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EP-4742523-A1 - SINGLE-INDUCTOR MULTIPLE-OUTPUT DC-DC CONVERTER AND METHOD OF OPERATING

EP4742523A1EP 4742523 A1EP4742523 A1EP 4742523A1EP-4742523-A1

Abstract

A SIMO DC-DC converter having a modified buck topology in which multiple output are served from a single inductor. The serving order of the outputs is reversed when the inductor is discharged, such that the inductor current at the end of the serving of an output can be reset to the same value that it had at the beginning of the serving of the same output in the same cycle.

Inventors

  • SURACI, MICHELE

Assignees

  • Semtech Corporation

Dates

Publication Date
20260513
Application Date
20241107

Claims (16)

  1. A single-inductor multiple-output (SIMO) circuit having a modified buck topology in which multiple outputs (51, 52, 53) are selectively and cyclically connectable to a single inductor (61), characterized in that a serving order of the outputs being reversed when the inductor (61) is discharged, such that the inductor current at the end of the serving of an output can be reset to the same value that it had at the beginning of the serving of the same output in the same cycle.
  2. The circuit of the preceding claim, in which a first inductor terminal (A) is connected to a left-side switching circuit (107) operable to inject a current into the inductor from a power supply terminal (41) or from a ground terminal (40), a right-side switching circuit (103) operable to connect a second terminal (B) of the inductor to one of a plurality of output terminals (51, 52, 53), and a control circuit (104, 105) configured to operate cyclically the left-side switching circuit (107) and the right-side switching circuit (103) such that potentials of the output terminals are stabilised to predetermined voltage values, a cycle of operation of the control circuit (104, 105) including a charging part, in which the left-side switching circuit (107) is operated such that the current flowing in the inductor rises and a discharging part, in which the left-side switching circuit is operated such the current flowing in the inductor decreases, characterized in that the control circuit (104, 105) is configured to select with the right-side switching circuit (103) is operated one of the output terminals at a time following a serving order during the charging part and following a reverse order during the discharging part, and to time the left-side switching circuit (107) and the right-side switching circuit (103) such that at the end of each serving interval of a terminal during the discharging part the current flowing in the inductor returns to the value it had at the beginning of a serving interval for the same output terminal during the charging part.
  3. The circuit of the preceding claim, the left-side switching circuit (107) comprising a half-bridge with a high-side switch (117) and a low-side switch (118) operable to allow a current flow between the first terminal (A) of the inductor and the power supply (61), respectively between the first terminal (A) and ground (40).
  4. The circuit of any one of the preceding claims, the right-side switching circuit comprising a plurality of output switches (111,112,113) each operable to connect the second terminal (B) of the inductor to one of the terminals (51, 52, 53).
  5. The circuit of any one of the preceding claims, the output terminals being in number of two, three or more.
  6. The circuit of any one of the preceding claims, the cycle of the control circuit having a fixed frequency.
  7. The circuit of any one of the preceding claims, comprising a zero-current detector, (130) the control circuit (106) being configured to activate a freewheeling mode when the zero-current detector signals that the inductor current reaches zero, in which freewheeling mode the right-side and the left-side are set in an high impedance mode and a bypass switch is closed short-circuiting the inductor.
  8. The circuit of any one of the preceding claims, comprising for each voltage output a feedback loop including a modulator providing a timing signal for the left-hand switching circuit and/or for the right-hand switching circuit driven by an error signal derived from the comparison of the output voltage with a reference value.
  9. The circuit of the preceding claim, the feedback loop including a PI compensator or a PID compensator.
  10. A method of operating a single-inductor multiple-output (SIMO) DC-DC converter comprising a cycle of operation including a charging part, in which the a first terminal (A) of the inductor is connected to potential higher than the output potentials such that the current flowing in the inductor rises and a discharging part, in which the first terminal is connected to a lower potential such the current flowing in the inductor decreases, while a second terminal (B) of the inductor is switched to one of the output terminals at a time following a serving order during the charging part and following a reverse order during the discharging part, such that at the end of each serving interval of a terminal during the discharging part the current flowing in the inductor returns to the value it had at the beginning of a serving interval for the same output terminal during the charging part.
  11. The method of the preceding claim, in which the current flowing in the inductor in each cycle at the end of serving an output is reset to the same value it had at the beginning of serving the same output in the same cycle.
  12. The method of any one of claims 10-11, the output terminals being in number of two, three or more.
  13. The method of any one of claims 10-12, the cycle of the control circuit having a fixed frequency.
  14. The method of any one of claims 10-13, comprising activating a freewheeling mode when the inductor current reaches zero, in which the inductor is not connected to the output terminals and is short-circuited by a bypass switch.
  15. The method of any one of claims 10-14, comprising storing a value of the inductor current at the beginning of a serving of an output in the charging part and terminating a serving of the same output in the discharging part when the inductor current reaches the stored value, or the method comprising estimating a time when the inductor current serving an output in the discharging part will reach the same value it had at the beginning of serving the same output in the charging part and terminating a serving of the output at the estimated time.
  16. The method of any one of claims 10-15, comprising generating a timing signal for connecting the first terminal (A) to the higher potential or to the lower potential based on an error signal derived from the comparison of one output voltage with a reference value.

Description

Technical domain The present invention relates, in embodiments, to power supply and management circuits providing a plurality of power rails, as well as to an algorithm to generate a plurality of independent power levels in a circuit with a single storage inductor. Related art With increased complexity and integration, power management circuits are more and more required to provide several different power rails for different points of loads and different applications, each with a specific set of requirements. A single integrated circuit or chip may be required to supply power to external companion chips as well as to internal functions, such as low-power radios. These multifunction systems require stable power supplies for both the analogue circuitry and the digital section respecting strict EMI limits for the analogue/radio circuits and providing high-performance load regulation for the digital ones. Furthermore, high energy efficiency, adaptability of the voltage rails, low cost BOM are expected in most application, particularly in loT hardware. Meeting all these contrasting requirements is highly challenging. In today-s market, PMICs (Power Management Integrated Circuits) are highly popular for addressing these requirements. These PMICs often include multiple inductive DC/DC converters, LDOs and other auxiliary functions. These circuits provide significant advantages over single point-of-load (PoL) solution and discrete converter circuits of old. SIMO (single inductor, multiple output) converters promise even better BOM saving by requiring only one single inductor to provide multiple voltage rails. Document EP 4387073 A1 discloses a single-inductor, multiple-output DC-DC converter. Short disclosure of the invention An aim of the present invention is the provision of a multiple output voltage converter that overcomes at least some of the shortcomings and limitations of the state of the art. Embodiments of the invention provide superior performances both in terms of efficiency and of stability, while remaining simple enough for easy integration into high-volume production flows. According to the invention, these aims are attained by the object of the attached claims, and especially by a single-inductor multiple-output (SIMO) circuit having a modified buck topology in which multiple outputs are selectively and cyclically connectable to a single inductor, characterized in that a serving order of the outputs being reversed when the inductor is discharged, such that the inductor current at the end of the serving of an output can be reset to the same value that it had at the beginning of the serving of the same output in the same cycle. Dependent claims introduce important aspects of the invention that, while advantageous, are not essential. For example, a structure of a modified buck converter in which a first inductor terminal is connected to a left-side switching circuit with a half-bridge between a power supply terminal and ground, and a second terminal of the inductor is linked to an array of output switches, one per output. In embodiments, a controller circuit determines the timing of the various switches such that in a first charging part of each cycle the inductor current rises while the output terminals are served one after the other, and in a second discharging part of each cycle the output terminals are served in the reverse order while the inductor current decreases. The timing of the switches is such that at the end of each serving interval of a terminal during the discharging part the current flowing in the inductor returns to the value it had at the beginning of a serving interval for the same output terminal during the charging part. Many valuable use cases require two independent output terminals, but the number of outputs is not limited in the invention. They may be two, three or more. As to the switches, they may be implemented with MOS transistors. The converter may operate in a fixed-frequency cycle, which may be advantageous for EMI, or in a variable-frequency mode where needed. In the former case, it may be advantageous to introduce a freewheeling phase in each cycle, such that the converter can operate in discontinuous current mode at low load without changing the frequency. The freewheeling mode may be triggered by a zero current detector and involves isolating the inductor from the switching circuits on the right side or on both sides (the switches are put in a high-impedance state) and possibly activating a bypass switch short-cutting the inductor to allow the decay of residual currents. The timing of the charging part of each cycle may be determined by a modulator, such as a V-T converter, a PWM circuit, that operates on an error signal derived from the comparison of the output voltage with a reference value. This establishes a feedback control loop that regulates the output voltages at the desired values. PI or PID compensators may be included in the feedback loop. The invention als