Self-adaptive current compensation control circuit, control method and switching power supply

Abstract

The invention discloses a self-adaptive current compensation control circuit, a control method and a switching power supply, sampling information of inductive current is obtained through a sampling circuit, and then the sampling information of the inductive current is controlled to be sampled and held in a preset time signal according to a switching control signal and the preset time signal. According to the technical scheme, the compensation signal delayed by the line voltage is obtained, and the compensation signal is compensated to the comparison circuit for comparing the current sampling signal with the reference signal, so that peak current control can be accurately realized, additional pins and setting of system parameters are not needed, the cost can be saved, and the scheme of the invention is simple and reliable in control.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and more specifically, to an adaptive current compensation control circuit, a control method and a switching power supply. Background Art

[0002] During the operation of the switching power supply, it is usually necessary to sample the inductor current information of the switching power supply in order to adjust the output signal accordingly. However, in the actual operation process, due to the influence of the line voltage in the circuit, for example, changes in the line voltage will cause the rising slope of the inductor current of the power supply system to change. Therefore, there is a certain delay in the control of the system. Under different line voltages, due to the delay time, the difference between the sampled peak current and the reference current will increase, and the sampled peak current cannot be effectively limited, which will further cause the saturation problem of the magnetic device. Moreover, under the condition of a wide range of line voltages, it will cause a large difference between the low-voltage and high-voltage peak currents, causing high-voltage overpower or low-voltage underpower problems.

[0003] Traditional solutions such as Figure 1 As shown, by introducing a and V BUS The current proportional to the compensation is obtained, for example, by obtaining V through the Vs pin. BUS Information is used to accurately control the peak current. However, as the system requires a more streamlined design, it is necessary to consider how the periphery can provide the freedom of parameter selection to compensate and adjust the line voltage. The existing solution cannot meet the existing control requirements. Therefore, it is necessary to provide an improved technical solution to overcome the above technical problems existing in the prior art. Summary of the invention

[0004] In view of this, an object of the present invention is to provide an adaptive current compensation control circuit, a control method and a switching power supply, so as to solve the technical problem that the switching power supply in the prior art cannot flexibly perform current compensation according to the peripheral circuit.

[0005] Provided is an adaptive current compensation control circuit, which is applied to a switching power supply, wherein the switching power supply comprises a main power switch tube and an excitation inductor, and the control circuit comprises: a sampling circuit, which is used to sample current information of the excitation inductor to obtain a current sampling signal; a compensation circuit, which receives the current sampling signal and samples and holds the current sampling signal within a preset time to obtain a compensation signal, wherein the preset time length is set according to a line voltage delay parameter in the circuit; a comparison circuit, which receives the current sampling signal and a reference signal to obtain a comparison signal, wherein the compensation signal compensates the current sampling signal or the reference signal; and a drive circuit, which generates a switch control signal according to the comparison signal to control the switching action of the main power switch tube.

[0006] Preferably, the delay parameter includes at least one of a delay time of a sampling circuit, a delay time of a comparison circuit and a delay time of a driving circuit.

[0007] Preferably, the preset time length is set to be the sum of at least two of the delay time of the sampling circuit, the delay time of the comparison circuit and the delay time of the driving circuit.

[0008] Preferably, the preset time is set within a conduction time period of the main power switch tube.

[0009] Preferably, the sampling circuit comprises a switch tube, and the switch tube is arranged in a mirror image with the main power switch tube, and the current sampling signal is obtained by sampling the current information of the switch tube.

[0010] Preferably, the sampling circuit comprises a sampling resistor, the sampling resistor is connected in series with the main power switch tube, and the current sampling signal is obtained by sampling current information of the sampling resistor.

[0011] Preferably, the compensation signal is superimposed on the current sampling signal to obtain a superimposed signal, and the comparison circuit compares the superimposed signal with the reference signal to obtain the comparison signal.

[0012] Preferably, the compensation signal is superimposed on the reference signal to obtain a superimposed signal, and the comparison circuit compares the superimposed signal with the circuit sampling signal to obtain the comparison signal.

[0013] Preferably, the compensation circuit includes a filtering circuit and a holding capacitor, the current sampling signal is transmitted to the filtering circuit through a first switching circuit to obtain a filtering signal, the filtering signal is transmitted to the holding circuit through a second switching circuit to obtain a sampling and holding signal, and the sampling and holding signal is output as a compensation signal; wherein, the first switching circuit and the second switching circuit control whether to be turned on or off according to the switching control signal and a preset time.

[0014] Preferably, the compensation circuit comprises: when the second switch circuit is turned on at the rising edge of the switch control signal representing the turning on of the main power switch tube, the compensation signal is transmitted to the comparison circuit within the current switching cycle;

[0015] When the second switch circuit is turned on at the falling edge of the switch control signal representing the turning on of the main power switch tube, the compensation signal is sampled and held in the current switching cycle, and the compensation signal is transmitted to the comparison circuit in the next switching cycle.

[0016] Preferably, the compensation circuit further comprises a proportional adjustment circuit, which is connected to the output end of the holding capacitor to perform proportional conversion on the sampled and held signal and output the proportionally converted signal as the compensation signal.

[0017] In a second aspect, an adaptive current compensation control method is provided, which is applied to a switching power supply, wherein the switching power supply includes a main power switch tube and an excitation inductor, and includes the following steps:

[0018] Sampling the current information of the excitation inductor to obtain a current sampling signal; receiving the current sampling signal, and sampling and holding the current sampling signal within a preset time to obtain a compensation signal, receiving the current sampling signal and a reference signal to obtain a comparison signal, the compensation signal compensates the current sampling signal or the reference signal; generating a switch control signal according to the comparison signal to control the switching action of the main power switch tube; the preset time length is set to the sum of at least two of the delay time of the sampling circuit, the delay time of the comparison circuit and the delay time of the drive circuit.

[0019] Preferably, the preset time is set within a conduction time period of the main power switch tube.

[0020] Preferably, the current sampling signal is transmitted to the filtering circuit through the first switching circuit to obtain a filtering signal, and the filtering signal is transmitted to the holding circuit through the second switching circuit to obtain a sampling and holding signal, and the sampling and holding signal is output as a compensation signal; wherein, the first switching circuit and the second switching circuit control whether to be turned on or off according to the switching control signal and a preset time.

[0021] Preferably, the sample-and-hold signal is scaled, and the scaled signal is output as a compensation signal.

[0022] In a third aspect, a switching power supply is provided, comprising a main power switch tube and an excitation inductor, and comprising the above-mentioned adaptive current compensation control circuit, wherein the current compensation control circuit is used to control the switching state of the main power switch tube to control the output voltage of the switching power supply to a desired value.

[0023] The adaptive current compensation control circuit of the present invention obtains the inductor current sampling information by multiplexing the sampling pins, and then controls the sampling and holding of the inductor current sampling information within the preset time signal according to the switch control signal and the preset time signal, so as to obtain the compensation signal delayed by the line voltage, and the compensation signal is compensated to the comparison circuit for comparing the current sampling signal and the reference signal, so that the peak current control can be accurately realized without the need for setting additional pins and system parameters, which can save costs. The control scheme of the present invention is simple and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A circuit block diagram of an existing switching power supply with inductance sampling compensation;

[0025] Figure 2 A first circuit diagram (current mirror sampling) of the adaptive current compensation control circuit according to the present invention;

[0026] Figure 3 A second circuit diagram (resistance sampling) of the adaptive current compensation control circuit according to the present invention;

[0027] Figure 4 Based on Figure 2 A circuit diagram for realizing a first compensation method of an adaptive current compensation control circuit;

[0028] Figure 5 Based on Figure 2 A circuit diagram for realizing a second compensation method of an adaptive current compensation control circuit;

[0029] Figure 6 Based on Figure 3 A circuit diagram for realizing a first compensation method of an adaptive current compensation control circuit;

[0030] Figure 7 A circuit diagram for realizing a compensation circuit according to the present invention;

[0031] Figure 8 FIG. 4 is a working waveform diagram according to the present invention. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0033] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these detailed descriptions.

[0034] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportion, and are only used for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0035] refer to Figure 2 The first circuit diagram of the adaptive current compensation control circuit according to the present invention and the reference Figure 4 and Figure 5 Based on Figure 2 The adaptive current compensation control circuit in the embodiment of the present application is applied to a switching power supply, which can be but is not limited to Figure 1 The flyback switching power supply in the embodiment of the present invention comprises a main power switch tube Qm and an excitation inductor (here, the primary winding of the transformer), and the control circuit comprises a sampling circuit, a compensation circuit, a comparison circuit and a drive circuit, wherein the sampling circuit is used to sample the current information of the excitation inductor to obtain a current sampling signal, specifically, as Figure 4 As shown, one implementation of the sampling circuit includes a switch tube Q1, which is mirrored with the main power switch tube, and the current sampling signal Vcs is obtained by sampling the current information of the switch tube. It is known to those skilled in the art that the sampling circuit also includes other devices such as switches and resistors, which are not shown here.

[0036] Specifically, the compensation circuit receives the current sampling signal and samples and holds the current sampling signal within a preset time to obtain a compensation signal, and the preset time length is set according to the line voltage delay parameter in the circuit. Preferably, the delay parameter includes at least one of the delay time of the sampling circuit, the delay time of the comparison circuit and the delay time of the drive circuit. Further preferably, the preset time length is set to the sum of at least two of the delay time of the sampling circuit, the delay time of the comparison circuit and the delay time of the drive circuit. Specifically, Figure 7 1 is a circuit diagram of a compensation circuit according to the present invention; the compensation circuit includes a filter circuit (such as resistors R1 and C1) and a holding capacitor (such as capacitor C2), the current sampling signal is transmitted to the filter circuit through a first switch circuit such as switch S1 to obtain a filter signal VS1, and the filter signal is transmitted to the holding circuit through a second switch circuit such as switch S2 to obtain a sample holding signal V S1S, the sampling and holding signal is output as the compensation signal Vcsc; wherein the first switch circuit and the second switch circuit control whether to open or not according to the switch control signal PWM and the preset time Dalay time. Here, the preset time Dalay time may be the sum of the delay time of the sampling circuit, the delay time of the comparison circuit and the delay time of the driving circuit, so that the delay of each circuit line can be considered more comprehensively and more accurate compensation can be achieved. It should be noted that the preset time is set within the conduction time period of the main power switch tube, which may be a time period from the beginning of the conduction time period of the main power switch tube, or a time period from a certain moment of the conduction time period. The first switch circuit controls its state through the first switch control circuit, and the second switch circuit controls its state through the second switch control circuit. The first switch control circuit generates a switch signal TREF to control the first switch circuit according to the switch control signal PWM and the preset time Dalay time, and the second switch circuit generates a switch control signal for the second switch circuit according to the switch signal TREF and the switch control signal PWM. The first switch control circuit may be some logic circuits, such as inverters and AND logic circuits, or a combination control circuit of some switches, and the second switch control circuit may be a circuit structure such as a pulse circuit and a trigger.

[0037] Continue to refer Figure 3 The comparison circuit receives the current sampling signal Vcs and the reference signal Vcsref to obtain a comparison signal, wherein the compensation signal compensates the current sampling signal or the reference signal. In one example, reference Figure 4 , the compensation signal is superimposed on the current sampling signal to obtain a superimposed signal, and the comparison circuit compares the superimposed signal with the reference signal to obtain a comparison signal. In another example, referring to Figure 5 The compensation signal is superimposed on the reference signal to obtain a superimposed signal, and the comparison circuit compares the superimposed signal with the circuit sampling signal to obtain a comparison signal. The comparison circuit can be a circuit structure such as a comparator comp.

[0038] Specifically, the drive circuit generates a switch control signal according to the comparison signal to control the switching action of the main power switch tube. The drive circuit can be a drive circuit structure in the prior art, such as a drive circuit composed of a switch tube. Here, the drive circuit generates a switch control signal according to the comparison signal to control the shutdown of the main power switch tube.

[0039] like Figure 8As shown, in the high-level effective stage of the switch control signal PWM, the main power switch tube is turned on, and the compensation circuit samples and holds the current sampling signal CS to obtain the sampled and held signal Vcs, such as sampling and holding the current sampling signal within the time period of the sum of the delay time t1 of the sampling circuit, the delay time t2 of the comparison circuit and the delay time t3 of the drive circuit to obtain the held signal V S1_S , keep the signal V S1_S After the proportional transformation, the compensation signal Vcsc is obtained. The compensation signal Vcsc is a DC signal of a certain magnitude. Finally, the comparison circuit superimposes the compensation signal and the current sampling signal to obtain the superimposed signal Vdj, such as Figure 8 As shown, the superimposed signal is finally compared with the reference signal. When the superimposed signal reaches the reference signal, the main power tube is turned off. Through the above process, accurate peak current control can be achieved. The present application solution stores the current information of the current cycle or the previous cycle, obtains the current deviation of the internal delay of the chip, and compensates for the current cycle or the next cycle to achieve adaptive peak current precision control. No additional PIN pins and system parameter settings are required, which saves costs, is simple and reliable.

[0040] Book Figure 4 In the example shown, a resistor R1 is also included, and the resistor R1 is connected to the pin CS, and the compensation circuit is connected to the sampling circuit and the CS pin, so as to obtain a current sampling signal. In another example, the resistor R1 can be set inside the chip of the control circuit, and the compensation circuit is connected to the sampling circuit to obtain a current sampling signal.

[0041] Preferably, the compensation circuit can perform compensation in the current switching cycle or in the next switching cycle, referring to Figure 7 In the compensation circuit structure, when the second switch circuit is turned on at the rising edge of the switch control signal representing the turning on of the main power switch tube, the compensation signal is transmitted to the comparison circuit in the current switching cycle; when the second switch circuit is turned on at the falling edge of the switch control signal representing the turning on of the main power switch tube, the compensation signal is sampled and held in the current switching cycle, and the compensation signal is transmitted to the comparison circuit in the next switching cycle. Another compensation method may be that the second switch circuit is always turned on, and a switch tube control is set on the path of the compensation signal transmitted to the comparison circuit, and whether to perform compensation in the current switching cycle or the next switching cycle is determined by controlling the turn-on time of the switch tube.

[0042] Preferably, the compensation circuit also includes a proportional adjustment circuit, which is connected to the output end of the holding capacitor to perform proportional conversion on the sampled holding signal and output the proportionally converted signal as a compensation signal. Adding a proportional adjustment circuit can solve the problem of sampling interference signals when the signal is sampled. At the moment when the main power switch tube is turned on, due to the influence of parasitic capacitance, interference fluctuations will appear on the signal; if a smaller sampling time is set, interference waveforms will be sampled and accurate compensation cannot be achieved; therefore, a longer sampling and holding time can be used, which will increase the compensation amount, and then the compensation signal can be reduced through the proportional link to adjust it to the increase caused by the delay time that needs to be compensated, which can improve the sampling accuracy.

[0043] refer to Figure 3 A second circuit diagram of the adaptive current compensation control circuit according to the present invention and Figure 6 Based on Figure 3 The first compensation method of the adaptive current compensation control circuit is implemented in the circuit diagram. In this embodiment, the sampling circuit includes a sampling resistor Rc, which is connected in series with the main power switch tube, and the current sampling signal is obtained by sampling the current information of the sampling resistor. Figure 6 In the example shown, the sampling circuit in the control circuit may also include a sampling voltage-dividing resistor to divide the voltage with the external sampling resistor Rc to obtain a current sampling signal of appropriate size. The compensation circuit in this example may be Figure 7 Similar to the structure in , the current sampling signal of this example is compensated by the compensation circuit to obtain a compensation signal, and the compensation signal can be compensated to the sampling signal end in the comparison circuit or to the reference signal end.

[0044] The present application provides an adaptive current compensation control method, which is applied to a switching power supply, wherein the switching power supply includes a main power switch tube and an excitation inductor, and includes the following steps:

[0045] Sampling the current information of the excitation inductor to obtain a current sampling signal; receiving the current sampling signal, and sampling and holding the current sampling signal within a preset time to obtain a compensation signal, receiving the current sampling signal and a reference signal to obtain a comparison signal, wherein the compensation signal compensates the current sampling signal or the reference signal;

[0046] Generate a switch control signal according to the comparison signal to control the switching action of the main power switch tube;

[0047] The preset time length is set to be the sum of at least two of the delay time of the sampling circuit, the delay time of the comparison circuit, and the delay time of the driving circuit.

[0048] Preferably, the preset time is set within a conduction time period of the main power switch tube.

[0049] Preferably, the current sampling signal is transmitted to the filter circuit through the first switch circuit to obtain a filter signal.

[0050] The filtered signal is transmitted to the holding circuit through the second switch circuit to obtain a sample holding signal, and the sample holding signal is output as a compensation signal;

[0051] The first switch circuit and the second switch circuit are controlled to be turned on or off according to the switch control signal and a preset time.

[0052] Preferably, the sample-and-hold signal is proportionally transformed, and the proportionally transformed signal is output as a compensation signal.

[0053] Finally, the present application provides a switching power supply, a switching power supply, including a main power switch tube and an excitation inductor, and also including the adaptive current compensation control circuit, the current compensation control circuit is used to control the switching state of the main power switch tube to control the output voltage of the switching power supply to the desired value. The switching power supply of the present application stores the current information of the current cycle or the previous cycle, obtains the current deviation of the internal delay of the chip, and compensates for the current cycle or the next cycle, so as to realize adaptive peak current precision control, without the need for additional PIN pins and system parameter settings, saving costs, being simple and reliable.

[0054] It should be noted that the specific implementation and corresponding illustrations given are merely a way of describing the implementation method of the present invention, and do not limit the specific structure of the implementation scheme of the present invention. Various changes or modifications can be made to these implementation schemes without departing from the principle and essence of the present invention, but these changes and modifications fall within the scope of protection of the present invention.

[0055] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0056] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. An adaptive current compensation control circuit is applied to a switching power supply, wherein the switching power supply comprises a main power switch tube and an excitation inductor. It is characterized in that The control circuit comprises, A sampling circuit, used for sampling the current information of the excitation inductor to obtain a current sampling signal; A compensation circuit receives the current sampling signal and samples and holds the current sampling signal within a preset time to obtain a compensation signal, wherein the preset time length is set according to a line voltage delay parameter in the circuit; A comparison circuit receives the current sampling signal and a reference signal to obtain a comparison signal, wherein the compensation signal compensates the current sampling signal or the reference signal; The driving circuit generates a switch control signal according to the comparison signal to control the switching action of the main power switch tube.

2. The adaptive current compensation control circuit according to claim 1, It is characterized in that The delay parameter includes at least one of a delay time of a sampling circuit, a delay time of a comparison circuit, and a delay time of a driving circuit.

3. The adaptive current compensation control circuit according to claim 2, It is characterized in that The preset time length is set to be the sum of at least two of the delay time of the sampling circuit, the delay time of the comparison circuit, and the delay time of the driving circuit.

4. The adaptive current compensation control circuit according to claim 1, It is characterized in that The preset time is set within the conduction time period of the main power switch tube.

5. The adaptive current compensation control circuit according to claim 1, It is characterized in that The sampling circuit includes a switch tube. The switch tube is arranged in a mirror image with the main power switch tube, and the current sampling signal is obtained by sampling the current information of the switch tube.

6. The adaptive current compensation control circuit according to claim 1, It is characterized in that The sampling circuit includes a sampling resistor, The sampling resistor is connected in series with the main power switch tube, and the current sampling signal is obtained by sampling the current information of the sampling resistor.

7. The adaptive current compensation control circuit according to claim 5 or 6, It is characterized in that The compensation signal is superimposed on the current sampling signal to obtain a superimposed signal, The comparison circuit compares the superimposed signal and the reference signal to obtain the comparison signal.

8. The adaptive current compensation control circuit according to claim 1, It is characterized in that The compensation signal is superimposed on the reference signal to obtain a superimposed signal, The comparison circuit compares the superimposed signal and the circuit sampling signal to obtain the comparison signal.

9. The adaptive current compensation control circuit according to claim 1, It is characterized in that The compensation circuit includes a filter circuit and a holding capacitor. The current sampling signal is transmitted to the filter circuit through the first switch circuit to obtain a filter signal. The filtered signal is transmitted to the holding circuit through the second switch circuit to obtain a sample holding signal, and the sample holding signal is output as a compensation signal; The first switch circuit and the second switch circuit are controlled to be turned on or off according to the switch control signal and a preset time.

10. The adaptive current compensation control circuit according to claim 9, It is characterized in that The compensation circuit comprises: When the second switch circuit is turned on at the rising edge of the switch control signal representing the turning on of the main power switch tube, the compensation signal is transmitted to the comparison circuit in the current switching cycle. When the second switch circuit is turned on at the falling edge of the switch control signal representing the turning on of the main power switch tube, the compensation signal is sampled and held in the current switching cycle, and the compensation signal is transmitted to the comparison circuit in the next switching cycle.

11. The adaptive current compensation control circuit according to claim 9, It is characterized in that The compensation circuit also includes a proportional adjustment circuit. The proportional adjustment circuit is connected to the output end of the holding capacitor to perform proportional conversion on the sampled and held signal, and output the proportionally converted signal as a compensation signal.

12. An adaptive current compensation control method, applied to a switching power supply, the switching power supply comprising a main power switch tube and an excitation inductor, It is characterized in that The following steps are involved: Sampling the current information of the excitation inductor to obtain a current sampling signal; receiving the current sampling signal, and sampling and holding the current sampling signal within a preset time to obtain a compensation signal, receiving the current sampling signal and a reference signal to obtain a comparison signal, wherein the compensation signal compensates the current sampling signal or the reference signal; Generate a switch control signal according to the comparison signal to control the switching action of the main power switch tube; The preset time length is set to be the sum of at least two of the delay time of the sampling circuit, the delay time of the comparison circuit, and the delay time of the driving circuit.

13. The adaptive current compensation control method according to claim 12, It is characterized in that The preset time is set within the conduction time period of the main power switch tube.

14. The adaptive current compensation control method according to claim 12, It is characterized in that The current sampling signal is transmitted to the filter circuit through the first switch circuit to obtain a filter signal. The filtered signal is transmitted to the holding circuit through the second switch circuit to obtain a sample holding signal, and the sample holding signal is output as a compensation signal; The first switch circuit and the second switch circuit are controlled to be turned on or off according to the switch control signal and a preset time.

15. The adaptive current compensation control method according to claim 12, It is characterized in that The sample-and-hold signal is proportionally transformed, and the proportionally transformed signal is output as a compensation signal.

16. A switching power supply, comprising a main power switch tube and an excitation inductor, It is characterized in that It also includes the adaptive current compensation control circuit according to any one of claims 1 to 11, The current compensation control circuit is used to control the switching state of the main power switch tube to control the output voltage of the switching power supply to a desired value.

Images