Conversion circuit and its autonomous transient recovery method

Abstract

A conversion circuit with autonomous transient recovery, and the conversion circuit includes a power output stage and a controller. When the controller determines that the operation mode of the power output stage is operated in a continuous conduction mode, and the output voltage is higher than an upper voltage limit, the controller operates the power output stage in a forced continuous conduction mode, and in the forced continuous conduction mode, the controller controls the second switch to be continuously on until the inductor current drops to a negative lower limit, and then controls the first switch and the second switch to be alternately on and off to maintain the inductor current in a predetermined range, so as to consume a large amount of energy through negative current.

Description

Technical Field

[0001] This invention relates to a conversion circuit and its operating method, and more particularly to a conversion circuit with autonomous instantaneous recovery and its autonomous instantaneous recovery method. Background Technology

[0002] Due to the rapid development of the information industry in recent years, power supplies play a crucial role, especially as the power requirements of large-scale information equipment have gradually increased. Consequently, the output power of power supplies has also increased to meet load demands. The main circuitry within a power supply that performs power conversion is the switching circuit. The switching circuit primarily functions to convert input power into output power, providing a stable output voltage to supply the load. The switching circuit typically contains several switches and at least one power inductor. An internal controller controls the switches to alternately turn on and off, allowing the power inductor to store and release energy, thereby controlling the switching circuit to convert the input voltage into the output voltage. The conventional operating mode of the switching circuit is as follows: when the load is heavy, the controller typically operates the switching circuit in continuous conduction mode (CCM); conversely, when the load is light, the controller typically operates the switching circuit in discontinuous conduction mode (DCM).

[0003] However, as Figure 1A As shown, when the load rapidly decreases from heavy load to light load or no load, the output voltage Vo rises, and the inductor current Il begins to decrease, allowing energy to be released. However, once the inductor current Il drops to 0, excess energy cannot be released, causing the output voltage Vo to decrease only slowly. This results in a slow instantaneous response of the switching circuit and an excessively long recovery time to steady state. Therefore, existing solutions include... Figure 1B As shown, by using the external bypass circuit CB composed of the error amplifier and the switch, when the output voltage Vo is too high, the excess energy can be released by turning on the switch.

[0004] However, this solution is limited by the accuracy and response speed of the error amplifier. Regarding accuracy, the input of the error amplifier must accurately reflect the received voltage; otherwise, voltage comparison will be misaligned, triggering the switch too early or too late. Regarding response speed, the error amplifier needs a high response rate; otherwise, a slow response will result in the switch being triggered too late. Furthermore, the energy release rate depends on the switch specifications. To achieve rapid energy release, the switch specifications must be improved to withstand larger currents. Therefore, existing technologies cannot reduce circuit specifications and costs.

[0005] Therefore, how to design a conversion circuit and its autonomous instantaneous recovery method so that when the load drops rapidly from heavy load to light load or no load, a large amount of energy can be effectively consumed without the use of an external bypass circuit is a major research topic of this invention. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a conversion circuit with autonomous instantaneous recovery to overcome the limitations of existing technologies. Therefore, the conversion circuit of this invention receives an input voltage at an input node and converts the input voltage to provide an output voltage at an output node. The conversion circuit includes a power output stage and a controller, and the power output stage includes a power inductor, a first switch, and a second switch. The power output stage is coupled between the input node and the output node, and the power inductor, the first switch, and the second switch are all connected at the midpoint of the power output stage. The controller is coupled to the first switch and the second switch and controls the first switch and the second switch to alternately turn on and off, thereby controlling the power inductor to generate inductor current. The controller operates the power output stage in one of three modes: continuous conduction mode, discontinuous conduction mode, and forced continuous conduction mode, and sets a negative lower limit value for the inductor current. Specifically, when the controller determines that the power output stage is operating in continuous conduction mode and the output voltage is higher than the upper voltage limit, the controller will operate the power output stage in forced continuous conduction mode. In forced continuous conduction mode, the controller keeps the second switch continuously on until the inductor current drops to the negative lower limit. Then, the controller will control the first and second switches to alternately turn on and off to maintain the inductor current within a predetermined range. When the controller determines that the output voltage is lower than the lower voltage limit, the controller will switch the power output stage from forced continuous conduction mode to one of continuous conduction mode or discontinuous conduction mode.

[0007] To address the aforementioned problems, this invention provides an autonomous instantaneous recovery method for a conversion circuit, overcoming the limitations of existing technologies. Therefore, the conversion circuit of this invention includes a power output stage, which comprises a power inductor, a first switch, and a second switch. The autonomous instantaneous recovery method includes the following steps: (a) controlling the first and second switches to alternately turn on and off to control the power inductor to generate inductor current. (b) determining that the power output stage operates in a continuous conduction mode and that the output voltage is higher than the upper voltage limit. (c) operating the power output stage in a forced continuous conduction mode, and in this mode, controlling the second switch to remain continuously on until the inductor current drops to a negative lower limit, then controlling the first and second switches to alternately turn on and off to maintain the inductor current within a predetermined range. (d) determining that the output voltage is lower than the lower voltage limit. (e) switching the power output stage from the forced continuous conduction mode to one of a continuous conduction mode or a discontinuous conduction mode.

[0008] The main objective and effect of this invention is that, when the load rapidly decreases from heavy load to light load or no load, the controller of this invention operates the inductor current in a forced continuous conduction mode with a negative value, thereby consuming a large amount of energy through the negative current, so as to achieve the effect of rapidly reducing the output voltage to a predetermined level.

[0009] 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

[0010] Figure 1A A waveform diagram of an existing conversion circuit;

[0011] Figure 1B A circuit block diagram of an existing instantaneous recovery conversion circuit;

[0012] Figure 2A This is a circuit block diagram of the conversion circuit with autonomous instantaneous recovery according to the present invention;

[0013] Figure 2B This is a circuit block diagram of the controller of the present invention;

[0014] Figure 3A This is a circuit block diagram of the energy detection circuit of the present invention;

[0015] Figure 3B This is a circuit block diagram of the pattern detection circuit of the present invention;

[0016] Figure 3C This is a schematic diagram of the logic circuit of the present invention.

[0017] Figure 4 This is a waveform diagram of the conversion circuit with autonomous instantaneous recovery according to the present invention; and

[0018] Figure 5 This is a flowchart of the autonomous instantaneous recovery method for the conversion circuit.

[0019] In the attached figures, the following labels are used:

[0020] CB: Bypass circuit

[0021] 100: Conversion circuit

[0022] 100-1: Input Node

[0023] 100-2: Output Node

[0024] 1: Power Output Stage

[0025] L: Power inductor

[0026] Q1: First switch

[0027] Q2: Second switch

[0028] SW: Midpoint of power output stage

[0029] Co: Output capacitor

[0030] 2: Drive circuit

[0031] 3: Controller

[0032] 30: Main control circuit

[0033] 302: Pulse Width Modulator

[0034] 304: Feedback Circuit

[0035] R1, R2: Voltage divider circuit

[0036] OP: Error Amplifier

[0037] Ci: Integrating circuit

[0038] 32: Instantaneous control loop

[0039] 320: Energy Detection Circuit

[0040] Ccp: Potential clamping circuit

[0041] Cc: Comparator circuit

[0042] limit_L: Lower limit value

[0043] 322: Pattern Detection Circuit

[0044] 324: Logic Circuits

[0045] 200: Load

[0046] Vin: Input voltage

[0047] Vo: Output voltage

[0048] Vfb: Feedback voltage

[0049] Vref: Reference voltage

[0050] Ve: Error amount

[0051] VL: Lower voltage limit

[0052] VH: Upper limit of voltage

[0053] Il: Inductor current

[0054] limit_N: Negative lower limit value

[0055] Sc1, Sc2: Control signals

[0056] PWM: Pulse Width Modulation Signal

[0057] Hiz-Release: Forced On Signal

[0058] HiZ: High impedance signal

[0059] DTY: Energy Demand Signal

[0060] ClampL: Energy Excess Signal

[0061] Mode: Mode indicator signal

[0062] Se: Error signal

[0063] CCM: Continuous On Mode

[0064] DCM: Discontinuous conduction mode

[0065] Force-CCM: Forced Continuous On Mode

[0066] t1~t5: Time

[0067] R: Pre-defined interval

[0068] (S100)~(S600): Steps Detailed Implementation

[0069] The structural and working principles of the present invention will be described in detail below with reference to the accompanying drawings:

[0070] Please see Figure 2A This is a circuit block diagram of the conversion circuit with autonomous instantaneous recovery of the present invention, which can be further referenced. Figures 1A-1B The conversion circuit 100 includes an input node 100-1 and an output node 100-2, with the output node 100-2 coupled to a load 200. The conversion circuit 100 receives an input voltage Vin from the input node 100-1 and converts the input voltage Vin into an output voltage Vo, which is then supplied to the load 200 via the output node 100-2. The conversion circuit 100 includes a power output stage 1, a drive circuit 2, and a controller 3, with the power output stage 1 coupled between the input node 100-1 and the output node 100-2. The power output stage 1 includes a power inductor L, a first switch Q1, a second switch Q2, and an output capacitor Co, with the power inductor L, the first switch Q1, and the second switch Q2 all connected at the midpoint SW of the power output stage. Taking the conversion circuit 100 as an example of a buck converter circuit architecture, the first switch Q1 is coupled to the input node 100-1, and the output capacitor Co is coupled to the output node 100-2.

[0071] The drive circuit 2 is coupled to the first switch Q1 and the second switch Q2, and the controller 3 is coupled to the drive circuit 2. The controller 3 provides a pulse width modulation (PWM) signal to the drive circuit 2, and the drive circuit 2 provides control signals Sc1 and Sc2 based on the PWM signal to control the first switch Q1 and the second switch Q2 respectively, so that the first switch Q1 and the second switch Q2 are alternately turned on and off, thereby controlling the power inductor L to generate an inductor current Il. The power output stage 1 charges / discharges the output capacitor Co through the generation of the inductor current Il, thereby adjusting the output voltage Vo supplied to the output node 100-2. The controller 3 can be an analog control circuit composed of electronic components, a programmable controller controlled by software, or a controller with signal processing and calculation functions such as a microcontroller or a central processing unit.

[0072] The controller 3 is further coupled to the output node 100-2 to adjust the pulse width modulation signal (PWM) based on feedback from the output voltage Vo, and to maintain the stability of the output voltage Vo by adjusting the PWM. The controller 3 further adjusts the operating mode of the power output stage based on the magnitude of the load 200, and the operating modes provided by the controller 3 include at least continuous conduction mode (CCM), discontinuous conduction mode (DCM), and forced continuous conduction mode (Force-CCM). The magnitude of the load 200 can be determined, for example, but not limited to, the current of the output node 100-2, the inductor current Il, the current flowing through switches Q1 and Q2, or the current of the input node 100-1. When the load 200 is large (e.g., but not limited to medium load or heavy load), the controller 3 typically operates the power output stage 1 in continuous conduction mode (CCM) by adjusting the PWM. Conversely, when the load 200 is relatively small (e.g., but not limited to no load or light load), the controller 3 typically operates the power output stage 1 in discontinuous conduction mode (DCM) by adjusting the pulse width modulation signal PWM.

[0073] Because when the load decreases rapidly (e.g., from heavy load to light load or no load), the output capacitor Co may temporarily store a large amount of energy that cannot be released quickly, resulting in a situation similar to... Figure 1AIn this case, the output voltage Vo is too high and cannot drop to the predetermined normal level in a short time. Therefore, the main objective and effect of this invention is that when the load 200 rapidly decreases from heavy load to light load or no load, the controller 3 dissipates a large amount of energy through the negative current by operating the inductor current Il in a forced continuous conduction mode (Force-CCM), so that the output voltage Vo can quickly drop to the predetermined level. Specifically, the controller 3 sets a negative lower limit value for the inductor current Il. When the controller 3 determines that the power output stage 1 was originally operating in continuous conduction mode (CCM) and the output voltage Vo is higher than the preset upper voltage limit value at a certain point in time, the controller 3 operates the power output stage 1 in forced continuous conduction mode (Force-CCM).

[0074] In Force-CCM, step (1): Controller 3 first controls the first switch Q1 to remain off and the second switch Q2 to remain on until the inductor current Il drops to the negative lower limit. Step (2): After the inductor current Il drops to the negative lower limit, for a preset period of time, controller 3 keeps the first switch Q1 on and the second switch Q2 off. When the preset period of time ends, controller 3 executes steps (1) and (2) again in sequence. In this way, controller 3 controls the first switch Q1 and the second switch Q2 to be turned on and off alternately to maintain the inductor current Il in a predetermined range associated with the negative lower limit. Finally, when controller 3 determines that the output voltage Vo has dropped from above the upper voltage limit to below the lower voltage limit, controller 3 switches the power output stage 1 from Force-CCM to CCM or DCM by adjusting the pulse width modulation signal PWM to make the inductor current Il rise from negative to 0. It is worth mentioning that, in one embodiment of the present invention, the upper voltage limit and the lower voltage limit can be set to the same point or to different points. It is also worth mentioning that, in one embodiment of the present invention, the conversion circuit 100 is not limited to a buck converter architecture; any conversion circuit 100 having a continuous conduction mode (CCM) and a discontinuous conduction mode (DCM) can be included within the scope of this embodiment.

[0075] Please see Figure 2B This is a circuit block diagram of the controller of the present invention, which can be further referenced. Figure 2AThe controller 3 includes a main control loop 30 and an instantaneous control loop 32. The main control loop 30 is coupled to the output node 100-2 and the drive circuit 2, so that the pulse width modulator 302 of the main control loop 30 generates a pulse width modulation signal PWM based on the output voltage Vo, and controls the first switch Q1 and the second switch Q2 to be turned on and off alternately through the pulse width modulation signal PWM. The main control loop 30 also detects the magnitude of the inductor current Il and generates a high impedance signal HiZ based on the magnitude of the inductor current Il. The circuit design related to the high impedance signal HiZ corresponds to the logic of the high impedance signal HiZ in the discontinuous conduction mode (DCM) operation. For relevant background information, please refer to the relevant descriptions in US Patent Application US20160156268A1 or Chinese Patent Application CN105048805A.

[0076] The instantaneous control loop 32 is coupled to the main control loop 30 and determines whether the power output stage 1 is operating in discontinuous conduction mode (DCM) based on the high impedance signal HiZ, and whether the output voltage Vo is higher than the upper voltage limit VH. Based on the operating mode and the magnitude of the output voltage Vo, it provides a forced conduction signal HiZ-Release to adjust the pulse width modulation signal PWM. Thus, by adjusting the pulse width modulation signal PWM, the power output stage 1 can be operated in forced continuous conduction mode (Force-CCM).

[0077] Specifically, when power output stage 1 operates in discontinuous conduction mode (DCM), the main control circuit 30 generates a high-impedance signal HiZ based on the inductor current Il, which is related to the control of the second switch Q1 turning off, and generates an energy demand signal DTY based on the output voltage Vo. This allows the main control circuit 30 to generate a pulse width modulation (PWM) signal based on the high-impedance signal HiZ and the energy demand signal DTY. The energy demand signal DTY typically indicates that the energy stored in the output capacitor Co at the output node 100-2 of the conversion circuit 100 has been significantly consumed by the load, resulting in insufficient output voltage Vo, requiring replenishment using the input voltage Vin. Therefore, the energy demand signal DTY typically indicates the turn-on time of the first switch Q1.

[0078] The high-impedance signal HiZ is typically used to indicate whether the inductor current Il has reached 0. When the high-impedance signal HiZ is 1 at the end of the previous switching cycle, it means that the switching circuit 100 operated in discontinuous conduction mode (DCM) in the previous cycle. When the high-impedance signal HiZ is 0 at the end of the previous switching cycle, it means that the switching circuit 100 operated in continuous conduction mode (CCM) in the previous cycle.

[0079] The instantaneous control loop 32 provides a forced turn-on signal Hiz-Release based on the high impedance signal HiZ and the energy demand signal DTY, so as to control the power output stage 1 to operate in the forced continuous conduction mode Force-CCM by adjusting the pulse width modulation signal PWM through the forced turn-on signal Hiz-Release.

[0080] Furthermore, the instantaneous control loop 32 includes an energy detection circuit 320, a mode detection circuit 322, and a logic circuit 324. The energy detection circuit 320 is coupled to the output node 100-2 and sets a voltage upper limit value VH to generate an energy excess signal ClampL based on the output voltage Vo and the voltage upper limit value VH. The energy excess signal ClampL indicates whether the conversion circuit 100 has a large amount of energy that cannot be released. The mode detection circuit 322 is coupled to the main control loop 30 and determines the operating mode of the power output stage 1 based on the pulse width modulation signal PWM (specifically, the high impedance signal HiZ and the energy demand signal DTY), and provides a mode indication signal Mode associated with the change in operating mode. The logic circuit 324 receives the excess energy signal ClampL and the mode indication signal Mode, and generates a forced conduction signal Hiz-Release based on the excess energy signal ClampL and the mode indication signal Mode, so that the main control circuit 30 can determine whether to adjust the operation mode of the power output stage 1 to the forced continuous conduction mode Force-CCM by receiving the forced conduction signal Hiz-Release.

[0081] Please see Figure 3A This is a circuit block diagram of the energy detection circuit of the present invention, which can be further referenced. Figures 2A-2B The main control loop 30 includes a feedback circuit 304, which comprises voltage divider circuits R1 and R2, an error amplifier OP, and an integrator circuit Ci. The voltage divider circuits R1 and R2 generate a feedback voltage Vfb based on the output voltage Vo, and the error amplifier OP generates an error quantity Ve based on the feedback voltage Vfb and the reference voltage Vref. The integrator circuit Ci integrates the error quantity Ve to generate an error signal Se. The error signal Se is also processed by the subsequent internal circuitry of the main control loop 30 to generate an energy demand signal DTY. The energy detection circuit 320 further includes a potential clamping circuit Ccp and a comparator circuit Cc. The potential clamping circuit Ccp clamps the error signal Se to the lower limit value limit_L when it is below the lower limit value limit_L, thereby maintaining the operation of the error amplifier OP.

[0082] Specifically, when the error value Ve is negative, continuous integration by the integrator Ci will cause the negative value of the error signal Se to decrease. Therefore, if the negative value of the error signal Se is too low, the operating voltage received by the error amplifier OP will be too low, causing it to shut down. This means that the error amplifier OP must wait for its startup time before it can operate again, reducing the overall response time of the controller 3. Therefore, by clamping the error signal Se to the lower limit limit_L using the potential clamping circuit Ccp, the situation where the operating voltage received by the error amplifier OP is too low and forced to shut down, thus reducing the response time of the controller 3, can be avoided.

[0083] Then, the comparator circuit Cc compares the error signal Se with the value corresponding to the upper voltage limit VH to provide an energy excess signal ClampL. Therefore, when the output voltage Vo is higher than the upper voltage limit VH, the energy excess signal ClampL indicates that an energy excess condition has occurred at the output node 100-2. It is worth mentioning that, in one embodiment of the present invention, the potential clamping circuit Ccp can be constructed by circuit elements such as, but not limited to, a voltage regulator, and the comparator circuit Cc can be constructed by circuit elements such as, but not limited to, a comparator. Therefore, any circuit elements or software programs that can achieve the above functions can be included in the scope of this embodiment.

[0084] Please see Figure 3B This is a circuit block diagram of the pattern detection circuit of the present invention, which can be further referenced. Figures 2A-3A .by Figure 3B For example, the mode detection circuit 322 can be composed of, but is not limited to, logic circuits. In one embodiment, it is illustrated using a D-type flip-flop. The mode detection circuit 322 mainly determines whether the operating mode of the power output stage 1 is in discontinuous conduction mode (DCM) based on the high impedance signal HiZ, and the controller 3 mainly generates a pulse width modulation signal (PWM) based on the energy demand signal DTY. Therefore, by receiving the energy demand signal DTY and the high impedance signal HiZ through the D-type flip-flop, it can be determined whether the operating mode of the power output stage 1 in the previous switching cycle is still in continuous conduction mode (CCM), and a mode indication signal Mode is provided accordingly. It is worth mentioning that in one embodiment of the present invention, the mode detection circuit 322 is not limited to being implemented only with a D-type flip-flop. Any circuit element or software program that can achieve the above functions can be included in the scope of this embodiment.

[0085] Please see Figure 3C This is a circuit block diagram of the logic circuit of the present invention, which can be further referenced. Figures 2A-3B .by Figure 3AFor example, logic circuit 324 can be composed of, but is not limited to, logic circuits. In one embodiment, it is illustrated by an AND gate and an RS flip-flop. The AND gate generates a logic change at the output based on the excess energy signal ClampL and the mode indication signal Mode, and the RS flip-flop generates a forced conduction signal Hiz-Release based on this logic change and the energy demand signal DTY. When the excess energy signal ClampL indicates that the output node 100-2 has excess energy, and the mode indication signal Mode indicates that the power output stage 1 was operating in continuous conduction mode (CCM) in the previous switching cycle, it means that the load 200 has rapidly decreased from heavy load to light load or no load and the output voltage Vo is too high. At this time, logic circuit 324 outputs the forced conduction signal Hiz-Release, triggering controller 3 to operate the switching circuit 100 in forced continuous conduction mode (Force-CCM) to dissipate a large amount of energy through negative current. Therefore, the main control loop 30 can adjust the pulse width modulation signal PWM based on the forced conduction signal Hiz-Release to operate the power output stage 1 in the forced continuous conduction mode Force-CCM.

[0086] Please see Figure 4 This is a waveform diagram of the conversion circuit with autonomous instantaneous recovery of the present invention, which can be further referenced. Figures 2A-3C Before time t1, load 200 is under heavy load, so controller 3 controls power output stage 1 to operate in continuous conduction mode (CCM) to maintain the output voltage at a predetermined voltage (i.e., below the lower voltage limit VL). At this time, because load 200 has a large load drawdown, it is necessary to continuously replenish energy. Therefore, before the inductor current Il drops to 0, the pulse of the energy demand signal DTY for the next switching cycle is received. Conversely, because controller 3 controls power output stage 1 to operate in continuous conduction mode (CCM), the high impedance signal HiZ is low. Mode detection circuit 322 generates a high-level mode indication signal Mode based on the energy demand signal DTY and the high impedance signal HiZ, and energy detection circuit 320 generates a low-level energy excess signal ClampL based on the output voltage Vo being below the lower voltage limit VL. Logic circuit 324 generates a low-level forced conduction signal HiZ-Release based on the high-level mode indication signal Mode and the low-level energy excess signal ClampL to indicate that the operating mode does not need to be adjusted.

[0087] At time t1, the load rapidly decreases from heavy load to light load or no load, causing the output voltage Vo to rise above the upper voltage limit VH. Since the output voltage Vo rises above the upper voltage limit VH, it indicates excess energy, causing the energy demand signal DTY to go low and the excess energy signal ClampL to go high. Conversely, since the inductor current Il has not yet dropped to 0 before this instant, the high impedance signal HiZ remains low, causing the mode indicator signal Mode to remain high. Logic circuit 324 generates a high-level forced conduction signal HiZ-Release based on the high-level mode indicator signal Mode and the high-level excess energy signal ClampL, indicating that controller 3 needs to switch power output stage 1 from continuous conduction mode (CCM) to forced continuous conduction mode (Force-CCM) by adjusting the pulse width modulation signal PWM.

[0088] Between time t1 and t2, since controller 3 operates power output stage 1 in Forced Continuous Conduction Mode (Force-CCM), controller 3 first controls the first switch Q1 to remain continuously off and the second switch Q2 to remain continuously on until the inductor current Il drops to the negative lower limit value limit_N. After the inductor current Il drops to the negative lower limit value, step (1) is repeatedly executed: controller 3 controls the first switch Q1 to turn on and the second switch Q2 to turn off for a specific duration when the inductor current Il drops to the negative lower limit value limit_N, and step (2) ends at the end of the specific duration, controller 3 controls the first switch Q1 to turn off and the second switch Q2 to turn on until the inductor current Il drops to the negative lower limit value limit_N. The first switch Q1 and the second switch Q2 are thus controlled to turn on and off alternately to maintain the inductor current Il within a predetermined range R associated with the negative lower limit value limit_N. It is worth mentioning that the controller 3 can set the negative lower limit value limit_N to the lower limit of the predetermined range R to avoid the inductor current Il being too low and exceeding the tolerance specification of the conversion circuit 100. However, it is not excluded that the relationship between the predetermined range R and the negative lower limit value limit_N can be specified separately, and it is not required to be set to the lower limit of the predetermined range R.

[0089] At time t2, the output voltage Vo has fallen below the lower voltage limit VL, therefore the excess energy signal ClampL changes from high to low. Controller 3 controls the inductor current Il to move away from the predetermined range R by alternately turning the first switch Q1 and the second switch Q2 on and off. Specifically, controller 3 gradually increases the inductor current to move away from the predetermined range R by alternately turning the first switch Q1 and the second switch Q2 on and off through a specific cycle.

[0090] At time t3, the excess energy signal ClampL is at a low level, and the energy demand signal DTY pulse is received. The logic circuit 324 causes the forced conduction signal Hiz-Release to switch to a low level, and the controller 3 ends the forced continuous conduction mode Force-CCM and enters the continuous conduction mode CCM.

[0091] Between times t3 and t4, since power output stage 1 operates in continuous conduction mode (CCM) and conversion circuit 100 requires energy replenishment again, the energy demand signal DTY generates pulses periodically once more. Conversely, since the inductor current Il has not yet risen to 0 at this instant, the high impedance signal HiZ remains low, causing the mode indicator signal Mode to remain high.

[0092] At time t4, the inductor current Il has been gradually increased to 0, and since the inductor current Il is 0 after the second switch Q2 is turned off, the high impedance signal HiZ generates a pulse to indicate that the inductor current Il has reached 0, which means that the power output stage 1 was operating in discontinuous conduction mode (DCM) in the previous switching cycle.

[0093] At time t5, the energy demand signal DTY generates another pulse after the first pulse of the high impedance signal HiZ. Therefore, the mode indicator signal Mode switches to a low level to enter the steady-state discontinuous conduction mode DCM. The pulses of the energy demand signal DTY and the high impedance signal HiZ thereafter begin to have a specific periodicity (depending on the size of the load 200).

[0094] It is worth mentioning that, in one embodiment of the present invention, the controller 3 can switch the power output stage 1 from Forced Continuous Conduction Mode (Force-CCM) to one of Continuous Conduction Mode (CCM) or Discontinuous Conduction Mode (DCM). That is, the controller 3 can also control the first switch Q1 to remain on at time t3 until the inductor current Il returns directly to 0 and enters the discontinuous conduction mode (DCM) (the concept is the same as the second switch Q2 remaining on after time t1). Although this operation will cause the output voltage Vo to deviate from the predetermined voltage and rise again, it will not exceed the upper voltage limit VH. In this way, the conversion circuit 100 can quickly return to the discontinuous conduction mode (DCM).

[0095] Please see Figure 5 This is a flowchart of the autonomous instantaneous recovery method for the conversion circuit of the present invention, which can be further referenced. Figures 2A-4The autonomous instantaneous recovery method of the present invention mainly involves the conversion circuit 100 dissipating a large amount of energy through a negative current when the load 200 rapidly decreases from a heavy load to a light load or no load. This is achieved by operating the inductor current Il in a forced continuous conduction mode (Force-CCM) with a negative value, allowing the output voltage Vo to rapidly drop to a predetermined level. Therefore, the autonomous instantaneous recovery method of the conversion circuit 100 includes controlling the first switch and the second switch to alternately turn on and off to control the power inductor to generate inductor current (S100). A preferred embodiment utilizes the controller 3 to provide a pulse width modulation (PWM) signal to the drive circuit 2, and the drive circuit 2, based on the PWM signal, provides control signals Sc1 and Sc2 to control the first switch Q1 and the second switch Q2 to alternately turn on and off to control the power inductor L to generate inductor current Il.

[0096] Then, it is determined that the power output stage operates in continuous conduction mode (CCM) and the output voltage is higher than the upper voltage limit (S200). A preferred embodiment uses the controller 3 to detect, for example, but not limited to, the voltage / current at output node 100-2, power inductor L, switches Q1 and Q2, or input node 100-1 to determine the operating mode of the power output stage 1 and the magnitude of the output voltage Vo. Then, when the controller 3 determines that the power output stage 1 operates in continuous conduction mode (CCM) and the output voltage Vo is higher than the upper voltage limit VH, the power output stage is operated in forced continuous conduction mode. In forced continuous conduction mode, the second switch is controlled to remain on until the inductor current drops to the negative lower limit (S300). A preferred embodiment uses the controller 3 to control the first switch Q1 to remain off and the second switch Q2 to remain on until the inductor current Il drops to the negative lower limit limit_N.

[0097] Then, the first switch and the second switch are alternately turned on and off to maintain the inductor current within a predetermined range (S400). In a preferred embodiment, when the inductor current Il drops to the negative lower limit limit_N, the controller 3 controls the first switch Q1 and the second switch Q2 to alternately turn on and off to maintain the inductor current Il within a predetermined range R associated with the negative lower limit limit_N. This allows a large amount of energy to be consumed through the negative current. Then, it is determined that the output voltage is below the voltage lower limit (S500). In a preferred embodiment, when the controller 3 determines that the output voltage Vo is below the voltage lower limit VL, it indicates that a large amount of energy has been released. Therefore, the controller 3 can switch the power output stage from the forced continuous conduction mode to one of the continuous conduction mode and the discontinuous conduction mode (S600) to switch the power output stage 1 from the forced continuous conduction mode Force-CCM to the discontinuous conduction mode DCM, thus restoring the normal operation of the conversion circuit 100. It is worth mentioning that, in one embodiment of the present invention, the detailed process steps of the autonomous instantaneous recovery method of the present invention can be referred to in conjunction with the following: Figures 3A-4 The details will not be elaborated here.

[0098] 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 conversion circuit that receives an input voltage at an input node and converts the input voltage to provide an output voltage at an output node, characterized in that, include: A power output stage is coupled between the input node and the output node, and the power output stage includes a power inductor, a first switch, and a second switch, wherein the power inductor, the first switch, and the second switch are all connected to the midpoint of the power output stage; and A controller is coupled to the first switch and the second switch, and controls the first switch and the second switch to be turned on and off alternately, so as to control the power inductor to generate an inductor current. The controller operates the power output stage in one of a continuous conduction mode, a discontinuous conduction mode, and a forced continuous conduction mode, and sets a negative lower limit value for the inductor current. Specifically, when the controller determines that the power output stage is operating in the continuous conduction mode and the output voltage is higher than a voltage upper limit, the controller operates the power output stage in the forced continuous conduction mode, and in the forced continuous conduction mode... (a) When the inductor current has not yet dropped to the negative lower limit, the controller controls the second switch to remain on. (b) When the inductor current drops to the negative lower limit, the controller repeats the following steps: (1) controlling the first switch to turn on and the second switch to turn off for a specific duration; (2) controlling the first switch to turn off and the second switch to turn on until the inductor current drops to the negative lower limit, thereby maintaining the inductor current within a predetermined range associated with the negative lower limit; and Specifically, when the controller determines that the output voltage is lower than a lower voltage limit, the controller switches the power output stage from the forced continuous conduction mode to one of the continuous conduction mode and the discontinuous conduction mode.

2. The conversion circuit as described in claim 1, characterized in that, The controller includes: A main control circuit generates a pulse-width modulation (PWM) signal based on the output voltage to control the first switch and the second switch to be alternately turned on and off via the PWM signal. The main control circuit also generates a high-impedance signal based on the inductor current. An instantaneous control loop determines whether the power output stage is operating in the discontinuous conduction mode based on the high impedance signal, and determines whether the output voltage is higher than the upper voltage limit, so as to provide a forced conduction signal to adjust the pulse width modulation signal accordingly.

3. The conversion circuit as described in claim 2, characterized in that, The main control circuit generates an energy demand signal based on the output voltage and generates a pulse width modulation signal based on the energy demand signal; the instantaneous control circuit provides the forced conduction signal based on the high impedance signal and the energy demand signal.

4. The conversion circuit as described in claim 2, characterized in that, The instantaneous control loop includes: An energy detection circuit sets an upper limit value for the voltage and generates an energy excess signal based on the output voltage and the upper limit value for the voltage. A mode detection circuit determines the operating mode of the power output stage based on the pulse width modulation signal and provides a mode indication signal associated with the change in operating mode; and A logic circuit generates a forced conduction signal based on the excess energy signal and the mode indication signal, thereby causing the power output stage to operate in the forced continuous conduction mode.

5. The conversion circuit as described in claim 4, characterized in that, The main control loop includes: A feedback circuit includes a voltage divider circuit and an error amplifier. The voltage divider circuit generates a feedback voltage based on the output voltage, and the error amplifier generates an error signal based on the feedback voltage and a reference voltage. The energy detection circuit further includes: A potential clamping circuit clamps the error signal to a lower limit value based on the error signal being below that lower limit value, thereby maintaining the operation of the error amplifier.

6. The conversion circuit as described in claim 1, characterized in that, In the forced continuous conduction mode, when the inductor current drops to the negative lower limit and the output voltage is still higher than the upper voltage limit, the controller controls the first switch and the second switch to alternately turn on and off to maintain the inductor current within the predetermined range, and the lower limit of the predetermined range is the negative lower limit.

7. The conversion circuit as described in claim 1, characterized in that, When the inductor current is within the predetermined range, and the controller controls the inductor current to leave the predetermined range by alternating the conduction and cutoff of the first switch and the second switch, and gradually increases the inductor current to zero by alternating the conduction and cutoff of the first switch and the second switch based on a specific cycle.

8. A method for autonomous instantaneous recovery of a conversion circuit, the conversion circuit including a power output stage, the power output stage including a power inductor, a first switch and a second switch, characterized in that, The autonomous transient recovery method includes the following steps: The first switch and the second switch are alternately turned on and off to control the power inductor to generate an inductor current; It is determined that the power output stage operates in a continuous conduction mode, and an output voltage of the conversion circuit is higher than a voltage upper limit value; The power output stage is operated in a forced continuous conduction mode, and in this forced continuous conduction mode, (a) When the inductor current has not yet dropped to a negative lower limit, control the second switch to remain on; and (b) Once the inductor current drops to the negative lower limit, the process is repeated. (1) Control the first switch to be turned on and the second switch to be turned off for a specific duration; and (2) Control the first switch to turn off and the second switch to turn on until the inductor current drops to the negative lower limit value, so that the inductor current is maintained in a predetermined range associated with the negative lower limit value; The output voltage is determined to be below a lower voltage limit. and Switch the power output stage from the forced continuous conduction mode to one of a continuous conduction mode and a discontinuous conduction mode.

9. The autonomous transient recovery method as described in claim 8, characterized in that, It also includes the following steps: A pulse width modulation signal is generated based on the output voltage, and the first switch and the second switch are alternately turned on and off by the pulse width modulation signal, and a high impedance signal is generated based on the inductor current. Based on the high impedance signal, it is determined whether the power output stage is operating in the discontinuous conduction mode, and it is determined whether the output voltage is higher than the upper voltage limit and a forced conduction signal is provided accordingly; and The pulse width modulation signal is adjusted by the forced conduction signal.

10. The autonomous instantaneous recovery method as described in claim 9, characterized in that, It also includes the following steps: An energy demand signal is generated based on the output voltage, and the pulse width modulation signal is generated based on the energy demand signal; and The forced conduction signal is provided based on the high impedance signal and the energy demand signal.

11. The autonomous instantaneous recovery method as described in claim 9, characterized in that, It also includes the following steps: Set the upper limit of the voltage, and generate an energy excess signal based on the output voltage and the upper limit of the voltage; The operating mode of the power output stage is determined based on the pulse width modulation signal, and a mode indication signal associated with the change in operating mode is provided; and The power output stage is operated in the forced continuous conduction mode by generating the forced conduction signal based on the excess energy signal and the mode indication signal.

12. The autonomous instantaneous recovery method as described in claim 11, characterized in that, It also includes the following steps: A feedback voltage is generated based on the output voltage, and an error signal is generated based on the feedback voltage and a reference voltage; and The error signal is clamped to the lower limit value because the error signal is below the lower limit value, so as to maintain the operation of the feedback circuit.

13. The autonomous transient recovery method as described in claim 8, characterized in that, It also includes the following steps: In the forced continuous conduction mode, when the inductor current drops to the negative lower limit and the output voltage is still higher than the upper limit, the first switch and the second switch are controlled to alternately turn on and off to maintain the inductor current within the predetermined range. The lower limit of the predetermined interval is the negative lower limit value.

14. The autonomous transient recovery method as described in claim 8, characterized in that, It also includes the following steps: When the inductor current is within the predetermined range and the output voltage becomes lower than the lower voltage limit, the inductor current is controlled to move out of the predetermined range by alternately turning the first switch and the second switch on and off; and The inductor current is gradually increased to zero by controlling the first switch and the second switch to be turned on and off alternately according to a specific cycle.

Images