Slope compensation circuit

Abstract

The utility model relates to the technical field of digital power supply control, in particular to a slope compensation circuit. The main control unit is connected with the MCU and the DCDC power supply; comprising a power supply unit, a first slope compensation unit, a second slope compensation unit, an input interface A and an output interface B, a first external slope compensation unit and a second external slope compensation unit are added during current mode control of the digital switching power supply, so that control can be better realized, subharmonic oscillation is avoided, and external slope compensation is more stable and higher in linearity than internal slope compensation; and more flexible slope compensation is realized through matching with a driving signal given by the MCU unit.

Description

Technical Field

[0001] This utility model relates to the field of digital power control technology, and more specifically, to a slope compensation circuit. Background Technology

[0002] For existing digital DC-DC converters, voltage-mode control is mostly used due to slope compensation requirements. However, voltage-mode control has limitations in adjusting many technical parameters. In many operating conditions, current-mode control is better suited to the power supply module's operation, and it requires slope compensation for the sampled current. Currently, most solutions use the slope compensation circuit built into the microcontroller to achieve current control in the digital scheme.

[0003] Meanwhile, the existing external slope compensation control is simplistic, using hardware to control the slope compensation switch, and the slope compensation value is controlled by the power supply, making it relatively simple and inflexible.

[0004] Many microcontrollers today can be configured with ramp compensation circuits, but they have drawbacks such as insufficient accuracy and linearity, and sometimes cannot meet the requirements of actual applications. Utility Model Content

[0005] This invention addresses the problems of existing external slope compensation control being too simplistic and inflexible, and internal slope compensation lacking sufficient limitation. It proposes a slope compensation circuit that, by adding an external slope compensation unit in conjunction with the drive signal provided by the MCU, achieves more flexible slope compensation. This results in better control, avoids subharmonic oscillations, and demonstrates that external slope compensation is more stable and linear than internal compensation.

[0006] The specific implementation details of this utility model are as follows:

[0007] A ramp compensation circuit is connected to an MCU unit and a DC-DC power supply; it includes a power supply unit, a first ramp compensation unit, an input interface A, and an output interface B.

[0008] The output terminal of the power supply unit is connected to the input terminal of the first slope compensation unit and the input terminal of the second slope compensation unit.

[0009] The input terminal of the first slope compensation unit is connected to the MCU unit through input interface A, and the output terminal of the first slope compensation unit is connected to the DC-DC power supply through output interface B.

[0010] The MCU unit is used to generate a first drive signal based on the current sampling signal obtained from the DC-DC power supply;

[0011] The first slope compensation unit is used to generate a first slope compensation signal based on the acquired first driving signal;

[0012] The first ramp compensation signal is used to adjust the output voltage of the ramp circuit.

[0013] To better realize this utility model, the slope compensation circuit further includes a second slope compensation unit;

[0014] The input terminal of the second ramp compensation unit is connected to the MCU unit through input interface A, and the output terminal of the first ramp compensation unit is connected to the DC-DC power supply through output interface B.

[0015] The second slope compensation unit is used to generate a second slope compensation signal based on the acquired first driving signal;

[0016] The second slope compensation signal is used to adjust the voltage at the slope compensation point of the slope circuit.

[0017] To better realize this utility model, the power supply unit further includes a Zener diode D1, a resistor R1, a resistor R3, a transistor Q2, and a capacitor C1;

[0018] One end of the Zener diode D1 is connected to the power supply VDD, and the other end is connected to the base of the transistor Q2;

[0019] One end of the resistor R1 is connected between the power supply VDD and the Zener diode D1, and the other end is connected to the emitter of the transistor Q2.

[0020] One end of the resistor R3 is connected between the base of the transistor Q2 and the Zener diode D1, and the other end is connected to the capacitor C1.

[0021] One end of the capacitor C1 is connected to the collector of the transistor Q2 and the first slope compensation unit, and the other end is connected to the resistor R3 and the first slope compensation unit.

[0022] To better realize this utility model, the first slope compensation unit further includes a MOS transistor Q3 and a resistor R2;

[0023] One end of the resistor R2 is connected to the collector of the transistor Q2, the capacitor C1, and the source of the MOSFET Q3, and the other end of the resistor R2 is connected to the output interface B.

[0024] The drain of the MOS transistor Q3 is connected to ground, and the gate of the MOS transistor Q3 is connected to the input interface A.

[0025] To better realize this utility model, the second slope compensation unit further includes a MOS transistor Q1; the gate of the MOS transistor Q1 is connected between the gate of the MOS transistor Q3 and the input interface A, the drain of the MOS transistor Q1 is connected to ground, and the drain of the MOS transistor Q1 is connected to the output interface B.

[0026] To better realize this utility model, the slope compensation circuit further includes a resistor R4;

[0027] One end of the resistor R4 is connected between the gate of the MOSFET Q3 and the gate of the MOSFET Q1, and the other end is connected to the drain of the MOSFET Q3, the drain of the MOSFET Q1, and ground.

[0028] This utility model has the following beneficial effects:

[0029] This invention improves control and avoids subharmonic oscillations by adding an external slope compensation circuit to the current mode control of the digital switching power supply. The external slope compensation is more stable and has higher linearity than the internal one.

[0030] This invention achieves more flexible slope compensation by cooperating with the drive signals provided by the MCU. Attached Figure Description

[0031] Figure 1 The schematic diagram of the slope compensation circuit provided by this utility model. Detailed Implementation

[0032] To more clearly illustrate the technical solutions of the embodiments of this utility model, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the described embodiments are only some embodiments of this utility model, not all embodiments, and therefore should not be regarded as a limitation on the scope of protection. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0033] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances. Example 1

[0034] This embodiment proposes a ramp compensation circuit, which is connected to an MCU unit and a DC-DC power supply; it includes a power supply unit, a first ramp compensation unit, an input interface A, and an output interface B.

[0035] The output terminal of the power supply unit is connected to the input terminal of the first slope compensation unit and the input terminal of the second slope compensation unit.

[0036] The input terminal of the first slope compensation unit is connected to the MCU unit through input interface A, and the output terminal of the first slope compensation unit is connected to the DC-DC power supply through output interface B.

[0037] The MCU unit is used to generate a first drive signal based on the current sampling signal obtained from the DC-DC power supply;

[0038] The first slope compensation unit is used to generate a first slope compensation signal based on the acquired first driving signal;

[0039] The first ramp compensation signal is used to adjust the output voltage of the ramp circuit.

[0040] Working principle: This embodiment achieves better control and avoids subharmonic oscillation by adding an external slope compensation circuit during current mode control of the digital switching power supply. The external slope compensation is more stable and has higher linearity than the internal one. By cooperating with the drive signal given by the MCU, more flexible slope compensation can be achieved. Example 2

[0041] Based on Embodiment 1 above, the slope compensation circuit in this embodiment further includes a second slope compensation unit;

[0042] The input terminal of the second ramp compensation unit is connected to the MCU unit through input interface A, and the output terminal of the first ramp compensation unit is connected to the DC-DC power supply through output interface B.

[0043] The second slope compensation unit is used to generate a second slope compensation signal based on the acquired first driving signal;

[0044] The second slope compensation signal is used to adjust the voltage at the slope compensation point of the slope circuit.

[0045] Working principle: This embodiment further includes a second slope compensation unit, which can control the voltage at the slope compensation point to achieve a more regular voltage waveform, making it easier to use. In actual use, it can be added or not according to the actual situation.

[0046] The other parts of this embodiment are the same as those in Embodiment 1 above, so they will not be described again. Example 3

[0047] This embodiment is based on any one of Embodiments 1-2 above, such as Figure 1 As shown, the specific structure of the power supply unit is described using a specific embodiment.

[0048] The power supply unit includes a Zener diode D1, a resistor R1, a resistor R3, a transistor Q2, and a capacitor C1;

[0049] One end of the Zener diode D1 is connected to the power supply VDD, and the other end is connected to the base of the transistor Q2;

[0050] One end of the resistor R1 is connected between the power supply VDD and the Zener diode D1, and the other end is connected to the emitter of the transistor Q2.

[0051] One end of the resistor R3 is connected between the base of the transistor Q2 and the Zener diode D1, and the other end is connected to the capacitor C1.

[0052] One end of the capacitor C1 is connected to the collector of the transistor Q2 and the first slope compensation unit, and the other end is connected to the resistor R3 and the first slope compensation unit.

[0053] Working Principle: In this embodiment, it is assumed that VCC supplies 12V and Zener diode D1 supplies 3.3V. Therefore, the base voltage of transistor Q2 is 12V - 3.3V = 8.7V due to the presence of Zener diode D1. The power supply VCC, through resistor R1, provides 12V to the emitter of transistor Q2, causing Q2 to conduct. VCC then charges capacitor C1 through current-limiting resistor R1. When capacitor C1 is charged to 3.3V - 0.7V = 2.6V, transistor Q2 turns off, ensuring that the voltage across capacitor C1 does not exceed the set 2.6V, protecting the downstream circuit. The current from capacitor C1 is output through resistor R2 to the point requiring slope compensation, thus achieving slope compensation.

[0054] The other parts of this embodiment are the same as any one of the above embodiments 1-2, so they will not be described again. Example 4

[0055] This embodiment is based on any one of embodiments 1-3 above, such as Figure 1 As shown, the structure of the first slope compensation circuit and the second slope compensation circuit will be described in detail with reference to a specific embodiment.

[0056] The first slope compensation unit includes a MOSFET Q3 and a resistor R2;

[0057] One end of the resistor R2 is connected to the collector of the transistor Q2, the capacitor C1, and the source of the MOSFET Q3, and the other end of the resistor R2 is connected to the output interface B.

[0058] The drain of the MOS transistor Q3 is connected to ground, and the gate of the MOS transistor Q3 is connected to the input interface A.

[0059] The second slope compensation unit includes a MOS transistor Q1; the gate of the MOS transistor Q1 is connected between the gate of the MOS transistor Q3 and the input interface A, the drain of the MOS transistor Q1 is connected to ground, and the drain of the MOS transistor Q1 is connected to the output interface B.

[0060] The slope compensation circuit also includes resistor R4;

[0061] One end of the resistor R4 is connected between the gate of the MOSFET Q3 and the gate of the MOSFET Q1, and the other end is connected to the drain of the MOSFET Q3, the drain of the MOSFET Q1, and ground.

[0062] Working Principle: In this embodiment, when the capacitor is charged to 3.3V - 0.7V = 2.6V, transistor Q2 is cut off, ensuring that the voltage across capacitor C1 does not exceed the set 2.6V, thus protecting the downstream circuit. The current on capacitor C1 is output through resistor R2 to the point requiring slope compensation, achieving slope compensation. Simultaneously, the voltage across capacitor C1 is controlled by MOSFET Q3, which in turn controls the output voltage of the slope compensation circuit. MOSFET Q1 can control the voltage at the slope compensation point, achieving a more regular voltage waveform for ease of use. In practical applications, its addition can be selected based on actual conditions.

[0063] In digital power supplies such as DC-DC half-bridge and full-bridge converters, if current-mode control is desired, the subharmonic oscillation problem at large duty cycles needs to be addressed. The best way to solve this problem is to superimpose slope compensation onto the current sampling signal. In this circuit, the drive of MOSFETs Q1 and Q3 is provided by the MCU. The MCU calculates the required duty cycle based on the input and output voltages of the main power section of the DC-DC power supply, the switching frequency, and through the outer voltage loop and internal current loop. It then uses a timer to generate an external slope compensation drive signal synchronized with the PWM switching cycle, which is sent to the external slope compensation circuit through port A. When slope compensation is required for the entire power supply operation, typically when the main MOSFET of the DC-DC power supply is turned on, the MCU outputs a low slope compensation drive signal (input port B is low), MOSFETs Q1 and Q3 are turned off, and the slope compensation circuit starts working. The slope compensation voltage rises linearly according to the set slope, passes through a set resistor R4, and is superimposed on the current sampling port at a certain ratio, then sent to the MCU. The MCU detects the voltage at the current sampling port to perform peak current control, cycle-by-cycle control, short-circuit protection control, etc., and provides a suitable PWM switching signal through the internal loop to control the normal operation and abnormal protection of the entire power supply. When the MCU detects the power supply operating state and does not require external slope compensation (i.e., when the main MOSFET is turned off), the MCU outputs a high slope compensation drive signal (input port B is high), and MOSFETs Q1 and Q3 are turned on. MOSFET Q1 pulls down the voltage of the capacitor in the slope compensation circuit, making the slope compensation value 0. At the same time, MOSFET Q3 pulls down the current and uses the port voltage to achieve a port voltage of 0, ensuring the stability and reliability of the current sampling in the next cycle and the slope compensation when it is turned on, thus better achieving stable and reliable control of the entire power supply.

[0064] The switching of MOSFETs Q1 and Q3 is controlled by drive signals from the MCU, offering flexibility and enabling better integration with required circuits. This allows for periodic changes in slope compensation, achieving real-time slope compensation. R4 is a pull-down resistor at the drive terminals of MOSFETs Q1 and Q3, preventing MOSFETs from mistakenly turning on and ensuring circuit stability and reliability.

[0065] The parameters in the circuit can be modified according to the user's needs. The charging speed of capacitor C1 can be changed by altering resistor R1, achieving different slopes in the slope compensation circuit. The maximum value of the slope compensation can be achieved by changing the value of Zener diode D1, allowing for flexible modification without altering the supply voltage, making it more convenient to use. Since the slope compensation is driven and controlled by a MOSFET, and the drive is provided by the MCU, it is even more convenient and flexible to use through different control methods.

[0066] This embodiment adds an external slope compensation circuit to the current-mode control of the digital switching power supply, which improves control, avoids subharmonic oscillations, and provides greater stability and linearity than internal slope compensation. The slope compensation method is also more flexible, allowing for flexible control of the slope rate and peak point. By controlling the parameters in the control circuit, the slope and peak point can be flexibly controlled without changing the supply voltage, enabling flexible settings according to requirements and protecting the downstream circuitry. This embodiment has a wider range of applications because its slope compensation switching is not controlled by hardware, making it more flexible in its use and no longer limited to current slope compensation; it can also be used in other applications where needed.

[0067] The other parts of this embodiment are the same as any one of the embodiments 1-3 above, so they will not be described again.

[0068] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A slope compensation circuit, connected to an MCU unit and a DC-DC power supply; characterized in that, Includes a power supply unit, a first slope compensation unit, input interface A, and output interface B; The output terminal of the power supply unit is connected to the input terminal of the first slope compensation unit and the input terminal of the second slope compensation unit. The input terminal of the first slope compensation unit is connected to the MCU unit through input interface A, and the output terminal of the first slope compensation unit is connected to the DC-DC power supply through output interface B. The MCU unit is used to generate a first drive signal based on the current sampling signal obtained from the DC-DC power supply; The first slope compensation unit is used to generate a first slope compensation signal based on the acquired first driving signal; The first ramp compensation signal is used to adjust the output voltage of the ramp circuit.

2. The slope compensation circuit according to claim 1, characterized in that, The slope compensation circuit also includes a second slope compensation unit; The input terminal of the second ramp compensation unit is connected to the MCU unit through input interface A, and the output terminal of the first ramp compensation unit is connected to the DC-DC power supply through output interface B. The second slope compensation unit is used to generate a second slope compensation signal based on the acquired first driving signal; The second slope compensation signal is used to adjust the voltage at the slope compensation point of the slope circuit.

3. The slope compensation circuit according to claim 2, characterized in that, The power supply unit includes a Zener diode D1, a resistor R1, a resistor R3, a transistor Q2, and a capacitor C1; One end of the Zener diode D1 is connected to the power supply VDD, and the other end is connected to the base of the transistor Q2; One end of the resistor R1 is connected between the power supply VDD and the Zener diode D1, and the other end is connected to the emitter of the transistor Q2. One end of the resistor R3 is connected between the base of the transistor Q2 and the Zener diode D1, and the other end is connected to the capacitor C1. One end of the capacitor C1 is connected to the collector of the transistor Q2 and the first slope compensation unit, and the other end is connected to the resistor R3 and the first slope compensation unit.

4. A slope compensation circuit according to claim 3, characterized in that, The first slope compensation unit includes a MOSFET Q3 and a resistor R2; One end of the resistor R2 is connected to the collector of the transistor Q2, the capacitor C1, and the source of the MOSFET Q3, and the other end of the resistor R2 is connected to the output interface B. The drain of the MOS transistor Q3 is connected to ground, and the gate of the MOS transistor Q3 is connected to the input interface A.

5. A slope compensation circuit according to claim 4, characterized in that, The second slope compensation unit includes a MOS transistor Q1; the gate of the MOS transistor Q1 is connected between the gate of the MOS transistor Q3 and the input interface A, the drain of the MOS transistor Q1 is connected to ground, and the drain of the MOS transistor Q1 is connected to the output interface B.

6. A slope compensation circuit according to claim 5, characterized in that, The slope compensation circuit also includes resistor R4; One end of the resistor R4 is connected between the gate of the MOSFET Q3 and the gate of the MOSFET Q1, and the other end is connected to the drain of the MOSFET Q3, the drain of the MOSFET Q1, and ground.

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