KR20170006363A - Circuit and method for detecting output voltage of flyback converter - Google Patents

Circuit and method for detecting output voltage of flyback converter Download PDF

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Publication number
KR20170006363A
KR20170006363A KR1020150096879A KR20150096879A KR20170006363A KR 20170006363 A KR20170006363 A KR 20170006363A KR 1020150096879 A KR1020150096879 A KR 1020150096879A KR 20150096879 A KR20150096879 A KR 20150096879A KR 20170006363 A KR20170006363 A KR 20170006363A
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KR
South Korea
Prior art keywords
inflection point
sawtooth wave
detected
signal
falling edge
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KR1020150096879A
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Korean (ko)
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남상국
김기현
김형우
서길수
이경호
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한국전기연구원
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Priority to KR1020150096879A priority Critical patent/KR20170006363A/en
Publication of KR20170006363A publication Critical patent/KR20170006363A/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M2001/0009—

Abstract

The present invention relates to a circuit and method for detecting output voltage of flyback converter. According to the present invention, a circuit for detecting output voltage of a flyback converter, which includes a primary coil, and a secondary coil and a sub coil guided by and combined with the primary coil, comprises: a falling edge detection unit detecting a falling edge of a gate voltage signal of a switching device connected to one end of the primary coil; an inflection detection unit detecting an inflection point of a feedback voltage signal applied to one end of the secondary sub coil; a sawtooth wave generation unit generating or resetting a sawtooth wave based on detection of the falling edge and the inflection point; a signal summation unit generating a correction signal summating the generated sawtooth wave and the feedback voltage signal; a peak value detection unit operated when the gate voltage signal is an off-state, so as to detect a peak value of the correction signal; and a sample and hold (S/H) circuit maintaining the peak value detected in a time point when the inflection point is detected until the next inflection point is detected. Thus, a section having secondary output voltage information of the flyback convert is controlled to always maintain the peak value, so output voltage information with high reliability can be detected and stable operation is realized in the whole circuit owing to improved regulation characteristics.

Description

TECHNICAL FIELD [0001] The present invention relates to an output voltage detecting circuit and a method of detecting an output voltage of a flyback converter.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output voltage sensing circuit and a sensing method for a flyback converter, and more particularly, To a sensing circuit and a sensing method that can be used.

Recently, due to the emergence of various electronic products such as smart phones and wearable appliances, the standby power problem of electronic devices has arisen, so that the standby power regulation is gradually increasing not only in domestic but also in the world. Therefore, There is increasing interest in flyback converters, which are very simple in configuration and low in cost.

Since the primary flyback converter is insulated by the transformer and the secondary side is insulated by the transformer, a direct detection method using an optocoupler has been used when detecting the output voltage information of the secondary side. For such a direct detection method, there is a need to add a secondary side control circuit, and there is a concern that an increase in standby power due to an increase in power loss is concerned. Accordingly, in recent years, a primary side control (PSR) scheme of a flyback converter that indirectly senses output voltage information of a flyback converter using an auxiliary winding has been extensively studied.

However, in the output voltage information sensing method using the conventional PSR method, if the sensing time of the circuit is short and the converter operates, if the time is delayed or if it senses a section ahead of the section to be sensed, The converter is detected to be higher or lower to exhibit unstable converter operation characteristics, resulting in lower reliability and reduced regulation characteristics, resulting in unstable operation of the entire circuit.

KR 10-2014-0001674 A

SUMMARY OF THE INVENTION It is an object of the present invention to provide an output voltage sensing circuit and a sensing method for a flyback converter capable of sensing stable output voltage information even if the sensing interval is delayed due to a delay in the circuit operation .

An output voltage sensing circuit of a flyback converter according to an aspect of the present invention is an output voltage sensing circuit of a flyback converter including a primary winding, a secondary winding wound inductively coupled to the primary winding, and a secondary auxiliary winding A falling edge sensing unit for sensing a falling edge of a gate voltage signal of a switching element connected to one end of the primary winding; An inflection point sensing unit for sensing an inflection point of a feedback voltage signal applied to one end of the secondary side auxiliary winding; A sawtooth wave generating unit for generating or resetting a sawtooth wave based on whether the falling edge and the inflection point are detected; A signal summing unit for generating a correction signal by summing the generated sawtooth wave and the feedback voltage signal; A peak value detector for detecting a peak value of the correction signal when the gate voltage signal is off; And an S / H circuit for holding the peak value detected at the time when the inflection point is sensed until the next inflection point is sensed.

According to another aspect of the present invention, there is provided a method of sensing an output voltage of a flyback converter including a primary winding, a secondary winding wound inductively coupled to the primary winding, and a secondary winding, The method comprising: sensing a falling edge of a gate voltage signal of a switching element connected to one end of the primary winding; Sensing an inflection point of a feedback voltage signal applied to one end of the secondary side auxiliary winding; Generating or resetting sawtooth based on whether the falling edge and the inflection point are detected; Generating a correction signal by summing the generated sawtooth wave and the feedback voltage signal; Detecting a peak value of the correction signal while the gate voltage signal is off; And maintaining the peak value detected at the time when the inflection point is sensed until the next inflection point is sensed.

According to the present invention, it is possible to detect the output voltage information with high reliability by controlling the interval in which the output voltage information of the secondary side of the flyback converter always maintains the peak value, and the regulation characteristic is improved, There is an effect that can be done.

1 is a circuit diagram of a flyback converter according to an embodiment of the present invention,
2 is a block diagram showing a configuration of an output voltage sensing circuit of a flyback converter according to an embodiment of the present invention,
3 is an internal circuit diagram of the sawtooth wave generator of FIG. 2,
4 is a graph showing signal waveforms according to an output voltage sensing method of a flyback converter according to an embodiment of the present invention.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. Like reference numerals refer to like elements throughout the specification.

FIG. 1 is a circuit diagram of a flyback converter according to an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of an output voltage sensing circuit of a flyback converter according to an embodiment of the present invention, FIG. 4 is a graph showing signal waveforms according to a method of sensing an output voltage of a flyback converter according to an embodiment of the present invention. Referring to FIG.

Hereinafter, a sensing circuit and a sensing method of a flyback converter according to an embodiment of the present invention will be described with reference to the drawings.

1, a flyback converter according to an embodiment of the present invention includes a primary winding 10, a secondary winding 20 inductively coupled to the primary winding 10, A winding 30 and a switching element SW for controlling the current flow of the primary winding 10.

For example, referring to FIG. 4, the currents (I ds , I D ) flowing in the primary winding 10 and the secondary winding 20 will be described below. Here, the turns ratio of the primary side winding 10, the secondary side winding 20 and the secondary side auxiliary winding 30 is N P : N S : N A.

First, when the switching element SW is turned on, a gate voltage V GS of a predetermined magnitude is applied to the switching element SW, and a current is charged in the primary winding 10 to be supplied to the primary winding 10 The flowing current I ds gradually increases.

Next, when the switching element SW is turned off, a gate voltage V GS of 0 is applied to the switching element SW, and a current I ds charged in the primary winding 10 is applied to the primary winding Side winding 20 and the secondary-side auxiliary winding 30, which are inductively coupled to the secondary winding 10. At this time, the current I d flowing through the secondary winding 20 gradually decreases because the primary winding 10 is no longer charged by the OFF operation of the switching element SW.

2, the sensing circuit for sensing the secondary side output voltage information in the flyback converter according to the present invention includes a falling edge sensing unit 100, an inflection point sensing unit 200, a sawtooth wave generating unit 300, A signal summing unit 400, a peak value detecting unit 500, and a S / H circuit 600.

The falling edge sensing unit 100 senses the falling edge of the gate voltage signal V GS of the switching device SW connected to one end of the primary winding 10.

Here, the gate voltage signal V GS may be in the form of a square wave having a first state value or a second state value corresponding to the on / off operation of the switching element SW.

For example, the gate voltage signal V GS indicates a first state value, that is, a predetermined voltage value when the switching element SW is in an on state, and a second state value , That is, a voltage value of zero.

The inflection point sensing unit 200 is for sensing the inflection point of the feedback voltage signal V FB applied to one end of the secondary side auxiliary winding 30.

Here, the feedback voltage signal V FB is generated when the switching element SW is turned off and the gate voltage signal V GS has a voltage value of 0, and the output of the secondary winding 20 May be a voltage value including a voltage (V o ) and a forward voltage (V f ) of a diode (D1) connected to one end of the secondary side auxiliary winding (30).

Here, the forward voltage V f of the diode D 1 gradually decreases due to the influence of the current I D flowing through the secondary winding 20, and when the current I D becomes 0, At this time, an inflection point of the feedback voltage signal V FB is formed.

The sawtooth wave generating unit 300 generates a sawtooth V saw based on whether the falling edge is detected by the falling edge detecting unit 100 and whether the inflection point is detected by the inflection point detecting unit 200 Or reset.

Here, the sawtooth wave generator 300 may generate the sawtooth wave when the falling edge is detected, and may reset the sawtooth wave when the inflection point is detected.

Specifically, the sawtooth wave generating unit 300 is set by a detection signal of the falling edge received from the falling edge sensing unit 100, and detects the inflection point received from the inflection point sensing unit 200 Lt; RTI ID = 0.0 > RESET < / RTI >

For example, referring to FIGS. 2 and 3, the sawtooth wave generator 300 generates a sawtooth wave from the falling edge detection unit 100 as a gate terminal of the discharge switch DSW, when the signal (V SAW _ ctl) is input, the discharging switch (DSW) is a capacitor (C) is turned off is connected to the output stage is to generate a sawtooth wave (V SAW) as the charge output to the signal summation unit (400) If the operation, and the discharge switch (DSW), the gate terminal to the inflection point detecting unit the inflection point on state saw tooth control signal (V SAW _ ctl) of a detection signal from the 200 in the input to the 'SET' state, the ground RESET 'state in which the sawtooth wave V SAW is reset as the discharge switch DSW is turned on and the capacitor C is discharged.

The signal summing unit 400 receives the sawtooth wave V saw generated by the sawtooth wave generator 300 and the feedback voltage signal V FB applied to one end of the secondary side auxiliary winding 30, To generate the signal V SUM .

The peak value detector 500 detects the peak value V PEAK of the correction signal V SUM generated by the signal summing unit 400 when the gate voltage signal V GS is off, will be.

Specifically, the peak value detector 500 is reset when the switching element SW is turned on and the gate voltage signal V GS indicates a predetermined value, and the switching element SW is turned off, And operates when the signal V GS becomes 0 to detect the peak value (V PEAK ) of the correction signal (V SUM ).

The S / H circuit 600 detects the peak value detected by the peak value detector 500 at the time when the inflection point of the feedback voltage signal V FB is detected by the inflection point sensing unit 200, To be sampled.

4 is a graph showing signal waveforms according to an output voltage sensing method of a flyback converter according to an embodiment of the present invention.

Hereinafter, a sawtooth wave voltage with reference to Figure 4 generated by the switching elements (SW) gate voltage (V GS) and the secondary side feedback voltage on the secondary winding (30) (V FB) and a sawtooth wave generator 300 of the ( held by the V SAW), and summing the voltage generated by the signal summation unit (400), (V sUM) and the peak voltage (V pEAK) and a S / H circuit 600 is detected by the peak value detector (500) The signal waveform of the output voltage V S / H will be described in detail as follows.

First, the gate voltage signal V GS indicates a first state value, that is, a voltage value of a predetermined magnitude when the switching element SW is in an on state, and a second state when the switching element SW is in an off state. Value, that is, a voltage value of zero.

Next, the feedback voltage signal (V FB ) is generated when the switching element (SW) is turned off and the gate voltage signal (V GS ) has a voltage value of 0, and the secondary winding And is transmitted to the secondary side auxiliary winding (30). At this time, the turns ratio of the secondary side winding 20 and the secondary side auxiliary winding 30 is N S : N A.

More specifically, the initial value of the feedback voltage signal V FB is a voltage obtained by adding the output voltage V o of the secondary winding 20 to the forward voltage V f of the diode Dl

Figure pat00001
When the forward voltage V f of the diode D 1 gradually decreases due to the influence of the current I D flowing through the secondary winding 20 to exhibit a value of 0, (V o ) applied to the secondary winding (20) at the time of forming the inflection point, the winding ratio
Figure pat00002
), And then decreases gradually while exhibiting an electric free vibration waveform.

Next, the saw-tooth voltage signal (V SAW), the falling edge detecting unit time when the falling edge of the gate voltage signal (V GS) occurs at 100, that is, the gate voltage signal (V GS) is a predetermined magnitude It is generated from the time it detects the time point is changed to zero in the voltage value by sawtooth control signal (V SAW _ ctl) of an off-state in which the output is inputted, the inflection point of the feedback voltage signal (V FB) at the inflection point detecting unit 200 forming time, i.e., the feedback voltage signal (V FB) the diode (D1) the forward voltage (V f) sawtooth control signal of the oN state and outputting the detection to the time representing the value of 0 to a gradual reduction in the contained in the is to be reset when the input (V SAW _ ctl).

Next, the summed voltage signal V SUM is obtained by correcting the feedback voltage signal V FB and the sawtooth voltage signal V saw as they are, and is gradually increased until the inflection point is detected after the initial generation. But gradually decreases from the inflection point to the electric free vibration waveform.

Next, the peak voltage signal (V PEAK ) is a waveform representing a peak value of the sum voltage (V SUM ) detected while the gate voltage signal (V GS ) is turned off, and gradually increases until the inflection point is detected The summed voltage V SUM at the point of time when the inflection point is sensed is maintained as it is after the detection point of the inflection point.

Next, the output voltage V S / H is sampled and maintained until the next inflection point is detected, when the inflection point is detected, and the peak value detected by the peak value detector 500.

Accordingly, it is possible to detect the output voltage information with high reliability by controlling the interval in which the output voltage information of the secondary side of the flyback converter always maintains the peak value, and the regulation characteristic can be improved, There is an effect.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

10: Primary winding 20: Secondary winding
30: secondary side auxiliary winding 100: falling edge detection unit
200: inflection point sensing unit 300: sawtooth wave generating unit
400: Signal summation unit 500: Peak value detection unit
600: S / H circuit

Claims (5)

1. An output voltage sensing circuit of a flyback converter including a primary winding, a secondary winding wound inductively coupled to the primary winding, and a secondary auxiliary winding,
A falling edge detecting unit for detecting a falling edge of a gate voltage signal of a switching element connected to one end of the primary winding;
An inflection point sensing unit for sensing an inflection point of a feedback voltage signal applied to one end of the secondary side auxiliary winding;
A sawtooth wave generating unit for generating or resetting a sawtooth wave based on whether the falling edge and the inflection point are detected;
A signal summing unit for generating a correction signal by summing the generated sawtooth wave and the feedback voltage signal;
A peak value detector for detecting a peak value of the correction signal when the gate voltage signal is off; And
And an S / H circuit for holding the peak value detected at the time when the inflection point is sensed until the next inflection point is sensed. The sawtooth wave generator according to claim 1,
Generates the sawtooth wave when the falling edge is detected, and resets the sawtooth wave when the inflection point is detected. The sawtooth wave generator according to claim 2,
And an SR latch which is set by a sense signal of the falling edge and is reset by a sense signal of the inflection point. A method for detecting an output voltage of a flyback converter including a primary winding, a secondary winding wound inductively coupled to the primary winding, and a secondary winding,
Sensing a falling edge of a gate voltage signal of a switching element connected to one end of the primary winding;
Sensing an inflection point of a feedback voltage signal applied to one end of the secondary side auxiliary winding;
Generating or resetting sawtooth based on whether the falling edge and the inflection point are detected;
Generating a correction signal by summing the generated sawtooth wave and the feedback voltage signal;
Detecting a peak value of the correction signal while the gate voltage signal is off; And
And maintaining the peak value detected at the time when the inflection point is sensed until the next inflection point is sensed. 5. The method of claim 4,
The step of generating or resetting the sawtooth wave includes:
Wherein the sawtooth wave is generated when the falling edge is detected, and the sawtooth wave is reset when the inflection point is detected.
KR1020150096879A 2015-07-08 2015-07-08 Circuit and method for detecting output voltage of flyback converter KR20170006363A (en)

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20140001674A (en) 2012-06-28 2014-01-07 삼성전기주식회사 Pwm control circuit for dc-dc converter, flyback converter and method for pwm controlling dc-dc converter

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20140001674A (en) 2012-06-28 2014-01-07 삼성전기주식회사 Pwm control circuit for dc-dc converter, flyback converter and method for pwm controlling dc-dc converter

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