Control circuit for digitally controlling input voltage of switching converter

Abstract

The embodiment of the invention provides a control circuit for digitally controlling input voltage of a switching converter. The control circuit comprises a main power circuit and a control circuit of the main power circuit, the main power circuit is a main power conversion circuit and is used for realizing voltage conversion; the control circuit is used for improving the dynamic performance of the switching converter in the fast transient state of input voltage. The control circuit comprises an integrator, a phase inverter, a voltage limiting circuit, an adder, a comparison circuit, a reset circuit and a microcontroller. The input end of the voltage limiting circuit is connected with the input end of the summator, the output end of the microcontroller is connected with the main power circuit, the input end of the phase inverter is connected with the output end of the integrator, the output end of the phase inverter is connected with the input end of the comparison circuit, and the output end of the comparison circuit is connected with the input end of the microcontroller. The input end of the reset circuit is connected with the output end of the microcontroller. And the purpose of improving the dynamic performance of the switching converter during transient overshoot of the input voltage is achieved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of switching converters, and in particular to a control circuit for digitally controlling an input voltage of a switching converter. Background Art

[0002] In various power supply systems, especially airborne power supply systems, in order to enhance system reliability, there are usually more than two primary power sources, such as the main power source composed of the main generator and the backup power source composed of batteries. When switching between different power sources, it is inevitable that there will be instantaneous power failure or instantaneous voltage overshoot, and the transient conversion time is usually in microseconds. In addition, under extremely harsh conditions, such as socket plug-in and unplug jitter, instantaneous voltage drops or overshoots will also occur.

[0003] With the development of technology, the requirements of electrical equipment for switching power supplies are constantly increasing. Digital control switching converters are widely used for their super flexibility, plasticity, and good anti-interference performance. Compared with analog control, digital control has inherent digital delays, cannot achieve real-time control, and its dynamic performance is generally poor. Therefore, when the input voltage changes transiently, especially when the microsecond instantaneous voltage overshoot occurs, the converter cannot respond immediately and there is a delay, which may cause the converter to shut down due to overcurrent protection, causing the electrical equipment to lose power. This is unacceptable in many applications, such as airborne power supply applications that require extremely high power quality.

[0004] One of the most direct and effective methods to solve the dynamic characteristics of switching converters when the input voltage changes transiently is to use peak current control. However, it still has certain application limitations. On the one hand, peak current control requires accurate switching cycle current sampling, which is generally achieved through non-inductive resistors or pulse current transformers. However, in high-power power supplies or applications that require a higher isolation level, these two types of sampling methods are no longer applicable; on the other hand, in wide-range input voltage applications, dual-tube or quad-tube Buck-Boost converters are generally used. When the voltage changes transiently, there is a switching process between Boost mode, BuckBoost mode and Buck mode, which naturally leads to dynamic performance deviations. In addition, due to the existence of mode switching, it generally works in valley current control mode in Buck mode and in peak current control mode in Boost mode, which makes it difficult to implement peak current control. At the same time, since the main control switch tube is always on, pulse current transformers cannot be used, and current sampling is more difficult, and it is generally only used in low-power applications.

[0005] Another effective way to solve the dynamic characteristics of switching converters when the input voltage changes transiently is to use input voltage feedforward control. Feedforward control can effectively improve the dynamic characteristics of converters in applications where the input voltage transient speed is slow. However, for voltage transients with transient conversion time of microseconds, as mentioned above, digital control has inherent digital delay, that is, the minimum 1-beat loading delay, which makes it difficult to effectively limit the internal current overshoot of the converter. In addition, in order to avoid interference introduced by input voltage sampling, filtering processing is required, which will introduce delay and further reduce the improvement effect of input voltage feedforward on dynamic characteristics. Summary of the invention

[0006] In view of this, an embodiment of the present specification provides a control circuit for digitally controlling the input voltage of a switching converter, so as to achieve the purpose of improving the dynamic performance of the switching converter when the input voltage transiently overshoots.

[0007] A control circuit for a digitally controlled switching converter input voltage, comprising:

[0008] A main power circuit and a control circuit of the main power circuit;

[0009] The main power circuit is the main power conversion circuit and is used to realize voltage conversion. The main power circuit includes an input bridge arm midpoint sampling signal V A , output voltage sampling signal V o and the inductor current sampling signal I L ;

[0010] The control circuit is used to improve the dynamic performance of the digital control switch converter when the input voltage is in a fast transient state. The control circuit includes an integrator, an inverter, a voltage limiting circuit, an adder, a comparison circuit, a reset circuit and a microcontroller;

[0011] Input bridge arm midpoint sampling signal V A Connected to the input of the integrator, the output voltage is sampled V o Connected to the voltage limiting circuit, the inductor current sampling signal I L The input end of the voltage limiting circuit is connected to the input end of the adder, the output end of the microcontroller is connected to the main power circuit, the input end of the inverter is connected to the output end of the integrator, the output end of the inverter is connected to the input end of the comparison circuit, the output end of the comparison circuit is connected to the input end of the microcontroller, and the input end of the reset circuit is connected to the output end of the microcontroller.

[0012] Furthermore, the main power circuit is a dual-tube Buck-Boost converter, and the dual-tube Buck-Boost converter includes a Buck first main control switch tube Q1 and a Boost second main control switch tube Q2;

[0013] The main power circuit also includes an input voltage sampling signal V in ;

[0014] The voltage limiting circuit includes a minimum value circuit and a slope damper. The input voltage sampling V in and output voltage sampling V o Both are connected to the input end of the minimum value circuit, and the output end of the minimum value circuit is connected to the input end of the slope damper.

[0015] Further, the minimum value circuit includes:

[0016] The minimum value circuit first input terminal, the minimum value circuit second input terminal and the minimum value circuit output terminal, the minimum value circuit is used to obtain the input voltage sampling signal V in And the output voltage sampling signal V o The smaller value of ;

[0017] The first input terminal of the minimum value circuit and the input voltage sampling signal V of the main power circuit in The minimum circuit second input terminal of the minimum circuit is connected to the output voltage sampling signal V o The minimum circuit output terminal is connected to the input terminal of the slope damper;

[0018] The slope damper comprises a slope damper input terminal and a slope damper output terminal, and the slope damper is used to control the change slope of the minimum circuit output;

[0019] The slope damper input terminal is connected to the minimum circuit output terminal of the minimum circuit, and the slope damper output terminal is connected to the input terminal of the adder.

[0020] Further, the microcontroller is a main control chip of the converter, which is used to generate the first drive control signal Q1, the second drive control signal Q2 and the control signal CLK;

[0021] The first driving control signal Q1 is connected to the Buck first main control switch Q1 of the main power circuit, and the second driving control signal Q2 is connected to the Boost second main control switch Q2 of the main power circuit;

[0022] The reset circuit comprises a first input terminal of the reset circuit, a second input terminal of the reset circuit and an output terminal of the reset circuit;

[0023] The first input terminal of the reset circuit is connected to the first drive control signal Q1 of the microcontroller, the second input terminal of the reset circuit is connected to the control signal CLK of the microcontroller, and the output terminal of the reset circuit is connected to the control electrode of the reset switch S of the integrator.

[0024] Furthermore, the main power circuit is a non-isolated Buck converter, and the non-isolated Buck converter includes a Buck main control switch tube Q1;

[0025] The microcontroller is a main control chip of the converter, and is used to generate a first drive control signal Q1, and the first drive control signal Q1 is connected to the Buck main control switch tube Q1 of the main power circuit;

[0026] The reset circuit comprises a reset circuit first input terminal and a reset circuit output terminal;

[0027] The first input terminal of the reset circuit is connected to the first driving control signal Q1 of the microcontroller, and the output terminal of the reset circuit is connected to the control electrode of the reset switch S of the integrator.

[0028] Further, the main power circuit is an isolated Buck converter, the isolated Buck converter includes a full-bridge converter, a half-bridge converter, a forward converter and a push-pull converter, and the isolated Buck converter includes a switch and a rectifier unit;

[0029] The microcontroller is the main control chip of the converter, which is used to generate a driving control signal for driving the switch tube and the rectifier tube in the switch and rectifier unit;

[0030] The reset circuit comprises a reset circuit first input terminal and a reset circuit output terminal;

[0031] The first input terminal of the reset circuit is connected to the output control signal CLK of the microcontroller, and the output terminal of the reset circuit is connected to the control electrode of the reset switch S of the integrator.

[0032] Further, the integrator comprises:

[0033] Integral resistance R int , Integral capacitor C int and operational amplifier OP1;

[0034] Integral resistance R int One end of the main power circuit input bridge arm midpoint sampling signal V A Phase connected, integrating resistor R int The other end is connected to the inverting input of the operational amplifier OP1, and the integrating capacitor C int One end is connected to the inverting input terminal of the operational amplifier OP1, and the integrating capacitor C int The other end is connected to the output end of the operational amplifier OP1, the non-inverting end of the operational amplifier OP1 is connected to the signal ground, and the output end of the operational amplifier OP1 is connected to the input end of the inverter as the output of the integrator.

[0035] Further, the inverter comprises:

[0036] Input resistance Rin , feedback resistor R F and operational amplifier OP2, the inverter is used to invert the integrated output to obtain a positive output;

[0037] Input resistance R in One end is connected to the output end of the integrator, and the input resistor R in The other end is connected to the inverting input of the operational amplifier OP2, and the feedback resistor R F One end is connected to the inverting input terminal of the operational amplifier OP2, and the feedback resistor R F The other end is connected to the output end of the operational amplifier OP2, the non-inverting end of the operational amplifier OP2 is connected to the signal ground, and the output end of the operational amplifier OP2 is connected to the comparison circuit as the output end of the inverter.

[0038] Further, the adder comprises:

[0039] The first input terminal of the adder, the second input terminal of the adder, the third input terminal of the adder, the output terminal of the adder and the fixed bias I bias ;

[0040] The first input terminal of the adder is connected to the slope damper output terminal of the slope damper, and the second input terminal of the adder is connected to the settable fixed bias I bias The third input terminal of the adder is connected to the inductor current sampling signal I L The adder output terminal is connected to the comparison circuit second input terminal of the comparison circuit.

[0041] Further, the comparison circuit comprises:

[0042] A first input terminal of a comparison circuit, a second input terminal of a comparison circuit and an output terminal of a comparison circuit;

[0043] The first input terminal of the comparison circuit is connected to the output terminal of the inverter, the second input terminal of the comparison circuit is connected to the output terminal of the adder, and the output terminal of the comparison circuit is connected to the input pin BRK of the microcontroller.

[0044] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in the embodiments of this specification include at least:

[0045] The dynamic performance improvement control method of the embodiment of the present invention overcomes the inherent delay disadvantage of digital control, realizes cycle-by-cycle volt-second product control, and effectively avoids overcurrent protection caused by input voltage transients. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 It is a block diagram of a main power circuit and a control circuit of a method for improving the transient performance of input voltage of a digitally controlled switching converter provided in an embodiment of the present invention;

[0048] Figure 2 This is a working waveform diagram of key points when the embodiment of the present invention works stably in Boost mode;

[0049] Figure 3 This is a working waveform diagram of key points when the embodiment of the present invention works stably in Buck mode;

[0050] Figure 4 This is a working waveform diagram of a key point when a transient overshoot occurs at the input in the Boost mode according to an embodiment of the present invention;

[0051] Figure 5 The working waveform diagram of the key points when transient overshoot occurs in the input of the embodiment of the present invention in Buck mode;

[0052] Figure 6 The working waveform diagram of the key points when the input has transient overshoot when switching from Boost mode to Buck mode in the embodiment of the present invention;

[0053] Figure 7 A block diagram of a main power circuit and a control circuit when an embodiment of the present invention is applied to a non-isolated Buck converter;

[0054] Figure 8 The embodiment of the present invention is applied to a main power circuit and a control circuit block diagram of an isolated Buck converter.

[0055] Reference numerals in the figure: 101, main power circuit; 102, integrator; 103, inverter; 104, minimum circuit; 105, slope damper; 106, adder; 107, comparison circuit; 108, reset circuit; 109, microcontroller. DETAILED DESCRIPTION

[0056] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0057] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0058] The embodiment of the present invention proposes a method for improving the transient performance of the input voltage of a digitally controlled switching converter. The method can achieve cycle-by-cycle current limiting, so that the converter can maintain normal operation and maintain the specified performance when the input voltage transient occurs, thereby reducing the impact on the electrical equipment. At the same time, the method does not require current sampling accurate to the switching cycle, which reduces the difficulty of use and can be quickly expanded to various topological applications.

[0059] A control method for improving the transient performance of input voltage of digital control switching converters, the core feature of which is to control the on-off of the source side switch bridge arm by sampling the rectangular wave voltage at the switch point of the source side bridge arm, and calculate its volt-second product in a switching cycle, thereby limiting the overshoot of the inductor current inside the converter. The working principle is as follows:

[0060] 1. Exactly the same as the traditional digital control method, the microcontroller 109, i.e., MCU, implements closed-loop control of the output voltage by sampling the output voltage. It can adopt a single voltage loop, average current control, or other available control methods. The microcontroller 109 outputs drive signals Q1 and Q2 with a certain timing sequence to drive the switch tube of the main power circuit 101. At the same time, it outputs a narrow pulse clock signal CLK in phase with the drive signal Q1 as a reset signal;

[0061] 2. Input voltage sampling signal V of the main power circuit in And the output voltage sampling signal V o The smaller value is taken through competition in the minimum value circuit, and the smaller value is sent to the slope damper to control its change slope to obtain the original reference voltage.

[0062] 3. The original reference voltage is added to the inductor current sampling signal and the adjustable constant bias to serve as the final reference voltage of the control variable. It should be noted that the inductor current feedback is only used for damping, so it is not necessary to sample accurately to the switching frequency, and the average value of the inductor current can be sampled.

[0063] 4. The integrator is used to integrate the rectangular wave voltage of the source side switch point to obtain the volt-second product on the left side of the inductor. Its output is inverted by the inverter and sent to the comparison circuit CMP1 as the control quantity to be compared with the above reference. When the value of the integrated control quantity is equal to the reference voltage, the comparator output flips to a high level, triggering the MCU to turn off the Buck main control switch tube drive and reset the integration circuit at the same time. At this time, since the switch tube is turned off, the volt-second applied to the inductor is reduced, thereby reducing the inductor current overshoot.

[0064] 5. When working in Boost mode, the duty cycle of the Buck master switch is always 1. In order to prevent the integrator from saturation, it is necessary to add a narrow pulse clock signal CLK with the same phase as the drive signal Q1 to periodically reset the integrator to ensure the normal operation of the circuit.

[0065] 6. In order not to affect the steady-state operation of the converter, the output of the integral control quantity should always be lower than the reference voltage, so the comparator output is always at a low level. The embodiment of the present invention proposes that the dynamic improvement circuit does not start working. When an overvoltage transient occurs at the input, the volt-second product of the source-side bridge arm increases, the dynamic improvement circuit starts working, turns off the Buck switch tube, limits the volt-second product on the inductor side, and then limits the inductor current to avoid overcurrent protection.

[0066] It can be seen from the above working principle that the control method proposed in the embodiment of the present invention only acts on the Buck bridge arm switch tube. Therefore, the main power circuit 101 in the embodiment of the present invention is not limited to the dual-tube Buck-Boost converter, and it can also adopt Buck-type converters, such as non-isolated Buck, full-bridge, half-bridge, etc.

[0067] Embodiment 1 (using a dual-tube Buck-Boost converter):

[0068] like Figure 1 As shown, the main power circuit 101 adopts a dual-tube Buck-Boost converter, wherein Q1 is a Buck main control switch tube (Buck first main control switch tube Q1), D1 is a Buck freewheeling diode, Q1 and D1 form a source side bridge arm, and its chopping point voltage is V A ; Q2 is the Boost main control switch tube (Boost second main control switch tube), D2 is the Boost freewheeling diode, and Q2 and D2 constitute the load side bridge arm.

[0069] The dual-tube Buck-Boost converter of the embodiment of the present invention has three operating modes. in >V o +△V, it works in Buck mode, and the Boost main control switch is always off, that is, its duty cycle D2 = 0; when V o +△V>V in >V o -△V, it works in Buck-Boost mode; when V in <V o -△V, it works in Boost mode, and the Buck main control switch is always on, that is, its duty cycle D1 = 1. Among them, the value of △V is very small, that is, the working range of Buck-Boost mode is very small, so it is ignored in subsequent processing.

[0070] refer to Figure 1 The control circuit of the embodiment of the present invention includes: an integrator 102, an inverter 103, a minimum circuit 104, a slope damper 105, an adder 106, a comparison circuit 107, a reset circuit 108 and a microcontroller 109.

[0071] Input bridge arm midpoint sampling signal VA Connected to one end of the integrator input, input voltage sampling V in and output voltage sampling V o The inductor current sampling signal I L Connected to the first input terminal of the adder 106, the drive control signal Q1 and the second drive control signal Q2 generated by the microcontroller 109 are respectively connected to the Buck main control switch tube Q1 and the Boost main control switch tube Q2 of the double-tube Buck-Boost.

[0072] Integrator 102 is composed of an integrating resistor R int , Integral capacitor Cint and operational amplifier OP1, which is used to integrate the source side midpoint voltage during the switching cycle. int One end of the main power circuit 101 is connected to the input bridge arm midpoint sampling signal V A The other end is connected to the inverting input terminal of the operational amplifier OP1; C int One end of is connected to the inverting input end of the operational amplifier OP1, and the other end is connected to the output end of OP1; the non-inverting end of OP1 is connected to the signal ground, and the output end of OP1 is connected to the input end of the inverter 103 as the output of the integrator 102.

[0073] The inverter 103 has an input resistor R in , feedback resistor RF and operational amplifier OP2, which are used to invert the integral output and obtain a positive output. in One end of R is connected to the output end of the integrator 102, and the other end is connected to the inverting input end of OP2; F One end of is connected to the inverting input end of OP2, and the other end is connected to the output end of OP2; the non-inverting end of OP2 is connected to the signal ground, and the output end of OP2 is connected to the comparison circuit 107 as the output end of the inverter 103.

[0074] Specifically, the integrator 102 and the inverter 103 are used to integrate and invert the voltage of the source side bridge arm chopping point to obtain the volt-second product within the switching period of the source side bridge arm chopping point as the final control quantity v c , whose expression is:

[0075] Among them, the integral constant satisfies R int C int =T s Therefore, in steady-state operation, when the input voltage remains unchanged, the final control quantity v c Can be simplified to: In the formula, when V in <Vo When D1=1, the steady-state control quantity is V in ; V in >V o , D2=0,D1V in =V o , so the size of the steady-state control quantity is V o Therefore, the original reference of the control quantity should be V in and V o The smaller value in .

[0076] The minimum value circuit 104 is used to obtain the input voltage sample V in and the output voltage V o The smaller value in is used as the final control quantity v c The original reference value, its output can be expressed as min(V in , V o ). Its first input terminal is connected to the input voltage sampling signal V of the main power circuit 101. in The second input terminal is connected to the output voltage sampling signal V of the main power circuit 101 o The output end is connected to the input end of the slope damper 105.

[0077] The slope damper 105 is used to limit the slope of the output of the minimum circuit 104 when the input voltage changes transiently. One end of the input of the slope damper 105 is connected to the output of the minimum circuit 104; one end of the output of the slope damper 105 is connected to the first input of the adder 106. The slope damper 105 outputs a smoothly changing reference voltage v refori , expressed as smooth(min(V in , V o )). This rate of change determines the transient conversion time. The longer the time, the smaller the current overshoot. At the same time, the smaller the dynamic overshoot reflected in the output voltage. The shorter the time, the greater the current overshoot and the shorter the adjustment time.

[0078] The adder 106 is used to control the superposition of variables and includes three input terminals, namely, a first input terminal, a second input terminal and a third input terminal. The first input terminal is connected to an output terminal of the slope damper 105, and the second input terminal is connected to a fixed bias I bias The third input terminal is connected to the inductor current sampling signal I of the main power circuit 101. L The output end of the adder is connected to the input end of the comparison circuit 107.

[0079] The adder 106 is used to adjust the reference v after being corrected by the slope damper 105. refori With the inductor current sampling I L and constant bias I bias Subtract, as the final reference vref , which can be expressed as: ref =smooth[min(V in ,V o )-I L +I bias ].

[0081] In order not to affect the normal loop operation, in steady state operation, v c Should always be less than v ref , that is, the following relationship should be satisfied:

[0082]

[0083] Under any load condition, the above formula must be satisfied. Therefore, I should be designed under the worst working condition, that is, full load condition. bias , at this time the inductor current reaches the maximum value I Lmax Therefore, the constant offset should satisfy: I bias >I Lmax .

[0084] The comparison circuit 107 is used to compare the control quantity with the reference quantity, so as to control the shutdown of the Buck bridge arm switch tube. The first input end of the comparison circuit is connected to the output end of the inverter 103; the second input end of the comparison circuit is connected to the output end of the adder 106; the output end is connected to the input pin BRK of the microcontroller 109 as its input to immediately shut down the switch tube.

[0085] The first input terminal of the reset circuit 108 is connected to the output control signal Q1 of the microcontroller 109 , the second output terminal is connected to the output control signal CLK of the microcontroller 109 , and the output terminal is connected to the control electrode of the reset switch S1 .

[0086] The reset circuit 108 is used to periodically reset the integrator 102 to prevent the output of the integrator 102 from saturating. It includes two input signals. Input signal 1 is the inverse signal of the Buck main control switch tube drive control signal Q1, which is used to determine the integration interval; input signal 2 is a narrow pulse width clock signal CLK with the same phase as the Buck drive timer. When working in the Boost mode, D1=1, signal 1 has no effect, and CLK periodically resets the integrator 102.

[0087] The microcontroller 109 serves as the main control chip of the converter, and outputs three control signals Q1, Q2 and CLK, which are respectively connected to the gates of the switch tubes Q1 and Q2 of the main power circuit 101 of the comparison circuit 107 and the reset circuit 108.

[0088] The microcontroller 109 completes the digital control algorithms such as output voltage closed loop, various protections, and logic functions by sampling the key information such as the output voltage and inductor current of the main power circuit 101. In theory, the closed-loop control can adopt a single voltage loop, average current control, or other available loop control methods. According to the closed-loop control algorithm, the MCU outputs drive signals Q1 and Q2 with a certain timing to drive the main power switch tubes Q1 and Q2 to achieve output voltage regulation. At the same time, the MCU also provides a narrow pulse clock signal CLK with the same phase as the drive signal Q1 as a reset clock signal. At present, typical commercial microcontrollers for switching power supplies generally have the function of shutting down PWM output in a single cycle, that is, the PWM output can be prohibited in real time in a single cycle through the external pin BRK. In an embodiment of the present invention, the output of the comparison circuit 107 is connected to BRK to prohibit the Buck drive signal in real time, thereby realizing cycle-by-cycle volt-second control, thereby limiting the inductor current.

[0089] Figure 2 and Figure 3 The key working waveforms of the dynamic performance improvement control method proposed by the present invention are given in Buck mode and Boost mode respectively when working in steady state. In the whole process under the two modes, the control quantity v c Always less than the reference value v ref , the output of comparator CMP1 is always at a low level, that is, the dynamic improvement circuit does not affect the operation of the closed-loop control circuit.

[0090] Figure 4 , Figure 5 and Figure 6 The working waveforms of each key point when transient overshoot occurs in the input in Boost mode, Buck mode and Buck-to-Boost mode are given respectively. The whole switching process is divided into three stages:

[0091] Phase 1: The converter operates at the first stable point. Figure 4 and Figure 6 The converter works in Boost mode. Figure 5 The converter works in Buck mode, at which time the output of the comparator CMP1 is always at a low level, and the dynamic improvement circuit of the present invention does not work.

[0092] The second stage: at t0, the input voltage rises stepwise. Due to the effect of the slope damper, the reference voltage ref Rising slowly at a slower speed, during which v ref <min(V in , V o ). At this time, due to the increase of input voltage, the control quantity v c The slope of the integral increases significantly, and the control quantity v c will be the same as the benchmark vref Early interception. When the control quantity v c With the benchmark v ref When they are equal, the output of the comparator CMP1 flips to a high level, triggering the microcontroller to turn off the drive signal Q1 of the Buck main control switch tube and reset the integration circuit at the same time.

[0093] Phase 3: In this phase, the benchmark v ref Increases to greater than min(V in , V o ), at this time the control quantity v c Always smaller than the base v ref , the comparator output is always at a low level, the dynamic improvement circuit is naturally switched out, and the converter enters the second stable point.

[0094] Embodiment 2 (using a non-isolated Buck converter or an isolated Buck converter):

[0095] It can be seen from the above working principle that the control method of the embodiment of the present invention only acts on the Buck bridge arm, so the method can be extended to Buck converters, such as non-isolated Buck converters (such as Figure 7 As shown), and isolated Buck converters such as half-bridge, full-bridge, push-pull, etc. (as shown Figure 8 For this type of converter, the volt-second voltage on the left side of the inductor, i.e. the chopping point, is always V o Therefore, the minimum value circuit 104 can be omitted at this time. In addition, generally speaking, the Buck converter has a duty cycle limit, so the Buck duty cycle will not be always on, so the narrow pulse clock signal can be omitted, that is, the reset circuit 108 becomes only one input source, such as Figure 8 In addition, only CLK can be used for reset, such as Figure 7 and Figure 8 shown.

[0096] refer to Figure 7 and Figure 8 The control circuit of the second embodiment includes: an integrator 102 , an inverter 103 , a voltage limiting circuit, an adder 106 , a comparison circuit 107 , a reset circuit 108 and a microcontroller 109 . The voltage limiting circuit includes a slope damper 105 .

[0097] Beneficial effects of the embodiments of the present invention:

[0098] The dynamic performance improvement control method proposed in the present invention overcomes the inherent delay disadvantage of digital control, realizes cycle-by-cycle volt-second product control, and effectively avoids overcurrent protection caused by input voltage transients; the embodiment of the present invention integrates the key voltage of the source side bridge arm, has a time accumulation effect, can effectively prevent the interference introduced by high-frequency sampling glitches, and has strong anti-interference ability; the introduction of the inductor current only has a damping effect on the current, so it is sufficient to sample the average value of the inductor current. Compared with traditional peak current control, there is no need to accurately sample the current in the switching cycle, which reduces the difficulty of current sampling and has strong scalability; the control method of the embodiment of the present invention does not affect the steady-state operation of the converter, and only starts working when the input voltage changes transiently. It is simple to implement and does not change the original control system architecture. Therefore, it can be embedded in any system without loss and has strong versatility.

[0099] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the patent protection scope of the present invention, should still fall within the scope of this patent. In addition, the technical features in the embodiments of the present invention can be freely combined with each other, with each other, and with each other.

Claims

1. A control circuit for digitally controlling the input voltage of a switching converter, characterized in that: include: A main power circuit (101) and a control circuit of the main power circuit (101); The main power circuit (101) is a main power conversion circuit and is used to realize voltage conversion. The main power circuit (101) includes an input bridge arm midpoint sampling signal V A , output voltage sampling signal V o and the inductor current sampling signal I L ; The control circuit is used to improve the dynamic performance of the digital control switch converter when the input voltage is in a fast transient state, and the control circuit comprises an integrator (102), an inverter (103), a voltage limiting circuit, an adder (106), a comparison circuit (107), a reset circuit (108) and a microcontroller (109); The input bridge arm midpoint sampling signal V A Connected to the input terminal of the integrator (102), the output voltage sampling V o is connected to the voltage limiting circuit, the inductor current sampling signal I L The microcontroller (109) is connected to the adder (106), the input end of the voltage limiting circuit is connected to the input end of the adder (106), the output end of the microcontroller (109) is connected to the main power circuit (101), the input end of the inverter (103) is connected to the output end of the integrator (102), the output end of the inverter (103) is connected to the input end of the comparison circuit (107), the output end of the comparison circuit (107) is connected to the input end of the microcontroller (109), and the input end of the reset circuit (108) is connected to the output end of the microcontroller (109).

2. The control circuit for digitally controlling the input voltage of a switching converter according to claim 1, characterized in that: The main power circuit (101) is a double-tube Buck-Boost converter, which comprises a Buck first main control switch tube Q1 and a Boost second main control switch tube Q2; The main power circuit (101) also includes an input voltage sampling signal V in ; The voltage limiting circuit comprises a minimum value circuit (104) and a slope damper (105), wherein the input voltage sampling V in and the output voltage sampling V o Both are connected to the input end of the minimum value circuit (104), and the output end of the minimum value circuit (104) is connected to the input end of the slope damper (105).

3. The control circuit for digitally controlling the input voltage of a switching converter according to claim 2, characterized in that: The minimum value circuit (104) comprises: A minimum value circuit first input terminal, a minimum value circuit second input terminal and a minimum value circuit output terminal, the minimum value circuit (104) is used to obtain the input voltage sampling signal V in and the output voltage sampling signal V o The smaller value of ; The first input terminal of the minimum value circuit is connected to the input voltage sampling signal V of the main power circuit (101). in The minimum circuit second input terminal of the minimum circuit (104) is connected to the output voltage sampling signal V of the main power circuit (101). o The minimum value circuit output terminal is connected to the input terminal of the slope damper (105); The slope damper (105) comprises a slope damper input terminal and a slope damper output terminal, and the slope damper (105) is used to control the change slope of the output of the minimum value circuit (104); The slope damper input terminal is connected to the minimum circuit output terminal of the minimum circuit (104), and the slope damper output terminal is connected to the input terminal of the adder (106).

4. The control circuit for digitally controlling the input voltage of a switching converter according to claim 2, characterized in that: The microcontroller (109) is a converter main control chip, used to generate a first drive control signal Q1, a second drive control signal Q2 and a control signal CLK; The first drive control signal Q1 is connected to the Buck first main control switch tube Q1 of the main power circuit (101), and the second drive control signal Q2 is connected to the Boost second main control switch tube Q2 of the main power circuit (101); The reset circuit (108) comprises a first input terminal of the reset circuit, a second input terminal of the reset circuit and an output terminal of the reset circuit; The first input end of the reset circuit is connected to the first drive control signal Q1 of the microcontroller (109), the second input end of the reset circuit is connected to the control signal CLK of the microcontroller (109), and the output end of the reset circuit is connected to the control electrode of the reset switch S of the integrator (102).

5. The control circuit for digitally controlling the input voltage of a switching converter according to claim 1, characterized in that: The main power circuit (101) is a non-isolated Buck converter, and the non-isolated Buck converter comprises a Buck main control switch tube Q1; The microcontroller (109) is a converter main control chip, used for generating a first drive control signal Q1, wherein the first drive control signal Q1 is connected to the Buck main control switch tube Q1 of the main power circuit (101); The reset circuit (108) comprises a reset circuit first input terminal and a reset circuit output terminal; The first input end of the reset circuit is connected to the first drive control signal Q1 of the microcontroller (109), and the output end of the reset circuit is connected to the control electrode of the reset switch S of the integrator (102).

6. The control circuit for digitally controlling the input voltage of a switching converter according to claim 1, characterized in that: The main power circuit (101) is an isolated Buck converter, which includes a full-bridge converter, a half-bridge converter, a forward converter and a push-pull converter, and includes a switch and a rectifier unit; The microcontroller (109) is a main control chip of the converter, and is used to generate a driving control signal for driving the switch and the switch tube and the rectifier tube in the rectifier unit; The reset circuit (108) comprises a reset circuit first input terminal and a reset circuit output terminal; The first input end of the reset circuit is connected to the output control signal CLK of the microcontroller (109), and the output end of the reset circuit is connected to the control electrode of the reset switch S of the integrator (102).

7. The control circuit for digitally controlling the input voltage of a switching converter according to claim 1, characterized in that: The integrator (102) comprises: Integral resistance R int , Integral capacitor C int and operational amplifier OP1; The integrating resistor R int One end of the input bridge arm midpoint sampling signal V of the main power circuit (101) A connected, the integrating resistor R int The other end is connected to the inverting input terminal of the operational amplifier OP1, and the integrating capacitor C int One end of the integrated capacitor C is connected to the inverting input terminal of the operational amplifier OP1. int The other end is connected to the output end of the operational amplifier OP1, the non-inverting end of the operational amplifier OP1 is connected to the signal ground, and the output end of the operational amplifier OP1 is connected to the input end of the inverter (103) as the output of the integrator (102).

8. The control circuit for digitally controlling the input voltage of a switching converter according to claim 1, characterized in that: The inverter (103) comprises: Input resistance R in , feedback resistor R F and operational amplifier OP2, the inverter (103) is used to invert the integrated output to obtain a positive output; The input resistance R in One end of the input resistor R is connected to the output end of the integrator (102). in The other end is connected to the inverting input terminal of the operational amplifier OP2, and the feedback resistor R F One end of the feedback resistor R is connected to the inverting input terminal of the operational amplifier OP2. F The other end is connected to the output end of the operational amplifier OP2, the non-inverting end of the operational amplifier OP2 is connected to the signal ground, and the output end of the operational amplifier OP2 is connected to the comparison circuit (107) as the output end of the inverter (103).

9. The control circuit for digitally controlling the input voltage of a switching converter according to claim 1, characterized in that: The adder (106) comprises: The first input terminal of the adder, the second input terminal of the adder, the third input terminal of the adder, the output terminal of the adder and the fixed bias I bias ; The first input terminal of the adder is connected to the slope damper output terminal of the slope damper (105), and the second input terminal of the adder is connected to the settable fixed bias I bias The third input terminal of the adder is connected to the inductor current sampling signal I of the main power circuit (101). L The adder output terminal is connected to the comparison circuit second input terminal of the comparison circuit (107).

10. The control circuit for digitally controlling the input voltage of a switching converter according to claim 1, characterized in that: The comparison circuit (107) comprises: A first input terminal of a comparison circuit, a second input terminal of a comparison circuit and an output terminal of a comparison circuit; The first input end of the comparison circuit is connected to the output end of the inverter (103), the second input end of the comparison circuit is connected to the output end of the adder (106), and the output end of the comparison circuit is connected to the input pin BRK of the microcontroller (109).

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