Converter with hysteretic control

Patent metadata

Field	Value
Publication number	US-8988056-B2
Application number	US-201213659046-A
Country	US
Kind code	B2
Filing date	Oct 24, 2012
Priority date	Oct 26, 2011
Publication date	Mar 24, 2015
Grant date	Mar 24, 2015

Abstract

A hysteretic power converter constituted of: a switched mode power supply; a hysteretic comparator, a first input of the comparator arranged to receive a feedback signal providing a representation of the output voltage of the switched mode power supply and a second input of the comparator arranged to receive a reference voltage; a ramp capacitor coupled to one of the first and second input of the comparator; a current source, a terminal of the current source coupled to the ramp capacitor and arranged to drive current to the ramp capacitor; and a switchable current source, a terminal of the switchable current source coupled to the ramp capacitor, the switchable current source arranged to drive current to the ramp capacitor in a direction opposite the current driven by the current source, wherein the switchable current source is alternately enabled and disabled responsive to the output of the hysteretic comparator.

First claim

The invention claimed is:

1. A hysteretic power converter comprising:
a switched mode power supply comprising an inductor, an electronically controlled switch and an output capacitor, said electronically controlled switch arranged to alternately open and close a loop with said inductor and leads of a power source;
a synchronization circuit arranged to synchronize said switched mode power supply with a periodic signal, said synchronization circuit arranged to close said electronically controlled switch responsive to each and every occurrence of a predetermined condition of the periodic signal;
a hysteretic comparator, a first input of said hysteretic comparator coupled to a feedback connection and arranged to receive from the feedback connection a feedback signal providing a representation of the voltage across said output capacitor, said electronically controlled switch opened responsive to the output of said hysteretic comparator;
a reference voltage source coupled to a second input of said hysteretic comparator and arranged to provide a reference voltage;
a ramp capacitor coupled to one of said reference voltage source and said feedback connection;
a current source, a terminal of said current source coupled to said ramp capacitor and arranged to drive current to said ramp capacitor;
a switchable current source, a terminal of said switchable current source coupled to said ramp capacitor, said switchable current source arranged to drive current to said ramp capacitor in a direction opposite the current driven by said current source, wherein said switchable current source is alternately enabled and disabled responsive to the output of said hysteretic comparator; and
an auto-zero circuit coupled across said ramp capacitor and arranged to set the average voltage across said ramp capacitor to zero.

2. The hysteretic power converter according to claim 1 , wherein said switchable current source is arranged to provide a current, when enabled, whose amplitude is a function of the voltage of the leads of the power source.

3. The hysteretic power converter according to claim 1 , wherein said current source is arranged to provide a current whose amplitude is a function of the reference voltage source.

4. The hysteretic power converter according to claim 1 , further comprising a voltage divider, an end of said voltage divider coupled to said output capacitor, the feedback connection being a connection to the common node of said voltage divider.

5. The hysteretic power converter according to claim 1 , wherein said switchable current source is enabled when said electronically controlled switch is closed, and disabled when said first electronically controlled switch is open.

6. The hysteretic power converter according to claim 1 , wherein said current source and said switchable current source are selected such that the average voltage across said ramp capacitor is zero.

7. The hysteretic power converter according to claim 6 , further comprising a ramp resistor coupled in parallel with said ramp capacitor.

8. A hysteretic power converter comprising:
a switched mode power supply comprising an inductor, an electronically controlled switch and an output capacitor, said electronically controlled switch arranged to alternately open and close a loop with said inductor and leads of a power source;
a hysteretic comparator, a first input of said hysteretic comparator coupled to a feedback connection and arranged to receive from the feedback connection a feedback signal providing a representation of the voltage across said output capacitor, said electronically controlled switch opened and closed responsive to the output of said hysteretic comparator;
a reference voltage source coupled to a second input of said hysteretic comparator and arranged to provide a reference voltage;
a ramp capacitor coupled to one of said reference voltage source and said feedback connection;
a current source, a terminal of said current source coupled to said ramp capacitor and arranged to drive current to said ramp capacitor;
a switchable current source, a terminal of said switchable current source coupled to said ramp capacitor, said switchable current source arranged to drive current to said ramp capacitor in a direction opposite the current driven by said current source, wherein said switchable current source is alternately enabled and disabled responsive to the output of said hysteretic comparator; and
an auto-zero circuit coupled across said ramp capacitor and arranged to set the average voltage across said ramp capacitor to zero,
wherein said auto-zero circuit comprises:
a first transconductance amplifier;
a second transconductance amplifier; and
an averaging capacitor,
a first input of said first transconductance amplifier coupled to a first end of said ramp capacitor and a second input of said first transconductance amplifier coupled to a second end of said ramp capacitor, the output of said first transconductance amplifier coupled to a first input of said second transconductance amplifier, said averaging capacitor coupled between the first input of said second transconductance amplifier and a second input of said second transconductance amplifier and arranged to reflect the average of the voltage across said ramp capacitor, the output of said second transconductance amplifier coupled to the first end of said ramp capacitor,
wherein in the event that the average voltage across said ramp capacitor increases, said second transconductance amplifier outputs a current so as to decrease the voltage across said ramp capacitor and in the event that the average voltage across said ramp capacitor decreases, said second transconductance amplifier outputs a current so as to increase the voltage across said ramp capacitor.

9. The hysteretic power converter according to claim 8 , further comprising a synchronization circuit arranged to synchronize said switched mode power supply with a periodic signal.

10. The hysteretic power converter according to claim 1 , wherein said synchronization circuit is further arranged to open said electronically controlled switch after expiration of a fixed maximum period.

11. The hysteretic power converter according to claim 1 , further comprising a slope compensation circuit.

12. A hysteretic power converter comprising:
a switched mode power supply comprising an inductor, an electronically controlled switch and an output capacitor, said electronically controlled switch arranged to alternately open and close a loop with said inductor and a power source;
a synchronization circuit arranged to synchronize said switched mode power supply with a periodic signal, said synchronization circuit arranged to close said electronically controlled switch responsive to each and every occurrence of a predetermined condition of the periodic signal;
a hysteretic comparator, a first input of said hysteretic comparator coupled to a feedback connection and arranged to receive from said feedback connection a feedback signal providing a representation of the voltage across said output capacitor, said electronically controlled switch opened responsive to the output of said hysteretic comparator;
a reference voltage source coupled to a second input of said hysteretic comparator and arranged to produce a reference voltage;
a ramp generator arranged to generate a ramp voltage added to one of said reference voltage and the feedback signal, said ramp generator comprising:
a current source, a switchable current source and a ramp capacitor, a terminal of each of said current source and said switchable current source coupled to said ramp capacitor, said current source and said switchable current source arrang

Assignees

• Microsemi Corp

Inventors

• Smith Jr Kevin Mark
• Cengelci Ekrem

Classifications

• H02M3/1588 Primary

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

• H02M2001/0016

  Electricity · mapped topic

• H02M2001/0025

  Electricity · mapped topic

• Y02B70/1466

  Cross-Sectional Technologies · mapped topic

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title