S1, a second IGBT tube S2, a first diode D1, a second diode D2, a filter inductor Lf, an output filter capacitor Co and an inductive load; the positive terminal of the DC bus is connected to the collector of the first IGBT tube S1, and the negative terminal of the DC bus is connected to the anode of the first diode D1, the lower terminal of the output filter capacitor Co, and the lower terminal of the inductive load; the emitter of the first IGBT tube S1 is connected to the cathode of the first diode D1 and the left terminal of the filter inductor; the collector of the second IGBT tube S2 is connected to the anode of the second diode D2 and the right terminal of the filter inductor; the cathode of the second diode D2 is connected to the upper terminal of the output filter capacitor Co and the upper terminal of the inductive load.

[0006] A three-mode switching method for a high-power inductive load dual-tube Buck-Boost converter comprises the following steps:

[0007] Step 1: Obtain the voltage gain K of the control loop connected to the dual-tube Buck-Boost converter; obtain the maximum value K of the required output voltage gain OO1 With the minimum gain K OO2 ;

[0008] Step 2: Set the duty cycle of the PWM drive signal of the first IGBT tube S1 to d1; the duty cycle of the PWM drive signal of the second IGBT tube S2 to d2. The drive signal blind area between the first IGBT tube S1 and the second IGBT tube S2 is Δd;

[0009] Step 3: Set the critical gain K for switching between Boost and Buck-Boost modes 1m ; Set the second critical gain K for Buck and Buck-Boost mode switching 2m ;

[0010] Step 4: Set the mode switching hysteresis width ΔM; set the gain rise stage to enter the start point R of the Buck-Boost mode hysteresis comparator r_bb =K 2m +ΔM; Set the gain rising stage and enter the start point R of the Boost mode hysteresis comparator r_bo =K 1m +ΔM; Set the gain reduction stage and enter the start point R of the Buck-Boost mode hysteresis comparator d_bb =K 1m -ΔM; Set the gain reduction stage and enter the start point R of the Buck mode hysteresis comparator d_bu=K 2m -ΔM; set the mode flags flag_buckboost, flag_boost, flag_buck, and the initial values ​​are all zero;

[0011] Step 5: When the converter operates in a state where the gain increases unidirectionally and the initial operating mode is the Buck mode, and when the converter operates in a state where the gain decreases unidirectionally and the initial operating mode is the Boost mode, the values ​​of the PWM drive signal duty cycle d1 of the first IGBT tube S1 and the PWM drive signal duty cycle d2 of the second IGBT tube S2 are determined by comparing the value of the mode flag and the size of the voltage gain, thereby realizing the mode switching of the inductive load dual-tube Buck-Boost converter.

[0012] Furthermore, in step 3, the gain K 1m With gain K 2m The value should satisfy K 1m =K OO1 *m,K 2m =K OO2 *1 / m; where m is the gain adjustment factor, which should be appropriately selected according to the output voltage gain range in the case of high-power inductive loads.

[0013] Furthermore, within a certain time range, the converter operates in a working state where the gain increases unidirectionally and the initial operating mode is the Buck mode, or the gain decreases unidirectionally and the initial operating mode is the Boost mode.

[0014] Furthermore, without considering the influence of the hysteresis comparator, the duty cycle of the PWM drive signal of the first IGBT tube S1 is d1, and the duty cycle of the PWM drive signal of the second IGBT tube S2 is d2, respectively:

[0015]

[0016]

[0017] K is the voltage gain, Δd is the driving signal blind area of ​​the first IGBT tube S1 and the second IGBT tube S2, K 1m K is the first critical gain for switching between Boost and Buck-Boost modes; 2m It is the second critical gain for switching between Buck and Buck-Boost modes.

[0018] Furthermore, when the converter operates in a state where the gain increases unidirectionally and the initial operating mode is the Buck mode, when the voltage gain K is greater than the start point R of the Buck-Boost mode hysteresis comparator, r_bbWhen the voltage gain K is greater than the start point R of the Boost mode hysteresis comparator, the mode flag flag_buckboost is set to 1. r_bo When the mode flag flag_boost is set to 1;

[0019] When the converter is operating in a state where the gain is decreasing unidirectionally and the initial operating mode is the Boost mode, when the voltage gain K is less than the start point R of the Buck-Boost mode hysteresis comparator, d_bb When the mode flag flag_buckboost is set to 1; when the voltage gain K is less than the start point R of the Buck mode hysteresis comparator d_bu When the mode flag flag_buck is set to 1.

[0020] Furthermore, when the converter operates in a state where the gain increases unidirectionally and the initial operating mode is the Buck mode, the control method includes the following steps:

[0021] Step 1: When the mode flag flag_buckboost is equal to 0, compare the voltage gain K; if K>K 2m , then d1 takes K 2m , d2 is 0; if K≤K 2m , then the value is obtained according to formula (1) and (2);

[0022] Step 2: When the mode flag flag_buckboost is equal to 1, compare the voltage gain K; if K ≤ K 2m , then d1 takes K 2m (1-Δd), d2 takes Δd; if K 2m <K≤K 1m , then the value is determined according to formulas (1) and (2); if K>K 1m , then d1 is (1-Δd), d2 is 1-(1-Δd) / K 1m ;

[0023] Step 3: When the mode flag flag_boost is equal to 1, compare the voltage gain K; if K≤K 1m , then d1 is 1, d2 is 1-1 / K 1m ; if K>K 1m , then the value is obtained according to formulas (1) and (2);

[0024] By executing steps 1, 2, and 3 in this way, the high-power inductive load dual-tube Buck-Boost converter can smoothly perform mode switching during the process of unidirectional gain increase.

[0025] Furthermore, when the converter operates in a state where the gain decreases unidirectionally and the initial operating mode is the Boost mode, the control method includes the following steps:

[0026] Step 1: When the mode flag flag_buckboost is equal to 0, compare the voltage gain K; if K>K 1m , then the value is obtained according to formulas (1) and (2); if K≤K 1m , then d1 is 1, d2 is 1-1 / K 1m ;

[0027] Step 2: When the mode flag flag_buckboost is equal to 1, compare the voltage gain K; if K ≤ K 2m , then d1 takes K 2m (1-Δd), d2 takes Δd; if K 2m <K≤K 1m , then the value is determined according to formulas (1) and (2); if K>K 1m , then d1 is (1-Δd), d2 is 1-(1-Δd) / K 1m ;

[0028] Step 3: When the mode flag flag_buck is equal to 1, compare the voltage gain K; if K≤K 2m , according to formula (1) and (2); if K>K 2m , then d1 takes K 2m , d2 is 0;

[0029] By executing steps 1, 2, and 3 in this way, the high-power inductive load dual-tube Buck-Boost converter can smoothly perform mode switching during the process of unidirectional gain reduction.

[0030] The beneficial effects and features of the present invention are:

[0031] (1) The three-mode switching method of the high-power inductive load dual-tube Buck-Boost converter of the present invention; takes into account the application scenarios of high-power inductive loads in detail; realizes the stable mode switching of the dual-tube Buck-Boost converter in the process of generating inductive load current pulses; and effectively improves the problems of output voltage instability caused by a series of factors such as gain jump and control loop instability during the mode switching process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A dual-tube Buck-Boost circuit and its load used in the mode switching method of the present invention;

[0033] Figure 2 This is a working point trajectory diagram of a dual-tube Buck-Boost circuit ignoring the hysteresis comparator during the mode switching process;

[0034] Figure 3A schematic diagram of a three-mode switching method for a high-power inductive load dual-tube Buck-Boost circuit;

[0035] Figure 4 The following is a simulation waveform diagram of an application example of a three-mode switching method for a high-power inductive load dual-tube Buck-Boost circuit.

[0036] Figure 5 It is a simulation waveform diagram of an application example of the three-mode switching method of the high-power inductive load dual-tube Buck-Boost circuit of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, the present invention relates to a dual-tube Buck-Boost converter for high-power inductive loads. The dual-tube Buck-Boost converter and its load include a DC bus, a first IGBT tube S1, a second IGBT tube S2, a first diode D1, a second diode D2, a filter inductor Lf, an output filter capacitor Co and an inductive load. The positive terminal of the DC bus is connected to the collector of the first IGBT tube S1, and the negative terminal of the DC bus is connected to the anode of the first diode D1, the lower terminal of the output filter capacitor Co, and the lower terminal of the inductive load; the emitter of the first IGBT tube S1 is connected to the cathode of the first diode D1 and the left terminal of the filter inductor; the collector of the second IGBT tube S2 is connected to the anode of the second diode D2 and the right terminal of the filter inductor; the cathode of the second diode D2 is connected to the upper terminal of the output filter capacitor Co and the upper terminal of the inductive load.

[0039] Within a certain time range, the converter operates in a working state where the gain increases unidirectionally and the initial operating mode is the Buck mode, or the gain decreases unidirectionally and the initial operating mode is the Boost mode.

[0040] like Figure 2 As shown in the figure, without considering the influence of the hysteresis comparator, the operating point operation trajectory of the dual-tube Buck-Boost circuit during the mode switching process. 1 -DCBAO 2That is the running track of the working point. According to this track, the gain will not change suddenly during the mode switching process under the ideal working state. Using the working track diagram, it can be concluded that the duty cycle of the PWM drive signal of the first IGBT tube S1 is d1, and the duty cycle of the PWM drive signal of the second IGBT tube S2 is d2. The calculation formulas are:

[0041]

[0042]

[0043] K is the voltage gain, Δd is the driving signal blind area of ​​the first IGBT tube S1 and the second IGBT tube S2, K 1m K is the first critical gain for switching between Boost and Buck-Boost modes; 2m It is the second critical gain for switching between Buck and Buck-Boost modes.

[0044] When the converter operates in a state where the gain increases unidirectionally and the initial operating mode is Buck mode, when the voltage gain K is greater than the start point R of the Buck-Boost mode hysteresis comparator, r_bb When the voltage gain K is greater than the start point R of the Boost mode hysteresis comparator, the mode flag flag_buckboost is set to 1. r_bo When the mode flag flag_boost is set to 1.

[0045] When the converter is operating in a state where the gain is decreasing unidirectionally and the initial operating mode is the Boost mode, when the voltage gain K is less than the start point R of the Buck-Boost mode hysteresis comparator, d_bb When the mode flag flag_buckboost is set to 1; when the voltage gain K is less than the start point R of the Buck mode hysteresis comparator d_bu When the mode flag flag_buck is set to 1.

[0046] like Figure 3-Figure 4 , as shown, a flow chart of the control method is given under two conditions: one is when the converter operates in a state where the voltage gain increases unidirectionally and the initial operating mode is the Buck mode, and the other is when the converter operates in a state where the voltage gain decreases unidirectionally and the initial operating mode is the Boost mode.

[0047] like Figure 5As shown in FIG. 1 , it is a simulation waveform diagram of an application example of the three-mode switching method of the high-power inductive load dual-tube Buck-Boost circuit of the present invention. The waveform diagram includes the current output voltage gain K, the PWM drive signal of the first IGBT tube S1, and the PWM drive signal of the second IGBT tube S2. It can be seen from the figure that in the mode switching process of increasing the voltage gain and decreasing the voltage gain, the gain always maintains a stable change.

[0048] The present invention proposes a three-mode switching method for a high-power inductive load dual-tube Buck-Boost circuit. The present invention solves the problem of unstable output voltage caused by a series of factors such as gain jump and unstable control loop during mode switching under high-power and high-inductive load conditions.

[0049] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the structural relationship and principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A three-mode switching method for a high-power inductive load dual-tube Buck-Boost converter, characterized in that: The steps include: Step 1: Obtain the voltage gain K of the control loop connected to the dual-tube Buck-Boost converter; obtain the maximum value K of the required output voltage gain OO1 With the minimum gain K OO2 ; Step 2: Set the duty cycle of the PWM drive signal of the first IGBT tube S1 to d1; the duty cycle of the PWM drive signal of the second IGBT tube S2 to d2. The drive signal blind area of ​​the first IGBT tube S1 and the second IGBT tube S2 is Δd; Step 3: Set the critical gain K for switching between Boost and Buck-Boost modes 1m ; Set the second critical gain K for Buck and Buck-Boost mode switching 2m ; Step 4: Set the mode switching hysteresis width ΔM; Set the gain rise stage to enter the start point R of the Buck-Boost mode hysteresis comparator r_bb =K 2m +ΔM; Set the gain rising stage and enter the start point R of the Boost mode hysteresis comparator r_bo =K 1m +ΔM; Set the gain reduction stage to enter the start point R of the Buck-Boost mode hysteresis comparator d_bb =K 1m -ΔM; Set the gain reduction stage to enter the start point R of the Buck mode hysteresis comparator d_bu =K 2m -ΔM; set the mode flags flag_buckboost, flag_boost, flag_buck, and the initial values ​​are all zero; Step 5: When the converter operates in a state where the gain increases unidirectionally and the initial operating mode is the Buck mode, and when the converter operates in a state where the gain decreases unidirectionally and the initial operating mode is the Boost mode, the values ​​of the PWM drive signal duty cycle d1 of the first IGBT tube S1 and the PWM drive signal duty cycle d2 of the second IGBT tube S2 are determined by comparing the value of the mode flag and the size of the voltage gain, so as to realize the mode switching of the inductive load dual-tube Buck-Boost converter; The high-power inductive load dual-tube Buck-Boost converter used in the above method includes a DC bus, a first IGBT tube S1, a second IGBT tube S2, a first diode D1, a second diode D2, a filter inductor Lf, an output filter capacitor Co and an inductive load; the positive terminal of the DC bus is connected to the collector of the first IGBT tube S1, and the negative terminal of the DC bus is connected to the anode of the first diode D1, the lower terminal of the output filter capacitor Co, and the lower terminal of the inductive load; the emitter of the first IGBT tube S1 is connected to the cathode of the first diode D1 and the left terminal of the filter inductor; the collector of the second IGBT tube S2 is connected to the anode of the second diode D2 and the right terminal of the filter inductor; the cathode of the second diode D2 is connected to the upper terminal of the output filter capacitor Co and the upper terminal of the inductive load.

2. The three-mode switching method of the high-power inductive load dual-tube Buck-Boost converter according to claim 1 is characterized in that : In step 3, the gain K 1m With gain K 2m The value should satisfy K 1m =(K OO1 -1)*m+K OO1 ,K 2m =(1-K OO2 )*m+K OO2 ; Wherein, m is the gain adjustment coefficient, and in the case of high-power inductive load, the value is 0.

3.

3. The three-mode switching method of the high-power inductive load dual-tube Buck-Boost converter according to claim 1 is characterized in that : The converter operates in a working state where the gain increases unidirectionally and the initial operating mode is the Buck mode, or the gain decreases unidirectionally and the initial operating mode is the Boost mode.

4. The three-mode switching method of the high-power inductive load dual-tube Buck-Boost converter according to claim 1 is characterized in that Without considering the influence of the hysteresis comparator, the duty cycle of the PWM drive signal of the first IGBT tube S1 is d1, and the duty cycle of the PWM drive signal of the second IGBT tube S2 is d2, respectively: K is the voltage gain, Δd is the driving signal blind area of ​​the first IGBT tube S1 and the second IGBT tube S2, K 1m K is the first critical gain for switching between Boost and Buck-Boost modes; 2m It is the second critical gain for switching between Buck and Buck-Boost modes.

5. The three-mode switching method of the high-power inductive load dual-tube Buck-Boost converter according to claim 1 is characterized in that : When the converter operates in a state where the gain increases unidirectionally and the initial operating mode is Buck mode, when the voltage gain K is greater than the start point R of the Buck-Boost mode hysteresis comparator, r_bb When the voltage gain K is greater than the start point R of the Boost mode hysteresis comparator, the mode flag flag_buckboost is set to 1. r_bo When the mode flag flag_boost is set to 1; When the converter is operating in a state where the gain is decreasing unidirectionally and the initial operating mode is the Boost mode, when the voltage gain K is less than the start point R of the Buck-Boost mode hysteresis comparator, d_bb When the mode flag flag_buckboost is set to 1; when the voltage gain K is less than the start point R of the Buck mode hysteresis comparator d_bu When the mode flag flag_buck is set to 1.

6. The three-mode switching method of the high-power inductive load dual-tube Buck-Boost converter according to claim 4 is characterized in that When the converter is operating in a state where the gain increases unidirectionally and the initial operating mode is the Buck mode, the switching method comprises the following steps: Step 1: When the mode flag flag_buckboost is equal to 0, compare the voltage gain K; if K>K 2m , then d1 takes K 2m , d2 is 0; if K≤K 2m , then the value is obtained according to formula (1) and (2); Step 2: When the mode flag flag_buckboost is equal to 1, compare the voltage gain K; if K ≤ K 2m , then d1 takes K 2m (1-Δd), d2 takes Δd; if K 2m <K≤K 1m , then the value is determined according to formulas (1) and (2); if K>K 1m , then d1 is (1-Δd), d2 is 1-(1-Δd) / K 1m ; Step 3: When the mode flag flag_boost is equal to 1, compare the voltage gain K; if K≤K 1m , then d1 is 1, d2 is 1-1 / K 1m ; if K>K 1m , then the value is obtained according to formulas (1) and (2); By executing steps 1, 2, and 3 in this way, the high-power inductive load dual-tube Buck-Boost converter can smoothly perform mode switching during the process of unidirectional gain increase.

7. The three-mode switching method of the high-power inductive load dual-transistor Buck-Boost converter according to claim 4 is characterized in that: In a state where the converter operates in a state where the gain is unidirectionally reduced and the initial operating mode is a Boost mode, the switching method comprises the following steps: Step 1: When the mode flag flag_buckboost is equal to 0, compare the voltage gain K; if K>K 1m , then the value is obtained according to formulas (1) and (2); if K≤K 1m , then d1 is 1, d2 is 1-1 / K 1m ; Step 2: When the mode flag flag_buckboost is equal to 1, compare the voltage gain K; if K ≤ K 2m , then d1 takes K 2m (1-Δd), d2 takes Δd; if K 2m <K≤K 1m , then the value is determined according to formulas (1) and (2); if K>K 1m , then d1 is (1-Δd), d2 is 1-(1-Δd) / K 1m ; Step 3: When the mode flag flag_buck is equal to 1, compare the voltage gain K; if K≤K 2m , then the value is determined according to formulas (1) and (2); if K>K 2m , then d1 takes K 2m , d2 is 0; By executing steps 1, 2, and 3 in this way, the high-power inductive load dual-tube Buck-Boost converter can smoothly perform mode switching during the process of unidirectional gain reduction.

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