US 8,044,641 B2 · Step-down switching regulator with turn off undershoot prevention

Abstract

A step-down switching regulator prevents an output voltage undershoot and enables a quick lowering of an output voltage immediately after turning off of power supply. The step-down switching regulator includes an NMOS transistor connected between an output terminal and a ground voltage and another NMOS transistor connected in parallel with a synchronous rectification transistor. Upon reception of an on/off signal for terminating the operation of the switching regulator, the NMOS transistors are turned on into an on-state.

Drawings

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Drawings

Claims5

Dependent claims

A synchronous-rectification-type step-down switching regulator for converting an input voltage at an input terminal of the switching regulator into a predetermined constant voltage that is applied to a load connected at an output terminal of the switching regulator,

the switching regulator comprising:
a first switching element configured to perform a switching in accordance with a control signal;
an inductor that is charged by the input voltage when the first switching element performs the switching;
a second switching element for synchronous rectification configured to discharge the inductor by performing a switching in accordance with the control signal;
a control circuit unit configured to control the switching of the first switching element in order to obtain the predetermined constant voltage at the output terminal, the control circuit also being configured to cause the second switching element to perform the switching in an opposite manner to the switching of the first switching element;
and
a short-circuiting unit configured to connect the output terminal to a ground voltage and also short-circuit the second switching element when the control circuit unit is deactivated.

4 more elements

the switching regulator comprising:
a first switching element configured to perform a switching in accordance with a control signal;
an inductor that is charged by the input voltage when the first switching element performs the switching;
a second switching element for synchronous rectification configured to discharge the inductor by performing a switching in accordance with the control signal;
a control circuit unit configured to control the switching of the first switching element in order to obtain the predetermined constant voltage at the output terminal, the control circuit also being configured to cause the second switching element to perform the switching in an opposite manner to the switching of the first switching element;
a short-circuiting unit configured to connect the output terminal to a ground voltage when the control circuit unit is deactivated;
and
a voltage detecting circuit unit configured to detect a voltage at a connecting portion between the inductor and the second switching element,
wherein the voltage detecting circuit unit, when the voltage at the connecting portion between the inductor and the second switching element is a negative voltage, turns on the second switching element into a conducting state upon reception of an external signal for terminating the operation of the control circuit unit.

6 more elements

Dependencies are inferred from the claim text.

Description5,073 words

Summary1,334 words

#1. Field of the Invention

#The present invention generally relates to step-down switching regulators for supplying power to electronic devices. Particularly, the invention relates to technologies for protecting a power supply circuit and a load circuit upon termination of power supply by quickly lowering a voltage applied to an electronic circuit and preventing the development of an output voltage undershoot due to an inductor.

#2. Description of the Related Art

Brief description of the drawings6 figures

#These and other objects, features and advantages of the invention will be apparent to those skilled in the art from the following detailed description of the invention, when read in conjunction with the accompanying drawings in which:

#FIG. 1 shows a circuit diagram of a step-down switching regulator according to a first embodiment of the present invention;

#FIG. 2 shows a timing chart illustrating waveforms of various signals in the switching regulator shown in FIG. 1;

Detailed description3,584 words

#In the following, preferred embodiments of the present invention are described with reference to the drawings.

#FIG. 1 shows a circuit diagram of a step-down switching regulator 1 according to a first embodiment of the present invention.

#The step-down switching regulator 1 is of a synchronous rectification type whereby an input voltage Vin at an input terminal IN is converted into a predetermined constant voltage in order to produce an output voltage Vout at an output terminal OUT that is applied to a load 10.

Facts

Application

12/364,748Filed 3 Feb 2009

Priority

JP 2008-04602327 Feb 2008

Published

US 2009/0213631 A127 Aug 2009

Granted

25 Oct 2011

Term ends

1 May 2030

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 452 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification3 codes

H02M 1/36
Details of apparatus for conversion: means for starting or stopping converters
H02M 1/32
Details of apparatus for conversion: means for protecting converters other than automatic disconnection
H02M
Apparatus for conversion between ac and ac, between ac and dc, or

Timeline

27 Feb 2008Priority claimedJP 2008-046023
3 Feb 2009Application filedUS 12/364,748
4 Feb 2009Assigned to Ricoh Company, Ltd.assignment of assignor's interest
27 Aug 2009PublishedUS 2009/0213631 A1
25 Oct 2011GrantedUS 8,044,641 B2
18 Feb 2015Assigned to Ricoh Electronic Devices Co., Ltd.assignment of assignor's interest
14 Feb 2022Assigned to New Japan Radio Co., Ltd.merger
3 Mar 2022Assigned to Nisshinbo Micro Devices Inc.change of name
12 Oct 2026TodayWithin its term
1 May 2030Term endsEstimated, includes 452 days of adjustment

Step-down switching regulator with turn off undershoot prevention

Life of this patent

Step-down switching regulator with turn off undershoot prevention

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims5

Description5,073 words

Drawings

Classification3 codes

Life of this patent

Description5,073 words