US20160087534A1 - Methods and power controllers for primary side control - Google Patents

Methods and power controllers for primary side control Download PDF

Info

Publication number
US20160087534A1
US20160087534A1 US14/960,452 US201514960452A US2016087534A1 US 20160087534 A1 US20160087534 A1 US 20160087534A1 US 201514960452 A US201514960452 A US 201514960452A US 2016087534 A1 US2016087534 A1 US 2016087534A1
Authority
US
United States
Prior art keywords
voltage
feedback
power switch
switching frequency
over
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US14/960,452
Inventor
Yu-Yun Huang
Yi-Lun Shen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Leadtrend Technology Corp
Original Assignee
Leadtrend Technology Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Leadtrend Technology Corp filed Critical Leadtrend Technology Corp
Priority to US14/960,452 priority Critical patent/US20160087534A1/en
Assigned to LEADTREND TECHNOLOGY CORP. reassignment LEADTREND TECHNOLOGY CORP. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HUANG, YU-YUN, SHEN, Yi-lun
Publication of US20160087534A1 publication Critical patent/US20160087534A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • 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
    • H02M3/33507—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 with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—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 with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • 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
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4258—Arrangements for improving power factor of AC input using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Definitions

  • the present invention relates to a primary side control (PSC) switching-mode power supply (SMPS), and particularly to a PSC SMPS that has reduced output voltage jitter.
  • PSC primary side control
  • SMPS switching-mode power supply
  • Power supplies are a necessary electronic device in most electronic products, and are used for converting battery or grid power to power required by the electronic product and having specific characteristics. In most power supplies, switching-mode power supplies have superior electrical energy conversion efficiency and smaller product dimensions, making them popular in the power supply market.
  • PSC primary side control
  • SSC secondary side control
  • SSC directly couples a detection circuit to an output node of a secondary winding of a power supply, then through a photo coupler, transmits a detection result to a power supply controller located on the primary side to control energy of the power supply that is to be stored and converted on the primary winding.
  • PSC indirectly detects voltage outputted by the secondary winding through directly detecting reflected voltage on an auxiliary winding, and indirectly completes detection of output voltage on an output node of the power supply.
  • PSC completes detection and energy conversion control on the primary side.
  • PSC is able to lower cost, as PSC does not require the photo coupler having both greater size and cost.
  • PSC may also have higher conversion efficiency, because PSC does not require the detection circuit on the secondary side that constantly drains energy.
  • FIG. 1 is a diagram of a switching-mode power supply that uses PSC.
  • Bridge rectifier 20 rectifies alternating current from grid node AC to establish direct current input power at input node IN.
  • Voltage V IN of output power may have an M-shaped waveform, but may also be filtered into a fixed level that roughly does not vary over time.
  • Transformer has three windings: primary winding PRM, secondary winding SEC, and auxiliary winding AUX.
  • Power supply controller 26 periodically controls power switch 34 through gate node GATE. When power switch 34 is ON, primary winding PRM performs energy storage. When power switch 34 is OFF, secondary winding SEC and auxiliary winding AUX discharge to establish output voltage VOUT on output node OUT for supply to load 24 , and control voltage VCC for supply to power supply controller 26 .
  • Voltage divider resistors 28 , 30 detect voltage V AUX of auxiliary winding AUX to provide feedback voltage V FB to feedback node FB of power supply controller 26 . According to feedback voltage V FB , power supply controller 26 establishes compensation voltage V COM on compensation capacitor 32 , and controls power switch 34 according thereto.
  • FIG. 2 shows the power supply controller 26 of FIG. 1 and some external components.
  • Power supply controller 26 comprises sampler 12 , pulse generator 14 , transconductor 15 , and pulse width controller 16 .
  • pulse generator 14 provides a short pulse to sampler 12 , so that sampler 12 samples feedback voltage V FB to generate feedback voltage V IFB at intermediate node IFB.
  • feedback voltage V IFB equivalently represents voltage level of secondary winding voltage V SEC of secondary winding SEC during discharging, and roughly represents output voltage V OUT .
  • Transconductor 15 controls compensation voltage V COM on compensation node COMP according to a comparison result of feedback voltage V IFB and target voltage V REF .
  • Pulse width controller 16 controls power switch 34 according to compensation voltage V COM .
  • power supply controller 26 provides a feedback mechanism that roughly stabilizes feedback voltage V IFB to target voltage V REF , and is thus able to stabilize output voltage V OUT .
  • a primary-side control method comprises providing a feedback voltage, the feedback voltage representing a secondary-side voltage of a secondary winding through an inductance-coupling effect; controlling a power switch by a first switching frequency; comparing the feedback voltage and an over-shot reference voltage; and controlling the power switch by a second switching frequency when the feedback voltage is greater than the over-shot reference voltage.
  • the second switching frequency is lower than the first switching frequency.
  • a power supply controller for performing primary-side control comprises a comparator and an ON triggering controller.
  • the comparator is for comparing a feedback voltage and an over-shot reference voltage.
  • the feedback voltage represents a secondary-side voltage of a secondary winding through an inductance-coupling effect.
  • the ON-triggering controller is coupled to the comparator. When the feedback voltage is lower than the over-shot reference voltage, the ON-triggering controller causes a power switch to operate at approximately a first switching frequency. When the feedback voltage is higher than the over-shot reference voltage, the ON-triggering controller causes the power switch to operate at approximately a second switching frequency. The second switching frequency is lower than the first switching frequency.
  • a power management system comprises a transformer, a power switch, and a power supply controller.
  • the transformer has a primary winding, an auxiliary winding, and a secondary winding.
  • the power switch is coupled to the primary winding for controlling an inductance current flowing through the primary winding.
  • the power supply controller is for controlling the power switch, and comprises a feedback node, a comparator, and an ON-triggering controller.
  • the feedback node is coupled to the auxiliary winding.
  • the comparator is for comparing a feedback voltage and an over-shot reference voltage.
  • the feedback voltage represents a secondary-side voltage of the secondary winding through the feedback node and the auxiliary winding.
  • the ON-triggering controller is coupled to the comparator.
  • the ON-triggering controller causes the power switch to operate approximately at a first switching frequency when the feedback voltage is lower than the over-shot reference voltage, and the ON-triggering controller causes the power switch to operate approximately at a second switching frequency when the feedback voltage is higher than the over-shot reference voltage.
  • the second switching frequency is lower than the first switching frequency.
  • FIG. 1 is a diagram of a switching-mode power supply that uses PSC.
  • FIG. 2 shows the power supply controller of FIG. 1 and some external components.
  • FIG. 3 is a diagram of a power supply controller according to an embodiment.
  • FIG. 4 is a diagram of a power supply controller according to an embodiment.
  • the power supply controller 26 of FIG. 2 may exhibit excessive output voltage VOUT jitter during light-heavy load switching.
  • FIG. 3 is a diagram of a power supply controller 26 a according to an embodiment. Power supply controller 26 a replaces power supply controller 26 of FIG. 1 .
  • Power supply controller 26 a comprises sampler 12 , pulse generator 14 , transconductor 15 , comparator 60 , oscillator 62 , and pulse width controller 64 .
  • pulse width controller 64 turns power switch 34 off, secondary winding SEC and auxiliary winding AUX begin to release energy stored previously by primary winding PRM while power switch 34 was turned on.
  • the time for secondary winding SEC and auxiliary winding AUX to release electrical energy is called discharge time T DIS .
  • pulse generator 14 provides a short pulse to cause sampler 12 to sample feedback voltage V FB on feedback node FB.
  • a sample result is then stored on intermediate node IFB as feedback voltage V IFB .
  • feedback voltage V IFB approximately represents output voltage V OUT through voltage division and inductive coupling through feedback node FB, voltage divider resistors 28 and 30 , auxiliary winding AUX, and secondary winding SEC.
  • Transconductor 15 controls compensation voltage V COM according to feedback voltage V IFB and target voltage V REF .
  • pulse width controller 64 determines ON time T ON of power switch 34 per one switching period according to compensation voltage V COM on compensation node COMP, which is time in which power switch 34 is short circuited.
  • Oscillator 62 provides set signal S SET through set node SET, which periodically triggers turning on of power switch 34 .
  • switching frequency of power switch 34 is approximately equal to frequency of set signal S SET .
  • frequency of set signal S SET can be determined from compensation voltage V COM .
  • frequency of set signal S SET can decrease with decreasing compensation voltage V COM .
  • Comparator 60 compares feedback voltage V IFB and over-shot reference voltage V OS-REF .
  • Comparison result S OV of comparator 60 affects frequency of set signal S SET provided by oscillator 62 .
  • comparison result S OV is logic 0, and frequency of set signal S SET may be determined solely by compensation voltage V COM to be, for example, 60 KHz.
  • compensation voltage V COM is, for example, 60 KHz.
  • Power supply controller 26 a of FIG. 3 can suppress output voltage V OUT jitter when transitioning from a heavy load to a light load.
  • the following description is made with reference to FIG. 1 , with power supply controller 26 a replacing power supply controller 26 thereof, and target voltage V REF and over-shot reference voltage V OS-REF assumed to be 2.5V and 2.6V, respectively.
  • target voltage V REF and over-shot reference voltage V OS-REF assumed to be 2.5V and 2.6V, respectively.
  • Feedback voltage V IFB is periodically updated as set signal S SET periodically turns on power switch 34 , so as to track current output voltage V OUT .
  • power supply controller 26 a will return to normal operation, e.g. frequency of set signal S SET being determined only on by compensation voltage V COM . So, for normal operation, power supply controller 26 a and power supply controller 26 are the same, each causing feedback voltage V IFB to converge to target voltage V REF of 2.5V.
  • FIG. 4 is a diagram of a power supply controller 26 b according to an embodiment.
  • power supply controller 26 b replaces power supply controller 26 of FIG. 1 as another embodiment.
  • power supply controller 26 b has OFF time controller 66 coupled to feedback node FB.
  • OFF time controller 66 may employ valley switching. For example, after discharge time T DIS , auxiliary winding voltage V AUX of auxiliary winding AUX starts oscillating, and gradually converges to 0V. So-called “valley switching” may mean that, after power switch 34 is turned off, power switch 34 is turned on when a 1 st valley, a 2 nd valley, a 3 rd valley, and so on of auxiliary winding voltage V AUX occurs. This type of operating scheme is typically called quasi-resonance (QR) mode.
  • QR quasi-resonance
  • OFF time controller 66 can determine when auxiliary winding voltage V AUX drops across 0V, so-called zero crossing. OFF time controller 66 may be designed to trigger pulse width controller 64 to turn on power switch 34 through set node SET a predetermined period after auxiliary winding voltage V AUX drops across 0V. Thus, valley switching can be approximately realized. In order to avoid zero-crossing never being detected, OFF time controller 66 can be designed to forcefully trigger pulse width controller 64 to turn on power switch 34 if no zero-crossing has been detected after a maximum OFF time.
  • timing of set signal S SET triggering turning on of power switch 34 may be determined according to compensation voltage V COM and zero-crossing detected by OFF time controller 66 through feedback node FB.
  • power supply controller 26 b approximately operates in QR mode, and may trigger turning on of power switch 34 at any valley appearing in auxiliary winding voltage V AUX .
  • comparison result S OV is logic 1
  • OFF time controller 66 only triggers pulse width controller 64 to turn on power switch 34 after maximum OFF time. At this time, switching frequency of power switch 34 is necessarily lower than when operating in QR mode.
  • power supply controller 26 b of FIG. 4 causes OFF time of power switch 34 to be maximum OFF time, so that switching frequency immediately drops. Electrical power transmitted by the transformer can be lowered rapidly, which can rapidly prevent output voltage V OUT from rising further.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

Power controllers and related primary-side control methods are disclosed. A disclosed power controller has a comparator and an ON-triggering controller. The comparator compares a feedback voltage with an over-shot reference voltage. Based on an inductance-coupling effect, the feedback voltage represents a secondary-side voltage of a secondary winding. Coupled to the comparator, the ON-triggering controller operates a power switch at about a first switching frequency when the feedback voltage is lower than the over-shot reference voltage. The ON-triggering controller operates the power switch at about a second switching frequency when the feedback voltage exceeds the over-shot reference voltage. The second switching frequency is less than the first switching frequency.

Description

    CROSS REFERENCE TO RELATED APPLICATIONS
  • This is a continuation application of U.S. patent application Ser. No. 13/650,098, filed on Oct. 11, 2012, and all benefits of such earlier application are hereby claimed for this new continuation application.
    • BACKGROUND OF THE INVENTION
  • 1. Field of the Invention
  • The present invention relates to a primary side control (PSC) switching-mode power supply (SMPS), and particularly to a PSC SMPS that has reduced output voltage jitter.
  • 2. Description of the Prior Art
  • Power supplies are a necessary electronic device in most electronic products, and are used for converting battery or grid power to power required by the electronic product and having specific characteristics. In most power supplies, switching-mode power supplies have superior electrical energy conversion efficiency and smaller product dimensions, making them popular in the power supply market.
  • Two different control schemes are used in current switching-mode power supplies: primary side control (PSC) and secondary side control (SSC). SSC directly couples a detection circuit to an output node of a secondary winding of a power supply, then through a photo coupler, transmits a detection result to a power supply controller located on the primary side to control energy of the power supply that is to be stored and converted on the primary winding. Compared to SSC, PSC indirectly detects voltage outputted by the secondary winding through directly detecting reflected voltage on an auxiliary winding, and indirectly completes detection of output voltage on an output node of the power supply. PSC completes detection and energy conversion control on the primary side. Compared to SSC, PSC is able to lower cost, as PSC does not require the photo coupler having both greater size and cost. PSC may also have higher conversion efficiency, because PSC does not require the detection circuit on the secondary side that constantly drains energy.
  • FIG. 1 is a diagram of a switching-mode power supply that uses PSC. Bridge rectifier 20 rectifies alternating current from grid node AC to establish direct current input power at input node IN. Voltage VIN of output power may have an M-shaped waveform, but may also be filtered into a fixed level that roughly does not vary over time. Transformer has three windings: primary winding PRM, secondary winding SEC, and auxiliary winding AUX. Power supply controller 26 periodically controls power switch 34 through gate node GATE. When power switch 34 is ON, primary winding PRM performs energy storage. When power switch 34 is OFF, secondary winding SEC and auxiliary winding AUX discharge to establish output voltage VOUT on output node OUT for supply to load 24, and control voltage VCC for supply to power supply controller 26.
  • Voltage divider resistors 28, 30 detect voltage VAUX of auxiliary winding AUX to provide feedback voltage VFB to feedback node FB of power supply controller 26. According to feedback voltage VFB, power supply controller 26 establishes compensation voltage VCOM on compensation capacitor 32, and controls power switch 34 according thereto.
  • FIG. 2 shows the power supply controller 26 of FIG. 1 and some external components. Power supply controller 26 comprises sampler 12, pulse generator 14, transconductor 15, and pulse width controller 16. During discharging of secondary winding SEC and auxiliary winding AUX, pulse generator 14 provides a short pulse to sampler 12, so that sampler 12 samples feedback voltage VFB to generate feedback voltage VIFB at intermediate node IFB. Through feedback node FB, voltage divider resistors 28 and 30, and auxiliary winding AUX, feedback voltage VIFB equivalently represents voltage level of secondary winding voltage VSEC of secondary winding SEC during discharging, and roughly represents output voltage VOUT. Transconductor 15 controls compensation voltage VCOM on compensation node COMP according to a comparison result of feedback voltage VIFB and target voltage VREF. Pulse width controller 16 controls power switch 34 according to compensation voltage VCOM. Overall, power supply controller 26 provides a feedback mechanism that roughly stabilizes feedback voltage VIFB to target voltage VREF, and is thus able to stabilize output voltage VOUT.
    • SUMMARY OF THE INVENTION
  • According to an embodiment, a primary-side control method comprises providing a feedback voltage, the feedback voltage representing a secondary-side voltage of a secondary winding through an inductance-coupling effect; controlling a power switch by a first switching frequency; comparing the feedback voltage and an over-shot reference voltage; and controlling the power switch by a second switching frequency when the feedback voltage is greater than the over-shot reference voltage. The second switching frequency is lower than the first switching frequency.
  • According to an embodiment, a power supply controller for performing primary-side control comprises a comparator and an ON triggering controller. The comparator is for comparing a feedback voltage and an over-shot reference voltage. The feedback voltage represents a secondary-side voltage of a secondary winding through an inductance-coupling effect. The ON-triggering controller is coupled to the comparator. When the feedback voltage is lower than the over-shot reference voltage, the ON-triggering controller causes a power switch to operate at approximately a first switching frequency. When the feedback voltage is higher than the over-shot reference voltage, the ON-triggering controller causes the power switch to operate at approximately a second switching frequency. The second switching frequency is lower than the first switching frequency.
  • According to an embodiment, a power management system comprises a transformer, a power switch, and a power supply controller. The transformer has a primary winding, an auxiliary winding, and a secondary winding. The power switch is coupled to the primary winding for controlling an inductance current flowing through the primary winding. The power supply controller is for controlling the power switch, and comprises a feedback node, a comparator, and an ON-triggering controller. The feedback node is coupled to the auxiliary winding. The comparator is for comparing a feedback voltage and an over-shot reference voltage. The feedback voltage represents a secondary-side voltage of the secondary winding through the feedback node and the auxiliary winding. The ON-triggering controller is coupled to the comparator. The ON-triggering controller causes the power switch to operate approximately at a first switching frequency when the feedback voltage is lower than the over-shot reference voltage, and the ON-triggering controller causes the power switch to operate approximately at a second switching frequency when the feedback voltage is higher than the over-shot reference voltage. The second switching frequency is lower than the first switching frequency.
  • These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG. 1 is a diagram of a switching-mode power supply that uses PSC.
  • FIG. 2 shows the power supply controller of FIG. 1 and some external components.
  • FIG. 3 is a diagram of a power supply controller according to an embodiment.
  • FIG. 4 is a diagram of a power supply controller according to an embodiment.
    •  DETAILED DESCRIPTION
  • In the following examples, components sharing the same reference numerals have similar or the same function, structure, and operation. Persons of ordinary skill in the art may arrive at simple alterations or modifications of the embodiments of the detailed description according to the teachings and disclosure herein without leaving the spirit of the present invention.
  • The power supply controller 26 of FIG. 2 may exhibit excessive output voltage VOUT jitter during light-heavy load switching.
  • For example, when load 24 suddenly transitions from a heavy load to a light load or no load, output voltage VOUT will suddenly rise. And, power supply controller 26 must wait for a period of time, in which transconductor 15 pulls compensation voltage VCOM down to a certain level, such that energy converted by transformer is lower than energy consumed by load 24, before output voltage VOUT can begin to fall. However, at this time, output voltage VOUT is very likely to already have exceeded the required specification of the power supply management system.
  • FIG. 3 is a diagram of a power supply controller 26 a according to an embodiment. Power supply controller 26 a replaces power supply controller 26 of FIG. 1.
  • Power supply controller 26 a comprises sampler 12, pulse generator 14, transconductor 15, comparator 60, oscillator 62, and pulse width controller 64.
  • After pulse width controller 64 turns power switch 34 off, secondary winding SEC and auxiliary winding AUX begin to release energy stored previously by primary winding PRM while power switch 34 was turned on. The time for secondary winding SEC and auxiliary winding AUX to release electrical energy is called discharge time TDIS. During discharge time TDIS, pulse generator 14 provides a short pulse to cause sampler 12 to sample feedback voltage VFB on feedback node FB. A sample result is then stored on intermediate node IFB as feedback voltage VIFB. Thus, feedback voltage VIFB approximately represents output voltage VOUT through voltage division and inductive coupling through feedback node FB, voltage divider resistors 28 and 30, auxiliary winding AUX, and secondary winding SEC.
  • Transconductor 15 controls compensation voltage VCOM according to feedback voltage VIFB and target voltage VREF. In some embodiments, pulse width controller 64 determines ON time TON of power switch 34 per one switching period according to compensation voltage VCOM on compensation node COMP, which is time in which power switch 34 is short circuited.
  • Oscillator 62 provides set signal SSET through set node SET, which periodically triggers turning on of power switch 34. Thus, switching frequency of power switch 34 is approximately equal to frequency of set signal SSET. In some embodiments, frequency of set signal SSET can be determined from compensation voltage VCOM. For example, frequency of set signal SSET can decrease with decreasing compensation voltage VCOM.
  • Comparator 60 compares feedback voltage VIFB and over-shot reference voltage VOS-REF. Comparison result SOV of comparator 60 affects frequency of set signal SSET provided by oscillator 62. For example, when feedback voltage VIFB is lower than over-shot reference voltage VOS-REF, comparison result SOV is logic 0, and frequency of set signal SSET may be determined solely by compensation voltage VCOM to be, for example, 60 KHz. As soon as feedback voltage VIFB exceeds over-shot reference voltage VOS-REF/comparison result SOV becomes logic 1, and frequency of set signal SSET immediately drops to be fixed at, for example, 25 KHz.
  • Power supply controller 26 a of FIG. 3 can suppress output voltage VOUT jitter when transitioning from a heavy load to a light load. The following description is made with reference to FIG. 1, with power supply controller 26 a replacing power supply controller 26 thereof, and target voltage VREF and over-shot reference voltage VOS-REF assumed to be 2.5V and 2.6V, respectively. As soon as load 24 suddenly transitions from heavy loading to light loading or no loading, because energy output of the transformer exceeds energy consumption of load 24, output voltage VOUT suddenly rises, causing feedback voltage VIFB to start rising in turn. As soon as feedback voltage VIFB exceeds over-shot reference voltage VOS-REF of 2.6V, frequency of set signal SSET immediately drops to a low value, so that electrical power outputted by transformer immediately drops. Compared to the prior art, which must wait for compensation voltage VCOM to be pulled down to a certain level before transmitted energy can drop noticeably, as soon as power supply controller 26 a discovers that feedback voltage VIFB has exceeded over-shot reference voltage VOS-REF of 2.6V, frequency of set signal SSET is dropped immediately, which also lowers electrical power output of the transformer, thus rapidly prohibiting output voltage VOUT from increasing.
  • Feedback voltage VIFB is periodically updated as set signal SSET periodically turns on power switch 34, so as to track current output voltage VOUT. As long as feedback voltage VIFB is lower than over-shot reference voltage VOS-REF of 2.6V, power supply controller 26 a will return to normal operation, e.g. frequency of set signal SSET being determined only on by compensation voltage VCOM. So, for normal operation, power supply controller 26 a and power supply controller 26 are the same, each causing feedback voltage VIFB to converge to target voltage VREF of 2.5V.
  • FIG. 4 is a diagram of a power supply controller 26 b according to an embodiment. In the following description, power supply controller 26 b replaces power supply controller 26 of FIG. 1 as another embodiment.
  • Compared to the power supply controller 26 a of FIG. 2, power supply controller 26 b has OFF time controller 66 coupled to feedback node FB. OFF time controller 66 may employ valley switching. For example, after discharge time TDIS, auxiliary winding voltage VAUX of auxiliary winding AUX starts oscillating, and gradually converges to 0V. So-called “valley switching” may mean that, after power switch 34 is turned off, power switch 34 is turned on when a 1st valley, a 2nd valley, a 3rd valley, and so on of auxiliary winding voltage VAUX occurs. This type of operating scheme is typically called quasi-resonance (QR) mode.
  • Through feedback node FB, OFF time controller 66 can determine when auxiliary winding voltage VAUX drops across 0V, so-called zero crossing. OFF time controller 66 may be designed to trigger pulse width controller 64 to turn on power switch 34 through set node SET a predetermined period after auxiliary winding voltage VAUX drops across 0V. Thus, valley switching can be approximately realized. In order to avoid zero-crossing never being detected, OFF time controller 66 can be designed to forcefully trigger pulse width controller 64 to turn on power switch 34 if no zero-crossing has been detected after a maximum OFF time.
  • In the embodiment of FIG. 4, when feedback voltage VIFB is lower than over-shot reference voltage VOS-REF, comparison result SOV is logic 0. At this time, timing of set signal SSET triggering turning on of power switch 34 may be determined according to compensation voltage VCOM and zero-crossing detected by OFF time controller 66 through feedback node FB. Simply speaking, when feedback voltage VIFB is lower than over-shot reference voltage VOS-REF, power supply controller 26 b approximately operates in QR mode, and may trigger turning on of power switch 34 at any valley appearing in auxiliary winding voltage VAUX.
  • When feedback voltage VIFB is greater than over-shot reference voltage VOS-REF, comparison result SOV is logic 1, and OFF time controller 66 only triggers pulse width controller 64 to turn on power switch 34 after maximum OFF time. At this time, switching frequency of power switch 34 is necessarily lower than when operating in QR mode.
  • Similar to power supply controller 26 a of FIG. 3, when output voltage VOUT is on the high side, causing feedback voltage VIFB to exceed over-shot reference voltage VOS-REF, power supply controller 26 b of FIG. 4 causes OFF time of power switch 34 to be maximum OFF time, so that switching frequency immediately drops. Electrical power transmitted by the transformer can be lowered rapidly, which can rapidly prevent output voltage VOUT from rising further.
  • It is predictable that the power supply controllers of FIG. 3 and FIG. 4 can both rapidly prevent feedback voltage VIFB from rising further, which can reduce output voltage VOUT jitter, and cause output voltage VOUT to converge more rapidly.
  • Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims (9)

What is claimed is:
1. A primary-side control method comprising:
providing a feedback node, coupled to an auxiliary winding;
generating a feedback voltage by sampling the feedback node during discharging of the secondary winding;
controlling a power switch in a first switching frequency;
comparing the feedback voltage and an over-shot reference voltage; and
controlling the power switch in a second switching frequency when the feedback voltage is greater than the over-shot reference voltage;
wherein the second switching frequency is lower than the first switching frequency, and the feedback voltage represents a secondary-side voltage of the secondary winding through an inductance-coupling effect.
2. The primary-side control method of claim 1, further comprising:
turning on the power switch if an auxiliary winding voltage of the auxiliary winding is approximately within a voltage valley, when the feedback voltage is lower than the over-shot reference voltage; and
turning on the power switch after the power switch turned off for a maximum OFF time, when the feedback voltage is higher than the over-shot reference voltage.
3. The primary-side control method of claim 1, further comprising:
comparing the feedback voltage and a target voltage and a target voltage to control a compensation voltage; and
controlling ON time of the power switch according to the compensation voltage.
4. The primary-side control method of claim 1, further comprising:
determining the first switching frequency according to the compensation voltage.
5. A power supply controller for performing primary-side control, comprising:
a comparator for comparing a feedback voltage and an over-shot reference voltage, wherein the feedback voltage represents a secondary-side voltage of a secondary winding through an inductance-coupling effect;
a sampler coupled between the comparator and a feedback node coupled to an auxiliary winding, the sampler sampling the feedback node to generate the feedback voltage; and
an ON-triggering controller coupled to the comparator, wherein when the feedback voltage is lower than the over-shot reference voltage, the ON-triggering controller causes a power switch to operate at approximately a first switching frequency, and when the feedback voltage is higher than the over-shot reference voltage, the ON-triggering controller causes the power switch to operate at approximately a second switching frequency;
wherein the second switching frequency is lower than the first switching frequency.
6. The power supply controller of claim 5, further comprising:
a pulse generator for providing a pulse during discharging of the secondary winding for causing the sampler to sample the feedback node.
7. The power supply controller of claim 6, further comprising:
a transconductor for comparing the feedback voltage and a target voltage to control a compensation voltage.
8. The power supply controller of claim 7, wherein the ON-triggering controller is an oscillator for providing a periodic signal to trigger turning on of the power switch, and the compensation voltage determines a switching frequency of the periodic signal.
9. The power supply controller of claim 6, wherein:
the ON-triggering controller is an OFF time controller coupled to a feedback node;
the OFF time controller triggers turning on of the power switch if an auxiliary winding voltage of the auxiliary winding is approximately in a voltage valley, when the feedback voltage is lower than the over-shot reference voltage; and
the OFF time controller triggers turning on of the power switch after the power switch turned off for a maximum OFF time, when the feedback voltage is larger than the over-shot reference voltage.
US14/960,452 2011-10-12 2015-12-07 Methods and power controllers for primary side control Abandoned US20160087534A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US14/960,452 US20160087534A1 (en) 2011-10-12 2015-12-07 Methods and power controllers for primary side control

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
TW100136874A TWI445291B (en) 2011-10-12 2011-10-12 Methods and power controllers for primary side control
TW100136874 2011-10-12
US13/650,098 US9236793B2 (en) 2011-10-12 2012-10-11 Methods and power controllers for primary side control
US14/960,452 US20160087534A1 (en) 2011-10-12 2015-12-07 Methods and power controllers for primary side control

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US13/650,098 Continuation US9236793B2 (en) 2011-10-12 2012-10-11 Methods and power controllers for primary side control

Publications (1)

Publication Number Publication Date
US20160087534A1 true US20160087534A1 (en) 2016-03-24

Family

ID=48085868

Family Applications (2)

Application Number Title Priority Date Filing Date
US13/650,098 Active 2033-03-25 US9236793B2 (en) 2011-10-12 2012-10-11 Methods and power controllers for primary side control
US14/960,452 Abandoned US20160087534A1 (en) 2011-10-12 2015-12-07 Methods and power controllers for primary side control

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US13/650,098 Active 2033-03-25 US9236793B2 (en) 2011-10-12 2012-10-11 Methods and power controllers for primary side control

Country Status (2)

Country Link
US (2) US9236793B2 (en)
TW (1) TWI445291B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110121043A (en) * 2019-06-10 2019-08-13 北海惠科光电技术有限公司 Show power supply unit and display system

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI460975B (en) * 2011-09-07 2014-11-11 Leadtrend Tech Corp Power controllers with load compensation and related control methods
US9515545B2 (en) * 2014-02-14 2016-12-06 Infineon Technologies Austria Ag Power conversion with external parameter detection
TWI555314B (en) * 2015-01-22 2016-10-21 通嘉科技股份有限公司 Frequency controller of a power converter and related frequency control method
US10218279B2 (en) * 2016-10-26 2019-02-26 Texas Instruments Incorporated Methods and circuitry for operating switching power supplies based on switching frequency comparison
TWI692191B (en) * 2019-02-21 2020-04-21 通嘉科技股份有限公司 Power controller and control method thereof
CN111628646B (en) * 2019-02-28 2021-07-20 通嘉科技股份有限公司 Power supply controller and related control method

Family Cites Families (45)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5173847A (en) * 1988-09-30 1992-12-22 Canon Kabushiki Kaisha PWM power supply with synchronous rectifier and synchronizing oscillator
DE4209053A1 (en) * 1992-03-20 1993-09-23 Telefunken Microelectron SWITCHING CONTROL SYSTEM
EP0689731A1 (en) * 1993-03-17 1996-01-03 National Semiconductor Corporation Frequency shift circuit for switching regulator
US5903452A (en) * 1997-08-11 1999-05-11 System General Corporation Adaptive slope compensator for current mode power converters
US7034800B2 (en) * 2001-11-14 2006-04-25 Matsushita Electric Industrial Co., Ltd. Driving circuit and driving method for piezoelectric transformer, backlight apparatus, liquid crystal display apparatus, liquid crystal monitor, and liquid crystal TV
US6611439B1 (en) * 2002-10-28 2003-08-26 System General Corporation PWM controller for controlling output power limit of a power supply
US6836415B1 (en) * 2003-06-18 2004-12-28 Systems General Corp. Primary-side regulated pulse width modulation controller with improved load regulation
US6853563B1 (en) * 2003-07-28 2005-02-08 System General Corp. Primary-side controlled flyback power converter
US7054170B2 (en) * 2004-01-05 2006-05-30 System General Corp. Power-mode controlled power converter
AU2005222987B9 (en) * 2004-03-15 2009-10-22 Signify North America Corporation Power control methods and apparatus
US7088598B2 (en) * 2004-04-02 2006-08-08 System General Corp. Power-mode control circuitry for power converters
US6977824B1 (en) * 2004-08-09 2005-12-20 System General Corp. Control circuit for controlling output current at the primary side of a power converter
US7016204B2 (en) * 2004-08-12 2006-03-21 System General Corp. Close-loop PWM controller for primary-side controlled power converters
US7061780B2 (en) * 2004-09-09 2006-06-13 System General Corp. Switching control circuit with variable switching frequency for primary-side-controlled power converters
US7362592B2 (en) * 2004-09-16 2008-04-22 System General Corp. Switching control circuit for primary-side controlled power converters
US7362593B2 (en) * 2004-09-16 2008-04-22 System General Corp. Switching control circuit having off-time modulation to improve efficiency of primary-side controlled power supply
US7259972B2 (en) * 2004-10-07 2007-08-21 System General Corporation Primary-side-control power converter having a switching controller using frequency hopping and voltage and current control loops
US7593245B2 (en) * 2005-07-08 2009-09-22 Power Integrations, Inc. Method and apparatus to limit maximum switch current in a switching power supply
US7505287B1 (en) * 2005-11-10 2009-03-17 Iwatt Inc. On-time control for constant current mode in a flyback power supply
US7635956B2 (en) * 2006-01-06 2009-12-22 Active-Semi, Inc. Primary side constant output voltage controller
US7602160B2 (en) * 2006-07-31 2009-10-13 System General Corp. Method and apparatus providing protection for power converter
CN101127495B (en) * 2006-08-16 2010-04-21 昂宝电子（上海）有限公司 System and method for switch power supply control
US20080062725A1 (en) * 2006-09-11 2008-03-13 Ta-Yung Yang Multi-channels power converter having power saving means to improve light load efficiency
US7443700B2 (en) * 2006-11-09 2008-10-28 Iwatt Inc. On-time control for constant current mode in a flyback power supply
US8179700B2 (en) * 2006-11-29 2012-05-15 Systems General Corp. Control circuit with adaptive minimum on time for power converters
US7656685B2 (en) * 2007-01-12 2010-02-02 System General Corp. Control method and circuit with indirect input voltage detection by switching current slope detection
US7616461B2 (en) * 2007-01-12 2009-11-10 System General Corp. Control method and circuit with indirect input voltage detection by switching current slope detection
US7911808B2 (en) * 2007-02-10 2011-03-22 Active-Semi, Inc. Primary side constant output current controller with highly improved accuracy
JP2008206239A (en) * 2007-02-17 2008-09-04 Seiko Instruments Inc Semiconductor device
US7710095B2 (en) * 2007-05-22 2010-05-04 System General Corporation Power converter having PWM controller for maximum output power compensation
ITTO20070862A1 (en) * 2007-11-29 2009-05-30 St Microelectronics Srl VOLTAGE ISOLATED CONVERTER WITH FEEDBACK TO THE PRIMARY AND PASSIVE SNUBBER NETWORK, AND RELATIVE CONTROL METHOD
JP5230181B2 (en) * 2007-12-07 2013-07-10 パナソニック株式会社 Energy transfer device and semiconductor device for energy transfer control
US7906943B2 (en) * 2007-12-20 2011-03-15 Microsemi Corporation Boost converter with adaptive coil peak current
CN101515756B (en) * 2008-02-18 2011-11-23 昂宝电子（上海）有限公司 Multimode method and system for high-efficiency power control
US20110116287A1 (en) * 2008-08-05 2011-05-19 System General Corp. Switching controller having switching frequency hopping for power converter
US8253400B2 (en) * 2008-08-07 2012-08-28 Microsemi Corporation Current sensing for high voltage buck converter
US8488342B2 (en) * 2008-10-21 2013-07-16 On-Bright Electronics (Shanghai) Co., Ltd. Systems and methods for constant voltage mode and constant current mode in flyback power converters with primary-side sensing and regulation
US8526203B2 (en) * 2008-10-21 2013-09-03 On-Bright Electronics (Shanghai) Co., Ltd. Systems and methods for constant voltage mode and constant current mode in flyback power converter with primary-side sensing and regulation
KR20100136305A (en) * 2009-06-18 2010-12-28 페어차일드코리아반도체 주식회사 Frequency modulation controller, switch mode power supply comprising the same and switching operation frequency modulation method
TWI431918B (en) * 2009-06-19 2014-03-21 Leadtrend Tech Corp Control method, constant current control method, method for generating a real current source to represent average current through a winding, constant current and constant voltage power converter, switch controller, and average voltage detector
TWI403061B (en) * 2009-06-22 2013-07-21 Richpower Microelectronics Apparatus and method for protection of current sense resistor short circuit in isolated type power supply
US8629630B2 (en) * 2010-05-25 2014-01-14 Green Solution Technology Co., Ltd. LED driving circuit and control circuit
US8994351B2 (en) * 2011-08-02 2015-03-31 Power Integrations, Inc. Smooth mode transition plateau for a power supply controller
CN102916586B (en) * 2011-08-04 2014-04-02 昂宝电子（上海）有限公司 System and method for switching on and off power converter
US8717785B2 (en) * 2011-09-30 2014-05-06 Power Integrations, Inc. Multi-stage sampling circuit for a power converter controller

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110121043A (en) * 2019-06-10 2019-08-13 北海惠科光电技术有限公司 Show power supply unit and display system

Also Published As

Publication number Publication date
US9236793B2 (en) 2016-01-12
TWI445291B (en) 2014-07-11
US20130094254A1 (en) 2013-04-18
TW201316657A (en) 2013-04-16

Similar Documents

Publication Publication Date Title
US9954450B2 (en) Control circuit, control method and primary-controlled flyback converter using the same
US20160087534A1 (en) Methods and power controllers for primary side control
US20230336089A1 (en) Flyback converter with secondary side regulation
US8994351B2 (en) Smooth mode transition plateau for a power supply controller
US9093909B2 (en) Switching mode power supply and the method thereof
US11303195B2 (en) Partial zero voltage switching (ZVS) for flyback power converter and method therefor
JP4735072B2 (en) Switching power supply
US8665613B2 (en) Switched mode power converter and method of operation thereof
US8717785B2 (en) Multi-stage sampling circuit for a power converter controller
US10784789B1 (en) Switched mode power supply with multi-mode operation and method therefor
US9136769B2 (en) Load change detection for switched mode power supply with low no load power
US9184667B2 (en) Switching power converter with primary-side dynamic load detection and primary-side feedback and control
US20130235621A1 (en) Regulation for power supply mode transition to low-load operation
TWI584568B (en) Converter and control method thereof
JP2010063327A (en) Switching power supply unit
CN111327196B (en) Synchronizing multiple controllers in a power converter
TWI672894B (en) Power controllers and control methods thereof
JP5857702B2 (en) Switching power supply
TWI497894B (en) Power controller and relevant control method for operating a power supply to switch at a bottom of a voltage valley
CN103066868A (en) Primary side control method and power controller
US20200186044A1 (en) Power supply apparatus and image forming apparatus
US11424684B2 (en) High performance two stage power converter with enhanced light load management
TW202135453A (en) Partial zero voltage switching (zvs) for flyback power converter and method therefor
TWI407668B (en) Power supply and method for suppressing voltage ripple on output voltage source of a power supply
JP4415052B2 (en) Switching power supply

Legal Events

Date Code Title Description
AS Assignment

Owner name: LEADTREND TECHNOLOGY CORP., TAIWAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HUANG, YU-YUN;SHEN, YI-LUN;REEL/FRAME:037219/0662

Effective date: 20121009

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION