Transient frequency conversion control method of converter and electronic device

Abstract

The application provides a transient frequency conversion control method of a converter and an electronic device. The method comprises the following steps: determining the working state of the converter, wherein the working state comprises a light load working state and a heavy load working state; if it is determined that the working state switches between the light load working state and the heavy load working state, starting a transient frequency conversion control strategy to adjust the switching frequency of the converter, wherein the transient frequency conversion control strategy is used to adjust the duration of the freewheeling stage in the switching cycle of the converter; after the working state of the converter switches, and the clamping capacitor voltage sampling value of the converter v c satisfies a preset condition, exiting the transient frequency conversion control strategy to restore the switching frequency of the converter to normal. The dynamic response speed of the converter is effectively improved, and the overshoot and drop of the output voltage when the converter is subjected to a step load are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of converter technology, and in particular to a transient frequency conversion control method of a converter and an electronic device. BACKGROUND

[0002] In the application occasions of wide input and output range, isolated boost-buck converters (hereinafter uniformly described as converters in the present application) are widely used, such as LLC resonant converters and double-clamp zero-voltage switching converters. For such converters, when they work in the boost mode, by deducing the open-loop transfer function, it can be found that the right-half-plane zero point usually exists in the converters, and the frequency of the right-half-plane zero point is much lower than the switching frequency, which has a great influence on the stability of the converter.

[0003] In the prior art, in order to ensure the stability of the system, the tracking bandwidth of the converter is usually set to be low. When the converter is loaded with a step load, due to the low tracking bandwidth, the dynamic response speed is slow, which will cause a large overshoot or drop of the output voltage of the converter when the load steps. SUMMARY

[0004] The present application provides a transient frequency conversion control method of a converter and an electronic device, which can effectively improve the dynamic response speed of the converter and reduce the overshoot and drop of the output voltage of the converter when the converter is loaded with a step load.

[0005] In a first aspect, the present application provides a transient frequency conversion control method of a converter, comprising:

[0006] monitoring the working state of the converter, the working state comprising a light load working state and a heavy load working state; if it is monitored that the working state switches between the light load working state and the heavy load working state, starting a transient frequency conversion control strategy to adjust the switching frequency of the converter, the transient frequency conversion control strategy being used to adjust the duration of the freewheeling stage in the switching period of the converter; after the working state of the converter switches, and when the sampling value v c of the clamping capacitor voltage of the converter meets a preset condition, exiting the transient frequency conversion control strategy to restore the switching frequency of the converter to normal.

[0007] In a possible implementation, the transient frequency conversion control method of the converter provided by the present application comprises a transient frequency conversion control strategy,

[0008] the transient frequency conversion control strategy comprising a transient frequency increase control strategy and a transient frequency decrease control strategy, the transient frequency increase control strategy being used to shorten the duration of the freewheeling stage in the switching period of the converter when the working state switches from the light load working state to the heavy load working state, and the transient frequency decrease control strategy being used to lengthen the duration of the freewheeling stage in the switching period of the converter when the working state switches from the heavy load working state to the light load working state.

[0009] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the application comprises:

[0010] If the working state is switched from the light-load working state to the heavy-load working state, and the clamping capacitor voltage sampling value v c of the converter is lower than a first voltage V cref1 , a transient frequency conversion control strategy in the transient frequency conversion control strategy is started until the clamping capacitor voltage sampling value v c is not lower than a second voltage V cref2 , the second voltage V cref2 is greater than the first voltage V cref1 .

[0011] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the application comprises:

[0012] If the working state is switched from the heavy-load working state to the light-load working state, and the clamping capacitor voltage sampling value v c of the converter is higher than a third voltage V cref3 , a transient frequency conversion control strategy in the transient frequency conversion control strategy is started until the clamping capacitor voltage sampling value v c is not higher than a fourth voltage V cref4 , the third voltage V cref3 is greater than the fourth voltage V cref4 .

[0013] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the application is realized by a transient frequency conversion control module, and the transient frequency conversion control module comprises a period timing module and a frequency conversion control module,

[0014] The period timing module comprises a first comparison circuit, a second comparison circuit, a first logic circuit and a first feedback circuit. The output terminals of the first comparison circuit and the second comparison circuit are connected to the input terminals of the first logic circuit respectively, the output terminal of the first logic circuit is connected to the period control switch of the converter, the input terminal of the first feedback circuit is connected to the output terminal of the first logic circuit, and the output terminal of the first feedback circuit is connected to the input terminal of the first comparison circuit. The first feedback circuit is used for controlling the first comparison circuit, the first comparison circuit is used for limiting the highest switching frequency of the converter, and the second comparison circuit is used for monitoring the primary voltage of the converter. The input terminal of the frequency conversion control module is connected to the clamping capacitor voltage sampling module of the converter, the output terminal of the frequency conversion control module is connected between the first feedback circuit and the first comparison circuit, and the frequency conversion control module is used for controlling the input of the first comparator through the clamping capacitor voltage sampling value v c .

[0015] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the present application, the first comparison circuit comprises a first comparator, a first capacitor C1 and a first switch SW1, one end of the first capacitor C1 is connected with a first voltage-controlled current source VCCS1, the other end of the first capacitor C1 is grounded, the non-inverting input end of the first comparator is connected between the first capacitor C1 and the first voltage-controlled current source VCCS1, the inverting input end of the first comparator is connected with a first reference voltage V ref1 , one end of the first switch SW1 is connected with the non-inverting input end of the first comparator, and the other end of the first switch SW1 is grounded; the output end of the first feedback circuit is connected with the control structure of the first switch, and the conduction and closure of the first switch SW1 are controlled through the first feedback circuit.

[0016] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the present application, the frequency conversion control module comprises a second switch SW2 and a third comparison circuit.

[0017] The input end of the third comparison circuit is connected with a clamping capacitor voltage sampling module of the converter, the output end of the third comparison circuit is connected with the control structure of the second switch SW2; one end of the second switch SW2 is connected with the first feedback circuit, and the other end of the second switch SW2 is grounded; the third comparison circuit is used for controlling the second switch SW2 to be conducted when the clamping capacitor voltage sampling value v c * is lower than a first voltage V cref1 , until the clamping capacitor voltage sampling value v c * is not lower than a second voltage V cref2 , the second voltage V cref2 is greater than the first voltage V cref1 .

[0018] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the present application, the transient frequency conversion control module further comprises a soft exit circuit, the soft exit circuit comprises a resistor R2, a second capacitor C2 and a third switch SW3, one end of the resistor R2 is connected with a first reference voltage V ref1 , the other end of the resistor R2 is connected with the second capacitor C2, the other end of the second capacitor C2 is grounded, the connection point of the resistor R2 and the second capacitor C2 is connected with the inverting input end of the comparator 1, the third switch SW3 is connected with the second capacitor C2 in parallel, and the control structure of the third switch SW3 is connected with the frequency conversion control module, and the frequency conversion control module is used for controlling the conduction and closure of the third switch SW3.

[0019] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the present application, the frequency conversion control module comprises a second switch SW2 and a hysteresis comparator, the comparison threshold value of the hysteresis comparator is a first voltage V cref1 and a second voltage V cref2The input end of the hysteresis comparator is connected with the clamping capacitor voltage sampling module of the converter, and the output end of the hysteresis comparator is respectively connected with the control structure of the second switch SW2 and the control structure of the third switch SW3.

[0020] In a possible implementation, the transient frequency conversion control method of the converter provided by the embodiment of the present application further includes:

[0021] obtaining a clamping capacitor voltage sampling value v c of the converter; c determining an error signal v cref between the clamping capacitor voltage sampling value v e and a reference voltage V e adjusting the duration of the freewheeling stage in the switching period of the converter according to the error signal v

[0022] In a second aspect, the embodiment of the present application provides an electronic device for executing the transient frequency conversion control method of the converter provided by the first aspect and the optional mode of the first aspect of the present application, and the content and effects can be referred to the first aspect, and will not be described here.

[0023] The transient frequency conversion control method of the converter and the electronic device provided by the embodiment of the present application, when the working state of the converter is switched between the light load working state and the heavy load working state, the transient frequency conversion control strategy is started, the duration of the freewheeling stage in the switching period of the converter is adjusted, and then the switching frequency of the converter is adjusted, after the working state of the converter is switched, and when the clamping capacitor voltage sampling value v c of the converter satisfies the preset condition, the transient frequency conversion control strategy is exited, so that the switching frequency of the converter returns to normal, the dynamic response speed of the converter is effectively improved, and the overshoot and the drop of the output voltage when the converter is loaded with a step load are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0025] Figure 1 is a structural schematic diagram of a double-clamp zero-voltage switching converter in the prior art;

[0026] Figure 2 is a flowchart of the transient frequency conversion control method of the converter provided by an embodiment of the present application;

[0027] Figures 3A-3Bis a waveform schematic diagram provided by an embodiment of the application when the working state of the converter is switched;

[0028] Figures 4A-4B is a schematic diagram of the voltage change of the clamping capacitor provided by an embodiment of the application in the transient frequency conversion control strategy;

[0029] Figure 5 is a schematic diagram of the structure of the transient frequency conversion control module provided by an embodiment of the application;

[0030] Figure 6 is a schematic diagram of the structure of the transient frequency conversion control module provided by another embodiment of the application;

[0031] Figures 7A-7B is a waveform schematic diagram of the converter before the working of the frequency conversion control module provided by an embodiment of the application;

[0032] Figure 8 is a comparative waveform schematic diagram provided by an embodiment of the application before and after the transient frequency conversion control strategy is switched in;

[0033] Figure 9A is a waveform schematic diagram of the load current i o , the output voltage v o and the excitation inductance current i Lm after the light load is switched to the heavy load in the prior art;

[0034] Figure 9B is a partial enlarged schematic diagram in the dashed box in Figure 9A ;

[0035] Figure 10A is a waveform schematic diagram of the load current i o , the output voltage v o and the excitation inductance current i Lm after the transient frequency increase control strategy is enabled in an embodiment of the application;

[0036] Figure 10B is a partial enlarged schematic diagram in the dashed box in Figure 10A ;

[0037] Figure 11A is a waveform schematic diagram after the transient frequency increase control strategy is exited provided by an embodiment of the application;

[0038] Figure 11B is a partial enlarged diagram in the dashed box in Figure 11A ;

[0039] Figure 12 is a schematic diagram of the structure of the transient frequency conversion control module provided by still another embodiment of the application;

[0040] Figure 13is a control signal S of SW2 and SW3 provided by the embodiment of the application f 、v f potential and switching frequency f s schematic diagram of the state;

[0041] Figure 14 is a waveform schematic diagram of load current, output voltage and excitation inductance current after adding a soft exit circuit in the embodiment of the application;

[0042] Figure 15 is a flowchart of the transient frequency conversion control method of the converter provided by still another embodiment of the application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are some of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0044] The terms "first", "second", "third", "fourth" and the like (if any) in the specification and claims of the application and the above drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0045] In wide input and output range application occasions, isolated boost-buck converters are widely used, such as LLC resonant converters and double-clamp zero-voltage switching converters. For such converters, when they work in boost mode, by deriving their open-loop transfer function, it can be found that such converters usually have a right half plane zero point, and the frequency of the right half plane zero point is much lower than the switching frequency, which has a great influence on the stability of the converter.

[0046] As an isolated boost-buck converter with primary side feedback control, dual-clamp zero-voltage-switching (ZVS) converter has high power density, all switches can achieve soft switching, and is widely used. For ease of introduction, the method will be described in combination with the dual-clamp ZVS converter. It is worth noting that the method is not limited to this converter.

[0047] Figure 1 is a structural schematic diagram of the prior art dual-clamp ZVS converter. As shown in Figure 1 , the dual-clamp ZVS converter includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, and a fifth switch Q5, and a power transformer T. The converter has four working modes in a switching cycle, which are input energy storage stage, primary and secondary energy transmission stage, resonance stage, and freewheeling stage. The durations of each stage are T1-T4, which can be expressed as:

[0048]

[0049] Among them, v err is the output signal of the error amplifier in the converter, V in is the input voltage of the converter, v c is the voltage of the clamping capacitor C f , T s is the switching period of the converter, T s_min is the shortest switching period of the converter, which is mainly used to limit the highest switching frequency of the converter, and T Q4_ZVS is the time from the start of the converter cycle to the realization of zero-voltage turn-on of the fourth switch Q4. When the converter works in light load, T s_min >T Q4_ZVS , at this time T s =T s_min , the converter works in discontinuous conduction mode (DCM). When the converter works in heavy load, if T Q4_ZVS >T s_min , then T s =T Q4_ZVS , at this time the converter works in critical conduction mode (CRM), and the switching frequency of the converter is reduced compared with that in light load.

[0050] According to the law of conservation of energy, the relationship between the peak value i Lmax of the excitation inductance current and the load current i o can be approximately expressed as:

[0051]

[0052] Among them, f s L is the switching frequency of the converter. m This is the magnetizing inductance. According to... Figure 1 A schematic diagram of the dual-clamp zero-voltage switching converter in the diagram, i Lmax This can be further expressed as:

[0053]

[0054] Where v err Let k be the output signal of the error amplifier in the converter, and k be the proportionality coefficient. Substituting equation (3) into equation (2), we get:

[0055]

[0056] As can be seen from formula (4), when the converter has a step load, in order to quickly change the load current i of the converter... o Besides rapidly changing v err In addition, the switching frequency f of the converter can also be changed. s To achieve this.

[0057] When the converter load changes step, due to v err The change is relatively slow, and v can be approximated as such. err If the input energy storage stage duration T1 remains unchanged, then according to formula (1), the primary and secondary energy transfer stage duration T2 also remains approximately unchanged. The resonant stage duration T3, which is related to the parameters of the main circuit, also remains approximately unchanged. To adjust the converter's switching frequency f... s This can be achieved by adjusting the duration T4 of the continuous flow phase.

[0058] Based on this, the inventive concept of the transient frequency conversion control method and electronic device for the converter provided in this application is that, when the operating state of the converter switches between a light-load operating state and a heavy-load operating state, a transient frequency conversion control strategy is activated to adjust the duration of the freewheeling phase in the switching cycle of the converter, thereby adjusting the switching frequency of the converter. After the operating state of the converter switches, and the sampled value v of the clamping capacitor voltage of the converter... c *When preset conditions are met, the transient frequency conversion control strategy is exited so that the switching frequency of the converter can return to normal, effectively improving the dynamic response speed of the converter and reducing the overshoot and drop of the output voltage when the converter is driven by a step load.

[0059] Below, the transient frequency conversion control method of the converter and the electronic device provided by the embodiments of the present application are introduced. The transient frequency conversion control method of the converter and the electronic device provided by the embodiments of the present application can be implemented by an electronic device or a control module in the electronic device, and the embodiments of the present application do not limit this.

[0060] Figure 2 is a flowchart of the transient frequency conversion control method of the converter provided by an embodiment of the present application. Below, the transient frequency conversion control method of the converter is described with the electronic device as the execution subject. As shown in Figure 2 the method in the embodiments of the present application can include:

[0061] Step S101: monitoring the working state of the converter, the working state including a light load working state and a heavy load working state.

[0062] Step S102: if it is determined that the working state switches between the light load working state and the heavy load working state, starting a transient frequency conversion control strategy to adjust the switching frequency of the converter, the transient frequency conversion control strategy being used to adjust the duration of the freewheeling stage in the switching period of the converter.

[0063] Step S103: after the working state of the converter switches, and the clamping capacitor voltage sampling value v c of the converter meets the preset condition, exiting the transient frequency conversion control strategy to restore the switching frequency of the converter to normal.

[0064] The embodiments of the present application do not limit the specific implementation manner of how to monitor the working state of the converter. The specific implementation manner can be determined according to the scheme in the prior art, for example, the working state of the converter can be determined by monitoring the clamping capacitor voltage of the converter and / or the working current of the converter, and then it is determined whether the working state of the converter switches. If there is a switch, the transient frequency conversion control strategy is started to adjust the duration T4 of the freewheeling stage in the switching period of the converter to adjust the switching frequency of the converter. The embodiments of the present application do not limit the specific implementation manner of the transient frequency conversion control strategy. For example, the transient frequency conversion control strategy can be implemented in the form of software or hardware, as long as it can adjust the duration T4 of the freewheeling stage in the switching period of the converter to adjust the switching frequency of the converter. In addition, the embodiments of the present application do not limit the range of the duration T4 of the freewheeling stage in the switching period of the converter. The range can be set according to user demand.

[0065] In a possible implementation manner, the transient frequency conversion control method of the converter provided by the embodiments of the present application includes a transient frequency conversion control strategy, the transient frequency conversion control strategy including a transient frequency conversion control strategy and a transient frequency conversion control strategy,

[0066] The transient frequency increasing control strategy is used to shorten the duration of the freewheeling stage in the switching cycle of the converter when the working state is switched from the light load working state to the heavy load working state; the transient frequency decreasing control strategy is used to lengthen the duration of the freewheeling stage in the switching cycle of the converter when the working state is switched from the heavy load working state to the light load working state.

[0067] Figures 3A-3B is a waveform diagram provided by an embodiment of the application when the working state of the converter is switched, in the embodiment of the application, when the load of the converter is switched from the light load to the heavy load, the duration T4 of the freewheeling stage is reduced, for example, the duration T4 of the freewheeling stage can be reduced to zero, so as to realize the transient frequency increasing, as shown in Figure 3A ; when the load of the converter is switched from the heavy load to the light load, the duration T4 of the freewheeling stage is increased, so as to realize the transient frequency decreasing, as shown in Figure 3B .

[0068] In a possible implementation, when the load of the converter is switched from the light load to the heavy load, the clamping capacitor voltage v c of the converter drops, the transient frequency control method of the converter provided by the embodiment of the application comprises the following steps:

[0069] If the working state is switched from the light load working state to the heavy load working state, and the clamping capacitor voltage sampling value v c of the converter is lower than the first voltage V cref1 , the transient frequency increasing control strategy in the transient frequency control strategy is started until the clamping capacitor voltage sampling value v c is not lower than the second voltage V cref2 , and the second voltage V cref2 is greater than the first voltage V cref1 .

[0070] Figures 4A-4B is a clamping capacitor voltage change diagram of the transient frequency control strategy provided by an embodiment of the application. As shown in Figure 4A , when the load of the converter is switched from the light load to the heavy load, the clamping capacitor voltage v c of the converter drops, when the clamping capacitor voltage sampling value v c of the converter is lower than the first voltage V cref1 , the transient frequency increasing control strategy is switched in, so as to enhance the load capacity of the converter and inhibit the further drop of the clamping capacitor voltage; when the clamping capacitor voltage sampling value v c gradually recovers to the second voltage V cref2 , the converter approximately reaches the steady state, at this time, the transient frequency increasing control strategy is exited, the switching frequency of the converter is reduced, and the state of normal operation is restored.

[0071] In one possible implementation, when the converter switches from heavy load to light load, the clamping capacitor voltage v c Overshoot: The transient frequency conversion control method for converters provided in this application includes:

[0072] If the converter's operating state switches from heavy load to light load, and the sampled value of the converter's clamping capacitor voltage v c *Higher than the third voltage V cref3 When this happens, the transient frequency reduction control strategy in the transient frequency conversion control strategy is activated until the clamping capacitor voltage sampling value v is reached. c *Not higher than the fourth voltage V cref4 The third voltage V cref3 Greater than the fourth voltage V cref4 .

[0073] like Figure 4B As shown, when the clamping capacitor voltage sampling value v c *Higher than the third voltage V cref3 When the transient frequency reduction control strategy is activated, the converter's load-carrying capacity is reduced to suppress further increases in the clamp capacitor voltage; when the clamp capacitor voltage sampling value v c *Gradually decreases to the fourth voltage V cref4 When the converter approaches steady state, the transient frequency reduction control strategy is exited, and the switching frequency of the converter is increased to restore it to normal operation.

[0074] In this embodiment, when the converter's operating state switches between a light-load operating state and a heavy-load operating state, a transient frequency conversion control strategy is activated to adjust the duration of the freewheeling phase in the converter's switching cycle, thereby adjusting the converter's switching frequency. After the converter's operating state switches, and the sampled value v of the converter's clamping capacitor voltage... c *When preset conditions are met, the transient frequency conversion control strategy is exited so that the switching frequency of the converter can return to normal, effectively improving the dynamic response speed of the converter and reducing the overshoot and drop of the output voltage when the converter is driven by a step load.

[0075] The transient frequency up control strategy and the transient frequency down control strategy are implemented in a similar way. This embodiment takes the transient frequency up control strategy as an example and elaborates on the entry and exit mechanism of the transient frequency up control strategy in detail with the specific implementation circuit.

[0076] In one possible implementation, the transient frequency conversion control method for the converter provided in this application embodiment is implemented by a transient frequency conversion control module, wherein the transient frequency conversion control strategy is implemented. Figure 5 This is a schematic diagram of the structure of a transient frequency conversion control module provided in an embodiment of this application, as shown below. Figure 5 As shown, the transient frequency conversion control module includes: a periodic timing module and a frequency conversion control module.

[0077] The period timing module comprises a first comparison circuit, a second comparison circuit, a first logic circuit and a first feedback circuit; the output terminals of the first comparison circuit and the second comparison circuit are connected with the input terminals of the first logic circuit respectively, the output terminal of the first logic circuit is connected with the period control switch of the converter, the input terminal of the first feedback circuit is connected with the output terminal of the first logic circuit, and the output terminal of the first feedback circuit is connected with the input terminal of the first comparison circuit; the first feedback circuit is used for controlling the first comparison circuit to output a low level, the first comparison circuit is used for limiting the highest switching frequency of the converter, and the second comparison circuit is used for monitoring the primary voltage of the converter; the input terminal of the frequency conversion control module is connected with the clamping capacitor voltage sampling module of the converter, the output terminal of the frequency conversion control module is connected between the first feedback circuit and the first comparison circuit, and the frequency conversion control module is used for controlling the first feedback circuit and the first comparison circuit to output the high level signal through the clamping capacitor voltage sampling value v c * controls the input of the first comparator.

[0078] The embodiments of the present application do not limit the specific circuit structures of the first comparison circuit, the second comparison circuit, the first logic circuit, the first feedback circuit and the frequency conversion control module, as long as the purposes in the embodiments of the present application can be achieved. For example, the first comparison circuit can comprise a first comparator and a voltage input circuit, wherein the voltage input circuit can be connected with the positive input terminal of the first comparator, the inverting input terminal of the first comparator can be connected with a fixed voltage, and the first comparator can be controlled to output a high level signal at intervals of a preset period by comparing the voltage of the voltage input circuit with the fixed voltage. For another example, the voltage input circuit can be connected with the inverting input terminal of the first comparator, and the positive input terminal of the first comparator can be connected with a fixed voltage, so as to control the first comparator to output a low level signal at intervals of a preset period, and the like. In combination with other parts in the period timing module, the highest switching frequency of the converter can be limited.

[0079] In a possible implementation, the second comparison circuit can also comprise a second comparator, the input terminals of the second comparator are connected with the primary voltage of the converter and a preset reference voltage respectively, so as to monitor the primary voltage of the converter, and output a high level signal or a low level signal when the primary voltage of the converter reaches the preset reference voltage, and the like.

[0080] In a possible implementation, the first logic circuit can be an AND gate, a NOT gate, a NAND gate or the like, and the specific form of the first logic circuit is not limited in the embodiments of the present application. The specific form of the first logic circuit can be adaptively set according to the circuit structures of the first comparison circuit and the second comparison circuit, and the embodiments of the present application do not limit this.

[0081] In addition, the specific structure of the frequency conversion control module and the first feedback circuit is not limited in the embodiments of the present application, as long as the voltage sampling value v c of the clamping capacitor can be obtained .

[0082] In a possible implementation, Figure 6 is a structural schematic diagram of the transient frequency conversion control module provided by another embodiment of the present application, as shown in the figure, the transient frequency conversion control method of the converter provided by the embodiments of the present application includes a first comparison circuit, the first comparison circuit includes a first comparator (comparator 1), a first capacitor C1 and a first switch SW1, one end of the first capacitor C1 is connected with a first voltage-controlled current source VCCS1, the other end of the first capacitor C1 is grounded, the non-inverting input end of the first comparator is connected between the first capacitor C1 and the first voltage-controlled current source VCCS1, the inverting input end of the first comparator is connected with a first reference voltage V ref1 , one end of the first switch SW1 is connected with the non-inverting input end of the first comparator, and the other end of the first switch SW1 is grounded; the output end of the first feedback circuit is connected with the control structure of the first switch, and the conduction and closure of the first switch SW1 are controlled through the first feedback circuit.

[0083] The second comparison circuit can include a second comparator (comparator 2), the non-inverting input end of the comparator 2 is connected with a second reference voltage V ref2 , and the inverting input end of the comparator 2 is connected with the connection point between the third switch Q3 and the fourth switch Q4 (i.e. the primary side voltage v B of the converter) to ground voltage. Wherein, the controlled quantity of the first voltage-controlled current source VCCS1 can be a 5V reference voltage, Figure 6 , the current i c1 is the charging current of the first capacitor C1. The first logic circuit is an AND gate, S R is the output signal of the AND gate, and is also the reset signal of the system, which determines the starting time of the switching period and the switching period T s .

[0084] Before the frequency conversion control module works, the first capacitor C1 is charged to the first reference voltage V c1 through the first voltage-controlled current source VCCS1. ref1 When v B > V ref2 , the output of the comparator 1 is high, otherwise it is low; when v R < V s_min , the output of the comparator 2 is high, otherwise it is low. When the outputs of the comparator 1 and the comparator 2 are both high, S c is high, and the converter will start a new switching period. The introduction of the comparator 1 is to limit the highest switching frequency of the converter, and the introduction of the comparator 2 is to ensure that the fourth switch Q4 can realize zero-voltage turn-on.

[0085] When the converter is lightly loaded, the output of comparator 2 is first high, at which time the converter will start a new switching period only when the output of comparator 1 is high. Since the time T s_min is required for comparator 1 to be high, the switching frequency of the converter is not fixed.

[0086]

[0087] Therefore, the switching frequency of the converter is fixed when the converter is lightly loaded.

[0088] Figures 7A-7B is a waveform diagram of the converter before the variable frequency control module works, as shown in Figure 7A From the time when comparator 2 is high to the time when comparator 1 is high, the converter works in the freewheeling stage. As the load becomes heavier, the duration T4 of the freewheeling stage gradually shortens to zero. As shown in Figure 7B When the load of the converter continues to become heavier, the output of comparator 1 is first high, at which time the switching period of the converter is determined by comparator 2, and the heavier the load of the converter, the longer the switching period.

[0089] When the converter switches from light load to heavy load, if the sampling value v c of the clamping capacitor voltage drops to V cref1 Below, the cut-in mechanism of the transient frequency-varying control strategy is triggered, at which time the variable frequency control module controls the first switch SW1 in the first comparison circuit to be closed, and the first capacitor C1 cannot be discharged through the first switch SW1, and the voltage v c1 of the first capacitor C1 will gradually rise and maintain a high level, at which time the output of comparator 1 will always maintain a high level.

[0090] In a possible implementation, as shown in Figure 6 The transient frequency-varying control method of the converter provided in the embodiments of the present application includes a second switch SW2 and a third comparison circuit.

[0091] The input end of the third comparison circuit is connected with the clamping capacitor voltage sampling module of the converter, and the output end of the third comparison circuit is connected with the control structure of the second switch SW2; one end of the second switch SW2 is connected with the first feedback circuit, and the other end of the second switch SW2 is grounded; the third comparison circuit is used to control the second switch SW2 to be turned on when the sampling value v c of the clamping capacitor voltage of the converter is lower than the first voltage V cref1 , and to be turned off when the sampling value v c of the clamping capacitor voltage is not lower than the second voltage V cref2 , the second voltage V cref2 being greater than the first voltage V cref1 .

[0092] In the embodiment of the present application, the frequency conversion control module controls the sampling value v c of the clamping capacitor voltage of the converter to be lower than the first voltage V cref1 , and turns on the second switch to turn off the first switch. The embodiment of the present application does not limit the structure of the first switch SW1 and the second switch SW2. For example, the first switch SW1 and the second switch SW2 can be field effect tubes.

[0093] In a possible implementation, the third comparison circuit can be a hysteresis comparator, the output end of the hysteresis comparator is connected to the gate of the second switch SW2, and the drain and source of the second switch SW2 are respectively connected to the gate of the first switch SW1 and the ground. The embodiment of the present application is only used as an example and is not limited thereto.

[0094] Figure 8 is a comparison waveform diagram before and after the transient frequency conversion control strategy provided by the embodiment of the present application. As shown in Figure 8 , the freewheeling stage can be removed after the transient frequency conversion control strategy is turned on, and the switching frequency of the converter is improved. As can be seen from formula (4), the improvement of the switching frequency of the converter will effectively accelerate the response speed of the converter to the sudden load.

[0095] Figure 9A is a waveform diagram of the load current i o , the output voltage v o and the excitation inductor current i Lm after the light load is turned into the heavy load in the prior art. The output voltage v o drops by 300 mV. Figure 9B is a partial enlarged diagram in the dashed box in Figure 9A . It can be seen that the frequency of the excitation inductor current, that is, the switching frequency of the converter, changes slowly. Figure 10A is a waveform diagram of the load current i o , the output voltage v o and the excitation inductor current i Lm after the transient frequency conversion control strategy is enabled in the embodiment of the present application. The drop of the output voltage v o is reduced to 100 mV. Figure 10B is a partial enlarged diagram in the dashed box in Figure 10A . The frequency of the excitation inductor current, that is, the switching frequency of the converter, is rapidly improved.

[0096] When the converter gradually enters the steady state, the transient frequency conversion control strategy needs to be turned off, otherwise the converter will run at a high switching frequency, which reduces the efficiency of the converter. When the sampling value v c of the clamping capacitor voltage rises to v cref2 , the exit mechanism of the transient frequency conversion control strategy is triggered, and the output signal S fSW2 is off for low level.

[0097] If the converter still works in DCM in the new steady state, the converter will be directly switched from CRM to DCM by the transient frequency boost control strategy after the transient frequency boost control strategy exits. Figure 11A is a waveform schematic diagram provided by the embodiment of the application after the transient frequency boost control strategy exits, Figure 11B is Figure 11A The local enlarged view in the dashed box is shown in Figure 11A and Figure 11B As shown, the converter is switched from CRM to DCM, and due to the sudden reduction of the switching frequency of the converter, the load carrying capacity of the converter is weakened, and the output voltage v o experiences a large drop.

[0098] To solve the above technical problems, in a possible implementation, in Figure 6 the embodiment, the transient frequency boost control module further comprises a soft exit circuit. Figure 12 is a structural schematic diagram of a transient frequency boost control module provided by another embodiment of the application, as shown in Figure 12 The transient frequency boost control method of the converter provided by the embodiment of the application, the transient frequency boost control module further comprises a soft exit circuit, the soft exit circuit comprises a resistor R2, a second capacitor C2 and a third switch SW3, one end of the resistor R2 is connected with a first reference voltage V ref1 , the other end of the resistor R2 is connected with the second capacitor C2, the other end of the second capacitor C2 is grounded, the connection point of the resistor R2 and the second capacitor C2 is connected with the negative input end of the inverting input terminal of the comparator 1, the third switch SW3 is connected with the second capacitor C2 in parallel, and the control structure of the third switch SW3 is connected with the frequency boost control module, and the frequency boost control module is used to control the conduction and closure of the third switch SW3.

[0099] In a possible implementation, the frequency boost control module comprises a second switch SW2 and a hysteresis comparator, the comparison threshold of the hysteresis comparator is a first voltage V cref1 and a second voltage V cref2 , the input end of the hysteresis comparator is connected with the clamping capacitor voltage sampling module of the converter, and the output end of the hysteresis comparator is respectively connected with the control structure of the second switch SW2 and the control structure of the third switch SW3.

[0100] Figure 13 is a state schematic diagram of the control signal S f , the voltage v f and the switching frequency f s of the SW2 and SW3. The embodiment of the application will be introduced below in combination with Figure 12 and Figure 13 It is assumed that before the transient frequency boost control strategy is switched on, the load of the converter is light, and the converter works in DCM (steady state 1). At this time, the switching frequency fs The frequency of the output pulse of comparator 1 is determined by f1 (f s =f1), the reference value of comparator 1 is V. ref1 When the converter load changes from light load to heavy load, the clamping capacitor voltage sampling value v c *Drops to the first voltage V cref1 The following describes the triggering mechanism for the transient frequency converter control strategy, S. f When set to high level, the second switch SW2 and the third switch SW3 are turned on, and the first switch SW1 is blocked. Simultaneously, v... f The potential drops to zero, therefore the output of comparator 1 is always high. The operating frequency of the converter is determined by the output pulse frequency f2 of comparator 2, and f2 is constant. s =f2>f1; when the clamping capacitor voltage sampling value v c *Gradually rises to the second voltage V cref2 At that time, S f When set to low level, the third switch SW3 is turned off, and the first reference voltage V... ref1 Slowly charge the second capacitor C2, v f The voltage at the point also rises slowly. This is because the input signal v at the inverting input of comparator 1 is at this time... f With a lower amplitude, the output signal of comparator 1 goes high earlier than the output signal of comparator 2. At this time, the switching frequency f of the converter is... s It is still determined by the output pulse frequency f2 of comparator 2, i.e., f s =f2. With v f As the amplitude continues to increase, the high-level signal of comparator 1 is gradually delayed until v f =V ref3 At that time, the output signal of comparator 1 is set to high at the same time as the output signal of comparator 2. As v... f As the frequency increases further, the output signal of comparator 1 will be high later than the output signal of comparator 2. At this time, the switching frequency f of the converter will increase. s The frequency is determined by the output pulse frequency of comparator 1, and the frequency changes with v. f The point potential rises and then slowly decreases. When v f =V ref1 At this point, the converter's switching frequency drops to f1. This means the transient frequency ramp-up control strategy's soft-shutdown circuit allows the converter's operating frequency to gradually decrease to the steady-state operating frequency, reducing the impact on the converter.

[0101] It is worth noting that, in Figure 13 In the middle, S f During the high-frequency period, the switching frequency of the converter does not remain constant, but is affected by the output signal v of the error regulator. err The adjustment, Figure 13For the convenience of description, the adjustment process is simplified.

[0102] Figure 14 is the waveform diagram of the load current, output voltage and excitation inductance current after the soft exit circuit is added in the embodiment of the application, as shown in Figure 14 The voltage drop caused by the exit of the transient frequency increasing control strategy is greatly reduced, and the expanded graph of the A-C area is also given in the figure, from which it can be obtained that the switching frequency of the converter presents a slow decreasing trend with the exit of the transient frequency increasing control strategy, avoiding the severe impact introduced by the sudden change of the switching frequency of the converter, and the greater the time constant τ=R2C2 is, the slower the change of the switching frequency is, and the smaller the impact caused is.

[0103] Similarly, when the step load carried by the converter is switched from heavy load to light load, the output voltage will produce a certain overshoot. In order to reduce the overshoot, the transient frequency decreasing control strategy needs to be introduced to reduce the energy transferred from the primary side to the secondary side in unit time. The specific implementation mode is similar to that of the transient frequency increasing control strategy, and will not be described here. It is worth noting that the transient frequency decreasing control strategy also needs a corresponding soft exit mechanism.

[0104] In summary, in the case that the converter carries a step load, the transient frequency control strategy is introduced to achieve the effect of quickly adjusting the switching frequency of the converter, which can greatly reduce the drop and overshoot of the output voltage. Further, the soft exit mechanism of the transient frequency control strategy is further proposed to avoid the sudden change of the switching frequency of the converter caused by the exit of the transient frequency control strategy, and greatly reduce the impact on the converter caused by the exit of the transient frequency control strategy.

[0105] The above implementation method is only one of many implementations, and in a possible implementation mode, the transient frequency control method of the converter provided by the embodiment of the application can further include:

[0106] obtaining the clamping capacitor voltage sampling value v c of the converter; c determining the error signal v cref of the clamping capacitor voltage sampling value v e and the reference voltage V e ; and adjusting the duration of the freewheeling stage in the switching period of the converter according to the error signal v c .

[0107] In a possible implementation mode, Figure 15 is the flowchart of the transient frequency control method of the converter provided by another embodiment of the application, as shown in Figure 15 The embodiment of the application controls the duration T4 of the freewheeling stage by introducing a closed loop, when the clamping capacitor voltage sampling value v c deviates from the reference voltage V cref , and the error signal ve After passing through the band-pass filter and proportional amplification, the amplification factor is k p , to generate the adjustment amount ΔT4 of T4, and adjust T4.

[0108] The embodiment of the present application further provides an electronic device for executing the transient frequency conversion control method of the transformer provided by the above-mentioned embodiment of the present application, and the content and effects can be referred to the above-mentioned embodiment, and will not be described here.

[0109] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of transient variable frequency control of a converter, characterized by, The method comprises: monitoring the working state of the converter, the working state comprising a light load working state and a heavy load working state; if the working state of the converter switches between the light load working state and the heavy load working state, starting a transient frequency control strategy to adjust the switching frequency of the converter, the transient frequency control strategy being used to adjust the duration of the freewheeling stage in the switching cycle of the converter; After the working state of the converter is switched, and the clamping capacitor voltage sampling value v c When the preset condition is met, the transient frequency conversion control strategy is exited, so that the switching frequency of the converter returns to normal. the transient frequency control strategy comprising a transient frequency increase control strategy and a transient frequency decrease control strategy, the transient frequency increase control strategy being used to shorten the duration of the freewheeling stage in the switching cycle of the converter when the working state switches from the light load working state to the heavy load working state; the transient frequency decrease control strategy being used to lengthen the duration of the freewheeling stage in the switching cycle of the converter when the working state switches from the heavy load working state to the light load working state; If the working state is switched from the light-load working state to the heavy-load working state, and the clamping capacitor voltage sampling value v c of the converter is lower than a first voltage V cref1 , a transient frequency-rising control strategy in the transient frequency conversion control strategy is started until the clamping capacitor voltage sampling value v c is not lower than a second voltage V cref2 , the second voltage V cref2 is greater than the first voltage V cref1 . If the working state is switched from the heavy load working state to the light load working state, and the clamping capacitor voltage sampling value v c of the converter is higher than a third voltage V cref3 , a transient frequency reduction control strategy in the transient frequency conversion control strategy is started until the clamping capacitor voltage sampling value v c of the converter is not higher than a fourth voltage V cref4 , the third voltage V cref3 is greater than the fourth voltage V cref4 .

2. The method of claim 1, wherein, the transient frequency control strategy being realized by a transient frequency control module, the transient frequency control module comprising a cycle timing module and a frequency control module, wherein the cycle timing module comprises a first comparison circuit, a second comparison circuit, a first logic circuit and a first feedback circuit; the output terminals of the first comparison circuit and the second comparison circuit are respectively connected with the input terminal of the first logic circuit, the output terminal of the first logic circuit is connected with the cycle control switch of the converter, the input terminal of the first feedback circuit is connected with the output terminal of the first logic circuit, and the output terminal of the first feedback circuit is connected with the input terminal of the first comparison circuit; the first feedback circuit is used to control the output signal of the first comparison circuit, the first comparison circuit is used to limit the highest switching frequency of the converter, and the second comparison circuit is used to monitor the primary voltage of the converter; The input end of the variable frequency control module is connected with the clamping capacitor voltage sampling module of the converter, the output end of the variable frequency control module is connected between the first feedback circuit and the first comparison circuit, and the variable frequency control module is used for sampling the clamping capacitor voltage value v c controlling the input of the first comparison circuit.

3. The method according to claim 2, wherein The first comparison circuit comprises a first comparator, a first capacitor C1 and a first switch SW1, one end of the first capacitor C1 is connected with a first voltage-controlled current source VCCS1, the other end of the first capacitor C1 is grounded, the non-inverting input end of the first comparator is connected between the first capacitor C1 and the first voltage-controlled current source VCCS1, the inverting input end of the first comparator is connected with a first reference voltage V ref1 The first comparison circuit comprises a first comparator, a first capacitor C1 and a first switch SW1, one end of the first capacitor C1 is connected with a first voltage-controlled current source VCCS1, the other end of the first capacitor C1 is grounded, the non-inverting input end of the first comparator is connected between the first capacitor C1 and the first voltage-controlled current source VCCS1, the inverting input end of the first comparator is connected with a first reference voltage V the output terminal of the first feedback circuit is connected with the control structure of the first switch, and the conduction and closure of the first switch SW1 are controlled through the first feedback circuit.

4. The method of claim 3, wherein, the frequency control module comprises a second switch SW2 and a third comparison circuit, the input terminal of the third comparison circuit is connected with the clamping capacitor voltage sampling module of the converter, and the output terminal of the third comparison circuit is connected with the control structure of the second switch SW2; one end of the second switch SW2 is connected with the first feedback circuit, and the other end of the second switch SW2 is grounded; The third comparison circuit is configured to compare the clamping capacitor voltage sampling value v c * of the converter with a first voltage V cref1 * and to control the second switch SW2 to be conductive when the clamping capacitor voltage sampling value v c * is lower than the first voltage V cref2 * and to be non-conductive when the clamping capacitor voltage sampling value v cref2 * is not lower than the first voltage V cref1 .

5. The method of claim 3, wherein, The transient frequency conversion control module further comprises a soft exit circuit, the soft exit circuit comprises a resistor R2, a second capacitor C2 and a third switch SW3, one end of the resistor R2 is connected with a first reference voltage V ref1 The other end of the resistor R2 is connected with the second capacitor C2, the other end of the second capacitor C2 is grounded, the connection point of the resistor R2 and the second capacitor C2 is connected with the negative end of the inverting input end of a comparator 1, the third switch SW3 is connected with the second capacitor C2 in parallel, and the control structure of the third switch SW3 is connected with the frequency conversion control module, and the frequency conversion control module is used for controlling the conduction and closure of the third switch SW3.

6. The method of claim 5, wherein, The variable frequency control module comprises a second switch SW2 and a hysteresis comparator, a comparison threshold of the hysteresis comparator is a first voltage V cref1 and a second voltage V cref2 , an input end of the hysteresis comparator is connected with a clamping capacitor voltage sampling module of the converter, and output ends of the hysteresis comparator are respectively connected with a control structure of the second switch SW2 and a control structure of the third switch SW3.

7. The method according to any one of claims 1 to 6, characterized in that, the method further comprises: obtaining a clamping capacitor voltage sample value v of the converter c *; determining the clamped capacitor voltage sample value v c the error signal v cref between the reference voltage V e ; According to the error signal v e Adjusting the duration of the freewheel phase in the switching period of the converter.

8. An electronic device, comprising: a transient frequency control method for a converter as claimed in any one of claims 1-7.

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