Soft start controller of a converter

Patent metadata

Field	Value
Publication number	US-9716436-B2
Application number	US-201514630902-A
Country	US
Kind code	B2
Filing date	Feb 25, 2015
Priority date	Oct 24, 2014
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A DC-to-DC converter includes first and second switches. If on, the first switch provides a signal path through a common node to an output voltage node. If on, the second switch provides a signal path through the common node to the output voltage node. Control logic provides first and second control signals to control the first and second switches. A node produces a first voltage that ramps up from zero during initialization, and a soft start controller controls the second control signal while the first voltage is not greater than a predefined level. While the first voltage is not greater than the predefined level, the soft start controller keeps the second control signal at a higher level to maintain on the second switch, and transitions the second control signal to a lower level only when the first control signal transitions from a lower level to a higher level.

First claim

What is claimed is:

1. A DC-to-DC converter, comprising:
a first switch connected to an input voltage node and a common node, the first switch configured to provide a signal path between the input voltage node and an output voltage node of the DC-to-DC converter through the common node when the first switch is turned on;
a second switch connected to a ground node and the common node, the second switch is configured to provide a signal path between the ground node and the output voltage node of the DC-to-DC converter through the common node when the second switch is turned on; and
a control logic coupled to the first and second switches, the control logic configured to provide a first control signal and a second control signal to control the first and the second switches respectively, wherein a falling edge of the second control signal is aligned with a rising edge of the first control signal and a duty cycle of the second control signal is varied over time in a non-complementary manner when compared with a duty cycle of the first control signal while a voltage level of a first node of the DC-to-DC converter is less than a predefined level, the first node is a soft start voltage node.

2. The DC-to-DC converter of claim 1 further comprising:
the first node configured to produce a first voltage that ramps up from zero during initialization.

3. The DC-to-DC converter of claim 2 further comprising:
a first soft start controller coupled to the control logic, the first soft start controller configured to control the duty cycle of the second control signal.

4. The DC-to-DC converter of claim 3 , wherein while the first voltage is less than the predefined level, the first soft start controller is configured to determine the duty cycle of the second control signal based on a slope, wherein the slope is based on a difference between an input voltage of the input voltage node and a non-zero voltage level of the output voltage node.

5. The DC-to-DC converter of claim 4 , wherein the first soft start controller comprises a comparator configured to compare the slope with a sawtooth signal to determine the duty cycle of the second control signal.

6. The DC-to-DC converter of claim 3 further comprising:
an inductor connected to the common node and the output voltage node, wherein the first soft start controller controls the second control signal to enable current flowing through the inductor to be sensed by a first current sensing circuit and a second current sensing circuit coupled to the first and second switches respectively.

7. The DC-to-DC converter of claim 3 , wherein, when the first voltage reaches the predefined level, the duty cycle of the second control signal is varied with a duty cycle of the first control signal in a complementary manner, and wherein the first control signal is controlled by a second soft start controller.

8. The DC-to-DC converter of claim 1 , wherein the first and second control signals are pulse width modulated signals, each of which is associated with a duty cycle of the respective switch.

9. A voltage regulator, comprising:
a first switch connected to an input voltage node and a common node, the first switch is configured to provide a signal path between the input voltage node and an output voltage node of the voltage regulator through the common node when the first switch is turned on;
a second switch connected to a ground node and the common node, the second switch configured to provide a signal path between the ground node and the output voltage node of the voltage regulator through the common node when the second switch is turned on;
a control logic configured to provide a first and a second control signals to control the first and second switches respectively;
a first soft start controller coupled to the control logic and configured to determine the second control signal while a first voltage is less than a predefined level, the first voltage ramps up from zero during initialization; and
a second soft start controller coupled to the control logic, and configured to determine the first and second control signals while the first voltage is greater than the predefined level;
wherein a falling edge of the second control signal is aligned with a rising edge of the first control signal and a duty cycle of the second control signal is varied over time in a non-complementary manner when compared with a duty cycle of the first control signal while the first voltage is less than the predefined level.

10. The voltage regulator of claim 9 , wherein the first and second control signals are pulse width modulated signals, each of which is associated with a duty cycle of the respective switch.

11. The voltage regulator of claim 10 , wherein the first soft start controller is configured to determine the duty cycle of the second control signal based on a slope, wherein the slope is proportional to a difference between a voltage level at the input voltage node and a voltage level at the output voltage node.

12. The voltage regulator of claim 11 , wherein the first soft start controller further comprises a comparator configured to compare the slope with a sawtooth signal to determine the duty cycle of the second control signal.

13. The voltage regulator of claim 9 further comprising:
an inductor coupled to the output voltage node, wherein the first soft start controller controls the second control signal to enable current flowing through the inductor to be sensed by a first current sensing circuit and a second current sensing circuit coupled to the first and second switches respectively.

14. The voltage regulator of claim 9 , wherein when the first voltage reaches the predefined level, the duty cycle of the second control signal is varied with a duty cycle of the first control signal in a complementary manner.

15. A method, comprising:
receiving, by a soft start controller, voltage levels at an input voltage node and an output voltage node of a DC-to-DC converter;
determining, by the soft start controller, a duty cycle of a low side control signal for controlling a low side switch of the DC-to-DC converter;
controlling, by the soft start controller, a falling edge of the low side control signal to align with a rising edge of a high side control signal, the high side control signal being used to control a high side switch of the DC-to-DC converter; and
varying the duty cycle of the low side control signal over time in a non-complementary manner when compared with a duty cycle of the high side signal while a voltage level of a first node of the DC-to-DC converter is less than a predefined level, the first node is a soft start voltage node.

16. The method of claim 15 , wherein the duty cycle of the low side control signal is determined based on a slope, wherein the slope is proportional to a difference between the voltage level at the input voltage node and the voltage level at the output voltage node.

17. The method of claim 15 , wherein the duty cycle of the low side control signal is varied in a complementary manner when compared to the duty cycle of the high side signal when the voltage level of the first node of the DC-to-DC converter is greater than the predefined level.

Assignees

• Texas Instruments Inc

Inventors

• Xu Xiaojun
• Jiang Nan
• Dong Xianhui

Classifications

• H02M1/36

  Means for starting or stopping converters · CPC title

• H02M2001/0009

  Electricity · mapped topic

• H02M3/1588 Primary

  comprising at least one synchronous rectifier element (H02M3/1582, H02M3/1584 take precedence) · CPC title

• H02M3/158 Primary

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

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title