Control device for a flyback switching power supply and related method and charger
By combining valley detection and peak current control modules, the frequency fluctuation problem of the flyback converter during valley switching is solved, the stable operation of the flyback converter is achieved, EMI performance is improved and audible noise is reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN INJOINIC TECH
- Filing Date
- 2022-08-19
- Publication Date
- 2026-06-23
Smart Images
Figure CN115776237B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic technology, specifically to a control device, method, and charger for a flyback switching power supply. Background Technology
[0002] Flyback switching power supplies, also known as flyback converters, are widely used in low-power power supplies due to their simple circuit structure and low cost. To reduce switching losses, flyback converters are generally turned on at the resonant valley of the DCM mode, and are called quasi-resonant (QR) flyback converters.
[0003] The operating frequency of a switching power supply operating in QR mode is inversely proportional to the load. Therefore, existing technologies typically use maximum frequency clamping to limit the operating frequency range of the switching power supply. However, when using this method, the operating power of the flyback converter changes abruptly at the valley switching point, resulting in discontinuous power output. This causes the flyback converter to jump between two or more valleys, leading to drastic fluctuations in the converter's operating frequency. This affects system (electromagnetic compatibility, EMI) performance and generates audible noise. Therefore, the problem of how to achieve valley locking functionality in the flyback converter urgently needs to be solved. Summary of the Invention
[0004] This application provides a control device, related method, and charger for a flyback switching power supply, which can realize the valley-locking function of the flyback converter.
[0005] In a first aspect, embodiments of this application provide a control device for a flyback switching power supply. The control device includes: a valley detection module, a valley quantity determination module, a peak current control module, and a PWM logic module. The valley detection module, the valley quantity determination module, and the peak current control module are all connected to the PWM logic module. The valley detection module is connected to a first pin of the control device, the PWM logic module is connected to a second pin and a third pin of the control device, and the valley quantity determination module and the peak current control module are both connected to a fourth pin of the control device.
[0006] The valley detection module is used to detect valleys during the operation of the flyback converter;
[0007] The valley quantity determination module is used to determine the valley quantity when the main power switch is turned on by the feedback voltage.
[0008] 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 increases 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.
[0009] The PWM logic module generates PWM pulses to drive the main power switch.
[0010] Secondly, embodiments of this application provide a control method for a flyback switching power supply, applied to a control device for a flyback switching power supply as described in the first aspect, the method comprising:
[0011] The valley detection module detects the valleys during the operation of the flyback converter;
[0012] The valley quantity determination module determines the valley quantity when the main power switch is turned on by the feedback voltage.
[0013] 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 increases 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.
[0014] The PWM logic module generates PWM pulses to drive the main power switch.
[0015] Thirdly, embodiments of this application provide a charger that includes a control device as described in the first aspect.
[0016] Implementing the embodiments of this application has the following beneficial effects:
[0017] As can be seen, the control device, method, and charger for the flyback switching power supply described in the embodiments of this application include: a valley detection module, a valley quantity judgment module, a peak current control module, and a PWM logic module; the valley detection module, valley quantity judgment module, and 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 and third pins of the control device, and the valley quantity judgment module and peak current control module are both connected to the fourth pin of the control device; the valley detection module is used to detect valleys during the operation of the flyback converter; the valley quantity judgment module is used to determine the number of valleys when the main power switch is turned on through the feedback voltage; the peak current control module is used to determine the number of valleys when the main power switch is turned on based on the feedback voltage. The peak current signal during shutdown is specifically defined as follows: 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 flyback converter overlaps. The PWM logic module generates PWM pulses to drive the main power switch. Thus, the transmission power range of the converter in each valley state can be expanded by controlling the peak current value, so that the transmission power between adjacent valleys of the converter overlaps. Specifically, 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 overlaps, thereby realizing the valley locking function of the flyback converter. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of the operating frequency of a frequency clamping control method in a related art provided in an embodiment of this application;
[0020] Figure 2 This is a graph showing the relationship between the peak current signal and the feedback voltage signal in a frequency clamping control method provided in this application embodiment.
[0021] Figure 3 This is a schematic diagram of the operating power of a frequency clamping control method in a related art provided in an embodiment of this application;
[0022] Figure 4This is a schematic diagram of a control device for a flyback switching power supply provided in an embodiment of this application;
[0023] Figure 5 This is a schematic diagram of a flyback switching power supply system provided in an embodiment of this application;
[0024] Figure 6 This is a schematic diagram of a system circuit for another flyback switching power supply provided in an embodiment of this application;
[0025] Figure 7 This is a schematic diagram of the valley quantity determination module provided in an embodiment of this application;
[0026] Figure 8 This is a graph showing the relationship between the valley quantity signal and the feedback voltage signal provided in an embodiment of this application.
[0027] Figure 9 This is a schematic diagram of the peak current control module structure provided in an embodiment of this application;
[0028] Figure 10 This is a graph showing the relationship between the peak current signal and the feedback voltage signal provided in an embodiment of this application.
[0029] Figure 11 This is a schematic diagram of the PWM logic module structure provided in an embodiment of this application;
[0030] Figure 12 This is a schematic diagram of the operating power provided in the embodiments of this application;
[0031] Figure 13 This is a flowchart illustrating the control method for a flyback switching power supply provided in an embodiment of this application. Detailed Implementation
[0032] To help those skilled in the art better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the description of the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0033] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, software, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but also includes steps or units not listed, or other steps or units inherent to such processes, methods, products, or apparatus.
[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0035] The embodiments of this application are described below with reference to the accompanying drawings. In the drawings, the intersection of intersecting wires is indicated by dots, and the absence of dots indicates that the wires are not connected.
[0036] To better understand the solutions of the embodiments of this application, the relevant terms and concepts that may be involved in the embodiments of this application will be introduced below.
[0037] In related technologies, such as Figure 1 This is a schematic diagram showing the operating frequency of a traditional frequency clamping control method. Figure 2 This is a graph showing the relationship between the peak current signal and the feedback voltage signal in a traditional frequency clamping control method. Figure 3 This diagram illustrates the operating power of a traditional frequency clamping control method. Near the valley switching point of the flyback converter, its operating power undergoes a sudden change, becoming discontinuous. This leads to frequent valley switching when the load power is at the point of discontinuous operating power. The specific reason is as follows: If, under stable load conditions, the load power happens to be at the point of power discontinuity, for example... Figure 3 At the power point corresponding to P1, the converter's operating power is greater than the load power at the first valley and less than the load power at the second valley. Therefore, the converter will repeatedly switch between the first valley and the second valley operating states to make the average output power equal to the load power.
[0038] To address the shortcomings in the relevant technology, please refer to Figure 4 , Figure 4This is a schematic diagram of a control device for a flyback switching power supply provided in an embodiment 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. The valley detection module, the valley quantity 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 VS of the control device, the PWM logic module is connected to the second pin VG and the third pin CS of the control device, and the valley quantity judgment module and the peak current control module are both connected to the fourth pin FB of the control device.
[0039] The valley detection module is used to detect valleys during the operation of the flyback converter;
[0040] The valley quantity determination module is used to determine the valley quantity when the main power switch Q1 is turned on by the feedback voltage.
[0041] 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 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 flyback converter overlaps.
[0042] The PWM logic module generates PWM pulses to drive the main power switch Q1.
[0043] Specifically, it determines the number of valleys when the main power switch is turned on by using feedback voltage, and expands the converter's transmission power range in each valley state by controlling the peak current value. This ensures that the transmission power between adjacent valleys overlaps, avoiding power discontinuity near the valley switching operating point and preventing repeated valley switching by the converter. The reduction or increase in offset should ensure that the transmission power between adjacent valleys overlaps.
[0044] Optionally, the first pin VS is used to connect to a 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 first terminal of the main power switch Q1. One end of the secondary winding is connected to one end of a diode and the other end is grounded. The other end of the diode D1 is connected to the fourth pin FB through a feedback and isolation module.
[0045] The PWM logic module is connected to the second terminal of the main power switch Q1 via the second pin VG, and the PWM logic module is connected to the third terminal of the main power switch Q1 via the third pin CS and the sampling resistor R. sense Grounding.
[0046] Among them, such as Figure 5 As shown, the first pin VS is used to connect to 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 an external power supply, and the other end is connected to the first terminal of the main power switch Q1. One end of the secondary winding is connected to one end of diode D1, and the other end is grounded. The other end of diode D1 is connected to the fourth pin FB through a feedback and isolation module. The PWM logic module is connected to the second terminal of the main power switch Q1 through the second pin VG, and the PWM logic module is connected to the third terminal of the main power switch Q1 through the third pin CS and the sampling resistor R. sense Grounding.
[0047] In practice, the current magnitude can be sampled by measuring the voltage across the sampling resistor.
[0048] One end of the primary winding can also be connected to a capacitor (C). in The diode D1 is grounded, and its output can also be connected to a capacitor (C). o Grounding.
[0049] Optionally, the first pin VS is used to connect to the flyback converter, which includes an auxiliary winding, a primary winding, and a secondary winding.
[0050] 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 a 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 a feedback and isolation module.
[0051] 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.
[0052] In specific implementation, such as Figure 6 As shown, the first pin VS is used to connect to 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 (V). inThe 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 the main power switch.
[0053] One end of the primary winding can also be connected to a capacitor (C). in The diode D1 is grounded, and its output can also be connected to a capacitor (C). o Grounding.
[0054] In practice, the MOS can be integrated into a small system, namely the MOS integrated system, which can directly output a voltage signal that reflects the magnitude of the current without the need for a sampling resistor.
[0055] In practical 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 overlaps; the peak current control module can rely solely on the feedback voltage signal V from the FB pin. FB The peak current signal V is obtained when the main power switch is turned off. cs_ref The peak current signal V when the main power switch is turned off can also be obtained by combining the valley quantity signal with the valley quantity signal. cs_ref The control modules that make the transmission power between adjacent valleys of the converter overlap by controlling the peak current signal value are all extensions and variations of the peak current control module, and are all within the protection scope of the embodiments of this application.
[0056] 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 PWM logic module;
[0057] The valley number determination module is used to determine the valley number signal when the main power switch is turned on based on the feedback voltage of the fourth pin FB, and transmit the valley number signal to the PWM logic module.
[0058] The peak current control module is used to control 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 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, and transmits the peak current signal to the PWM logic module.
[0059] The PWM logic module is used to generate PWM pulses 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 CS voltage signal of the third pin. The PWM pulse signal is output through the second pin VS.
[0060] The valley detection module samples the voltage at the VS pin, detects valleys during the flyback converter's operation, and generates a valley signal (Valley). This Valley signal is then transmitted to the PWM logic module. The valley quantity determination module determines the valley quantity based on the feedback voltage V at the FB pin. FB The valley count signal Valley_N is determined when the main power switch is turned on, and then passed to the PWM logic module. The peak current control module uses the feedback voltage signal V from the FB pin. FB The control obtains the peak current signal V when the main power switch is turned off. cs_ref Specifically, 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, thus controlling the peak current signal V. cs_ref This information is passed to the PWM logic module. The PWM logic module is used to determine the valley signal (Valley), the number of valleys when the main power switch is turned on (Valley_N), and the peak current signal (V). cs_ref and CS pin voltage signal V cs It generates PWM pulses to drive the main power switch transistor, and the PWM pulse signal is output through the VG pin.
[0061] Optional, such as Figure 7 As shown, the valley quantity 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 connected to the negative input terminals of the first comparator, the second comparator, the third comparator, the fourth comparator, the fifth comparator, and the sixth comparator, respectively.
[0062] The positive input terminals of the first, second, third, fourth, fifth, and sixth comparators are respectively connected to the first, second, third, fourth, fifth, and sixth valley reference signals. When the voltage at the positive input terminal of any comparator is higher than the voltage at its negative input terminal, the comparator outputs a high level. The first input terminal A0 and the eighth input terminal A7 of the priority decoder are grounded. The second input terminal A1, the third input terminal A2, the fourth input terminal A3, the fifth input terminal A4, the sixth input terminal A5, and the seventh input terminal A6 of the priority decoder are respectively connected to the output terminals of the first, second, third, fourth, fifth, and sixth comparators.
[0063] The output of the priority decoder is connected to the first input of the first adder, and the second input of the first adder is connected to a preset circuit module. 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 decoded result to obtain the valley number when the main power switch is turned on. The data input of the data register is connected to the output of the first adder. The enable of the data register is connected to the turn-on signal of the main power switch. The output of the data register outputs the valley number signal. The data register is used to latch the input valley number after the main power switch is turned on to avoid the valley number from jumping due to feedback voltage signal fluctuations within one cycle.
[0064] The preset circuit module can be any module that can generate a constant 1.
[0065] Among them, the negative input terminals of the first, second, third, fourth, fifth, and sixth comparators are all connected to the feedback voltage signal V. FBThe positive input of the first comparator is connected to V1, the positive input of the second comparator is connected to V2, the positive input of the third comparator is connected to V3, the positive input of the fourth comparator is connected to V4, the positive input of the fifth comparator is connected to V5, and the positive input of the sixth comparator is connected to V6. The priority decoder may include eight input pins: A0, A1, A2, A3, A4, A5, A6, and A7. A0 and A7 are grounded, and A1, A2, A3, A4, A5, and A6 are connected sequentially to the outputs of the first, second, third, fourth, fifth, and sixth comparators. The priority decoder may also include three output pins: D0, D1, and D2, all connected to the first input of the first adder. The data register includes three input pins, A0, A1, and A2, which are connected to the output of the first adder. The data register also includes three output pins, D0, D1, and D2, through which the valley quantity signal Valley_N is output.
[0066] In specific implementation, such as Figure 8 As shown, Figure 8 Based on the valley quantity signal and feedback voltage signal relationship curve of this application, the specific working process of the valley quantity judgment module is as follows: The valley reference voltage in the valley quantity judgment module is preset, and the feedback voltage signal V... FB The result of the comparator is compared 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 number when the main power switch is turned on. The data register latches the input valley number after the switch is turned on and outputs the valley number signal Valley_N.
[0067] Optional, such as Figure 9 As shown, the peak current control module includes a selector, a subtractor (-), and a second adder (+);
[0068] The data input terminals of the selector are respectively connected to the first reference signal V. ref1 Second reference signal V ref2 Third reference signal V ref3 Fourth reference signal V ref4 Fifth reference signal V ref5 and the sixth reference signal V ref6 The selector's data selection terminal is connected to the valley quantity signal (Valley_N); the selector's output terminal is connected to the negative input terminal of the subtractor; the selector selects the corresponding reference signal based on the valley quantity signal and outputs the selected reference signal to the negative input terminal of the subtractor; the feedback voltage signal (V FBThe subtractor's positive input is connected to the first input of the second adder via a first proportional element (1 / Kv); the subtractor's output is connected to the second input of the second adder via a second proportional element (1 / K1); the second adder outputs the peak current signal V. cs_ref .
[0069] The first and second scaling stages are used to achieve a certain scaling function.
[0070] Among them, such as Figure 10 The figure shows the relationship curve 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, and generates the peak current signal V based on the selected reference signal and the preset proportional coefficient. cs_ref V cs_ref It can be obtained from the following formula:
[0071] Where V ref The reference voltage selected for the selector.
[0072] The scaling factor can be preset or set by the system default.
[0073] Optionally, the peak current signal generated by the peak current control module is used to make the transmission power between two adjacent valleys overlap.
[0074] Among them, the peak current signal V generated by the peak current control module cs_ref The transmission power between two adjacent valleys should overlap to avoid discontinuous converter power switching at valleys, which would cause the converter to repeatedly switch valleys.
[0075] Optional, such as Figure 11 As shown, 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;
[0076] 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, and is reset when the main power switch is turned on; 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 count 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 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 output terminal of the AND gate; the reset terminal of the R / S flip-flop is connected to the output terminal of the seventh comparator; the output terminal of the R / S flip-flop outputs a drive signal and is connected to the input terminal of the single-pulse flip-flop; the output terminal of the single-pulse flip-flop outputs the turn-on signal of the main power switch; when the voltage signal at the third pin is greater than the peak current signal, the seventh comparator outputs a high level, the R / S flip-flop is reset, and the drive signal becomes low; when the digital comparator outputs a high level and the valley signal is also high, the AND gate outputs a high level, the R / S flip-flop is set, and the drive signal becomes high.
[0077] The specific working process of the PWM logic module is as follows: The digital counter counts the number of valleys in the current cycle based on the valley signal. The digital counter is reset when the switching transistor is turned on. When the number of valleys counted by the digital counter, Count_N, is greater than or equal to the valley number signal, Valley_N, the digital comparator outputs a high level. The voltage signal V on the CS pin is then activated. cs Greater than the peak current signal V cs_ref When the seventh comparator outputs a high level, the R / S flip-flop is reset, and the drive signal Drive becomes low. When the digital comparator outputs a high level and the valley signal is also high, the AND gate outputs a high level, the R / S flip-flop is set, and the drive signal Drive becomes high.
[0078] Furthermore, such as Figure 12 As shown, Figure 12This diagram illustrates the operating power based on an embodiment of this application. Compared to control methods in related technologies, 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. This causes the transmission power between adjacent valleys of the converter to overlap, thereby achieving the valley locking function of the flyback converter. The reason is that if, under steady-state conditions, the load power is located at the power point corresponding to P1, the converter can stably operate at the first valley (point B in the diagram) or the second valley (point A in the diagram). In both cases, the converter's output power is equal to the load power, therefore, valley switching will not occur.
[0079] Optionally, the voltage signal of the third pin is a voltage signal reflecting the magnitude of the power circuit current. This voltage signal is obtained by sampling the voltage across an external sampling resistor, or by directly sampling a voltage signal reflecting the magnitude of the power circuit current.
[0080] In the specific implementation, Figure 5 , Figure 6 In the circuit shown, after the switching transistor is turned on, the current flowing through the switching transistor will gradually increase. This current is the power loop current, and the third pin CS samples the magnitude of this current.
[0081] Optionally, the control device may be part of a control system. Any control system that includes the control method and device or is extended or modified based on the control method and device is within the protection scope of this application.
[0082] In this embodiment, the number of valleys when the main power switch is turned on is determined by the feedback voltage, and the transmission power between adjacent valleys of the converter is made to overlap by controlling the peak current value, so as to avoid the converter's working power being discontinuous when switching operating points at valleys, which would cause the converter to repeatedly switch valleys.
[0083] In this embodiment, 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 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 overlaps, thereby realizing the valley locking function of the flyback converter.
[0084] Please participate Figure 13 , Figure 13 This is a flowchart illustrating a control method for a flyback switching power supply provided in an embodiment of this application. Applied to the control device for the flyback switching power supply provided in this embodiment, the method includes the following steps:
[0085] S1. The valley detection module detects the valley during the operation of the flyback converter;
[0086] S2. The valley quantity determination module determines the valley quantity when the main power switch is turned on by the feedback voltage.
[0087] 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 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 flyback converter overlaps.
[0088] S4. The PWM logic module generates PWM pulses to drive the main power switch transistor.
[0089] The specific descriptions of steps S1-S4 above can be found in the corresponding descriptions above, and will not be repeated here.
[0090] In this embodiment of the application, a charger is also provided, which includes the above-mentioned control device. The control device realizes valley bottom locking, thereby ensuring the stability of the charger.
[0091] The above are the implementation methods of the embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the embodiments of this application, and these improvements and modifications are also considered to be within the protection scope of this application.
Claims
1. A control device for a flyback switching power supply, characterized in that, The control device includes: a valley detection circuit, a valley quantity determination circuit, a peak current control circuit, and a PWM logic circuit; the valley detection circuit, the valley quantity determination circuit, and the peak current control circuit are all connected to the PWM logic circuit; the valley detection circuit is connected to the first pin of the control device; wherein, the first pin is used to connect to the flyback converter; in, The valley detection circuit is used to detect valleys during the operation of the flyback converter; The valley quantity determination circuit is used to determine the valley quantity when the main power switch is turned on by the feedback voltage. The peak current control circuit 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 circuit 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 flyback converter overlaps. The PWM logic circuit generates PWM pulses to drive the main power switch.
2. The apparatus according to claim 1, characterized in that, The PWM logic circuit is connected to the second and third pins of the control device, and the valley quantity judgment circuit and the peak current control circuit are both connected to the fourth pin of the control device. 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 first terminal of the main power switch. One end of the secondary winding is connected to one end of a diode and the other end is grounded. The other end of the diode is connected to the fourth pin through a feedback and isolation circuit. One end of the primary winding is also grounded through a capacitor. The PWM logic circuit is connected to the second terminal of the main power switch through the second pin, and the PWM logic circuit is connected to the third terminal of the main power switch through the third pin and grounded through the sampling resistor.
3. The apparatus according to claim 1, characterized in that, The PWM logic circuit is connected to the second and third pins of the control device, and the valley quantity judgment circuit and the peak current control circuit are both connected to the fourth pin of the control device; 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 a MOS integrated system; one end of the secondary winding is connected to one end of a diode and the other end is grounded; the other end of the diode is connected to the fourth pin through a feedback and isolation circuit; wherein, one end of the primary winding is also grounded through a capacitor; The PWM logic circuit is connected to the MOS integrated system through the second pin and the third pin. The MOS integrated system includes a main power switch.
4. The apparatus according to any one of claims 2-3, characterized in that, The valley detection circuit 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 circuit. The valley quantity determination circuit 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, and transmit the valley quantity signal to the PWM logic circuit. The peak current control circuit is used to control the peak current signal when the main power switch is turned off according to the feedback voltage signal of the fourth pin. Specifically, the peak current control circuit 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, and transmits the peak current signal to the PWM logic circuit. The PWM logic circuit is used to generate PWM pulses to drive the main power switch based on the valley signal, the valley quantity signal when the main power switch is turned on, the peak current signal, and the voltage signal of the third pin. The PWM pulse signal is output through the second pin.
5. The apparatus according to claim 4, characterized in that, The valley quantity determination circuit 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 connected to the negative input terminals of the first comparator, the second comparator, the third comparator, the fourth comparator, the fifth comparator, and the sixth comparator, respectively; The positive input terminals of the first, second, third, fourth, fifth, and sixth comparators are respectively connected to the first, second, third, fourth, fifth, and sixth valley reference signals. When the voltage at the positive input terminal of any comparator is higher than the voltage at its negative input terminal, that comparator outputs a high level. The first and eighth input terminals of the priority decoder are grounded, and the second, third, fourth, fifth, sixth, and seventh input terminals of the priority decoder are respectively connected to the output terminals of the first, second, third, fourth, fifth, and sixth comparators. The output of the priority decoder is connected to the first input of the first adder, and the second input of the first adder is connected to a preset circuit, which generates a constant 1. The priority decoder decodes the result of the comparator. The first adder adds 1 to the decoded result to obtain the valley number when the main power switch is turned on. The data input of the data register is connected to the output of the first adder. The enable of the data register is connected to the turn-on signal of the main power switch. The output of the data register outputs the valley number signal. The data register is used to latch the input valley number after the main power switch is turned on to avoid fluctuations in the feedback voltage signal within one cycle that cause a jump in the valley number.
6. The apparatus according to claim 4, characterized in that, The peak current control circuit includes a selector, a subtractor, and a second adder. The data input terminals of the selector are respectively 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; the data selection terminal of the selector is connected to the valley quantity signal; 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 outputs the selected reference signal to the negative input terminal of the subtractor; the feedback voltage signal is connected to the positive input terminal of the subtractor and, through a first proportional element, to 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 a second proportional element; the output terminal of the second adder outputs the peak current signal.
7. The apparatus according to claim 6, characterized in that, The peak current signal generated by the peak current control circuit is used to make the transmission power between two adjacent valleys overlap.
8. The apparatus according to claim 4, characterized in that, The PWM logic circuit 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, and is reset when the main power switch is turned on; 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 count 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 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 output terminal of the AND gate; the reset terminal of the R / S flip-flop is connected to the output terminal of the seventh comparator; the output terminal of the R / S flip-flop outputs a drive signal and is connected to the input terminal of the single-pulse flip-flop; the output terminal of the single-pulse flip-flop outputs the turn-on signal of the main power switch; when the voltage signal at the third pin is greater than the peak current signal, the seventh comparator outputs a high level, the R / S flip-flop is reset, and the drive signal becomes low; when the digital comparator outputs a high level and the valley signal is also high, the AND gate outputs a high level, the R / S flip-flop is set, and the drive signal becomes high.
9. A control method for a flyback switching power supply, characterized in that, Applied to the control device as described in any one of claims 1-8, the method comprises: The valley detection circuit detects the valley during the operation of the flyback converter; The valley quantity determination circuit determines the valley quantity when the main power switch is turned on by the feedback voltage. The peak current control circuit obtains the peak current signal when the main power switch is turned off based on the feedback voltage. Specifically, the peak current control circuit 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 flyback converter overlaps. The PWM logic circuit generates PWM pulses to drive the main power switch.
10. A charger, characterized in that, The charger includes the control device as described in any one of claims 1-8.