Constant on-time power converter and method of dynamically adjusting minimum on-time

Abstract

A constant on-time power converter has a function of dynamically adjusting a minimum on-time. The power converter includes an energy storage switch, an output inductor, an input voltage associated circuit, a preset minimum on-time circuit, an output power associated circuit and a comparison circuit. The energy storage switch is conductible for an on-time in an operation period. The output inductor is coupled with the energy storage switch at a switching node. The input voltage associated circuit receives an input voltage to provide a ramp signal. The preset minimum on-time circuit is to provide a minimum threshold voltage. The output power associated circuit is to provide an output modulation threshold voltage. The comparison circuit receives the ramp signal and a voltage at a summing node. When the ramp signal changes to reach the voltage at the summing node, the comparison circuit outputs an off signal to end the on-time.

Description

Technical Field

[0001] This invention relates to a power converter and a method for adjusting the on-time, and more particularly to a constant on-time power converter and a method for dynamically adjusting the minimum on-time. Background Technology

[0002] For constant-time converters (COT converters), a fixed output-to-input conversion ratio corresponds to a constant on-time (COT). In other words, this constant on-time is determined by the output and input voltages. For power converters with lower conversion ratios, the on-time is typically constant under higher load conditions. Therefore, systems often improve operational responsiveness by increasing the frequency. However, increasing the frequency leads to increased switching losses, directly impacting system efficiency.

[0003] Therefore, how to design a constant on-time power converter and a method for dynamically adjusting the minimum on-time, and how to solve the problems and technical bottlenecks of the prior art by dynamically adjusting the on-time, especially the method for dynamically adjusting the minimum on-time, and the corresponding power converter for implementing the method, is an important research topic for the inventors of this case. Summary of the Invention

[0004] One objective of this invention is to provide a constant on-time power converter to solve the problems of the prior art.

[0005] To achieve the aforementioned objective, the constant on-time power converter proposed in this invention has the function of dynamically adjusting the minimum on-time. The power converter includes an energy storage switch, an output inductor, an input voltage correlation circuit, a preset minimum on-time circuit, an output energy correlation circuit, and a comparator circuit. The energy storage switch receives a pulse-width modulation signal during its operating cycle and can be turned on for a certain on-time. The first terminal of the output inductor is coupled to the energy storage switch at a switching node, and the second terminal of the output inductor is coupled to the load. The input voltage correlation circuit receives the input voltage to provide a ramp signal, the slope of which is positively correlated with the input voltage. The preset minimum on-time circuit is coupled to a summing node to provide a minimum threshold voltage. The output energy correlation circuit is coupled to a summing node to provide an output modulation threshold voltage, which is positively correlated with the output voltage provided to the load. The voltage at the summing node is the larger of the minimum threshold voltage and the output modulation threshold voltage. The comparator circuit has a first input point and a second input point; the first input point receives the ramp signal, and the second input point receives the voltage at the summing node. When the slope signal changes to the voltage of the summing node, the comparator circuit outputs a turn-off signal to end the conduction time.

[0006] In one embodiment, the power converter further includes a power extraction sensing circuit. The power extraction sensing circuit is coupled to a summing node to provide a load modulation threshold voltage. The load modulation threshold voltage is positively correlated with the power extracted by the load and increases the minimum threshold voltage by a voltage increment equal to the load modulation threshold voltage.

[0007] In one embodiment, the preset minimum on-time circuit includes a constant current source and a resistor. The resistor is coupled to the constant current source. The constant current source and the resistor provide a minimum voltage value to correspondingly set the minimum on-time.

[0008] In one embodiment, the electrical energy drawn from the load is positively correlated with the inductor current flowing through the output inductor to the load. A power extraction sensing circuit detects the inductor current to modulate the load extraction modulation threshold voltage.

[0009] In one embodiment, the output inductor has a DC resistor in series. The average value of the inductor current flowing through the DC resistor results in a DC voltage across the DC resistor. The amount of electrical energy drawn by the load is determined based on this DC voltage.

[0010] In one embodiment, the power extraction sensing circuit includes a voltage divider resistor circuit and a conductance unit. The voltage divider resistor circuit is used to divide the output voltage to obtain a divided output voltage. The conductance unit is coupled to the voltage divider resistor circuit. The first input terminal of the conductance unit receives the node voltage of the switching node, and the second input terminal of the conductance unit receives the divided output voltage. The conductance ratio product is then applied to the voltage difference between the node voltage and the divided output voltage to obtain a compensation current source that is positively correlated with the inductor current.

[0011] Another objective of this invention is to provide a method for dynamically adjusting the minimum conduction time, thereby solving the problems of the prior art.

[0012] To achieve the aforementioned objective, the method for dynamically adjusting the minimum on-time proposed in this invention can be applied to a constant on-time power converter. The constant on-time power converter has an energy storage switch and an output inductor, and is coupled to a load. The method for dynamically adjusting the minimum on-time includes: setting a minimum on-time of the energy storage switch; modulating the minimum on-time according to the energy drawn by the load; determining the on-time of the energy storage switch within the operating cycle based on the output voltage and input voltage of the constant on-time power converter; when the energy storage switch is on, energy can be stored in the output inductor; when the on-time is greater than or equal to the minimum on-time, the energy storage switch conducts for the length of that on-time; when the on-time is less than the minimum on-time, the energy storage switch conducts for the length of that minimum on-time.

[0013] In one embodiment, the step of determining the conduction time based on the output voltage and the input voltage includes: an input voltage correlation circuit providing a ramp signal positively correlated with the input voltage; a preset minimum conduction time circuit providing a minimum threshold voltage to the summing node; an output power correlation circuit providing an output modulation threshold voltage positively correlated with the output voltage to the summing node, wherein the voltage of the summing node is the larger of the minimum threshold voltage and the output modulation threshold voltage; and a comparison circuit comparing the ramp signal with the voltage of the summing node, wherein the comparison circuit ends the conduction time when the change in the ramp signal reaches the voltage of the summing node.

[0014] In one embodiment, the step of setting the minimum on-time includes: the preset minimum on-time circuit makes the current of the constant current source flow through the resistor, and takes the voltage level generated at the resistor terminal as the minimum threshold voltage.

[0015] In one embodiment, the step of modulating the minimum on-time in a positive correlation with the power drawn from the load includes: the power drawn sensing circuit providing a load modulation threshold voltage positively correlated with the power drawn from the load to the summing node, and increasing the minimum threshold voltage by a voltage increment, the voltage increment being the load modulation threshold voltage.

[0016] In one embodiment, the power extraction sensing circuit determines the amount of power to be extracted by detecting the inductor current flowing through the output inductor to the load.

[0017] In one embodiment, the DC voltage is calculated based on the average value of the inductor current and the DC resistance of the output inductor, and the amount of electrical energy extracted is determined based on the DC voltage.

[0018] In one embodiment, the current value of the compensation current source is the product of the voltage difference between the node voltage between the energy storage switch and the output inductor and the voltage divider of the output voltage, and the conductance ratio.

[0019] By using the proposed constant on-time power converter and the method of dynamically adjusting the minimum on-time, the minimum on-time is dynamically adjusted, thereby improving the power conversion efficiency.

[0020] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Attached Figure Description

[0021] Figure 1 This is a circuit architecture diagram of the first embodiment of the constant on-time power converter of the present invention.

[0022] Figure 2 This is a circuit architecture diagram of a second embodiment of the constant on-time power converter of the present invention.

[0023] Figure 3 This is a flowchart of the method for dynamically adjusting the minimum conduction time according to the present invention.

[0024] Figure 4 The waveform diagram shows the signal for dynamically adjusting the minimum conduction time according to the present invention.

[0025] Among them, the attached reference numerals

[0026] HS: Energy storage switch L: Output inductor

[0027] 10: Input voltage correlation circuit; 20: Preset minimum conduction time circuit

[0028] 30: Output power correlation circuit; 40: Extraction power sensing circuit

[0029] 90: Comparator circuit 41: Voltage divider resistor circuit

[0030] 42: Conductivity unit; 50: Pulse width modulation controller

[0031] 60: Non-overlapping processing unit; 71: First driver

[0032] 72: Second Driver

[0033] LX: Switching node V IN Input voltage

[0034] Chr_on: Ramp signal; SN: Aggregation node

[0035] V REF_ Ton_In: Output modulation threshold voltage V REF_ Ton: Sum of node voltages

[0036] TONr: Turn-off signal T ON On-time

[0037] I DC *R: Minimum threshold voltage Isns*R: De-loading modulation threshold voltage

[0038] I DC Constant current source Opt: Variable resistor

[0039] I L Inductance current (DCR): DC resistance

[0040] V DCR DC voltage V OUT Output voltage

[0041] V LX Node voltage αV OUT Voltage divider output voltage

[0042] gm: Conductivity ratio; Isns: Compensating current source

[0043] TON _min: Minimum on-time

[0044] S11~S16: Steps Detailed Implementation

[0045] The structural and working principles of the present invention will be described in detail below with reference to the accompanying drawings:

[0046] Please see Figure 1 The first embodiment shown is a circuit architecture diagram of the first embodiment of the constant-on-time power converter of the present invention. This constant-on-time power converter (COT converter) has the function of dynamically adjusting the minimum on-time. The constant-on-time power converter includes an energy storage switch HS, an output inductor L, an input voltage correlation circuit 10, a preset minimum on-time circuit 20, an output energy correlation circuit 30, and a comparator circuit 90.

[0047] like Figure 1 In the first embodiment shown, the energy storage switch HS is a high-side switch, but this is not intended to limit the invention. Furthermore, in conjunction with Figure 4 The diagram shown is a waveform of the signal used to dynamically adjust the minimum on-time according to the present invention. Under different boost and buck circuit topologies, this switch, used for energy storage operation of the power converter, is the energy storage switch corresponding to this embodiment. The energy storage switch HS can receive a pulse width modulation (PWM) signal within one operating cycle, causing the energy storage switch HS to be turned on for an on-time T. ON .by Figure 1 In the illustrated embodiment, the energy storage switch HS, acting as the high-side switch, is driven by the first driver 71, while the other low-side switch is driven by the second driver 72. Furthermore, the first driver 71 and the second driver 72 are connected to a non-overlapping processing unit 60. The purpose of this unit is to receive the pulse width modulation signal PWM through the non-overlapping processing unit 60 and control the high-side switch and the low-side switch separately (without time overlap) to avoid damage to the high-side switch and the low-side switch due to short-through caused by simultaneous conduction.

[0048] The first terminal of the output inductor L is coupled to the energy storage switch HS at the switching node LX, and the second terminal of the output inductor L is coupled to the load (not shown) to provide the output voltage V. OUT .

[0049] Input voltage correlation circuit 10 receives input voltage V INThis is used to provide the ramp signal Chr_on. The slope of the ramp signal Chr_on is related to the input voltage V. IN Positive correlation. A preset minimum on-time circuit 20 is coupled to the summing node SN to provide the minimum threshold voltage I. DC *R. In an embodiment of the present invention, the preset minimum conduction time circuit 20 includes a constant current source I. DC With variable resistor Opt. Where the constant current source I DC The product of the current value and the resistance value R of the variable resistor Opt determines the minimum voltage value, which is used to set the minimum on-time T accordingly. ON The minimum on-time T can be dynamically adjusted by changing the resistance value R of the variable resistor Opt. ON _min.

[0050] The output power correlation circuit 30 is coupled to the summing node SN to provide the output modulation threshold voltage V. REF_ Ton_In. Where the output modulation threshold voltage V... REF_ Ton_In and the output voltage V supplied to the load OUT Positive correlation. It's worth mentioning that the summation of the voltage V at node SN... REF_ Ton is the minimum threshold voltage I. DC *R and output modulation threshold voltage V REF_ Ton_In is determined by the larger of the two. In other words, if the minimum threshold voltage I... DC *R is greater than the output modulation threshold voltage V REF_ Ton_In, summing the voltage V at node SN. REF_ Ton is the minimum threshold voltage I. DC *R; Conversely, if the output modulation threshold voltage V REF_ Ton_In is greater than the minimum threshold voltage I DC *R, summing the voltage V at node SN. REF_ Ton is the output modulation threshold voltage V. REF_ Ton_In.

[0051] Comparator circuit 90 has a first input point and a second input point. The first input point receives the ramp signal Chr_on, and the second input point receives the voltage V of the summing node SN. REF_ Ton. When the change in the ramp signal Chr_on reaches the voltage V of the summing node SN. REF_ When Ton (e.g.) Figure 4 As shown, the comparator circuit 90 outputs a turn-off signal TONr to trigger the end edge of the pulse width modulation signal PWM, thereby ending the on-time T during this operating cycle. ON .like Figure 1As shown, the pulse width modulation controller 50 is connected to the non-overlapping processing unit 60, and the pulse width modulation controller 50 receives the off signal TONr output by the comparator circuit 90. The off signal TONr triggers the end edge of the pulse width modulation signal PWM, thereby ending the conduction time T during the operation cycle. ON .

[0052] like Figure 2 The second embodiment shown is a circuit architecture diagram of a second embodiment of the constant on-time power converter of the present invention. The constant on-time power converter further includes a power extraction sensing circuit 40. The power extraction sensing circuit 40 is coupled to a summing node SN to provide a descent modulation threshold voltage Isns*R. The descent modulation threshold voltage Isns*R is positively correlated with the power extracted from the load and ensures that the minimum threshold voltage I... DC *R increases the voltage increment. The voltage increment is the de-loading modulation threshold voltage Isns*R. The energy drawn from the load is equal to the inductor current I flowing from the output inductor L to the load. L Positive correlation. The energy sensing circuit 40 detects the inductor current I. L This is used to modulate the de-loading modulation threshold voltage Isns*R. The output inductor L has a series DC resistance DCR. The inductor current I flowing through the DC resistance DCR is... L The average value is used to obtain the DC voltage V across the DC resistor DCR. DCR That is, DC voltage V DCR Equal to inductor current I L The product of the average value and the DC resistance DCR. Based on the DC voltage V... DCR This determines the amount of electrical energy that the load draws.

[0053] Specifically, the power extraction sensing circuit 40 includes a voltage divider resistor circuit 41 and a conductivity unit 42. The voltage divider resistor circuit 41 is used to measure the output voltage V. OUT Voltage division to obtain the voltage divider output voltage αV OUT Conductivity unit 42 is coupled to voltage divider resistor circuit 41. A first input terminal of conductivity unit 42 receives the node voltage V of switch switching node LX. LX The second input terminal of the conductivity unit 42 receives the output voltage αV through voltage division. OUT Used to measure node voltage V LX With the voltage divider output voltage αV OUT The voltage difference is multiplied by the conductance ratio gm to obtain the product with respect to the inductor current I. L The compensating current source Isns is positively correlated. That is, the current value of the compensating current source Isns is equal to the node voltage V. LX With the voltage divider output voltage αV OUTThe voltage difference is the product of the conductance ratio gm. The product of the current value of the compensation current source Isns and the resistance value R of the variable resistor Opt determines the de-loading modulation threshold voltage Isns*R.

[0054] Please see Figure 3 The diagram shown is a flowchart of the method for dynamically adjusting the minimum on-time according to the present invention. This method for dynamically adjusting the minimum on-time can be applied to a constant on-time power converter (COT converter). The COT converter has an energy storage switch HS and an output inductor L, and is coupled to a load. The method for dynamically adjusting the minimum on-time includes:

[0055] First, in step S11, the minimum on-time of the energy storage switch is set, including: the preset minimum on-time circuit 20 causes the constant current source I to... DC The current flows through the variable resistor Opt. The fixed current source I is selected. DC The voltage level resulting from the product of the resistance value R of the variable resistor Opt is used as the minimum threshold voltage I at the summing node SN. DC *R, through the minimum threshold voltage I DC *R is used to set the minimum on-time Ton_min of the energy storage switch HS.

[0056] Secondly, in step S12, the minimum on-time T is modulated in a positive correlation with the energy drawn from the load. ON _min, including: the power extraction sensing circuit 40 provides a load modulation threshold voltage Isns*R that is positively correlated with the power extracted from the load to the summing node SN, and makes the minimum threshold voltage I DC *R adds a voltage increment, where the voltage increment can be the de-loading modulation threshold voltage Isns*R; the de-loading modulation threshold voltage Isns*R is equal to the product of the current value of the compensation current source Isns and the resistance value R of the variable resistor Opt.

[0057] The power extraction sensing circuit 40 can detect the inductor current I flowing through the output inductor L to the load. L To detect the amount of electrical energy drawn by the load; for example, based on the inductor current I. L The DC voltage V is obtained by calculating the average value of the output inductor L and the DC resistance DCR. DCR And according to the DC voltage V DCR To determine the amount of electrical energy extracted.

[0058] Wherein, the DC voltage V DCR The system can correspond to (1) the node voltage V between the energy storage switch HS and the output inductor L. LX (2) Output voltage V OUT The voltage divider output voltage αVOUT The voltage difference is then multiplied by the conductance ratio gm to determine the current value of the compensation current source Isns.

[0059] Then, in step S13, based on the output voltage V of the constant on-time power converter... OUT With input voltage V IN The conduction time T during which the energy storage switch HS receives a pulse width modulation (PWM) signal during its operating cycle determines the conduction time that the switch can be turned on. ON When the energy storage switch HS is turned on, electrical energy can be stored in the output inductor L. This step may further include: (1) the input voltage association circuit 10 provides energy related to the input voltage V. IN Positively correlated ramp signal Chr_on; (2) Preset minimum on-time circuit 20 provides minimum threshold voltage I DC *R to summing node SN; (3) Output power association circuit 30 provides power to the output voltage V OUT Positively correlated output modulation threshold voltage V REF_ Ton_In is connected to the summing node SN. The voltage V at the summing node SN is... REF_ Ton is the minimum threshold voltage I. DC *R and output modulation threshold voltage V REF_ Ton_In is the larger of the two; and (4) the comparison circuit 90 compares the ramp signal Chr_on with the voltage V of the summing node SN. REF_ Ton. When the slope signal Chr_on changes to reach the voltage V of the summing node SN. REF_ When Ton, the comparator circuit 90 ends its conduction time T. ON .

[0060] Then, in step S14, the conduction time T is determined. ON Is it greater than or equal to the conduction time T? ON _min. If the conduction time T ON Greater than or equal to the minimum conduction time T ON At time _min, the energy storage switch HS is turned on for the specified on-time T. ON The length of (S15 step). Conversely, if the conduction time T ON Less than the minimum conduction time T ON At time _min, the minimum conduction time T of the energy storage switch HS is _min. ON The length of _min (S16 step).

[0061] In summary, the constant on-time power converter and the method for dynamically adjusting the minimum on-time proposed in this invention can dynamically adjust the minimum on-time, thereby improving power conversion efficiency.

[0062] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A constant on-time power converter, characterized by dynamically adjusting the minimum on-time, wherein... The power converter includes: An energy storage switch that receives a pulse width modulation signal during an operating cycle and can be turned on for a conduction time; An output inductor, a first end of which is coupled to the energy storage switch at a switching node, and a second end of which is coupled to a load; An input voltage correlation circuit receives an input voltage and provides a ramp signal whose slope is positively correlated with the input voltage. A preset minimum on-time circuit, coupled to a summing node, is used to provide a minimum threshold voltage; An output power correlation circuit, coupled to the summing node, is used to provide an output modulation threshold voltage, wherein the output modulation threshold voltage is positively correlated with an output voltage supplied to the load; the voltage of the summing node is the larger of the minimum threshold voltage and the output modulation threshold voltage; and A comparator circuit has a first input point and a second input point. The first input point receives the ramp signal, and the second input point receives the voltage of the summing node. When the ramp signal changes to reach the voltage of the summing node, the comparator circuit outputs a turn-off signal to end the conduction time.

2. The constant on-time power converter as described in claim 1, characterized in that, The power converter further includes: A power extraction sensing circuit, coupled to the summing node, provides a load modulation threshold voltage that is positively correlated with the power extracted by the load and increases the minimum threshold voltage by a voltage increment, wherein the voltage increment is the load modulation threshold voltage.

3. The constant on-time power converter as described in claim 1, characterized in that, The preset minimum on-time circuit includes: A certain current source; and A resistor is coupled to the constant current source; The constant current source and the resistor provide a minimum voltage value to set the minimum conduction time accordingly.

4. The constant on-time power converter as described in claim 2, characterized in that, The electrical energy drawn by the load is positively correlated with the inductor current flowing through the output inductor to the load; the drawn electrical energy sensing circuit detects the inductor current to modulate the load modulation threshold voltage.

5. The constant on-time power converter as described in claim 4, characterized in that, The output inductor has a DC resistor in series; The average value of the inductor current flowing through the DC resistor results in a DC voltage across the DC resistor, and the amount of electrical energy drawn by the load is determined based on this DC voltage.

6. The constant on-time power converter as described in claim 2, characterized in that, The energy extraction sensing circuit includes: A voltage divider resistor circuit is used to divide the output voltage to obtain a divided output voltage; and A conductivity unit is coupled to the voltage divider resistor circuit; The first input terminal of the conductivity unit receives a node voltage of the switching node, and the second input terminal of the conductivity unit receives the output voltage through the voltage divider. The voltage difference between the node voltage and the output voltage divider is multiplied by a conductivity ratio to obtain a compensation current source that is positively correlated with an inductor current.

7. A method for dynamically adjusting the minimum on-time, applicable to a constant on-time power converter, the constant on-time power converter having an energy storage switch and an output inductor, the constant on-time power converter being coupled to a load, characterized in that, The method includes the following steps: Set a minimum on-time for the energy storage switch; The minimum on-time is modulated according to the positive correlation between the power drawn from the load and the minimum on-time. The step of modulating the minimum on-time based on the extracted power of the load includes: a extracted power sensing circuit provides a load modulation threshold voltage that is positively correlated with the extracted power of the load to a summing node, and increases a minimum threshold voltage by a voltage increment, the voltage increment being the load modulation threshold voltage. The on-time of the energy storage switch within an operating cycle is determined based on an output voltage and an input voltage of the constant on-time power converter. When the energy storage switch is on, energy can be stored in the output inductor. The step of determining the on-time based on the output voltage and the input voltage includes: an input voltage correlation circuit providing a ramp signal positively correlated with the input voltage; a preset minimum on-time circuit providing the minimum threshold voltage to the summing node; an output energy correlation circuit providing an output modulation threshold voltage positively correlated with the output voltage to the summing node, wherein the voltage of the summing node is the larger of the minimum threshold voltage and the output modulation threshold voltage; and a comparator circuit comparing the ramp signal with the voltage of the summing node; when the change in the ramp signal reaches the voltage of the summing node, the comparator circuit ends the on-time. When the conduction time is greater than or equal to the minimum conduction time, the energy storage switch conducts for the length of that conduction time; and When the conduction time is less than the minimum conduction time, the energy storage switch conducts for the length of the minimum conduction time.

8. The method for dynamically adjusting the minimum conduction time as described in claim 7, characterized in that, The steps for setting the minimum on-time include: The preset minimum on-time circuit uses a resistor to allow current from a certain current source to flow through it, and takes the voltage level generated at the resistor's endpoint as the minimum threshold voltage.

9. The method for dynamically adjusting the minimum conduction time as described in claim 7, characterized in that, The extracted power sensing circuit determines the amount of power extracted by detecting the inductor current flowing through the output inductor to the load.

10. The method for dynamically adjusting the minimum conduction time as described in claim 9, characterized in that, The DC voltage is calculated based on the average value of the inductor current and the DC resistance of the output inductor, and the amount of extracted electrical energy is determined based on the DC voltage.

11. The method for dynamically adjusting the minimum conduction time as described in claim 10, characterized in that, The current value of one of the compensation current sources is the product of the voltage difference between a node voltage between the energy storage switch and the output inductor and a voltage divider of the output voltage, and a conductance ratio.

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