Dynamic control optimization system and method for primary feedback controlled switching converter

Abstract

This invention discloses a dynamic control optimization system and method for a primary-side feedback control switching converter, including a main topology circuit and a control circuit. The main topology primarily adopts a primary-side feedback switching converter structure, sampling the voltage V of the primary winding of the switching converter. sense Main winding current information I p The signal is transmitted to the control circuit to control the output current of the switching converter. The control circuit includes an output current prediction module, an output voltage sampling module, a dynamic optimization control module, a PID compensation control module, and a PWM drive module. The PWM drive module outputs a switching signal to control the on / off state of the switching transistors in the main topology circuit, forming a closed loop. This invention reduces the dynamic response time and improves the dynamic response speed, making it suitable for various types of switching power supplies.

Description

Technical Field

[0001] This invention relates to dynamic control of control switching converters, and more specifically to a dynamic control optimization system and method for primary-side feedback control switching converters. Background Technology

[0002] In recent years, with the development of low-power electronic devices, chargers and adapters based on offline power supplies have been widely used, and designing low-cost, low-power switching power supplies has gradually become a research hotspot. Commonly used offline switching power supplies mainly include flyback converters, forward converters, half-bridge converters, and full-bridge converters. Among them, flyback converters are widely used in low-power electronic devices due to their advantages such as simple circuit structure, low cost, and good isolation.

[0003] Depending on the control method, flyback converters can be controlled using either primary-side feedback or secondary-side feedback. Secondary-side feedback primarily uses optocouplers between the transformer input and output load to convert the output electrical signal into an optical signal for transmission, which is then converted back into an electrical signal for input to the control module. This control method offers good real-time performance, but the addition of optocouplers and other components increases circuit complexity. Furthermore, optocouplers are prone to aging and are susceptible to temperature variations, reducing the reliability and lifespan of the power supply. Primary-side feedback typically introduces an auxiliary winding, indirectly controlling the output voltage or current based on the voltage information from this auxiliary winding. The primary-side feedback circuit does not use optocouplers, thus improving circuit integration.

[0004] Since the output current cannot be directly sampled, the constant current control of the output of a traditional primary-side feedback flyback converter mainly relies on maintaining the average current I of the output diode. dREF To achieve a constant current, the output winding and output diode are equivalent to a current I. dREF The constant current source supplies power to the output load and output capacitor. During the dynamic process, through analysis of the output equivalent circuit, the output voltage satisfies:

[0005]

[0006] The output current satisfies:

[0007]

[0008] Where R1 represents the load resistance before switching, R2 represents the load resistance after switching, and C represents the output capacitor. The output current and output voltage recover to their stable values ​​exponentially, and the dynamic response time depends only on the time constant τ, which is the product of the output capacitor C and the load resistance R2 after switching.

[0009] Compared with the secondary-side feedback method, the primary-side feedback method has a longer response time in the dynamic process because it cannot directly sample the output current information. Therefore, it is necessary to study the dynamic optimization control strategy of the primary-side feedback constant current control switching power supply.

[0010] Existing methods for improving the dynamic response of primary-side feedback are mainly aimed at systems with constant output voltage. They involve changing the input power to make the output voltage stabilize quickly and determining the operating mode based on the slope of the output voltage change to eliminate voltage overshoot. However, this method is not suitable for constant current converters with varying output voltage. Summary of the Invention

[0011] Based on the above analysis, this invention proposes a dynamic control optimization system and method for primary-side feedback control switching converters, which is applicable to various types of switching converters, reduces dynamic response time, and improves dynamic response speed.

[0012] The technical solution to achieve the purpose of this invention is as follows:

[0013] A dynamic control optimization system for a primary-side feedback control switching converter includes a main topology circuit and a control circuit. The main topology primarily adopts a primary-side feedback switching converter structure and samples the voltage V of the primary winding of the switching converter. sense Main winding current information I p The signal is transmitted to the control circuit to control the output current of the switching converter. The control circuit includes an output current prediction module, an output voltage sampling module, a dynamic optimization control module, a PID compensation control module, and a PWM drive module. The PWM drive module outputs a switching signal to control the switching transistors in the main topology circuit to turn on and off, forming a closed loop.

[0014] Furthermore, the proposed output current prediction module takes as input the voltage V of the primary winding of the converter. sense Primary winding current I p and switching period T s Based on the above signals, the average current I of the output diode is calculated. d This information is then transmitted to the PID compensation control module. When the switching converter reaches a stable state, the current in the output load is equal to the average current I of the output diodes. d At this time, the output current can be obtained through I d express.

[0015] Furthermore, the proposed output voltage sampling module receives the primary winding voltage V as its input signal. sense The output signal is the output voltage V. o It is then passed to the dynamic optimization control module.

[0016] Furthermore, the proposed dynamic optimization control module includes a dynamic detection module, a parameter calculation module, and an optimization control module. Its input signal is the output voltage V. o The output signal is the average current reference value I of the output diode. dREF PID initial control parameters V after load switching pi0 The dynamic mode variable mode_D, and the output signal are transmitted to the PID compensation control module, specifically including:

[0017] (1) The input to the dynamic detection module is the output voltage V. o Estimated steady-state output voltage V after load switching o_stable2 The output is the dynamic mode variable mode_D. The dynamic detection module first bases its detection on the output voltage V. o The upper limit of steady-state output voltage V is calculated. omax and lower limit V omin Secondly, based on the output voltage V o Estimated steady-state output voltage V after load switching o_stable2 Upper limit of steady-state output voltage V omax and lower limit V omin The relationship enables switching between normal and dynamic modes, and determines the load changes under dynamic conditions.

[0018] Upper limit of steady-state output voltage V omax and lower limit V omin The calculation method is as follows:

[0019] The output voltage V is calculated once every N cycles. o average value V o_avg When V o_avg When the fluctuation is small enough, the output voltage stabilizes. At this point, the average value of the output voltage is recorded as the current steady-state load voltage V. o_stable1 Based on the current load steady-state voltage V o_stable1 Calculate the upper limit of steady-state output voltage V omax and lower limit V omin .

[0020] V omax satisfy

[0021] V omax =V o_stable1 +ΔV1,

[0022] V omin satisfy

[0023] V omin =V o_stable1 -ΔV2,

[0024] Here, ΔV1 and ΔV2 are small voltages related to the system parameters.

[0025] The method for switching between normal mode and dynamic mode is as follows:

[0026] When the converter is in normal operating mode, the dynamic mode variable mode_D is set to "0". If the output voltage is higher than V... omin And below V omax When the load does not change significantly, the converter remains in normal operating mode, and mode_D remains "0"; if the output voltage is greater than or equal to V omax At that time, the output voltage V o When the load impedance increases, the converter enters dynamic mode, indicating an increase in load impedance. At this point, mode_D is set to "1". If the output voltage is less than or equal to V... omin At that time, the output voltage V o When the load impedance decreases, the converter enters dynamic mode, indicating a reduction in load impedance. At this point, mode_D is set to "2".

[0027] When the converter is in dynamic operating mode, mode_D is either "1" or "2". When mode_D is "1", that is, the output voltage V... o Greater than or equal to V omax Then, once the output voltage is detected to be greater than or equal to the estimated steady-state output voltage V after load switching, o_stable2 When the dynamic working mode is exited and the normal working mode is returned, mode_D is set to "0"; when mode_D is "2", that is, the output voltage V o Less than or equal to V omin Then, once the output voltage is detected to be less than or equal to the estimated steady-state output voltage V after load switching, o_stable2 When exiting dynamic working mode, return to normal working mode, and set mode_D to "0".

[0028] (2) The input to the parameter calculation module is the output voltage V. o The dynamic mode variable mode_D outputs the initial PID control parameters V after load switching. pi0 Estimated steady-state output voltage V after load switching o_stable2 This data is then transmitted to the PID compensation control module and the dynamic detection module. First, this module determines the output voltage V... o Calculate the load impedance R2 after switching, considering the changes during the dynamic process; then, based on the load impedance R2 after switching, calculate the estimated steady-state output voltage V after load switching. o_stable2 Initial PID control parameters V after load switching pi0 .

[0029] The main calculation method for the load impedance R2 after switching is as follows:

[0030] When mode_D switches from "0" to "1" or "2", it indicates a switch from normal mode to dynamic mode. Let the current time be t1, and let the output voltage V be recorded at this time. o For V o (t1); Starting from time t1, after a known time interval Δt1, i.e. at time t2 = t1 + Δt1, let the output voltage V at this time be denoted as V. o For V o (t2); Starting from time t2, after a known time interval Δt2, i.e. at time t3 = t2 + Δt2, let the output voltage V at this time be recorded. o For V o (t3); Based on V o (t1), V o (t2), V o The output load impedance is calculated from (t3), Δt1, and Δt2 as follows:

[0031]

[0032] Where R2 represents the load impedance after switching, and C represents the output capacitor.

[0033] Estimated steady-state output voltage V after load switching o_stable2 Initial PID control parameters V after load switching pi0 The main calculation method is as follows:

[0034] Estimated steady-state output voltage V after load switching o_stable2 Initial PID control parameters V after load switching pi0 This represents the situation after load switching, where the output current equals the target reference current I. REF Output voltage and PID control parameters V pi V o_stable2 That is, at this time, the load impedance R2 and the target reference current I REF The product of is expressed as

[0035]

[0036] When the load impedance R2 and the input voltage V in Given that the PID control parameters V of the steady-time converter can be derived based on existing control methods, then... pi , remember this V pi The value is the initial PID control parameter V after load switching. pi0 (3) The input signal of the optimized control module is the dynamic mode variable mode_D, and the output signal is the average current reference value I of the output diode. dREF This information is then transmitted to the PID compensation control module. When mode_D is "0", the average current reference value I of the output diode is... dREFThat is, the target reference current I REF When stable, the output current will stabilize at the target reference current I. REF When mode_D is "1", the average current reference value I of the output diode is... dREF Set as a large current I d_high , among which, I d_high =I REF +ΔI1, based on the system parameter ΔI1, should be as large as possible to allow more primary-side power to be transferred to the secondary side, resulting in a faster increase in output voltage; when mode_D is "2", the average current reference value of the output diode is I. dREF Set as a small current I d_low , among which, I d_low =I REF -ΔI2, based on the system parameter ΔI2, is taken to be as small as possible so that less primary-side power is transferred to the secondary side, the output capacitor discharges through the output load, and the output voltage decreases faster.

[0037] Furthermore, the proposed PID compensation control module takes the average current I of the output diode as its input signal. d Average current reference value I of output diode dREF PID initial control parameters V after load switching pi0 The dynamic mode variable mode_D outputs a control parameter V. pi This information is then transmitted to the PWM driver module.

[0038] Let mode_D be the mode variable of the previous switching cycle. If mode_D_pre is "1" or "2" and mode_D is "0", then the control parameter V... pi Equal to the initial PID control parameter V after load switching pi0 Otherwise, the average current reference value I of the output diode will be used. dREF With the average current I of the output diode d The difference yields the error e(n), and based on the value of e(n), the control parameter V for the next cycle is calculated using PID compensation control. pi .

[0039] Furthermore, the proposed PWM drive module's input signal is the primary winding current I. p The control parameters V generated by the PID compensation control module pi The output signal is the switching period T. s and the duty signal of the switching transistor;

[0040] According to the control parameter V pi Calculate the switching period T s and current control value I p_ctrlBased on the primary winding current I p Switching period T s and current control value I p_ctrl It can generate the duty signal for the switching transistor. Taking the peak current control method as an example, based on the control parameter V... pi The switching period T can be calculated. s and peak current control value I p_ctrl Each switching cycle T s When duty is set to "1", the switching transistor is turned on; through peak current control, when the primary winding current I... p When the peak value is reached, duty is set to "0", the switching transistor is turned off, and this generates the control signal duty for the switching transistor. s The signal is transmitted to the output current prediction module, and the duty controls the switching transistors in the main topology circuit to form a closed loop.

[0041] A method for a dynamic control optimization system based on the aforementioned primary-side feedback control switching converter includes the following steps:

[0042] The output current prediction module is based on the auxiliary winding voltage V of the main topology circuit. sense Primary sampling voltage V p and the switching period T output by the PWM drive module s Predict the average current I of the output diode d And transmit it to the PID compensation control module;

[0043] The output voltage sampling module is based on the auxiliary winding voltage V sense Sampling output voltage V o And transmit it to the dynamic optimization control module;

[0044] The dynamic optimization control module adjusts the output voltage V based on the output voltage V. o This generates the average current reference value I of the output diode. dREF PID initial control parameters V after load switching pi0 And the dynamic mode variable mode_D, and pass it to the PID compensation control module;

[0045] The PID compensation control module uses the dynamic mode variable mode_D and the average current reference value I of the output diode. dREF Average current I of output diode d Initial PID control parameters V after load switching pi0 This generates the control parameter V for the next cycle. pi And pass it to the PWM driver module;

[0046] The PWM drive module determines the control parameter V based on the control parameter V. piThe switching period T of the next output cycle is determined by sampling the primary side information of the circuit topology. s The control signal duty of the switching transistor in the main topology circuit forms a closed loop with the main topology circuit, and the switching period T is... s Input to output current prediction module;

[0047] Repeat the above steps to control the switching converter in the main topology circuit.

[0048] Compared with existing technologies, the significant advantages of this invention are:

[0049] (1) The dynamic detection module proposed in this invention first calculates the upper and lower limits of the steady-state voltage, and then switches between normal mode and steady-state mode according to the relationship between the output voltage and the upper and lower limits of the steady-state voltage.

[0050] (2) The parameter calculation module proposed in this invention calculates the load impedance after switching based on the change characteristics of the output voltage in the dynamic process, calculates the estimated steady-state output voltage and PID initial control parameters after load switching based on the load impedance, switches between steady-state mode and normal mode based on the steady-state output voltage after load switching, and sets the initial working state of the PID control method based on the PID initial control parameters after load switching after exiting the dynamic mode.

[0051] (3) The optimized control module proposed in this invention inputs small energy in the mode of switching from heavy load impedance to light load impedance, or inputs large energy in the mode of switching from light load impedance to heavy load impedance, according to the change of load impedance, so that the output is fast and stable and the dynamic recovery time is greatly reduced.

[0052] (4) The control method proposed in this invention is applicable to all types of switching power supplies. Attached Figure Description

[0053] Figure 1 This is a block diagram of the control circuit in this invention.

[0054] Figure 2 This is a typical circuit topology diagram of a primary-side feedback flyback converter.

[0055] Figure 3 The waveform diagram is shown when the current is discontinuous.

[0056] Figure 4(a) shows the circuit topology of the output voltage sampling module.

[0057] Figure 4(b) shows the waveform of the output voltage sampling module (Δt = Δt). ref )picture.

[0058] Figure 4(c) shows the waveform of the output voltage sampling module (Δt>Δt). ref )picture.

[0059] Figure 4(d) shows the waveform of the output voltage sampling module (Δt < Δt). ref )picture.

[0060] Figure 5(a) shows the waveform of the dynamic optimization control strategy under light load to heavy load.

[0061] Figure 5(b) shows the waveform of the dynamic optimization control strategy under heavy load switching to light load.

[0062] Figure 6 This is a waveform diagram for peak current control.

[0063] Figure 7 This is the execution logic diagram of the present invention.

[0064] Figure 8(a) shows a comparison of the dynamic response time of the traditional control method and the control method proposed in this invention when the load impedance increases.

[0065] Figure 8(b) shows a comparison of the dynamic response time of the traditional control method and the control method proposed in this invention when the load impedance decreases. Detailed Implementation

[0066] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] See Figure 1 The dynamic control optimization system for a primary-side feedback control switching converter proposed in this invention includes an output current prediction module, an output voltage sampling module, a dynamic optimization control module, a PID compensation control module, and a PWM drive module; the auxiliary winding voltage V sense The input is fed into the output current prediction module, which will predict the average current I of the output diode. d And transmit it to the PID compensation control module; the output voltage sampling module based on the auxiliary winding voltage V sense Sampling output voltage V o And transmit it to the dynamic optimization control module; the dynamic optimization control module, based on the output voltage V o This generates the average current reference value I of the output diode. dREF PID initial control parameters V after load switching pi0 The dynamic mode variable mode_D is input and passed to the PID compensation control module; the PID compensation control module inputs the dynamic mode variable mode_D and the average current reference value I of the output diode. dREF Average current I of output diode dInitial PID control parameters V after load switching pi0 This generates the control parameter V for the next cycle. pi The data is then transmitted to the PWM driver module; the PWM driver module then adjusts the control parameters V according to the given parameters. pi Switching control is performed using primary-side information sampled from the circuit topology.

[0068] Figure 2 This is a typical circuit in the main structure of a switching power supply, employing a primary-side feedback flyback converter structure. The transformer has three windings, with the auxiliary winding sampling the primary-side information and the auxiliary winding providing voltage division V. sense Input to the control circuit; a small current sampling resistor is connected in series between the source terminal of the switching transistor and the ground terminal to sample the primary winding current I. p and its voltage V p Input to the control circuit. The control circuit is based on V. sense V p The loop control generates the duty signal for the switching transistor.

[0069] Figure 3 In discontinuous current mode, the switching signal duty and the primary current I are represented. p Secondary current I s and auxiliary winding component voltage V sense The operating waveform. When the switching transistor is turned on, the primary current I... p The current increases linearly; at the instant the switch is turned off, the energy from the primary side is coupled to the secondary side, and the secondary side current I... s V reaches its peak and then begins to decrease linearly. sense The time during which the magnetization gradually decreases is called the demagnetization time T. r ; when I s After being reduced to 0, due to the resonance caused by the magnetizing inductance and the parasitic capacitance of the switching transistor, V sense The oscillation continues until the start of the next cycle; this period is called the dead time T. d .

[0070] The proposed output current prediction module takes as input the voltage V of the primary winding of the converter. sense Primary side sampling voltage V p and switching period T s Based on the above signals, the average current I of the output diode is calculated. d Once a steady state is reached, the current flowing through the output load is equal to the output diode current. Therefore, the output current can be obtained by calculating the average current of the output diode. The average current of the output diode over one cycle can be expressed as:

[0071]

[0072] Among them, R p N represents the primary-side sampling resistor.p and N s The number of turns in the primary and secondary windings of a transformer depends on the system parameters; V p_peak T represents the primary peak voltage. s Indicates the switching period, which is the input value for the output current prediction module; T r Indicates demagnetization time, via V sense The result is calculated by comparing it with the 0 voltage.

[0073] The proposed output voltage sampling module takes as input the primary winding voltage V as input. sense The output signal is the output voltage V. o When the primary current I s When the voltage drops to 0, the auxiliary winding component voltage V sense_sampling The relationship between the output voltage Vo and the voltage is:

[0074]

[0075] Where R1 and R2 represent the voltage divider resistor values ​​across the auxiliary winding, N a and N s The number of turns in the transformer's auxiliary and secondary windings depends on the system parameters. (Using I...) s The moment when the voltage drops to 0 is taken as the "sampling point," and the auxiliary winding voltage V is sampled at that moment. sense_sampling This can represent the output voltage V. o The specific sampling module circuit topology is shown in Figure 4(a), which is a conventional topology and will not be described in detail here.

[0076] The digital control module outputs two digital quantities V with a fixed difference ΔV. ref_dig and V knee_dig ΔV depends on the system parameters and generates two analog quantities V after passing through the DAC. ref_ana and V knee_ana and the input signal V sense The comparison results, Scomp_ref and Scomp_knee, represent the sampled voltage V. sense respectively with V ref and V knee The distance between them is input into the digital control module for analysis; the digital control module analyzes the distance based on the current cycle V. sense With V ref and V knee The difference between them determines the magnitude of the digital output voltage in the next cycle, until V... knee The sampling point was traced.

[0077] Figures 4(b), (c), and (d) show the operating waveforms of the output voltage sampling module. Referring to Figure 4(b), when Vknee When a sampling point is traced, the time interval Δt at that moment is set as the reference value Δt. ref That is, when Δt = Δt ref At that time, V knee If the voltage at the sampling point is V, then the digital voltage output in the next cycle is equal to the digital voltage output in the current cycle; referring to Figure 4(c), when V knee When the value is higher than the sampling point, then Δt > Δt ref If the output digital voltage in the next cycle is smaller than the output digital voltage in the current cycle, then, referring to Figure 4(d), when V knee When the value is below the sampling point, Δt < Δt ref If the output digital voltage in the next cycle is greater than the output digital voltage in the current cycle, then the output digital voltage value V is continuously adjusted in the digital control module. ref_dig and V knee_dig This allows it to continuously approach the voltage at the sampling point until the voltage at the sampling point is accurately sampled.

[0078] The proposed dynamic optimization control module includes a dynamic detection module, a parameter calculation module, and an optimization control module. Its input signal is the output voltage V. o The output signal is the average current reference value I of the output diode. dREF PID initial control parameters V after load switching pi0 The dynamic mode variable mode_D is output as a signal to the PID compensation control module. For specific waveform diagrams, please refer to Figure 5(a) and Figure 5(b).

[0079] Referring to Figures 5(a) and 5(b) during the t0-t1 stage, the dynamic detection module's input is the output voltage V. o Estimated steady-state output voltage V after load switching o_stable2 The output is the dynamic mode variable mode_D.

[0080] The output voltage V is calculated once every N cycles. o average value V o_avg When V o_avg When the fluctuation is small enough, the output voltage stabilizes. At this point, the average value of the output voltage is recorded as the current steady-state load voltage V. o_stable1 Based on the current load steady-state voltage V o_stable1 Calculate the upper limit of steady-state output voltage V omax and lower limit V omin .

[0081] V omax satisfy

[0082] V omax =V o_stable1 +ΔV1,

[0083] Vomin satisfy

[0084] V omin =V o_stable1 -ΔV2,

[0085] Here, ΔV1 and ΔV2 are small voltages related to the system parameters.

[0086] When the converter is in normal operating mode, the dynamic mode variable mode_D is set to "0". If the output voltage is higher than V... omin And below V omax When the load does not change significantly, the converter remains in normal operating mode, and mode_D remains "0"; if the output voltage is greater than or equal to V omax At that time, the output voltage V o When the load impedance increases, the converter enters dynamic mode, indicating an increase in load impedance. At this point, mode_D is set to "1". If the output voltage is less than or equal to V... omin At that time, the output voltage V o When the load impedance decreases, the converter enters dynamic mode, indicating a reduction in load impedance. At this point, mode_D is set to "2".

[0087] Once the dynamic mode is detected, the parameter calculation module begins to work. Referring to the t1-t3 stage in Figures 5(a) and 5(b), its input is the output voltage V. o The dynamic mode variable mode_D outputs the initial PID control parameters V after load switching. pi0 Estimated steady-state output voltage V after load switching o_stable2 .

[0088] When mode_D switches from "0" to "1" or "2", let the current time be t1, and let the output voltage V be recorded at this time. o For v o (t1); Starting from time t1, after a known time interval Δt1, i.e. at time t2 = t1 + Δt1, let the output voltage V at this time be denoted as V. o For v o (t2); Starting from time t2, after a known time interval Δt2, i.e. at time t3 = t2 + Δt2, let the output voltage V at this time be recorded. o For v o (t3). In a flyback converter constant current system, v o (t1), v o (t2), v o (t3) can be represented as:

[0089]

[0090] When Δt1 = Δt2, v o(t1), v o (t2) and v o (t3) satisfies:

[0091]

[0092] Therefore, the load impedance R2 after switching can be expressed as:

[0093]

[0094] Where R2 represents the load impedance after switching, and C represents the output capacitor.

[0095] Estimated steady-state output voltage V after load switching o_stable2 That is, the output current is equal to the target reference current I. REF The output voltage at this time can be expressed as the output current I at this time. REF The product of this and the load impedance R2 is expressed as:

[0096]

[0097] Calculated steady-state output voltage V after load switching o_stable2 The signal is transmitted to the dynamic detection module. When the converter is in dynamic operating mode, mode_D is either "1" or "2". If mode_D is "1", that is, the output voltage V... o Greater than or equal to V omax Then, when the output voltage is detected to be greater than or equal to the estimated steady-state output voltage V after load switching, o_stable2 When the dynamic working mode is exited and the normal working mode is returned, mode_D is set to "0"; if mode_D is "2", that is, the output voltage V o Less than or equal to V omin Then, when the output voltage is detected to be less than or equal to the estimated steady-state output voltage V after load switching, o_stable2 When exiting dynamic working mode, return to normal working mode, and set mode_D to "0".

[0098] Maintain T during dynamic process s Unchanged, i.e., T s =T s0 According to the principle of energy conservation, the primary peak voltage V after load switching peak0 It can be expressed by the following formula:

[0099]

[0100] That is, V after load switching peak0 It can be represented as:

[0101]

[0102] Among them, L p The primary magnetizing inductance is represented by η, and the transmission efficiency is represented by η. The initial PID control parameters V are set after load switching. pi0 =V peak0 The result is then transmitted to the PID compensation control module.

[0103] After the parameter calculation module calculates the steady-state operating parameters, the optimization control module starts working. Referring to the t3-t4 stage in Figures 5(a) and 5(b), its input signal is the dynamic mode variable mode_D, and its output signal is the average current reference value I of the output diode. dREF This information is then transmitted to the PID compensation control module. When mode_D is "0", the average current reference value I of the output diode is... dREF That is, the target reference current I REF When mode_D is "1", the average current reference value I of the output diode is... dREF Set as a large current I d_high , among which, I d_high =I REF +ΔI1, based on the system parameter ΔI1, should be as large as possible to allow more primary-side power to be transferred to the secondary side, resulting in a faster increase in output voltage; when mode_D is "2", the average current reference value of the output diode is I. dREF Set as a small current I d_low Among them, I d_low =I REF -ΔI2, based on the system parameter ΔI2, is taken to be as large as possible so that less primary-side power is transferred to the secondary side, the output capacitor discharges through the output load, and the output voltage decreases faster.

[0104] The proposed PID compensation control module takes the average current I of the output diode as its input signal. d Average current reference value I of output diode dREF PID initial control parameters V after load switching pi0 And the dynamic mode variable mode_D, the output signal is the compensation value V pi This information is then transmitted to the PWM driver module.

[0105] Let mode_D be the mode variable of the previous switching cycle. If mode_D_pre is "1" or "2" and mode_D is "0", the compensation value V is... pi Equal to the initial PID control parameter V after load switching pi0 Otherwise, the average current reference value I of the output diode will be used. dREF With the average current I of the output diode dThe difference yields the error e(n), and based on the value of e(n), a new compensation value V is calculated using PID compensation control. pi The PID compensation control calculation method is a commonly used method in this field, and will not be elaborated here.

[0106] The proposed PWM drive module uses the peak current control principle, and its input signal is the primary side sampling voltage V. p V generated by the PID compensation control module pi The output signal is the switching period T. s The duty signal for the switching transistor.

[0107] Based on the compensation value V pi Calculate the switching period T s and primary peak voltage V peak Based on the primary side sampling voltage V p Switching period T s and primary peak voltage V peak It can generate the duty signal, which controls the switching transistor. (See reference) Figure 6 Each switching cycle T s When duty is set to "1", the switching transistor is turned on; through peak current control, when the primary side sampling voltage V p Reaching peak V peak When duty is set to "0", the switching transistor is turned off, thus generating the control signal duty for the switching transistor. s The signal is transmitted to the output current prediction module, and the duty controls the switching transistors in the main topology circuit to form a closed loop.

[0108] Execution logic reference of the present invention Figure 7 First, the operating mode is determined based on the dynamic mode variable mode_D. If mode_D is "0", it indicates that the normal operating mode is in progress. If mode_D is "1" or "2", it indicates that the dynamic operating mode is in progress.

[0109] If operating in normal mode, first calculate the average value V of the output voltage over N cycles. o_avg Determine if the output voltage has reached a stable state. If it has, determine the steady-state output voltage V at that point. o_stable1 And calculate the upper limit of steady-state output voltage V. omax and lower limit V omin If stability is not achieved, adjust the output voltage using PID compensation control to stabilize it. Next, determine the output voltage V. o With steady-state output voltage upper limit V omax and lower limit V omin The relationship, if V o Greater than or equal to V omaxThis indicates an increase in load impedance, entering dynamic mode, and mode_D is set to "1"; if V o Less than or equal to V omin This indicates that the load impedance has decreased and the system has entered dynamic mode; mode_D is set to "2".

[0110] If operating in dynamic mode, i.e., mode_D is "1" or "2", first calculate the steady-state operating parameters, i.e., the estimated steady-state output voltage V after load switching. o_stable2 Initial PID control parameters V after load switching pi0 Secondly, determine whether the output voltage has reached the estimated steady-state output voltage V after load switching. o_stable2 If the output voltage does not reach the estimated steady-state output voltage V after load switching. o_stable2 If mode_D is "1", then a larger output diode current reference value I will be output. d_high If mode_D is "2", then a small output diode current reference value I will be output. d_low This allows the output voltage to quickly reach a stable state; if the output voltage reaches the estimated steady-state output voltage V after load switching... o_stable2 Exit dynamic mode, set mode_D to "0", and output the initial PID control parameters V after load switching. pi0 And start working with these parameters.

[0111] This invention can also be used in other types of primary-side feedback switching power supply circuit structures; here, we will only take the primary-side feedback flyback circuit as an example.

[0112] The flyback converter has an input voltage of 90–265V, an output constant current of 1A, and an output voltage of 1–5V. The turns ratio of the transformer's primary, secondary, and auxiliary windings is 160:10:14. The primary inductance is 1.6mH. The switching frequency is set to 50–70kHz. ΔV1 is 0.1V, ΔV2 is 0.1V, Δt1 is 80μs, Δt2 is 80μs, ΔI1 is 0.7A, and ΔI2 is 0.7A.

[0113] Referring to Figures 8(a) and 8(b), the dynamic response time of the conventional control scheme and the dynamic response time of the control method proposed in this invention are shown. Compared with the conventional control method, the dynamic control method proposed in this invention significantly reduces the dynamic response time.

[0114] This invention firstly, based on the exponential change characteristic of the output current in the current primary-side feedback constant current control, obtains the load resistance value after switching by sampling, judging and calculating the output voltage; secondly, by controlling the switching transistor to turn on and off, the power transferred from the primary side to the secondary side is changed, thereby rapidly increasing or decreasing the output voltage and reducing the recovery time of the dynamic process.

[0115] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the invention is limited to these descriptions. Many variations of the invention described herein are possible, and such variations should not deviate intentionally from the spirit and scope of the invention. Therefore, all modifications that are obvious to those skilled in the art are included within the scope of the claims.

Claims

1. A dynamic control optimization system for a primary-side feedback control switching converter, comprising a main topology circuit employing a primary-side feedback switching converter structure, characterized in that, It also includes a control circuit, which comprises an output current prediction module, an output voltage sampling module, a dynamic optimization control module, a PID compensation control module, and a PWM drive module; wherein: The input to the output current prediction module is the auxiliary winding voltage V of the main topology circuit. sense Primary sampling voltage V p and the switching period T output by the PWM drive module s Predict the average current I of the output diode d And transmit it to the PID compensation control module; The output voltage sampling module is based on the auxiliary winding voltage V sense Sampling output voltage V o And transmit it to the dynamic optimization control module; The dynamic optimization control module is based on the output voltage V o This generates the average current reference value I of the output diode. dREF PID initial control parameters V after load switching pi0 And the dynamic mode variable mode_D, and pass it to the PID compensation control module; The PID compensation control module is based on the dynamic mode variable mode_D and the average current reference value I of the output diode. dREF Average current I of output diode d Initial PID control parameters V after load switching pi0 This generates the control parameter V for the next cycle. pi And pass it to the PWM driver module; The PWM drive module determines the control parameter V. pi The switching period T of the next output cycle is determined by sampling the primary side information of the circuit topology. s The control signal duty of the switching transistor in the main topology circuit forms a closed loop with the main topology circuit, and the switching period T is... s Input to the output current prediction module.

2. The dynamic control optimization system for a primary-side feedback control switching converter according to claim 1, characterized in that, The average diode current I output by the output current prediction module d for: Among them, R p N represents the primary-side sampling resistor. p and N s Indicates the number of turns in the primary and secondary windings of the transformer; V p_peak T represents the primary peak voltage. s Indicates the switching period; T r The demagnetization time is indicated by the auxiliary winding voltage V. sense Determined by comparing with 0 voltage.

3. The dynamic control optimization system for a primary-side feedback control switching converter according to claim 1, characterized in that, The output voltage V o With auxiliary winding voltage V sense The relationship is: Where R1 and R2 represent the voltage divider resistor values ​​across the auxiliary winding, N a and N s Indicates the number of turns in the transformer's auxiliary winding and secondary winding, expressed in I. s V is taken as the sampling point when it drops to 0. sense_sampling The auxiliary winding is divided into voltage components at the sampling moment.

4. The dynamic control optimization system for a primary-side feedback control switching converter according to claim 1, characterized in that, The dynamic optimization control module includes a dynamic detection module, a parameter calculation module, and an optimization control module; the input of the dynamic detection module is the output voltage V. o Estimated steady-state output voltage V after load switching o_stable2 This module is used to determine the dynamic mode variable mode_D; the parameter calculation module takes the output voltage V as its input. o And the dynamic mode variable mode_D, this module is used to determine the initial PID control parameters V after load switching. pi0 Estimated steady-state output voltage V after load switching o_stable2 The optimization control module takes a dynamic mode variable, mode_D, as its input. This module is used to determine the diode average current reference value I. dREF .

5. A dynamic control optimization system for a primary-side feedback control switching converter according to claim 4, characterized in that, The dynamic detection module determines the dynamic mode variable mode_D by: Determine the upper limit of steady-state output voltage V omax and lower limit V omin ; V omax =V o_stable1 +ΔV1 V omin =V o_stable1 -ΔV2 Where ΔV1 and ΔV2 are voltages related to system parameters, V o_stable1 This is the average value of the output voltage over N cycles; When the converter is in normal operating mode, the dynamic mode variable mode_D is set to 0. If the output voltage is higher than V... omin And below V omax At this time, the converter is still in normal operating mode, and mode_D remains 0; if the output voltage V o Greater than or equal to V omax At that time, the output voltage V o When the output voltage V increases, mode_D is set to 1; if the output voltage V... o Less than or equal to V omin At that time, the output voltage V o The value decreases, at which point mode_D is set to 2; When the converter is in dynamic operating mode, if mode_D is 1, the estimated steady-state output voltage V is predicted after load switching when the detected output voltage is greater than or equal to the output voltage. o_stable2 When the dynamic working mode is exited and the normal working mode is returned, mode_D is set to 0; if mode_D is 2, when the output voltage is detected to be less than or equal to the estimated steady-state output voltage V after load switching, the dynamic working mode is exited and the normal working mode is returned, and mode_D is set to 0; if mode_D is 2, when the output voltage is detected to be less than or equal to the estimated steady-state output voltage V after load switching, the dynamic working mode is exited and the normal working o_stable2 When exiting dynamic working mode, return to normal working mode, and set mode_D to 0.

6. The dynamic control optimization system for a primary-side feedback control switching converter according to claim 4, characterized in that, The parameter calculation module determines the initial PID control parameter V after load switching. pi0 Estimated steady-state output voltage V after load switching o_stable2 Specifically, it includes: When mode_D switches from 0 to 1 or 2, let the current time be t1, and record the output voltage V at this time. o For v o (t1); Starting from time t1, after a known time interval Δt1, at time t2 = t1 + Δt1, let the output voltage V be recorded. o For v o (t2); Starting from time t2, after a known time interval Δt2, i.e. at time t3 = t2 + Δt2, let the output voltage V at this time be recorded. o For v o (t3); The estimated steady-state output voltage V after load switching o_stable2 for: Among them, I REF R2 is the output current, and R2 is the load impedance. Where C represents the output capacitor; Primary peak voltage V after load switching peak0 for: Among them, L p T represents the primary magnetizing inductance, η represents the transmission efficiency, and T represents the transmission efficiency. s0 =T s Set the initial PID control parameter V after load switching. pi0 =V peak0 .

7. A dynamic control optimization system for a primary-side feedback control switching converter according to claim 4, characterized in that, The optimization control module determines the diode average current reference value I. dREF Includes: the average current reference value I of the output diode when mode_D is 0. dREF That is, the target reference current I REF When mode_D is 1, the average current reference value I of the output diode is... dREF Set as current I d_high , among which, I d_high =I REF +ΔI1, parameter ΔI1 is based on the system parameter value; when mode_D is 2, the average current reference value of the output diode is I. dREF Set as current I d_low I d_low =I REF -ΔI2, where ΔI2 is based on the system parameter values.

8. A dynamic control optimization system for a primary-side feedback control switching converter according to claim 1, characterized in that, The PID compensation control module generates the control parameter V for the next cycle. pi This includes: Let mode_D_pre be the mode variable of the previous switching cycle; if mode_D_pre is 1 or 2, and mode_D is 0, then the control parameter V... pi Equal to the initial PID control parameter V after load switching pi0 Otherwise, the average current reference value I of the output diode will be used. dREF With the average current I of the output diode d The difference yields the error e(n), and based on the value of e(n), a new compensation value V is calculated using PID compensation control. pi .

9. A dynamic control optimization system for a primary-side feedback control switching converter according to claim 1, characterized in that, The PWM drive module uses a peak current control method to determine the switching period T. s The duty signal for the switching transistors in the main topology circuit.

10. A method for dynamic control optimization system of a primary-side feedback control switching converter based on any one of claims 1 to 9, characterized in that, Including the following steps: The output current prediction module is based on the auxiliary winding voltage V of the main topology circuit. sense Primary sampling voltage V p and the switching period T output by the PWM drive module s Predict the average current I of the output diode d And transmit it to the PID compensation control module; The output voltage sampling module is based on the auxiliary winding voltage V sense Sampling output voltage V o And transmit it to the dynamic optimization control module; The dynamic optimization control module adjusts the output voltage V based on the output voltage V. o This generates the average current reference value I of the output diode. dREF PID initial control parameters V after load switching pi0 And the dynamic mode variable mode_D, and pass it to the PID compensation control module; The PID compensation control module uses the dynamic mode variable mode_D and the average current reference value I of the output diode. dREF Average current I of output diode d Initial PID control parameters V after load switching pi0 This generates the control parameter V for the next cycle. pi And pass it to the PWM driver module; The PWM drive module determines the control parameter V based on the control parameter V. pi The switching period T of the next output cycle is determined by sampling the primary side information of the circuit topology. s The control signal duty of the switching transistor in the main topology circuit forms a closed loop with the main topology circuit, and the switching period T is... s Input to output current prediction module; Repeat the above steps to control the switching converter in the main topology circuit.

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