CN113067482B - Error compensation circuit of switching power supply and switching power supply - Google Patents
Error compensation circuit of switching power supply and switching power supply Download PDFInfo
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- CN113067482B CN113067482B CN202110484963.3A CN202110484963A CN113067482B CN 113067482 B CN113067482 B CN 113067482B CN 202110484963 A CN202110484963 A CN 202110484963A CN 113067482 B CN113067482 B CN 113067482B
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The application discloses a switching power supply error compensation circuit and a switching power supply. The application adds a nonlinear compensation circuit on the original control loop of the switching power supply, and aims to realize the following: when the fluctuation amplitude of the output voltage of the switching power supply exceeds a preset fluctuation range (transient response stage), the control loop superimposes a compensation adjustment voltage which changes in the opposite direction along with the amplitude value of the exceeding fluctuation amplitude under the first compensation voltage generated by the original compensation circuit, and the compensation adjustment voltage together control the conduction time of the power switch so as to accelerate the response speed of the control loop and help to accelerate the stability of the output voltage; when the fluctuation amplitude does not exceed the preset fluctuation range (steady state response stage), the control loop only controls the conduction time of the power switch under the first compensation voltage generated by the original compensation circuit, and the compensation voltage ripple is smaller under the condition, so that the input current harmonic distortion can be improved, and the error compensation effect is better.
Description
Technical Field
The present invention relates to the field of switching power supplies, and in particular, to a switching power supply error compensation circuit and a switching power supply.
Background
The switching power supply comprises a rectifying circuit and a transformer; the rectification circuit is used for rectifying alternating current input by the switching power supply into direct current; the transformer is used for providing the load with the required electric energy after the rectified direct current is subjected to transformation treatment.
At present, in order to ensure the stability of the output voltage of the switching power supply, a control circuit for error compensation is generally disposed in the switching power supply, as shown in fig. 1, a conventional control circuit includes an error conversion circuit, a compensation circuit, a conduction control circuit, and a power switch Q connected to the primary winding L of the transformer, where the error compensation principle is as follows: the error conversion circuit is used for solving the error voltage between the output feedback voltage FBSH of the switching power supply and the preset voltage stabilizing reference voltage VREF and converting the error voltage between the output feedback voltage FBSH and the preset voltage stabilizing reference voltage VREF into error current to be output; the compensation circuit is used for integrating the error current converted by the error conversion circuit to obtain compensation voltage; the on control circuit is used for controlling the on time of the power switch Q according to the compensation voltage generated by the compensation circuit so as to adjust the output current of the switching power supply and further adjust the output voltage of the switching power supply, so that the output feedback voltage FBSH is stabilized to the preset stabilized reference voltage VREF.
It is known that there is a conflict between the response speed of the control loop and the compensation voltage ripple generated by the compensation circuit, that is, if the response speed of the control loop is to be increased, the compensation voltage ripple generated by the compensation circuit cannot be reduced, that is, the faster the response speed of the control loop is, the larger the compensation voltage ripple generated by the compensation circuit is, which causes harmonic distortion of the input current of the switching power supply. It can be understood that, when the output voltage of the switching power supply is in the transient response phase, the response speed of the control loop is emphasized more (if the response speed of the control loop is fast, the output voltage stability is facilitated to be accelerated); the magnitude of the compensation voltage ripple generated by the compensation circuit is emphasized when the output voltage of the switching power supply is in the steady state response stage (the compensation voltage ripple is small, which is helpful to improve the harmonic distortion of the input current of the switching power supply). However, the existing control circuit adopts the same compensation circuit to perform error compensation no matter in a transient response stage or a steady state response stage of the output voltage of the switching power supply, so that the error compensation effect is poor.
Therefore, how to provide a solution to the above technical problem is a problem that a person skilled in the art needs to solve at present.
Disclosure of Invention
The invention aims to provide a switching power supply error compensation circuit and a switching power supply, wherein when the output voltage of the switching power supply is in a transient response stage, a control loop superimposes a compensation adjustment voltage which changes in the opposite direction along with an amplitude value with exceeding fluctuation amplitude under a first compensation voltage generated by an original compensation circuit, and the compensation adjustment voltage control circuit control the conduction time of a power switch together so as to accelerate the response speed of the control loop and help to accelerate the stability of the output voltage of the switching power supply; when the output voltage of the switching power supply is in a steady state response stage, the control loop controls the on time of the power switch only under the first compensation voltage generated by the original compensation circuit, and the compensation voltage ripple is smaller under the condition, so that the harmonic distortion of the input current of the switching power supply is improved, and the error compensation effect is better.
In order to solve the above technical problems, the present invention provides a switching power supply error compensation circuit, including:
The error conversion circuit is used for solving a first error voltage between the output feedback voltage of the switching power supply and a preset first reference voltage and converting the first error voltage between the output feedback voltage and the preset first reference voltage into a first error current to be output;
the compensation circuit is used for integrating the first error current to obtain a first compensation voltage;
The nonlinear compensation circuit is used for detecting whether the fluctuation amplitude of the output feedback voltage exceeds a preset fluctuation range, and if so, generating a compensation adjustment voltage which changes in the opposite direction along with the amplitude value exceeding the fluctuation amplitude; if not, generating a compensation adjustment voltage with the amplitude smaller than a preset amplitude threshold value; superposing the compensation adjustment voltage on the first compensation voltage to obtain a second compensation voltage;
The conduction control circuit is used for controlling the conduction time of a power switch connected with a primary winding of a transformer in the switching power supply according to the second compensation voltage so as to enable the output feedback voltage to be stabilized to a preset first reference voltage; wherein the higher the second compensation voltage, the longer the on-time.
Preferably, the error conversion circuit includes:
The inverting input end is connected with the output feedback voltage, the non-inverting input end is connected with a first transconductance amplifier of a preset first reference voltage, and the first transconductance amplifier is used for obtaining a first error voltage between the output feedback voltage and the preset first reference voltage, amplifying the first error voltage and converting the first error voltage into a first error current and outputting the first error current.
Preferably, the compensation circuit includes:
The first end is respectively connected with the output end of the error conversion circuit and the nonlinear compensation circuit, and the second end is grounded.
Preferably, the nonlinear compensation circuit includes:
The nonlinear transconductance circuit is used for detecting whether the fluctuation amplitude of the output feedback voltage exceeds a preset fluctuation range, and if so, generating a compensation current which changes in the opposite direction along with the amplitude value exceeding the fluctuation amplitude; if not, generating a compensation current with the amplitude smaller than the preset amplitude threshold value;
And the voltage compensation circuit is connected with the output end of the nonlinear transconductance circuit at a first end and the output end of the compensation circuit at a second end, and is used for converting the compensation current into compensation adjustment voltage and superposing the compensation adjustment voltage on the first compensation voltage to obtain a second compensation voltage.
Preferably, the nonlinear transconductance circuit comprises a second transconductance amplifier, a third transconductance amplifier, a forward diode and a reverse diode; wherein:
the non-inverting input end of the second transconductance amplifier is connected with a preset second reference voltage, the inverting input end of the second transconductance amplifier is connected with the output feedback voltage, the output end of the second transconductance amplifier is connected with the anode of the forward diode, the non-inverting input end of the third transconductance amplifier is connected with a preset third reference voltage, the inverting input end of the third transconductance amplifier is connected with the output feedback voltage, the output end of the third transconductance amplifier is connected with the cathode of the reverse diode, the cathode of the forward diode is connected with the anode of the reverse diode, and the common end of the forward diode is used as the output end of the nonlinear transconductance circuit; wherein the preset second reference voltage is less than the preset first reference voltage is less than the preset third reference voltage;
the N-th transconductance amplifier is used for solving an N-th error voltage between the output feedback voltage and a preset N-th reference voltage, amplifying the N-th error voltage and converting the N-th error voltage into an N-th error current to be output; where n=2, 3.
Preferably, the nonlinear transconductance circuit comprises a second transconductance amplifier, a third transconductance amplifier, a forward diode and a reverse diode; wherein:
The non-inverting input end of the second transconductance amplifier is connected with a preset second reference voltage, the inverting input end of the second transconductance amplifier is connected with the output feedback voltage, the output end of the second transconductance amplifier is connected with the anode of the forward diode and the common end of the second transconductance amplifier is connected with a preset first bias current, the non-inverting input end of the third transconductance amplifier is connected with a preset third reference voltage, the inverting input end of the third transconductance amplifier is connected with the output feedback voltage, the output end of the third transconductance amplifier is connected with the cathode of the reverse diode and the common end of the third transconductance amplifier is connected with a preset second bias current, and the cathode of the forward diode is connected with the anode of the reverse diode and the common end of the forward diode is used as the output end of the nonlinear transconductance circuit; wherein the preset second reference voltage and the preset third reference voltage are equal to the preset first reference voltage; the flow direction of the preset first bias current flows out of the output end of the second transconductance amplifier; the flow direction of the preset second bias current flows into the output end of the third transconductance amplifier;
the N-th transconductance amplifier is used for solving an N-th error voltage between the output feedback voltage and a preset N-th reference voltage, amplifying the N-th error voltage and converting the N-th error voltage into an N-th error current to be output; where n=2, 3.
Preferably, the voltage compensation circuit includes:
and the first end of the compensation resistor is connected with the output end of the nonlinear transconductance circuit, and the second end of the compensation resistor is connected with the output end of the compensation circuit.
Preferably, the switching power supply error compensation circuit further includes:
and the first end of the voltage buffer is connected with the output end of the compensation circuit, and the second end of the voltage buffer is connected with the second end of the voltage compensation circuit.
Preferably, the switching power supply error compensation circuit is integrally arranged inside a control chip of the switching power supply.
In order to solve the technical problems, the invention also provides a switching power supply, which comprises any one of the switching power supply error compensation circuits.
The application provides a switching power supply error compensation circuit which comprises an error conversion circuit, a compensation circuit, a nonlinear compensation circuit and a conduction control circuit. The application adds a nonlinear compensation circuit on the original control loop of the switching power supply, and aims to realize the following: when the fluctuation amplitude of the output voltage of the switching power supply exceeds a preset fluctuation range (transient response stage), the control loop superimposes a compensation adjustment voltage which changes in the opposite direction along with the amplitude value of the exceeding fluctuation amplitude under the first compensation voltage generated by the original compensation circuit, and the compensation adjustment voltage together control the on time of the power switch so as to accelerate the response speed of the control loop and help to accelerate the stability of the output voltage of the switching power supply; when the fluctuation amplitude of the output voltage of the switching power supply does not exceed the preset fluctuation range (steady-state response stage), the compensation adjustment voltage is smaller than the preset amplitude threshold, and in fact, the compensation adjustment voltage is very small and is close to zero at the moment, that is, the control loop only controls the on time of the power switch under the first compensation voltage generated by the original compensation circuit, and under the condition, the ripple of the compensation voltage is smaller, so that the harmonic distortion of the input current of the switching power supply is improved, and the error compensation effect is better.
The invention also provides a switching power supply which has the same beneficial effects as the error compensation circuit.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the prior art and the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of error compensation of a control circuit in a switching power supply according to the prior art;
Fig. 2 is a schematic structural diagram of a switching power supply error compensation circuit according to an embodiment of the present invention;
Fig. 3 is a schematic diagram of a specific structure of a switching power supply error compensation circuit according to an embodiment of the present invention;
Fig. 4 is a specific signal waveform diagram of a switching power supply error compensation circuit according to an embodiment of the present invention.
Detailed Description
The invention provides a switching power supply error compensation circuit and a switching power supply, wherein when the output voltage of the switching power supply is in a transient response stage, a control loop superimposes a compensation adjustment voltage which changes in the opposite direction along with an amplitude value with exceeding fluctuation amplitude under a first compensation voltage generated by an original compensation circuit, and the compensation adjustment voltage control circuit control the conduction time of a power switch together so as to accelerate the response speed of the control loop and help to accelerate the stability of the output voltage of the switching power supply; when the output voltage of the switching power supply is in a steady state response stage, the control loop controls the on time of the power switch only under the first compensation voltage generated by the original compensation circuit, and the compensation voltage ripple is smaller under the condition, so that the harmonic distortion of the input current of the switching power supply is improved, and the error compensation effect is better.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a switching power supply error compensation circuit according to an embodiment of the invention.
The switching power supply error compensation circuit includes:
The error conversion circuit 100 is configured to obtain a first error voltage between an output feedback voltage of the switching power supply and a preset first reference voltage, and convert the first error voltage between the output feedback voltage and the preset first reference voltage into a first error current for output;
the compensation circuit 200 is configured to integrate the first error current to obtain a first compensation voltage;
The nonlinear compensation circuit 400 is configured to detect whether a fluctuation range of the output feedback voltage exceeds a preset fluctuation range, and if so, generate a compensation adjustment voltage that changes in a reverse direction along with a magnitude value exceeding the fluctuation range; if not, generating a compensation adjustment voltage with the amplitude smaller than a preset amplitude threshold value; superposing the compensation adjustment voltage with the first compensation voltage to obtain a second compensation voltage;
The conduction control circuit 300 is configured to control a conduction time of a power switch connected to a primary winding of a transformer in the switching power supply according to the second compensation voltage, so as to stabilize the output feedback voltage to a preset first reference voltage; wherein, the higher the second compensation voltage, the longer the on-time.
Specifically, the switching power supply error compensation circuit of the present application includes an error conversion circuit 100, a compensation circuit 200, a nonlinear compensation circuit 400 and a conduction control circuit 300, and the working principle thereof is as follows:
The error conversion circuit 100 has two input terminals, wherein one input terminal inputs an output feedback voltage FBSH (which can be obtained by sampling by the voltage sampling circuit) of the switching power supply, and the other input terminal inputs a preset first reference voltage Vref1, and the error conversion circuit 100 is configured to obtain a first error voltage between the output feedback voltage FBSH of the switching power supply and the preset first reference voltage Vref1, and convert the first error voltage therebetween into a first error current lc1 for outputting.
The input end of the compensation circuit 200 is connected to the output end of the error conversion circuit 100, and the compensation circuit 200 is configured to integrate the first error current lc1 output by the error conversion circuit 100 to obtain a first compensation voltage Vc1. The first end of the nonlinear compensation circuit 400 is connected to the input end of the conduction control circuit 300, the second end of the nonlinear compensation circuit 400 is connected to the output end of the compensation circuit 200, and the nonlinear compensation circuit 400 is used for detecting whether the fluctuation amplitude of the output feedback voltage FBSH of the switching power supply exceeds a preset fluctuation range: 1) If the fluctuation range exceeds the preset fluctuation range, indicating that the output voltage of the switching power supply is in a transient response stage, generating a compensation adjustment voltage which changes in the opposite direction along with the amplitude value exceeding the fluctuation range, namely, the larger the amplitude value of the output feedback voltage FBSH exceeds the upper limit of the preset fluctuation range (the larger the output feedback voltage FBSH), the larger the negative value of the compensation adjustment voltage, and superposing the compensation adjustment voltage with the larger negative value on the first compensation voltage Vc1 to obtain a second compensation voltage Vc2 smaller than the first compensation voltage Vc 1; the larger the amplitude value of the fluctuation amplitude of the output feedback voltage FBSH exceeds the lower limit of the preset fluctuation range (the smaller the output feedback voltage FBSH), the larger the positive value of the compensation adjustment voltage, the larger the positive value is, the first compensation voltage Vc1 is superimposed on the compensation adjustment voltage with the larger positive value, and the second compensation voltage Vc2 with the larger positive value is obtained (in summary, when the fluctuation amplitude of the output feedback voltage FBSH exceeds the preset fluctuation range, the larger the compensation adjustment voltage is, so that the fluctuation amplitude of the second compensation voltage Vc2 is increased to control the change amplitude of the output current of the switching power supply to counteract the change of the load current). 2) If the preset fluctuation range is not exceeded, the output voltage of the switching power supply is in a steady state response stage, a compensation adjustment voltage with the amplitude close to zero is generated, the compensation adjustment voltage with the amplitude close to zero is overlapped with the first compensation voltage Vc1, and a second compensation voltage Vc2 approximately equal to the first compensation voltage Vc1 is obtained.
The on control circuit 300 is configured to control an on time of a power switch Q connected to a primary winding L of a transformer in the switching power supply according to a second compensation voltage Vc2 obtained by the nonlinear compensation circuit 400, so as to stabilize an output feedback voltage FBSH of the switching power supply to a preset first reference voltage Vref1. It should be noted that, the lower the output feedback voltage FBSH of the switching power supply is, the higher the second compensation voltage Vc2 is, and the longer the on time of the power switch Q is, so that the larger the output current of the switching power supply is, the difference between the output current and the load current of the switching power supply is integrated on the load capacitor to obtain the output voltage, so as to form negative feedback closed loop control, and the output voltage of the switching power supply always tends to be stable at the preset first reference voltage Vref1.
Therefore, the nonlinear compensation circuit is additionally arranged on the original control loop of the switching power supply, and the purpose is to realize: when the fluctuation amplitude of the output voltage of the switching power supply exceeds a preset fluctuation range (transient response stage), the control loop superimposes a compensation adjustment voltage which changes in the opposite direction along with the amplitude value of the exceeding fluctuation amplitude under the first compensation voltage generated by the original compensation circuit, and the compensation adjustment voltage together control the on time of the power switch so as to accelerate the response speed of the control loop and help to accelerate the stability of the output voltage of the switching power supply; when the fluctuation amplitude of the output voltage of the switching power supply does not exceed the preset fluctuation range (steady-state response stage), the compensation adjustment voltage is smaller than the preset amplitude threshold, and in fact, the compensation adjustment voltage is very small and is close to zero at the moment, that is, the control loop only controls the on time of the power switch under the first compensation voltage generated by the original compensation circuit, and under the condition, the ripple of the compensation voltage is smaller, so that the harmonic distortion of the input current of the switching power supply is improved, and the error compensation effect is better.
Based on the above embodiments:
Referring to fig. 3, fig. 3 is a schematic diagram of a specific structure of a switching power supply error compensation circuit according to an embodiment of the invention.
As an alternative embodiment, the error conversion circuit 100 includes:
the inverting input end is connected with the output feedback voltage, the non-inverting input end is connected with a first transconductance amplifier GM1 of a preset first reference voltage, and the inverting input end is used for obtaining a first error voltage between the output feedback voltage and the preset first reference voltage, amplifying the first error voltage and converting the first error voltage into a first error current and outputting the first error current.
Specifically, the error conversion circuit 100 of the present application includes a first transconductance amplifier GM1, whose operating principle is:
The inverting input terminal of the first transconductance amplifier GM1 is used as one input terminal of the error conversion circuit 100, the non-inverting input terminal of the first transconductance amplifier GM1 is used as the other input terminal of the error conversion circuit 100, and the output terminal of the first transconductance amplifier GM1 is used as the output terminal of the error conversion circuit 100. The first transconductance amplifier GM1 is configured to obtain a first error voltage between an output feedback voltage FBSH of the switching power supply and a preset first reference voltage Vref1, amplify the first error voltage therebetween, and convert the amplified first error voltage into a first error current lc1 for outputting.
As an alternative embodiment, the compensation circuit 200 includes:
The first end is respectively connected with the output end of the error conversion circuit 100 and the nonlinear compensation circuit 400, and the second end is grounded to the compensation capacitor C1.
Specifically, the conventional compensation circuit is composed of a plurality of components such as resistors, capacitors and the like, and presents different impedance characteristics at different frequencies, so that the frequency characteristic of the compensation voltage is adjusted. However, under different application scenarios of different switching power supplies, the parameter values of the compensation circuit are different, so that components of the compensation circuit need to be adjusted according to the parameters of the switching power supplies, and therefore the components cannot be integrated inside a control chip along with the control circuit, so that the design complexity and cost of the switching power supplies are increased.
In order to reduce the cost and design complexity of the periphery of the control chip, the compensation circuit 200 is simplified to a compensation capacitor C1 to the greatest extent, the first end of the compensation capacitor C1 is used as the input end of the compensation circuit 200 and the output end of the compensation circuit 200, and the compensation capacitor C1 is used for integrating the first error current lc1 output by the first transconductance amplifier GM1 to obtain the first compensation voltage Vc1.
In addition, in order to filter the power frequency ripple wave input by the switching power supply, so as to reduce the harmonic distortion of the input current, the value of the compensation capacitor C1 can be several times of the sum of all the capacitors in the traditional compensation circuit, so that the high-frequency component higher than the power frequency ripple wave frequency in the first compensation voltage Vc1 is correspondingly several times lower than the high-frequency component in the traditional compensation voltage. Specifically, when the load current of the switching power supply is stable, the switching power supply is in a steady state response stage, the dc component of the output feedback voltage FBSH of the switching power supply is equal to the first reference voltage Vref1, and the compensation adjustment voltage is close to zero, so that the second compensation voltage Vc2 is close to the first compensation voltage Vc1, and therefore, the high-frequency component in the second compensation voltage Vc2 is correspondingly reduced. Because the high-frequency component in the second compensation voltage Vc2 is reduced, the high-frequency component in the input current of the switching power supply is correspondingly reduced, thereby reducing the harmonic distortion of the input current and improving the power factor of the system.
As an alternative embodiment, the nonlinear compensation circuit 400 includes:
The nonlinear transconductance circuit 401 is configured to detect whether a fluctuation amplitude of the output feedback voltage exceeds a preset fluctuation range, and if so, generate a compensation current that changes in an opposite direction along with an amplitude value exceeding the fluctuation amplitude; if not, generating a compensation current with the amplitude smaller than the preset amplitude threshold value;
The voltage compensation circuit 402, the first end of which is connected to the output end of the nonlinear transconductance circuit 401 and the second end of which is connected to the output end of the compensation circuit 200, is configured to convert the compensation current into a compensation adjustment voltage, and superimpose the compensation adjustment voltage on the first compensation voltage to obtain a second compensation voltage.
Specifically, the nonlinear compensation circuit 400 of the present application includes a nonlinear transconductance circuit 401 and a voltage compensation circuit 402, and its working principle is:
An output terminal of the nonlinear transconductance circuit 401 is connected to a first terminal of the voltage compensation circuit 402, and a common terminal is used as a first terminal of the nonlinear compensation circuit 400, and a second terminal of the voltage compensation circuit 402 is used as a second terminal of the nonlinear compensation circuit 400. The nonlinear transconductance circuit 401 is configured to detect whether a fluctuation amplitude of the output feedback voltage FBSH of the switching power supply exceeds a preset fluctuation range: 1) If the fluctuation range exceeds the preset fluctuation range, indicating that the output voltage of the switching power supply is in a transient response stage, generating a compensation current lc2 which changes in the opposite direction along with the amplitude value exceeding the fluctuation range, namely, the larger the amplitude value exceeding the upper limit of the preset fluctuation range of the output feedback voltage FBSH is, the larger the negative value of the compensation current lc2 is, the larger the negative value of the compensation adjustment voltage obtained by converting the compensation current lc2 is, and the larger the negative value is, the compensation adjustment voltage is superimposed on the first compensation voltage Vc1, so that a second compensation voltage Vc2 smaller than the first compensation voltage Vc1 is obtained; the larger the amplitude value of the fluctuation amplitude of the output feedback voltage FBSH exceeds the lower limit of the preset fluctuation range, the larger the positive value of the compensation current lc2, the larger the positive value of the compensation adjustment voltage obtained by converting the compensation current lc2 is, and the larger the positive value is superimposed on the first compensation voltage Vc1 to obtain the second compensation voltage Vc2 which is larger than the first compensation voltage Vc 1. 2) If the preset fluctuation range is not exceeded, the output voltage of the switching power supply is in a steady state response stage, a compensation current lc2 with the amplitude close to zero is generated, the voltage compensation circuit 402 also enables the compensation adjustment voltage obtained by converting the compensation current lc2 to be close to zero, and the compensation adjustment voltage with the amplitude close to zero is overlapped with the first compensation voltage Vc1 to obtain a second compensation voltage Vc2 approximately equal to the first compensation voltage Vc 1.
As an alternative embodiment, the nonlinear transconductance circuit 401 includes a second transconductance amplifier GM2, a third transconductance amplifier GM3, a forward diode Dp, and a reverse diode Dn; wherein:
the non-inverting input end of the second transconductance amplifier GM2 is connected with a preset second reference voltage, the inverting input end of the second transconductance amplifier GM2 is connected with an output feedback voltage, the output end of the second transconductance amplifier GM2 is connected with the anode of the forward diode Dp, the non-inverting input end of the third transconductance amplifier GM3 is connected with a preset third reference voltage, the inverting input end of the third transconductance amplifier GM3 is connected with an output feedback voltage, the output end of the third transconductance amplifier GM3 is connected with the cathode of the backward diode Dn, the cathode of the forward diode Dp is connected with the anode of the backward diode Dn, and the common end is used as the output end of the nonlinear transconductance circuit 401; wherein, the preset second reference voltage is less than the preset first reference voltage and less than the preset third reference voltage;
the N-th transconductance amplifier is used for solving an N-th error voltage between the output feedback voltage and a preset N-th reference voltage, amplifying the N-th error voltage and then converting the amplified N-th error voltage into an N-th error current to be output; where n=2, 3.
Specifically, the first embodiment of the nonlinear transconductance circuit 401 of the present application: the nonlinear transconductance circuit 401 includes a second transconductance amplifier GM2, a third transconductance amplifier GM3, a forward diode Dp, and a reverse diode Dn (without bias currents lb1 and lb 2), and operates according to the following principle:
The preset fluctuation range of the output feedback voltage FBSH of the switching power supply may be set by the second reference voltage Vref2 and the third reference voltage Vref3, as shown in fig. 4, the second reference voltage Vref2 < the first reference voltage Vref1 < the third reference voltage Vref3.
When the output feedback voltage FBSH of the switching power supply is lower than the second reference voltage Vref2, the compensation current Ic2 flows out from the output end of the second transconductance amplifier GM2, flows into the voltage compensation circuit 402 after flowing through the forward diode Dp, so that the second compensation voltage Vc2 is higher than the first compensation voltage Vc1, the lower the output feedback voltage FBSH is lower than the second reference voltage Vref2, the larger the forward value of the compensation current Ic2 is, and the higher the second compensation voltage Vc2 is than the first compensation voltage Vc1. When the output feedback voltage FBSH of the switching power supply is higher than the second reference voltage Vref2, that is, the output feedback voltage FBSH of the switching power supply is closer to the first reference voltage Vref1, the forward diode Dp prevents the compensation current Ic2 from flowing, so that the second compensation voltage Vc2 is equal to the first compensation voltage Vc1.
When the output feedback voltage FBSH of the switching power supply is higher than the third reference voltage Vref3, the compensation current Ic2 flows in from the output end of the third transconductance amplifier GM3, flows through the reverse diode Dn, flows out from the voltage compensation circuit 402, makes the second compensation voltage Vc2 lower than the first compensation voltage Vc1, and the higher the output feedback voltage FBSH is than the third reference voltage Vref3, the larger the negative value of the compensation current Ic2 is, and the lower the second compensation voltage Vc2 is than the first compensation voltage Vc1. When the output feedback voltage FBSH of the switching power supply is lower than the third reference voltage Vref3, that is, the output feedback voltage FBSH of the switching power supply is closer to the first reference voltage Vref1, the reverse diode Dn prevents the compensation current Ic2 from flowing, so that the second compensation voltage Vc2 is equal to the first compensation voltage Vc1.
As an alternative embodiment, the nonlinear transconductance circuit 401 includes a second transconductance amplifier GM2, a third transconductance amplifier GM3, a forward diode Dp, and a reverse diode Dn; wherein:
The non-inverting input end of the second transconductance amplifier GM2 is connected with a preset second reference voltage, the inverting input end of the second transconductance amplifier GM2 is connected with an output feedback voltage, the output end of the second transconductance amplifier GM2 is connected with the anode of the forward diode Dp and the common end of the second transconductance amplifier GM2 is connected with a preset first bias current, the non-inverting input end of the third transconductance amplifier GM3 is connected with a preset third reference voltage, the inverting input end of the third transconductance amplifier GM3 is connected with an output feedback voltage, the output end of the third transconductance amplifier GM3 is connected with the cathode of the reverse diode Dn and the common end of the third transconductance amplifier GM3 is connected with the anode of the reverse diode Dn and the common end of the forward diode Dp is used as the output end of the nonlinear transconductance circuit 401; the preset second reference voltage and the preset third reference voltage are equal to the preset first reference voltage; presetting the flow direction of the first bias current to flow out of the output end of the second transconductance amplifier GM 2; presetting the flow direction of the second bias current to flow into the output end of the third transconductance amplifier GM 3;
the N-th transconductance amplifier is used for solving an N-th error voltage between the output feedback voltage and a preset N-th reference voltage, amplifying the N-th error voltage and then converting the amplified N-th error voltage into an N-th error current to be output; where n=2, 3.
Specifically, the second embodiment of the nonlinear transconductance circuit 401 of the present application: the nonlinear transconductance circuit 401 includes a second transconductance amplifier GM2, a third transconductance amplifier GM3, a forward diode Dp, and a reverse diode Dn (including bias currents lb1 and lb 2), and its working principle is:
The preset fluctuation range of the output feedback voltage FBSH of the switching power supply may also be set by the first bias current Ib1 and the second bias current Ib 2. When the product of the difference between the output feedback voltage FBSH of the switching power supply and the second reference voltage Vref2 and the transconductance of the second transconductance amplifier GM2 is greater than the first bias current Ib1, the difference between the current at the output end of the second transconductance amplifier GM2 and the first bias current Ib1 flows through the forward diode Dp to form the compensation current Ic2. When the difference of the output feedback voltage FBSH minus the second reference voltage Vref2 is multiplied by the transconductance of the second transconductance amplifier GM2, the product thereof is larger than the first bias current Ib1, the larger the forward value of the compensation current Ic2 is, the higher the second compensation voltage Vc2 is than the first compensation voltage Vc1.
When the product of the difference of the third reference voltage Vref3 and the output feedback voltage FBSH is multiplied by the transconductance of the third transconductance amplifier GM3 and is larger than the second bias current Ib2, the difference of the current at the output end of the third transconductance amplifier GM3 and the second bias current Ib2 flows through the reverse diode Dn to form the compensation current Ic2, and when the product of the difference of the third reference voltage Vref3 and the output feedback voltage FBSH is multiplied by the transconductance of the third transconductance amplifier GM3 and is larger than the second bias current Ib2, the negative value of the compensation current Ic2 is larger and the second compensation voltage Vc2 is lower than the first compensation voltage Vc1.
As an alternative embodiment, the voltage compensation circuit 402 includes:
And the first end is connected with the output end of the nonlinear transconductance circuit 401, and the second end is connected with the compensation resistor R1 of the output end of the compensation circuit 200.
Specifically, the voltage compensation circuit 402 of the present application includes a compensation resistor R1, which operates according to the following principle:
the first terminal of the compensation resistor R1 is used as the first terminal of the voltage compensation circuit 402, and the second terminal of the compensation resistor R1 is used as the second terminal of the voltage compensation circuit 402. The compensation current Ic2 flows through the compensation resistor R1, and the voltage drop generated across the compensation resistor R1 constitutes a compensation adjustment voltage. It should be noted that, the compensation current Ic2 also flows into the compensation capacitor C1 to accelerate the stabilization of the first compensation voltage Vc 1.
As an alternative embodiment, the switching power supply error compensation circuit further includes:
A voltage buffer having a first terminal connected to the output terminal of the compensation circuit 200 and a second terminal connected to the second terminal of the voltage compensation circuit 402.
Further, the error compensation circuit of the switching power supply of the application further comprises a voltage buffer, and the working principle of the voltage buffer is as follows:
The first compensation voltage Vc1 is output to the compensation resistor R1 through the voltage buffer, and the structure has the advantage that the transient variation compensation current Ic2 can be prevented from flowing into the compensation capacitor C1, so that the voltage of the compensation capacitor C1 is not influenced by the transient response process.
As an alternative embodiment, the switching power supply error compensation circuit is integrally built in the control chip of the switching power supply.
Based on the above, compared with the traditional switching power supply error compensation circuit and the switching power supply error compensation circuit of the application: 1) A traditional switching power supply error compensation circuit: the compensation circuit of the switching power supply (PFC (Power Factor Correction, power factor correction) CV (constant voltage) system) is composed of a plurality of components (generally 3 RC components) such as a resistor, a capacitor and the like, the capacitor enables the input current of the switching power supply to generate phase shift, and the resistor enables the input current of the switching power supply to generate ripple, so that the Power Factor (PF) is reduced, and The Harmonic Distortion (THD) is increased. In order to improve the power factor/harmonic distortion, a compensation circuit is required to compensate for low-bandwidth over-damping; in order to improve the response speed of the control loop, the compensation circuit is required to compensate for the underdamping with high bandwidth, so that the component parameters of the compensation circuit need to be adjusted in a compromise between improving the response speed of the control loop and the power factor/harmonic distortion, and therefore the compensation circuit cannot be integrated inside the control chip along with the control circuit, so that the design complexity and the cost of the switching power supply are increased. 2) The error compensation circuit of the switching power supply comprises: the whole compensation circuit of the switching power supply is reduced to 1 RC component from a plurality of RC components, wherein the compensation resistor is controlled by P (Proportio in proportion), the compensation capacitor is controlled by I (Integration), namely PI control is split into independent P and I, the respective adjustment range of PI is increased by a plurality of times, the compensation resistor and the compensation capacitor can be built in a control chip, and the control chip does not need compensation pins any more. The control principle of the compensation resistor and the compensation capacitor is as follows: the detection of the output voltage range is increased, and in the preset fluctuation range, the P control (the compensation resistor is not active) is closed, so that the I control (the compensation capacitor) independently adjusts the power factor/harmonic distortion; and (3) starting the P control (the compensation resistor acts) outside a preset fluctuation range, so that the P control independently adjusts the response speed of the system.
In summary, the switching power supply error compensation circuit provided by the application distinguishes the transient response and the steady state response of the system according to the output feedback voltage, and the harmonic distortion is independently regulated by utilizing the low-frequency pole of the compensation circuit in the steady state response stage; in the transient response stage, nonlinear error amplification and compensation are utilized to generate nonlinear compensation voltage to independently adjust the response speed of the system, and the error compensation effect is good.
The application also provides a switching power supply, which comprises any one of the switching power supply error compensation circuits.
The description of the switching power supply provided by the present application refers to the embodiment of the error compensation circuit, and the disclosure is not repeated here.
It should also be noted that in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A switching power supply error compensation circuit, comprising:
The error conversion circuit is used for solving a first error voltage between the output feedback voltage of the switching power supply and a preset first reference voltage and converting the first error voltage between the output feedback voltage and the preset first reference voltage into a first error current to be output;
the compensation circuit is used for integrating the first error current to obtain a first compensation voltage;
The nonlinear compensation circuit is used for detecting whether the fluctuation amplitude of the output feedback voltage exceeds a preset fluctuation range, and if so, generating a compensation adjustment voltage which changes in the opposite direction along with the amplitude value exceeding the fluctuation amplitude; if not, generating a compensation adjustment voltage with the amplitude smaller than a preset amplitude threshold value; superposing the compensation adjustment voltage on the first compensation voltage to obtain a second compensation voltage;
The conduction control circuit is used for controlling the conduction time of a power switch connected with a primary winding of a transformer in the switching power supply according to the second compensation voltage so as to enable the output feedback voltage to be stabilized to a preset first reference voltage; wherein the higher the second compensation voltage, the longer the on-time.
2. The switching power supply error compensation circuit of claim 1 wherein said error conversion circuit comprises:
The inverting input end is connected with the output feedback voltage, the non-inverting input end is connected with a first transconductance amplifier of a preset first reference voltage, and the first transconductance amplifier is used for obtaining a first error voltage between the output feedback voltage and the preset first reference voltage, amplifying the first error voltage and converting the first error voltage into a first error current and outputting the first error current.
3. The switching power supply error compensation circuit of claim 1 wherein said compensation circuit comprises:
The first end is respectively connected with the output end of the error conversion circuit and the nonlinear compensation circuit, and the second end is grounded.
4. A switching power supply error compensation circuit according to any one of claims 1 to 3, wherein said non-linear compensation circuit comprises:
The nonlinear transconductance circuit is used for detecting whether the fluctuation amplitude of the output feedback voltage exceeds a preset fluctuation range, and if so, generating a compensation current which changes in the opposite direction along with the amplitude value exceeding the fluctuation amplitude; if not, generating a compensation current with the amplitude smaller than the preset amplitude threshold value;
And the voltage compensation circuit is connected with the output end of the nonlinear transconductance circuit at a first end and the output end of the compensation circuit at a second end, and is used for converting the compensation current into compensation adjustment voltage and superposing the compensation adjustment voltage on the first compensation voltage to obtain a second compensation voltage.
5. The switching power supply error compensation circuit of claim 4 wherein said nonlinear transconductance circuit comprises a second transconductance amplifier, a third transconductance amplifier, a forward diode, and a reverse diode; wherein:
the non-inverting input end of the second transconductance amplifier is connected with a preset second reference voltage, the inverting input end of the second transconductance amplifier is connected with the output feedback voltage, the output end of the second transconductance amplifier is connected with the anode of the forward diode, the non-inverting input end of the third transconductance amplifier is connected with a preset third reference voltage, the inverting input end of the third transconductance amplifier is connected with the output feedback voltage, the output end of the third transconductance amplifier is connected with the cathode of the reverse diode, the cathode of the forward diode is connected with the anode of the reverse diode, and the common end of the forward diode is used as the output end of the nonlinear transconductance circuit; wherein the preset second reference voltage is less than the preset first reference voltage is less than the preset third reference voltage;
the N-th transconductance amplifier is used for solving an N-th error voltage between the output feedback voltage and a preset N-th reference voltage, amplifying the N-th error voltage and converting the N-th error voltage into an N-th error current to be output; where n=2, 3.
6. The switching power supply error compensation circuit of claim 4 wherein said nonlinear transconductance circuit comprises a second transconductance amplifier, a third transconductance amplifier, a forward diode, and a reverse diode; wherein:
The non-inverting input end of the second transconductance amplifier is connected with a preset second reference voltage, the inverting input end of the second transconductance amplifier is connected with the output feedback voltage, the output end of the second transconductance amplifier is connected with the anode of the forward diode and the common end of the second transconductance amplifier is connected with a preset first bias current, the non-inverting input end of the third transconductance amplifier is connected with a preset third reference voltage, the inverting input end of the third transconductance amplifier is connected with the output feedback voltage, the output end of the third transconductance amplifier is connected with the cathode of the reverse diode and the common end of the third transconductance amplifier is connected with a preset second bias current, and the cathode of the forward diode is connected with the anode of the reverse diode and the common end of the forward diode is used as the output end of the nonlinear transconductance circuit; wherein the preset second reference voltage and the preset third reference voltage are equal to the preset first reference voltage; the flow direction of the preset first bias current flows out of the output end of the second transconductance amplifier; the flow direction of the preset second bias current flows into the output end of the third transconductance amplifier;
the N-th transconductance amplifier is used for solving an N-th error voltage between the output feedback voltage and a preset N-th reference voltage, amplifying the N-th error voltage and converting the N-th error voltage into an N-th error current to be output; where n=2, 3.
7. The switching power supply error compensation circuit of claim 4 wherein said voltage compensation circuit comprises:
and the first end of the compensation resistor is connected with the output end of the nonlinear transconductance circuit, and the second end of the compensation resistor is connected with the output end of the compensation circuit.
8. The switching power supply error compensation circuit of claim 4, wherein said switching power supply error compensation circuit further comprises:
and the first end of the voltage buffer is connected with the output end of the compensation circuit, and the second end of the voltage buffer is connected with the second end of the voltage compensation circuit.
9. The switching power supply error compensation circuit of claim 1 wherein said switching power supply error compensation circuit is disposed entirely within a control chip of said switching power supply.
10. A switching power supply comprising a switching power supply error compensation circuit as claimed in any one of claims 1 to 9.
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