An adaptive slope compensation method and circuit for a multiphase control circuit

Abstract

The application discloses an adaptive slope compensation method and circuit of a multiphase control circuit, and is characterized in that the method comprises the following steps: step 1, setting a slope compensation time limit of a slope compensation unit in the multiphase control circuit based on a power supply voltage of the multiphase control circuit, a load limit of an inductance current sampling signal, a turn-on slope of an upper power tube and a turn-on slope of the slope compensation unit; and step 2, realizing feedback control of the multiphase control circuit by using the slope compensation time limit and a pulse width modulation signal together. The circuit of the application comprises a slope compensation delay unit, an AND gate, a NOT gate, a switch tube, a compensation capacitor, a bias current source, a voltage-controlled current source, a resistor and a superposition circuit, and is used for realizing the adaptive slope compensation method. The application can prevent a too large difference of control signals in adjacent phases in the circuit by adjusting the highest compensation time of the slope compensation in each cycle, so that the stability of the whole system is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of integrated circuits, and more particularly, to an adaptive slope compensation method and circuit for a multiphase control circuit. BACKGROUND

[0002] A multiphase voltage converter is usually composed of a group of parallel power stage devices, and each phase has an independent inductor and power device to achieve independent voltage control. After the combination of multiple phases, it is called multiphase. Through the parallel connection of multiple phases, each phase is switched at equal intervals and performs the corresponding voltage conversion function. Compared with ordinary single-phase voltage converters, multiphase voltage converters can reduce the output capacitance, improve the thermal performance and efficiency of the circuit under large load current conditions, and improve the overshoot and undershoot of the output during the load transient process, thus having good output characteristics and being widely used. In addition, in order to prevent sub-harmonic oscillation problems, an independent slope compensation circuit can also be configured for each phase.

[0003] However, for a multiphase voltage converter with a slope compensation circuit, there is often a problem that the sum of the slope compensation slope and the slope provided by the upper power tube in the current phase is too high, and the power supply voltage is not sufficient to provide such a high fast compensation, which makes the transient response exhibited by the circuit unable to meet the design index requirements. At the same time, the circuit of the next phase is also controlled by the pulse width modulation signal in the current phase, which makes it difficult to match the outputs of the slope compensation signals in two adjacent phases, and the actual switching times of the upper and lower power tubes in two adjacent phases are misaligned, the time difference between the switching periods exceeds a fixed period, resulting in the loss of stability of the entire system.

[0004] In view of the above problems, the present application provides an adaptive slope compensation method and circuit for a multiphase control circuit. SUMMARY

[0005] In order to solve the problems existing in the prior art, the present application provides an adaptive slope compensation method and circuit for a multiphase control circuit, which adjusts the maximum compensation time of the slope compensation in each period to prevent the difference between the control signals in adjacent phases in the circuit from being too large, and ensures the stability of the entire system.

[0006] The present application adopts the following technical solutions.

[0007] The first aspect of the present application relates to an adaptive slope compensation method for a multiphase control circuit, the method comprising the following steps: step 1, setting a slope compensation time limit of a slope compensation unit in the multiphase control circuit based on a power supply voltage of the multiphase control circuit, a load limit of an inductor current sampling signal, a turn-on slope of an upper power transistor, and a turn-on slope of the slope compensation unit; and step 2, using the slope compensation time limit and a pulse width modulation signal to realize feedback control of the multiphase control circuit.

[0008] Preferably,

[0009] wherein T is the slope compensation time limit,

[0010] k S1_i is the turn-on slope of the upper power transistor in the i-th phase, determined by an inductance value L i in the i-th phase, i a sampling resistor R

[0011] k ramp_i is the turn-on slope of the slope compensation unit in the i-th phase, determined by a bias current I bias of a bias current source in the i-th phase, i a capacitance value C

[0012] V CS_load_max is a maximum DC value of the inductor current sampling signal, determined by a maximum value of a current I LOAD

[0013] V dd is a power supply voltage of the multiphase control circuit,

[0014] V dsat is a saturation drain-source voltage for maintaining a saturation state of a charging current source.

[0015] Preferably, the slope compensation time limit is an integer multiple of a switching frequency of the upper and lower power transistors in the multiphase control circuit.

[0016] In the second aspect of the present application, the adaptive slope compensation circuit of the multiphase control circuit comprises a slope compensation delay unit, an AND gate, a NOT gate, a switch tube, a compensation capacitor, a bias current source, a voltage-controlled current source, a resistor and a superposition circuit; wherein the first input end of the slope compensation delay unit is connected with the pulse width modulation signal of the i-th phase in the multiphase control circuit, the second input end is connected with a clock signal, and the output end is connected with the second input end of the AND gate; the first input end of the AND gate is connected with the pulse width modulation signal of the i-th phase in the multiphase control circuit, and the output end is connected with the input end of the NOT gate; the input end of the NOT gate is connected with the gate of the switch tube, the source-drain electrode of the switch tube is connected in parallel across the compensation capacitor, one end of the compensation capacitor is connected to the power supply voltage through the bias current source, and the other end is connected to the ground; the connection point of the bias current source and the compensation capacitor is connected to the non-inverting input end of the voltage-controlled current source, the inverting input end of the voltage-controlled current source is connected to the ground, and the output end is connected to the first input end of the superposition circuit through the resistor; the second input end of the superposition circuit is connected with the inductance current peak sampling signal VCS_i of the i-th phase, and the output end generates the feedback control signal of the i-th phase.

[0017] The present application has the advantages that, compared with the prior art, the adaptive slope compensation method and circuit of the multiphase control circuit can prevent the difference between the control signals in adjacent phases from being too large by adjusting the highest compensation time in each period, thereby ensuring the stability of the entire system. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a circuit structure schematic diagram of a multiphase control circuit in the prior art;

[0019] Figure 2 FIG. 2 is a circuit structure schematic diagram of a slope compensation unit in the multiphase control circuit in the prior art;

[0020] Figure 3 FIG. 3 is a compensation control signal output timing diagram provided by the slope compensation unit in the multiphase control circuit in the prior art;

[0021] Figure 4 FIG. 4 is a structure schematic diagram of the adaptive slope compensation circuit of the multiphase control circuit in the present application;

[0022] Figure 5 FIG. 5 is a compensation control signal output timing diagram provided by the adaptive slope compensation circuit of the multiphase control circuit in the present application. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0024] Figure 1 This is a schematic diagram of the circuit structure of a multiphase control circuit in the prior art. For example... Figure 1 As shown, the structure of the multiphase control circuit used in the prior art typically includes multiple identical control phase branches. In each branch, VIN and VOUT represent the input voltage and output voltage of the circuit, respectively; S1 and S2 represent the upper and lower power switches of each phase, respectively; signal EAO represents the error amplification signal between the feedback of signal VOUT and the reference VREF; Ri represents the inductor current sampling resistor of each phase; and ILOAD represents the external load of the system.

[0025] In this circuit, when the main phase loop is designed with adaptive turn-on or turn-off time control mode (i.e.) Figure 1 In Adaptive Off-time Control (AOT), the secondary phase loop can achieve balanced power stage energy distribution through sequential phase delay control. Taking a multiphase control system where the primary phase loop is designed with adaptive off-time control as an example, the first secondary phase will use the rising edge of the primary phase PWM (Pulse Width Modulation) pulse as the clock signal to turn on the upper power transistor and turn off the lower power transistor, and compare whether its own inductor current peak reaches the error amplification signal between the system output voltage feedback and the output voltage reference. If the inductor current peak in the first secondary phase reaches the target, it will switch the transistor state to turn off the upper power transistor and turn on the lower power transistor, thus completing the loop adjustment for each cycle. Similarly, the (i+1)th secondary phase will also control each cycle with the rising edge of the PWM pulse of the ith secondary phase and the comparison signal between its own peak current and the error output to stabilize the current phase loop.

[0026] Based on the above principle, all sub-phases except the main phase follow the peak current mode control mode. Therefore, each phase loop needs to introduce a slope compensation circuit to avoid subharmonic oscillations when the system is used with a duty cycle greater than 50%, while maintaining the energy balance of the power stage.

[0027] Figure 2 This is a schematic diagram of the circuit structure of a slope compensation unit in a multiphase control circuit in the prior art. Figure 2As shown, in the conventional multi-phase control system compensation ramp generation circuit, signal PWM_i is the pulse width modulation signal of the current main phase or auxiliary phase, signal VCS_i is the inductor current peak value sampling signal of the current main phase or auxiliary phase, signal VSUM_i is the signal after VCS_i superimposes the compensation ramp, and i represents the phase order corresponding to the current PWM signal.

[0028] For the ramp compensation unit, signal IBIAS is a fixed bias current generated by the system bias circuit. In each switching period of the i-th phase, if signal PWM_i is flipped from low to high, upper power tube S1_i is turned on and lower power tube S2_i is turned off. At this time, signal PWM_i drives switch tube M to be turned off, signal IBIAS charges capacitor C, and a ramp voltage signal VRAMP_i is generated on the upper plate of capacitor C and input to voltage-controlled current source VCCS, where G1 is the gain of voltage-controlled current source VCCS. Voltage-controlled current source VCCS converts signal VRAMP_i into ramp current signal IRAMP_i, so that signal IRAMP_i can be superimposed with signal VCS_i through resistor R to generate signal VSUM_i.

[0029] Figure 3 A compensation control signal output timing diagram is provided for a ramp compensation unit in a multi-phase control circuit in the prior art. As shown, Figure 3 When the applied load ILOAD of the system is switched from light load to heavy load, signal EAO will surge according to the drop of system output voltage VOUT. Under this condition, the phase loop under high duty cycle application will experience a long time of upper power tube S1 being turned on.

[0030] In the process of signal VCSi following the long-time rise of inductor current ILi, the ramp signal VRAMP_i superimposed on it will be distorted due to the voltage margin limitation of module circuit power supply voltage VCC, so that the slope of signal VSUM_i is lower than the sum of the slopes of signal VCSi and signal VRAMP_i. From Figure 3As can be seen from the figure, due to the distortion of the signal VRAMP_i, the slope of the signal VSUM_i in the rising process on the EAO is difficult to keep consistent with the slope of the signal VSUM_i+1. When the signal VSUM_i reaches the signal EAO, so that the upper power tube S1_i is turned off and the lower power tube S2_i is turned on, the signal VSUM_i+1 is still in the rising process, then the signal VSUM_i+1 needs to wait for a fixed delay when the signal VSUM_i is at the moment when the falling process ends, that is, when the signal VSUM_i reaches the valley value. In this adjustment process, the signal VCS_i+1 deviates from VCS_i in the vertical direction, that is, in the inductance current, ILi and ILi+1 present different DC levels, and the difference in the amount will reach a stable state respectively as the loop adjustment proceeds.

[0031] In Figure 3 the signal VSUM_i+1 in each switching period of the rising process will miss the valley delay of the signal VSUM_i+1, so that the switching period of the signal PWM_i+1 is finally maintained at twice the switching period of the signal PWM_i. As can be seen, the traditional slope generation circuit applied to the multi-phase control system is prone to cause more than one “stable” state to appear when the system has a transient response, thereby causing the stability of the entire system to lose control.

[0032] In other words, in the multi-phase control circuit, if the system is in a non-stable adjustment state, such as when a load transient response occurs, even if the rising slope of the current remains constant, the slope of the inductance current sampling signal after the slope compensation is still prone to lose control. When the slopes of two adjacent phases are charged for a long time, limited by the module power supply voltage margin, after being superimposed on the respective inductance current sampling signals, the compensation effect presented deviates from the design value and interferes with the original regulation mode of the loop, which has an adverse effect on the stability of the system. Therefore, the present application proposes an adaptive slope compensation technology for a multi-phase control circuit.

[0033] Figure 4 The present application is a structure diagram of an adaptive slope compensation circuit for a multi-phase control circuit. As Figure 4 shown, an adaptive slope compensation method for a multi-phase control circuit, the method comprising the following steps: step 1, setting the slope compensation time limit of the slope compensation unit in the multi-phase control circuit based on the power supply voltage of the multi-phase control circuit, the load limit of the inductance current sampling signal, the conduction slope of the upper power tube, and the conduction slope of the slope compensation unit; step 2, using the slope compensation time limit and the pulse width modulation signal to realize feedback control of the multi-phase control circuit.

[0034] It can be understood that the method in the application first designs the slope compensation time limit in order to fully ensure that the compensated phase control signals will not exceed the limit of the power supply voltage to provide instantaneous energy. In other words, in order to make the voltage rise amplitude of a single phase in the actual working process of the circuit consistent with the sum of the voltage rise amplitude generated by the upper power tube and the voltage rise amplitude generated by the slope compensation unit during design, the time length of the slope compensation unit for slope compensation is limited. After the time length is limited, there is no problem that the slope compensation can theoretically continuously output, but due to the limitation of the power supply voltage, the actual slope of the feedback voltage in the circuit cannot reach the preset index.

[0035] It should be noted that the turn-on slope of the upper power tube and the turn-on slope of the slope compensation unit are circuit design indexes defined in the application, which are actually respectively used to represent the rising speed of the inductor peak current to the voltage size of the inductor current sampling signal VCS and the rising speed of the slope compensation unit to the voltage size of the voltage VSUM. Since the rising speed of the above two voltages will determine the length of time for the signal to reach EAO and realize the state flip of the upper and lower power tubes, the application names it as the turn-on slope. The adjustment method of the above index and the related parameters for determining the size of the index value will be specifically defined and explained below.

[0036] In addition, the load limit of the inductor current sampling signal can be determined according to the size of the load connected to the rear stage of the circuit. When the load is fixed, the maximum value of VCS generated by the maximum load current that the load can achieve. Since it affects the initial value of VCS voltage in realizing the sawtooth fluctuation, the range of the turn-on slope value is also affected.

[0037] Preferably, wherein T is the slope compensation time limit, k S1_i is the turn-on slope of the upper power tube in the i-th phase, which is determined by the inductance L i , the sampling resistance R i in the i-th phase, ramp_i is the turn-on slope of the slope compensation unit in the i-th phase, which is determined by the current I bias of the bias current source and the capacitance value C i of the compensation capacitor in the i-th phase, CS_load_max is the inductor current sampling threshold, which is the DC value of VCS when the current external load ILOAD reaches the maximum value, V dd is the power supply voltage of the multi-phase control circuit, V dsat is the saturation drain-source voltage for maintaining the saturation state of the charging current source.

[0038] It can be understood that in the circuit, if the upper power tube is in the on state and the lower power tube is in the off state without generating slope compensation, the inductor current sampling voltage in the phase loop will gradually increase with the change of the inductor current under the action of the inductor of the current phase, showing a state of rising at a fixed slope. At this time, the slope in the application is referred to as the on slope of the upper power tube.

[0039] In addition, when slope compensation occurs, the current IRAMP_i generated by the slope compensation unit will also cause the voltage to gradually rise. The rising rate of the voltage caused by the slope compensation unit alone in a unit time is referred to as the on slope of the slope compensation unit. Both of the above-mentioned slopes can be calculated according to the parameters of the related elements in the circuit.

[0040] Therefore, after obtaining the two slope indicators in the application, the longest time of the slope compensation unit in a single compensation process can be limited according to the size of the power supply voltage to ensure that the voltage will not rise infinitely to a state exceeding the power supply voltage.

[0041] In addition, the charging current source is a current source for charging the capacitor in the slope compensation delay unit. In order to maintain the saturation state of the corresponding MOS tube in the current source, a source-drain voltage of the above-mentioned MOS tube needs to be provided. The value is usually 200-300mV.

[0042] Preferably, the slope compensation is limited to the reciprocal of the switching frequency of the upper and lower power tubes in the multi-phase control circuit in the steady state.

[0043] The delay unit DLY_RAMP_CLR mentioned below can determine the duration of the signal VRAMP from the start of charging to the time of being cleared, and the time can be adaptively adjusted according to the switching frequency of the current system. For example, when the steady-state switching frequency of the system is set to FSW, the delay time is calculated as K*1 / FSW, wherein K is a pre-designed fixed proportion coefficient, which can be a positive integer. In an embodiment of the application, the value of K is 1.

[0044] A second aspect of this invention relates to an adaptive slope compensation circuit for a multiphase control circuit. The circuit includes a slope compensation delay unit, an AND gate, a NOT gate, a switching transistor, a compensation capacitor, a bias current source, a voltage-controlled current source, a resistor, and a superposition circuit. The first input terminal of the slope compensation delay unit is connected to the pulse width modulation signal of the i-th phase in the multiphase control circuit, the second input terminal is connected to a clock signal, and the output terminal is connected to the second input terminal of the AND gate. The first input terminal of the AND gate is connected to the pulse width modulation signal of the i-th phase in the multiphase control circuit, and the output terminal is connected to the second input terminal of the NOT gate. The input terminals are connected as follows: the input terminal of the NOT gate is connected to the gate of the switching transistor, the source and drain of the switching transistor are connected in parallel across the two ends of the compensation capacitor, one end of the compensation capacitor is connected to the power supply voltage through a bias current source, and the other end is grounded; the connection point between the bias current source and the compensation capacitor is connected to the positive input terminal of the voltage-controlled current source, the negative input terminal of the voltage-controlled current source is grounded, and the output terminal is connected to the first input terminal of the superposition circuit after passing through a resistor; the second input terminal of the superposition circuit is connected to the peak sampling signal VCS_i of the inductor current of the i-th phase, and the output terminal generates the feedback control signal of the i-th phase.

[0045] Figure 5 This is a timing diagram of the compensation control signal output for an adaptive slope compensation circuit in a multiphase control circuit of the present invention. (See diagram below.) Figure 5 As shown, in this circuit, the single compensation time of the slope compensation circuit is limited to a fixed time.

[0046] In traditional slope compensation circuits, for the i-th phase loop of a multiphase control system, the signal VRAMP_i superimposed on the signal VSC_i is only cleared when the signal PWM_i goes low. However, the adaptive slope compensation circuit ensures that the signal VRAMP_i only provides superimposed compensation within a set time. The slope of the compensated signal VSUM_i is controllable within this time, equal to the sum of the slopes of the signals VCSi and VRAMP_i. This avoids the loss of control over the slope of the signal VSUM_i due to VRAMP_i being distorted from prolonged charging when the current phase is in a prolonged on-state operation, such as during load transient responses, which could compromise the overall system stability.

[0047] Preferably, the ramp signal VRAMP_i is continuously charged for only one steady-state cycle after PWM_i turns high, and is superimposed on the signal VCS_i. During the operating cycle of the current phase loop when the upper power transistor S1_i is on for a long time, the signals VSUM_i and VSUM_i+1 will return to the VCS_i and VCS_i+1 signals respectively after reaching the steady-state cycle, that is, they maintain the same rising slope until they reach the signal EAO and then turn on the lower power transistor S2_i.

[0048] In the subsequent voltage stabilization process, since the signal VRAMP does not superimpose infinitely with the opening time of the upper power tube S1_i, even if the signal VCS_i+1 deviates from the signal VCS_i in direct current during the transient response process, the loop can be adjusted cycle by cycle, so that they enter the same stable state.

[0049] When the loop of the multiphase control system is adjusted to a stable state, since the opening time of the upper power tube S1 will not exceed one switching cycle time, the time when the signal VCS of each phase rises to the signal EAO in each switching cycle is kept the same superimposed slope, thereby ensuring the stability of the overall system, i.e. all phases are in the same stable state.

[0050] The beneficial effects of the present application are that, compared with the prior art, the adaptive slope compensation method and circuit of a multiphase control circuit in the present application can prevent the difference between the control signals in adjacent phases from being too large by adjusting the highest compensation time in each cycle, thereby ensuring the stability of the entire system.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can still be modified or replaced by equivalents without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered within the protection scope of the claims of the present application.

Claims

1. An adaptive slope compensation method for a multiphase control circuit, characterized in that, The method includes the following steps: Step 1: Based on the power supply voltage of the multiphase control circuit, the load limit of the inductor current sampling signal, the conduction slope of the upper power transistor, and the conduction slope of the slope compensation unit, set the slope compensation time limit of the slope compensation unit in the multiphase control circuit, specifically as follows: Where T is the slope compensation time limit. k S1_i Let L be the conduction slope of the upper power transistor in phase i, and let L be the inductance value in phase i. i Sampling resistor R i Sure, k ramp_i The conduction slope of the slope compensation unit in the i-th phase is given by the current I of the bias current source in the i-th phase. bias The capacitance value C of the compensation capacitor i Sure, V CS_load_max The maximum DC value of the inductor current sampling signal is determined by the maximum value of the current applied load ILOAD. V dd The power supply voltage of the multiphase control circuit is... V dsat To maintain the saturation drain-source voltage of the charging current source in saturation state; Step 2: The slope compensation time limit and pulse width modulation signal are used together to realize feedback control of the multiphase control circuit.

2. The adaptive slope compensation method for a multiphase control circuit according to claim 1, characterized in that: The slope compensation time limit is an integer multiple of the reciprocal of the switching frequency of the upper and lower power transistors in the multiphase control circuit.

3. An adaptive slope compensation circuit for a multiphase control circuit using the adaptive slope compensation method according to any one of claims 1-2, characterized in that: The circuit includes a ramp compensation delay unit, AND gates, NOT gates, switching transistors, compensation capacitors, bias current sources, voltage-controlled current sources, resistors, and a superposition circuit; wherein... The first input terminal of the ramp compensation delay unit is connected to the pulse width modulation signal of the i-th phase in the multiphase control circuit, the second input terminal is connected to the clock signal, and the output terminal is connected to the second input terminal of the AND gate. The first input terminal of the AND gate is connected to the pulse width modulation signal of the i-th phase in the multiphase control circuit, and the output terminal is connected to the input terminal of the NOT gate. The input terminal of the NOT gate is connected to the gate of the switching transistor. The source and drain of the switching transistor are connected in parallel across the two ends of the compensation capacitor. One end of the compensation capacitor is connected to the power supply voltage through the bias current source, and the other end is grounded. The connection point of the bias current source and the compensation capacitor is connected to the positive input terminal of the voltage-controlled current source, the negative input terminal of the voltage-controlled current source is grounded, and the output terminal is connected to the first input terminal of the superposition circuit after passing through the resistor. The second input terminal of the superposition circuit is connected to the peak sampling signal VCS_i of the inductor current of the i-th phase, and the output terminal generates the feedback control signal of the i-th phase.

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