Half-bridge DC-DC converter and loop quick response control method

Abstract

The invention discloses a half-bridge DC-DC converter and a loop quick response control method, and belongs to the field of DC-DC converters, the half-bridge DC-DC converter comprises an output voltage loop, an output current loop, an input voltage feed-forward module, an output current overshoot quick response module and a peripheral module; the output voltage loop and the output current loop establish a parallel loop structure, and the smaller value of the output values of the output voltage loop and the output current loop is taken as a loop output initial value; the input voltage feed-forward module quickly adjusts a loop output value according to the change of the input voltage; the output current overshoot quick response module quickly adjusts a loop output value according to a difference value between a given value and a feedback value of an output current closed-loop input side; and the peripheral module controls the voltage of the switching tube driving pulse output end and the current of the output end to be quickly adjusted according to the loop output value. According to the invention, the dynamic response speed is accelerated, a good suppression effect is achieved on output voltage overshoot and large-amplitude overshoot of output current in an extremely short time, and the system stability is ensured while the loop response is improved.

Description

Technical Field

[0001] The invention relates to the field of DC-DC converters, in particular to a half-bridge DC-DC converter and a loop fast response control method. Background Art

[0002] Power electronic equipment is often affected by the environment or other equipment in the power system, causing instantaneous and drastic fluctuations in the input voltage, which will greatly affect the performance and output of the DC-DC converter. Output instability, i.e. overshoot / undershoot, can cause damage or shutdown of the back-end equipment. Therefore, it is necessary to suppress the impact of transient input voltage on the output voltage to prevent the output voltage from overshooting or undershooting significantly.

[0003] Although the digital control scheme has the advantages of simple control circuit and convenient debugging, the loop response speed is slow, which may cause the output to be out of control in the application environment with sudden load changes. For example, in a pulse load environment such as radar, the output current will rise sharply in a very short time of microseconds. If the loop response is not timely, it is very likely to damage the converter or cause the converter performance to deteriorate. The traditional PI loop regulator can achieve rapid loop adjustment to a certain extent by selecting PI adjustment parameters based on the input error value, but for the above application scenarios, safety hazards still exist. Summary of the invention

[0004] With regard to the above problems existing in the prior art, the object of the present invention is to provide a half-bridge DC-DC converter and a loop fast response control method to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A half-bridge DC-DC converter comprises an output voltage loop, an output current loop, an input voltage feedforward module, an output current overshoot fast response module and a peripheral module; the output voltage loop and the output current loop establish a parallel loop structure, a PI regulator is provided inside the output voltage loop and the output current loop, the input end of the PI regulator of the output voltage loop is connected to an input voltage given value VoutRef and an input voltage feedback value VoSense, the input end of the PI regulator provided inside the output current loop is connected to an input current given value IoutRef and an input current feedback value IoSense, and the smaller value output by the output end of the PI regulator of the output voltage loop and the output current loop is the loop output initial value;

[0007] The input end of the input voltage feedforward module is connected to the input voltage sampling VinSense, and the output of the input voltage feedforward module is a loop output value that is quickly adjusted according to the transient change of the input voltage sampling VinSense;

[0008] The input end of the output current overshoot fast response module is connected to the input end of the PI regulator provided inside the output current loop; the output of the output current overshoot fast response module is to quickly adjust the loop output value according to the difference between the input current given value IoutRef and the input current feedback value IoSense on the input side of the output current loop;

[0009] The loop output initial values ​​of the output voltage loop and the output current loop, the loop output value of the input voltage feedforward module, and the loop output value of the output current overshoot fast response module are the loop output final values. The loop output final value is connected to the input end of the peripheral module, and the output end of the peripheral module outputs four MOS tube drive signals to complete the rapid adjustment of the output voltage and the output current.

[0010] As a further solution of the present invention: the peripheral module is a DSP peripheral module DPWM unit.

[0011] A loop fast response control method for a half-bridge DC-DC converter comprises the following steps:

[0012] S1. After obtaining the current output voltage and output current ADC sampling data VoSense and IoSense, the PI regulators of the output voltage loop and the output current loop perform discrete transfer functions according to the preset given values ​​VoutRef and IoutRef and the deviation values ​​ErrorVo and ErrorIo of the feedback values ​​VoSense and IoSense ADC sampling values: Calculation, and then limit the calculation results to obtain the output values ​​of each loop; when the output current preset given value IoutRef is greater than the output current feedback value IoSens, that is, within the normal current limiting value range, the output current loop is in current limiting mode, and the output voltage loop is the main working loop; when the output current preset given value IoutRef is less than the output current feedback value IoSense, the output current loop is in constant current mode, and the output current loop is the main working loop;

[0013] S2, determine whether the difference ΔVin between the current sampling value VinSenseNow and the last sampling value VinSensePre of the input voltage is greater than the preset threshold ΔVinRef. If so, it indicates that the input voltage has undergone a transient and drastic change, and first switch to S3, enter the input voltage feedforward control module, and then switch to S4; if not, directly switch to S4;

[0014] S3, input voltage feedforward module according to formula G vin =Kc+Kf×ΔVin to calculate the gain value G vin ; Gain value G vinDirectly multiply the initial value of the loop output, and the result of the multiplication adjusts the duty cycle of the open-tube pulse to achieve a rapid response of the loop to the sudden and drastic changes in the input voltage;

[0015] S4, further judging whether the deviation value ErrorIo between the output current loop current given value IoutRef and the output current feedback value IoSense is greater than the set threshold ErrorIoSet. If so, it indicates that the output current has a large overshoot in a very short time, i.e., within microseconds, and the process goes to S5 to enter the output current overshoot fast response module; if not, it indicates that the output current is not in an overshoot situation, and the loop output value remains unchanged to avoid affecting the normal loop regulation;

[0016] S5. The output current overshoot fast response module directly multiplies the coefficient Ks by the initial value of the loop output, so that the duty cycle of the switch tube pulse is proportionally reduced, limiting the output current in a shorter time; directly adjusting the control loop output value, skipping the output current loop calculation, responding faster, and quickly suppressing current overshoot.

[0017] As a further solution of the present invention: Kp of the discrete transfer function in step S1 is the proportional coefficient in the PI control link, and Ki is the integral coefficient in the PI control link.

[0018] As a further solution of the present invention: in step S1, Kp and Ki are nonlinear values, which are adjusted by the deviation values ​​ErrorVo and ErrorIo through the Limit module. The larger the deviation value, the larger the selected Kp and Ki coefficients.

[0019] As a further solution of the present invention: the output voltage loop and the output current loop of step S1 are in parallel competition mode, the calculation results of the two loops are compared, and the smaller one is taken as the initial value of the control loop output of the digital control half-bridge DC-DC converter.

[0020] As a further solution of the present invention: the coefficient Kc in step S3 is 0.5-0.7, Kf is a nonlinear value, which is adjusted by ΔVin. The larger ΔVin is, the larger Kf is. When ΔVin is small, Kf is 0.

[0021] As a further solution of the present invention: the coefficient Ks in step S5 is calculated to be in the range of 0.5-0.8, and the smaller the value, the faster the response speed.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a digital control isolated half-bridge DC-DC converter loop control structure consisting of an output voltage closed loop, an output current closed loop, an input voltage feedforward module, an output current overshoot fast response module and a peripheral module, adds an input voltage feedforward and an output current overshoot fast response control module in the parallel loop control structure, directly adjusts the control amount of the isolated half-bridge DC-DC converter drive pulse, has a fast dynamic response speed, can effectively suppress the output voltage overshoot caused by the violent fluctuation of the input voltage and the output current overshoot within a very short time, i.e., microseconds, thereby improving the loop response and also ensuring the system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a loop control structure of a half-bridge DC-DC converter disclosed in an embodiment.

[0025] Figure 2 The schematic diagram of the hardware topology of a half-bridge DC-DC converter disclosed in the embodiment is shown.

[0026] Figure 3 The present invention is a schematic diagram of the principle of a PI regulator in a half-bridge DC-DC converter disclosed in an embodiment.

[0027] Figure 4 The present invention is a schematic diagram of the principle of an input feedforward module in a half-bridge DC-DC converter disclosed in an embodiment.

[0028] Figure 5 The present invention is a software flow chart of a loop control response of a half-bridge DC-DC converter control method disclosed in an embodiment. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention; it is obvious that 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.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", and "connected" should be understood in a broad sense; for example, it can be a fixed connection, a detachable connection, or an integral connection, a mechanical connection, or an electrical connection, a direct connection, or an indirect connection through an intermediate medium, or the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] See also Figure 1-3, a half-bridge DC-DC converter, comprising an output voltage loop, an output current loop, an input voltage feedforward module, an output current overshoot fast response module and a peripheral module;

[0032] The output voltage loop and the output current loop establish a parallel loop structure, and a PI regulator is provided inside the output voltage loop and the output current loop. The input end of the PI regulator of the output voltage loop is connected to the input voltage given value VoutRef and the input voltage feedback value VoSense, and the input end of the PI regulator provided inside the output current loop is connected to the input current given value IoutRef and the input current feedback value IoSense. The smaller value output by the output end of the PI regulator of the output voltage loop and the output current loop is the loop output initial value;

[0033] The input end of the input voltage feedforward module is connected to the input voltage sampling VinSense, and the output end of the input voltage feedforward module is a loop output value that is quickly adjusted according to the transient change of the input voltage sampling VinSense;

[0034] The input end of the output current overshoot fast response module is connected to the input end of the PI regulator provided inside the output current loop; the output end of the output current overshoot fast response module quickly adjusts the loop output value according to the difference between the input current given value IoutRef and the input current feedback value IoSense on the input side of the output current loop;

[0035] The loop output initial values ​​of the output voltage loop and the output current loop, the loop output value of the input voltage feedforward module, and the loop output value of the output current overshoot fast response module are the loop output final values. The loop output final value is connected to the input end of the peripheral module. The output end of the peripheral module controls the switch tube drive pulse in the isolated half-bridge DC-DC converter, thereby controlling the output voltage and output current.

[0036] The peripheral module is a DSP peripheral module DPWM unit.

[0037] A loop fast response control method for a half-bridge DC-DC converter comprises the following steps:

[0038] S1. After obtaining the current output voltage and output current ADC sampling data VoSense and IoSense, the PI regulators of the output voltage loop and the output current loop perform discrete transfer functions according to the preset given values ​​VoutRef and IoutRef and the deviation values ​​ErrorVo and ErrorIo of the feedback values ​​VoSense and IoSense ADC sampling values: Calculation, and then limit the calculation results to obtain the output values ​​of each loop; when the output current preset given value IoutRef is greater than the output current feedback value IoSens, that is, within the normal current limiting value range, the output current loop is in current limiting mode, and the output voltage loop is the main working loop; when the output current preset given value IoutRef is less than the output current feedback value IoSense, the output current loop is in constant current mode, and the output current loop is the main working loop;

[0039] In the discrete transfer function, Kp is the proportional coefficient in the PI control link, and Ki is the integral coefficient in the PI control link. Figure 3 As shown, Kp and Ki are nonlinear values. Through the above-mentioned deviation values ​​ErrorVo and ErrorIo, they are adjusted by the Limit module. The larger the deviation value, the larger the Kp and Ki coefficients are selected, so that the system can respond quickly and stably. Among them, the role of the proportional part is to quickly reduce the steady-state error of the system, so that the system can respond quickly to the target values ​​VoutRef and IoutRef; the integral role is to eliminate the steady-state error of the system, deal with small errors that exist for a long time, and ensure that the system can eventually reach the target values ​​VoutRef and IoutRef; the output voltage loop and the output current loop are in parallel competition mode, and the calculation results of the two loops are compared, and the smaller one is taken as the initial value of the control loop output of the digital control half-bridge DC-DC converter.

[0040] S2, determine whether the difference ΔVin between the current sampling value VinSenseNow and the last sampling value VinSensePre of the input voltage is greater than the preset threshold ΔVinRef. If so, it indicates that the input voltage has undergone a transient and drastic change, and first switch to S3, enter the input voltage feedforward control module, and then switch to S4; if not, directly switch to S4;

[0041] S3, input voltage feedforward module according to formula G vin =Kc+Kf×ΔVin to calculate the gain value G vin ; The coefficient Kc can be selected from 0.5-0.7, Kf is a nonlinear value, which is adjusted by ΔVin. The larger the ΔVin, the larger the Kf. When ΔVin is small, Kf is 0; the gain value G vin Directly multiply the initial value of the loop output, and the result of the multiplication adjusts the duty cycle of the open-tube pulse to achieve a rapid response of the loop to the sudden and drastic changes in the input voltage;

[0042] S4, further judging whether the deviation value ErrorIo between the output current loop current given value IoutRef and the output current feedback value IoSense is greater than the set threshold ErrorIoSet. If so, it indicates that the output current has a large overshoot in a very short time, i.e., within microseconds, and the process goes to S5 to enter the output current overshoot fast response module; if not, it indicates that the output current is not in an overshoot situation, and the loop output value remains unchanged to avoid affecting the normal loop regulation;

[0043] S5, the output current overshoot fast response module directly multiplies the coefficient Ks by the initial value of the loop output, so that the duty cycle of the switch tube pulse is proportionally reduced, and the output current is limited in a shorter time; directly adjust the output value of the control loop, skip the output current loop calculation, and respond faster, and can quickly suppress current overshoot; the coefficient Ks is calculated to have an optional range of 0.5-0.8, and the smaller the value, the faster the response speed.

[0044] The output voltage loop and output current loop PI regulator are connected in series with the loop output to form a dual loop fast response. The two work in coordination. If there is no drastic change in input voltage transients and the output current overshoots in a very short time (microseconds), the loop control only adjusts the Kp and Ki coefficients in the PI regulator to speed up the loop calculation. If the above situation exists, the loop output is directly adjusted to control the duty cycle of the converter drive pulse.

[0045] Combination Figure 2 The figure shows the hardware topology of an isolated half-bridge DC-DC converter, with a DC high voltage input at the input and a low voltage DC load at the output. Control principle and requirements: The converter system can generate a voltage VFin on the secondary side of the transformer by pulse driving the half-bridge primary switch tube. This voltage is linearly related to the input voltage, and the input voltage can be obtained by detecting the voltage at this point. The output voltage and output current are sampled through the sampling resistor to sample the output voltage and current signals, and the output average voltage and current sampling values ​​are obtained after hardware filtering. The hardware filter is usually composed of circuit elements, including low-pass, high-pass, band-pass and band-stop filters, etc., which are used to process signals and change the signal characteristics by enhancing or weakening the components of specific frequencies. "Lin" indicates the input filter inductor, "Cin1 / Cin2" indicates the input filter equalizing capacitor, "Lout" indicates the output power inductor, "Cout" indicates the output filter capacitor, "Riosense" indicates the output current sampling resistor, "MOS1\MOS2" indicates the primary half-bridge power switch tube, "Tr" indicates the high-frequency power transformer, and "MOS3\MOS4\MOS5\MOS6" indicates the secondary full-wave rectifier bridge power switch tube. Specifically, combined with Figure 2 and Figure 5The peripheral module generates PWM control signals "PWM1A", "PWM1B", "PWM2A" and "PWM2B", four MOS tube drive signals, and adjusts the duty cycle of the drive pulse according to the final value of the loop output to control the output voltage and output current.

[0046] The above loop control method, while utilizing the calculation of different PI adjustment parameters to accelerate the loop response speed, can also suppress the output voltage overshoot caused by the instantaneous and drastic fluctuation of the input voltage, and the output current overshoot within a very short time, i.e., microseconds, thereby accelerating the loop response speed of the isolated half-bridge DC-DC converter with dual fast loop calculation.

[0047] The input of the output voltage closed loop is the error value between the output voltage feedback value and the preset voltage set value. The output voltage closed loop PI loop regulator selects different PI adjustment parameters according to the error value to calculate the output value of the output voltage closed loop.

[0048] The input of the output current closed loop is the error value between the output current feedback value and the preset current given value. The output current closed loop PI loop regulator selects different PI adjustment parameters according to the error value to calculate the output value of the output current closed loop.

[0049] The present invention provides a digital control isolated half-bridge DC-DC converter loop control structure consisting of an output voltage closed loop, an output current closed loop, an input voltage feedforward module, an output current overshoot fast response module and a peripheral module, adds an input voltage feedforward and an output current overshoot fast response control module in the parallel loop control structure, directly adjusts the control amount of the isolated half-bridge DC-DC converter drive pulse, has a fast dynamic response speed, can effectively suppress the output voltage overshoot caused by the violent fluctuation of the input voltage and the large overshoot of the output current in a very short time (microseconds), improves the loop response and also ensures the system stability.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive from any point of view. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention, and any reference numerals in the claims should not be considered as limiting the claims involved.

[0051] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A half-bridge DC-DC converter, characterized in that: It includes an output voltage loop, an output current loop, an input voltage feedforward module, an output current overshoot fast response module and a peripheral module; the output voltage loop and the output current loop establish a parallel loop structure, a PI regulator is provided inside the output voltage loop and the output current loop, the input end of the PI regulator of the output voltage loop is connected to the input voltage given value VoutRef and the input voltage feedback value VoSense, the input end of the PI regulator provided inside the output current loop is connected to the input current given value IoutRef and the input current feedback value IoSense, and the smaller value output by the output end of the PI regulator of the output voltage loop and the output current loop is the loop output initial value; The input end of the input voltage feedforward module is connected to the input voltage sampling VinSense, and the output of the input voltage feedforward module is a loop output value that is quickly adjusted according to the transient change of the input voltage sampling VinSense; The input end of the output current overshoot fast response module is connected to the input end of the PI regulator provided inside the output current loop; The output of the output current overshoot fast response module is to quickly adjust the loop output value according to the difference between the input current given value IoutRef and the input current feedback value IoSense on the input side of the output current loop; The loop output initial values ​​of the output voltage loop and the output current loop, the loop output value of the input voltage feedforward module, and the loop output value of the output current overshoot fast response module are the loop output final values. The loop output final value is connected to the input end of the peripheral module, and the output end of the peripheral module outputs four MOS tube drive signals to complete the rapid adjustment of the output voltage and the output current.

2. A half-bridge DC-DC converter according to claim 1, characterized in that: The peripheral module is a DSP peripheral module DPWM unit.

3. A loop fast response control method for a half-bridge DC-DC converter according to any one of claims 1 to 2, characterized in that: The method steps are as follows: S1, after obtaining the current output voltage and output current ADC sampling data VoSense, IoSense, the PI regulator of the output voltage loop and the output current loop performs discrete transfer function according to the preset given values ​​VoutRef, IoutRef and the deviation values ​​ErrorVo, ErrorIo of the feedback values ​​VoSense, IoSense ADC sampling values: Calculation, and then limit the calculation results to obtain the output values ​​of each loop; when the output current preset given value IoutRef is greater than the output current feedback value IoSens, that is, within the normal current limiting value range, the output current loop is in current limiting mode, and the output voltage loop is the main working loop; when the output current preset given value IoutRef is less than the output current feedback value IoSense, the output current loop is in constant current mode, and the output current loop is the main working loop; S2, determine whether the difference ΔVin between the current sampling value VinSenseNow and the last sampling value VinSensePre of the input voltage is greater than the preset threshold ΔVinRef. If so, it indicates that the input voltage has undergone a transient and drastic change, and first switch to S3, enter the input voltage feedforward control module, and then switch to S4; if not, directly switch to S4; S3, input voltage feedforward module according to formula G vin =Kc+Kf×ΔVin to calculate the gain value G vin ; Gain value G vin Directly multiply the initial value of the loop output, and the result of the multiplication adjusts the duty cycle of the open-tube pulse to achieve a rapid response of the loop to the sudden and drastic changes in the input voltage; S4, further judging whether the deviation value ErrorIo between the output current loop current given value IoutRef and the output current feedback value IoSense is greater than the set threshold ErrorIoSet. If so, it indicates that the output current has a large overshoot in a very short time, i.e., within microseconds, and the process goes to S5 to enter the output current overshoot fast response module; if not, it indicates that the output current is not in an overshoot situation, and the loop output value remains unchanged to avoid affecting the normal loop regulation; S5. The output current overshoot fast response module directly multiplies the coefficient Ks by the initial value of the loop output, so that the duty cycle of the switch tube pulse is proportionally reduced, limiting the output current in a shorter time; directly adjusting the control loop output value, skipping the output current loop calculation, responding faster, and quickly suppressing current overshoot.

4. A half-bridge DC-DC converter and loop fast response control method according to claim 3, characterized in that: In the step S1, Kp of the discrete transfer function is the proportional coefficient in the PI control link, and Ki is the integral coefficient in the PI control link.

5. A half-bridge DC-DC converter and loop fast response control method according to claim 4, characterized in that: In step S1, Kp and Ki are nonlinear values, which are adjusted by the deviation values ​​ErrorVo and ErrorIo through the Limit module. The larger the deviation value, the larger the selected Kp and Ki coefficients.

6. A half-bridge DC-DC converter and loop fast response control method according to claim 5, characterized in that: The output voltage loop and the output current loop of step S1 are in parallel competition mode, and the calculation results of the two loops are compared, and the smaller one is taken as the initial value of the control loop output of the digital control half-bridge DC-DC converter.

7. A half-bridge DC-DC converter and loop fast response control method according to claim 6, characterized in that: The coefficient Kc in step S3 is 0.5-0.7, and Kf is a nonlinear value, which is adjusted by ΔVin. The larger ΔVin is, the larger Kf is. When ΔVin is small, Kf is 0.

8. A half-bridge DC-DC converter and loop fast response control method according to claim 7, characterized in that: The coefficient Ks in step S5 is calculated to be in the range of 0.5-0.8, and the smaller the value, the faster the response speed.

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