Ramp compensation circuit for increasing transmission power in switching power supplies

Abstract

The application discloses a slope compensation circuit of a switching power supply, which 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 in the first current mirror unit, the first current mirror unit mirrors the current of the first current source to the second current mirror unit and outputs; the slope signal generation module generates a slope compensation current signal under the control of an enable signal; the signal superposition module superposes the slope compensation current signal and a sampling current of the switching power supply to generate a slope compensation control signal; the reference level compensation module compensates the reference level in multiple selectable gears to generate a compensated reference level; and the peak current of the switching power supply is determined 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] Current-controlled switching power supplies integrate current feedback into traditional PWM voltage control, improving performance by shifting from single-loop voltage control to dual-loop voltage and current control. Current control can be implemented in two ways: peak current control and average current control. Peak current control is simple, but in peak current-controlled Buck series circuits, changes in feedback current cannot fully reflect changes in load current. Consequently, when the duty cycle D exceeds 50%, the power supply becomes unstable. This limits the application of peak current control and necessitates 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 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 On the other hand, 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 significant disadvantage in the reference level V_ C Under the condition that the current remains unchanged, adding slope compensation will cause the amplitude of the inductor current sampling signal to decrease, and the corresponding peak current of the switching tube will become smaller, so the maximum power that can be transmitted will become smaller.

[0004] It can be seen from the above 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 objective to be achieved by the present invention is to provide a slope compensation circuit for a switching power supply. The slope compensation circuit satisfies the requirements of suppressing subharmonic oscillation when the duty cycle is greater than 50%, while minimizing the amplitude of the ramp signal, 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 objectives, the present invention provides a slope compensation circuit for a switching power supply, wherein the slope compensation circuit includes a current source module, a ramp signal generation 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 provided in the first current mirror unit. The first current mirror unit mirrors the current of the first current source to the second current mirror unit and outputs the mirrored current.

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

[0009] The signal superposition module superposes 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 in 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 generation 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 multiple resistors and multiple switches, and compensation for different voltage values ​​of the reference level is achieved by controlling the switching states of the multiple switches.

[0016] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained through 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 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 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 comparing the waveforms 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 being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there can be no intervening elements or layers. It should be understood that while the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or portion from another. Thus, without departing from the teachings of the present invention, a first element, component, region, layer, or portion discussed below may be represented as a second element, component, region, layer, or portion. Furthermore, when a second element, component, region, layer, or portion is discussed, it does not necessarily mean that the first element, component, region, layer, or portion is present in the present invention.

[0025] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the drawings is flipped, then the elements or features described as "under the other elements" or "under it" or "under it" will be oriented as "on" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in 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 limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" 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 includes a first current mirror unit and a second current mirror unit. The first current source is provided 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 generation module 200 includes: a first switching transistor 201, a first capacitor 202, a buffer amplifier 203, a second switching transistor 204, and a first resistor 205. An enable control signal EN is input to the gate of the first switching transistor 201, which is an NMOS transistor. The drain of the first switching transistor 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 non-inverting input of the buffer amplifier 203. The source of the first switching transistor 201 and the second end of the first capacitor 202 are grounded. The output of the buffer amplifier 203 is connected to the gate of the second switching transistor 204, which is an NMOS transistor. The source of the second switching transistor 204 is connected to the first end of the first resistor 205. The inverting input 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 switching transistor 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 of the first resistor 205.

[0031] The enable control signal EN can determine the start time of slope compensation, and is set to a duty cycle of 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 conduction 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. 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 switching states of the plurality of switches to realize the reference level V_C Compensation of different voltage values, thereby forming different compensated reference levels V_ C_OFFSET .

[0034] In the present invention, the use of compensation voltage generation module 402, comprised of multiple resistors and multiple switches, is merely one embodiment of the present invention for achieving different compensation values. Without departing from the overall concept of the present invention, different compensation voltages can also be achieved by stacking op amps; or by using a DAC to achieve different compensation voltages and superimpose them on a reference voltage level. Furthermore, resistor arrays can be implemented in a variety of ways. To reduce the number of switches, the resistance ratio can be binary, such as R, 2R, 4R, etc. Alternatively, the compensation resistor R can be set to a fixed value while the current I1 is set to be adjustable, thereby also adjusting the compensation voltage amplitude I1*R.

[0035] like Figure 4-5 As shown, the slope compensation control signal V_ SIGMA is the slope compensation voltage V_ SLOPE And 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=m c +m a Since VC_offset = VC + Ic*R, R can be selected according to different switches, that is, one of RC0, RC0+RC1, ..., RC0+RC1+ ...RCN; if Ic*R = ΔVsns, then the amplitude of the sampled 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above 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 provided in the first current mirror unit. The first current mirror unit mirrors the current of the first current source to the second current mirror unit. The second current mirror unit outputs the mirrored current to the ramp signal generation module. The ramp signal generating 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 sampled current of the switching power supply to generate a slope compensation control signal; The reference level compensation module compensates the reference level in 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, wherein: 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, wherein: The signal superposition module includes a third current mirror unit. The first side of the third current mirror unit inputs the slope compensation current generated by the ramp signal generation module, and the second side of the third current mirror unit outputs a slope compensation control signal.

4. The slope compensation circuit of the switching power supply according to claim 1, wherein: The reference level compensation module includes a compensation voltage generation module composed of multiple resistors and multiple switches, and compensates for different voltage values ​​of the reference level by controlling the switching states of the multiple switches.

5. A switching power supply, characterized in that: The switching power supply includes the slope compensation circuit according to any one of claims 1 to 4.

6. An integrated circuit structure, characterized in that: The integrated circuit structure includes the slope compensation circuit according to any one of claims 1 to 4.

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