Control circuit, control method and switching power supply

Abstract

The invention provides a control circuit, a control method and a switching power supply, and the control circuit comprises a sampling error compensation module which is used for outputting an error compensation amount, and the error compensation amount is in positive correlation with a peak current flowing through a switching tube; the first input end of the loop correction module is coupled to the output end of the sampling error compensation module, a feedback voltage signal representing the output voltage of the switching power supply is connected to the second input end of the loop correction module, and the loop correction module compensates the feedback voltage signal based on the error compensation amount and outputs a loop correction voltage signal; the input end of the switch control module is coupled with the output end of the loop correction module, the output end of the switch control module is coupled with the control end of the switching tube of the switching power supply, and a control signal for controlling on-off of the switching tube is output based on the loop correction voltage signal. The feedback voltage signal is compensated by adopting the error compensation quantity which is positively correlated with the peak current flowing through the switching tube, so that the output voltage deviation caused by the voltage drop of the diode in the traditional switching power supply is overcome, and the influence of the conduction voltage drop of the fly-wheel diode on the feedback sampling is effectively eliminated; and the precision and the stability of the output voltage are obviously improved.

Description

Technical Field

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

[0002] Buck converters, a common switching power supply topology, are widely used in various electronic devices. Their main function is to convert a higher input voltage to a lower output voltage. Buck circuits have become an important solution in power management due to their simple structure and stable, reliable operation. Depending on the position of the power switch in the circuit, Buck circuits can be divided into two architectures: high-side Buck and low-side Buck. The high-side Buck architecture, due to its convenient feedback voltage acquisition, simple peripheral circuit design, and lower cost, dominates in cost-sensitive applications (such as auxiliary power supplies for small household appliances). In this architecture, the power switch (such as MOSFET, BJT, IGBT, or GaN FET) is typically configured high-side (i.e., connected between the input voltage and the inductor).

[0003] Traditional High Side Buck architecture and its control circuit, such as Figure 1 , Figure 2 As shown, the control circuit reference ground is connected to the source of the MOSFET, and the positive terminal of the output voltage is connected to the voltage divider resistor network (R) through the feedback diode VD1. F1 and R F2 To generate feedback voltage V FB V FB After processing by the sample-and-hold circuit, a compensation signal V is generated through a transconductance operational amplifier and an RC compensation network. EA The gate control signal for the MOSFET is then generated via PWM modulation and a drive circuit. A loop correction circuit (compensator) consisting of a transconductance operational amplifier and a resistor-capacitor compensation network is used to ensure system stability. The compensator can also be implemented using a voltage operational amplifier or digital circuitry. However, this architecture suffers from significant output voltage accuracy defects, stemming from the indirect control mechanism of the control loop. Specifically: 1) Feedback signal deviation problem: The control loop directly regulates the feedback voltage V. FB , and V FB The relationship between V and the output voltage Vo satisfies the formula: V FB =Vo + VF2 - VF1, where VF1 and VF2 are the forward voltage drops of the feedback diode VD1 and the freewheeling diode VD2, respectively. 2) Impact of voltage drop fluctuations: The forward voltage drop of the diode is easily affected by temperature changes, load current fluctuations, input voltage variations, and batch differences in components. This fluctuation leads to V FBAn uncontrollable deviation occurs between V and Vo, causing the control loop to be able to stabilize V. FB However, it cannot accurately stabilize Vo, which ultimately causes the output voltage to drift with the operating conditions and device parameters.

[0004] Existing high-side buck circuits rely on diode voltage drops to transmit feedback signals, resulting in output voltage accuracy being limited by parasitic parameters, making it difficult to meet the requirements of high-precision power supply applications. Therefore, a new structure or control method is needed to solve at least some of the aforementioned problems. Summary of the Invention

[0005] To address one or more problems in the background art, this invention proposes a control circuit, control method, and switching power supply. By performing error compensation on the feedback voltage signal, the influence of diode voltage drop on feedback sampling is eliminated, thereby improving the accuracy of the output voltage.

[0006] According to one aspect of the present invention, a control circuit for a switching power supply includes:

[0007] The sampling error compensation module is used to output the error compensation amount V. cp The error compensation amount V cp It is positively correlated with the peak current flowing through switch S1;

[0008] The loop correction module has a first input terminal coupled to the output terminal of the sampling error compensation module, and a second input terminal connected to the feedback voltage signal VFB, which characterizes the output voltage of the switching power supply. The loop correction module is based on the error compensation amount VFB. cp The feedback voltage signal VFB is compensated and a loop correction voltage signal V is output. EA ;

[0009] The switching control module has its input terminal coupled to the output terminal of the loop correction module, and its output terminal coupled to the control terminal of the switching power supply switching transistor S1, based on the loop correction voltage signal V. EA The output controls the switching signal of the transistor S1.

[0010] Optionally, the control circuit further includes:

[0011] The current reference generation circuit has its input terminal coupled to the output terminal of the loop correction module, and its output terminal coupled to the input terminal of the sampling error compensation module; the current reference generation circuit is based on the loop correction voltage signal V. EA Output current reference signal V OCP The sampling error compensation module is based on the current reference signal V. OCP Output error compensation amount V cp .

[0012] Optionally, the current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met:

[0013] When the loop correction voltage signal is less than the second threshold, the current reference signal is the minimum current reference signal;

[0014] When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal;

[0015] When the loop correction voltage signal is greater than the first threshold, the current reference signal is the maximum current reference signal.

[0016] Optionally, the error compensation amount V cp With the current reference signal V OCP They change proportionally.

[0017] Optionally, the control circuit further includes:

[0018] The comparator circuit has a first input terminal connected to a current sampling signal Vcs representing the current flowing through the switching transistor S1, a second input terminal coupled to the output terminal of the current reference generation circuit, and an output terminal coupled to the switch control module; the comparator circuit compares the current sampling signal Vcs with the current reference signal Vcs. OCP It outputs a detection signal, which is used to adjust the control signal.

[0019] Optionally, the control circuit further includes:

[0020] The sample-and-hold module has an input terminal that receives a current sampling signal Vcs representing the current flowing through the switching transistor S1, and an output terminal that is coupled to the input terminal of the sampling error compensation module. The sample-and-hold module outputs a peak current sampling signal Vcs1 based on the current sampling signal Vcs, and the sampling error compensation module outputs an error compensation amount V based on the peak current sampling signal Vcs1. cp .

[0021] Optionally, the control circuit further includes:

[0022] The current reference generation circuit has its input terminal coupled to the output terminal of the loop correction module. The current reference generation circuit is based on the loop correction voltage signal V. EA Output current reference signal V OCP ;

[0023] The comparator circuit has a first input terminal connected to a current sampling signal Vcs representing the current flowing through the switching transistor S1, a second input terminal coupled to the output terminal of the current reference generation circuit, and an output terminal coupled to the switch control module; the comparator circuit compares the current sampling signal Vcs with the current reference signal Vcs. OCP It outputs a detection signal, which is used to adjust the control signal.

[0024] Optionally, the control circuit further includes:

[0025] The input terminal of the sampling error compensation module is coupled to the output terminal of the loop correction module, and the sampling error compensation module is based on the loop correction voltage signal V. EA Output error compensation amount V cp ;

[0026] The current reference generation circuit has its input terminal coupled to the output terminal of the loop correction module. The current reference generation circuit is based on the loop correction voltage signal V. EA Output current reference signal V OCP ;

[0027] The comparator circuit has a first input terminal connected to a current sampling signal Vcs representing the current flowing through the switching transistor S1, a second input terminal coupled to the output terminal of the current reference generation circuit, and an output terminal coupled to the switch control module; the comparator circuit compares the current sampling signal Vcs with the current reference signal Vcs. OCP It outputs a detection signal, which is used to adjust the control signal.

[0028] Optionally, the error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met:

[0029] When the loop correction voltage signal is less than the second threshold, the error compensation amount is the second error compensation amount, and the current reference signal is the minimum current reference signal;

[0030] When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal.

[0031] When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

[0032] Optionally, the error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met:

[0033] When the loop correction voltage signal is less than the second threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from 0 to the second error compensation amount; the current reference signal is the minimum current reference signal;

[0034] When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal.

[0035] When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

[0036] Optionally, the loop correction module includes:

[0037] The signal conditioning circuit has a first input terminal coupled to the output terminal of the sampling error compensation module, and a second input terminal connected to the feedback voltage signal VFB that represents the output voltage of the switching power supply. The signal conditioning circuit performs error compensation on the feedback voltage signal VFB based on the error compensation amount Vcp and outputs the error-compensated feedback voltage signal VFB1.

[0038] The second sample and hold circuit has its input terminal coupled to the output terminal of the signal conditioning circuit. The second sample and hold circuit samples the feedback voltage signal VFB1 after error compensation and outputs the feedback voltage sampling signal VFB2.

[0039] The loop correction circuit has its input terminal coupled to the output terminal of the second sample-and-hold circuit, and its output terminal coupled to the input terminal of the switch control module; the loop correction circuit outputs a loop correction voltage signal V based on the feedback voltage sampling signal VFB2. EA .

[0040] According to another aspect of the present invention, a switching power supply includes a switching transistor S1 and a control circuit of any of the above, wherein the input terminal of the control circuit is connected to a feedback voltage signal VFB characterizing the output voltage of the switching power supply, and the output terminal is coupled to the control terminal of the switching transistor S1.

[0041] According to another aspect of the present invention, a control method for a switching power supply includes:

[0042] Obtain the error compensation amount V cp The error compensation amount V cp It is positively correlated with the peak current flowing through switch S1;

[0043] According to the error compensation amount V cp The feedback voltage signal VFB is compensated and a loop correction voltage signal VEA is output, wherein the feedback voltage signal VFB represents the output voltage of the switching power supply.

[0044] The loop correction voltage signal VEA is used to output a control signal, which controls the switching transistor S1 to turn on and off.

[0045] Optionally, the error compensation amount V cp The methods for obtaining it include:

[0046] The current reference signal V is generated based on the loop correction voltage signal VEA. OCP The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met: when the loop correction voltage signal is less than the second threshold, the current reference signal is the minimum current reference signal; when the loop correction voltage signal is greater than the second threshold and less than the first threshold, the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal; when the loop correction voltage signal is greater than the first threshold, the current reference signal is the maximum current reference signal.

[0047] According to the current reference signal V OCP Generate error compensation amount V cp The error compensation amount V cp With the current reference signal V OCP They change proportionally.

[0048] Optionally, the error compensation amount V cp The methods for obtaining it include:

[0049] A peak current sampling signal Vcs1 is generated based on the current sampling signal Vcs, wherein the current sampling signal Vcs represents the current flowing through the switching transistor S1.

[0050] An error compensation amount V is generated based on the peak current sampling signal Vcs1. cp .

[0051] Optionally, the error compensation amount V cp The methods for obtaining it include:

[0052] An error compensation amount V is generated based on the loop correction voltage signal VEA. cp and current reference signal V OCP The error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met:

[0053] When the loop correction voltage signal is less than the second threshold, the error compensation amount is the second error compensation amount, and the current reference signal is the minimum current reference signal;

[0054] When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal.

[0055] When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

[0056] Optionally, the error compensation amount V cp The methods for obtaining it include:

[0057] An error compensation amount V is generated based on the loop correction voltage signal VEA. cp and current reference signal V OCP The error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met:

[0058] When the loop correction voltage signal is less than the second threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from 0 to the second error compensation amount; the current reference signal is the minimum current reference signal;

[0059] When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal.

[0060] When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

[0061] Optionally, the method for obtaining the loop correction voltage signal VEA includes:

[0062] The feedback voltage signal VFB is error-compensated according to the error compensation amount Vcp, and the error-compensated feedback voltage signal VFB1 is output.

[0063] The feedback voltage signal VFB1 after error compensation is sampled and the feedback voltage sampling signal VFB2 is output.

[0064] Based on the feedback voltage sampling signal VFB2, a loop correction voltage signal V is generated. EA .

[0065] The control circuit, control method, and switching power supply proposed in this invention compensate for the error in the feedback voltage signal by using an error compensation amount that is positively correlated with the peak current flowing through the switching transistor. This overcomes the output voltage deviation caused by diode voltage drop in traditional switching power supplies, effectively eliminates the influence of freewheeling diode forward voltage drop on feedback sampling, and thus significantly improves the accuracy and stability of the output voltage. Attached Figure Description

[0066] The accompanying drawings are provided to further illustrate the invention and, together with the description, serve to explain embodiments of the invention, but do not constitute a limitation thereof. In the drawings:

[0067] Figure 1 A schematic diagram of a prior art high-side buck converter circuit is shown;

[0068] Figure 2 A block diagram of the control circuit for a prior art high-side buck converter is shown.

[0069] Figure 3 A structural block diagram of the control circuit of the present invention is shown;

[0070] Figure 4 A schematic diagram of the switching power supply and its control circuit structure of the present invention is shown.

[0071] Figure 5 A schematic diagram of a switching power supply and its control circuit according to an embodiment of the present invention is shown.

[0072] Figure 6 A schematic diagram of a switching power supply and its control circuit according to another embodiment of the present invention is shown.

[0073] Figure 7 A schematic diagram of a sample-and-hold module according to another embodiment of the present invention is shown;

[0074] Figure 8 A timing diagram of the sample-and-hold module according to another embodiment of the present invention is shown;

[0075] Figure 9 A schematic diagram of a switching power supply and its control circuit according to another embodiment of the present invention is shown;

[0076] Figure 10 One of the waveforms of the error compensation amount and the current reference signal as a function of the loop correction voltage signal is shown in another embodiment of the present invention;

[0077] Figure 11 The second waveform diagram of the error compensation amount and current reference signal changing with the loop correction voltage signal is shown in another embodiment of the present invention;

[0078] Figure 12 A schematic diagram of a second sample-and-hold circuit according to an embodiment of the present invention is shown;

[0079] Figure 13 The following is a timing diagram of the operation of a second sample-and-hold circuit according to an embodiment of the present invention. Detailed Implementation

[0080] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0081] The description in this section pertains to only a few typical embodiments, and the present invention is not limited to the scope of the embodiments described. Combinations of different embodiments, substitution of some technical features in different embodiments, and substitution of similar or identical prior art with some technical features in the embodiments are also within the scope of the description and protection of the present invention.

[0082] The terms "coupled" or "connected" in this specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection through an electrically conductive medium like a conductor, which may contain parasitic inductance or capacitance. It can also be a connection through intermediate circuits or components described in the embodiments of this specification. Indirect connections may also include connections through other active or passive devices that achieve the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, or other circuits or components. "Multiple" or "more" indicates two or more.

[0083] This invention proposes a control circuit for a switching power supply, wherein the switching power supply can be a buck switching power supply, a flyback switching power supply, or other voltage conversion circuits, such as... Figure 3 As shown, the control circuit includes a sampling error compensation module, a loop correction module, and a switch control module. (The following is a simplified description of the control circuit.) Figure 4 The control circuit is illustrated using the high-side step-down switching power supply shown as an example:

[0084] The sampling error compensation module is used to output the error compensation amount V. cp The error compensation amount V cp It is positively correlated with the peak current flowing through the switching transistor S1.

[0085] The first input terminal of the loop correction module is coupled to the output terminal of the sampling error compensation module, and the second input terminal is connected to the feedback voltage signal V, which characterizes the output voltage of the switching power supply. FB The loop correction module is based on the error compensation amount V. cp For the feedback voltage signal V FB Perform compensation and output loop correction voltage signal V EA .

[0086] The input terminal of the switch control module is coupled to the output terminal of the loop correction module, and the output terminal is coupled to the control terminal of the switching power supply switching transistor S1. The switch control module is based on the loop correction voltage signal V. EA The output controls the switching signal of the transistor S1.

[0087] In one embodiment, such as Figure 5 As shown, the control circuit further includes a current reference generation circuit, wherein:

[0088] The input terminal of the current reference generation circuit is coupled to the output terminal of the loop correction module, and the output terminal is coupled to the input terminal of the sampling error compensation module. The current reference generation circuit is based on the loop correction voltage signal V. EA Output current reference signal V OCP The sampling error compensation module is based on the current reference signal V. OCP Output error compensation amount V cp .

[0089] In one specific implementation, the current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met: (1) When the loop correction voltage signal V EA When the current reference signal V is less than the second threshold, OCP (2) When the loop correction voltage signal V is the minimum current reference signal; EA When the current reference signal V is greater than the second threshold and less than the first threshold, OCP With the loop correction voltage signal V EA The current increases linearly with the increase of the minimum current reference signal, changing from the minimum current reference signal to the maximum current reference signal; (3) when the loop correction voltage signal V EA When the current reference signal V is greater than the first threshold, OCPThis refers to the maximum current reference signal.

[0090] In another specific implementation, the error compensation amount V cp With the current reference signal V OCP They change proportionally.

[0091] Furthermore, such as Figure 5 As shown, the control circuit further includes a comparison circuit, wherein:

[0092] The first input terminal of the comparator circuit is connected to a current sampling signal Vcs, representing the current flowing through the switching transistor S1. The second input terminal is coupled to the output terminal of the current reference generation circuit, and the output terminal is coupled to the switch control module. The comparator circuit compares the current sampling signal Vcs with the current reference signal V. OCP It outputs a detection signal, which is used to adjust the control signal. When the current sampling signal Vcs is greater than or equal to the reference signal V... OCP When the current sampling signal Vcs is less than the reference signal V, the control signal is set to a low level. OCP When this occurs, the control signal is set to a high level.

[0093] In another embodiment, such as Figure 6 As shown, the control circuit further includes a sample-and-hold module, wherein:

[0094] The input of the sample-and-hold module is connected to a current sampling signal Vcs, representing the current flowing through the switching transistor S1, and the output is coupled to the input of the sampling error compensation module. The sample-and-hold module outputs a peak current sampling signal Vcs1 based on the current sampling signal Vcs, and the sampling error compensation module outputs an error compensation amount V based on the peak current sampling signal Vcs1. cp .

[0095] In one specific implementation, such as Figure 7 As shown, the sample-and-hold module includes a first sampling switch S. SH1 and the first holding capacitor C SH1 The first sampling switch S SH1 The first terminal is connected to a current sampling signal Vcs representing the current flowing through the switch S1. The first sampling switch S SH1 The second end is coupled to the first holding capacitor C SH1 The first end is coupled to the input end of the sampling error compensation module as the output end, and the first holding capacitor C SH1 The second terminal is grounded. The first sampling switch transistor S... SH1 The first sampling pulse signal Sample1 is generated based on the PWM signal, preferably, as follows: Figure 8 As shown, the falling edge of the first sampling pulse signal Sample1 is synchronized with the turn-off edge of the PWM signal. The first sampling pulse signal Sample1 is used to activate the first sampling switch S. SH1 When the circuit is turned on, the peak value of the current sampling signal Vcs is acquired, and the first sampling switch S... SH1 Output peak current sampling signal Vcs1.

[0096] In another specific implementation, such as Figure 6 As shown, the control circuit includes a sample-and-hold module, a current reference generation circuit, and a comparison circuit, wherein:

[0097] The input terminal of the current reference generation circuit is coupled to the output terminal of the loop correction module. The current reference generation circuit is based on the loop correction voltage signal V. EA Output current reference signal V OCP .

[0098] The first input terminal of the comparator circuit is connected to a current sampling signal Vcs representing the current flowing through the switching transistor S1. The second input terminal is coupled to the output terminal of the current reference generation circuit, and the output terminal is coupled to the switch control module. The comparator circuit compares the current sampling signal Vcs with the current reference signal V. OCP It outputs a detection signal, which is used to adjust the control signal.

[0099] In yet another embodiment, such as Figure 9 As shown, the control circuit further includes a current reference generation circuit and a comparison circuit, wherein:

[0100] The input terminal of the sampling error compensation module is coupled to the output terminal of the loop correction module. The sampling error compensation module is based on the loop correction voltage signal V. EA Output error compensation amount V cp .

[0101] The input terminal of the current reference generation circuit is coupled to the output terminal of the loop correction module. The current reference generation circuit is based on the loop correction voltage signal V. EA Output current reference signal V OCP .

[0102] The first input terminal of the comparator circuit is connected to a current sampling signal Vcs representing the current flowing through the switching transistor S1. The second input terminal is coupled to the output terminal of the current reference generation circuit, and the output terminal is coupled to the switch control module. The comparator circuit compares the current sampling signal Vcs with the current reference signal V. OCP It outputs a detection signal, which is used to adjust the control signal.

[0103] In one specific implementation, such as Figure 10 As shown, the error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met: (1) When the loop correction voltage signal V EA Less than the second threshold V EA_th2 At that time, the error compensation amount V cp The second error compensation amount V cp_th2 The current reference signal V OCP Minimum current reference signal V OCP_min (2) When the loop correction voltage signal V EA Greater than the second threshold V EA_th2 And less than the first threshold V EA_th1 At that time, the error compensation amount V cp With the loop correction voltage signal V EA The error compensation amount V increases linearly with the increase of V. cp_th2 Change to the first error compensation amount V EA_th1 The current reference signal V OCP With the loop correction voltage signal V EA The value increases linearly with the increase of the minimum current reference signal V. OCP_min Change to the maximum current reference signal V OCP_max (3) When the loop correction voltage signal V EA Greater than the first threshold V EA_th1 At that time, the error compensation amount V cp The first error compensation amount V cp_th1 The current reference signal V OCP The maximum current reference signal V OCP_max .

[0104] In another specific implementation, such as Figure 11 As shown, the error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met: (1) When the loop correction voltage signal V EA Less than the second threshold V EA_th2 At that time, the error compensation amount V cp With the loop correction voltage signal V EA The value increases linearly with the increase of the second error compensation amount V, changing from 0 to the second error compensation amount V. cp_th2 The current reference signal V OCP Minimum current reference signal V OCP_min(2) When the loop correction voltage signal V EA Greater than the second threshold V EA_th2 And less than the first threshold V EA_th1 At that time, the error compensation amount V cp With the loop correction voltage signal V EA The error compensation amount V increases linearly with the increase of V. cp_th2 Change to the first error compensation amount V cp_th1 The current reference signal V OCP With the loop correction voltage signal V EA The value increases linearly with the increase of the minimum current reference signal V. OCP_min Change to the maximum current reference signal V OCP_max (3) When the loop correction voltage signal V EA Greater than the first threshold V EA_th1 At that time, the error compensation amount V cp The first error compensation amount V cp_th1 The current reference signal V OCP The maximum current reference signal V OCP_max .

[0105] In one embodiment, such as Figure 4 As shown, the loop correction module includes a signal conditioning circuit, a second sample-and-hold circuit, and a loop correction circuit, wherein:

[0106] The first input terminal of the signal conditioning circuit is coupled to the output terminal of the sampling error compensation module, and the second input terminal is connected to the feedback voltage signal V, which characterizes the output voltage of the switching power supply. FB The signal conditioning circuit adjusts the feedback voltage signal V based on the error compensation amount Vcp. FB Perform error compensation and output the feedback voltage signal V after error compensation. FB1 ;

[0107] The input of the second sample-and-hold circuit is coupled to the output of the signal conditioning circuit. The second sample-and-hold circuit handles the error-compensated feedback voltage signal V. FB1 Sample and output feedback voltage sampling signal V FB2 ;

[0108] The input terminal of the loop correction circuit is coupled to the output terminal of the second sample-and-hold circuit, and the output terminal is coupled to the input terminal of the switch control module. The loop correction circuit is based on the feedback voltage sampling signal V. FB2 Output loop correction voltage signal V EA .

[0109] In one specific implementation, such as Figure 12As shown, the second sample-and-hold circuit includes a second sampling switch S. SH Second holding capacitor C SH The second sampling switch S SH The first terminal is coupled to the output terminal of the signal conditioning circuit, and the second sampling switch S SH The second end is coupled to the second holding capacitor C S The first terminal is coupled to the input terminal of the loop correction circuit as the output terminal, and the second holding capacitor C S The second terminal is grounded. The second sampling switch S... SH The second sampling pulse signal, Sample, is generated based on the PWM signal, preferably, as follows: Figure 13 As shown, when the PWM signal is set to a high level, the control switch S1 is turned on; after the PWM signal is set from a high level to a low level (at which time the switch S1 is turned off), after a blank time (preferably 2 microseconds), the second sampling pulse signal Sample is set to a high level and held for a preset time to superimpose the feedback signal V. FB1 Sampling is performed (the preset time for setting the second sampling pulse signal Sample to high level is preferably 1 microsecond), thereby ensuring that the second sample-and-hold circuit only performs sampling after the diode voltage drop stabilizes after the switch S1 is turned off, avoiding interference from the diode voltage drop during the sampling stage.

[0110] In one specific embodiment, the loop correction circuit includes a transconductance operational amplifier and an RC compensation network. Besides the aforementioned embodiment, other forms of loop correction circuits, such as voltage operational amplifiers and digital circuits, can also be directly applied to this control circuit to achieve an output loop correction voltage signal.

[0111] In one embodiment, such as Figure 4 As shown, the switch control module includes a PWM modulation circuit and a drive circuit, wherein:

[0112] The input terminal of the PWM modulation circuit is coupled to the output terminal of the loop correction module. The PWM modulation circuit is based on the loop correction voltage signal V. EA Output PWM signal.

[0113] The input terminal of the drive circuit is coupled to the output terminal of the PWM modulation circuit, and the output terminal is coupled to the control terminal of the switching transistor S1. The drive circuit outputs a drive signal based on the PWM signal, which drives the switching transistor S1 to turn on and off. Specifically, when the PWM signal is high, it drives the switching transistor S1 to turn on (the switching power supply operates).

[0114] The present invention also proposes a switching power supply, including a switching transistor S1 and any of the above-mentioned control circuits, wherein the input terminal of the control circuit is connected to a feedback voltage signal V characterizing the output voltage of the switching power supply. FB The output terminal is coupled to the control terminal of the switching transistor S1. Specifically, the switching transistor S1 can be a power device such as a MOSFET, a single-transistor BJT, a Darlington BJT, an IGBT, or a GaN FET. In one embodiment, the switching power supply can be a buck circuit, which includes a MOSFET, a diode, an inductor, an output capacitor, and any of the above-mentioned control circuits, wherein: the drain of the MOSFET is connected to the input voltage, and the source is coupled to the anode of the diode and the first end of the inductor; the cathode of the diode is grounded; the second end of the inductor is coupled to the first end of the output capacitor; the second end of the output capacitor is grounded; the load is coupled between the second end of the inductor and ground; the input terminal of the control circuit is connected to the output voltage feedback signal of the buck circuit, and the output terminal is coupled to the gate of the MOSFET. In another embodiment, the switching power supply can be a flyback switching power supply, which includes a switching transistor and any of the above-mentioned control circuits. The control circuit obtains the output voltage feedback signal through an auxiliary winding and outputs a control signal to control the switching transistor to turn on and off.

[0115] This invention also proposes a control method, comprising:

[0116] Obtain the error compensation amount V cp The error compensation amount V cp It is positively correlated with the peak current flowing through switch S1;

[0117] According to the error compensation amount V cp For the feedback voltage signal V FB Perform compensation and output loop correction voltage signal V EA The feedback voltage signal V FB Characterizes the output voltage of the switching power supply;

[0118] According to the loop correction voltage signal V EA Output control signal, which controls the switching transistor S1 to turn on and off.

[0119] In one embodiment, the error compensation amount V cp The methods for obtaining it include:

[0120] 1) Based on the loop correction voltage signal V EA Generate current reference signal V OCP The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met: A. When the loop correction voltage signal V... EA When the current reference signal V is less than the second threshold,OCP A. Minimum current reference signal; B. When the loop correction voltage signal V EA When the current reference signal V is greater than the second threshold and less than the first threshold, OCP With the loop correction voltage signal V EA The current increases linearly with the increase of the minimum current reference signal, changing from the maximum current reference signal; C, when the loop correction voltage signal V... EA When the current reference signal V is greater than the first threshold, OCP The maximum current reference signal;

[0121] 2) Based on the current reference signal V OCP Generate error compensation amount V cp The error compensation amount V cp With the current reference signal V OCP They change proportionally.

[0122] In another embodiment, the error compensation amount V cp The methods for obtaining it include:

[0123] 1) Generate a peak current sampling signal Vcs1 based on the current sampling signal Vcs, wherein the current sampling signal Vcs represents the current flowing through the switching transistor S1;

[0124] 2) Generate error compensation amount V based on the peak current sampling signal Vcs1. cp .

[0125] In yet another embodiment, the error compensation amount V cp The methods for obtaining it include:

[0126] 1) Based on the loop correction voltage signal V EA Generate error compensation amount V cp and current reference signal V OCP ,like Figure 10 As shown, the error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met:

[0127] A. When the loop correction voltage signal V EA Less than the second threshold V EA_th2 At that time, the error compensation amount V cp The second error compensation amount V cp_th2 The current reference signal V OCP Minimum current reference signal V OCP_min ;

[0128] B. When the loop correction voltage signal VEA Greater than the second threshold V EA_th2 And less than the first threshold V EA_th1 At that time, the error compensation amount V cp With the loop correction voltage signal V EA The error compensation amount V increases linearly with the increase of V. cp_th2 Change to the first error compensation amount V cp_th1 The current reference signal V OCP With the loop correction voltage signal V EA The value increases linearly with the increase of the minimum current reference signal V. OCP_min Change to the maximum current reference signal V OCP_max ;

[0129] C. When the loop correction voltage signal V EA Greater than the first threshold V EA_th1 At that time, the error compensation amount V cp The first error compensation amount V cp_th1 The current reference signal V OCP The maximum current reference signal V OCP_max .

[0130] In yet another embodiment, the error compensation amount V cp The methods for obtaining it include:

[0131] 1) Based on the loop correction voltage signal V EA Generate error compensation amount V cp and current reference signal V OCP ,like Figure 11 As shown, the error compensation amount V cp The current reference signal V OCP With the loop correction voltage signal V EA The following conditions must be met:

[0132] A. When the loop correction voltage signal V EA Less than the second threshold V EA_th2 At that time, the error compensation amount V cp With the compensation voltage signal V EA The sign increases linearly, changing from 0 to the second error compensation amount V. cp_th2 The current reference signal V OCP Minimum current reference signal V OCP_min ;

[0133] B. When the loop correction voltage signal V EA Greater than the second threshold V EA_th2 And less than the first threshold V EA_th1 At that time, the error compensation amount Vcp The error compensation amount V increases linearly with the increase of the loop correction voltage signal. cp_th2 Change to the first error compensation amount V cp_th1 The current reference signal V OCP With the loop correction voltage signal V EA The value increases linearly with the increase of the minimum current reference signal V. OCP_min Change to the maximum current reference signal V OCP_max ;

[0134] C. When the loop correction voltage signal V EA Greater than the first threshold V EA_th1 At that time, the error compensation amount V cp The first error compensation amount V cp_th1 The current reference signal V OCP The maximum current reference signal V OCP_max .

[0135] In one embodiment, the loop correction voltage signal V EA The methods for obtaining it include:

[0136] 1) Adjust the feedback voltage signal V based on the error compensation amount Vcp. FB Perform error compensation and output the feedback voltage signal V after error compensation. FB1 ;

[0137] 2) The feedback voltage signal V after error compensation FB1 Sample and output feedback voltage sampling signal V FB2 ;

[0138] 3) Based on the feedback voltage sampling signal V FB2 Generate loop correction voltage signal V EA .

[0139] Those skilled in the art should know that the logic controls such as "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "non-inverting input" and "inverting input" in the logic control involved in the specification or drawings can be interchanged or changed, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic control.

[0140] The description and application of the present invention herein are illustrative and not intended to limit the scope of the invention to the embodiments described above. The effects or advantages described in the specification may not be apparent in actual experimental cases due to uncertainties in specific conditions or other factors, and such descriptions are not intended to limit the scope of the invention. Variations and modifications to the embodiments disclosed herein are possible, and various substitutions and equivalents of the components in the embodiments are well known to those skilled in the art. It should be understood by those skilled in the art that the invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the invention. Other variations and modifications can be made to the embodiments disclosed herein without departing from the scope and spirit of the invention.

Claims

1. A control circuit for a switching power supply, characterized in that, include: A sampling error compensation module is used to output an error compensation amount, which is positively correlated with the peak current flowing through the switching transistor; The loop correction module has a first input terminal coupled to the output terminal of the sampling error compensation module, and a second input terminal connected to a feedback voltage signal characterizing the output voltage of the switching power supply. The loop correction module compensates the feedback voltage signal based on the error compensation amount and outputs a loop correction voltage signal. The switch control module has its input terminal coupled to the output terminal of the loop correction module and its output terminal coupled to the control terminal of the switching power supply transistor. Based on the loop correction voltage signal, it outputs a control signal to control the switching transistor to turn on or off.

2. The control circuit according to claim 1, characterized in that, The control circuit further includes: The current reference generation circuit has its input terminal coupled to the output terminal of the loop correction module and its output terminal coupled to the input terminal of the sampling error compensation module. The current reference generation circuit outputs a current reference signal based on the loop correction voltage signal, and the sampling error compensation module outputs an error compensation amount based on the current reference signal.

3. The control circuit according to claim 2, characterized in that, The current reference signal and the loop correction voltage signal satisfy the following: When the loop correction voltage signal is less than the second threshold, the current reference signal is the minimum current reference signal; When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal; When the loop correction voltage signal is greater than the first threshold, the current reference signal is the maximum current reference signal.

4. The control circuit according to claim 2 or 3, characterized in that, The error compensation amount varies proportionally with the current reference signal.

5. The control circuit according to claim 2, characterized in that, The control circuit further includes: The comparator circuit has a first input terminal connected to a current sampling signal representing the current flowing through the switching transistor, a second input terminal coupled to the output terminal of the current reference generation circuit, and an output terminal coupled to the switching control module. The comparator circuit compares the current sampling signal with the current reference signal and outputs a detection signal, which is used to adjust the control signal.

6. The control circuit according to claim 1, characterized in that, The control circuit further includes: The sample-and-hold module has a current sampling signal representing the current flowing through the switching transistor as its input terminal, and its output terminal is coupled to the input terminal of the sampling error compensation module. The sample-and-hold module outputs a peak current sampling signal based on the current sampling signal, and the sampling error compensation module outputs an error compensation amount based on the peak current sampling signal.

7. The control circuit according to claim 6, characterized in that, The control circuit further includes: The current reference generation circuit has its input terminal coupled to the output terminal of the loop correction module, and outputs a current reference signal based on the loop correction voltage signal. The comparator circuit has a first input terminal connected to a current sampling signal representing the current flowing through the switching transistor, a second input terminal coupled to the output terminal of the current reference generation circuit, and an output terminal coupled to the switching control module. The comparator circuit compares the current sampling signal with the current reference signal and outputs a detection signal, which is used to adjust the control signal.

8. The control circuit according to claim 1, characterized in that, The control circuit further includes: The input terminal of the sampling error compensation module is coupled to the output terminal of the loop correction module, and the sampling error compensation module outputs the error compensation amount based on the loop correction voltage signal; The current reference generation circuit has its input terminal coupled to the output terminal of the loop correction module, and outputs a current reference signal based on the loop correction voltage signal. The comparator circuit has a first input terminal connected to a current sampling signal representing the current flowing through the switching transistor, a second input terminal coupled to the output terminal of the current reference generation circuit, and an output terminal coupled to the switching control module. The comparator circuit compares the current sampling signal with the current reference signal and outputs a detection signal, which is used to adjust the control signal.

9. The control circuit according to claim 8, characterized in that, The error compensation amount, the current reference signal, and the loop correction voltage signal satisfy the following: When the loop correction voltage signal is less than the second threshold, the error compensation amount is the second error compensation amount, and the current reference signal is the minimum current reference signal; When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; The current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal; When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

10. The control circuit according to claim 8, characterized in that, The error compensation amount V cp The current reference signal and the loop correction voltage signal satisfy the following: When the loop correction voltage signal is less than the second threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from 0 to the second error compensation amount; the current reference signal is the minimum current reference signal; When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; The current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal; When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

11. The control circuit according to claim 1, characterized in that, The loop correction module includes: The signal conditioning circuit has a first input terminal coupled to the output terminal of the sampling error compensation module, and a second input terminal connected to a feedback voltage signal characterizing the output voltage of the switching power supply. The signal conditioning circuit performs error compensation on the feedback voltage signal based on the error compensation amount and outputs the error-compensated feedback voltage signal. The second sample-and-hold circuit has its input terminal coupled to the output terminal of the signal conditioning circuit. The second sample-and-hold circuit samples the feedback voltage signal after error compensation and outputs the feedback voltage sampling signal. The loop correction circuit has its input terminal coupled to the output terminal of the second sample-and-hold circuit, and its output terminal coupled to the input terminal of the switch control module; the loop correction circuit outputs a loop correction voltage signal based on the feedback voltage sampling signal.

12. A switching power supply, characterized in that, It includes a switching transistor and a control circuit as described in any one of claims 1-11, wherein the input terminal of the control circuit is connected to a feedback voltage signal characterizing the output voltage of the switching power supply, and the output terminal is coupled to the control terminal of the switching transistor.

13. A control method for a switching power supply, characterized in that, include: Obtain the error compensation amount, which is positively correlated with the peak current flowing through the switching transistor; The feedback voltage signal is compensated according to the error compensation amount, and a loop correction voltage signal is output, wherein the feedback voltage signal represents the output voltage of the switching power supply. The loop correction voltage signal is used to output a control signal, which controls the switching transistor to turn on and off.

14. The control method according to claim 13, characterized in that, The method for obtaining the error compensation amount includes: A current reference signal is generated based on the loop correction voltage signal. The current reference signal and the loop correction voltage signal satisfy the following conditions: when the loop correction voltage signal is less than a second threshold, the current reference signal is the minimum current reference signal; when the loop correction voltage signal is greater than the second threshold and less than a first threshold, the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal; when the loop correction voltage signal is greater than the first threshold, the current reference signal is the maximum current reference signal. An error compensation amount is generated based on the current reference signal, and the error compensation amount varies proportionally to the current reference signal.

15. The control method according to claim 13, characterized in that, The method for obtaining the error compensation amount includes: A peak current sampling signal is generated based on the current sampling signal, wherein the current sampling signal represents the current flowing through the switching transistor; An error compensation amount is generated based on the peak current sampling signal.

16. The control method according to claim 13, characterized in that, The method for obtaining the error compensation amount includes: An error compensation amount and a current reference signal are generated based on the loop correction voltage signal, and the error compensation amount, the current reference signal, and the loop correction voltage signal satisfy the following relationship: When the loop correction voltage signal is less than the second threshold, the error compensation amount is the second error compensation amount, and the current reference signal is the minimum current reference signal; When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal. When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

17. The control method according to claim 13, characterized in that, The method for obtaining the error compensation amount includes: An error compensation amount and a current reference signal are generated based on the loop correction voltage signal, and the error compensation amount, the current reference signal, and the loop correction voltage signal satisfy the following relationship: When the loop correction voltage signal is less than the second threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from 0 to the second error compensation amount; the current reference signal is the minimum current reference signal; When the loop correction voltage signal is greater than the second threshold and less than the first threshold, the error compensation amount increases linearly with the increase of the loop correction voltage signal, changing from the second error compensation amount to the first error compensation amount; the current reference signal increases linearly with the increase of the loop correction voltage signal, changing from the minimum current reference signal to the maximum current reference signal. When the loop correction voltage signal is greater than the first threshold, the error compensation amount is the first error compensation amount, and the current reference signal is the maximum current reference signal.

18. The control method according to claim 13, characterized in that, The method for obtaining the loop correction voltage signal includes: The feedback voltage signal is error-compensated according to the error compensation amount, and the error-compensated feedback voltage signal is output. The feedback voltage signal after error compensation is sampled and the feedback voltage sampling signal is output. A loop correction voltage signal is generated based on the feedback voltage sampling signal.

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