US 5,631,810 AGranted

Control of switching devices in synchronized-rectification system

AssigneeNEC Corporation

InventorYoshinori Takano

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Abstract

A switch controller in a DC--DC converter performs the switching control of a primary switch and a freewheel switch which are connected to the primary and the secondary of a transformer, respectively. The switch controller comprises a control voltage generator for generating two control voltages having a predetermined voltage difference, a triangular-wave oscillator for generating a triangular-wave voltage, and a control pulse generator for generating two control pulse signals which cause the primary switch and the freewheel switch to alternately turn on and off such that both the primary switch and the freewheel switch become off during a certain period when one of the primary switch and the freewheel switch is turned off.

Claims20

Dependent claims

A controller for performing control of a primary switch and a freewheel switch provided in a DC--DC converter, said primary switch connected to the primary of a transformer, and said freewheel switch connected to the secondary of said transformer, said controller comprising:

control voltage generating means for generating a first control voltage and a second control voltage which have a predetermined voltage difference, said first control voltage being associated with said primary switch, and said second control voltage being associated with said freewheel switch;
periodic voltage generating means for generating a periodic varying voltage having a predetermined inclination in voltage;
detecting means for detecting a time instant at which said periodic varying voltage reaches a start voltage selected from a peak voltage and a bottom voltage of said periodic varying voltage;
comparing means for comparing said periodic varying voltage with each of said first control voltage and said second control voltage, generating a first timing signal when said periodic varying voltage reaches said first control voltage from said start voltage, and generating a second timing signal when said periodic varying voltage reaches said second control voltage from said start voltage;
state retaining means for retaining a first output signal and a second output signal at one of an active state and an inactive state based on said time instant, said first timing signal and said second timing signal, said first output signal and said second output signal concurrently changing to said active state and said inactive state at said time instant, respectively, said first output signal changing from said active state to said inactive state when receiving said first timing. signal from said comparing means, and said second output signal changing from said inactive state to said active state when receiving said second timing signal from said comparing means;
and
driving means for driving said primary switch and said freewheel switch according to said first output signal and said second output signal, respectively, such that said primary switch is on when said first output signal is active, said freewheel switch is on when said second output signal is active, said primary switch is off when said first output signal is inactive, and said freewheel switch is off when said second output signal is inactive.

4 more elements

A DC--DC converter comprising:

a transformer for transferring an electrical energy from a DC power supply to a load;
a first switch connected to the primary of said transformer, for switching on and off according to a first control pulse signal to supply said electrical energy to said transformer;
a rectifier connected to the secondary of said transformer, for rectifying an output of said transformer;
a second switch connected to said secondary of said transformer through said rectifier, for switching on and off according to a second control pulse signal;
a smoothing circuit connected to said second switch, comprising an element for storing said electrical energy output from said rectifier;
control voltage generating means for generating a first control voltage and a second control voltage lower than said first control voltage by a predetermined voltage, both said first control voltage and said second control voltage varying according to a DC output voltage of said smoothing circuit;
periodic voltage generating means for generating a periodic varying voltage having a predetermined inclination in voltage;
detecting means for detecting a time instant at which said periodic varying voltage reaches a start voltage selected from a peak voltage and a bottom voltage of said periodic varying voltage;
comparing means for comparing said periodic varying voltage with each of said first control voltage and said second control voltage, generating a first timing signal when said periodic varying voltage reaches said first control voltage from said start voltage, and generating a second timing signal when said periodic varying voltage reaches said second control voltage from said start voltage;
state retaining means for retaining a first output signal and a second output signal at one of an active state and an inactive state based on said time instant, said first timing signal and said second timing signal, said first output signal and said second output signal concurrently changing to said active state and said inactive state at said time instant, respectively, said first output signal changing from said active state to said inactive state when receiving said first timing signal from said comparing means, and said second output signal changing from said inactive state to said active state when receiving said second timing signal from said comparing means;
and
driving means for driving said primary switch and said freewheel switch according to said first output signal and said second output signal, respectively, such that said primary switch is on when said first output signal is active, said freewheel switch is on when said second output signal is active, said primary switch is off when said first output signal is inactive, and said freewheel switch is off when said second output signal is inactive.

9 more elements

A control method of a primary switch and a freewheel switch provided in a DC--DC converter, said primary switch connected to the primary of a transformer, and said freewheel switch connected to the secondary of said transformer, said method comprising the steps of:

generating a first control voltage and a second control voltage which have a predetermined voltage difference, said first control voltage being associated with said primary switch, and said second control voltage being associated with said freewheel switch;
generating a periodic varying voltage having a predetermined inclination in voltage;
detecting a time instant at which said periodic varying voltage reaches a start voltage selected from a peak voltage and a bottom voltage of said periodic varying voltage;
comparing said periodic varying voltage with each of said first control voltage and said second control voltage to generate a first timing signal when said periodic varying voltage reaches said first control voltage from said start voltage and to generate a second timing signal when said periodic varying voltage reaches said second control voltage from said start voltage;
retaining a first output signal and a second output signal at one of an active state and an inactive state based on said time instant, said first timing signal and said second timing signal, said first output signal and said second output signal concurrently changing to said active state and said inactive state at said time instant, respectively, said first output signal changing from said active state to said inactive state when said first timing signal is generated, and said second output signal changing from said inactive state to said active state when said second timing signal is generated;
and
driving said primary switch and said freewheel switch according to said first output signal and said second output signal, respectively, such that said primary switch is on when said first output signal is active, said freewheel switch is on when said second output signal is active, said primary switch is off when said first output signal is inactive, and said freewheel switch is off when said second output signal is inactive.

4 more elements

Dependencies are inferred from the claim text.

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Abstract

control voltage generating means for generating a first control voltage and a second control voltage which have a predetermined voltage difference, said first control voltage being associated with said primary switch, and said second control voltage being associated with said freewheel switch;
periodic voltage generating means for generating a periodic varying voltage having a predetermined inclination in voltage;
detecting means for detecting a time instant at which said periodic varying voltage reaches a start voltage selected from a peak voltage and a bottom voltage of said periodic varying voltage;
comparing means for comparing said periodic varying voltage with each of said first control voltage and said second control voltage, generating a first timing signal when said periodic varying voltage reaches said first control voltage from said start voltage, and generating a second timing signal when said periodic varying voltage reaches said second control voltage from said start voltage;
state retaining means for retaining a first output signal and a second output signal at one of an active state and an inactive state based on said time instant, said first timing signal and said second timing signal, said first output signal and said second output signal concurrently changing to said active state and said inactive state at said time instant, respectively, said first output signal changing from said active state to said inactive state when receiving said first timing. signal from said comparing means, and said second output signal changing from said inactive state to said active state when receiving said second timing signal from said comparing means;
and
driving means for driving said primary switch and said freewheel switch according to said first output signal and said second output signal, respectively, such that said primary switch is on when said first output signal is active, said freewheel switch is on when said second output signal is active, said primary switch is off when said first output signal is inactive, and said freewheel switch is off when said second output signal is inactive.

4 more elements