Slope compensation circuit for improving transmission power in switching power supply

Abstract

The invention discloses a slope compensation circuit of a switching power supply. The slope compensation circuit comprises a current source module, a slope signal generation module, a signal superposition module and a reference level compensation module, the current source module comprises a first current mirror unit and a second current mirror unit, a first current source is arranged on the first current mirror unit, and the first current mirror unit is used for mirroring current of the first current source to the second current mirror unit and outputting the current; the slope signal generation module generates a slope compensation current signal under the control of the enable signal; the signal superposition module superposes the slope compensation current signal and the sampling current of the switching power supply so as to generate a slope compensation control signal; the reference level compensation module performs selectable multi-gear compensation on a reference level so as to generate a compensated reference level; and determining the peak current of the switching power supply based on the slope compensation control signal and the compensated reference level.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a slope compensation circuit for improving transmission power in a switching power supply. Background Art

[0002] The current-controlled switching power supply introduces current feedback on the basis of the traditional PWM voltage control method, and improves the original single voltage closed-loop control to voltage and current dual closed-loop control to improve the performance of the power supply. There are two types of current control: peak current control and average current control. The peak current control method is simple, but in the Buck series circuit of peak current control, since the change of feedback current cannot fully reflect the change of load current, when the duty cycle D>50%, the power supply cannot work stably, which limits the application of the peak current control method and must be improved by slope compensation.

[0003] The main function of the slope compensation circuit in the switching power supply is to generate a slope compensation signal to suppress the open-loop instability and subharmonic oscillation phenomenon that occurs when the duty cycle is greater than 50%. Figure 1 As shown, a slope compensation signal V_ is generated from the beginning of each cycle. SLOPE , and the slope compensation signal V_ SLOPE Superimposed on the reference level V_ C The uncompensated current sampling signal V_ SNS Relative to the compensated current sampling signal V_ SNS1 The amplitude is reduced by ΔV_ SNS The slope compensation method in the prior art has obvious defects, that is, the current technology has a large amount of reference level V_ C Under the condition that the current remains unchanged, adding slope compensation will lead to a decrease in the amplitude of the inductor current sampling signal, and the corresponding peak current of the switch tube will become smaller, so the maximum transmittable power will become smaller.

[0004] It can be seen that a new slope compensation circuit of a switching power supply is needed in the prior art to solve the problem of too small peak current when the switching power supply performs slope compensation. Summary of the invention

[0005] The technical purpose to be achieved by the present invention is to provide a slope compensation circuit for a switching power supply. The slope compensation circuit can suppress subharmonic oscillation when the duty cycle is greater than 50%, while reducing the amplitude of the ramp signal as much as possible, so that the sampling signal can reach a larger amplitude, thereby increasing the maximum power that the switching power supply can transmit.

[0006] Based on the above technical purpose, the present invention provides a slope compensation circuit of a switching power supply, wherein the slope compensation circuit includes a current source module, a ramp signal generating module, a signal superposition module and a reference level compensation module;

[0007] The current source module includes a first current mirror unit and a second current mirror unit, the first current source is arranged in the first current mirror unit, and the first current mirror unit mirrors the current of the first current source to the second current mirror unit and outputs it;

[0008] The ramp signal generating module generates a ramp compensation current signal under the control of the enable signal;

[0009] The signal superposition module superimposes the slope compensation current signal and the sampled current of the switching power supply to generate a slope compensation control signal;

[0010] The reference level compensation module compensates the reference level by a plurality of selectable levels to generate a compensated reference level;

[0011] The peak current of the switching power supply is determined based on the slope compensation control signal and the compensated reference level.

[0012] In one embodiment, the ramp signal generating module includes a first switch tube, a first capacitor, a buffer amplifier, a second switch tube and a first resistor; the slope of the ramp compensation voltage is determined by the first capacitor and the first current source.

[0013] In one embodiment, the duty cycle of the PWM control signal is set to 45%.

[0014] In one embodiment, the signal superposition module includes a third current mirror unit, a first side of the third current mirror unit inputs the slope compensation current generated by the ramp signal generating module, and a second side of the third current mirror unit outputs a slope compensation control signal.

[0015] In one embodiment, the reference level compensation module includes a compensation voltage generation module composed of a plurality of resistors and a plurality of switches, and compensation for different voltage values ​​of the reference level is achieved by controlling the switching states of the plurality of switches.

[0016] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 It is a signal waveform and timing diagram of a slope compensation circuit in the prior art;

[0019] Figure 2 It is a schematic diagram of the structural framework of the slope compensation circuit of the present invention;

[0020] Figure 3 is a schematic diagram of a slope compensation circuit of the present invention;

[0021] Figure 4 It is a schematic diagram of the signal waveform and timing of the slope compensation circuit of the present invention;

[0022] Figure 5 It is a schematic diagram of waveform comparison of the reference signal before and after compensation of the present invention. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings.

[0024] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present invention necessarily has the first element, component, region, layer or part.

[0025] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0026] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0027] Example 1

[0028] like Figure 2-3 As shown, the slope compensation circuit of the present invention includes a current source module 100 , a ramp signal generating module 200 , a signal superposition module 300 and a reference level compensation module 400 .

[0029] The current source module 100 shown includes a first current mirror unit and a second current mirror unit. The first current source is disposed in the first current mirror unit. The first current mirror unit mirrors the current I1 of the first current source to the second current mirror unit and outputs the mirrored current.

[0030] The ramp signal generating module 200 includes: a first switch tube 201, a first capacitor 202, a buffer amplifier 203, a second switch tube 204, and a first resistor 205. The enable control signal EN is input to the gate of the first switch tube 201, the first switch tube 201 is an NMOS tube, the drain of the first switch tube 201, the first end of the first capacitor 202, and the current I1 output by the current source module 100 are all connected to the in-phase input end of the buffer amplifier 203, and the source of the first switch tube 201 and the second end of the first capacitor 202 are grounded. The output end of the buffer amplifier 203 is connected to the gate of the second switch tube 204, the second switch tube 204 is an NMOS tube, the source of the second switch tube 204 is connected to the first end of the first resistor 205, and the inverting input end of the buffer amplifier 203 is also connected to the first end of the first resistor 205. The second end of the first resistor 205 is grounded. Through the action of the buffer amplifier 203 and the second switch tube 204, the voltage at the first end of the first resistor 205 is equal to the slope compensation voltage V_ SLOPE , so the current on the first resistor 205 is equal to V_ SLOPE / R1, where R1 is the resistance value of the first resistor 205.

[0031] The enable control signal EN can determine the start time of the slope compensation, and is set to a duty cycle less than or equal to 50% to ensure sufficient slope compensation. In this embodiment, the duty cycle of the PWM control signal is set to 45%.

[0032] The signal superposition module 300 includes a third current mirror unit, a first side of which inputs the slope compensation current I_ generated by the ramp signal generating module 200. SLOPE The second side of the third current mirror unit is provided with a resistor, and the sampling current I_ of the switching power supply is input from the second side of the third current mirror unit. SNS . And generate a slope compensation control signal V_ on the second side of the third current mirror unit. SIGMA .

[0033] The reference level compensation module 400 includes a third switch tube 401, which is connected in parallel with the second current mirror unit of the current source module 100, and mirrors the current I1 of the first current source to the on-current of the third switch tube 401. The third switch tube 401 is connected to a compensation voltage generation module 402 composed of multiple resistors and multiple switches, and one end of the compensation voltage generation module 402 is connected to the reference level V_ C , the other end outputs the compensated reference level V_ C_OFFSET The compensation voltage generating module 402 controls the switch states of the plurality of switches to realize the reference level V_C The compensation of different voltage values ​​​​of the reference level V_ C_OFFSET .

[0034] In the present invention, the compensation voltage generation module 402 composed of multiple resistors and multiple switches is only one implementation method of the present invention to achieve different compensation values. Without departing from the general idea of ​​the present invention, different compensation voltages can also be achieved by superposition of operational amplifiers; or different compensation voltages can be achieved by using DAC and superimposed on the reference level; at the same time, there are many implementation methods for the resistor array. In order to reduce the number of switches, the ratio of the resistance value can be binary, such as R, 2R, 4R...; the compensation resistor R can also be set to a fixed value, while the current I1 is set to be adjustable, so that the amplitude of the compensation voltage I1*R can also be adjusted.

[0035] like Figure 4-5 As shown, the slope compensation control signal V_ SIGMA is the slope compensation voltage V_ SLOPE With the switching power supply sampling voltage V_ SNS The voltage signal after the superposition of the two, m c is the slope compensation voltage V_ SLOPE The slope, m a is the switching power supply sampling voltage V_ SNS The slope of m1 is the slope compensation control signal V_ SIGMA The slope of m1 is m c +m a Since VC_offset=VC+Ic*R, R can be selected according to different switches, namely, one of RC0, RC0+RC1, ..., RC0+RC1+...RCN; if Ic*R=ΔVsns, the amplitude of the sampling current is completely unaffected by the addition of the slope compensation signal.

[0036] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A slope compensation circuit for a switching power supply, characterized in that: The slope compensation circuit includes a current source module, a ramp signal generation module, a signal superposition module and a reference level compensation module; The current source module includes a first current mirror unit and a second current mirror unit, the first current source is arranged in the first current mirror unit, and the first current mirror unit mirrors the current of the first current source to the second current mirror unit and outputs it; The ramp signal generating module generates a ramp compensation current signal under the control of the enable signal; The signal superposition module superimposes the slope compensation current signal and the sampled current of the switching power supply to generate a slope compensation control signal; The reference level compensation module compensates the reference level by a plurality of selectable levels to generate a compensated reference level; The peak current of the switching power supply is determined based on the slope compensation control signal and the compensated reference level.

2. The slope compensation circuit of the switching power supply according to claim 1, characterized in that: The ramp signal generating module includes a first switch tube, a first capacitor, a buffer amplifier, a second switch tube and a first resistor; the slope of the ramp compensation voltage is determined by the first capacitor and the first current source.

3. The slope compensation circuit of the switching power supply according to claim 1, characterized in that: The duty cycle of the PWM control signal is set to 45%.

4. The slope compensation circuit of the switching power supply according to claim 1, characterized in that: The signal superposition module comprises a third current mirror unit, a first side of the third current mirror unit inputs a slope compensation current generated by the ramp signal generating module, and a second side of the third current mirror unit outputs a slope compensation control signal.

5. The slope compensation circuit of the switching power supply according to claim 1, characterized in that: The reference level compensation module includes a compensation voltage generation module composed of a plurality of resistors and a plurality of switches, and compensation for different voltage values ​​of the reference level is achieved by controlling the switch states of the plurality of switches.

6. A switching power supply, characterized in that: The switching power supply comprises the slope compensation circuit as claimed in any one of claims 1-5.

7. An integrated circuit structure, characterized in that: The integrated circuit structure comprises the slope compensation circuit as claimed in any one of claims 1-5.

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