A control circuit with a timing circuit, a switching power supply system and a control method thereof

Abstract

The application provides a control circuit with a timing circuit, a switching power supply system and a control method thereof. The control circuit comprises: a switching control circuit, which provides a switching control signal to control the conduction and turn-off of a switching tube; a timing circuit, which starts timing when the switching tube is switched from conduction to turn-off, and ends timing when the switching tube is switched from turn-off to conduction; and a pulse circuit, which provides N pulse signals to make the switching tube conduct correspondingly when the timing time exceeds a preset time length. The control circuit, the switching power supply system and the control method thereof are used to solve the situation of insufficient power supply of the control circuit, and further used to adaptively adjust the power supply voltage according to actual conditions, and increase the reliability of the system.

Description

Technical Field

[0001] This invention relates to the field of electronics, specifically but not limited to a control circuit with a timing circuit, a switching power supply system thereon, and a control method thereof. Background Technology

[0002] Switching power supply circuits are widely used due to their high power efficiency to provide suitable power to loads.

[0003] In applications such as small household appliances, due to their widespread use in homes, there are high requirements for green energy conservation, making standby power consumption a crucial parameter. To achieve higher power efficiency, when the load is low, the system will reduce the switching frequency or use hiccup control to intermittently switch on and off, further reducing power loss.

[0004] However, in many situations, such as in isolated switching power supply circuits, the power supply for the primary-side control circuit is often provided through auxiliary windings, etc. The supply voltage is affected by the output. When the system is in standby control state or due to load transients, the PWM signal of the switching transistor stops outputting, which may cause the supply voltage to drop, resulting in insufficient power supply to the control circuit and thus affecting the reliability of the appliance.

[0005] In view of this, there is a need to provide a structure or control method to solve at least some of the above problems. Summary of the Invention

[0006] To address one or more problems in the prior art, this invention proposes a control circuit with a timing circuit, a switching power supply system therewith, and a control method thereof.

[0007] According to one aspect of the present invention, a control circuit for controlling a switching transistor in a switching power supply circuit includes: a switching control circuit for providing a switching control signal, the switching control signal being used to control the switching transistor to turn on and off; a timing circuit coupled to the switching control circuit, the timing circuit being used to start timing when the switching control signal controls the switching transistor to switch off from a conducting state, and to stop timing when the switching transistor switches off from a conducting state; a pulse circuit coupled to the timing circuit, the pulse circuit providing N pulse signals when the timing time of the timing circuit exceeds a preset duration, where N is an integer greater than or equal to 1; and a driving circuit coupled to the switching control circuit and the pulse circuit, the switching transistor being turned on accordingly when the pulse circuit provides N pulse signals.

[0008] In one embodiment, the control circuit further includes a pulse count adjustment circuit having an input terminal and an output terminal. The input terminal of the pulse count adjustment circuit receives a status indication signal, and the output terminal of the pulse count adjustment circuit is coupled to a pulse circuit. The pulse count adjustment circuit adjusts the N value based on the status indication signal.

[0009] In one embodiment, the input of the pulse count adjustment circuit is coupled to a feedback circuit to obtain a status indication signal characterizing the load size, and the pulse count adjustment circuit adjusts the N value based on the load size.

[0010] In one embodiment, the control circuit further includes a latch circuit, the input of which is coupled to a feedback circuit to obtain a feedback signal characterizing the load size, and the output of which provides a status indication signal.

[0011] In one embodiment, the status indication signal represents a preset duration, and the N value increases as the preset duration increases.

[0012] In one embodiment, the switching power supply circuit is an isolated voltage conversion circuit, which includes a primary winding, a secondary winding and an auxiliary winding coupled to the primary winding. The primary winding is coupled to a switching transistor, the secondary winding is used to provide the output voltage, and the auxiliary winding is coupled to a control circuit to provide the power supply voltage to the control circuit.

[0013] In one embodiment, the isolated voltage converter circuit is a flyback voltage converter circuit, which further includes an isolated feedback circuit. The input terminal of the isolated feedback circuit is used to receive the output voltage, and the output terminal of the isolated feedback circuit is coupled to the feedback input terminal of the control circuit. The feedback input terminal is coupled to the input terminal of the switch control circuit.

[0014] According to another aspect of the present invention, a control circuit for controlling a switching transistor in a switching power supply circuit starts timing when the switching transistor switches from an on state to an off state, stops timing when the switching transistor switches from an off state to an on state, and when the timing duration exceeds a preset duration, the control circuit provides N pulse signals to turn on the switching transistor N times, where N is an integer greater than or equal to 1.

[0015] In one embodiment, the control circuit further includes a pulse count adjustment circuit that adjusts the N value based on a status indication signal.

[0016] In one embodiment, the pulse count adjustment circuit is coupled to a feedback circuit to acquire a load indication signal characterizing the load size, and the pulse count adjustment circuit adjusts the N value based on the load indication signal.

[0017] According to another aspect of the present invention, a switching power supply system includes a control circuit and a switching power supply circuit as described in any of the above embodiments.

[0018] According to another aspect of the present invention, a control method for a switching power supply circuit includes: monitoring the state of a switching transistor in the switching power supply circuit; starting a timer when the switching transistor switches from being on to being off, and continuing the timer when the switching transistor remains off; and intermittently turning the switching transistor on N times when the timer duration exceeds a preset duration, wherein N is an integer greater than or equal to 1.

[0019] In one embodiment, the control method further includes providing a power supply voltage using an auxiliary winding, wherein the auxiliary winding is coupled to the primary winding of the switching power supply circuit.

[0020] The control circuit with timing circuit, its switching power supply system, and control method proposed in this invention are used to solve the problem of insufficient power supply to the control circuit, and further used to adaptively adjust the power supply voltage according to the actual situation, thereby increasing the reliability of the system. Attached Figure Description

[0021] Figure 1 A schematic block diagram of a switching power supply system according to an embodiment of the present invention is shown;

[0022] Figure 2 A schematic diagram of a portion of the control circuit according to an embodiment of the present invention is shown;

[0023] Figure 3 A schematic diagram of a portion of the control circuit according to another embodiment of the present invention is shown;

[0024] Figure 4 A schematic diagram of the working waveforms according to an embodiment of the present invention is shown;

[0025] Figure 5 A schematic diagram of a switching power supply system according to an embodiment of the present invention is shown;

[0026] Figure 6 A schematic flowchart of a control method for supplying power to a control circuit in a switching power supply circuit according to an embodiment of the present invention is shown.

[0027] The same labels in different diagrams represent the same or similar parts or components. Detailed Implementation

[0028] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0029] The description in this section pertains to only a few typical embodiments, and the present invention is not limited to the scope of the embodiments described. Combinations of different embodiments, substitution of some technical features in different embodiments, and substitution of similar or identical prior art with some technical features in the embodiments are also within the scope of the description and protection of the present invention.

[0030] The terms "coupled" or "connected" in this specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection through an electrically conductive medium like a conductor, which may contain parasitic inductance or capacitance. It can also be a connection through intermediate circuits or components described in the embodiments of this specification. Indirect connections may also include connections through other active or passive devices that achieve the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, or other circuits or components. "Multiple" or "more" indicates two or more.

[0031] Figure 1 A schematic block diagram of a switching power supply system according to an embodiment of the present invention is shown. The switching power supply system includes a switching power supply circuit 101 and a control circuit 100 that controls the switching transistor Q in the switching power supply circuit 101. The switching power supply circuit 101 is used to convert the input voltage Vin into an output voltage Vout by adjusting the switching action of the switching transistor Q. The output terminal of the control circuit 100 is coupled to the control terminal of the switching transistor Q in the switching power supply circuit 101 to provide a drive signal Gate for controlling the switching transistor Q.

[0032] The control circuit 100 includes a timing circuit 11, a pulse circuit 12, a switch control circuit 13, and a drive circuit 14. The switch control circuit 13 provides a switch control signal PWM, which controls the on / off state of the switching transistor Q. In one embodiment, the switch control signal PWM provided by the switch control circuit 13 is generated based on the output voltage Vout of the switching power supply circuit 101. In another embodiment, the switch control signal PWM is further generated based on other signals. The timing circuit 11 is coupled to the switch control circuit 13; specifically, the input terminal of the timing circuit 11 is coupled to the output terminal of the switch control circuit 13 to receive the switch control signal PWM. In another embodiment, the input terminal of the timing circuit 11 receives other signals indicating whether the switching transistor Q is on or off, such as... Figure 2The ON / OFF signal is provided. The timing circuit 11 starts timing when the switch Q switches from the ON state to the ON state, continues timing while the switch Q is ON, and stops timing when the switch Q switches from the ON state to the ON state. When the timing circuit 11's timing time exceeds a preset duration T, it provides a valid overflow signal TM. In one embodiment, the overflow signal TM is a high-level pulse. In another embodiment, the overflow signal TM is a rising or falling edge of a level. The pulse circuit 12 has an input terminal and an output terminal. The input terminal of the pulse circuit 12 is coupled to the output terminal of the timing circuit 11, and the output terminal of the pulse circuit 12 provides a pulse signal PS. When the pulse circuit 12 receives a valid overflow signal TM, it provides N pulse signals PS to force the switch Q to conduct for a period of time or intermittently. Here, N is an integer greater than or equal to 1. In another embodiment, the timing circuit 11 is used to capture the moment when the switch Q switches from being on to being off and provides a signal to the pulse circuit 12. The pulse circuit 12 simultaneously detects the working state of the switch and continuously times the switch Q when it is off. When the time reaches a preset duration T, it outputs N pulse signals to turn on the switch Q for a period of time or intermittently turn it on N times.

[0033] The drive circuit 14 is coupled to the switch control circuit 13 and the pulse circuit 12. When the pulse circuit 12 provides N pulse signals, the switch transistor Q is intermittently turned on N times. When the PWM signal turns off the switch transistor Q for a longer period of time, the output voltage Vout of the switching power supply circuit 101 gradually decreases. The supply voltage VDD of the control circuit is affected by the operating state of the switch transistor Q and also decreases as the output voltage Vout decreases. In one embodiment, see... Figure 5 The supply voltage VDD is generated through the auxiliary winding of the flyback voltage converter circuit. Its value varies with the PWM signal or effective duty cycle of the primary circuit's switching transistor and also with the output voltage. In another embodiment, the supply voltage is obtained by coupling to the output of the switching power supply circuit 101. When the switching transistor Q is off for an extended period, the supply voltage VDD of the control circuit 100 will be too low. By detecting the off-time of the switching transistor Q and turning it on when the off-time exceeds a preset duration, the supply voltage VDD of the control circuit can be increased, ensuring the normal operation of the control circuit 100 and improving system reliability.

[0034] The pulse PS can include N pulse signals with a fixed pulse width. The timing time T can be set empirically; a longer timing time T allows for the output of more pulses (N) under the same conditions. A shorter timing time T reduces the number of pulses N. The number of pulses N can also be adjusted in other ways.

[0035] The drive circuit 14 can also be further coupled to other circuits to control the on and off actions of the switch Q according to signals provided by other circuits, such as protection signals.

[0036] Figure 2 A partial control circuit diagram according to an embodiment of the present invention is shown. The control circuit further includes a pulse count adjustment circuit 21, which has an input terminal and an output terminal. The input terminal of the pulse count adjustment circuit 21 receives a status indication signal IND, and the output terminal of the pulse count adjustment circuit 21 is coupled to the input terminal of a pulse circuit 22. The pulse count adjustment circuit 21 adjusts the pulse count, i.e., the value N, based on the status indication signal IND. In one embodiment, the pulse count adjustment circuit 21 adjusts the pulse count based on a signal characterizing the load. When the load value stored in the system is large, the pulse count N increases. When the load value stored in the system is small, the value N decreases.

[0037] Figure 3 A schematic diagram of a portion of the control circuit according to an embodiment of the present invention is shown. Figure 2 In contrast, the control circuit further includes a latch circuit 31 for receiving and latching the feedback signal FB. The input of the latch circuit 31 is coupled to the feedback circuit to obtain the feedback signal FB, which characterizes the load magnitude. The output of the latch circuit 31 provides a status indication signal IND. In one embodiment, the feedback signal is latched periodically, and the latching update stops when the standby signal or protection signal is active.

[0038] In another embodiment, the status indication signal IND represents a preset duration T in the timing circuit 11. If the preset duration T is long, the status indication signal IND indicates that the N value decreases.

[0039] In another embodiment, the status indication signal IND represents an input voltage overvoltage protection signal or an output current overcurrent protection signal, etc. If the input voltage overvoltage protection signal is active, the status indication signal IND indicates that the N value is decreased. If the output current overcurrent protection signal is active, the status indication signal IND indicates that the N value is increased.

[0040] In another embodiment, the status indication signal IND represents the value of the supply voltage VDD. The higher the supply voltage, the lower the N value indicated by the status indication signal IND. If the supply voltage VDD is low, the N value indicated by the status indication signal IND is increased.

[0041] In another embodiment, the status indication signal IND is used to adjust the effective value width of the pulse signal, thereby increasing the on-time of the switch Q.

[0042] continue Figure 2As described above, the drive circuit 13 may include an OR gate 23 and a drive stage circuit 24. The first input of the OR gate 23 is coupled to a pulse signal PS, and the second input is coupled to a switch control signal PWM. The output of the OR gate 23 provides a switch control signal ON / OFF. The ON / OFF signal is amplified by the drive stage circuit 24 to generate a drive signal Gate for driving the switch Q. The switch control signal PWM can be a pulse width modulation signal, or an AND signal of a pulse width modulation signal and a protection signal. The output of the OR gate 23 is coupled to the input of the drive stage circuit 24, and the output of the drive stage circuit 24 is coupled to the control terminal of the switch Q. The drive stage circuit 24 amplifies the signal to provide a suitable voltage signal for driving the switch Q.

[0043] Figure 4 A schematic diagram of the working waveforms according to an embodiment of the present invention is shown. From top to bottom, the waveforms represent the switch control signal PWM, the overflow signal TM, the pulse signal PS, and the drive signal Gate. The waveform of the drive signal Gate is the OR of the switch control signal PWM and the pulse signal PS. When the drive signal Gate is high, the switch Q is turned on. When the drive signal Gate is low, the switch Q is turned off. When the PWM signal switches from high to low, the timing circuit starts timing. If the low-level state of the PWM signal lasts for more than a preset duration T, the timing circuit overflows, and the overflow signal TM outputs a pulse signal, which causes the pulse circuit to output N valid pulse signals PS, which are used to turn on the switch Q accordingly. The preset duration T or the number of pulses N of the pulse signal PS can be adjusted based on other signals to ensure that the system's supply voltage VDD can reliably power the system without causing excessive interference to other controls.

[0044] Figure 5 A schematic diagram of a switching power supply system according to an embodiment of the present invention is shown. The switching power supply system includes a flyback voltage converter circuit and a control circuit 52. The flyback voltage converter circuit includes a transformer T1, a switching transistor Q, and an isolation feedback circuit. The transformer T1 includes a primary winding L1 coupled to the switching transistor Q, a secondary winding L2 coupled to the primary winding, and an auxiliary winding L3. The secondary winding L2 provides an output voltage Vout through a rectifier diode D. The auxiliary winding L3 provides a supply voltage VDD to the control circuit 52. In this system, when the switching transistor Q is in standby mode and does not perform switching action for a long time, the supply voltage VDD provided by the auxiliary winding L3 decreases, and the output voltage Vout also decreases simultaneously. If the off-time of the switching transistor Q is too long, exceeding a preset duration, the system generates several pulse signals to control the switching transistor Q to turn on, increasing the supply voltage VDD.

[0045] The isolation feedback circuit includes a light emitter on the secondary side and a light receiver on the primary side, used to transmit a feedback signal FB indicating the change in the output voltage Vout. Specifically, the input of the isolation feedback circuit receives the output voltage Vout, and the output of the isolation feedback circuit is coupled to the feedback input FB of the control circuit 52 to control the switching transistor Q. The feedback input FB is coupled to... Figure 1 The input terminal of the switch control circuit 13 shown. The switch control circuit 13 generates the switch control signal PWM based at least on the feedback signal FB.

[0046] Figure 6 A schematic flowchart of a control method for supplying power to a control circuit in a switching power supply circuit according to an embodiment of the present invention is shown. The control method includes step 601, monitoring the state of a switching transistor Q in the switching power supply circuit. The state of the switching transistor Q in the switching power supply circuit can be obtained by acquiring the state of a switching control signal, see [link to relevant documentation]. Figure 3 The switching control signal PWM is used. When the PWM signal is high, the switch Q is turned on; when the PWM signal is low, the switch Q is turned off. In step 602, it is monitored whether the switch Q has switched from the on state to the off state. Preferably, the monitoring of whether the switch Q has switched from the on state to the off state is determined by detecting whether the switching control signal PWM has switched from a high level to a low level. When it is detected that the switch Q has switched from the on state to the off state, step 603 is entered, and the timing circuit starts timing. In step 604, it is monitored whether the off state of the switch Q has lasted for more than a preset duration T. If the off state of the switch Q has lasted for more than the preset duration T, step 605 is entered, and N pulse signals are generated to turn on the switch Q. Each of the N pulses can have a fixed duration. The number of pulses N can be modulated by other signals, such as adjusting according to the preset duration T, feedback signals, control circuit power supply voltage levels, etc.

[0047] Those skilled in the art should know that the logic controls such as "high level" and "low level" and "AND gate" and "OR gate" in the logic control involved in the specification or drawings can be interchanged or changed, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic control.

[0048] The description and application of the present invention herein are illustrative and not intended to limit the scope of the invention to the embodiments described above. The effects or advantages described in the specification may not be apparent in actual experimental cases due to uncertainties in specific conditions or other factors, and such descriptions are not intended to limit the scope of the invention. Variations and modifications to the embodiments disclosed herein are possible, and various substitutions and equivalents of the components in the embodiments are well known to those skilled in the art. It should be understood by those skilled in the art that the invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the invention. Other variations and modifications can be made to the embodiments disclosed herein without departing from the scope and spirit of the invention.

Claims

1. A control circuit for controlling a switching transistor in a switching power supply circuit, comprising: The switching control circuit provides switching control signals, which are used to control the switching transistor to turn on and off. The timing circuit is coupled to the switch control circuit. The timing circuit is used to start timing when the switch control signal controls the switch transistor to switch from the on state to the off state, and to stop timing when the switch transistor switches from the off state to the on state. The pulse circuit is coupled to the timing circuit. When the timing time of the timing circuit exceeds the preset duration, the pulse circuit provides N pulse signals, where N is an integer greater than or equal to 1. The pulse count adjustment circuit has an input terminal and an output terminal. The input terminal of the pulse count adjustment circuit receives a status indication signal, and the output terminal of the pulse count adjustment circuit is coupled to a pulse circuit. The pulse count adjustment circuit adjusts the N value based on the status indication signal. as well as The drive circuit is coupled to the switch control circuit and the pulse circuit. When the pulse circuit provides N pulse signals, the switch transistor will turn on accordingly.

2. The control circuit as described in claim 1, wherein the input terminal of the pulse number adjustment circuit is coupled to a feedback circuit for obtaining a status indication signal characterizing the load size, and the pulse number adjustment circuit adjusts the N value based on the load size.

3. The control circuit as described in claim 2 further includes a latch circuit, wherein the input terminal of the latch circuit is coupled to a feedback circuit for obtaining a feedback signal characterizing the load size, and the output terminal of the latch circuit provides a status indication signal.

4. The control circuit as described in claim 1, wherein the status indication signal represents a preset duration, and the value of N increases with the increase of the preset duration.

5. The control circuit as described in claim 1, wherein the switching power supply circuit is an isolated voltage conversion circuit, the isolated voltage conversion circuit includes a primary winding and a secondary winding and an auxiliary winding coupled to the primary winding, wherein the primary winding is coupled to a switching transistor, the secondary winding is used to provide an output voltage, and the auxiliary winding is coupled to a control circuit to provide a power supply voltage for the control circuit.

6. The control circuit as described in claim 5, wherein the isolated voltage conversion circuit is a flyback voltage conversion circuit, and the flyback voltage conversion circuit further includes an isolated feedback circuit, wherein the input terminal of the isolated feedback circuit is used to receive the output voltage, the output terminal of the isolated feedback circuit is coupled to the feedback input terminal of the control circuit, and the feedback input terminal is coupled to the input terminal of the switch control circuit.

7. A control circuit for controlling a switching transistor in a switching power supply circuit, wherein timing begins when the switching transistor switches from an on state to an off state, and timing stops when the switching transistor switches from an off state to an on state; when the timing duration exceeds a preset duration, the control circuit provides N pulse signals to turn the switching transistor on N times, where N is an integer greater than or equal to 1; the control circuit further includes a pulse count adjustment circuit, which adjusts the value of N based on a status indication signal.

8. The control circuit as described in claim 7, wherein the pulse count adjustment circuit is coupled to the feedback circuit for acquiring a load indication signal characterizing the load size, and the pulse count adjustment circuit adjusts the N value based on the load indication signal.

9. A switching power supply system, comprising a control circuit and a switching power supply circuit as described in any one of claims 1-8.

10. A control method for supplying power to a switching power supply circuit, comprising: Monitor the status of the switching transistors in the switching power supply circuit; The timer starts when the switching transistor switches from the on state to the off state, and continues to run while the switching transistor remains in the off state. When the timing duration exceeds the preset duration, the switch is intermittently turned on N times, where N is an integer greater than or equal to 1; and The value of N is adjusted based on the status indication signal.

11. The power supply control method of claim 10, further comprising using an auxiliary winding to provide the power supply voltage, wherein the auxiliary winding is coupled to the primary winding of the switching power supply circuit.

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