Digital control method and control circuit of single-inductor multi-output converter

Abstract

The application provides a digital control method and a control circuit of a single-inductor multi-output converter, wherein the digital control method comprises the following steps: receiving a clock signal, and controlling the single-inductor multi-output converter to enter a split-mode; controlling the single-inductor multi-output converter to enter a charging mode or a discharging mode according to a digital quantity of an inductor current and a reference current; and controlling whether the single-inductor multi-output converter enters a holding mode according to a generation time of a next clock signal. The digital control method controls output voltages of each output branch in an initial stage of a clock period in a digital manner, and controls the inductor current in a middle and later stage of the clock period, so that the output voltages of each output branch and the inductor current are stable, and cross interference of each output branch is reduced.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically, to a digital control method and control circuit for a single-inductor multi-output converter. Background Technology

[0002] A Single-Inductor Multiple-Output (SIMO) converter is a DC-DC converter that requires only one input voltage to simultaneously obtain multiple DC output voltages. SIMO uses a single inductor to power or filter different output channels, thus reducing system size and cost. The power transfer methods of SIMO converters are mainly divided into two types: Time-Division Multiplexing (TM) and Ordered Output-Distributive Control (OPDC).

[0003] In time-division multiplexing, each output channel requires charging and then discharging the inductor. For a converter with n channels, time-division multiplexing involves n charging and n discharging cycles. This control method results in too many switching actions and significant switching losses. Furthermore, when the load changes, this control method may cause the charging and discharging cycles of adjacent channels to overlap, leading to increased mutual interference between channels.

[0004] In sequential power supply control, the inductor is charged only once per cycle, and then each output is discharged sequentially. For a converter with n channels, sequential power supply control requires only one charge and n discharge cycles. This control method can significantly reduce the number of switching operations and switching losses, and is widely used in single-inductor multi-output DC-DC converters. However, in sequential power supply control, all channels share the same inductor. Therefore, changes in the load of one channel will cause changes in the inductor current, and the changing inductor current will inevitably cause interference to other channels that do not experience load transients (i.e., the load remains constant).

[0005] Therefore, the control methods of existing single-inductor multi-output converters all suffer from the problem of mutual interference between channels. Summary of the Invention

[0006] To address the technical problem of mutual interference between output channels in existing control methods for single-inductor multi-output converters, this invention proposes a digital control method and control circuit for a single-inductor multi-output converter. The single-inductor multi-output converter connects multiple output branches, each of which includes a control switch and a voltage loop module. The digital control method includes:

[0007] Receive a clock signal to control the single-inductor multi-output converter to enter the shunt mode. In the shunt mode, the input power supply is controlled to supply power to each output branch in sequence according to the digital quantity of the inductor current and the output quantity of each voltage loop module. Receive a clock signal to indicate that the single-inductor multi-output converter has entered a clock cycle.

[0008] Based on the digital value of the inductor current and the reference current, the single-inductor multi-output converter is controlled to enter either the charging mode or the discharging mode. In the charging mode, the inductor charges, and in the discharging mode, the inductor discharges to any of the output branches.

[0009] Based on the generation time of the next clock signal, control whether the single-inductor multi-output converter enters the hold mode, in which the energy in the inductor remains unchanged.

[0010] Furthermore, it also includes the step of: adjusting the magnitude of the reference current in the next clock cycle based on the relationship between the preset period and the actual period, wherein,

[0011] The actual period represents the duration of the shunt mode and the charging mode within the current clock cycle, or the actual period represents the duration of the shunt mode and the discharging mode within the current clock cycle.

[0012] Furthermore, controlling the input power supply to sequentially power each output branch based on the digital value of the inductor current and the output values ​​of each voltage loop module includes the following steps:

[0013] Collect the inductor current and the output voltage of any of the output branches, and perform analog-to-digital conversion to obtain the digital values ​​of the inductor current and the output voltage;

[0014] The PI parameters are obtained based on the digital value of the output voltage and the reference voltage.

[0015] The voltage loop module of this output branch generates the output quantity by performing PI control based on the PI parameters;

[0016] Based on the relationship between the digital value of the inductor current and the output value of the voltage loop module, the input power supply is controlled to supply power to this output branch.

[0017] Furthermore, controlling the single-inductor multi-output converter to enter charging or discharging mode based on the digital value of the inductor current and the reference current includes the following steps:

[0018] After the current shunt mode ends, the inductor current is collected and converted from digital to analog to obtain the digital value of the inductor current.

[0019] If the digital value of the inductor current is greater than the reference current, the single-inductor multi-output converter is controlled to enter the discharge mode.

[0020] If the digital value of the inductor current is less than the reference current, the single-inductor multi-output converter is controlled to enter the charging mode.

[0021] Furthermore, controlling whether the single-inductor multi-output converter enters hold mode based on the generation time of the next clock signal includes the following steps:

[0022] Determine whether the next clock signal is received when the discharge mode or the charging mode ends;

[0023] If so, the single-inductor multi-output converter is controlled to directly enter the next clock cycle;

[0024] If not, the single-inductor multi-output converter is controlled to enter hold mode until the next clock signal is received.

[0025] Furthermore, based on the relationship between the preset period and the actual period, the reference current in the next clock cycle is adjusted as follows:

[0026] When the actual period is greater than the preset period, the reference current in the next clock cycle is increased;

[0027] When the actual period is less than the preset period, the reference current in the next clock cycle is reduced.

[0028] Furthermore, the change in the reference current is the absolute value of the difference between the actual period and the preset period.

[0029] Furthermore, the voltage loop module of this output branch generates the output quantity through PI control based on PI parameters, including the following steps:

[0030] Obtain the pre-amplifier output and the pre-amplifier error. The pre-amplifier output represents the output of the voltage loop module before the voltage loop module performs PI control according to the PI parameters. The pre-amplifier error represents the difference between the output voltage and the input voltage of the output branch before the voltage loop module performs PI control according to the PI parameters.

[0031] Based on the pre-output quantity, the pre-error quantity, the output threshold, and the error threshold, the control voltage loop module determines whether the integral stage of the PI control process is set to zero and whether the error accumulation stage is counted to zero.

[0032] A control circuit for a single-inductor multi-output converter is disclosed. The single-inductor multi-output converter connects to multiple output branches, each output branch including a control switch and a voltage loop module. The single-inductor multi-output converter includes: a first switch and a second switch connected between an input power supply and a reference ground; a third switch connected between a second terminal of an inductor and a reference ground; a first terminal of the inductor connected to a node between the first and second switches; and a second terminal of the inductor connected to multiple output branches. The digital control circuit controls the single-inductor multi-output converter using the digital control method described above.

[0033] Furthermore, the digital control circuit includes:

[0034] Current sampling circuit to collect inductor current;

[0035] The voltage sampling circuit collects the output voltage of each output branch.

[0036] The analog-to-digital converter circuit performs analog-to-digital conversion on the inductor current to obtain the digital value of the inductor current, and performs analog-to-digital conversion on the output voltage to obtain the digital value of the output voltage.

[0037] The FPGA control circuit generates indication signals for controlling the single-inductor multi-output circuit to enter the shunt mode, charging mode, discharging mode, and holding mode according to the digital control method.

[0038] An isolated drive circuit generates drive signals to control the on / off states of the first switch, the second switch, the third switch, and multiple control switches based on the indication signal.

[0039] In summary, the digital control method proposed in this invention controls the output voltage of each output branch in the early stage of the clock cycle and controls the inductor current in the middle and late stages of the clock cycle in a digital manner, thereby ensuring the stability of the output of each output branch and the stability of the inductor current, and reducing the cross-interference of each output branch. Attached Figure Description

[0040] Figure 1 A flowchart of the digital control method proposed in this invention;

[0041] Figure 2 This is a topology for a single-inductor multi-output converter.

[0042] Figure 3 Four modes of operation for a single-inductor multi-output converter;

[0043] Figure 4 The flowchart is for the integral separation method;

[0044] Figure 5 This shows the change in inductor current under buck-dominant mode.

[0045] Figure 6 This shows the change in inductor current under boost-dominant mode.

[0046] Figure 7 This is a block diagram of the control circuit.

[0047] Figure 8 This is a framework diagram of the voltage loop module. Detailed Implementation

[0048] Some preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0049] Since the existing control methods for single-inductor multi-output converters cannot solve the problem of cross-interference between output channels, this invention proposes a digital control method for single-inductor multi-output converters to reduce cross-interference between output channels.

[0050] Specifically, the digital control method proposed in this invention includes the following steps:

[0051] After receiving the clock signal, the single-inductor multi-output converter is controlled to enter the shunt mode. In the shunt mode, the input power supply is controlled to supply power to each output branch in sequence according to the digital value of the inductor current and the output value of the voltage loop module in each output branch. Receiving the clock signal indicates that the single-inductor multi-output converter has entered one clock cycle.

[0052] After the shunt mode ends, based on the digital value of the inductor current and the reference current, the single-inductor multi-output converter is controlled to enter the charging mode or the discharging mode. In the charging mode, the inductor is controlled to charge, and in the discharging mode, the inductor is controlled to discharge to any output branch.

[0053] After the discharge or charge mode ends, the single-inductor multi-output converter is controlled to enter the holding mode according to the generation time of the next clock signal. In the holding mode, the energy in the control inductor remains unchanged.

[0054] Therefore, the digital control method proposed in this invention controls the output voltage of each output branch in the early stage of the clock cycle and controls the inductor current in the middle and late stages of the clock cycle in a digital manner, thereby ensuring the stability of the output of each output branch and the stability of the inductor current, and reducing the cross-interference of each output branch.

[0055] Furthermore, during the operation of the single-inductor multi-output converter, it requires dynamic adjustment over multiple clock cycles to reach a stable state. Therefore, to facilitate the smooth entry of the single-inductor multi-output converter into a stable state, the digital control method proposed in this invention also includes adjustment of the reference current. Specifically:

[0056] Based on the relationship between the preset period and the actual period, the magnitude of the reference current in the next clock cycle is adjusted. The actual period refers to the duration of the shunt mode and the charging mode in the current clock cycle, or the duration of the shunt mode and the discharging mode in the current clock cycle.

[0057] Specifically, the digital control method proposed in this invention will be further explained and described below.

[0058] In a single-inductor multi-output converter, the inductor connects to multiple output branches. Each output branch includes a control switch and a voltage loop module. The control switch controls the on / off state of the output branch, and the voltage loop module regulates the output voltage of the output branch. For example... Figure 8 As shown, the voltage loop module includes a feedback unit, an analog-to-digital converter (ADC), and a PI controller. The feedback unit acquires the output voltage of the output branch. The ADC converts the acquired output voltage into a digital value. The PI controller receives the error between the digital values ​​of the reference voltage and the output voltage, and generates an output based on this error. The single-inductor multi-output converter adjusts the output voltage of the output branch according to the output of the PI controller. Based on this single-inductor multi-output converter, this invention proposes a digital control method to reduce cross-interference among multiple output branches, such as... Figure 1 As shown:

[0059] When the single-inductor multi-output converter receives the clock signal, it enters a new clock cycle. After entering the clock cycle, the converter enters shunt mode, where it controls the input power supply to sequentially power each output branch. Specifically, the converter controls the input power supply to power the corresponding output branch based on the digital value of the inductor current and the output of any voltage loop module. After powering that output branch, the converter re-acquires the digital value of the inductor current and the output of any remaining voltage loop module, then controls the input power supply to power the corresponding output branch again. This process is repeated until the input power supply has powered all output branches. The input power supply powers one output branch at a time, and the order in which the output branches are powered is arbitrarily chosen.

[0060] After the shunt mode ends, the single-inductor multi-output converter (SIMP) controls itself to enter either charging or discharging mode based on the digital value of the inductor current and the reference current. In charging mode, the inductor is charged; in discharging mode, the inductor discharges to any output branch. Specifically, after the input power supply has supplied power to all output branches, the digital value of the inductor current is acquired and compared with the reference current. If the digital value of the inductor current is greater than the reference current, the SIMP enters discharging mode until the digital value of the inductor current equals the reference current; if the digital value of the inductor current is less than the reference current, the SIMP enters charging mode until the inductor current equals the reference current.

[0061] After the charging or discharging mode ends, based on the timing of the next clock signal, the single-inductor multi-output converter is controlled to enter a hold mode before the next clock cycle. In hold mode, the inductor neither charges nor discharges, and the energy in the inductor remains constant. Specifically, if the next clock signal has not arrived at the end of the charging or discharging mode, it means the current clock cycle has not ended. In this case, the single-inductor multi-output converter needs to be controlled to enter hold mode and maintain hold mode until the next clock signal arrives, thereby achieving constant frequency control of the clock cycle. When the next clock signal arrives, the single-inductor multi-output converter enters the next clock cycle and re-enters the above process. If the next clock signal arrives at the end of the charging or discharging mode, it means the current clock cycle has ended. In this case, the single-inductor multi-output converter simply needs to be controlled to directly enter the next clock cycle and re-enter the above process.

[0062] Furthermore, to ensure that the single-inductor multi-output converter can smoothly enter a stable output state through dynamic adjustment during startup, the reference current in the next clock cycle is adjusted according to the relationship between the actual cycle and the preset cycle. The actual cycle refers to the duration of the shunt and charging modes, or the duration of the shunt and discharging modes, within the current clock cycle. Specifically, when the actual cycle is greater than the preset cycle, the reference current in the next clock cycle is increased by the absolute value of the difference between the actual and preset cycles; when the actual cycle is less than the preset cycle, the reference current in the next clock cycle is decreased by the absolute value of the difference between the actual and preset cycles.

[0063] The digital control method proposed in this invention will be applied to a specific topology of a single-inductor multi-output converter to further illustrate the digital control method proposed in this invention.

[0064] like Figure 2As shown, the single-inductor multi-output converter includes a first switch SW1 and a second switch SW2 connected between the input power supply and a reference ground, and a third switch SW3 connected between the second terminal of inductor L0 and the reference ground. The first terminal of inductor L0 is connected to node Vx1 between the first switch SW1 and the second switch SW2. The second terminal of inductor L0 is connected to a first output branch 101, a second output branch 102, and a third output branch 103. The first output branch 101 includes a first control switch K1 and a first voltage loop module. The first control switch K1 controls the on / off state of the first output branch 101, and the first voltage loop module controls the output voltage of the first output branch 101. The second output branch 102 includes a second control switch K2 and a second voltage loop module. The second control switch K2 controls the on / off state of the second output branch 102, and the second voltage loop module controls the output voltage of the second output branch 102. The third output branch 103 includes a third control switch K3 and a third voltage loop module. The third control switch K3 controls the on / off state of the third output branch 103, and the third voltage loop module controls the output voltage of the third output branch 103. Each output branch can be arbitrarily selected to implement either Buck or Boost functionality. Assume that the first output branch 101 is selected as Boost mode, the second output branch 102 as Boost mode, and the third output branch 103 as Buck mode.

[0065] Among them, such as Figure 3 As shown, the single-inductor multi-output converter can operate in the following modes:

[0066] (1) Flow splitting mode SW B SW split mode B The input power supply sequentially supplies power to the three output branches. When the input power supply supplies power to the first output branch 101, the first switch SW1 and the first control switch K1 are closed. When the input power supply supplies power to the second output branch 102, the first switch SW1 and the second control switch K2 are closed. When the input power supply supplies power to the third output branch 103, the first switch SW1 and the third control switch K3 are closed.

[0067] (2) Charging mode SW C Charging mode SW C The lower control inductor L0 is charged, which controls the first switch SW1 and the third switch SW3 to close.

[0068] (3) Discharge mode SW D Discharge mode SW DWhen the control inductor L0 discharges to any output branch, when the control inductor L0 discharges to the first output branch 101, the second switch SW2 and the first control switch K1 are closed; when the control inductor L0 discharges to the second output branch 102, the second switch SW2 and the second control switch K2 are closed; when the control inductor L0 discharges to the third output branch 103, the second switch SW2 and the third control switch K3 are closed.

[0069] (4) Maintain mode SW H Maintain mode SW H The lower control inductor L0 neither discharges nor charges, meaning the energy in the control inductor L0 remains constant. At this time, the second control switch SW2 and the third control switch SW3 are closed.

[0070] When the clock signal CLK arrives, the single-inductor multi-output converter enters the current clock cycle, controlling the single-inductor multi-output converter to enter the shunt mode SW. B Specifically, the inductor current is collected and converted from analog to digital to obtain a digital value; the output voltage of the first output branch 101 is collected and converted from analog to digital to obtain a digital value; a PI parameter is obtained based on the difference between the digital value of the output voltage and the reference voltage; the first voltage loop module generates an output value after performing PI control based on the PI parameter; if the digital value of the inductor current is less than the output value of the first voltage loop module, the first switch SW1 and the first control switch K1 are closed, thereby controlling the input power supply to power the first output branch 101, until the digital value of the inductor current equals the output value of the first voltage loop module, at which point the input power supply stops powering the first output branch 101. It should be noted that during the process of the input power supply to the first output branch 101, the digital value of the inductor current changes and is acquired in real time. Similarly, after the input power supply finishes supplying power to the first output branch 101, the above steps are repeated to control the input power supply to the second output branch 102; after the input power supply finishes supplying power to the second output branch 102, the above steps are repeated to control the input power supply to the third output branch 103, thereby realizing that the input power supply supplies power to each output branch in sequence. In other embodiments, the order in which the input power supply supplies power to each output branch can be arbitrarily selected, and it can be in the order of supplying power to the second output branch 102, the first output branch 101, and the third output branch 103 in sequence.

[0071] shunt mode SW BAfter completion, the single-inductor multi-output converter is controlled to enter either charging or discharging mode based on the digital value of the inductor current and the reference current. Specifically, the inductor current is acquired and converted from digital to analog to obtain the digital value of the inductor current; the acquired digital value of the inductor current is compared with the reference current; if the digital value of the inductor current is greater than the reference current, it indicates that the single-inductor multi-output converter is in boost-dominated mode, and at this time, the single-inductor multi-output converter is controlled to enter the discharging mode SW. D This means controlling the closing of the second switch SW2 and any one of the first control switch K1, the second control switch K2, and the third control switch K3, thereby enabling the inductor L0 to discharge to any output branch, and stopping the inductor from discharging when the digital value of the inductor current decreases to equal the reference current; if the digital value of the inductor current is less than the reference current, it indicates that the single-inductor multi-output converter is in buck-dominated mode, and at this time, the single-inductor multi-output converter is controlled to enter the charging mode SW. C That is, controlling the first switch SW1 and the second switch SW2 to close, so as to charge the inductor L0, and the inductor stops charging when the digital value of the inductor current increases to equal the reference current.

[0072] When the inductor charging or discharging ends, it checks whether a new clock signal CLK has been generated. If the new clock signal CLK is generated when the inductor L0 finishes charging or discharging, the single-inductor multi-output converter is controlled to directly end the current clock cycle and enter the next clock cycle, repeating the above steps when entering the next clock cycle. If the new clock signal CLK is not generated when the inductor L0 finishes charging or discharging, the single-inductor multi-output converter is controlled to enter the hold mode SW. H That is, the second switch SW2 and the third switch SW3 are closed. At this time, the two ends of the inductor L0 are pulled low to the reference ground. The inductor L0 is neither charged nor discharged. The energy stored in the inductor L0 remains unchanged. This process continues until the new clock signal CLK is generated, thereby realizing constant frequency control of the clock cycle. That is, by adding a process to keep the energy of the inductor L0 constant, the frequency of each clock cycle is the same.

[0073] Specifically, such as Figure 5 As shown, upon receiving the clock signal CLK, the single-inductor multi-output converter is controlled to enter the shunt mode SW. B In the split-mode SW BFirst, the input power supply is controlled to power the first output branch 101. Since the first output branch 101 is in Boost mode, the current iL0 of inductor LO decreases. Then, the input power supply is controlled to power the second output branch 102. Since the second output branch 102 is in Boost mode, the current iL0 of inductor LO decreases. Finally, the input power supply is controlled to power the third output branch 103. Since the third output branch 103 is in Buck dominant mode, the current iL0 of inductor LO increases. After the shunt mode ends, because iL0 is less than the reference current Iref, i.e., the single-inductor multi-output converter is in Buck dominant mode, the single-inductor multi-output converter is controlled to enter the charging mode SW. C At this point, iL0 increases until it equals the reference current Iref, at which point the charging mode SW... C End. Charging mode SW C At the end, the next clock signal CLK has not yet been generated, so the single-inductor multi-output converter is controlled to enter hold mode SW. H The current clock cycle ends and the next clock cycle begins when the next clock signal CLK arrives.

[0074] Specifically, such as Figure 6 As shown, upon receiving the clock signal CLK, the single-inductor multi-output converter is controlled to enter the shunt mode SW. B In the split-mode SW B First, the input power supply is controlled to power the first output branch 101. Since the first output branch 101 is in Boost mode, the current iL0 of inductor LO decreases. Then, the input power supply is controlled to power the second output branch 102. Since the second output branch 102 is in Boost mode, the current iL0 of inductor LO decreases. Finally, the input power supply is controlled to power the third output branch 103. Since the third output branch 103 is in Buck dominant mode, the current iL0 of inductor LO increases. After the shunt mode ends, because iL0 is greater than the reference current Iref, i.e., the single-inductor multi-output converter is in boost dominant mode, the single-inductor multi-output converter is controlled to enter the discharge mode SW. D At this point, iL0 decreases until it equals the reference current Iref, at which point the discharge mode SW begins. D End. Discharge mode SW D At the end, the next clock signal CLK has not yet been generated, so the single-inductor multi-output converter is controlled to enter hold mode SW. H The current clock cycle ends and the next clock cycle begins when the next clock signal CLK arrives.

[0075] Furthermore, to facilitate the smooth transition of the single-inductor multi-output converter to a stable state through dynamic adjustment, the reference current needs to be adjusted for each clock cycle. Specifically, within the current clock cycle, the reference current for the next clock cycle is adjusted based on the relationship between the actual cycle and the preset cycle. If the actual cycle is greater than the preset cycle, the reference current for the next clock cycle is increased by the difference between the actual and preset cycles; if the actual cycle is less than the preset cycle, the reference current for the next clock cycle is decreased by the difference between the preset and actual cycles. Here, the actual cycle refers to the time from the beginning of the current clock cycle to the end of inductor charging or discharging, while the preset cycle is a set value that is shorter than the clock cycle.

[0076] It should be noted that the reference current mentioned above is a digital quantity when comparing the digital quantity of the inductor current with the reference current, and the reference voltage in the PI parameter obtained by the difference between the digital quantity of the output voltage and the reference voltage is also a digital quantity. The collected inductor current reflects the magnitude of the current accumulated in the inductor from the beginning of the clock cycle.

[0077] Furthermore, in the process of the voltage loop module generating output through PI control based on PI parameters, in order to suppress output saturation of the voltage loop module, this invention proposes an integral separation method, which specifically includes:

[0078] Obtain the pre-output quantity and the pre-error quantity. The pre-output quantity refers to the output quantity of the voltage loop module before it performs PI control according to the PI parameters. The pre-error quantity refers to the difference between the output voltage and the input voltage of the output branch before the voltage loop module performs PI control according to the PI parameters.

[0079] The PI control process is controlled based on the pre-output quantity, pre-error quantity, output threshold, and error threshold to determine whether the integral stage is set to zero and whether the error accumulation stage is counted to zero.

[0080] If the pre-output quantity is greater than the first output threshold and the pre-error quantity is greater than zero, then the control error accumulation circuit is counted as zero.

[0081] If the pre-output quantity is greater than the first output threshold and the pre-error quantity is less than the first error threshold, then the integral control loop is set to zero and the first error threshold is less than zero.

[0082] If the pre-output quantity is greater than the first output threshold, the pre-error quantity is greater than or equal to the first error threshold and the pre-error quantity is less than zero, then the control integral and error accumulation stages will calculate normally.

[0083] If the pre-output quantity is less than the second output threshold and the pre-error quantity is less than zero, then the control error accumulation circuit is counted as zero, and the second output threshold is less than the first output threshold.

[0084] If the pre-output quantity is less than the second output threshold and the pre-error quantity is greater than the second error threshold, then the integral control loop is set to zero and the second error threshold is greater than zero.

[0085] If the pre-output quantity is less than the second output threshold, the pre-error quantity is greater than or equal to zero and the pre-error quantity is less than or equal to the second error threshold, then the control integral and error accumulation stages will calculate normally.

[0086] If the pre-output quantity is less than or equal to the first output threshold and the pre-output quantity is greater than or equal to the second output threshold, and the pre-error quantity is greater than the first error threshold and the pre-error quantity is less than the second error threshold, then the control integral and error accumulation stages will calculate normally.

[0087] If the preamplifier output is less than or equal to the first output threshold and greater than or equal to the second output threshold, and the preamplifier error is greater than or equal to the second error threshold, or if the preamplifier output is less than or equal to the first output threshold and greater than or equal to the second output threshold, and the preamplifier error is less than or equal to the first error threshold, then the control integral stage is set to zero.

[0088] More specifically, such as Figure 4 As shown, the integral separation method includes:

[0089] Determine if the output value of the preamplifier is greater than the first output threshold PI_MAX;

[0090] If the preamplifier output is greater than the first output threshold PI_MAX, then determine if the preamplifier error is greater than zero; if the preamplifier error is greater than zero, then control the error accumulation stage to count to zero; if the preamplifier error is less than or equal to zero, then determine if the preamplifier error is less than the first error threshold err_min; if the preamplifier error is less than the first error threshold err_min, then control the integration stage to set to zero; if the preamplifier error is greater than or equal to the first error threshold err_min, then control the error accumulation stage and the integration stage to calculate normally.

[0091] If the output value of the preamp is less than or equal to the first output threshold PI_MAX, then determine whether the output value of the preamp is less than the first output threshold PI_MAX.

[0092] If the preamplifier output is less than the first output threshold PI_MAX, then determine if the preamplifier error is less than zero; if the preamplifier error is less than zero, then control the error accumulation stage to count to zero; if the preamplifier error is greater than or equal to zero, then determine if the preamplifier error is greater than the second error threshold err_max; if the preamplifier error is greater than the second error threshold err_max, then control the integration stage to set to zero; if the preamplifier error is less than or equal to the second error threshold err_max, then control the error accumulation stage and the integration stage to calculate normally.

[0093] If the pre-output quantity is greater than or equal to the first output threshold PI_MAX, then determine whether the pre-error quantity is greater than the first error threshold err_min and less than the second error threshold err_max; if yes, then control the error accumulation stage and the integration stage to calculate normally; if no, then control the integration stage to be set to zero.

[0094] In summary, the digital control method proposed in this invention performs digital control on the output voltage and inductor current of each output branch, so that the output voltage of each output branch is stable and meets the requirements, and the inductor current reaches the current reference at the end of the clock cycle, thereby reducing the cross-interference of each output branch.

[0095] This invention also proposes a control circuit for a single-inductor multi-output converter. The single-inductor multi-output converter connects multiple output branches, each output branch including a control switch and a voltage loop module. The single-inductor multi-output converter includes: a first switch and a second switch connected between the input power supply and a reference ground, a third switch connected between the second end of the inductor and the reference ground, the first end of the inductor being connected to the node between the first switch and the second switch, and the second end of the inductor being connected to multiple output branches. The control circuit uses the digital control method proposed above to control the single-inductor multi-output converter.

[0096] Specifically, such as Figure 7 As shown, the control circuit includes:

[0097] Current sampling circuit to collect inductor current;

[0098] The voltage sampling circuit collects the output voltage of each output branch.

[0099] The analog-to-digital converter circuit performs analog-to-digital conversion on the inductor current to obtain the digital value of the inductor current, and performs analog-to-digital conversion on the output voltage to obtain the digital value of the output voltage.

[0100] The FPGA control circuit generates indication signals to control the single-inductor multi-output converter to enter the shunt mode, charging mode, discharging mode and holding mode according to the digital control method described above;

[0101] An isolated drive circuit generates drive signals to control the on / off states of the first, second, and third switching transistors and multiple control switches based on an indication signal.

[0102] Therefore, the control circuit of the single-inductor multi-output converter proposed in this invention does not require additional analog auxiliary circuits and adopts a digital control method, which is simple and flexible. Using an FPGA control circuit as the core, a higher switching frequency is achieved, thereby reducing the inductor size and consequently reducing the overall size of the single-inductor multi-output converter.

[0103] The preferred embodiments of the present invention have been described in detail above. However, the circuitry and beneficial effects of this patent should not be considered as being limited to those described above. The disclosed embodiments and accompanying drawings can better illustrate the present invention. Therefore, the disclosed embodiments and accompanying drawings are for the purpose of better understanding the present invention. The protection of the present invention is not limited to the scope of this disclosure. All substitutions and modifications made by those skilled in the art to the embodiments of the present invention are within the protection scope of the present invention.

Claims

1. A digital control method for a single-inductor multi-output converter, wherein the single-inductor multi-output converter is connected to multiple output branches, each output branch including a control switch and a voltage loop module, characterized in that, The digital control method includes the following steps: Receive a clock signal to control the single-inductor multi-output converter to enter the shunt mode. In the shunt mode, the input power supply is controlled to supply power to each output branch in sequence according to the digital quantity of the inductor current and the output quantity of each voltage loop module. Receive a clock signal to indicate that the single-inductor multi-output converter has entered a clock cycle. Based on the digital value of the inductor current and the reference current, the single-inductor multi-output converter is controlled to enter either the charging mode or the discharging mode. In the charging mode, the inductor charges, and in the discharging mode, the inductor discharges to any of the output branches. Based on the generation time of the next clock signal, control whether the single-inductor multi-output converter enters the hold mode, in which the energy in the inductor remains unchanged.

2. The digital control method as described in claim 1, characterized in that, It also includes the step of: comparing the magnitude of the preset period and the actual period, and adjusting the magnitude of the reference current in the next clock cycle, wherein, The actual period represents the duration of the shunt mode and the charging mode within the current clock cycle, or the actual period represents the duration of the shunt mode and the discharging mode within the current clock cycle.

3. The digital control method as described in claim 1, characterized in that, The steps include controlling the input power supply to sequentially power each output branch based on the digital value of the inductor current and the output of each voltage loop module: Collect the inductor current and the output voltage of any of the output branches, and perform analog-to-digital conversion to obtain the digital values ​​of the inductor current and the output voltage; The PI parameters are obtained based on the digital value of the output voltage and the reference voltage. The voltage loop module of this output branch generates the output quantity by performing PI control based on the PI parameters; Based on the relationship between the digital value of the inductor current and the output value of the voltage loop module, the input power supply is controlled to supply power to this output branch.

4. The digital control method as described in claim 1, characterized in that, Controlling the single-inductor multi-output converter to enter charging or discharging mode based on the digital value of the inductor current and the reference current includes the following steps: After the current shunt mode ends, the inductor current is collected and converted from digital to analog to obtain the digital value of the inductor current. If the digital value of the inductor current is greater than the reference current, the single-inductor multi-output converter is controlled to enter the discharge mode. If the digital value of the inductor current is less than the reference current, the single-inductor multi-output converter is controlled to enter the charging mode.

5. The digital control method as described in claim 1, characterized in that, Controlling whether the single-inductor multi-output converter enters hold mode based on the generation time of the next clock signal includes the following steps: Determine whether the next clock signal is received when the discharge mode or the charging mode ends; If so, control the single-inductor multi-output converter to directly enter the next clock cycle; Otherwise, the single-inductor multi-output converter is controlled to enter hold mode until the next clock signal is received.

6. The digital control method as described in claim 2, characterized in that, Comparing the preset period and the actual period, adjusting the reference current in the next clock cycle includes: When the actual period is greater than the preset period, the reference current in the next clock cycle is increased; When the actual period is less than the preset period, the reference current in the next clock cycle is reduced.

7. The digital control method as described in claim 6, characterized in that, The change in the reference current is the absolute value of the difference between the actual period and the preset period.

8. The digital control method as described in claim 3, characterized in that, The voltage loop module of this output branch generates the output quantity through PI control based on PI parameters, including the following steps: Obtain the pre-amplifier output and the pre-amplifier error. The pre-amplifier output represents the output of the voltage loop module before the voltage loop module performs PI control according to the PI parameters. The pre-amplifier error represents the difference between the output voltage and the input voltage of the output branch before the voltage loop module performs PI control according to the PI parameters. Based on the pre-output quantity, the pre-error quantity, the output threshold, and the error threshold, the control voltage loop module determines whether the integral stage of the PI control process is set to zero and whether the error accumulation stage is counted to zero.

9. A control circuit for a single-inductor multi-output converter, wherein the single-inductor multi-output converter is connected to multiple output branches, each output branch including a control switch and a voltage loop module, and the single-inductor multi-output converter includes: The control circuit comprises a first switch and a second switch connected between the input power supply and a reference ground, a third switch connected between the second end of an inductor and the reference ground, a first end of the inductor connected to a node between the first switch and the second switch, and a second end of the inductor connected to multiple output branches. The control circuit uses the digital control method described in any one of claims 1-8 to control the single-inductor multi-output converter.

10. The control circuit as described in claim 9, characterized in that, The control circuit includes: Current sampling circuit to collect inductor current; The voltage sampling circuit collects the output voltage of each output branch. The analog-to-digital converter circuit performs analog-to-digital conversion on the inductor current to obtain the digital value of the inductor current, and performs analog-to-digital conversion on the output voltage to obtain the digital value of the output voltage. The FPGA control circuit generates indication signals for controlling the single-inductor multi-output circuit to enter the shunt mode, charging mode, discharging mode, and holding mode according to the digital control method. An isolated drive circuit generates drive signals to control the on / off states of the first switch, the second switch, the third switch, and multiple control switches based on the indication signal.

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