WO2024036790A1

WO2024036790A1 - Control device and method for flyback switch-mode power supply, and charger

Info

Publication number: WO2024036790A1
Application number: PCT/CN2022/132295
Authority: WO
Inventors: 朱况; 陈伟
Original assignee: 深圳英集芯科技股份有限公司
Priority date: 2022-08-19
Filing date: 2022-11-16
Publication date: 2024-02-22
Also published as: CN115065254A; CN115065254B; CN115776237A

Abstract

The present application provides a control device and method for a flyback switch-mode power supply, and a charger. The control device comprises a PWM logic module, and a valley detection module, a valley quantity determining module, and a peak current control module which are connected to the PWM logic module; the valley detection module detects valleys during operation of a flyback converter; the valley quantity determining module determines, by means of a feedback voltage, the quantity of valleys when a main power switch tube is switched on; the peak current control module obtains, according to the feedback voltage, a peak current signal when the main power switch tube is switched off, specifically: the peak current control module reduces the peak current signal by an offset when the quantity of valleys decreases, or increases the peak current signal by an offset when the quantity of valleys increases, so that transmission powers at adjacent valleys of the flyback converter overlap; the PWM logic module generates a PWM pulse for driving the main power switch tube. Embodiments of the present application can implement a valley locking function of flyback converters.

Description

Control device, method and charger of flyback switching power supply

This application claims priority for the Chinese patent application submitted to the China Patent Office on August 19, 2022, with the application number 202210995767.7 and the application name "Control device, method and charger for flyback switching power supply", and its entire content has been approved This reference is incorporated into this application.

Technical field

The present application relates to the field of electronic technology, and specifically to a control device, method and charger for a flyback switching power supply.

Background technique

Flyback switching power supply, also known as flyback converter, is widely used in low-power power supplies because of its simple circuit structure and low cost. In order to reduce switching losses, flyback converters generally open the resonance valley in DCM mode, which is called a quasi-resonant (QR) flyback converter.

The operating frequency of a switching power supply operating in QR mode is inversely proportional to the load, so the existing technology usually uses a maximum frequency clamp to limit the operating frequency range of the switching power supply. However, when this method is used, the operating power of the flyback converter at the valley switching operating point will suddenly change, and the operating power of the flyback converter will be discontinuous. Therefore, the flyback converter will operate between two or more valleys. jumps between times, causing the operating frequency of the converter to fluctuate violently, affecting system (electromagnetic compatibility, EMI) performance and generating audible noise. Therefore, the problem of how to implement the valley locking function of the flyback converter needs to be solved urgently.

Contents of the invention

Embodiments of the present application provide a control device, method and charger for a flyback switching power supply, which can realize the valley locking function of the flyback converter.

In a first aspect, embodiments of the present application provide a control device for a flyback switching power supply. The control device includes: a valley detection module, a valley number judgment module, a peak current control module and a PWM logic module; the valley detection module, The valley number judgment module and the peak current control module are both connected to the PWM logic module; the valley detection module is connected to the first pin of the control device, and the PWM logic module is connected to the second pin of the control device. pin and the third pin, the valley number judgment module and the peak current control module are both connected to the fourth pin of the control device;

The valley bottom detection module is used to detect the valley bottom during the operation of the flyback converter;

The valley number judgment module is used to determine the number of valleys when the main power switch is turned on by judging the feedback voltage;

The peak current control module is used to obtain the peak current signal when the main power switch is turned off according to the feedback voltage, specifically: the peak current control module reduces the peak current signal by one bias when the number of valleys decreases. Shift, or increase the peak current signal by an offset when the number of valleys increases, so that the transmission power between adjacent valleys of the flyback converter overlaps;

The PWM logic module generates PWM pulses that drive the main power switch.

In a second aspect, embodiments of the present application provide a control method for a flyback switching power supply, which is applied to the control device of a flyback switching power supply as described in the first aspect. The method includes:

The valley detection module detects the valley during the operation of the flyback converter;

The valley number judgment module determines the number of valleys when the main power switch is turned on by judging the feedback voltage;

The PWM logic module generates PWM pulses that drive the main power switch.

In a third aspect, embodiments of the present application provide a charger, which includes the control device described in the first aspect.

Implementing the embodiments of this application will have the following beneficial effects:

It can be seen that in the control device, method and charger of the flyback switching power supply described in the embodiments of this application, the control device includes: a valley detection module, a valley quantity judgment module, a peak current control module and a PWM logic module; valley detection module. The module, the valley number judgment module, and the peak current control module are all connected to the PWM logic module; the valley detection module is connected to the first pin of the control device, the PWM logic module is connected to the second pin and the third pin of the control device, and the valley number judgment module , the peak current control module are connected to the fourth pin of the control device; the valley detection module is used to detect the valley during the operation of the flyback converter; the valley number judgment module is used to judge the turn-on time of the main power switch through the feedback voltage The number of valleys; the peak current control module is used to obtain the peak current signal when the main power switch is turned off based on the feedback voltage, specifically: the peak current control module reduces the peak current signal by an offset when the number of valleys decreases, or When the number of valleys increases, the peak current signal is increased by an offset, so that the transmission power between adjacent valleys of the flyback converter coincides. The PWM logic module generates a PWM pulse that drives the main power switch tube, so that it can be controlled by The peak current value is used to expand the transmission power range of the converter in each valley state, so that the transmission power between adjacent valleys of the converter overlaps; specifically, the peak current control module reduces the peak current signal by one bias when the number of valleys decreases. Shift, or increase the peak current signal by an offset when the number of valleys increases, so that the transmission power between adjacent valleys of the converter overlaps, thus realizing the valley locking function of the flyback converter.

Description of drawings

In order to explain the embodiments of the present application or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic diagram of the operating frequency of a frequency clamp control method in related technology provided by an embodiment of the present application;

Figure 2 is a graph showing the relationship between the peak current signal and the feedback voltage signal of a frequency clamp control method in related technology provided by an embodiment of the present application;

Figure 3 is a schematic diagram of the operating power of a frequency clamp control method in related technology provided by an embodiment of the present application;

Figure 4 is a schematic diagram of a control device of a flyback switching power supply provided by an embodiment of the present application;

Figure 5 is a system circuit schematic diagram of a flyback switching power supply provided by an embodiment of the present application;

Figure 6 is a system circuit schematic diagram of another flyback switching power supply provided by an embodiment of the present application;

Figure 7 is a schematic structural diagram of the valley number determination module provided by the embodiment of the present application;

Figure 8 is a graph showing the relationship between the valley number signal and the feedback voltage signal provided by the embodiment of the present application;

Figure 9 is a schematic structural diagram of a peak current control module provided by an embodiment of the present application;

Figure 10 is a graph showing the relationship between the peak current signal and the feedback voltage signal provided by the embodiment of the present application;

Figure 11 is a schematic structural diagram of a PWM logic module provided by an embodiment of the present application;

Figure 12 is a schematic diagram of working power provided by the embodiment of the present application;

FIG. 13 is a schematic flowchart of a control method for a flyback switching power supply provided by an embodiment of the present application.

Detailed ways

In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions in the embodiments of the present application are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only for the purpose of this application. Some, but not all, of the embodiments of the application. Based on the description of the embodiments of this application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of this application.

The terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than describing a specific sequence. Furthermore, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, software, product or device that includes a series of steps or units is not limited to the listed steps or units, but also includes unlisted steps or units, or also includes the steps or units for these processes, methods. , other steps or units inherent to the product or equipment.

Reference herein to "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearances of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art understand, both explicitly and implicitly, that the embodiments described herein may be combined with other embodiments.

The embodiments of the present application will be introduced below with reference to the accompanying drawings. In the drawings, there are dots at the intersections of the intersecting conductors, which means that the conductors are connected, and there are no dots at the intersections, which means that the conductors are not connected.

In order to better understand the solutions of the embodiments of the present application, related terms and concepts that may be involved in the embodiments of the present application are first introduced below.

In the related art, Figure 1 is a schematic diagram of the operating frequency of the traditional frequency clamp control method. Figure 2 is a graph showing the relationship between the peak current signal and the feedback voltage signal of the traditional frequency clamp control method. Figure 3 is a schematic diagram of the operating power of the traditional frequency clamp control method. When the flyback converter is near the valley switching operating point, its operating power will mutate and the operating power will be discontinuous, resulting in frequent valley switching of the converter when the load power is at the intermittent operating power point. The specific reasons are as follows: If the load power is exactly at the power discontinuity point in the steady state of the load, for example, the power point corresponding to P1 in Figure 3, the operating power of the converter at the first valley is greater than the load power, and the converter operates at the second valley. The operating power at the valley bottom is less than the load power, so the converter will repeatedly switch between the first valley and the second valley operating states to make the output average power equal to the load power.

In order to solve the deficiencies in the related technology, please refer to Figure 4. Figure 4 is a schematic structural diagram of a control device for a flyback switching power supply provided by an embodiment of the present application. The control device includes: a valley detection module and a valley quantity judgment module. , peak current control module and PWM logic module; the valley bottom detection module, the valley bottom number judgment module, and the peak current control module are all connected to the PWM logic module; the valley bottom detection module is connected to the first terminal of the control device Pin VS, the PWM logic module is connected to the second pin VG and the third pin CS of the control device, and the valley number judgment module and the peak current control module are both connected to the fourth pin of the control device. foot FB;

The valley number judgment module is used to determine the number of valleys when the main power switch Q1 is turned on by judging the feedback voltage;

The peak current control module is used to obtain the peak current signal when the main power switch Q1 is turned off according to the feedback voltage. Specifically, the peak current control module reduces the peak current signal by one when the number of valleys decreases. Offset, or when the number of valleys increases, the peak current signal is increased by an offset, so that the transmission power between adjacent valleys of the flyback converter coincides;

The PWM logic module generates PWM pulses that drive the main power switch Q1.

Among them, it uses the feedback voltage to determine the number of valleys when the main power switch is turned on. At the same time, it controls the peak current value to expand the transmission power range of the converter in each valley state, so that the transmission power between adjacent valleys of the converter overlaps. , to avoid power discontinuity near the valley switching operating point and causing the converter to repeatedly switch to valley. Among them, the reduced or increased offset should make the transmission power between adjacent valleys of the converter coincide.

Optionally, the first pin VS is used to connect to a flyback converter. The flyback converter includes an auxiliary winding, a primary winding and a secondary winding. One end of the auxiliary winding is connected to the first pin. VS and the other end are grounded; one end of the primary winding is connected to the external power supply and the other end is connected to the first end of the main power switch Q1; one end of the secondary winding is connected to one end of the diode and the other end is grounded; so The other end of the diode D1 is connected to the fourth pin FB through the feedback and isolation module;

The PWM logic module is connected to the second end of the main power switch Q1 through the second pin VG, and the PWM logic module is connected to the third end of the main power switch Q1 through the third pin CS. terminal and grounded through the sampling resistor R _sense .

Among them, as shown in Figure 5, the first pin VS is used to connect the flyback converter. The flyback converter includes an auxiliary winding, a primary winding and a secondary winding. One end of the auxiliary winding is connected to the first pin VS and the other end. Grounded; one end of the primary winding is connected to the external power supply and the other end is connected to the first end of the main power switch Q1; one end of the secondary winding is connected to one end of the diode D1 and the other end is grounded; the other end of the diode D1 passes through the feedback and isolation module Connect the fourth pin FB; the PWM logic module is connected to the second end of the main power switch Q1 through the second pin VG, and the PWM logic module is connected to the third end of the main power switch Q1 through the third pin CS and the sampling resistor. R _sense is grounded.

In specific implementation, the current size can be sampled by the voltage of the sampling resistor.

Among them, one end of the primary winding can also be grounded through a capacitor (C _in ), and the output end of the diode D1 can also be grounded through a capacitor (C _o ).

Optionally, the first pin VS is used to connect the flyback converter, which includes an auxiliary winding, a primary winding and a secondary winding;

One end of the auxiliary winding is connected to the first pin VS and the other end is grounded; one end of the primary winding is connected to an external power supply and the other end is connected to the MOS integrated system; one end of the secondary winding is connected to one end of diode D1 and the other end is grounded; the other end of the diode is connected to the fourth pin FB through the feedback and isolation module;

The PWM logic module is connected to the MOS integrated system through the second pin VG and the third pin CS. The MOS integrated system includes a main power switch tube.

In the specific implementation, as shown in Figure 6, the first pin VS is used to connect the flyback converter. The flyback converter includes an auxiliary winding, a primary winding and a secondary winding; one end of the auxiliary winding is connected to the first pin VS and The other end is grounded; one end of the primary winding is connected to the external power supply (V _in ) and the other end is connected to the MOS integrated system (Mosfet System); one end of the secondary winding is connected to one end of the diode D1 and the other end is grounded; the other end of the diode passes through feedback The fourth pin FB is connected to the isolation module; the PWM logic module is connected to the MOS integrated system through the second pin VG and the third pin CS. The MOS integrated system includes the main power switch tube.

In specific implementation, MOS can be integrated into a small system, that is, a MOS integrated system. This system can directly output a voltage signal reflecting the size of the current without adding a sampling resistor.

In specific implementation, the peak current control module reduces the peak current signal by an offset when the number of valleys decreases, or increases the peak current signal by an offset when the number of valleys increases, so that the transmission power between adjacent valleys of the converter is Coincidence occurs; the peak current control module can only obtain the peak current signal V _{cs_ref} when the main power switch is turned off based on the feedback voltage signal V _FB of the FB pin, or it can also be combined with the valley number signal to obtain the peak current signal V cs_ref when the main power switch is turned off. The peak current signal V _{cs_ref} and the control module that controls the value of the peak current signal to cause the transmission power between adjacent valleys of the converter to overlap are all extensions and deformations of the peak current control module, and all belong to the protection scope of the embodiments of this application.

Optionally, the valley detection module is used to sample the voltage of the first pin VS pin, detect the valley during the operation of the flyback converter and generate a valley signal, and transmit the valley signal to the Described PWM logic module;

The valley quantity judgment module is used to determine the valley quantity signal when the main power switch is turned on based on the feedback voltage of the fourth pin FB, and transmit the valley quantity signal to the PWM logic module;

The peak current control module is used to control to obtain the peak current signal when the main power switch is turned off according to the feedback voltage signal of the fourth pin FB, specifically: the number of the peak current control module decreases at the bottom When the peak current signal is reduced by an offset, or when the number of valleys increases, the peak current signal is increased by an offset, and the peak current signal is transmitted to the PWM logic module;

The PWM logic module is used to generate and drive the main power switch according to the valley signal, the valley number signal when the main power switch is turned on, the peak current signal and the third pin CS voltage signal. PWM pulse, the PWM pulse signal is output through the second pin VS.

Among them, the valley detection module is used to sample the VS pin voltage, detect the valley during the operation of the flyback converter and generate a valley signal Valley, and pass the generated valley signal Valley to the PWM logic module. The valley quantity judgment module is used to determine the valley quantity signal Valley_N when the main power switch is turned on based on the feedback voltage V _FB of the FB pin, and transfer the valley quantity signal Valley_N to the PWM logic module. The peak current control module is used to control the peak current signal V _{cs_ref} when the main power switch is turned off based on the feedback voltage signal V _FB of the FB pin. Specifically, the peak current control module reduces the peak current signal by one when the number of valleys decreases. offset, or increase the peak current signal by an offset when the number of valleys increases, and pass the peak current signal V _{cs_ref} to the PWM logic module. The PWM logic module is used to generate a PWM pulse to drive the main power switch based on the valley signal Valley, the valley number signal Valley_N when the main power switch is turned on, the peak current signal V _{cs_ref} and the CS pin voltage signal V _cs . The PWM pulse signal passes through VG pin output.

Optionally, as shown in Figure 7, the valley number judgment module includes a first comparator, a second comparator, a third comparator, a fourth comparator, a fifth comparator, a sixth comparator, a priority decoding , the first adder and the data register; the feedback voltage signal of the fourth pin is connected to the first comparator, the second comparator, the third comparator, the fourth comparator, The negative input terminals of the fifth comparator and the sixth comparator;

The positive input terminals of the first comparator, the second comparator, the third comparator, the fourth comparator, the fifth comparator and the sixth comparator are respectively connected to the first valley. reference signal, the second valley reference signal, the third valley reference signal, the fourth valley reference signal, the fifth valley reference signal and the sixth valley reference signal, wherein the voltage at the positive input terminal of any comparator is higher than the voltage at the negative input terminal When The four input terminals A3, the fifth input terminal A4, the sixth input terminal A5 and the seventh input terminal A6 are respectively connected to the first comparator, the second comparator, the third comparator and the fourth comparator. The output terminals of the second comparator, the fifth comparator and the sixth comparator;

The output end of the priority decoder is connected to the first input end of the first adder and the second input end of the first adder is connected to a preset circuit module, and the preset circuit module is used to generate a constant 1 ; The priority decoder decodes the result of the comparator; the first adder adds 1 to the decoding result to obtain the valley number when the main power switch is turned on; the data input terminal of the data register Connect the output end of the first adder; the enable end of the data register is connected to the turn-on signal of the main power switch; the output end of the data register outputs a valley quantity signal; the data register is used to After the main power switch is turned on, the input valley number is latched to prevent the valley number from jumping due to fluctuations in the feedback voltage signal within one cycle.

The preset circuit module can be any module that can generate a constant 1.

Among them, the negative input terminals of the first comparator, the second comparator, the third comparator, the fourth comparator, the fifth comparator and the sixth comparator are all connected to the feedback voltage signal V _FB , and the positive input terminal of the first comparator terminal is connected to V1, the positive input terminal of the second comparator is connected to V2, the positive input terminal of the third comparator is connected to V3, the positive input terminal of the fourth comparator is connected to V4, and the positive input terminal of the fifth comparator is connected to Enter V5, and the positive input end of the sixth comparator is connected to V6. The priority decoder can include 8 input pins, namely A0, A1, A2, A3, A4, A5, A6, and A7. Among them, A0 and A7 are connected to ground, and A1, A2, A3, A4, A5, and A6 are connected in sequence. Enter the output terminals of the first comparator, the second comparator, the third comparator, the fourth comparator, the fifth comparator, and the sixth comparator. The priority decoder may also include three output pins, namely D0, D1, and D2, all of which are connected to the first input end of the first adder. The data register includes 3 input pins, namely A0, A1, and A2, which are connected to the output of the first adder. The data register also includes 3 output pins, namely: D0, D1, and D2. Through the 3 Each output pin outputs the valley number signal Valley_N.

In the specific implementation, as shown in Figure 8, Figure 8 is a graph showing the relationship between the valley number signal and the feedback voltage signal based on the present application. The specific working process of the valley number judgment module is as follows: preset the valley reference voltage in the valley number judgment module, Compare the feedback voltage signal V _FB with the set valley reference voltage signal. The priority decoder decodes the result of the comparator. The first adder adds 1 to the decoded result to obtain the valley when the main power switch is turned on. Quantity, the data register latches the input valley quantity after the switch is turned on, and the data register outputs the valley quantity signal Valley_N.

Optionally, as shown in Figure 9, the peak current control module includes a selector, a subtractor (-) and a second adder (+);

The data input terminals of the selector are respectively connected to the first reference signal V _ref1 , the second reference signal V _ref2 , the third reference signal V _ref3 , the fourth reference signal V _ref4 , the fifth reference signal V _ref5 and the sixth reference signal V _ref6; The data selection terminal of the selector is connected to the valley quantity signal (Valley_N); the output terminal of the selector is connected to the negative input terminal of the subtractor; the selector selects the corresponding reference signal according to the valley quantity signal And output the selected reference signal to the negative input terminal of the subtractor; the feedback voltage signal (V _FB ) is connected to the positive input terminal of the subtractor, and is connected to the positive input terminal of the subtractor through the first proportional link (1/Kv) The first input terminal of the second adder; the output terminal of the subtractor is connected to the second input terminal of the second adder through the second proportional link (1/K ₁ ); the second input terminal of the second adder is The output terminal outputs the peak current signal V _{cs_ref} .

Among them, the first proportional link and the second proportional link are used to realize a certain scaling function.

Among them, as shown in Figure 10, it is a graph of the relationship between the peak current signal and the feedback voltage signal based on this application. The specific working process of the peak current control module is as follows: the selector selects the corresponding reference signal according to the valley number signal Valley_N. The signal and the preset proportional coefficient can generate the peak current signal V _{cs_ref} , and V _{cs_ref} can be obtained by the following formula:

Where V _ref is the reference voltage selected by the selector.

Among them, the proportion coefficient can be preset or system default.

Optionally, the peak current signal generated by the peak current control module is used to overlap the transmission power between two adjacent valleys.

Among them, the peak current signal V _{cs_ref} generated by the peak current control module should cause the transmission power between two adjacent valleys to overlap, thereby avoiding discontinuity in the operating power of the converter at the valley switching operating point and causing the converter to repeatedly switch valleys.

Optionally, as shown in Figure 11, the PWM logic module includes a digital counter, a digital comparator, an AND gate, a seventh comparator, an R/S flip-flop and a single pulse flip-flop;

The data input terminal of the digital counter is connected to the valley signal; the reset input terminal of the digital counter is connected to the main power switch turn-on signal; the digital counter counts the number of valleys in the current cycle according to the valley signal. When the power switch is turned on, the digital counter is reset; the first input terminal of the digital comparator is connected to the output terminal of the digital counter, and the second input terminal of the digital comparator is connected to the valley quantity signal; the digital comparator When the first input terminal is greater than or equal to the second input terminal, a high level is output; the first input terminal of the AND gate is connected to the valley signal, and the second input terminal of the AND gate is connected to the output terminal of the digital comparator; The positive input terminal of the seventh comparator is connected to the voltage signal of the first pin; the negative input terminal of the seventh comparator is connected to the peak current signal; the set terminal of the R/S flip-flop is connected to the AND The output end of the gate; the reset end of the R/S flip-flop is connected to the output end of the seventh comparator; the output end of the R/S flip-flop outputs a driving signal and is connected to the input end of the single-pulse flip-flop. , the output end of the single-pulse trigger outputs the main power switch turn-on signal. When the third pin voltage signal is greater than the peak current signal, the seventh comparator outputs a high level, and the R/ The S flip-flop is reset and the driving signal becomes low level. When the digital comparator outputs a high level and the valley signal is also a high level, the AND gate outputs a high level and the R/S flip-flop is When set, the drive signal goes high.

Among them, the specific working process of the PWM logic module is as follows: the digital counter counts the number of valleys in the current cycle according to the valley signal. When the switch is turned on, the digital counter is reset. When the number of valleys Count_N counted by the digital counter is greater than or equal to the valley number signal Valley_N, the digital comparator outputs High level, when the CS pin voltage signal V _cs is greater than the peak current signal V _{cs_ref} , the seventh comparator outputs a high level, the R/S flip-flop is reset, and the drive signal Drive becomes low level, when the digital comparator outputs When the level is high and the valley signal Valley is also high, the AND gate outputs a high level, the R/S flip-flop is set, and the drive signal Drive becomes high level.

Further, as shown in Figure 12, Figure 12 is a schematic diagram of operating power based on an embodiment of the present application. Compared with the control method in the related art, the peak current control module reduces the peak current signal by an offset when the number of valleys decreases. , or when the number of valleys increases, the peak current signal is increased by an offset, so that the transmission power between adjacent valleys of the converter overlaps, thereby realizing the valley locking function of the flyback converter. The reason is: if the load power is at the power point corresponding to P ₁ in the steady state, the converter can operate stably at the first valley, which is point B in the figure, and can also stably operate at the second valley, which is point A in the figure. This In both cases the converter output power is equal to the load power, so valley switching does not occur.

Optionally, the voltage signal of the third pin is a voltage signal that reflects the size of the power loop current. The voltage signal is obtained by sampling the voltage at both ends of the external sampling resistor, or by directly sampling the voltage signal that reflects the size of the power loop current. .

In the specific implementation, in the circuits shown in Figure 5 and Figure 6, after the switch tube is turned on, the current flowing through the switch tube will gradually increase. This current is the power loop current, and the third pin CS samples this current. size.

Optionally, the control device may be part of a control system. Control systems that include the control method and device or are extended and modified based on the control method and device fall within the protection scope of this application.

In the embodiment of the present application, the feedback voltage is used to determine the number of valleys when the main power switch is turned on, and the peak current value is controlled to cause the transmission power between adjacent valleys of the converter to overlap, thus avoiding switching the working point of the converter operating power at the valley bottom. Discontinuity causes the converter to repeatedly switch valleys.

In the embodiment of the present application, the transmission power range of the converter in each valley state is expanded by controlling the peak current value, so that the transmission power between adjacent valleys of the converter overlaps; specifically, the number of peak current control modules is reduced at the valley When the peak current signal is reduced by an offset, or when the number of valleys increases, the peak current signal is increased by an offset, so that the transmission power between adjacent valleys of the converter overlaps, thereby realizing the flyback converter Bottom lock function.

Please participate in Figure 13. Figure 13 is a schematic flow chart of a control method for a flyback switching power supply provided by an embodiment of the present application. It is applied to the control device of a flyback switching power supply provided by an embodiment of the present application. It includes the following steps:

S1. The valley bottom detection module detects the valley bottom during the operation of the flyback converter;

S2. The valley number judgment module determines the number of valleys when the main power switch is turned on by judging the feedback voltage;

S3. The peak current control module is used to obtain the peak current signal when the main power switch is turned off according to the feedback voltage, specifically: the peak current control module reduces the peak current signal when the number of valleys decreases. An offset, or when the number of valleys increases, the peak current signal is increased by an offset, so that the transmission power between adjacent valleys of the flyback converter coincides;

S4. The PWM logic module generates a PWM pulse to drive the main power switch tube.

For the specific description of the above-mentioned steps S1-S4, reference may be made to the above corresponding descriptions and will not be described again here.

In the embodiment of the present application, a charger may also be provided, which includes the above control device, and realizes valley locking through the control device, ensuring the stability of the charger.

The above is the implementation of the embodiments of the present application. It should be pointed out that for those of ordinary skill in the technical field, several improvements and modifications can be made without departing from the principles of the embodiments of the present application. These improvements and modifications can also be made. regarded as the protection scope of this application.

Claims

A control device for a flyback switching power supply, characterized in that the control device includes: a valley bottom detection module, a valley number judgment module, a peak current control module and a PWM logic module; the valley bottom detection module, the valley number judgment module The module and the peak current control module are both connected to the PWM logic module; the valley detection module is connected to the first pin of the control device, and the PWM logic module is connected to the second pin and the third pin of the control device. pin, the valley number judgment module and the peak current control module are both connected to the fourth pin of the control device;

The valley bottom detection module is used to detect the valley bottom during the operation of the flyback converter;

The valley number judgment module is used to determine the number of valleys when the main power switch is turned on by judging the feedback voltage;

The peak current control module is used to obtain the peak current signal when the main power switch is turned off according to the feedback voltage, specifically: the peak current control module reduces the peak current signal by one bias when the number of valleys decreases. Shift, or increase the peak current signal by an offset when the number of valleys increases, so that the transmission power between adjacent valleys of the flyback converter overlaps;

The PWM logic module generates PWM pulses that drive the main power switch.
The device according to claim 1, wherein the first pin is used to connect the flyback converter, the flyback converter includes an auxiliary winding, a primary winding and a secondary winding, and the auxiliary One end of the winding is connected to the first pin and the other end is grounded; one end of the primary winding is connected to an external power supply and the other end is connected to the first end of the main power switch; one end of the secondary winding is connected to a diode One end and the other end of the diode are connected to ground; the other end of the diode is connected to the fourth pin through the feedback and isolation module;

The PWM logic module is connected to the second end of the main power switch through the second pin, and the PWM logic module is connected to the third end of the main power switch through the third pin and through the sampling resistor to ground.
The device according to claim 1, wherein the first pin is used to connect the flyback converter, and the flyback converter includes an auxiliary winding, a primary winding and a secondary winding;

One end of the auxiliary winding is connected to the first pin and the other end is grounded; one end of the primary winding is connected to an external power supply and the other end is connected to the MOS integrated system; one end of the secondary winding is connected to one end of the diode and the other end. One end is connected to ground; the other end of the diode is connected to the fourth pin through a feedback and isolation module;

The PWM logic module is connected to the MOS integrated system through the second pin and the third pin, and the MOS integrated system includes a main power switch tube.
The device according to any one of claims 1-3, characterized in that,

The valley detection module is used to sample the pin voltage of the first pin, detect the valley during the operation of the flyback converter and generate a valley signal, and transmit the valley signal to the PWM logic module ;

The valley quantity judgment module is used to determine the valley quantity signal when the main power switch is turned on according to the feedback voltage of the fourth pin, and transmit the valley quantity signal to the PWM logic module;

The peak current control module is used to control and obtain the peak current signal when the main power switch is turned off according to the feedback voltage signal of the fourth pin, specifically: when the number of valleys decreases, the peak current control module Reduce the peak current signal by an offset, or increase the peak current signal by an offset when the number of valleys increases, and transfer the peak current signal to the PWM logic module;

The PWM logic module is used to generate a signal to drive the main power switch based on the valley signal, the valley number signal when the main power switch is turned on, the peak current signal and the third pin voltage signal. PWM pulse, the PWM pulse signal is output through the second pin.
The device according to claim 4, wherein the valley number determination module includes a first comparator, a second comparator, a third comparator, a fourth comparator, a fifth comparator, a sixth comparator, A priority decoder, a first adder and a data register; the feedback voltage signal of the fourth pin is respectively connected to the first comparator, the second comparator, the third comparator, the fourth the negative input terminals of the comparator, the fifth comparator and the sixth comparator;

The positive input terminals of the first comparator, the second comparator, the third comparator, the fourth comparator, the fifth comparator and the sixth comparator are respectively connected to the first valley. reference signal, the second valley reference signal, the third valley reference signal, the fourth valley reference signal, the fifth valley reference signal and the sixth valley reference signal, wherein the voltage at the positive input terminal of any comparator is higher than the voltage at the negative input terminal When, the comparator outputs a high level; the first input terminal and the eighth input terminal of the priority decoder are grounded, and the second input terminal, the third input terminal, the fourth input terminal, The fifth input terminal, the sixth input terminal and the seventh input terminal are respectively connected to the first comparator, the second comparator, the third comparator, the fourth comparator and the fifth comparator. and the output terminal of the sixth comparator;

The output end of the priority decoder is connected to the first input end of the first adder and the second input end of the first adder is connected to a preset circuit module, and the preset circuit module is used to generate a constant 1 ; The priority decoder decodes the result of the comparator; the first adder adds 1 to the decoding result to obtain the valley number when the main power switch is turned on; the data input terminal of the data register Connect the output end of the first adder; the enable end of the data register is connected to the turn-on signal of the main power switch; the output end of the data register outputs a valley quantity signal; the data register is used to After the main power switch is turned on, the input valley number is latched to prevent the valley number from jumping due to fluctuations in the feedback voltage signal within a cycle.
The device according to claim 4, wherein the peak current control module includes a selector, a subtractor and a second adder;

The data input end of the selector is connected to the first reference signal, the second reference signal, the third reference signal, the fourth reference signal, the fifth reference signal and the sixth reference signal respectively; the data selection end of the selector is connected to all The valley number signal; the output end of the selector is connected to the negative input end of the subtractor; the selector selects the corresponding reference signal according to the valley number signal and outputs the selected reference signal to the subtractor. Negative input terminal; the feedback voltage signal is connected to the positive input terminal of the subtractor, and is connected to the first input terminal of the second adder through the first proportional link; the output terminal of the subtractor passes through the second proportional link Connect the second input terminal of the second adder; the output terminal of the second adder outputs the peak current signal.
The device according to claim 6, wherein the peak current signal generated by the peak current control module is used to overlap the transmission power between two adjacent valleys.
The device according to claim 4, wherein the PWM logic module includes a digital counter, a digital comparator, an AND gate, a seventh comparator, an R/S flip-flop and a single pulse flip-flop;

The data input terminal of the digital counter is connected to the valley signal; the reset input terminal of the digital counter is connected to the turn-on signal of the main power switch; the digital counter counts the number of valleys in the current cycle according to the valley signal. When the main power switch is turned on, the digital counter is reset; the first input terminal of the digital comparator is connected to the output terminal of the digital counter, and the second input terminal of the digital comparator is connected to the valley quantity signal; The digital comparator outputs a high level when the first input terminal is greater than or equal to the second input terminal; the first input terminal of the AND gate is connected to the valley signal, and the second input terminal of the AND gate is connected to the digital The output end of the comparator; the positive input end of the seventh comparator is connected to the voltage signal of the first pin; the negative input end of the seventh comparator is connected to the peak current signal; the R/S trigger The set end of the R/S flip-flop is connected to the output end of the AND gate; the reset end of the R/S flip-flop is connected to the output end of the seventh comparator; the output end of the R/S flip-flop outputs a driving signal and is connected to The input end of the single pulse flip-flop and the output end of the single pulse flip-flop output the turn-on signal of the main power switch. When the third pin voltage signal is greater than the peak current signal, the third pin The seventh comparator outputs high level, the R/S flip-flop is reset, and the driving signal becomes low level. When the digital comparator outputs high level and the bottom signal is also high level, the AND The gate output is high, the R/S flip-flop is set, and the drive signal becomes high.
The device according to claim 4, characterized in that the voltage signal of the third pin is a voltage signal reflecting the size of the power loop current, and the voltage signal is obtained by sampling the voltage across an external sampling resistor, or by directly sampling A voltage signal reflecting the size of the power loop current is obtained.
A control method for a flyback switching power supply, characterized in that it is applied to the control device according to any one of claims 1 to 9, and the method includes:

The valley detection module detects the valley during the operation of the flyback converter;

The valley number judgment module determines the number of valleys when the main power switch is turned on by judging the feedback voltage;

The peak current control module obtains the peak current signal when the main power switch is turned off according to the feedback voltage. Specifically, the peak current control module reduces the peak current signal by an offset when the number of valleys decreases. Or when the number of valleys increases, the peak current signal is increased by an offset, so that the transmission power between adjacent valleys of the flyback converter overlaps;

The PWM logic module generates PWM pulses that drive the main power switch.
A charger, characterized in that the charger includes the control device according to any one of claims 1-9.