Freewheel turn-on time control circuit for DC-DC converter and DC-DC converter

Abstract

This disclosure provides an embodiment of a freewheeling diode turn-on time control circuit for a DC-DC converter, comprising: a delay signal multiplexing control circuit, a freewheeling diode turn-on time calculation circuit, an output circuit, and a reset circuit. The delay signal multiplexing control circuit generates a first indication signal based on a current-limiting indication signal output from a freewheeling diode current-limiting circuit and a reset signal from the reset circuit. The first indication signal flips to an active level when the delay signal multiplexing control circuit detects a first transition edge of the current-limiting indication signal, and resets to an inactive level when the reset signal is active. The freewheeling diode turn-on time calculation circuit calculates the freewheeling diode turn-on time of the DC-DC converter based on the input voltage and output voltage of the DC-DC converter, and generates a second indication signal based on the freewheeling diode turn-on time. The output circuit generates a freewheeling diode turn-on time control signal based on the first and second indication signals. The reset circuit generates a reset signal based on the freewheeling diode turn-on time control signal.

Description

Technical Field

[0001] Embodiments of this disclosure relate to the field of integrated circuit technology, and more specifically, to a freewheeling diode turn-on time control circuit for a DC-DC converter and a DC-DC converter. Background Technology

[0002] DC-DC converters are commonly used in various electronic devices for DC-DC voltage conversion. A freewheeling current-limiting circuit is included in the DC-DC converter to detect the current flowing through the freewheeling (i.e., the inductor current) during the freewheeling's on period. This circuit outputs a current-limiting indication signal. When the inductor current decreases to a set value, the indication signal flips to an active level. The PWM signal control circuit only allows the PWM signal to flip high after receiving the active current-limiting indication signal, thereby controlling the freewheeling to turn off and the power transistor to turn on. To provide blanking time for the freewheeling current-limiting circuit, a delay circuit is needed to postpone the output of the inductor current detection result. On the other hand, to avoid excessively small inductor current ripple and to provide sufficient logic control time for the PWM signal, the freewheeling needs to be on for at least a certain period, which is referred to as the minimum freewheeling on-time. To save chip area in DC-DC converters, the shortest freewheeling turn-on time can be set by reusing the delay circuit in the freewheeling current limiting circuit within the freewheeling turn-on time control circuit. Summary of the Invention

[0003] The embodiments described herein provide a freewheeling diode turn-on time control circuit for a DC-DC converter and a DC-DC converter.

[0004] According to a first aspect of this disclosure, a freewheeling diode turn-on time control circuit for a DC-DC converter is provided. The freewheeling diode turn-on time control circuit includes: a delay signal multiplexing control circuit, a freewheeling diode turn-on time calculation circuit, an output circuit, and a reset circuit. The delay signal multiplexing control circuit is configured to generate a first indication signal based on a current-limiting indication signal output from a freewheeling diode current-limiting circuit of the DC-DC converter and a reset signal from the reset circuit. The first indication signal flips to an active level when the delay signal multiplexing control circuit detects a first transition edge of the current-limiting indication signal. The first indication signal is reset to an inactive level when the reset signal is active. The freewheeling diode turn-on time calculation circuit is configured to calculate the freewheeling diode turn-on time of the DC-DC converter based on the input voltage and output voltage of the DC-DC converter, and generate a second indication signal based on the freewheeling diode turn-on time. The output circuit is configured to generate a freewheeling diode turn-on time control signal based on the first and second indication signals. The reset circuit is configured to generate a reset signal based on the freewheeling diode turn-on time control signal.

[0005] In some embodiments of this disclosure, the second indicator signal flips to an active level when the freewheeling tube on-time is full.

[0006] In some embodiments of this disclosure, the delay signal multiplexing control circuit includes a first inverter and a D flip-flop. The input of the first inverter is provided with a current limiting indication signal. The output of the first inverter is coupled to the clock signal terminal of the D flip-flop. The data input terminal of the D flip-flop is coupled to the inverted output terminal of the D flip-flop. A reset signal is provided to the reset terminal of the D flip-flop. A first indication signal is output from the non-inverted output terminal of the D flip-flop.

[0007] In some embodiments of this disclosure, the D flip-flop is a rising-edge triggered D flip-flop.

[0008] In some embodiments of this disclosure, the delay signal multiplexing control circuit includes a D flip-flop. The clock signal terminal of the D flip-flop is provided with a current limiting indication signal. The data input terminal of the D flip-flop is coupled to its inverted output terminal. A reset signal is provided at the reset terminal of the D flip-flop. A first indication signal is output from the output terminal of the D flip-flop.

[0009] In some embodiments of this disclosure, the D flip-flop is a falling-edge triggered D flip-flop.

[0010] In some embodiments of this disclosure, the output circuit includes an AND gate. A first input terminal of the AND gate is provided with a first indication signal. A second input terminal of the AND gate is provided with a second indication signal. A freewheeling diode on-time control signal is output from the output terminal of the AND gate.

[0011] In some embodiments of this disclosure, the reset circuit includes a second inverter. The input of the second inverter is provided with a freewheeling diode on-time control signal. A reset signal is output from the output of the second inverter.

[0012] According to a second aspect of this disclosure, a freewheeling diode turn-on time control circuit for a DC-DC converter is provided. The freewheeling diode turn-on time control circuit includes: a first inverter, a second inverter, a D flip-flop, an AND gate, and a freewheeling diode turn-on time calculation circuit. The input of the first inverter is provided with a current-limiting indication signal output from the freewheeling diode current-limiting circuit of the DC-DC converter. The output of the first inverter is coupled to the clock signal terminal of the D flip-flop. The data input terminal of the D flip-flop is coupled to the inverted output terminal of the D flip-flop. The reset terminal of the D flip-flop is coupled to the output terminal of the second inverter. The non-inverted output terminal of the D flip-flop is coupled to the first input terminal of the AND gate. The second input terminal of the AND gate is coupled to the output terminal of the freewheeling diode turn-on time calculation circuit. A freewheeling diode turn-on time control signal is output from the output terminal of the AND gate. The input terminal of the second inverter is coupled to the output terminal of the AND gate. The freewheeling diode turn-on time calculation circuit is configured to: calculate the turn-on time of the freewheeling diode of the DC-DC converter based on the input voltage and output voltage of the DC-DC converter, generate a second indication signal based on the turn-on time of the freewheeling diode, and output the second indication signal from the output terminal of the freewheeling diode turn-on time calculation circuit.

[0013] According to a third aspect of this disclosure, a DC-DC converter is provided. The DC-DC converter includes a freewheeling diode turn-on time control circuit as described in a first or second aspect of this disclosure. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure, wherein:

[0015] Figure 1 An exemplary circuit diagram of a freewheeling diode turn-on time control circuit for a DC-DC converter is shown.

[0016] Figure 2 It shows the use of Figure 1 The timing diagram of some signals of the freewheeling diode turn-on time control circuit is shown.

[0017] Figure 3 An exemplary block diagram of a freewheeling diode turn-on time control circuit for a DC-DC converter according to an embodiment of the present disclosure is shown;

[0018] Figure 4 An exemplary circuit diagram of a freewheeling diode turn-on time control circuit for a DC-DC converter according to an embodiment of the present disclosure is shown;

[0019] Figure 5 Another exemplary circuit diagram of a freewheeling diode turn-on time control circuit for a DC-DC converter according to embodiments of the present disclosure is shown; and

[0020] Figure 6 It shows the use of Figure 4 The diagram shows the timing of some signals in the freewheeling diode turn-on time control circuit.

[0021] It should be noted that the elements in the attached diagram are schematic and not drawn to scale. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0023] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the specification and in the related art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein. As used herein, statements that “connect” or “couple” two or more parts together shall mean that these parts are directly joined together or joined through one or more intermediate components. Furthermore, terms such as “first” and “second” are used only to distinguish one component (or part of a component) from another component (or another part of a component).

[0024] Figure 1 An exemplary circuit diagram of a freewheeling diode turn-on time control circuit 200 for a DC-DC converter is shown. Figure 1The diagram also shows a freewheeling diode current limiting circuit 100 in a DC-DC converter. A freewheeling diode turn-on time control circuit 200 is coupled to the freewheeling diode current limiting circuit 100. The freewheeling diode current limiting circuit 100 includes a current comparator circuit 110, a delay circuit 120, and an OR gate I0. The current comparator circuit 110 outputs signal A. Signal A flips to a low level when the current flowing through the freewheeling diode (i.e., the inductor current) decreases to a set value. The delay circuit outputs signal B. Signal B flips to a low level after the freewheeling diode turn-on time reaches the minimum freewheeling diode turn-on time; that is, the delay duration of the delay circuit is the minimum freewheeling diode turn-on time. Signals A and B are provided to the two inputs of the OR gate I0. The current limiting indicator signal LS_CL output by the OR gate I0 flips to a low level only when both signals A and B flip to a low level. In other words, the timing of the current limiting indicator signal LS_CL flipping to a low level depends on the signal that flips to a low level later than the signal in signals A and B. Figure 2 As shown, min_toff can be used to represent the shortest freewheeling tube on-time.

[0025] The freewheeling diode turn-on time control circuit 200 includes: a freewheeling diode turn-on time calculation circuit 210, an inverter I1, and an AND gate I2. The freewheeling diode turn-on time calculation circuit 210 calculates the freewheeling diode turn-on time based on the input voltage Vin and output voltage Vout of the DC-DC converter. After the freewheeling diode turn-on time is fully calculated, the second indicator signal Y output by the freewheeling diode turn-on time calculation circuit 210 flips to a high level. The current limiting indicator signal LS_CL is inverted by the inverter I1 to obtain the first indicator signal X. The first indicator signal X and the second indicator signal Y are provided to the two input terminals of the AND gate I2. When both the first indicator signal X and the second indicator signal Y are at a high level, the freewheeling diode turn-on time control signal P output by the AND gate I2 flips to a high level. If the first indicator signal X is at a low level, even if the second indicator signal Y flips to a high level, this high-level signal will be masked until the first indicator signal X flips to a high level, at which point the freewheeling diode turn-on time control signal P will flip to a high level. The freewheeling diode turn-on time control signal P is used to control the PWM signal of the DC-DC converter. The PWM signal is only allowed to turn high when the freewheeling diode turn-on time control signal P flips to a high level, thereby turning off the freewheeling diode and turning on the power transistor. Thus, by introducing the current-limiting indication signal LS_CL output from the freewheeling diode current-limiting circuit 100 into the freewheeling diode turn-on time control circuit 200, the delay circuit in the freewheeling diode current-limiting circuit 100 can be reused, thereby saving chip area in the DC-DC converter.

[0026] The inventors of this disclosure discovered Figure 1The proposed solution has the following drawbacks: the freewheeling diode turn-on time control circuit 200 reuses the delay circuit in the freewheeling diode current limiting circuit 100. Since the two are not in the same module, the current limiting indicator signal LS_CL inevitably introduces a delay due to its cross-module routing on the layout. (Reference) Figure 2 The current limiting indicator signal LS_CL rises at time T1, while the falling edge of the first indicator signal X is delayed by a time period td compared to the rising edge of the current limiting indicator signal LS_CL. When the DC-DC converter operates with a large duty cycle, the second indicator signal Y may flip to a high level within this time period td. That is, the time T2 when the second indicator signal Y flips to a high level may be earlier than the time T3 when the first indicator signal X flips to a low level. In this case, the freewheeling diode turn-on time control signal P flips to a high level prematurely at time T2 (the actual design aims for the freewheeling diode turn-on time control signal P to flip to a high level after time T4 to ensure the freewheeling diode is on for at least min_toff), causing the PWM signal to also flip to a high level prematurely, thus turning off the freewheeling diode earlier. Therefore, the actual start-up time of the freewheeling diode, toff_real (the time period between time T1 and time T2), is much lower than the minimum start-up time of the freewheeling diode, min_toff (the time period between time T1 and time T4), which is set by the multiplexing delay circuit. This causes the setting of the minimum start-up time of the freewheeling diode to fail, resulting in abnormal operation of the DC-DC converter.

[0027] Therefore, embodiments of this disclosure provide a freewheeling diode turn-on time control circuit for a DC-DC converter. Figure 3 An exemplary block diagram of a freewheeling diode turn-on time control circuit 300 for a DC-DC converter according to an embodiment of the present disclosure is shown. The freewheeling diode turn-on time control circuit 300 may include: a delay signal multiplexing control circuit 320, a freewheeling diode turn-on time calculation circuit 310, an output circuit 330, and a reset circuit 340.

[0028] The delay signal multiplexing control circuit 320 can be coupled to the output of the freewheeling diode current limiting circuit 100 of the DC-DC converter and receives the current limiting indication signal LS_CL output from the freewheeling diode current limiting circuit 100. The delay signal multiplexing control circuit 320 can also be coupled to the output circuit 330 and the reset circuit 340. The delay signal multiplexing control circuit 320 can be configured to generate a first indication signal X based on the current limiting indication signal LS_CL output from the freewheeling diode current limiting circuit 100 of the DC-DC converter and the reset signal Rst from the reset circuit 340. The first indication signal X flips to an active level when the delay signal multiplexing control circuit 320 detects a first transition edge of the current limiting indication signal LS_CL. The first indication signal X resets to an inactive level when the reset signal Rst is active. In some embodiments of this disclosure, the first transition edge is a falling edge. The delay signal multiplexing control circuit 320 detects that the first edge of the current limiting indicator signal LS_CL may occur later than the actual occurrence time of the first edge of the current limiting indicator signal LS_CL.

[0029] The freewheeling diode turn-on time calculation circuit 310 can be coupled to the delay signal multiplexing control circuit 320 and the output circuit 330. The freewheeling diode turn-on time calculation circuit 310 can be configured to calculate the freewheeling diode turn-on time of the DC-DC converter based on the input voltage and output voltage of the DC-DC converter, and generate a second indication signal Y based on the freewheeling diode turn-on time. In some embodiments of this disclosure, the freewheeling diode turn-on time calculation circuit 310 can start timing when the freewheeling diode of the DC-DC converter turns on, and when the timing reaches the calculated freewheeling diode turn-on time (i.e., the freewheeling diode turn-on time is fully counted), the second indication signal Y flips to an active level to indicate that the timing time has been reached.

[0030] Output circuit 330 can be coupled to delay signal multiplexing control circuit 320, freewheeling diode turn-on time calculation circuit 310, and reset circuit 340. Output circuit 330 can be configured to generate freewheeling diode turn-on time control signal P based on first indication signal X and second indication signal Y. In some embodiments of this disclosure, the freewheeling diode turn-on time control signal P is at an effective level when both the first indication signal X and the second indication signal Y are at an effective level. The freewheeling diode turn-on time control signal P is at an ineffective level when either the first indication signal X or the second indication signal Y is at an ineffective level. In some embodiments of this disclosure, the effective levels of the first indication signal X, the second indication signal Y, and the freewheeling diode turn-on time control signal P are all high. The ineffective levels of the first indication signal X, the second indication signal Y, and the freewheeling diode turn-on time control signal P are all low.

[0031] The reset circuit 340 can be coupled to the output circuit 330 and the delay signal multiplexing control circuit 320. The reset circuit 340 can be configured to generate a reset signal Rst based on the freewheeling diode turn-on time control signal P. In some embodiments of this disclosure, the reset signal Rst is active when the freewheeling diode turn-on time control signal P is active, and inactive when the freewheeling diode turn-on time control signal P is inactive. In some embodiments of this disclosure, the active level of the reset signal Rst is low, and the inactive level of the reset signal Rst is high.

[0032] Figure 4 An exemplary circuit diagram of a freewheeling diode turn-on time control circuit 400 for a DC-DC converter according to an embodiment of the present disclosure is shown. The delay signal multiplexing control circuit 420 may include a first inverter I1 and a D flip-flop I4. The input of the first inverter I1 is coupled to the output of the freewheeling diode current limiting circuit 100, thereby providing a current limiting indication signal LS_CL. The output of the first inverter I1 is coupled to the clock signal terminal CLK of the D flip-flop I4. The data input terminal D of the D flip-flop I4 is coupled to the inverted output terminal QN of the D flip-flop I4. The reset terminal RN of the D flip-flop I4 is coupled to the output of a reset circuit 440, thereby providing a reset signal Rst. A first indication signal X is output from the non-inverted output terminal Q of the D flip-flop I4. In some embodiments of the present disclosure, the D flip-flop I4 is a rising-edge triggered D flip-flop.

[0033] The output circuit 430 may include an AND gate I2. The first input of the AND gate I2 is coupled to the non-inverting output Q of the D flip-flop I4, thereby providing a first indication signal X. The second input of the AND gate I2 is coupled to the freewheeling diode turn-on time calculation circuit 310, thereby providing a second indication signal Y. A freewheeling diode turn-on time control signal P is output from the output of the AND gate I2. The freewheeling diode turn-on time control signal P can be used to generate a PWM signal, thereby controlling the turn-on time of the freewheeling diode.

[0034] The reset circuit 440 may include a second inverter I3. The input of the second inverter I3 is coupled to the output of the output circuit 430, thereby receiving a freewheeling diode on-time control signal P. A reset signal Rst is output from the output of the second inverter I3.

[0035] Those skilled in the art should understand that Figure 4 The internal structure of the delay signal multiplexing control circuit 420 is exemplary, and the delay signal multiplexing control circuit 420 can also be implemented by other circuits. The embodiments of this disclosure do not limit the specific implementation of the delay signal multiplexing control circuit 420. Figure 5Another exemplary circuit diagram of a freewheeling diode turn-on time control circuit 500 for a DC-DC converter according to an embodiment of the present disclosure is shown. Figure 4 Based on the example, the delay signal multiplexing control circuit 520 can include only a D flip-flop I4. The clock signal terminal CLK of the D flip-flop I4 is directly provided with a current limiting indication signal LS_CL. The data input terminal D of the D flip-flop I4 is coupled to the inverted output terminal QN of the D flip-flop I4. The reset terminal of the D flip-flop I4 is provided with a reset signal Rst. A first indication signal X is output from the output terminal of the D flip-flop I4. Figure 5 In the example, D flip-flop I4 is a falling-edge triggered D flip-flop I4.

[0036] The following is combined with Figure 6 The timing diagram is used to illustrate the operation of the freewheeling tube turn-on time control circuit 400 according to an embodiment of the present disclosure.

[0037] At time T1, the current limiting indicator signal LS_CL flips to a high level. Because the current limiting indicator signal LS_CL is transmitted across modules, there is a delay td when it reaches the input of the first inverter I1 in the freewheeling diode turn-on time control circuit 400. For example... Figure 6 As shown, the D flip-flop I4 detects the falling edge of the clock signal CLK output by the first inverter I1 at time T3. The time difference between time T3 and time T1 is td. Since... Figure 4 The D flip-flop I4 shown is rising-edge triggered. Therefore, during the td time period, the first indicator signal X output by the non-inverting output Q of the D flip-flop I4 remains low. The high level of the second indicator signal Y is masked until the clock signal CLK toggles high, preventing the freewheeling diode turn-on time control signal P from toggling high.

[0038] At time T5, the clock signal CLK flips to a high level (D flip-flop I4 detects the rising edge of the clock signal CLK), triggering D flip-flop I4. Since the data input D of D flip-flop I4 is connected to its inverted output QN, the high level assigned to the inverted output QN in the reset state is transmitted to the non-inverted output Q through the data input D. This causes the first indicator signal X output from the non-inverted output Q of D flip-flop I4 to flip to a high level. At this moment, both the first indicator signal X and the second indicator signal Y are high, causing the freewheeling diode turn-on time control signal P to also flip to a high level, thus allowing the PWM signal to flip to a high level to turn off the freewheeling diode and turn on the power transistor. The high-level freewheeling diode turn-on time control signal P, after passing through the second inverter I3, provides a low level to the reset terminal RN of D flip-flop I4, resetting D flip-flop I4. Therefore, the first indicator signal X flips to a low level, causing the freewheeling diode turn-on time control signal P to also flip to a low level, providing a high level to the reset terminal RN of D flip-flop I4, and D flip-flop I4 re-enters the operating state. The D flip-flop I4 is triggered again only when the rising edge of the clock signal CLK arrives during the next freewheeling diode turn-on period.

[0039] In this case, the actual start-up time of the freewheeling diode, toff_real (the time period between time T1 and time T5), will not be lower than the minimum start-up time of the freewheeling diode, min_toff (the time period between time T1 and time T4), which is set by the multiplexing delay circuit. Therefore, the setting of the minimum start-up time of the freewheeling diode is effective and will not turn off the freewheeling diode prematurely.

[0040] The freewheeling diode turn-on time control circuit for a DC-DC converter according to embodiments of this disclosure uses an edge-triggered method to reuse the delay circuit within the freewheeling diode current-limiting circuit. This avoids the risk of premature freewheeling shutdown caused by the level-triggered method used by the freewheeling diode turn-on time control circuit to reuse the delay circuit within the freewheeling diode current-limiting circuit when the DC-DC converter is operating with a large duty cycle. The freewheeling diode turn-on time control circuit for a DC-DC converter according to embodiments of this disclosure can maintain the stability of the DC-DC converter while saving chip area.

[0041] Unless otherwise expressly indicated by the context, the singular form of words used herein and in the appended claims includes the plural form, and vice versa. Thus, when referring to the singular, the plural form of the corresponding term is generally included. Similarly, the terms “comprising” and “including” shall be interpreted as including rather than exclusively. Likewise, the terms “including” and “or” shall be interpreted as including unless such interpretation is expressly prohibited herein. Where the term “example” is used herein, particularly when it follows a set of terms, the “example” is merely exemplary and illustrative and should not be considered exclusive or extensive.

[0042] Further aspects and scope of adaptation become apparent from the description provided herein. It should be understood that various aspects of this application may be implemented individually or in combination with one or more other aspects. It should also be understood that the descriptions and specific embodiments herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0043] Several embodiments of this disclosure have been described in detail above. However, it is obvious that those skilled in the art can make various modifications and variations to the embodiments of this disclosure without departing from the spirit and scope of this disclosure. The scope of protection of this disclosure is defined by the appended claims.

Claims

1. A freewheeling diode turn-on time control circuit for a DC-DC converter, comprising: The delay signal multiplexing control circuit, the freewheeling tube opening time calculation circuit, the output circuit, and the reset circuit, The delay signal multiplexing control circuit is configured to generate a first indication signal according to a current limiting indication signal output from a freewheeling tube current limiting circuit of the DC-DC converter and a reset signal from a reset circuit, wherein the first indication signal is flipped to a valid level when the delay signal multiplexing control circuit detects a first jump edge of the current limiting indication signal, and the first indication signal is reset to an invalid level when the reset signal is at a valid level. The freewheeling tube opening time calculation circuit is configured to calculate a freewheeling tube opening time of the DC-DC converter according to an input voltage and an output voltage of the DC-DC converter, and generate a second indication signal according to the freewheeling tube opening time. The output circuit is configured to generate a freewheeling tube opening time control signal according to the first indication signal and the second indication signal. The reset circuit is configured to generate the reset signal according to the freewheeling tube opening time control signal.

2. The freewheel tube opening time control circuit according to claim 1, wherein, The second indication signal is flipped to a valid level when the freewheeling tube opening time calculation circuit is full.

3. The freewheel tube opening time control circuit according to claim 1, wherein, The delay signal multiplexing control circuit comprises a first inverter and a D flip-flop, The input end of the first inverter is provided with the current limiting indication signal, and the output end of the first inverter is coupled to the clock signal end of the D flip-flop. The data input end of the D flip-flop is coupled to the inverted output end of the D flip-flop, the reset end of the D flip-flop is provided with the reset signal, and the first indication signal is output from the non-inverted output end of the D flip-flop.

4. The freewheel tube opening time control circuit according to claim 3, wherein, The D flip-flop is a rising edge triggered D flip-flop.

5. The freewheel tube opening time control circuit according to claim 1, wherein, The delay signal multiplexing control circuit comprises a D flip-flop, The clock signal end of the D flip-flop is provided with the current limiting indication signal, the data input end of the D flip-flop is coupled to the inverted output end of the D flip-flop, the reset end of the D flip-flop is provided with the reset signal, and the first indication signal is output from the output end of the D flip-flop.

6. The freewheel tube opening time control circuit according to claim 5, wherein The D flip-flop is a falling edge triggered D flip-flop.

7. The freewheel tube opening time control circuit according to claim 1, wherein, The output circuit comprises an AND gate, The first input end of the AND gate is provided with the first indication signal, the second input end of the AND gate is provided with the second indication signal, and the freewheeling tube opening time control signal is output from the output end of the AND gate.

8. The freewheel tube opening time control circuit according to claim 1, wherein, The reset circuit comprises a second inverter, The input end of the second inverter is provided with the freewheeling tube opening time control signal, and the reset signal is output from the output end of the second inverter.

9. A freewheel diode turn-on time control circuit for a DC-DC converter, comprising: The first inverter, the second inverter, the D flip-flop, the AND gate, and the freewheeling tube opening time calculation circuit, The input end of the first inverter is provided with a current limiting indication signal output from a freewheeling tube current limiting circuit of the DC-DC converter, and the output end of the first inverter is coupled to the clock signal end of the D flip-flop. The data input end of the D flip-flop is coupled to the inverting output end of the D flip-flop, the reset end of the D flip-flop is coupled to the output end of the second inverter, and the non-inverting output end of the D flip-flop is coupled to the first input end of the AND gate; the second input end of the AND gate is coupled to the output end of the freewheel diode on-time calculation circuit, and a freewheel diode on-time control signal is output from the output end of the AND gate; the input end of the second inverter is coupled to the output end of the AND gate; the freewheel diode on-time calculation circuit is configured to calculate a freewheel diode on-time of the DC-DC converter according to an input voltage and an output voltage of the DC-DC converter, generate a second indication signal according to the freewheel diode on-time, and output the second indication signal from the output end of the freewheel diode on-time calculation circuit. 10.A DC-DC converter comprising the freewheel diode on-time control circuit according to any one of claims 1 to 9.

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