GB2550222A

GB2550222A - Constant on time boost converter control

Info

Publication number: GB2550222A
Application number: GB1610243.6A
Authority: GB
Inventors: Wang Xiangcheng
Original assignee: Cirrus Logic International Semiconductor Ltd
Current assignee: Cirrus Logic International Semiconductor Ltd
Priority date: 2016-05-09
Filing date: 2016-06-13
Publication date: 2017-11-15
Anticipated expiration: 2036-06-13
Also published as: GB201610243D0; US20170324325A1; US10340796B2; GB2550222B

Abstract

A controller 116 for a switching converter (e.g. boost converter 102) includes: a current estimator to estimate current IL through an inductor 106; and a switch control to control activation and deactivation of at least one switch 108, 110 of the switching converter based on the estimated inductor current. The estimated inductor current is based upon a previous sample of a current through the inductor. A sense resistor 109 may be used to sense current Is flowing through a switch 108, wherein the current Is is indicative of the current IL flowing through the inductor when the switch 108 is closed. The switch control may also control activation and deactivation of the at least one switch based on a reference voltage formed by analogue-to-digital conversion of output voltages VOUT from a switched output stage 104. The reference voltage may be an audio signal or an ultrasonic signal.

Description

CONSTANT ON TIME BOOST CONVERTER CONTROL FTFT D OF DISCLOSURE

The present disclosure generally relates to integrated circuits, and, more particularly, to systems and methods for implementing a constant on time boost power converter of an electronic circuit.

BACKGROUND

Many electronic devices on the market today often use power converters to convert electric energy from one form to another (e.g., converting between alternating current and direct current), converting a voltage or current of an electrical signal, modifying a frequency of an electrical signal, or some combination of the above. Examples of power converters may include boost converters and buck converters. Such power converters are often used to convert an input voltage for other circuitry, wherein such converted voltage is greater than (e.g., if a boost converter is used) or less than (e.g., if a buck converter is used) the input voltage. For example, a boosted audio amplifier may include a boost converter for converting an input source voltage to produce a supply voltage for a switched output stage (e.g., a Class D of buck converter) of the amplifier.

SUMMARY

In accordance with the teachings of the present disclosure, certain disadvantages and problems associated with output signal integrity of a power converter have been reduced or eliminated.

In accordance with embodiments of the present disclosure, a controller for controlling at least one switch of a switching converter may include a current estimator configured to determine an estimated inductor current through an inductor of the switching converter based on a previous sample of a current through the inductor and a switch control configured to control activation and deactivation of the at least one switch based on the estimated inductor current.

In accordance with these and other embodiments of the present disclosure, a method may include determining an estimated inductor current through an inductor of a switching converter based on a previous sample of a current through the inductor and controlling activation and deactivation of the at least one switch based on the estimated inductor current.

In accordance with these and other embodiments of the present disclosure, a circuit may include a switching converter, a switched output stage coupled to the switching converter, wherein the switching converter generates a supply voltage to the switched output stage, and a controller for controlling at least one switch of a switching converter comprising a current estimator configured to determine an estimated inductor current through an inductor of the switching converter based on a previous sample of a current through the inductor and a switch control configured to control activation and deactivation of the at least one switch based on the estimated inductor current.

Technical advantages of the present disclosure may be readily apparent to one having ordinary skill in the art from the figures, description and claims included herein. The objects and advantages of the embodiments will be realized and achieved at least by the elements, features, and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description and the following detailed description are examples and explanatory and are not restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: FIGURE 1 illustrates an example circuit comprising a boost converter for converting an input source voltage to produce a supply voltage for a switched output stage of an amplifier, in accordance with embodiments of the present disclosure; FIGURE 2 illustrates a graph showing example waveforms for an output voltage of the switched output stage of FIGURE 1 and a supply voltage supplied to the switched output stage by the boost converter of FIGURE 1, in accordance with embodiments of the present disclosure; FIGURE 3 illustrates an example controller for controlling the boost converter of FIGURE 1, in accordance with embodiments of the present disclosure; and FIGURE 4 illustrates an example inductor current estimator of the controller depicted in FIGURE 3, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION FIGURE 1 illustrates an example circuit 100 comprising a boost converter 102 for converting an input source voltage Vbat to produce a supply voltage Vsupply for a switched output stage 104 of an amplifier (e.g., an audio amplifier), in accordance with embodiments of the present disclosure. As shown in FIGURE 1, boost converter 102 may comprise an inductor 106 coupled at a first terminal to an input source voltage Vbat and coupled at a second terminal to non-gate terminals of each of switches 108 and 110. Boost converter 102 shown in FIGURE 1 may also comprise a switch 108 (e.g., an n-type metal-oxide-semiconductor field effect transistor) coupled at one non-gate terminal to a ground voltage and coupled at its other non-gate terminal to inductor 106 and a non-gate terminal of switch 110, and a switch 110 (e.g., a p-type metal-oxide-semiconductor field effect transistor) coupled at one non-gate terminal to inductor 106 and a non-gate terminal of switch 108 and coupled at its other non-gate terminal to a terminal of capacitor 107. Boost converter 102 shown in FIGURE 1 may also include a capacitor 107 coupled between a non-gate terminal of switch 110 and a ground voltage. Furthermore, boost converter 102 may comprise a sense resistor 109 for sensing a current Is flowing through switch 108 (e.g., Is = Vs/Rs, where Vs is a voltage across sense resistor 109 and Rs is an electrical resistance of sense resistor 109). Such current Is may be indicative of a current II flowing through inductor 106 when switch 108 is closed.

Switched output stage 104 may include any suitable system, device, or apparatus configured to generate an output voltage Vout based on an input signal Vin provided to switched output stage 104, using electrical energy provided by supply voltage Vsupply provided by boost converter 102. For example, in some embodiments, switched output stage 104 may comprise a Class D output stage. In these and other embodiments, switched output stage 104 may comprise a buck converter. In some embodiments, output voltage Vout and input signal Vin may comprise audio signals. In other embodiments, output voltage Vout and input signal Vin may comprise ultrasonic signals.

Controller 116 may include any suitable system, device, or apparatus configured to, based on measured signals within circuit 100 (e.g., current Is, supply voltage Vsupply, output voltage Vout, input source voltage Vbat), drive a positive-polarity control voltage vcTRLP to the gate terminal of switch 110 and to drive a negative-polarity control voltage vcTEiLN to the gate terminal of switch 108. Each of positive-polarity control voltage vcTRLP and negative-polarity control voltage vcteiln may be pulse-width modulated signals. In steady-state operation, switch 108 will generally be open when switch 110 is closed, and vice versa (although, in some embodiments, a diode may be used in lieu of switch 110, wherein an anode of such diode may be coupled to inductor 106 and the cathode of such diode may be coupled to capacitor 107). When switch 108 is closed, current may flow from the voltage source generating the input source voltage Vbat through inductor 106, and inductor 106 may store energy. During this time, inductor 106 may have a voltage drop across it, with a positive-polarity at the terminal coupled to the input source voltage Vbat. When switch 108 is open and switch 110 is closed, the current flowing through inductor 106 may be reduced. Such change or reduction in current may be opposed by inductor 106 and the voltage polarity of inductor 106 may reverse (e.g., with a positive-polarity at the terminal coupled to generating the input source voltage Vbat). As a result, effectively two voltage sources are in series (input source voltage Vbat and the voltage across inductor 106), thus causing a voltage higher than Vbat to charge capacitor 107. If switches 108 and 110 are cycled fast enough, inductor 106 will not discharge fully in between charging stages, and the supply voltage Vsupply on capacitor 107 will have voltage greater than that of the input source voltage Vbat when switch 108 is opened. Thus, supply voltage Vsupply generated by boost converter 102 may be a function of positive-polarity control voltage vctrlp, negative-polarity control voltage vcTRLN, and the input source voltage Vbat.

In some embodiments, controller 116 may track an envelope of output voltage VouT, and for higher magnitudes of output voltage Vout (e.g., |Vour| > Vbat - AV, wherein AV is a headroom offset voltage), and controller 116 may cause supply voltage Vsupply to track the magnitude of output voltage Vout, such that supply voltage Vsupply is approximately equal to the magnitude of output voltage Vout plus the headroom offset voltage AV. Such envelope tracking may allow for a wide range of output voltage Vout while minimizing power consumption. FIGURE 2 illustrates a graph showing example waveforms for output voltage Vout and supply voltage Vsupply, in accordance with embodiments of the present disclosure. FIGURE 3 illustrates an example controller 116 for controlling boost converter 102, in accordance with embodiments of the present disclosure. As shown in FIGURE 3, analog voltages for input source voltage Vbat, sense resistor voltage Vs (indicative of current Is), supply voltage Vsupply, and output voltage Voux, may be respectively sampled by analog-to-digital converters 302, 304, 306, and 307 and converted into respective corresponding digital signals Vbat , Vs, Vsupply , and Vref, indicative of such voltages. In the case of output voltage Voux, analog-to-digital converter 307 may convert output voltage Voux into reference voltage signal Vref based on a magnitude of output voltage Voux. For example, in some embodiments, reference voltage signal Vref may equal the sum of output voltage Voux and headroom offset voltage AV. A current estimator 308 may comprise any suitable system, device or apparatus configured to, based on digital signals Vbax , Vs, and Vsupply , estimate inductor current II to generate an estimated voltage signal Vl_est, which represents a voltage induced across sense resistor 109 by inductor current II. While the digital signal Vs’ may itself alone be a voltage indicative of instantaneous inductor current II (which flows through sense resistor 109) during the duration of time during each switching cycle of boost converter 102 in which switch 108 is closed (e.g., Il = Is = Vs/Rs when switch 108 is closed), such is not the case when switch 108 is open as sense voltage Vs may be equal to zero when switch 108 is open, but inductor 106 may continue conducting current. Accordingly, when switch 108 is open, current estimator 308 may apply volt-second balance calculations, as described in greater detail below, to generate estimated current Il Esx during durations in which switch 108 is open. A charging phase estimator 310 may comprise any suitable system, device or apparatus configured to, based on digital signals Vbax and Vsupply , estimate a duration of time Ton during a switching cycle of boost converter 102 in which controller 116 should cause switch 108 to close (e.g., a charging phase in which switch 108 is closed and switch 110 is open such that inductor 106 charges). For example, duration Ton may be longer when supply voltage Vsupply is much greater than input source voltage Vbax, and shorter when supply voltage Vsupply is closer in magnitude to input source voltage Vbax. A combiner 312 may subtract digital signal Vsupply from the sum of reference voltage signal Vref and a slope compensation signal Sd, in order to generate a compensation signal Vc. Slope compensation signal Sd may compensate slope to provide for whole system stability of controller 116. Details and methods for such slope compensation are outside the scope of this disclosure. A comparator 314 may compare compensation signal Vc and estimated voltage Vl EST such that comparator 314 asserts its output (e.g., outputs a logic 1) when compensation signal Vc is larger than the product of estimated voltage Vl_est and deasserts its output (e.g., outputs a logic 0) otherwise. Assertion of the output of comparator 314 may trigger a pulse-width modulation generator 316 to output a pulse with a duration of time Ton such that pulse-width modulation generator 316 drives pulse-width modulated control voltage vctrln based on triggering from comparator 314 and a pulse width estimated by charging phase estimator 310. Controller 116 may also include a logic inverter 318 to a control voltage vctrlp as a complement to control voltage vctrln with certain non-overlapped time. FIGURE 4 illustrates an example inductor current estimator 308 of controller 116, in accordance with embodiments of the present disclosure. As shown in FIGURE 4, inductor current estimator 308 may include a trigger 402 that may receive estimated charging phase time Ton as its input and generate a trigger signal at a midpoint of such estimated charging phase time Ton. An analog-to-digital converter 404 may sample sense resistor voltage Vs responsive to such trigger, such that it outputs a digital signal Vl avg indicative of an average input current of inductor current II. A multiplexer 406 may pass zero during duration of time Ton, and output digital signal Vsupply otherwise. Such output of multiplexer 406 may be subtracted from digital signal Vbat by combiner 407 resulting in a signal indicative of a voltage across inductor 106 (e.g., such voltage equal to digital signal Vbat during estimated charging phase time Ton, otherwise such voltage equal to digital signal Vbat minus digital signal Vsupply . A preset gain block 408 may receive the signal output by combiner 407 and based thereon, apply a gain equal to a clock period of boost converter 102 divided by an inductance L of inductor 106 in order to generate a signal indicating an estimated slope (e g., change in current versus time) for the increasing inductor current II during duration of time Ton, and outside of estimated charging phase time Ton, generate a signal indicating an estimated slope for the decreasing inductor current II. An up/down counter 410 may receive digital signal Vl avg, the trigger signal generated by trigger 402, and the current slope signal output by preset gain block 408, and based thereon, generate estimated voltage signal Vl est indicative of an estimate of current II flowing through inductor 106. In operation, up/down counter 410 may increase estimated voltage Vl_est at the rate indicated by the slope output by preset gain block 408 (e.g., (Vbat *Tmclk/L) until the trigger 402 executes at the midpoint of estimated charging phase time Ton, at which the output of up/down counter 410 output is set to digital signal Vl avg indicative of the average current through inductor 106, after which and it continues to increase estimated voltage ViL EST at the rate indicated by the slope output by preset gain block 408 (e g., (Vbat *Tmclk/L) for the remainder of estimated charging phase time Ton. Outside of estimated charging phase time Ton, up/down counter 410 may decrease estimated voltage ViL EST at the rate indicated by the slope output by preset gain block 408 (e.g., ((Vbat -Vsupply’)*Tmclk/L). Any drift from ideal voltage-second balance may be addressed by resetting estimated voltage Vl est to digital signal Vl avg output at the midpoint of estimated charging phase time Ton, which may result in an accurate estimation of inductor current for loop controller 116.

As used herein, when two or more elements are referred to as “coupled” to one another, such term indicates that such two or more elements are in electronic communication whether connected indirectly or directly, without or without intervening elements.

This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.

All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the disclosure and the concepts contributed by the inventor to furthering the art, and are construed as being without limitation to such specifically recited examples and conditions. Although embodiments of the present disclosures have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.

Claims

WHAT IS CLAIMED IS:

1. A controller for controlling at least one switch of a switching converter, the controller comprising: a current estimator configured to determine an estimated inductor current through an inductor of the switching converter based on a previous sample of a current through the inductor; and a switch control configured to control activation and deactivation of the at least one switch based on the estimated inductor current.

2. The controller of Claim 1, further comprising a reference voltage input for receiving a reference voltage, and wherein the switch control is further configured to control activation and deactivation of the at least one switch based on the reference voltage.

3. The controller of Claim 2, wherein the reference voltage is an audio signal.

4. The controller of Claim 2, wherein the reference voltage is an ultrasonic signal.

5. The controller of Claim 1, wherein the switching converter is a boost converter for boosting an input voltage to a higher output voltage responsive to activation and deactivation of the at least one switch.

6. A method, comprising: determining an estimated inductor current through an inductor of a switching converter based on a previous sample of a current through the inductor; and controlling activation and deactivation of at least one switch based on the estimated inductor current.

7. The method of Claim 6, further comprising a reference voltage input for receiving a reference voltage, and wherein a switch control is further configured to control activation and deactivation of the at least one switch based on the reference voltage.

8. The method of Claim 7, wherein the reference voltage is an audio signal.

9. The method of Claim 7, wherein the reference voltage is an ultrasonic signal.

10. The method of Claim 6, wherein the switching converter is a boost converter for boosting an input voltage to a higher output voltage responsive to activation and deactivation of the at least one switch.

11. A circuit compri sing: a switching converter; a switched output stage coupled to the switching converter, wherein the switching converter generates a supply voltage to the switched output stage; and a controller for controlling at least one switch of a switching converter, the controller comprising: a current estimator configured to determine an estimated inductor current through an inductor of the switching converter based on a previous sample of a current through the inductor; and a switch control configured to control activation and deactivation of the at least one switch based on the estimated inductor current.

12. The circuit of Claim 11, further comprising a reference voltage input for receiving a reference voltage, and wherein the switch control is further configured to control activation and deactivation of the at least one switch based on the reference voltage.

13. The circuit of Claim 12, wherein the reference voltage is an audio signal.

14. The circuit of Claim 12, wherein the reference voltage is an ultrasonic signal.

15. The circuit of Claim 12, wherein the reference voltage is based on an output voltage generated by the switched output stage.

16. The circuit of Claim 11, wherein the switching converter is a boost converter for boosting an input voltage to a higher output voltage responsive to activation and deactivation of the at least one switch.