Slope compensation circuit and slope compensation method thereof

Abstract

The invention discloses a slope compensation circuit and a slope compensation method thereof, the slope compensation circuit is applied to a BOOST switching power supply, the BOOST switching power supply comprises a control unit and a power unit, the control unit outputs a signal OSC to the slope compensation circuit to control starting and ending of slope compensation, and the power unit outputs the signal OSC to the slope compensation circuit to control starting and ending of slope compensation. Meanwhile, the control unit outputs a signal DRV to the power unit to control on and off of a power switch; the power unit outputs a feedback signal FB to the control unit and is used for adjusting the output voltage; and the slope compensation circuit outputs a slope current I SLOPE to a sampling resistor of the power unit. According to the invention, the real-time voltage difference value of the output VOUT and the input VI N of the BOOST switching power supply is taken as a reference, the generated reference current for slope compensation automatically follows the change of the VOUT and the VI N, and the maximum required slope compensation amount does not need to be determined according to the maximum output voltage VOUT value and the minimum input voltage VI N value.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a slope compensation circuit and a slope compensation method thereof. Background Art

[0002] In switching power supplies, the current-mode PWM switch control mode is widely used because of its simple loop design and fast response speed. However, the biggest problem with switching power supplies using current-mode PWM switch control is that when the duty cycle is greater than 50%, there is subharmonic interference, which will cause unstable chip operation. Therefore, a slope compensation circuit needs to be introduced to eliminate subharmonic interference. For traditional slope compensation circuit, after the system parameters are set, its slope compensation amount is also determined. Therefore, in order to meet various application conditions, especially to work stably under various input voltages VIN and different output voltages VOUT, the slope compensation amount needs to be calculated according to the worst case. The slope compensation should be greater than or equal to half of the inductor current drop slope. For BOOST switching power supply, the inductor current drop slope is equal to (VOUT-VIN) / L. Therefore, the traditional slope compensation needs to be determined according to the maximum output voltage VOUT value and the minimum input voltage VIN value. This will result in a large slope compensation amount under all application conditions. In addition, the initial value of the traditional slope compensation at the beginning of compensation is not zero, which will also lead to an increase in the absolute value of the compensation voltage at the compensation cutoff point. The above problems will cause the following two problems. First, the larger the amount of slope compensation, the closer the current control mode will be to the voltage mode, thereby gradually losing the fast response advantage of the current mode itself; second, because the component of the slope compensation superimposed on the current sampling detection voltage is too large, the switch current limit value will become very large, which will put the system at risk. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a slope compensation circuit and a slope compensation method thereof.

[0004] In order to achieve the above object, the present invention provides a slope compensation circuit, which is applied to a BOOST switching power supply. The BOOST switching power supply includes a control unit and a power unit. The control unit outputs a signal OSC to the slope compensation circuit to control the start and end of the slope compensation. At the same time, the control unit outputs a signal DRV to the power unit to control the on and off of the power switch; the power unit outputs a feedback signal FB to the control unit for adjusting the output voltage;

[0005] The slope compensation circuit outputs a slope current I SLOPE To the sampling resistor of the power unit, the ramp current is converted into a ramp voltage V SLOPE And output to the control unit.

[0006] Preferably, the slope compensation circuit includes: a compensation reference current generating module, a slope current generating module, a zeroing current generating module, and an output module; the corresponding ends of the compensation reference current generating module are electrically connected to the corresponding ends of the slope current generating module and the zeroing current generating module respectively, and the corresponding ends of the output module are also electrically connected to the other corresponding ends of the slope current generating module and the zeroing current generating module.

[0007] Preferably, the compensation reference current generating module comprises: a current source I1, a PMOS transistor P1 and a PMOS transistor P2, an NMOS transistor N1, an NMOS transistor N2 and an NMOS transistor N3, and a resistor R1, wherein a first end of the current source I1 is grounded, a second end is respectively connected to a source of the NMOS transistor N1 and a gate of the PMOS transistor P1, a drain and a gate of the NMOS transistor N1 are connected to an input voltage VIN, a source of the PMOS transistor P1 is connected to a first end of the resistor R1, a drain of the PMOS transistor P1 is respectively connected to a drain and a gate of the NMOS transistor N2 and a gate of the NMOS transistor N3, a second end of the resistor R1 is connected to an output voltage VOUT, sources of the NMOS transistor N2 and the NMOS transistor N3 are both grounded, and a drain of the NMOS transistor N3 is connected to a drain and a gate of the PMOS transistor P2;

[0008] Preferably, the compensation reference current generating module generates a compensation reference current according to the real-time voltage difference between the output VOUT and the input VIN of the switching power supply. The reference current is mirrored through the PMOS transistor P2 to the ramp current generating module and mirrored to the zero current generating module.

[0009] Preferably, the ramp current generating module comprises: a PMOS transistor P3 and a PMOS transistor P5, an NMOS transistor N4, an NMOS transistor N5 and an NMOS transistor N6, a resistor R2, a capacitor C1, and a control signal OSC; the gate of the PMOS transistor P3 is connected to the gate and the drain of the PMOS transistor P2 to mirror the slope compensation reference current of the PMOS transistor P2, the drain of the PMOS transistor P3 is respectively connected to the drain and the gate of the NMOS transistor N4 and the gate of the NMOS transistor N5, the source of the NMOS transistor N4 is connected to the positive electrode of the capacitor C1 and the drain of the NMOS transistor N6, the negative electrode of the capacitor C1 and the source of the NMOS transistor N6 are grounded, the gate of the NMOS transistor N6 is connected to the control signal OSC, the source of the NMOS transistor N5 is connected to the positive electrode of the resistor R2, the negative electrode of the resistor R2 is grounded, and the drain of the NMOS transistor N5 is connected to the drain and the gate of the PMOS transistor P5;

[0010] Preferably, in the ramp current generating module, when the control signal OSC is high, the NMOS transistor N6 is turned on, and the point C at the NMOS transistor N6 is pulled to the ground, and the voltage is 0V. At this time, the voltage at the point D at the NMOS transistor N4 and the voltage at the point E at the NMOS transistor N5 also remain unchanged, and the current flowing through the PMOS transistor P5 remains fixed. When the control signal OSC becomes low, the NMOS transistor N6 is turned off, and the slope compensation starts. The mirror current source of the PMOS transistor P3 flows through the NMOS transistor N4 to charge the capacitor C1, and the voltage at the point C increases linearly, and the voltages at the points D and E also increase linearly, and the current flowing through the PMOS transistor P5 and the PMOS transistor P6 also increases linearly.

[0011] Preferably, the zero-elimination current generating module comprises: a PMOS transistor P4 and a PMOS transistor P6, an NMOS transistor N7 and an NMOS transistor N8, and a resistor R3; the gate of the PMOS transistor P4 is connected to the gate and the drain of the PMOS transistor P2 to mirror the reference current of the PMOS transistor P2, the drain of the PMOS transistor P4 is respectively connected to the drain and the gate of the NMOS transistor N7, and the gate of the NMOS transistor N8, the source of the NMOS transistor N7 is grounded, the source of the NMOS transistor N8 is connected to the positive electrode of the resistor R3, the negative electrode of the resistor R3 is grounded, the drain of the NMOS transistor N8 is connected to the drain of the PMOS transistor P6, the gate of the PMOS transistor P6 is respectively connected to the gate and the drain of the PMOS transistor P5 to mirror the ramp current of P5;

[0012] Preferably, in the zeroing current generating module, since the voltage at the point F of the NMOS transistor N7 and the voltage at the point G of the NMOS transistor N8 are also fixed, the current flowing through the NMOS transistor N8 is a fixed value, and the PMOS transistor P6 mirrors the current of the PMOS transistor P5. Before the slope compensation signal OSC is effective, the current of the PMOS transistor P6 is also a fixed value. Therefore, by setting the same transistor size and the same resistance value of the resistor R2 and the resistor R3, the current of the NMOS transistor N8 and the current of the PMOS transistor P6 can be equal. In this way, at the starting point of each compensation cycle, the current I output by the zeroing current generating module is SLOPE is 0.

[0013] Preferably, the output module includes: a resistor R4, and an output ramp current I SLOPE and the ramp voltage V SLOPE One end of the resistor R4 is connected to the drain of the PMOS transistor P6 and the NMOS transistor N6, and the other end outputs I SLOPE The current sampling resistor of the power unit; at the beginning of each compensation cycle, I SLOPE =I P6 -IN8 =0, after each cycle compensation starts, I P6 The current increases linearly, while I N8 Always fixed, so I SLOPE Linear increase, I SLOPE The current will flow through the resistor R4 and then to the sampling resistor R CS to the ground, so V SLOPE It will also increase linearly.

[0014] The present invention also provides a slope compensation method for a BOOST switching power supply, comprising the following steps:

[0015] Step a: using a compensation reference current generating module to generate a compensation reference current according to the real-time voltage difference between the output voltage VOUT and the input voltage VIN of the BOOST switching power supply;

[0016] Step b: mirroring the generated reference current and providing it to the ramp current generating module and the zeroing current generating module respectively;

[0017] Step c: Processing the generated compensation reference current through a ramp current generating module to generate a ramp current that varies with time;

[0018] Step c: Generate a current that is equal to the reference current but opposite in direction through the zero current generation module to reduce the slope compensation current I SLOPE The initial value of is set to zero;

[0019] Step d: synthesize the generated slope current and the generated zeroing current to obtain the final slope compensation current I SLOPE ;

[0020] Step e: The synthesized slope compensation current I SLOPE Converted into a slope compensation voltage V by the output module SLOPE ;

[0021] Step f: Set the slope compensation voltage V SLOPE The output is sent to the control unit of the BOOST switching power supply and is used to adjust the output of the switching power supply to achieve slope compensation and optimize the performance of the switching power supply.

[0022] The technical solution of the present invention has the following beneficial effects:

[0023] The compensation reference current generating module of the present invention generates a compensation reference current according to the real-time voltage difference between the output VOUT and the input VIN of the switching power supply, and gives it to the ramp current generating module and the zeroing current generating module respectively after being mirrored. Under the joint action of the ramp current generating module and the zeroing current generating module, a current difference is generated, and finally the zeroing current generating module outputs the current difference, which is the slope compensation current value I SLOPE , I SLOPE The voltage V generated at the positive end of the output module resistor R4 SLOPE The output is sent to the control unit of the BOOST switching power supply to achieve the purpose of slope compensation.

[0024] The present invention uses the real-time voltage difference between the output VOUT and the input VIN of the BOOST switching power supply as a reference, and the generated reference current of the slope compensation automatically follows the changes of VOUT and VIN. The slope compensation does not need to consider the changes of VOUT and VIN, so it is not necessary to determine the maximum required slope compensation amount according to the maximum output voltage VOUT value and the minimum input voltage VIN value. At the same time, due to the effect of the zero current generation module, the initial value of the slope compensation is made zero. The two work together to greatly reduce the amount of slope compensation required in various application occasions, avoid the current mode switching power supply from evolving into a voltage mode switching power supply, maintain the advantage of fast response of the current mode switching power supply itself, and greatly reduce the influence of the slope compensation on the switch current limit value, so as to avoid the current limit value becoming very large and causing the system to face risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a control module diagram of the present invention;

[0026] Figure 2 This is a control diagram of the slope compensation circuit of the present invention;

[0027] Figure 3 It is a circuit schematic diagram of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] Reference Figures 1 to 3The present invention provides a slope compensation circuit 10, which is applied to a BOOST switching power supply. The BOOST switching power supply includes a control unit 20 and a power unit 30. The control unit 20 outputs a signal OSC to the slope compensation circuit 10 to control the start and end of the slope compensation. At the same time, the control unit 20 outputs a signal DRV to the power unit 30 to control the on and off of the power switch, thereby achieving precise control of the BOOST switching power supply. The power unit 30 outputs a feedback signal FB to the control unit for adjusting the output voltage, directly controlling the power conversion process of the power supply, ensuring the stability of the output voltage, and providing feedback to achieve closed-loop control. The slope compensation circuit 10 outputs a slope current I SLOPE To the sampling resistor of the power unit, the ramp current is converted into a ramp voltage V SLOPE And output to the control unit 20.

[0030] Furthermore, the slope compensation circuit 10 includes: a compensation reference current generating module 101, a slope current generating module 102, a zeroing current generating module 103, and an output module 104; the corresponding end of the compensation reference current generating module 101 is electrically connected to the corresponding end of the slope current generating module 102 and the zeroing current generating module 103, respectively, and the corresponding end of the output module 104 is also electrically connected to the other corresponding end of the slope current generating module 102 and the zeroing current generating module 103; the compensation reference current generating module 101 dynamically generates a compensation reference current according to the real-time voltage difference between the output VOUT and the input VIN of the BOOST switching power supply, ensuring that the slope compensation current can automatically adapt to the real-time working conditions of the power supply and provide a precise current control basis; the slope current generating module 102: receives the compensation reference current, and generates a slope current that varies with time according to the control signal. Generate a control signal that simulates the slope of the inductor current, which is used to eliminate subharmonic interference in current mode control. The zeroing current generating module 103 generates a current which is equal to the reference current in magnitude but opposite in direction, so as to reduce the slope compensation current I SLOPE The initial value of is set to zero. Output module 104: outputs the ramp current to the sampling resistor of the power unit 30, and converts the ramp current into a ramp voltage V SLOPE The output is sent to the control unit 20 to adjust the output of the switching power supply, while ensuring that the slope compensation current can be accurately reflected in the control of the power unit.

[0031] Furthermore, the compensation reference current generating module 101 includes: a current source I1, a PMOS transistor P1 and a PMOS transistor P2, an NMOS transistor N1, an NMOS transistor N2 and an NMOS transistor N3, and a resistor R1, wherein a first end of the current source I1 is grounded, and a second end is respectively connected to a source of the NMOS transistor N1 and a gate of the PMOS transistor P1, a drain and a gate of the NMOS transistor N1 are connected to an input voltage VIN, a source of the PMOS transistor P1 is connected to a first end of the resistor R1, and a drain of the PMOS transistor P1 is respectively connected to the NMOS transistors The drain and gate of N2 and the gate of NMOS transistor N3, the second end of the resistor R1 is connected to the output voltage VOUT, the sources of the NMOS transistor N2 and the NMOS transistor N3 are both grounded, and the drain of the NMOS transistor N3 is connected to the drain and gate of the PMOS transistor P2; the compensation reference current generating module generates a compensation reference current according to the real-time voltage difference between the output VOUT and the input VIN of the switching power supply, and the reference current is mirrored through the PMOS transistor P2 to the ramp current generating module, and another current is mirrored to the zeroing current generating module.

[0032] Further, the slope current generating module 102 includes: PMOS transistors P3 and PMOS transistors P5, NMOS transistors N4, NMOS transistors N5 and NMOS transistors N6, resistor R2, capacitor C1, and control signal OSC; the gate of the PMOS transistor P3 is connected to the gate and drain of the PMOS transistor P2 to mirror the slope compensation reference current of the PMOS transistor P2, the drain of the PMOS transistor P3 is respectively connected to the drain and gate of the NMOS transistor N4 and the gate of the NMOS transistor N5, the source of the NMOS transistor N4 is connected to the positive electrode of the capacitor C1 and the drain of the NMOS transistor N6, the negative electrode of the capacitor C1 and the source of the NMOS transistor N6 are grounded, the gate of the NMOS transistor N6 is connected to the control signal OSC, the source of the NMOS transistor N5 is connected to the positive electrode of the capacitor C1 and the drain of the NMOS transistor N6, the negative electrode of the capacitor C1 and the source of the NMOS transistor N6 are grounded, the gate of the NMOS transistor N6 is connected to the control signal OSC, and the source of the NMOS transistor N5 is connected to the positive electrode of the capacitor C1 and the drain of the NMOS transistor N6. The positive electrode of the resistor R2 is connected, the negative electrode of the resistor R2 is grounded, and the drain of the NMOS transistor N5 is connected to the drain and gate of the PMOS transistor P5; the slope current generating module, when the control signal OSC is high, the NMOS transistor N6 is turned on, the point C at the NMOS transistor N6 is pulled to the ground, and the voltage is 0V. At this time, the voltage at the point D at the NMOS transistor N4 and the voltage at the point E at the NMOS transistor N5 also remain unchanged, and the current flowing through the PMOS transistor P5 remains fixed. When the control signal OSC becomes low, the NMOS transistor N6 is turned off, and the slope compensation starts. The mirror current source of the PMOS transistor P3 flows through the NMOS transistor N4 to charge the capacitor C1, the voltage at the point C increases linearly, and the voltages at the points D and E also increase linearly, and the currents flowing through the PMOS transistors P5 and PMOS transistors P6 also increase linearly.

[0033] Furthermore, the zeroing current generating module 103 includes: PMOS transistors P4 and PMOS transistors P6, NMOS transistors N7 and NMOS transistors N8, and resistor R3; the gate of the PMOS transistor P4 is connected to the gate and drain of the PMOS transistor P2 to mirror the reference current of the PMOS transistor P2, the drain of the PMOS transistor P4 is respectively connected to the drain and gate of the NMOS transistor N7, and the gate of the NMOS transistor N8, the source of the NMOS transistor N7 is grounded, the source of the NMOS transistor N8 is connected to the positive electrode of the resistor R3, the negative electrode of the resistor R3 is grounded, the drain of the NMOS transistor N8 is connected to the drain of the PMOS transistor P6, and the gate of the PMOS transistor P6 is respectively connected to the gate and drain of the PMOS transistor P5 to mirror the ramp current of P5. In the zeroing current generating module, since the voltage at the point F of the NMOS transistor N7 and the voltage at the point G of the NMOS transistor N8 are also fixed, the current flowing through the NMOS transistor N8 is a fixed value, and the PMOS transistor P6 mirrors the current of the PMOS transistor P5. Before the slope compensation signal OSC is effective, the current of the PMOS transistor P6 is also a fixed value. Therefore, by setting the same transistor size and the same resistance value of the resistor R2 and the resistor R3, the current of the NMOS transistor N8 and the current of the PMOS transistor P6 can be equal. In this way, at the starting point of each compensation cycle, the current I output by the zeroing current generating module is SLOPE is 0.

[0034] Furthermore, the output module 104 includes: a resistor R4, and an output ramp current I SLOPE and the ramp voltage V SLOPE One end of the resistor R4 is connected to the drain of the PMOS transistor P6 and the NMOS transistor N6, and the other end outputs I SLOPE The current sampling resistor of the power unit; at the beginning of each compensation cycle, I SLOPE =I P6 -I N8 =0, after each cycle compensation starts, I P6 The current increases linearly, while I N8 Always fixed, so I SLOPE Linear increase, I SLOPE The current will flow through the resistor R4 and then to the sampling resistor R CS to the ground, so V SLOPE It will also increase linearly.

[0035] The present invention also provides a slope compensation method for a BOOST switching power supply, comprising the following steps:

[0036] Step a: using a compensation reference current generating module to generate a compensation reference current according to the real-time voltage difference between the output voltage VOUT and the input voltage VIN of the BOOST switching power supply;

[0037] Step b: mirroring the generated reference current and providing it to the ramp current generating module and the zeroing current generating module respectively;

[0038] Step c: Processing the generated compensation reference current through a ramp current generating module to generate a ramp current that varies with time;

[0039] Step c: Generate a current that is equal to the reference current but opposite in direction through the zero current generation module to reduce the slope compensation current I SLOPE The initial value of is set to zero;

[0040] Step d: synthesize the generated slope current and the generated zeroing current to obtain the final slope compensation current I SLOPE ;

[0041] Step e: The synthesized slope compensation current I SLOPE Converted into a slope compensation voltage V by the output module SLOPE ;

[0042] Step f: Set the slope compensation voltage V SLOPE The output is sent to the control unit of the BOOST switching power supply and is used to adjust the output of the switching power supply to achieve slope compensation and optimize the performance of the switching power supply.

[0043] The compensation reference current generating module of the present invention generates a compensation reference current according to the real-time voltage difference between the output VOUT and the input VIN of the switching power supply, and gives it to the ramp current generating module and the zeroing current generating module respectively after being mirrored. Under the joint action of the ramp current generating module and the zeroing current generating module, a current difference is generated, and finally the zeroing current generating module outputs the current difference, which is the slope compensation current value I SLOPE , I SLOPE The voltage V generated at the positive end of the output module resistor R4 SLOPE The output is sent to the control unit of the BOOST switching power supply to achieve the purpose of slope compensation.

[0044] The present invention uses the real-time voltage difference between the output VOUT and the input VIN of the BOOST switching power supply as a reference, and the generated reference current of the slope compensation automatically follows the changes of VOUT and VIN. The slope compensation does not need to consider the changes of VOUT and VIN, so it is not necessary to determine the maximum required slope compensation amount according to the maximum output voltage VOUT value and the minimum input voltage VIN value. At the same time, due to the effect of the zero current generation module, the initial value of the slope compensation is made zero. The two work together to greatly reduce the amount of slope compensation required in various application occasions, avoid the current mode switching power supply from evolving into a voltage mode switching power supply, maintain the advantage of fast response of the current mode switching power supply itself, and greatly reduce the influence of the slope compensation on the switch current limit value, so as to avoid the current limit value becoming very large and causing the system to face risks.

[0045] The working principle of the present invention is as follows:

[0046] refer to Figure 3 The slope compensation circuit of the present invention is applied to a BOOST switching power supply. For the sake of simplicity of description and better understanding of the present invention, it is assumed that the sizes of all MOS tubes are equal and the resistance values ​​of resistors R2 and R3 are equal for illustration.

[0047] Under the action of current source I1, the voltage V at point A A =VIN-V GS_N1 , voltage at point B V B =V A +V GS_P1 , we can get V from the above two equations B =VIN-V GS_N1 +V GS_P1 , ignoring V GS_N1 and V GS_P1 The difference is V B =VIN, that is, the voltage at point B is equal to the input power supply voltage VIN, so the current flowing through resistor R1 is After the current mirror, the currents of P2, P3 and P4 are all equal to I R1 .

[0048] Before the slope compensation of each cycle starts, the control signal OSC is high, N6 is turned on, and the voltage at point C is pulled to 0V. Because the currents of P3 and P4 are equal, the currents of N4 and N7 are equal, so the voltage at point D is equal to the voltage at point F, the voltage at point E is equal to the voltage at point G, and the current flowing through R2 is equal to the current flowing through R3, that is:

[0049]

[0050] I R3 Flow through N8, I R2The current of N8 is equal to the current of P6, and the slope compensation current I SLOPE =I P6 -I N9 =0,I SLOPE The current will flow through the resistor R4 and then to the sampling resistor R CS To ground, there is no voltage drop on resistor R4 and the slope compensation amount is 0.

[0051] When slope compensation starts, the control signal OSC becomes low, N6 is turned off, and the current source I P3 Under the action of, capacitor C1 is charged, and the voltage V C Gradually increases, the voltage at point D V D =V C +V GS_N4 , so V D Follow V C Increase at the same rate, V E =V D -V GS_N5 , so the voltage at point E also increases at an approximately equal rate, and the current flowing through R2 gradually increases, I R2 The current of P6 is gradually increased by the mirror image of P5 to P6. SLOPE =I P6 -I N8 , also gradually increases, I SLOPE The current will flow through the resistor R4 and then to the sampling resistor R CS To ground, voltage V SLOPE It will also increase linearly. From the above, we can know that the slope compensation current is equal to the increased part of R2 current, that is:

[0052]

[0053] Since capacitor C1 is in the current I P3 When charged under the action of, the rate of change of capacitor voltage is:

[0054]

[0055] From the previous article, we know:

[0056]

[0057] The slope compensation current formula obtained by combining the above formulas ①②③ is:

[0058]

[0059] So the slope compensation voltage formula is:

[0060]

[0061] According to the slope compensation theory, to eliminate the subharmonic interference of the current mode switching power supply, the following conditions must be met: the compensation slope must be greater than or equal to half of the inductor current drop slope. The formula for the inductor current drop slope of the BOOST switching power supply is:

[0062]

[0063] Equivalent to the sampling voltage terminal of the switching power supply, the compensation slope must be greater than or equal to half of the inductor current decline slope, which is equivalent to:

[0064]

[0065] The V obtained above SLOPE Substituting the formula into the equation, we get:

[0066]

[0067] Right now:

[0068]

[0069] It can be found that the above conditions that need to be met for slope compensation have nothing to do with VIN and VOUT. For a BOOST switching power supply system, as long as the chip meets the above conditions during design, that is, as long as the above conditions are met when designing the slope compensation reference current, even in the face of various input power supply VIN or different output voltages VOUT, the conditions for slope compensation can be met to achieve the purpose of eliminating subharmonic interference.

[0070] In summary, the slope compensation circuit of the present invention, since the reference current source used for slope compensation is proportional to VOUT-VIN after processing, and the slope required for the slope compensation of the BOOST switching power supply is greater than or equal to half of the slope of the inductor current, and the slope of the inductor current is proportional to VOUT-VIN, after offsetting the influence of VOUT-VIN, the slope compensation of the present invention does not need to consider the changes of VOUT and VIN, and does not need to determine the amount of slope compensation according to the maximum output voltage VOUT value and the minimum input voltage VIN value. At the same time, due to the effect of the zero current generation module, the initial value of the slope compensation is made zero. The two work together to greatly reduce the amount of slope compensation required in various application scenarios, avoid the current mode switching power supply from being converted into a voltage mode switching power supply, maintain the fast response advantage of the current mode switching power supply itself, and at the same time minimize the voltage superimposed on the switch sampling circuit by the slope compensation, greatly reduce the influence of the slope compensation on the switch current limit value, and avoid the current limit value becoming very large and causing the system to face risks.

[0071] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A slope compensation circuit is applied to a BOOST switching power supply, wherein the BOOST switching power supply comprises a control unit and a power unit, wherein: The control unit outputs a signal OSC to the slope compensation circuit to control the start and end of the slope compensation, and at the same time, the control unit outputs a signal DRV to the power unit to control the on and off of the power switch; The power unit outputs a feedback signal FB to the control unit for adjusting the output voltage; The slope compensation circuit outputs a slope current I SLOPE To the sampling resistor of the power unit, the ramp current is converted into a ramp voltage V SLOPE And output to the control unit.

2. The slope compensation circuit according to claim 1, characterized in that: The slope compensation circuit includes: a compensation reference current generating module, a slope current generating module, a zeroing current generating module, and an output module; the corresponding end of the compensation reference current generating module is electrically connected to the corresponding end of the slope current generating module and the zeroing current generating module respectively, and the corresponding end of the output module is also electrically connected to the other corresponding end of the slope current generating module and the zeroing current generating module.

3. The slope compensation circuit according to claim 2, characterized in that: The compensation reference current generating module comprises: a current source I1, a PMOS transistor P1 and a PMOS transistor P2, an NMOS transistor N1, an NMOS transistor N2 and an NMOS transistor N3, and a resistor R1, wherein a first end of the current source I1 is grounded, a second end is respectively connected to a source of the NMOS transistor N1 and a gate of the PMOS transistor P1, a drain and a gate of the NMOS transistor N1 are connected to an input voltage VIN, a source of the PMOS transistor P1 is connected to a first end of the resistor R1, a drain of the PMOS transistor P1 is respectively connected to a drain and a gate of the NMOS transistor N2 and a gate of the NMOS transistor N3, a second end of the resistor R1 is connected to an output voltage VOUT, sources of the NMOS transistor N2 and the NMOS transistor N3 are both grounded, and a drain of the NMOS transistor N3 is connected to a drain and a gate of the PMOS transistor P2; 4. The slope compensation circuit according to claim 3, characterized in that: The compensation reference current generating module generates a compensation reference current according to the real-time voltage difference between the output VOUT and the input VIN of the switching power supply. The reference current is mirrored through the PMOS transistor P2 to the ramp current generating module and another current is mirrored to the zeroing current generating module.

5. The slope compensation circuit according to claim 4, characterized in that: The slope current generating module includes: PMOS transistors P3 and PMOS transistors P5, NMOS transistors N4, NMOS transistors N5 and NMOS transistors N6, resistor R2, capacitor C1, and control signal OSC; the gate of the PMOS transistor P3 is connected to the gate and drain of the PMOS transistor P2 to mirror the slope compensation reference current of the PMOS transistor P2, the drain of the PMOS transistor P3 is respectively connected to the drain and gate of the NMOS transistor N4 and the gate of the NMOS transistor N5, the source of the NMOS transistor N4 is connected to the positive electrode of the capacitor C1 and the drain of the NMOS transistor N6, the negative electrode of the capacitor C1 and the source of the NMOS transistor N6 are grounded, the gate of the NMOS transistor N6 is connected to the control signal OSC, the source of the NMOS transistor N5 is connected to the positive electrode of the resistor R2, the negative electrode of the resistor R2 is grounded, and the drain of the NMOS transistor N5 is connected to the drain and gate of the PMOS transistor P5; 6. The slope compensation circuit according to claim 5, characterized in that: In the slope current generating module, when the control signal OSC is high, the NMOS transistor N6 is turned on, and the point C at the NMOS transistor N6 is pulled to the ground, and the voltage is 0V. At this time, the voltage at the point D at the NMOS transistor N4 and the voltage at the point E at the NMOS transistor N5 also remain unchanged, and the current flowing through the PMOS transistor P5 remains fixed. When the control signal OSC becomes low, the NMOS transistor N6 is turned off, and the slope compensation starts. The mirror current source of the PMOS transistor P3 flows through the NMOS transistor N4 to charge the capacitor C1, and the voltage at the point C increases linearly, and the voltages at the points D and E also increase linearly, and the current flowing through the PMOS transistor P5 and the PMOS transistor P6 also increases linearly.

7. The slope compensation circuit according to claim 6, characterized in that: The zero-elimination current generating module comprises: a PMOS transistor P4 and a PMOS transistor P6, an NMOS transistor N7 and an NMOS transistor N8, and a resistor R3; the gate of the PMOS transistor P4 is connected to the gate and the drain of the PMOS transistor P2 to mirror the reference current of the PMOS transistor P2, the drain of the PMOS transistor P4 is respectively connected to the drain and the gate of the NMOS transistor N7, and the gate of the NMOS transistor N8, the source of the NMOS transistor N7 is grounded, the source of the NMOS transistor N8 is connected to the positive electrode of the resistor R3, the negative electrode of the resistor R3 is grounded, the drain of the NMOS transistor N8 is connected to the drain of the PMOS transistor P6, and the gate of the PMOS transistor P6 is respectively connected to the gate and the drain of the PMOS transistor P5 to mirror the ramp current of P5; 8. The slope compensation circuit according to claim 7, characterized in that: In the zeroing current generating module, since the voltage at the point F of the NMOS transistor N7 and the voltage at the point G of the NMOS transistor N8 are also fixed, the current flowing through the NMOS transistor N8 is a fixed value, and the PMOS transistor P6 mirrors the current of the PMOS transistor P5. Before the slope compensation signal OSC is effective, the current of the PMOS transistor P6 is also a fixed value. Therefore, by setting the same transistor size and the same resistance value of the resistor R2 and the resistor R3, the current of the NMOS transistor N8 and the current of the PMOS transistor P6 can be equal. In this way, at the starting point of each compensation cycle, the current I output by the zeroing current generating module is SLOPE is 0.

9. The slope compensation circuit according to claim 8, characterized in that: The output module includes: a resistor R4 and an output ramp current I SLOPE and the ramp voltage V SLOPE One end of the resistor R4 is connected to the drain of the PMOS transistor P6 and the NMOS transistor N6, and the other end outputs I SLOPE The sampling resistor of the current to the power unit; at the beginning of each compensation cycle, I SLOPE =I P6 -I N8 =0, after each cycle compensation starts, I P6 The current increases linearly, while I N8 Always fixed, so I SLOPE Linear increase, I SLOPE The current will flow through the resistor R4 and then to the sampling resistor R CS to the ground, so V SLOPE It will also increase linearly.

10. A slope compensation method for a BOOST switching power supply, characterized in that: The following steps are involved: Step a: using a compensation reference current generating module to generate a compensation reference current according to the real-time voltage difference between the output voltage VOUT and the input voltage VIN of the BOOST switching power supply; Step b: mirroring the generated reference current and providing it to the ramp current generating module and the zeroing current generating module respectively; Step c: Processing the generated compensation reference current through a ramp current generating module to generate a ramp current that varies with time; Step c: Generate a current that is equal to the reference current but opposite in direction through the zero current generation module to reduce the slope compensation current I SLOPE The initial value of is set to zero; Step d: synthesize the generated slope current and the generated zeroing current to obtain the final slope compensation current I SLOPE ; Step e: The synthesized slope compensation current I SLOPE Converted into a slope compensation voltage V by the output module SLOPE ; Step f: Set the slope compensation voltage V SLOPE The output is sent to the control unit of the BOOST switching power supply and is used to adjust the output of the switching power supply to achieve slope compensation and optimize the performance of the switching power supply.

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