WO2012068929A1

WO2012068929A1 - Switch-mode power supply control system and method thereof

Info

Publication number: WO2012068929A1
Application number: PCT/CN2011/080781
Authority: WO
Inventors: 刘永根; 熊江; 肖丽荣
Original assignee: 炬力集成电路设计有限公司
Priority date: 2010-11-26
Filing date: 2011-10-14
Publication date: 2012-05-31
Also published as: CN102480228B; CN102480228A

Abstract

Disclosed are a switch-mode power supply control system and method thereof. The switch-mode power supply control system comprises a reference signal generating circuit (10), a power switch driving circuit (50), a power switch and output circuit (60), a pulse frequency modulation (PFM) controlling circuit (30), a pulse width modulation (PWM) controlling circuit (20) and a preset duty cycle adjustment circuit (40). The preset duty cycle adjustment circuit (40) is used to compare the voltage feedback signal and the current feedback signal of the power switch and output circuit (60) with a received reference voltage signal or reference current signal, decide whether to output a mode switching signal to the PWM controlling circuit (20), and output a control logic signal to the power switch driving circuit (50) if a mode switching signal is received. The switch-mode power supply control system can quickly increase the actual output voltage of the switch-mode power supply, thus improves the load transient response and avoids affecting the normal operation of electronic devices.

Description

Switching power supply control system and method thereof

Technical field

The present invention relates to switching power supply technology, and more particularly to transient response in switching power supply technology.

Background technique

Due to the increasing popularity of portable consumer electronics, the switching power supply technology of portable electronic devices has been rapidly developed. Switching power supplies usually have pulse width modulation (Pulse Width) Modulation (referred to as "PWM") and Pulse Frequency Modulation ("PFM") work modes.

In the PWM mode of operation, the switching power converter operates at a constant switching frequency, and the PWM control circuit gradually adjusts the on-time of the power switch according to the load. Usually in PWM mode, the switching power supply has a strong load capacity. Higher efficiencies can be achieved under heavy load conditions, while at light load conditions, constant switching losses result in reduced efficiency.

In the PFM mode of operation, the operating frequency of the switching power converter varies with the size of the load. When the load is light, the operating frequency is reduced, so the switching loss is reduced, so that the switching power supply achieves higher efficiency under light load.

That is to say, switching between the PWM operating mode and the PFM operating mode according to the load current condition can improve the efficiency of the switching power supply. 1 is a block diagram of a switching power supply circuit having two operating modes of PFM and PWM and automatically switching between two modes according to load current conditions, including: a reference voltage and reference current generating circuit 10 for generating a reference voltage signal and a reference current signal The PWM control circuit 20 outputs a PWM control logic signal to the power switch drive circuit 50 according to the received mode switching signal, and obtains a voltage feedback signal and a current feedback signal from the power switch and output circuit 60, and the received reference voltage signal. Or comparing the reference current signal to determine whether to output a mode switching signal indicating switching to the PFM; the PFM control circuit 30, according to the received mode switching signal, outputting the PFM control logic signal to the power switch driving circuit 50, and from the power switch and the output The circuit 60 obtains a voltage feedback signal and a current feedback signal, and compares with the received reference voltage signal or the reference current signal to determine whether to output a mode switching signal indicating switching to PWM; the power switch driving circuit 50 receives the control logic signal and outputs the driving. Signal; power switch and output circuit 60 Receiving the driving signal, turning on and off according to the driving signal.

However, the inventors of the present invention have found that if the load current does not increase slowly, there may be a case where the light load is instantaneously changed to a heavy load, and the mutation process may be completed within a few microseconds, so that The output voltage instantaneously drops during the switching from the PFM to the PWM mode, that is, the so-called load transient response is poor, which affects the normal operation of the electronic device. The main reason for this problem is that when the load increases from a lighter mA to a heavier hundreds of mA, the switching power supply switches from PFM to PWM, but after switching to PWM mode, the power switch is controlled. The pulse width is gradually increased (that is, the on-duty of the PWM control logic signal output from the PWM control circuit to the power switch drive circuit is gradually increased), so when the power switch current does not reach the load current, the output voltage will It drops momentarily until the pulse width of the switch meets the load requirements. When the load current changes instantaneously from 1 mA to 100 mA, the output voltage and current waveform, the mode change signal, and the power switch duty cycle signal are as shown in FIG. 2. Similarly, increasing the load current instantaneously from the PWM lower duty cycle mode requires an output voltage drop problem that also occurs when switching to the PWM higher duty cycle mode.

technical problem

It is an object of the present invention to provide a switching power supply control system and method thereof that improve the transient response of a load and avoid affecting the normal operation of the electronic device.

Technical solution

To solve the above technical problem, an embodiment of the present invention provides a switching power supply control system including a reference signal generating circuit, a power switch driving circuit, a power switch and an output circuit, a pulse frequency modulation PFM control circuit, and a pulse width modulation PWM control circuit. The system further includes:

a preset duty ratio adjusting circuit, configured to output a control logic signal to the power switch driving circuit according to a mode switching signal of the PWM control circuit or the PFM control circuit, and output voltage of the power switch and the output circuit The feedback signal and the current feedback signal are compared with a reference voltage signal or a reference current signal of the reference signal generating circuit to determine whether to output a mode switching signal to the PWM control circuit or to output a control logic signal to the power switch driving circuit.

Embodiments of the present invention also provide a switching power supply control method, including the following steps:

If the preset duty ratio adjusting circuit receives the mode switching signal from the pulse width modulation PWM control circuit or the pulse frequency modulation PFM control circuit, outputting a control logic signal to the power switch driving circuit;

The preset duty ratio adjusting circuit receives a voltage feedback signal and a current feedback signal from the power switch and the output circuit, and receives the received voltage feedback signal and the current feedback signal with a reference voltage signal obtained from the reference signal generating circuit or Reference current signal for comparison;

The preset duty ratio adjustment circuit determines whether to output a mode switching signal to the PWM control circuit or to output a control logic signal to the power switch driving circuit according to the result of the comparison.

Beneficial effect

Compared with the prior art, the main differences and effects of the embodiments of the present invention are as follows:

It includes not only a reference voltage and reference current generating circuit, a PFM control circuit, a PWM control circuit, a power switch driving circuit, a power switch and an output circuit, but also a preset duty ratio adjusting circuit for applying a voltage feedback signal and a current feedback signal. Comparing with the received reference voltage signal or the reference current signal, determining whether to output the mode switching signal; and outputting the control logic signal to the power switch driving circuit according to the received mode switching signal. Since the control logic signal output by the preset duty ratio adjusting circuit can directly be a control logic signal with a higher turn-on duty ratio, the control logic of the preset duty ratio adjusting circuit output can be directly directly increased when the load current is instantaneously increased. The signal is output to the power switch driving circuit without waiting for the PWM control circuit to slowly adjust from the low on-duty to the high on-duty, so that the actual output voltage can be rapidly increased, and the output voltage can be dropped instantaneously. Improve the transient response of the load and avoid affecting the normal operation of the electronic device. Effectively solves the problem of output voltage drop caused by the instantaneous change of the switching power supply from the lighter load PFM mode to the larger load PWM mode, and the instantaneous increase of the load current from the PWM lower duty cycle mode requires conversion to the PWM higher duty The output voltage drop problem caused by the mode.

Further, the mode switching signal output by the PFM control circuit includes a mode switching signal outputted to the preset duty ratio adjusting circuit, and the preset duty ratio adjusting circuit receives the mode switching signal from the PFM control circuit to the power switch driving circuit. a control logic signal whose output conduction duty ratio is greater than a minimum on-duty ratio in the PWM operation mode; the mode switching signal output by the PWM control circuit includes a mode switching signal output to the preset duty ratio adjustment circuit, and the preset duty The ratio adjustment circuit outputs a control logic signal whose on-duty ratio is greater than the on-duty ratio in the PWM operation mode at the time of switching after receiving the mode switching signal from the PWM control circuit. Further ensuring that the control logic signal output by the preset duty ratio adjusting circuit has a higher on-duty ratio than the control logic signal outputted by the PWM control circuit when the load current is instantaneously increased, thereby ensuring the load. The improvement of transient response.

Further, the control logic signal may be a control signal for a fixed on-duty ratio, or may be a control signal that combines control signals of different on-duty ratios according to a predetermined timing or logic, so that the present embodiment can be flexibly implemented.

Further, the PFM control circuit and the PWM control circuit determine whether the preset duty ratio is required according to a comparison result between the voltage feedback signal and the current feedback signal obtained from the power switch and the output circuit and the reference voltage signal or the reference current signal. The mode switching signal output by the adjusting circuit is the same as the method for judging the change of the load current in the prior art, and the implementation is simple and can be well compatible with the prior art.

DRAWINGS

1 is a schematic structural diagram of a switching power supply control system according to prior art;

2 is a schematic diagram showing changes of respective signals when the load current changes instantaneously according to the prior art;

3 is a schematic structural diagram of a switching power supply control system according to a first embodiment of the present invention;

4 is a schematic diagram showing changes of respective signals when a load current changes instantaneously from 1 mA to 100 mA in the first embodiment of the present invention;

5 is a schematic diagram showing changes of respective signals when a load current changes instantaneously from 100 mA to 300 mA in accordance with the first embodiment of the present invention;

6 is a schematic structural diagram of a switching power supply control system according to a second embodiment of the present invention;

7 is a flow chart of a method of controlling a switching power supply according to a third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following description, numerous technical details are set forth in order to provide the reader with a better understanding of the present application. However, those skilled in the art can understand that the technical solutions claimed in the claims of the present application can be implemented without these technical details and various changes and modifications based on the following embodiments.

The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

A first embodiment of the invention relates to a switching power supply control system. 3 is a schematic structural view of the switching power supply control system. The switching power supply control system includes: a reference voltage and reference current generating circuit 10, a PWM control circuit 20, a PFM control circuit 30, a power switch driving circuit 50, a power switch and an output circuit 60, and a preset duty ratio adjusting circuit 40.

The reference voltage and reference current generating circuit 10 is configured to generate at least one reference voltage signal and at least one reference current signal.

When the PWM control circuit 20 is operating (ie, in the PWM mode of operation), the PWM control circuit 20 obtains the voltage feedback signal and the current feedback signal from the power switch and output circuit 60, and the reference voltage received from the reference voltage and reference current generating circuit 10. The signal or reference current signal is compared.

Specifically, when the actual output voltage (ie, the obtained voltage feedback signal) is higher than X% of the set voltage value (X is any number between 100 and 110, the set voltage value and the reference voltage signal satisfy a predetermined first Proportional relationship) In the present embodiment, taking X=102 as an example, setting a voltage value=1.8V as an example, the actual output voltage is higher than 1.836V, or the actual output current (ie, the obtained current feedback signal) is smaller than the set current. When the value (the set current value and the reference current signal satisfy a predetermined second proportional relationship, in the present embodiment, 50 mA is taken as an example), the PWM control circuit 20 transmits a mode switching signal to the PFM control circuit 30 and switches to the PFM operation mode. When the actual output voltage is within the range of the set voltage value and the set voltage value *N% (N is any number between 0 and 100, this embodiment takes 98 as an example), that is, when the actual output voltage is 1.8V. When between ~1.764V, the output PWM control logic signal is maintained to the power switch drive circuit 50. When the actual output voltage is less than the set voltage value *N%, it is determined that the load current is instantaneously increased, that is, when the actual output voltage is less than 1.764V, the PWM control circuit 20 sends a mode switching signal to the preset duty ratio adjusting circuit 40, and switches Adjust the working mode to the preset duty cycle. In addition, it can be understood that, in practical applications, the PWM control circuit can also determine whether the load current instantaneously increases based on the comparison of the current feedback signal obtained from the power switch and the output circuit with the set current value. It should be noted that the first proportional relationship between the set voltage value and the reference voltage signal, and the second proportional relationship between the set current value and the reference current signal may be set to an arbitrary ratio according to requirements. Common knowledge in the art is not repeated here.

When the PFM control circuit 30 is operating (ie, in the PFM mode of operation), the voltage feedback signal and the current feedback signal are obtained from the power switch and output circuit 60, and the reference voltage signal or reference current received from the reference voltage and reference current generating circuit 10 The signals are compared.

Specifically, when the actual output voltage is less than or equal to M% of the set voltage value (M is any number between 0 and 100, in this embodiment, taking 98 as an example, the set voltage value and the reference voltage signal satisfy a predetermined one. When the proportional current relationship or the actual output current is greater than the set current value (the set current value and the reference current signal satisfy a predetermined proportional relationship), it is determined that the load current is instantaneously increased, and the PFM control circuit 30 adjusts to the preset duty ratio. The circuit 40 sends a mode switching signal to switch to a preset duty ratio adjustment working mode; when the actual output voltage is greater than M% of the set output voltage value but less than or equal to U% of the set output voltage value (U is any number of 0-100, U>M, in the case of 99 as an example), the PFM control circuit 30 sends a mode switching signal to the PWM control circuit 20, and switches to the PWM control mode; when the actual output voltage When the U% is greater than the set voltage value and the actual output current is not greater than the set current value, the output PFM control logic signal is maintained to the power switch drive circuit 50.

The preset duty ratio adjusting circuit 40 is configured to enter an operating mode after receiving a mode switching signal from the PWM control circuit 20 or the PFM control circuit 30, and output a preset duty ratio adjustment to the power switch driving circuit 50 in the operating mode. The control logic signal is used to control the power switch on duty ratio, the on duty ratio of the control logic signal is greater than or equal to a preset threshold, and the voltage feedback signal and the current feedback signal are obtained from the power switch and the output circuit 60. The preset duty ratio adjusting circuit can use one of the voltage feedback signal and the current feedback signal as a basis for determining whether to switch. When the voltage feedback signal is used as a judgment basis, if the obtained voltage feedback signal is greater than the set voltage value, the PWM is switched to the PWM. Mode operation, otherwise, the output high-conduction duty control logic signal is output to the power switch driving circuit 50; when the current feedback signal is used as the judgment basis, if the obtained current feedback signal is greater than the set current value, the operation is switched to the PWM mode, otherwise The output high turn-on duty control logic signal is maintained to the power switch drive circuit 50.

Specifically, the preset duty ratio adjusting circuit 40 starts to operate after receiving the mode switching signal sent from the PWM control circuit 20, and outputs a preset duty ratio adjustment control logic signal to the power switch driving circuit 50. The control logic signal may be a fixed high on-duty duty control signal, or may be a combination of several different on-duty duty signals with a certain timing or logic, so that the preset duty ratio is adjusted. Control logic signals can be implemented flexibly. The turn-on duty ratio of the control logic signal is larger than the turn-on duty ratio in the PWM operating mode at the time of switching. Under the control of the preset duty cycle adjustment control signal, the actual output voltage of the switching power supply can be rapidly increased. When the actual output voltage reaches the set voltage value of 1.8V, the preset duty ratio adjusting circuit 40 issues a mode switching signal to the PWM control circuit 20 and switches back to the PWM control mode of operation.

The preset duty ratio adjusting circuit 40 starts to operate after receiving the mode switching signal sent from the PFM control circuit 30, and outputs a preset duty ratio adjustment control logic signal to the power switch driving circuit 50. The control logic signal may be a fixed high on-duty duty control signal, or may be a combination of several different on-duty duty signals with a certain timing or logic. The control logic signal has a large on-duty ratio that is higher than the minimum duty cycle in the PWM mode of operation. Under the control of the preset duty cycle adjustment control signal, the actual output voltage of the switching power supply can be rapidly increased. When the actual output voltage reaches the set voltage value of 1.8V, the preset duty ratio adjusting circuit 40 issues a mode switching signal to the PWM control circuit 20 and switches to the PWM control operating mode.

It is not difficult to find that in the present embodiment, since the control logic signal output by the preset duty ratio adjusting circuit can directly control the logic signal with higher duty ratio, without waiting for the PWM control circuit to be occupied from low conduction. The ratio is slowly adjusted to a high on-duty ratio, so that the actual output voltage of the switching power supply can be rapidly increased, the degree of instantaneous drop of the output voltage can be reduced, and the transient response of the load can be improved to avoid affecting the normal operation of the electronic device. Effectively solves the problem of output voltage drop caused by the instantaneous change of the switching power supply from the lighter load PFM mode to the larger load PWM mode, and the instantaneous increase of the load current from the PWM lower duty cycle mode requires conversion to the PWM higher duty The output voltage drop problem caused by the mode. When the load current changes instantaneously from 1 mA to 100 mA, the voltage waveform and mode switching signal tested by the present embodiment are as shown in FIG. 4; when the load current changes instantaneously from 100 mA to 300 mA, The voltage waveform and mode switching signal tested by this embodiment are as shown in FIG. 5.

In addition, the PFM control circuit and the PWM control circuit determine whether the load current instantaneously increases according to the comparison result between the voltage feedback signal and the current feedback signal obtained from the power switch and the output circuit, and the reference voltage signal or the reference current signal. In the technology, the manner of judging the change of the load current is the same, the implementation is simple, and the invention can be better compatible with the prior art.

A second embodiment of the present invention relates to a switching power supply control system. Fig. 6 is a schematic structural view of the switching power supply control system. The second embodiment is basically the same as the first embodiment, and the difference mainly lies in:

In the first embodiment, the preset duty ratio adjustment circuit 40 directly outputs a control logic signal to the power switch drive circuit 50. In the present embodiment, the switching power supply control system further includes a signal selection circuit (ie, the MAX circuit 70 in FIG. 6) for receiving the control logic signal from the preset duty cycle adjustment circuit and the control logic from the PWM control circuit. Signal, and select the control logic signal, in the control logic signal output by the preset duty ratio adjustment circuit and the control logic signal output by the PWM control circuit, select a larger on-duty control logic signal to be sent to the power switch drive circuit .

Specifically, the preset duty ratio adjusting circuit 40 starts to work after receiving the mode switching signal sent by the PWM control circuit 20 or the PFM control circuit 30, and presets the duty ratio adjusting circuit 40 and The PWM control circuit 20 supplies control logic signals to the MAX circuit 70. The MAX circuit 70 determines the on-duty ratio of the two control logic signals and delivers control logic having a large on-duty to the power switch drive circuit 50. signal. The preset duty ratio adjusting circuit 40 obtains the voltage feedback signal and the current feedback signal from the power switch and the output circuit 60, and compares with the reference voltage signal or the reference current signal received from the reference voltage and the reference current generating circuit 10, when the actual output is When the voltage is higher than the set voltage value or the actual output current is greater than the set current value, the preset duty ratio adjusting circuit 40 sends a mode switching signal to the PWM control circuit 20 and switches to the PWM mode; when the actual output voltage is not higher than When the set voltage value or the actual output current is not greater than the set current value, the MAX circuit 70 is held to deliver a control logic signal having a large on-duty ratio to the power switch drive circuit 50.

A third embodiment of the present invention relates to a switching power supply control method, as shown in FIG.

In step 701, the reference voltage signal and the reference current signal are generated by the reference voltage and the reference current generating circuit, and the generated reference voltage signal and the reference current signal are sent to the PFM control circuit, the PWM control circuit, and the preset duty ratio adjusting circuit. . If it is in the PFM mode of operation, then step 702 is entered, and if it is in the PWM mode of operation, then step 709 is entered.

In step 702, a control logic signal is output from the PFM control circuit to the power switch drive circuit, and a voltage feedback signal and a current feedback signal are received from the power switch and the output circuit. Specifically, after receiving the control logic signal from the PFM control circuit, the power switch drive circuit outputs a drive signal to the power switch and the output circuit. The power switch and the output circuit are turned on or off according to the received driving signal, and generate a voltage feedback signal and a current feedback signal to the PFM control circuit.

Next, in step 703, the PFM control circuit compares the voltage feedback signal and the current feedback signal with the reference voltage signal or the reference current signal, and determines whether the load current instantaneously increases according to the comparison result. If the load current instantaneously increases, the process proceeds to the step. 704, otherwise proceeds to step 707. Specifically, the PFM control circuit compares the voltage feedback signal obtained from the power switch and the output circuit with the set voltage value, and if the obtained voltage feedback signal is less than or equal to M% of the set voltage value, it is determined that the load current is instantaneously increased. Large, where 0 < M < 100. Alternatively, the obtained current feedback signal is compared with the set current value, and if the obtained current feedback signal is greater than the set current value, it is determined that the load current instantaneously increases. Wherein, the set voltage value and the reference voltage generated by the reference voltage and the reference current generating circuit satisfy a predetermined first proportional relationship, and the set current value and the reference voltage generated by the reference voltage and the reference current generating circuit satisfy a predetermined second ratio. relationship. The first proportional relationship and the second proportional relationship may be set to an arbitrary ratio as needed, and are common knowledge in the art, and are not described herein again.

In step 704, the PFM control circuit outputs a mode switching signal to the preset duty ratio adjusting circuit to switch to the operating mode of the preset duty ratio adjusting circuit.

Next, in step 705, the preset duty ratio adjustment circuit starts to work after receiving the mode switching signal output by the PFM control circuit, and outputs the on-duty ratio to the power switch driving circuit that is greater than the minimum conduction duty in the PWM operating mode. The control logic signal is compared, and the voltage feedback signal and the current feedback signal are obtained from the power switch and the output circuit. Specifically, after receiving the control logic signal from the preset duty ratio adjusting circuit, the power switch driving circuit outputs a driving signal to the power switch and the output circuit. The power switch and the output circuit are turned on or off according to the received driving signal, and generate a voltage feedback signal and a current feedback signal to the preset duty ratio adjusting circuit. The control logic signal output by the preset duty ratio adjusting circuit may be a control signal of a fixed on-duty ratio, or may be a control signal that combines control signals of different on-duty ratios according to a predetermined timing or logic.

Next, in step 706, the preset duty ratio adjusting circuit compares the voltage feedback signal and the current feedback signal with the reference voltage signal or the reference current signal, and determines whether it is necessary to switch to the PWM operating mode according to the comparison result. Specifically, the preset duty ratio adjusting circuit determines whether the obtained voltage feedback signal is greater than the set voltage value, or whether the obtained current feedback signal is greater than the set current value. If the obtained voltage feedback signal is greater than the set voltage value, or the obtained current feedback signal is greater than the set current value, it is determined that it is necessary to switch to the PWM operating mode, and the flow proceeds to step 716.

In step 716, the preset duty cycle circuit outputs a mode switching signal to the PWM control circuit to switch to the PWM operation mode, that is, proceeds to step 709. If it is determined that there is no need to switch to the PWM mode of operation, then return to step 705.

If it is determined in step 703 that the load current does not increase instantaneously, then step 707 is entered to further determine whether switching to the PWM operating mode is required.

Specifically, in step 707, the PFM control circuit determines whether the condition is satisfied according to a comparison result between the voltage feedback signal and the current feedback signal and the reference voltage signal or the reference current signal: the voltage feedback signal is greater than M% of the set voltage value, and Less than or equal to U% of the set voltage value, where 0<M<100, M<U<100. If it is determined that the condition is satisfied, the PFM control circuit determines that it is necessary to switch to the PWM operation mode, and proceeds to step 708; if it is determined that the condition is not satisfied, then returns to step 702.

In step 708, the PFM control circuit outputs a mode switching signal to the PWM control circuit, switches to the PWM mode of operation, and proceeds to step 709.

In step 709, a control logic signal is output from the PWM control circuit to the power switch drive circuit, and a voltage feedback signal and a current feedback signal are received from the power switch and the output circuit. Specifically, after receiving the control logic signal from the PWM control circuit, the power switch drive circuit outputs a drive signal to the power switch and the output circuit. The power switch and the output circuit are turned on or off according to the received driving signal, and generate a voltage feedback signal and a current feedback signal to the PWM control circuit.

Next, in step 710, the PWM control circuit compares the voltage feedback signal and the current feedback signal with a reference voltage signal or a reference current signal, and determines whether the load current instantaneously increases according to the comparison result. If the load current instantaneously increases, the process proceeds to the step. 711, otherwise proceeds to step 714. Specifically, the PWM control circuit compares the voltage feedback signal obtained from the power switch and the output circuit with the set voltage value, and if the obtained voltage feedback signal is less than N% of the set voltage value, it is determined that the load current instantaneously increases. Where 0 < N < 100.

In step 711, the PWM control circuit outputs a mode switching signal to the preset duty ratio adjusting circuit to switch to the working mode of the preset duty ratio adjusting circuit, that is, proceeds to step 705.

In step 714, the PWM control circuit determines whether the load current is small according to a comparison result between the voltage feedback signal and the current feedback signal and the reference voltage signal or the reference current signal. For example, if the voltage feedback signal is higher than X% of the set voltage value (X is any number between 100 and 110), or the current feedback signal is less than the set current value, it is determined that the load current becomes small. If it is determined that the load current becomes small, then step 715 is entered, otherwise step 709 is returned.

In step 715, the PWM control circuit outputs a mode switching signal to the PFM control circuit, switches to the PFM operation mode, and proceeds to step 702.

It is not difficult to find that the present embodiment is a method embodiment corresponding to the first embodiment, and the present embodiment can be implemented in cooperation with the first embodiment. The related technical details mentioned in the first embodiment are still effective in the present embodiment, and are not described herein again in order to reduce repetition. Accordingly, the related art details mentioned in the present embodiment can also be applied to the first embodiment.

A fourth embodiment of the present invention relates to a switching power supply control method. The fourth embodiment is basically the same as the third embodiment, and the difference mainly lies in:

In the third embodiment, the preset duty ratio adjustment circuit directly outputs the control logic signal to the power switch drive circuit. In the embodiment, the preset duty ratio adjusting circuit outputs the control logic signal to the power switch driving circuit through the signal selection circuit.

Specifically, the preset duty ratio adjustment circuit outputs a control logic signal to the signal selection circuit. The signal selection circuit receives the control logic signal output by the preset duty cycle adjustment circuit and simultaneously receives the control logic signal from the output of the PWM control circuit.

Then, the signal selection circuit selects a control logic signal with a large on-duty ratio to be sent to the power switch drive circuit in the control logic signal output by the preset duty ratio adjustment circuit and the control logic signal output by the PWM control circuit.

It is not difficult to find that the present embodiment is a method embodiment corresponding to the second embodiment, and the present embodiment can be implemented in cooperation with the second embodiment. The related technical details mentioned in the second embodiment are still effective in the present embodiment, and are not described herein again in order to reduce repetition. Accordingly, the related art details mentioned in the present embodiment can also be applied to the second embodiment.

It should be noted that the method embodiments of the present invention can be implemented in software, hardware, firmware, and the like. Regardless of whether the invention is implemented in software, hardware, or firmware, the instruction code can be stored in any type of computer-accessible memory (eg, permanent or modifiable, volatile or non-volatile, solid state Or non-solid, fixed or replaceable media, etc.). Also, the memory can be, for example, a programmable array logic (Programmable) Array Logic ("PAL" for short), Random Access Memory ("RAM") Programmable Read Only Memory ("PROM"), read-only memory (Read-Only) Memory, referred to as "ROM"), electrically erasable programmable read-only memory (Electrically Erasable Programmable) ROM, referred to as "EEPROM"), magnetic disk, optical disk, Digital Versatile Disc ("DVD") and so on.

Although the invention has been illustrated and described with reference to the preferred embodiments of the present invention, it will be understood The spirit and scope of the invention.

Embodiments of the invention

Industrial applicability

Sequence table free content

Claims

1. A switching power supply control system, comprising: a reference signal generating circuit, a power switch driving circuit, a power switch and an output circuit, a pulse frequency modulation PFM control circuit, and a pulse width modulation PWM control circuit, wherein the system further comprises:

2. The system according to claim 1, wherein said PFM control circuit is configured to use a voltage feedback signal and a current feedback signal obtained from the power switch and the output circuit, and a reference voltage obtained from the reference voltage and the reference current generating circuit. The signal or reference current signal is compared to determine whether to output a mode switching signal to the preset duty cycle adjusting circuit or the PWM control circuit, or to output a control logic signal to the power switch driving circuit.

3. The system according to claim 2, wherein the PFM control circuit outputs a mode switching signal to the preset duty ratio adjusting circuit when the following condition is satisfied;

The voltage feedback signal obtained by the PFM control circuit from the power switch and the output circuit is less than or equal to M% of the set voltage value, where 0<M<100; or

The current feedback signal obtained by the PFM control circuit from the power switch and the output circuit is greater than a set current value;

The mode switching signal output by the PFM control circuit to the PWM control circuit when the following conditions are met:

The voltage feedback signal obtained by the PFM control circuit from the power switch and the output circuit is greater than M% of the set voltage value, and is less than or equal to U% of the set voltage value, where 0<M<100 , M<U<100;

The PFM control circuit outputs a control logic signal to the power switch drive circuit when the following conditions are met:

The voltage feedback signal obtained by the PFM control circuit from the power switch and the output circuit is greater than U% of the set voltage value, and the current feedback signal obtained from the power switch and the output circuit is not greater than the set current value. ;

The reference voltage value and the reference voltage signal generated by the reference voltage and the reference current generating circuit satisfy a predetermined first proportional relationship, and the set current value and the reference voltage and the reference current generating circuit generate a reference. The current signal satisfies a predetermined second proportional relationship.

4. The system according to claim 3, wherein the preset duty ratio adjustment circuit outputs a control logic signal to the power switch drive circuit after receiving a mode switching signal from the PFM control circuit, the control logic The control signal with a fixed on-duty ratio or a control signal with different on-duty ratios is combined in a predetermined timing or logic, and the on-duty of the control signal is greater than the minimum on-duty duty in the PWM mode of operation. ratio.

5. The system according to claim 1, wherein said PWM control circuit is configured to use a voltage feedback signal and a current feedback signal obtained from the power switch and the output circuit, and a reference voltage signal or a reference current obtained from the reference voltage and the reference current generating circuit. The signals are compared to determine whether to output a mode switching signal to the preset duty cycle adjusting circuit or the PFM control circuit, or to output a control logic signal to the power switch driving circuit.

6. The system according to claim 5, wherein said PWM control circuit outputs a mode switching signal to said preset duty ratio adjusting circuit when said condition is satisfied:

The voltage feedback signal obtained by the PWM control circuit from the power switch and the output circuit is less than N% of the set voltage value, wherein 0<N<100;

The PWM control circuit outputs a mode switching signal to the PFM control circuit when the following conditions are met;

The voltage feedback signal obtained by the PWM control circuit from the power switch and the output circuit is greater than X% of the set voltage value, wherein 100<X<110; or

The current feedback signal obtained by the PWM control circuit from the power switch and the output circuit is smaller than the set current value;

The PWM control circuit outputs a control logic signal to the power switch drive circuit when the following conditions are met;

The voltage feedback signal obtained by the PWM control circuit from the power switch and the output circuit is within a range of the set voltage value and the set voltage value *N%;

7. The system according to claim 6, wherein the preset duty ratio adjustment circuit outputs a control logic signal to the power switch drive circuit after receiving a mode switching signal from the PWM control circuit, the control logic The control signal with a fixed on-duty ratio or a control signal with different on-duty ratios is combined in a predetermined timing or logic, and the on-duty of the control signal is greater than the minimum conduction in the PWM operation mode at the time of switching. Duty cycle.

8. The system according to claim 1, wherein said preset duty ratio adjustment circuit transmits a mode switching signal to said PWM control circuit when said condition is met:

The voltage feedback signal obtained by the preset duty ratio adjusting circuit from the power switch and the output circuit is greater than a set voltage value, or the current obtained by the preset duty ratio adjusting circuit from the power switch and the output circuit The feedback signal is greater than the set current value;

The preset duty ratio adjusting circuit sends a control logic signal to the power switch driving circuit when the following conditions are met:

The voltage feedback signal obtained by the preset duty ratio adjusting circuit from the power switch and the output circuit is less than or equal to a voltage setting value, or the preset duty ratio adjusting circuit is obtained from the power switch and the output circuit. The current feedback signal is less than or equal to the current set value;

9. The system according to any one of claims 1 to 8, wherein the switching power supply control system further comprises: a signal selection circuit for receiving a control logic signal from the preset duty cycle adjustment circuit and The control logic signal of the PWM control circuit selects a control logic signal having a large on-duty ratio and sends the control logic signal to the power switch drive circuit.

10. A switching power supply control method, comprising the steps of:

11. The switching power supply control method according to claim 10, wherein the preset duty ratio adjusting circuit receives the mode switching signal from the PFM control circuit, and outputs a control logic signal to the power switch driving circuit. The control signal for fixing the on-duty ratio or the control signal of the different on-duty ratio is combined in a predetermined timing or logic, and the on-duty of the control signal is greater than the minimum on-duty ratio in the PWM operation mode ;

After receiving the mode switching signal sent by the PWM control circuit, the preset duty ratio adjusting circuit outputs a control logic signal to the power switch driving circuit, which is a control signal of a fixed on-duty ratio or a different conduction duty. The control signals of the ratio are combined in a predetermined timing or logic, and the on-duty of the control signal is greater than the minimum on-duty of the PWM operating mode at the time of switching.

12. The switching power supply control method according to claim 10, wherein the PFM control circuit generates a voltage feedback signal and a current feedback signal obtained from the power switch and the output circuit, and generates the voltage from the reference voltage and the reference current. a comparison result of the reference voltage signal or the reference current signal obtained by the circuit, determining whether it is necessary to send a mode switching signal to the preset duty ratio adjusting circuit;

The PWM control circuit determines whether or not the voltage feedback signal and the current feedback signal obtained from the power switch and the output circuit are compared with a reference voltage signal or a reference current signal obtained from the reference voltage and the reference current generating circuit. A mode switching signal needs to be sent to the preset duty cycle adjustment circuit.

13. The switching power supply control method according to claim 12, wherein the step of determining, by the PFM control circuit, whether a mode switching signal needs to be sent to the preset duty ratio adjusting circuit according to the comparison result comprises the following substeps:

If the voltage feedback signal obtained by the PFM control circuit from the power switch and the output circuit is less than or equal to M% of the set voltage value, where 0<M<100; or The current feedback signal obtained by the PFM control circuit from the power switch and the output circuit is greater than a set current value; and the PFM control circuit determines to output a mode switching signal to the preset duty ratio adjusting circuit;

14. The switching power supply control method according to claim 12, further comprising the steps of:

If the voltage feedback signal obtained by the PFM control circuit from the power switch and the output circuit is greater than M% of the set voltage value, and less than or equal to U% of the set voltage value, where 0<M<100, M<U<100; then the PFM control circuit outputs a mode switching signal to the PWM control circuit;

If the voltage feedback signal obtained by the PFM control circuit from the power switch and the output circuit is greater than U% of the set voltage value and the current feedback signal obtained from the power switch and the output circuit is not greater than the set current value, then Outputting a PFM control logic signal to the power switch drive circuit;

15. The switching power supply control method according to claim 12, wherein the step of determining, by the PWM control circuit, whether a mode switching signal needs to be sent to the preset duty ratio adjusting circuit according to the comparison result comprises the following substeps:

If the voltage feedback signal obtained by the PWM control circuit from the power switch and the output circuit is less than N% of the set voltage value, wherein 0<N<100;

The reference voltage value and the reference voltage generated by the reference voltage and the reference current generating circuit satisfy a predetermined first proportional relationship.

16. The switching power supply control method according to claim 12, further comprising the steps of:

If the voltage feedback signal obtained by the PWM control circuit from the power switch and the output circuit is greater than X% of the set voltage value, wherein 100<X<110; or the PWM control circuit is from the power switch and the output The current feedback signal obtained by the circuit is less than the set current value; then the PWM control circuit outputs a mode switching signal to the PFM control circuit;

If the voltage feedback signal obtained by the PWM control circuit from the power switch and the output circuit is within a range of a set voltage value and a set voltage value *N%; then the PWM control circuit outputs to the power switch drive circuit Control logic signal;

17. The switching power supply control method according to claim 10, wherein the preset duty ratio adjusting circuit determines whether to output a mode switching signal to the PWM control circuit or to the power switch according to a result of the comparing. The step of the drive circuit outputting the control logic signal includes the following sub-steps:

If the voltage feedback signal obtained by the preset duty ratio adjusting circuit from the power switch and the output circuit is greater than a set voltage value or the current feedback signal obtained from the power switch and the output circuit is greater than a set current value, then The preset duty ratio adjusting circuit sends a mode switching signal to the PWM control circuit;

If the voltage feedback signal obtained by the preset duty ratio adjusting circuit from the power switch and the output circuit is not higher than the voltage setting value or the current feedback signal obtained from the power switch and the output circuit is not greater than the current setting value And the preset duty ratio adjusting circuit sends a control logic signal to the power switch driving circuit;

18. The switching power supply control method according to any one of claims 10 to 17, wherein the step of outputting a control logic signal to the power switch driving circuit by the preset duty ratio adjusting circuit comprises the following substeps :

The preset duty ratio adjustment circuit outputs a control logic signal to the signal selection circuit;

The signal selection circuit receives a control logic signal output by the preset duty cycle adjustment circuit, and simultaneously receives a control logic signal output from the PWM control circuit;

The signal selection circuit selects, in a control logic signal output by the preset duty ratio adjustment circuit and a control logic signal output by the PWM control circuit, a control logic signal having a large on-duty ratio to be sent to the power switch Drive circuit.