Buck-boost converter

Patent metadata

Field	Value
Publication number	US-10355596-B2
Application number	US-201615232361-A
Country	US
Kind code	B2
Filing date	Aug 9, 2016
Priority date	Nov 30, 2015
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

A buck-boost converter and a method are presented. The buck-boost converter comprises an inductor, a buck converter, and a boost converter. The buck converter controls switches according to a buck duty cycle, whereas the boost converter controls switches according to a boost duty cycle. The converter contains a voltage feedback loop for regulating an output voltage of the converter. A buck comparator generates the buck duty cycle signal by comparing the error voltage with a ramp voltage. A boost comparator generates the boost duty cycle signal by comparing a boost error voltage with the ramp voltage, wherein the boost error voltage is indicative of a sum of the error voltage and an offset voltage and the boost ramp voltage is indicative of a sum of the ramp voltage and the offset voltage. There is a duty cycle feedback loop for adjusting the buck and boost duty cycles.

First claim

What is claimed is:

1. A buck-boost converter with
an inductor;
a buck converter comprising a first switch and a second switch which are coupled to an input terminal of the inductor, the buck converter configured to control the first switch and the second switch according to a buck duty cycle based on a buck duty cycle signal;
a boost converter comprising a third switch and a fourth switch which are coupled to an output terminal of the inductor, the boost converter configured to control the third switch and the fourth switch according to a boost duty cycle based on a boost duty cycle signal;
a voltage feedback loop for regulating an output voltage at an output of the buck-boost converter, the voltage feedback loop comprising:
an error voltage determination unit configured to determine an error voltage indicative of a difference between the output voltage and a target voltage,
a buck comparator configured to generate the buck duty cycle signal by comparing the error voltage with a ramp voltage generated by a ramp voltage generator, and
a boost comparator configured to generate the boost duty cycle signal by comparing a boost error voltage with the ramp voltage or by comparing the error voltage with a boost ramp voltage, wherein the boost error voltage is indicative of a sum of the error voltage and an offset voltage and the boost ramp voltage is indicative of a sum of the ramp voltage and the offset voltage; and
a duty cycle feedback loop for adjusting the buck duty cycle and the boost duty cycle, the duty cycle feedback loop comprising an offset voltage determination unit connected to an output of the buck comparator for receiving the buck duty cycle signal and connected to an output of the boost comparator for receiving the boost duty cycle signal, wherein the offset voltage determination unit is configured to determine the offset voltage based on the received buck duty cycle signal generated by the buck comparator and based on the received boost duty cycle signal generated by the boost comparator,
wherein the offset voltage determination unit is configured to determine the offset voltage such that the boost duty cycle is regulated towards a minimum boost duty cycle or such that the buck duty cycle is regulated towards a maximum buck duty cycle.

2. The buck-boost converter according to claim 1 , wherein the offset voltage determination unit is configured to determine the offset voltage such that the boost duty cycle is regulated towards a minimum boost duty cycle when a buck duty cycle is smaller than a maximum buck duty cycle.

3. The buck-boost converter according to claim 2 , wherein the offset voltage determination unit comprises a duty cycle selector and a control unit, and the duty cycle selector is configured to couple, when the buck duty cycle is smaller than the maximum buck duty cycle, the boost duty cycle signal as a controlled variable to the control unit and the minimum boost duty cycle as a set point to the control unit, and the control unit is configured to determine the offset voltage based on the boost duty cycle signal and the minimum boost duty cycle.

4. The buck-boost converter according to claim 1 , wherein the offset voltage determination unit is configured to determine the offset voltage such that the buck duty cycle is regulated towards a maximum buck duty cycle when a buck duty cycle is larger than a maximum buck duty cycle.

5. The buck-boost converter according to claim 1 , wherein the offset voltage determination unit is configured to determine the offset voltage such that the boost duty cycle is regulated towards a minimum boost duty cycle when a boost duty cycle of the boost converter is smaller than the minimum boost duty cycle.

6. The buck-boost converter according to claim 1 , wherein the offset voltage determination unit comprises at least one of a proportional, an integral and a derivative controller.

7. The buck-boost converter according to claim 1 , wherein the offset voltage determination unit comprises a loop filter configured to smooth the offset voltage at an output of the offset determination unit.

8. The buck-boost converter according to claim 1 , wherein the offset voltage determination unit forms part of a delay line loop DLL.

9. The buck-boost converter according to claim 1 , wherein the buck-boost converter is configured to switch each of the four switches once per clock cycle from an on-state to an off-state or vice versa.

10. The buck-boost converter according to claim 1 , wherein the buck duty cycle and the boost duty cycle are synchronized by a clock signal.

11. The buck-boost converter according to claim 1 , further comprising an error adder unit coupled to an output of the offset voltage determination unit and to an output of the error voltage determination unit, the error adder unit configured to generate the boost error voltage by adding the offset voltage and the error voltage, and to apply the boost error voltage an input of the boost comparator.

12. A buck-boost converter with
an inductor;
a buck converter comprising a first switch and a second switch which are coupled to an input terminal of the inductor, the buck converter configured to control the first switch and the second switch according to a buck duty cycle based on a buck duty cycle signal;
a boost converter comprising a third switch and a fourth switch which are coupled to an output terminal of the inductor, the boost converter configured to control the third switch and the fourth switch according to a boost duty cycle based on a boost duty cycle signal;
a voltage feedback loop for regulating an output voltage at an output of the buck-boost converter, the voltage feedback loop comprising:
an error voltage determination unit configured to determine an error voltage indicative of a difference between the output voltage and a target voltage,
a buck comparator configured to generate the buck duty cycle signal by comparing the error voltage with an inductor input voltage indicative of a current at the input terminal of the inductor, and
a boost comparator configured to generate the boost duty cycle signal by comparing a boost error voltage with an inductor output voltage or by comparing the error voltage with a boost inductor output voltage, wherein the inductor output voltage is indicative of a current at the output terminal of the inductor, the boost error voltage is indicative of a sum of the error voltage and an offset voltage, and the boost inductor output voltage is indicative of a sum of the inductor output voltage and the offset voltage; and
a duty cycle feedback loop for adjusting the buck duty cycle and the boost duty cycle, the duty cycle feedback loop comprising an offset voltage determination unit connected to an output of the buck comparator for receiving the buck duty cycle signal and connected to an output of the boost comparator for receiving the boost duty cycle signal, wherein the offset voltage determination unit is configured to determine the offset voltage based on the received buck duty cycle signal generated by the buck comparator and based on the received boost duty cycle signal generated by the boost comparator,
wherein the offset voltage determination unit is configured to determine the offset voltage such that the boost duty cycle is regulated towards a minimum boost duty cycle or such that the buck duty cycle is regulated towards a maximum buck duty cycle.

13. A method for operating a buck-boost converter with an inductor, a buck converter comprising a first switch and a second switch which are coupled to an input terminal of the inductor, and a boost converter comprising a third switch and a fourth switch which

Assignees

• Dialog Semiconductor Uk Ltd

Inventors

• Choquet Frederic

Classifications

• H02M3/1582 Primary

  Buck-boost converters (H02M3/1584 takes precedence) · CPC title

• H02M3/158

  including plural semiconductor devices as final control devices for a single load · CPC title