Boost internal ripple compensation circuit based on cot control

Abstract

The application discloses a BOOST internal ripple compensation circuit based on COT control and relates to the field of power supply design.The BOOST internal ripple compensation circuit comprises a conduction time control module TON, a driving module Driver, a ripple injection circuit and a comparator COMP; when the conduction time control module TON is in a conduction state, the comparator COMP is used for performing ripple compensation on the square wave generated by the ripple injection circuit, so that the BOOST system is guaranteed to be stable.The application does not need an equivalent resistor in series with an output capacitor, the ripple compensation is performed by the internal ripple injection circuit, the ripple of the output voltage is greatly reduced, meanwhile, the problem that the change trend of the ripple of the output capacitor is inconsistent with the change trend of the inductor current ripple is solved by the ripple injection circuit, the transient response is enhanced, compared with the traditional RC filter which needs a large capacitor and a resistor, the application only needs to select a small capacitor and a resistor to realize the ripple compensation, and the area of a chip is reduced.

Description

Technical Field

[0001] This invention relates to the field of power supply design, and more specifically to a BOOST internal ripple compensation circuit based on COT control. Background Technology

[0002] Boost circuits are widely used in low-power applications such as signal modulation and high-voltage sensor power supplies. However, in today's portable electronic devices, industrial automation systems, and new energy vehicles, traditional single PWM modulation methods cannot meet the demands for rapid response to load changes and high efficiency under light loads.

[0003] COT control, with its simple design, good transient response, and high efficiency under light load, has become the mainstream control method for DC-DC power chips. With the widespread use of ceramic capacitors, the ESR resistance of the output capacitor is becoming increasingly smaller. Relying solely on the ripple on the ESR resistor for stable control is insufficient (because the output capacitor's ripple phase lags behind the inductor current). A common solution is to use RC filtering at the switching node of the power stage to generate ripple in phase with the inductor current for control. However, if the power transistor is external, additional external pins are required, which undoubtedly increases the area cost. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a BOOST internal ripple compensation circuit based on COT control.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This application discloses a BOOST internal ripple compensation circuit based on COT control, including: a conduction time control module TON, a driver module Driver, a ripple injection circuit and a comparator COMP;

[0007] After the input voltage Vin is connected to the inductor L, it is connected to the drain of the first MOSFET ML and the anode of the diode D1 respectively. The cathode of the diode D1 is connected to the first capacitor Co, the first resistor R1 and the third resistor RL respectively. The first resistor R1 is also connected to the second resistor R2 and the negative input terminal of the comparator COMP respectively.

[0008] The gate of the first MOSFET ML is connected to the driving module Driver, and the source of the first MOSFET ML is connected to the ground terminal. The driving module Driver is also connected to the on-time control module TON and the ripple injection circuit. The ripple injection circuit is connected to the negative input terminal of the comparator COMP. The output terminal of the comparator COMP is connected to the switch on-time TON. The positive input terminal of the comparator COMP is connected to the reference voltage Vref.

[0009] The turn-off time of the constant on-time module TON is compensated for by superimposing the ripple voltage generated by the ripple injection circuit with the feedback voltage, thereby ensuring the stability of the BOOST system.

[0010] Furthermore, the ripple injection circuit includes an inverter, a second MOSFET M1, a third MOSFET M2, a fourth MOSFET M3, a fifth MOSFET M4, a first current source IB1, and a second current source IB2;

[0011] The first current source IB1 is connected to the first node a. The first node a is also connected to the drain of the second MOSFET M1, the fourth resistor R3, and the second capacitor C1. The fourth resistor R3 is also connected to the ground terminal. The source of the second MOSFET M1 is connected to the ground terminal. The gate of the second MOSFET M1 is connected in parallel with the input terminal of the inverter to receive the control signal of the conduction time control module TON. The output terminal of the inverter is connected to the gate of the fifth MOSFET M4.

[0012] The second current source IB2 is connected to the drain of the third MOSFET M2. The second capacitor C1 is also connected to the second node b. The second node b is connected to the drain of the third capacitor C2 and the fourth MOSFET M3. The gate of the fourth MOSFET M3 is connected to the gate of the third MOSFET M2. The source of the fourth MOSFET M3 is connected to the drain of the fifth MOSFET M4. The source of the fifth MOSFET M4 is connected to the ground terminal. The drain of the third MOSFET M2 is also connected to its own gate. The source of the third MOSFET M2 is also connected to the ground terminal. The third capacitor C2 is also connected to the output terminal of the ripple injection circuit, thereby outputting a ripple current Iripple. The ripple current Iripple forms a first ripple voltage Vripple through the third resistor R2.

[0013] Furthermore, the third MOSFET M2 and the fourth MOSFET M3 constitute a current mirror, and the size ratio of the fourth MOSFET M3 to the third MOSFET M2 is [missing information]. ,in This indicates the width of the fourth MOSFET M3. This indicates the length of the fourth MOSFET M3. This indicates the width of the third MOSFET M2. This represents the length of the third MOSFET M2, and N represents a positive integer.

[0014] Further, when the on-time control module TON is in the off period, if the sum of the feedback voltage Vfb and the first ripple voltage Vripple is equal to the reference voltage Vref, that is, Vripple+Vfb=Vref; then the comparator COMP outputs a high level to enable the on-time control module TON, which changes from low level to high level. After entering the driver module Driver, the sixth MOS transistor ML is turned on, meanwhile the second MOS transistor M1 is turned on and the fifth MOS transistor M4 is turned off. The first current source IB1 starts discharging through the second MOS transistor M1, the voltage Va at the first node a is pulled down from IB1×R3 to 0. The step voltage of the first node a is transmitted to the second node b through the second capacitor C1, and the second node b generates a synchronous drop; at this time, the third capacitor C2 generates a magnitude of current, where C represents the capacitance of the third capacitor C2, represents the voltage of the second node b, represents the rising edge time of the switching on-time TON. This current flows through the third resistor R2 to form a second ripple voltage Vripple1, the sum of the second ripple voltage Vripple1 and the feedback voltage Vfb is less than the reference voltage Vref, that is, Vripple1+Vfb<Vref. During the enable period of the on-time control module TON, the second ripple voltage Vripple1 rises slowly.

[0015] Further, when the enable of the on-time control module TON ends and it is in the off state, the second MOS transistor M1 is turned off, the fifth MOS transistor M4 is turned on, the voltage of the first node a rises from 0 to IB1×R3, the second node b rises synchronously, and the second node b is slowly discharged through the fourth MOS transistor M3; at this time, the third capacitor C2 generates a magnitude of current and decreases slowly, wherein , represents the voltage of the first node a, represents the falling edge time of the switching on-time TON. This current flows through the third resistor R2 to form a third ripple voltage Vripple2, the third ripple voltage Vripple2 is superimposed with the feedback voltage Vfb, and Vfb+Vripple2>Vref; the comparator COMP outputs a low level, and during the period when the on-time control module TON is in the off state, the sum of the third ripple voltage Vripple2 and the feedback voltage Vfb decreases over time. When Vfb+Vripple2=Vref, the comparator COMP outputs a high level to enable the on-time control module TON.

[0016] The beneficial effects of the present invention are:

[0017] 1) This application does not require the equivalent resistance of the output capacitor in series. The ripple is compensated by the internal ripple injection circuit, which greatly reduces the ripple of the output voltage. At the same time, the ripple injection circuit makes up for the problem that the ripple of the output capacitor and the ripple of the inductor current are inconsistent, thus enhancing the transient response.

[0018] 2) Compared to traditional RC filtering which requires large capacitors and resistors, this application only requires smaller capacitors and resistors to achieve ripple compensation, thus reducing the chip area. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the BOOST internal ripple compensation circuit based on COT control according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the ripple injection circuit according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the control waveform according to an embodiment of the present invention, wherein, Figure 3 (a) in the diagram is a waveform diagram of the comparator COMP. Figure 3 (b) in the diagram is a schematic diagram of the feedback voltage Vfb waveform without ripple injection. Figure 3 (c) in the diagram is a schematic diagram of the feedback voltage Vfb waveform with ripple injection. Figure 3 (d) in the figure is a waveform diagram of the inductor current. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] See Figures 1-3 This application discloses a BOOST internal ripple compensation circuit based on COT control, including: a conduction time control module TON, a driver module Driver, a ripple injection circuit and a comparator COMP;

[0024] After the input voltage Vin is connected to the inductor L, it is connected to the drain of the first MOSFET ML and the anode of the diode D1 respectively. The cathode of the diode D1 is connected to the first capacitor Co, the first resistor R1 and the third resistor RL respectively. The first resistor R1 is also connected to the second resistor R2 and the negative input terminal of the comparator COMP respectively.

[0025] The gate of the first MOSFET ML is connected to the driving module Driver, and the source of the first MOSFET ML is connected to the ground terminal. The driving module Driver is also connected to the on-time control module TON and the ripple injection circuit. The ripple injection circuit is connected to the negative input terminal of the comparator COMP. The output terminal of the comparator COMP is connected to the switch on-time TON. The positive input terminal of the comparator COMP is connected to the reference voltage Vref.

[0026] The turn-off time of the constant on-time module TON is compensated for by superimposing the ripple voltage generated by the ripple injection circuit with the feedback voltage, thereby ensuring the stability of the BOOST system.

[0027] For example, the ripple injection circuit includes an inverter, a second MOSFET M1, a third MOSFET M2, a fourth MOSFET M3, a fifth MOSFET M4, a first current source IB1, and a second current source IB2.

[0028] The first current source IB1 is connected to the first node a. The first node a is also connected to the drain of the second MOSFET M1, the fourth resistor R3, and the second capacitor C1. The fourth resistor R3 is also connected to the ground terminal. The source of the second MOSFET M1 is connected to the ground terminal. The gate of the second MOSFET M1 is connected in parallel with the input terminal of the inverter to receive the control signal of the conduction time control module TON. The output terminal of the inverter is connected to the gate of the fifth MOSFET M4.

[0029] The second current source IB2 is connected to the drain of the third MOSFET M2. The second capacitor C1 is also connected to the second node b. The second node b is connected to the drain of the third capacitor C2 and the fourth MOSFET M3. The gate of the fourth MOSFET M3 is connected to the gate of the third MOSFET M2. The source of the fourth MOSFET M3 is connected to the drain of the fifth MOSFET M4. The source of the fifth MOSFET M4 is connected to the ground terminal. The drain of the third MOSFET M2 is also connected to its own gate. The source of the third MOSFET M2 is also connected to the ground terminal. The third capacitor C2 is also connected to the output terminal of the ripple injection circuit, thereby outputting a ripple current Iripple. The ripple current Iripple forms a first ripple voltage Vripple through the third resistor R2.

[0030] For example, the third MOSFET M2 and the fourth MOSFET M3 constitute a current mirror, and the size ratio of the fourth MOSFET M3 to the third MOSFET M2 is [missing information]. ,in This indicates the width of the fourth MOSFET M3. represents the length of the fourth MOS transistor M3, represents the width of the third MOS transistor M2, represents the length of the third MOS transistor M2, and N represents a positive integer.

[0031] For example, when the on-time control module TON is in the off period, if the sum of the feedback voltage Vfb and the first ripple voltage Vripple is equal to the reference voltage Vref, that is, Vripple+Vfb=Vref; then the comparator COMP outputs a high level to enable the on-time control module TON, which changes from a low level to a high level (the state changes from 0 to 1). After entering the driver module Driver, the sixth MOS transistor ML is turned on, while the second MOS transistor M1 is turned on, and the fifth MOS transistor M4 is turned off. The first current source IB1 starts discharging through the second MOS transistor M1, and the voltage Va at the first node a is pulled down from IB1×R3 to 0. The step voltage of the first node a is transmitted to the second node b through the second capacitor C1, and the second node b generates a synchronous drop; at this time, the third capacitor C2 generates a magnitude of current, where C represents the capacitance of the third capacitor C2, represents the voltage at the second node b, represents the rising edge time of the switch on-time TON. This current flows through the third resistor R2 to form a second ripple voltage Vripple1. The sum of the second ripple voltage Vripple1 and the feedback voltage Vfb is less than the reference voltage Vref, that is, Vripple1+Vfb < Vref. During the enabling period of the on-time control module TON, the second ripple voltage Vripple1 rises slowly.

[0032] For example, when the enabling of the on-time control module TON ends and it is in the off state, the second MOS transistor M1 is turned off, the fifth MOS transistor M4 is turned on, the voltage at the first node a rises from 0 to IB1×R3, the second node b rises synchronously, and the second node b is slowly discharged through the fourth MOS transistor M3 (the voltage Vb at the second node b rises and then falls slowly); at this time, the third capacitor C2 generates a magnitude of current which decreases slowly, where , represents the voltage at the first node a, The falling edge time of the switch conduction time TON is represented. The current flowing through the third resistor R2 forms the third ripple voltage Vripple2. The third ripple voltage Vripple2 is superimposed on the feedback voltage Vfb, and Vfb + Vripple2 > Vref. This superimposed voltage has similar behavior to the output voltage when the first capacitor Co has a large equivalent series resistance ESR (after the conduction time control module TON is enabled, the voltage ripple first rises significantly and then begins to fall). The comparator COMP outputs a low level, and during the period when the conduction time control module TON is in the off state, the sum of the third ripple voltage Vripple2 and the feedback voltage Vfb decreases with time. When Vfb + Vripple2 = Vref, the comparator COMP outputs a high level, enabling the conduction time control module TON.

[0033] If ripple compensation and stabilization are achieved using an output capacitor connected in series with an ESR resistor, the output voltage will be approximately equal to... The ripple size is given by IL, where IL represents the inductor current, D represents the duty cycle, Io represents the load current, and Rser represents the ESR resistor in series with the output capacitor.

[0034] This invention does not require an external ESR resistor, so compared to using an output capacitor in series with an ESR resistor for compensation, it greatly reduces the output voltage ripple.

[0035] This application uses a ripple injection circuit to generate [something] when the on-time control module TON ends. A ripple of size ×R2 is generated and decreases slowly during the turn-off period of the conduction time control module TON. This ripple is consistent with the change of the inductor current during the turn-off period of ML, and this ripple is greater than the ripple of the feedback voltage. Therefore, the ripple and the feedback voltage are superimposed, and the trend of the change of the inductor current during the turn-off period of TON is still consistent with that of the change of the inductor current during the turn-off period of ML. Because there is and Since both the rising and falling edges t of the conduction time control module TON are relatively small, the capacitor can be selected to be relatively small, and the ripple voltage is... ×R2 or ×R2, because the feedback resistor is relatively large, so the internal It can achieve a smaller result.

[0036] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A BOOST internal ripple compensation circuit based on COT control, characterized in that, include: The on-time control module TON, the driver module, the ripple injection circuit, and the comparator COMP; After the input voltage Vin is connected to the inductor L, it is connected to the drain of the first MOSFET ML and the anode of the diode D1 respectively. The cathode of the diode D1 is connected to the first capacitor Co, the first resistor R1 and the third resistor RL respectively. The first resistor R1 is also connected to the second resistor R2 and the negative input terminal of the comparator COMP respectively. The gate of the first MOSFET ML is connected to the driving module Driver, and the source of the first MOSFET ML is connected to the ground terminal. The driving module Driver is also connected to the on-time control module TON and the ripple injection circuit. The ripple injection circuit is connected to the negative input terminal of the comparator COMP. The output terminal of the comparator COMP is connected to the switch on-time TON. The positive input terminal of the comparator COMP is connected to the reference voltage Vref. The turn-off time of the constant on-time module TON is compensated for by superimposing the ripple voltage generated by the ripple injection circuit with the feedback voltage, thereby ensuring the stability of the BOOST system.

2. The BOOST internal ripple compensation circuit based on COT control according to claim 1, characterized in that: The ripple injection circuit includes an inverter, a second MOSFET M1, a third MOSFET M2, a fourth MOSFET M3, a fifth MOSFET M4, a first current source IB1, and a second current source IB2. The first current source IB1 is connected to the first node a. The first node a is also connected to the drain of the second MOSFET M1, the fourth resistor R3, and the second capacitor C1. The fourth resistor R3 is also connected to the ground terminal. The source of the second MOSFET M1 is connected to the ground terminal. The gate of the second MOSFET M1 is connected in parallel with the input terminal of the inverter to receive the control signal of the conduction time control module TON. The output terminal of the inverter is connected to the gate of the fifth MOSFET M4. The second current source IB2 is connected to the drain of the third MOSFET M2. The second capacitor C1 is also connected to the second node b. The second node b is connected to the drain of the third capacitor C2 and the fourth MOSFET M3. The gate of the fourth MOSFET M3 is connected to the gate of the third MOSFET M2. The source of the fourth MOSFET M3 is connected to the drain of the fifth MOSFET M4. The source of the fifth MOSFET M4 is connected to the ground terminal. The drain of the third MOSFET M2 is also connected to its own gate. The source of the third MOSFET M2 is also connected to the ground terminal. The third capacitor C2 is also connected to the output terminal of the ripple injection circuit, thereby outputting a ripple current Iripple. The ripple current Iripple forms a first ripple voltage Vripple through the third resistor R2.

3. The BOOST internal ripple compensation circuit based on COT control according to claim 2, characterized in that: The third MOSFET M2 and the fourth MOSFET M3 form a current mirror, and the size ratio of the fourth MOSFET M3 to the third MOSFET M2 is [missing information]. ,in This indicates the width of the fourth MOSFET M3. This indicates the length of the fourth MOSFET M3. This indicates the width of the third MOSFET M2. N represents the length of the third MOSFET M2, and N represents a positive integer.

4. The BOOST internal ripple compensation circuit based on COT control according to claim 3, characterized in that: When the on-time control module TON is in the off period, if the sum of the feedback voltage Vfb and the first ripple voltage Vripple equals the reference voltage Vref, that is, Vripple+Vfb=Vref; then the comparator COMP outputs a high level to enable the on-time control module TON, which changes from low level to high level. After entering the driver module Driver, the sixth MOS transistor ML is turned on, the second MOS transistor M1 is turned on at the same time, and the fifth MOS transistor M4 is turned off. The first current source IB1 starts discharging through the second MOS transistor M1, the voltage Va of the first node a is pulled down from IB1×R3 to 0, the step voltage of the first node a is transmitted to the second node b through the second capacitor C1, and the second node b produces a synchronous drop; at this time, the third capacitor C2 generates a magnitude of current, wherein C represents the capacitance of the third capacitor C2, represents the voltage of the second node b, represents the rising edge time of the switching on-time TON. The current flows through the third resistor R2 to form a second ripple voltage Vripple1, the sum of the second ripple voltage Vripple1 and the feedback voltage Vfb is less than the reference voltage Vref, that is, Vripple1+Vfb<Vref, and the second ripple voltage Vripple1 rises slowly when the on-time control module TON is in the enabled period.

5. The BOOST internal ripple compensation circuit based on COT control according to claim 4, characterized in that: When the on-time control module TON ends and is in the off state, the second MOSFET M1 is turned off, and the fifth MOSFET M4 is turned on. The voltage of the first node a rises from 0 to IB1×R3, and the voltage of the second node b rises synchronously. The fourth MOSFET M3 slowly discharges the second node b. At this time, the third capacitor C2 generates a voltage of... The current decreases slowly, among which , This represents the voltage at the first node a. The falling edge time of the switch conduction time TON is represented. The current flowing through the third resistor R2 forms the third ripple voltage Vripple2. The third ripple voltage Vripple2 is superimposed on the feedback voltage Vfb, and Vfb + Vripple2 > Vref. The comparator COMP outputs a low level. During the time period when the conduction time control module TON is in the off state, the sum of the third ripple voltage Vripple2 and the feedback voltage Vfb decreases with time. When Vfb + Vripple2 = Vref, the comparator COMP outputs a high level, enabling the conduction time control module TON.

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