Charge balancing control method and charge balancing controller for DCM Flyback converter

Abstract

The present invention belongs to the field of power electronics technology, and specifically relates to a charge balancing control method and a charge balancing controller for a DCM Flyback converter, comprising: completing charge balancing control within two switching cycles, wherein the following steps are performed in each switching cycle: based on the input and output of the converter in the current switching cycle obtained by sampling, calculating the output charge Q of the converter to the output capacitor when the duty cycle of the current switching cycle is high ch At the same time, the output voltage v of the converter after two switching cycles is estimated based on #imgabs0# ext , where v out and #imgabs1# are respectively the current switching cycle obtained by sampling at Q ch =0 when the output voltage and its changes; based on Q ch 、v ext And the reference voltage v ref , according to Q ref =C(v ref ‑v ext )‑Q ob Calculate the reference charge Q ref , used for calculating the duty cycle of the digital pulse width modulation signal to control the switch of the converter in the next switching cycle. The present invention estimates the output voltage after two switching cycles, which is used to calculate the reference charge of the next switching cycle without hysteresis, and improves the transient response to circuit disturbances.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and more specifically, relates to a charge balancing control method and a charge balancing controller for a DCM Flyback converter. Background Art

[0002] Flyback converters are widely used in the industrial field because of their simple scheme, small size and electrical isolation characteristics. The converter can operate in continuous conduction mode (CCM) or discontinuous conduction mode (DCM). Both modes have their own advantages and disadvantages. When the power level is relatively high, the Flyback converter operating in CCM mode can achieve higher efficiency and lower voltage stress than when operating in DCM mode. However, in this mode, the Flyback converter requires high magnetic inductance and large-sized transformers. In addition, since the Flyback converter transfer function at this time contains the right half plane (RHP) zero, the Flyback converter operating in CCM mode has limited bandwidth. Compared with CCM mode, the advantages of DCM mode are: only a small-sized transformer is required, the reverse recovery effect of the diode is reduced, and the elimination of the RHP zero facilitates stable control. Since the Flyback converter operating in DCM can be considered as an easily controlled current source, it is widely used in PV-AC modules and PFC systems.

[0003] In order to save the cost, power, size and improve the transient response of the converter, people are constantly exploring new methods based on the traditional converter control strategy. In order to achieve the best transient response, the voltage-based charge balance (VCB) controller is used for the Buck converter operating in CCM. This control method continuously adjusts the ON / OFF state of the main switch so that the inductor current can charge the output in the shortest time. However, when it is implemented by digital circuits, this method will reduce the performance because it requires continuous sampling and calculation. In addition, although this strategy can achieve the best dynamic response, it is only applicable to Buck converter applications. Based on this idea, average current-based charge balance control (ACCB) was proposed and used for Flyback converters. Instead of continuous sampling and calculation, the ACCB strategy is based on pulse width modulation (PWM), which performs sampling and calculation once in each switching cycle. It optimizes the transient response by calculating the appropriate duty cycle for the next switching cycle. The ACCB strategy is applicable to many different converters and can achieve the best dynamic response under PWM. However, the ACCB algorithm lags two switching cycles when calculating the reference charge, which reduces the effect of the circuit transient response. Summary of the invention

[0004] In view of the defects and improvement needs of the prior art, the present invention provides a charge balancing control method and a charge balancing controller for a DCM Flyback converter, which aims to improve the transient response to circuit disturbances.

[0005] To achieve the above object, according to one aspect of the present invention, a charge balancing control method for a DCM Flyback converter is provided, wherein the charge balancing control is completed within two switching cycles, wherein the following steps are performed in each switching cycle:

[0006] Based on the input and output of the DCM Flyback converter in the current switching cycle obtained by sampling, the output charge Q of the Flyback converter to the output capacitor when the duty cycle of the current switching cycle is high is calculated. ch , and according to Estimate the output voltage v of the Flyback converter after two switching cycles ext , where v out and The current switching cycle is sampled at Q ch = The output voltage and output voltage change when 0, T is the duration of a single switching cycle;

[0007] Based on the output charge Q ch , the output voltage v ext And the reference voltage v ref , according to Q ref =C(v ref -v ext )-Q ob The calculation method is as follows: ob =Q ch , Q ch =Q ref z -1 , z -1 is the unit delay factor in the Z transform, and the reference charge Q is calculated ref , the reference charge Q ref Used to calculate the duty cycle of the digital pulse width modulation signal to control the switching of the DCM Flyback converter in the next switching cycle.

[0008] Furthermore, a constant compensation factor K is used to reduce the damping effect. C , respectively correct the output charge Q ch and the reference charge Q ref , the correction method is as follows:

[0009]

[0010] In the formula, K dampIndicates the charge damping coefficient calculated and determined based on the current actual circuit.

[0011] Further, K C =K damp .

[0012] The present invention also provides a charge balancing controller for a DCM Flyback converter, comprising: a charge observer, a voltage extrapolator, a VECB algorithm module, and a charge controller;

[0013] The charge observer, the voltage extrapolator and the VECB algorithm module are used to sample the input and output of the DCM Flyback converter in each switching cycle based on digital pulse width modulation, and when the charge amount reaches the charge balance control required, perform the following functions in each switching cycle to complete the charge balance control within two switching cycles:

[0014] The charge observer is used to calculate the output charge Q of the Flyback converter to the output capacitor in the current switching cycle based on the input and output of the DCM Flyback converter in the current switching cycle. ch ;

[0015] The voltage extrapolator is used to adjust the input and output of the DCM Flyback converter based on the current switching cycle. Estimate the output voltage v of the Flyback converter after two switching cycles ext , where v out and The current switching cycle is sampled at Q ch = The output voltage and output voltage change when 0, T is the duration of a single switching cycle;

[0016] The VECB algorithm module is used to output the charge Q ch , the output voltage v ext And the reference voltage v ref , according to Q ref =C(v ref -v ext )-Q ob The calculation method is as follows: ob =Q ch , Q ch =Q ref z -1 , z -1 is the unit delay factor in the Z transform, and the reference charge Q is calculated ref , the reference charge Q ref Used to calculate the duty cycle of the digital pulse width modulation signal to control the switching of the DCM Flyback converter in the next switching cycle.

[0017] Furthermore, it also includes a correction unit for using a compensation factor K with a constant value to reduce the damping effect. C , respectively correct the output charge Q ch and the reference charge Q ref , the correction method is as follows:

[0018]

[0019] In the formula, K damp Indicates the charge damping coefficient calculated and determined based on the current actual circuit.

[0020] Further, K C =K damp .

[0021] The present invention also provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the charge balance control method for a DCM Flyback converter as described above.

[0022] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0023] (1) In order to improve the transient response to circuit disturbances, the present invention designs a voltage extrapolator based on the output voltage differential value to use the zero output charge condition to estimate the output voltage after two switching cycles. The extrapolated output voltage is used to calculate the reference charge for the next switching cycle. In this way, the reference charge can be calculated without hysteresis, thereby improving the transient response to circuit disturbances.

[0024] (2) The present invention aims at charge damping and its influence on the output voltage, and adopts a constant compensation factor in the circuit to minimize the steady-state error of the output voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of execution steps of a charge balancing control method for a DCM Flyback converter in a single switching cycle provided by an embodiment of the present invention;

[0026] Figure 2 A circuit diagram of a Flyback converter under the control of the ACCB algorithm provided in an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the output voltage and charge changes of a Flyback converter under the control of the ACCB algorithm provided in an embodiment of the present invention;

[0028] Figure 4 A circuit diagram of a Flyback controller under VECB algorithm control provided by an embodiment of the present invention;

[0029] Figure 5 A schematic diagram of the output voltage and charge changes of a Flyback converter under the control of a VECB algorithm provided in an embodiment of the present invention;

[0030] Figure 6 A circuit diagram of an accurate Flyback converter considering parasitic effects, transformer leakage inductance and RCD snubber circuit provided by an embodiment of the present invention;

[0031] Figure 7 The embodiment of the present invention provides an edge v in and v out Schematic diagram of charge damping coefficient;

[0032] Figure 8 The output voltage transient change diagram corresponding to different control algorithms when R jumps from 30Ω to 15Ω provided in the embodiment of the present invention, wherein (a) indicates the use of the PI control algorithm, (b) indicates the use of the ACCB control algorithm, and (c) indicates the use of the VECB control algorithm;

[0033] Fig. 9 The output voltage transient change diagram corresponding to different control algorithms when R jumps from 150Ω to 15Ω provided in the embodiment of the present invention, wherein (a) indicates the use of the PI control algorithm, (b) indicates the use of the ACCB control algorithm, and (c) indicates the use of the VECB control algorithm;

[0034] Fig.10 The output voltage transient change diagram corresponding to different control algorithms when Vin jumps from 10V to 7.5V provided in the embodiment of the present invention, wherein (a) indicates the use of the PI control algorithm, (b) indicates the use of the ACCB control algorithm, and (c) indicates the use of the VECB control algorithm;

[0035] Fig.11 The output voltage transient change diagram corresponding to different control algorithms when Vref jumps from 15V to 15.25V provided in the embodiment of the present invention, wherein (a) indicates the use of the PI control algorithm, (b) indicates the use of the ACCB control algorithm, and (c) indicates the use of the VECB control algorithm;

[0036] Fig.12 The output voltage transient change diagram corresponding to different control algorithms when Vref jumps from 13V to 15V provided in the embodiment of the present invention, wherein (a) represents the use of PI control algorithm, (b) represents the use of ACCB control algorithm, and (c) represents the use of VECB control algorithm. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Embodiment 1

[0039] A charge balancing control method for a DCM Flyback converter is provided, wherein the charge balancing control is completed within two switching cycles, wherein: Figure 1 As shown, the following steps are performed in each switching cycle:

[0040] Based on the input and output of the DCM Flyback converter in the current switching cycle obtained by sampling, the output charge Q of the Flyback converter to the output capacitor when the duty cycle of the current switching cycle is high is calculated. ch , and according to Estimate the output voltage v of the Flyback converter after two switching cycles ext , where v out and The current switching cycle is sampled at Q ch = The output voltage and output voltage change when 0, T is the duration of a single switching cycle;

[0041] Based on the output charge Q ch 、Output voltage v ext And the reference voltage v ref , according to Q ref =C(v ref -v ext )-Q ob The calculation method is as follows: ob =Q ch , Q ch =Q ref z -1 , z -1 is the unit delay factor in the Z transform, and the reference charge Q is calculated ref , reference charge Q ref Used to calculate the duty cycle of the digital pulse width modulation signal to control the switching of the DCM Flyback converter in the next switching cycle.

[0042] The origin of the charge balance control method of this embodiment and the rationality and advantages of the control method of this embodiment are now explained through the following description:

[0043] The Flyback converter circuit under the traditional ACCB algorithm control is as follows Figure 2As shown in the figure, d1 is the duty cycle of the digital pulse width modulation (DPWM) signal, C is the output capacitor, R is the load resistance, ADC is the digital-to-analog converter, V in Indicates the power supply voltage, Q ch The charge balance controller includes a charge observer and a charge controller. The charge observer is used to estimate the output charge Q ch , as a result of its own observation (i.e., Q ob ). ACCB algorithm module is based on Q ob , generating the appropriate Q ref Input to the charge controller as the reference for the charge controller to adjust the duty cycle d1, so that the output voltage V out Tracking V during both switching cycles ref , improving the transient response of the circuit.

[0044] That is, when the output voltage V out =V ref When the charge controller does not change the DPWM d1, the output V out Maintain constant; when the circuit is not in steady state, V out Deviation from V erf , the charge controller needs to change DPWM d1 so that V out Approaching V ref The ACCB algorithm module will detect V out Whether it deviates from V ref To control the operation of the charge controller: if a deviation occurs, the Q calculated by the charge observer ob To calculate the appropriate Q ref Send it to the charge controller and let the charge controller recalculate d1.

[0045] Regarding the ACCB algorithm, assuming that Q ch Tracking Q ref , the output voltage can be ref In addition, the ACCB algorithm calculates the reference charge Q in the next switching cycle. ref To improve transient response. Figure 3 As shown, when v out [k] is lower than v ref [k], Q ch [k+1]=Q ref [k] is used to adjust v out [k+2] to v ref [k]. Since the total charge flowing through the output capacitor is Q ch -Q dis , in the discrete time domain, gives v within a switching cycleout The changes are as follows:

[0046]

[0047] Where z is a basic unit in the Z transform.

[0048] The charge balancing controller corresponding to the ACCB algorithm is designed to convert v out Adjust to v ref , that is, v ref =v out z 2 To derive v out z 2 The value of , multiplying equation (1) by z+1 gives:

[0049]

[0050] In formula 2, Q dis With the load and output voltage changes, in one switching cycle is equal to v out T / R. Since R is unknown, Q dis To solve this problem, multiply equation (2) by 1-z -2 ,get:

[0051]

[0052] Due to the presence of output capacitance, the charge Q output to the load dis The change is small within a few switching cycles, Q dis (z+1-z -1 -z -2 )≈0 is valid. Therefore, equation (4) is derived:

[0053]

[0054] Due to the existence of the charge observer and the charge controller, Q ob =Q ch and Q ch =Q ref z -1 is valid. Therefore, substituting v ref =v out z 2 From formula (4), we get:

[0055] Q ref =Q ob z=Q ob (z -1 +z -2 -1)+C(v ref -2v out +vout z -2 ) (5)

[0056] Based on (5), the ACCB algorithm calculates the appropriate Q ref To improve transient response.

[0057] In formula (5), there is Z -2 , which means Q ref The calculation of Q has a lag of two switching cycles. Therefore, formula (5) means that although all the parameters in the formula are known, the correct Q ref It takes two switching cycles. If the circuit suddenly changes from a stable state to an unstable state, it also means that the circuit needs two cycles to react to the sudden change, and finally a total of four switching cycles are required to complete the charge balance.

[0058] ACCB algorithm is based on the assumption that Q dis (z+1-z -1 -z -2 )≈0, this approximate equation is used to eliminate Q in the equation dis , this is crucial because Q dis =v out There are unknowns in T / R. In addition, as shown in equation (5), the traditional ACCB algorithm calculates Q with a lag of two switching cycles. ref , obviously this hysteresis will degrade the transient response.

[0059] Based on the above analysis, this embodiment proposes a voltage extrapolation charge balance control strategy to eliminate response lag, such as Figure 4 The VECB algorithm module will detect V out Whether it deviates from V ref To control the operation of the charge controller. The VECB algorithm module calculates the reference charge Q by extrapolating the voltage ref , the extrapolated voltage is at the output charge Q ch = 0 condition from the current output voltage v out The theoretical voltage after two switching cycles. Using the extrapolated voltage, the voltage can be calculated without hysteresis and can be used to track the reference voltage v ref The reference charge is increased, thereby improving the transient response to circuit perturbations.

[0060] The extrapolated voltage above is given by Figure 3 The voltage extrapolator is calculated based on the output voltage v obtained by ADC sampling in the figure. out and Work. Figure 5As shown, for a Flyback converter operating in DCM mode, the output current is zero when the duty cycle is low within each switching period. Therefore, the output capacitor C discharges, and the output voltage decreases with a slope of dv out / dt, and there is

[0061] Assuming 2T << RC, which is valid in most application scenarios, the decrease in the output voltage is almost linear. Therefore, based on the measured v out and the extrapolated voltage v ext is given by:

[0062]

[0063] That is, if Q ch = 0, i.e., at zero output charge, the output voltage will drop to v ext within two switching periods. v ext Based on the current v out and dv out / / dt, it is continuously refreshed, and the value remains unchanged each time it is refreshed unless the circuit state changes. For the DCM state, when the switch is off, at this time Q ch = 0, and dv out / / dt can be obtained.

[0064] In addition, in order to adjust v out to v ref within two switching periods, the total output charge in the next two switching periods should be C(v ref - v ext ). Therefore, the discrete-time formula for the output charge should satisfy:

[0065] Q ch z + Q ch = C(v ref - v ext ) (7)

[0066] Assuming that Q ob = Q ch and Q ch = Q ref z -1 are guaranteed by the charge observer and the charge controller, the VECB algorithm is given by:

[0067] Q ref = C(v ref - v ext ) - Q ob (8)

[0068] Compared with Equation (5), the above algorithm is simpler, and calculating Q refThere is no lag in the process.

[0069] According to the above calculations, the closed-loop small signal models (SSM) of ACCB and VECB are as follows:

[0070]

[0071]

[0072] Φ r_VECB (z), Φ l_VECB (z) respectively represent the flyback converter under VECB control Relative to The transfer function and Relative to The transfer function of A small signal representing the output voltage, A small signal representing the reference voltage, represents the small signal of the load R; Φ r_ACCB (z) and Φ l_ACCB (z) represents the corresponding transfer function under ACCB control.

[0073] Comparing equations (9) and (10), we can see that {Φ r_VECB (z), Φ l_VECB (z)} relative to {Φ r_ACCB (z), Φ l_ACCB (z)}, is less affected by the coefficient a (a = T / RC). In addition, Φ l_VECB The molecular ratio Φ in (z) l_ACCB The numerator in (z) is delayed less, which indicates that the former has a faster transient response to circuit disturbances. Therefore, the theoretical analysis shows the advantages of VECB control over traditional ACCB control. That is, regardless of ACCB or VECB, the controller is designed to adjust v within two switching cycles. out to v ref , the difference is that Q ref In terms of calculation, the former lags behind by two cycles.

[0074] From the analysis of the above two algorithms, it can be seen that the output charge Q ch is calculated by the charge observer and regulated by the charge controller. The charge observer and charge controller ensure that Q ob =Q ch and Q ch =Q ref z -1 The traditional ACCB algorithm calculates Q with a lag of two switching cycles. ref, and then adjust the output voltage. This lag will reduce the transient response. The voltage extrapolator in the VECB algorithm is based on the sampled v out With DV out / dt, Q can be calculated without hysteresis ref , improving the transient response of the Flyback converter.

[0075] As the preferred solution, the above analysis is under ideal conditions, so Q ob =Q ch and Q ch =Q ref z -1 This premise is valid for both ACCB and VECB. This premise is ensured by the charge controller and charge observer. However, there is a damping effect in the actual output charge. For the actual Flyback circuit, such as Figure 6 As shown, L pt is the leakage inductance of the primary side, L st is the leakage inductance of the secondary side; R pt is the primary winding resistance, R st is the secondary winding resistance, R ds is the on-resistance of the switch tube, R F is the on-resistance of the diode, V F is the on-resistance of the diode; R s , C s , D s are the resistor, capacitor and diode of the RCD circuit, n:1 is the turns ratio, at this time Q ob =Q ch and Q ch =Q ref z -1 is no longer valid, the charge damping factor K damp Will affect the output voltage steady-state error. damp In the presence of , the control effect of the charge controller and the charge observer is expressed as:

[0076]

[0077] And because the discrete time model of the circuit in VECB control is as follows:

[0078]

[0079] The relative value of the steady-state error caused by the damping effect is derived from the above formula and formula (11):

[0080]

[0081] Because T / (RC)<0.01 and 0.8 <K damp<1 is valid in most application scenarios. At this time, the relative error is less than 0.5%. The relative error is of the same magnitude as the output voltage ripple value and can therefore be ignored.

[0082] Nevertheless, it is possible to use a constant compensation factor K C To minimize the damping effect. After considering the compensation factor, the actual effect of the charge observer and charge controller is as follows:

[0083]

[0084] like Figure 4 , Q ch Multiply by K c , Q ref Multiply by 1 / K c , the compensation factor acts on Q ch to ob The conversion of Q ref To Q ch in the conversion.

[0085] Therefore, the relative value of the steady-state error after considering the compensation factor is:

[0086]

[0087] In order to minimize the steady-state error, it is necessary to calculate the damping coefficient K according to the actual circuit under different steady-state conditions. damp ,like Figure 7 shown.

[0088] Preferably, the corresponding K is obtained according to formula (13) in this embodiment: C To eliminate the steady-state error caused by the damping effect, let K C =K damp , the theoretical relative steady-state error can be made equal to 0.

[0089] Therefore, due to the existence of parasitic effects, the actual output charge has a damping effect, and the Q ob =Q ch and Q ch =Q ref z -1 is no longer true, and a constant compensation factor K can be used C to minimize the damping effect.

[0090] The VECB control algorithm proposed in this embodiment eliminates the two-cycle lag in the charge balance calculation process of the traditional ACCB algorithm, greatly improving the linear regulation rate and load regulation rate of the Flyback converter used for DCM, as well as the transient response effect to the reference voltage jump. At the same time, a constant compensation factor K is used.C to minimize the damping effect.

[0091] An experimental circuit prototype was prepared and the VECB control proposed in this embodiment was compared with the traditional PI control and ACCB control. in =10V and v out =15V, experiments were carried out and three indicators were compared.

[0092] (I) Load Regulation

[0093] a. When the load resistance changes from 30Ω to 15Ω, the output voltage transient response is as follows Figure 8 As shown. Under PI control, the output voltage deviated by 210mV and stabilized again within 170us. Under ACCB control, the output voltage deviated by 270mV and stabilized again within 80us. Under VECB control, the output voltage deviated by 180mV and stabilized again within 40us. Compared with the ACCB controller, the VECB controller proposed in this embodiment reduces the transient response time and voltage deviation by 50% during load steps.

[0094] b. When the load resistance jumps from 150Ω to 15Ω, the transient response of the output voltage Fig. 9 As shown in the figure. Under the PI controller, the output voltage deviates by 370mV and stabilizes again within 240us. Under ACCB control, the output voltage deviates by 420mV and stabilizes again within 100us. Under VECB control, the output voltage deviates by 300mV and stabilizes again within 60us. For both ACCB and VECB controllers, the transient response is limited by charge saturation, where the duty cycle reaches its maximum value v out / (v in +v out ). Therefore, the output voltage transient ratio Figure 8 However, the transient response under VECB control is still much faster than that under PI and ACCB control.

[0095] It can be seen from the above that compared with the ACCB controller, the VECB controller reduces the transient response time and voltage deviation by 50% due to the elimination of the hysteresis of the charge balancing algorithm.

[0096] (II) Linear Regulation

[0097] According to the closed-loop SSM, under the control of ACCB and VECB, the output voltage is not affected by the input voltage disturbance. The experimental results are shown in Fig.10 shown.

[0098] When v inWhen jumping from 10V to 7.5V, the output voltage deviated by 210mV under PI control and stabilized again within 160us. Under ACCB and VECB control, the output voltage deviated by 130mV and stabilized again within 60us and 50us respectively. Both ACCB and VECB controllers showed great suppression of input voltage disturbances. VECB has a more obvious advantage.

[0099] (III) Reference voltage following

[0100] a.when v ref When the output voltage changes from 15V to 15.25V, the transient response is as follows: Fig.11 As shown in the figure, for the converter with PI controller, the output voltage is set to V within 130us. ref In addition, a 40mV overshoot of 16% of the jump voltage difference is caused. Under ACCB control, the output voltage tracks v within 80us. ref , and there is a 20mV overshoot. Under VECB control, there is no overshoot in the output voltage following process.

[0101] b. When v ref When the output voltage changes from 13V to 15V, the transient response is as follows: Fig.12 As shown. For the converter with PI controller, the output voltage is set to V within 190us. ref In addition, it causes a 1.1V overshoot of 55% of the jump voltage difference. The relative value of the overshoot is much higher than Fig.11 The value in (a) is due to duty cycle saturation and the circuit entering temporary CCM mode during transients. Under ACCB and VECB control, both output voltages rise linearly and track v within 130us. ref And there will be no overshoot. But the tracking time is longer than Fig.11 (b) and Fig.11 The one in (c) is much longer. This is because charge saturation occurs when the converter outputs its maximum voltage. Despite the charge saturation, the output voltage transients of ACCB and VECB are still relatively desirable.

[0102] From the above, it can be seen that the reference voltage following effect in VECB control is better than that in ACCB control.

[0103] Based on the comparison of the above three indicators, the experimental results show that the VECB controller proposed in this embodiment is stable in both small signal and large signal transients. In all measurement results, the output voltage shows good transient response and no obvious steady-state error. Compared with the ACCB controller, the VECB controller greatly improves the transient response to circuit disturbances.

[0104] Embodiment 2

[0105] A charge balancing controller for a DCM Flyback converter, such as Figure 4 As shown, it includes: a charge observer, a voltage extrapolator, a VECB algorithm module, and a charge controller; the charge observer, the voltage extrapolator and the VECB algorithm module are used to sample the input and output of the DCM Flyback converter in each switching cycle based on digital pulse width modulation, and when the charge amount reaches the charge balance control required, the following functions are performed in each switching cycle to complete the charge balance control within two switching cycles: the charge observer is used to calculate the output charge Q of the Flyback converter to the output capacitor in the current switching cycle based on the input and output of the DCM Flyback converter in the current switching cycle ch ; The voltage extrapolator is used to adjust the input and output of the DCM Flyback converter based on the current switching cycle. Estimate the output voltage v of the Flyback converter after two switching cycles ext , where v out and The current switching cycle is sampled at Q ch =0 when the output voltage and output voltage change, T is the duration of a single switching cycle; the VECB algorithm module is used to calculate the output charge Q ch , the output voltage v ext And the reference voltage v ref , according to Q ref =C(v ref -v ext )-Q ob The calculation method is as follows: ob =Q ch , Q ch =Q ref z -1 , z -1 is the unit delay factor in the Z transform, and the reference charge Q is calculated ref , the reference charge Q ref Used to calculate the duty cycle of the digital pulse width modulation signal to control the switching of the DCM Flyback converter in the next switching cycle.

[0106] Preferably, it also includes a correction unit for using a constant compensation factor K to reduce the damping effect. C , respectively correct the output charge Q ch and the reference charge Q ref , the correction method is as follows:

[0107]

[0108] In the formula, Kdamp Indicates the charge damping coefficient calculated and determined based on the current actual circuit.

[0109] Preferably, K C =K damp .

[0110] The relevant technical solution is the same as that in Embodiment 1 and will not be described in detail here.

[0111] Embodiment 3

[0112] A computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute a charge balancing control method for a DCM Flyback converter as described above.

[0113] The relevant technical solution is the same as that in Embodiment 1 and will not be described in detail here.

[0114] It will be easily understood by those skilled in the art that the above description is only a 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 scope of the present invention.

Claims

1. A charge balancing control method for a DCM Flyback converter, characterized in that: The charge balance control is completed within two switching cycles, where the following steps are performed in each switching cycle: Based on the input and output of the DCM Flyback converter in the current switching cycle obtained by sampling, the output charge Q of the Flyback converter to the output capacitor when the duty cycle of the current switching cycle is high is calculated. ch , and according to Estimate the output voltage v of the Flyback converter after two switching cycles ext , where v out and The current switching cycle is sampled at Q ch = The output voltage and output voltage change when 0, T is the duration of a single switching cycle; Based on the output charge Q ch , the output voltage v ext And the reference voltage v ref , according to Q ref =C(v ref -v ext )-Q ob The calculation method is as follows: ob =Q ch , Q ch =Q ref z -1 , z -1 is the unit delay factor in the Z transform, and the reference charge Q is calculated ref , the reference charge Q ref Used to calculate the duty cycle of the digital pulse width modulation signal to control the switching of the DCM Flyback converter in the next switching cycle; Among them, a constant compensation factor K is used to reduce the damping effect. C , respectively correct the output charge Q ch and the reference charge Q ref , the correction method is as follows: In the formula, K damp Indicates the charge damping coefficient calculated and determined based on the current actual circuit.

2. The charge balance control method according to claim 1, characterized in that: K C =K damp 。 3. A charge balancing controller for a DCM Flyback converter, characterized in that: include: Charge observer, voltage extrapolator, VECB algorithm module, and charge controller; The charge observer, the voltage extrapolator and the VECB algorithm module are used to sample the input and output of the DCM Flyback converter in each switching cycle based on digital pulse width modulation, and when the output charge amount requires charge balance control, perform the following functions in each switching cycle to complete the charge balance control within two switching cycles: The charge observer is used to calculate the output charge Q of the Flyback converter to the output capacitor in the current switching cycle based on the input and output of the DCM Flyback converter in the current switching cycle. ch ; The voltage extrapolator is used to adjust the input and output of the DCM Flyback converter based on the current switching cycle. Estimate the output voltage v of the Flyback converter after two switching cycles ext , where v out and The current switching cycle is sampled at Q ch = The output voltage and output voltage change when 0, T is the duration of a single switching cycle; The VECB algorithm module is used to output the charge Q ch , the output voltage v ext And the reference voltage v ref , according to Q ref =C(v ref -v ext )-Q ob The calculation method is as follows: ob =Q ch , Q ch =Q ref z -1 , z -1 is the unit delay factor in the Z transform, and the reference charge Q is calculated ref , the reference charge Q ref Used for calculating the duty cycle of the digital pulse width modulation signal to control the switching of the DCM Flyback converter in the next switching cycle; Among them, the compensation factor K used to reduce the damping effect is constant. C , respectively correct the output charge Q ch and the reference charge Q ref , the correction method is as follows: In the formula, K damp Indicates the charge damping coefficient calculated and determined based on the current actual circuit.

4. The charge balancing controller according to claim 3, characterized in that: K C =K damp 。 5. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute a charge balancing control method for a DCM Flyback converter according to claim 1 or 2.

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