CN115184666A - Slope detection circuit with programmable blanking function and switching power supply system - Google Patents
Slope detection circuit with programmable blanking function and switching power supply system Download PDFInfo
- Publication number
- CN115184666A CN115184666A CN202210876290.0A CN202210876290A CN115184666A CN 115184666 A CN115184666 A CN 115184666A CN 202210876290 A CN202210876290 A CN 202210876290A CN 115184666 A CN115184666 A CN 115184666A
- Authority
- CN
- China
- Prior art keywords
- circuit
- resistor
- voltage
- slope
- programmable
- 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.)
- Pending
Links
Images
Classifications
-
- 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
- G01R19/12—Measuring rate of change
-
- 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
- G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
- G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
- G01R19/16552—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies in I.C. power supplies
-
- 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
- H02M3/33569—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 having several active switching elements
- H02M3/33576—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 having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33592—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 having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention provides a slope detection circuit with programmable blanking function and a switch power supply system, comprising: a ramp generator generating an initial blanking ramp signal; the programmable module and the amplitude modulation circuit are respectively connected with a ramp generator and are used for respectively adjusting the blanking ramp falling time and amplitude of the blanking ramp signal to form a required ramp direct-current voltage signal; the capacitive coupling differential circuit is used for sampling the change slope of the SENSE terminal voltage and outputting a sampling voltage positively correlated with the change slope of the SENSE terminal voltage; and the comparison circuit receives the superposed voltage of the sampling voltage and the ramp direct-current voltage signal, and compares the superposed voltage with a first threshold voltage and a second threshold voltage which are set inside respectively so as to judge whether the change slope of the SENSE terminal voltage reaches expectation or not and finish slope detection. The circuit structure of the invention is simple, and can realize slope detection and resonance valley bottom detection functions and realize the anti-false-turn-on function applied to the synchronous rectification control DCM mode.
Description
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a slope detection circuit with a programmable blanking function and a switching power supply system.
Background
Various slope detection circuits are commonly used in the field of integrated circuits, including those based on analog design and those based on numbers, which may be called various simplifications and various multifarities. However, with the rapid development of integrated circuits in recent years, market competition is more intense, and demands for reduction in chip cost, increase in functions, optimization of performance, and the like are also more severe. It is certainly appreciated by engineers to design a compact, highly reliable slope detection circuit.
Simultaneously in the switching power supply field, along with the general use of new efficiency standard, more and more high to switching power supply's efficiency requirement, and use accurate resonance valley bottom to switch on and can effectively improve switching power supply's efficiency, reduce switching power supply temperature rise, improve switching power supply power density.
However, for the synchronous rectification controller on the secondary side, which is usually in a fixed voltage turn-on mode, how to avoid the false turn-on of the synchronous rectification controller in the quasi-resonance process is also a problem that needs to be solved urgently.
Disclosure of Invention
Aiming at the problems in the prior art, the slope detection circuit with the programmable blanking function is simple and high in reliability, can be applied to the field of switching power supplies, can effectively realize quasi-resonance valley bottom detection, and can prevent mistaken switching-on of a synchronous rectification controller caused by resonance in working modes such as DCM and QR.
The technical scheme adopted by the invention is as follows: a slope detection circuit with programmable blanking function comprises a slope generator, a programmable module, an amplitude modulation circuit, a capacitive coupling differential circuit and a comparison circuit;
a ramp generator for generating an initial blanking ramp signal according to the enable signal;
the programmable module and the amplitude modulation circuit are respectively connected with the ramp generator and are used for respectively adjusting the blanking ramp falling time and amplitude of the blanking ramp signal to form a ramp direct-current voltage signal with the required falling time and amplitude and a blanking function;
the capacitive coupling differential circuit is used for sampling the change slope of the SENSE terminal voltage and outputting a sampling voltage positively correlated with the change slope of the SENSE terminal voltage;
and the comparison circuit receives the superposed voltage of the sampling voltage and the ramp direct-current voltage signal, and compares the superposed voltage with a first threshold voltage and a second threshold voltage which are set inside respectively so as to judge whether the change slope of the SENSE terminal voltage reaches expectation or not and finish slope detection.
Further, the ramp generator comprises a first proportional current mirror circuit, a second proportional current mirror circuit, an NMOS transistor N01, a PMOS transistor P01 and a capacitor C01; the input end of the first proportional current mirror circuit is connected with the programmable module, and the output end of the first proportional current mirror circuit is connected with the input end of the second proportional current mirror circuit; the output end of the second proportional current mirror circuit is connected with the source electrode of an NMOS transistor N01; the drain electrode of the NMOS transistor N01 is connected with the drain electrode of the PMOS transistor P01 and the positive end of the capacitor C01; the negative end of the capacitor C01 is grounded; the source electrode of the PMOS transistor P01 is connected with VCC; and the gates of the NMOS transistor N01 and the PMOS transistor P01 are connected with an enable signal EN.
Furthermore, the programmable module is connected between the input end of the first proportional current mirror circuit and the ground, and the programmable function is realized through an adjustable resistor or an adjustable bias current.
Further, the amplitude modulation circuit comprises a PMOS (P-channel metal oxide semiconductor) tube P02, a bipolar transistor NPN1, a resistor R01, a resistor R02, a resistor R03 and a resistor R04; the resistor R01, the resistor R02 and the PMOS tube P02 are sequentially connected in series between a path from VCC to GND, the grid electrode of the PMOS tube P02 is connected with the positive end of the capacitor C01, the source electrode is connected with the resistor R02, and the drain electrode is grounded; the bipolar transistor NPN1 and the resistors R03 and R04 are sequentially connected in series between a circuit from VCC to GND, the base of the bipolar transistor NPN1 is connected with the series node of the resistors R01 and R02, the collector is connected with VCC, and the emitter is connected with the resistor R03; and the serial node of the resistor R03 and the resistor R04 is connected to the comparison circuit.
Furthermore, the positive end of the capacitive coupling differential circuit is connected to the SENSE end, and the negative end of the capacitive coupling differential circuit is connected to the comparison circuit.
Further, the capacitive coupling differential circuit is a capacitor or an MOS transistor.
Further, the comparison circuit comprises a fixed bias current circuit, a third proportion current mirror circuit, mirror image NMOS pair transistors N02 and N03 with the same size, resistors R05/R06 with the same specification, a first comparator COMP1 and a second comparator COMP2; the fixed bias current circuitThe constant bias current is connected between the input end of the third proportional current mirror circuit and GND (ground) to provide constant bias current; a first output end and a second output end of the third proportional current mirror circuit are respectively and correspondingly connected to drain electrodes of the mirror NMOS pair transistors N02 and N03; the grid electrodes of the mirror image NMOS pair transistors N02 and N03 are in short circuit and connected to the drain electrode of the NMOS transistor N03; one end of the resistor R05 is connected to the source electrode of the NMOS tube N02, and the other end of the resistor R05 is connected to the negative end of the capacitive coupling differential circuit and the series node of the resistor R03 and the resistor R04 of the amplitude modulation circuit; the resistor R06 is connected between the source electrode of the NMOS tube N03 and GND; the non-inverting input terminal of the first comparator COMP1 is connected with a first threshold voltage V TH1 The output end is the output pin of VOUT 1; the inverting input terminal of the second comparator COMP2 is connected with a second threshold voltage V TH2 The output end is the VOUT2 output pin; and the inverting input end of the first comparator COMP1 and the non-inverting input end of the second comparator COMP2 are connected to a node E between the drain electrode of the NMOS tube N02 and the first output end of the third proportional current mirror circuit.
Further, the slope detection process of the comparison circuit is as follows: VOUT1 outputs high level, which indicates that the slope of the falling edge of the SENSE end reaches a certain standard related to the first threshold voltage V TH1 (ii) a VOUT2 outputs high level, and the slope of the rising edge of the surface SENSE end reaches a certain standard which is related to the second threshold voltage V TH2 。。
Further, the comparison circuit further comprises a resonance valley bottom detection function: between the falling edge of the VOUT1 pulse signal and the rising edge of the VOUT2 pulse signal which is immediately behind the falling edge, a point that the change slope of the SENSE terminal voltage is 0 necessarily exists, and the point is a wave trough.
The invention also provides a switching power supply system which comprises a transformer, a switching power supply controller, a power switching tube, a synchronous rectification MOS tube, an output energy storage capacitor, a synchronous rectification controller and a programmable resistor; the slope detection circuit with the programmable blanking function is integrated in the synchronous rectification controller; the power switch tube drain electrode with the one end of the primary side of transformer is connected, and the source electrode is connected with ground, switching power supply controller's output with the grid of power switch tube links to each other, the drain terminal of synchronous rectification MOS pipe with the one end of the secondary side of transformer, synchronous rectification controller's slope sampling input SENSE end are connected, the source electrode ground connection of synchronous rectification MOS pipe, the grid end connection of synchronous rectification MOS pipe the output control end GATE of synchronous rectification controller, the VCC end of another termination output energy storage electric capacity of the secondary side of transformer and synchronous rectification controller is responsible for right the VCC that outputs energy storage electric capacity and synchronous rectification controller charges.
Compared with the prior art, the beneficial effects of adopting the technical scheme are as follows: 1. the slope detection circuit is simplified to the greatest extent, and reliability is guaranteed; 2. in the comparison circuit, a double-threshold comparison mode is introduced, so that the function of detecting the resonance valley bottom can be realized; 3. on the basis of a common slope detection circuit, a programmable blanking function is added and applied to a synchronous rectification control system, so that the slope detection of a resonance stage can be effectively shielded, the synchronous rectification controller is prevented from being switched on by mistake during resonance, and a power supply system is protected.
Drawings
Fig. 1 is a block diagram of a slope detection circuit with programmable blanking function according to the present invention.
Fig. 2 is a schematic diagram of a slope detection circuit with programmable blanking function according to an embodiment of the present invention.
Fig. 3 is a schematic diagram illustrating an operation of a slope detection circuit with programmable blanking function when a pulse signal is applied to a SENSE terminal according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of a switching power supply system employing a slope detection circuit with programmable blanking function.
Fig. 5 is a schematic diagram of the switching power supply system shown in fig. 4 for preventing the synchronous rectification controller from being turned on by mistake during resonance.
Fig. 6 is a schematic diagram of how to implement a resonance valley detection function when the slope detection circuit with programmable blanking function according to the embodiment of the present invention is applied to a switching power supply system.
Reference numerals are as follows: the circuit comprises a 1-ramp generator, a 2-programmable module, a 3-amplitude modulation circuit, a 4-capacitive coupling circuit, a 5-comparison circuit, a 6-transformer, a 7-switching power supply controller, an 8-power switching tube, a 9-synchronous rectification MOS tube, a 10-output energy storage capacitor and an 11-synchronous rectification controller.
Detailed Description
Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar modules or modules having the same or similar functionality throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application. On the contrary, the embodiments of the application include all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto.
Example 1
As shown in fig. 1, the present embodiment provides a slope detection circuit with programmable blanking function, which includes a slope generator 1, a programmable module 2, an amplitude modulation circuit 3, a capacitively coupled differential circuit 4, and a comparison circuit 5;
a ramp generator 1 for generating an initial blanking ramp signal according to an enable signal;
the programmable module 2 and the amplitude modulation circuit 3 are respectively connected with a ramp generator and are used for respectively adjusting the blanking ramp falling time and amplitude of the blanking ramp signal to form a ramp direct-current voltage signal with the required falling time and amplitude and a blanking function;
the capacitive coupling differential circuit 4 is used for sampling the change slope of the SENSE terminal voltage and outputting a sampling voltage positively correlated with the change slope of the SENSE terminal voltage;
and the comparison circuit 5 is used for receiving the superposed voltage of the sampling voltage and the ramp direct-current voltage signal and comparing the superposed voltage with a first threshold voltage and a second threshold voltage which are set inside respectively so as to judge whether the change slope of the SENSE terminal voltage reaches expectation or not and finish slope detection.
Specifically, as shown in fig. 2, the ramp generator 1 includes a first proportional current mirror circuit, a second proportional current mirror circuit, an NMOS transistor N01, a PMOS transistor P01, and a capacitor C01; the input end of the first proportional current mirror circuit is connected with the programmable module, and the output end of the first proportional current mirror circuit is connected with the input end of the second proportional current mirror circuit; the output end of the second proportional current mirror circuit is connected with the source electrode of an NMOS transistor N01; the drain electrode of the NMOS transistor N01 is connected with the drain electrode of the PMOS transistor P01 and the positive end of the capacitor C01; the negative end of the capacitor C01 is grounded; the source electrode of the PMOS transistor P01 is connected with VCC; the gates of the NMOS transistor N01 and the PMOS transistor P01 are both connected with an enable signal EN. Wherein, the first proportion current mirror circuit and the second proportion current mirror circuit are conventional parts of integrated circuits, and are formed by basic semiconductor devices such as MOS tubes or triodes, and the like, and the current mirror can be realized by any form of current mirror,
the programmable module 2 is connected between the input end of the first proportional current mirror circuit and the ground, and the programmable function is realized through an adjustable resistor or an adjustable bias current. In the present embodiment, the programmable module is mainly used to adjust the bias current I in FIG. 2 1 、I 2 、I 3 The discharge rate of the capacitor C01 is changed, and the falling time of the blanking ramp wave is adjusted.
The amplitude modulation circuit 3 comprises a PMOS (P-channel metal oxide semiconductor) tube P02, a bipolar transistor NPN1, a resistor R01, a resistor R02, a resistor R03 and a resistor R04; the resistor R01, the resistor R02 and the PMOS tube P02 are sequentially connected in series between a path from VCC to GND, the grid electrode of the PMOS tube P02 is connected with the positive end of the capacitor C01, the source electrode is connected with the resistor R02, and the drain electrode is grounded; the bipolar transistor NPN1 and the resistors R03 and R04 are sequentially connected in series between a circuit from VCC to GND, the base of the bipolar transistor NPN1 is connected with the series node of the resistors R01 and R02, the collector is connected with VCC, and the emitter is connected with the resistor R03; and the serial node of the resistor R03 and the resistor R04 is connected to the comparison circuit.
After the action of the ramp generator 1, the programmable module 2 and the amplitude modulation circuit 3, a ramp direct-current voltage signal V with proper fall time and amplitude and a blanking function is obtained C1 。
The positive terminal of the capacitively coupled differential circuit 4 is connected to the SENSE terminal and the negative terminal is connected to the comparator circuit. The capacitive coupling differential circuit is preferably implemented by using a capacitor or a MOS transistor, and in this embodiment, is implemented by using a capacitor. The capacitive coupling differential circuit samples the SENSE terminal voltage change rate and outputs a sampling voltage V positively correlated with the voltage change rate slope C2 Direct current with oblique wavePressure signal V C1 And the sampling voltage V C2 The voltage V of the C node in the figure 2 is obtained by superposition C Voltage V of C The change slope of the SENSE terminal voltage is also in a positive correlation relationship.
The comparison circuit 5 comprises a fixed bias current circuit, a third proportion current mirror circuit, mirror image NMOS (N-channel metal oxide semiconductor) pair transistors N02 and N03 with the same size, resistors R05/R06 with the same specification, a first comparator COMP1 and a second comparator COMP2; the fixed bias current circuit is connected between the input end of the third proportional current mirror circuit and GND (ground) to provide constant bias current; a first output end and a second output end of the third proportional current mirror circuit are respectively and correspondingly connected to drain electrodes of the mirror NMOS pair transistors N02 and N03; the grid electrodes of the mirror image NMOS pair transistors N02 and N03 are in short circuit and connected to the drain electrode of the NMOS transistor N03; one end of the resistor R05 is connected to the source electrode of the NMOS tube N02, and the other end of the resistor R05 is connected to the negative end of the capacitive coupling differential circuit and the series node of the resistor R03 and the resistor R04 of the amplitude modulation circuit; the resistor R06 is connected between the source electrode of the NMOS tube N03 and GND; the non-inverting input terminal of the first comparator COMP1 is connected with a first threshold voltage V TH1 The output end is the output pin of VOUT 1; the inverting input terminal of the second comparator COMP2 is connected with a second threshold voltage V TH2 The output end is the VOUT2 output pin; and the inverting input end of the first comparator COMP1 and the non-inverting input end of the second comparator COMP2 are both connected to a node E between the drain electrode of the NMOS tube N02 and the first output end of the third proportional current mirror circuit. It should be noted that, in this embodiment, the fixed bias current circuit may be implemented by any module or circuit capable of providing a constant bias current.
Further, the operation process of the slope detection circuit is specifically described with reference to fig. 1 and fig. 2, and at a node C in fig. 2, the following expression can be obtained from kirchhoff's current law:
usually bias current I 7 And I 4 Small, approximately negligible, i.e.:
when R is 04 And C X The value is small so that
When the method is used:
the expression can be derived:
this yields: in I 7 、I 4 、R 04 And C X When the circuit parameters are set within a reasonable range, V C And with
Approximately in a positive correlation relationship due to V E And V C Is also in a positive correlation, so V E And with
Again approximately in a positive correlation. SENSE, V in fig. 3, 5, 6 C 、V E The waveform of (A) is also apparent.
The slope detection circuit is applied to the synchronous rectification controller, and can effectively shield the slope detection function in the resonance stage when the blanking ramp signal works in a DCM (discontinuous reception) mode in the synchronous rectification controller, as shown in figure 5, when V is used for generating a programmable blanking ramp signal E >V TH1 The VOUT1 outputs a low level signal, so even when the SENSE terminal voltage is detected to be lower than the synchronous turn-on threshold, the GATE output terminal of the synchronous rectification controller will not be turned on because the slope sampling signal VOUT1, which is a necessary insufficient condition for the synchronous rectification controller to be turned on, cannot be turned over to a high level in time.
FIG. 3 shows the slope of the pulse signal applied to the SENSE terminalA detection circuit, a comparison circuit, and a voltage V at node E in FIG. 2 C The positive correlation voltage VE with an internally set first threshold voltage V TH1 And a second threshold voltage V TH2 A comparison is made (wherein the first threshold voltage V TH1 Less than a second threshold voltage V TH2 ) To judge whether the change slope of the SENSE terminal voltage reaches expectation; when SENSE terminal voltage changes slope
Is negative (i.e., falling edge) and is large enough that the superimposed voltage V E <V TH1 When the voltage is high, VOUT1 outputs high level; when the change slope of the SENSE terminal voltage
Is positive (i.e., rising edge) and is large enough that the superimposed voltage V E >V TH2 At this time, VOUT2 outputs high level, that is, VOUT1 outputs high level, indicating that the slope of the falling edge of SENSE terminal reaches a certain standard (the standard and the set first threshold voltage V) TH1 The specific numerical value should be determined according to specific applications); VOUT2 outputs high level, which indicates that the slope of rising edge of SENSE end reaches certain standard (the standard and the set second threshold voltage V) TH2 The specific numerical value should be determined according to specific applications); and between the falling edge of the VOUT1 pulse signal and the rising edge of the VOUT2 pulse signal immediately after the falling edge, the SENSE terminal voltage change slope is determined to exist
A point of 0, which is the trough.
Example 2
The embodiment proposes a switching power supply system, as shown in fig. 4, the switching power supply system includes a transformer 6, a switching power supply controller 7, a power switch tube 8, a synchronous rectification MOS tube 9, an output energy storage capacitor 10, a synchronous rectification controller 11, and a programmable resistor 12. The slope detection circuit with the programmable blanking function described in embodiment 1 is integrated in the synchronous rectification controller 11, wherein a programmable module in the original slope detection circuit is externally arranged on the synchronous rectification controller and is implemented by a programmable resistor 12.
Specifically, the drain of the power switch tube 8 is connected to one end of the primary side of the transformer 6, the source is connected to ground, the output of the switching power supply controller 7 is connected to the GATE of the power switch tube 8, the drain of the synchronous rectification MOS tube 9 is connected to one end of the secondary side of the transformer 6 and the slope sampling input SENSE end of the synchronous rectification controller 11, the source of the synchronous rectification MOS tube 9 is grounded, the GATE of the synchronous rectification MOS tube 9 is connected to the output control end GATE of the synchronous rectification controller 11, the other end of the secondary side of the transformer 6 is connected to the VCC end of the output energy storage capacitor 10 and the VCC end of the synchronous rectification controller 11, and is responsible for charging the VCC of the output energy storage capacitor 10 and the VCC end of the synchronous rectification controller 11.
The operation of the switching power supply system of the present embodiment will be described with reference to fig. 4 and 6.
When the switching power supply system works, the switching power supply controller 7 controls the power switch tube 8, no matter the power supply system works in a current continuous state, a current critical continuous state or a current discontinuous state, when the power switch tube 8 is switched on, energy is stored in the transformer 6, and the law of Faraday and Lenz can know that: the current of the primary side inductor of the transformer 6 gradually rises, the upper end of the induced voltage is positive, the lower end is negative, the lower end of the induced voltage of the secondary side inductor is positive, the upper end is negative, and the parasitic diode of the synchronous rectification MOS tube 9 is reversely biased at the moment, so that the drain-source voltage difference V of the synchronous rectification MOS tube 9 SENSE Becomes high with a magnitude equal to the sum of the output voltage and the secondary side inductor induced voltage.
When the power switch tube 8 is turned off, the primary side inductor current of the transformer 6 gradually decreases, the lower end of the induced voltage is positive and the upper end is negative, the upper end of the induced voltage of the secondary side inductor is positive and the lower end is negative, and the drain voltage V of the synchronous rectification MOS tube 9 SENSE And rapidly reducing, and conducting a parasitic diode of the synchronous rectification MOS tube 9 to realize follow current.
When the switching power supply system operates in the DCM state, the inductor current in the transformer 6 decreases to 0 (i.e. T in fig. 6) DEMAG After finishing), because of the influence of parasitic parameters such as parasitic capacitance of the synchronous rectification MOS transistor 9, the switching power supply system starts to enter a resonance/excitation oscillation process, as shown by a DRAIN terminal waveform in fig. 6, if the switching power supply controller 7 has a quasi-resonance valley bottom conduction function, at a certain specific valley bottom, the switching power supply controller 7 will be turned on, control the power switching transistor 8 to be turned on, pull down the DRAIN terminal voltage to 0, and the actual waveform is the DRAIN terminal voltage in fig. 6 VALLEY As shown.
The principle is briefly explained with reference to fig. 6: in fig. 6, a valley bottom must exist between the 1 st pulse falling edge of VOUT1 and the 1 st pulse rising edge of VOUT2, the 2 nd pulse falling edge of VOUT1 and the 2 nd pulse rising edge of VOUT2, the 3 rd pulse falling edge of VOUT1 and the 3 rd pulse rising edge of VOUT2, the 4 th pulse falling edge of VOUT1 and the 4 th pulse rising edge of VOUT2 \ 8230; \ 8230; the nth pulse falling edge of VOUT1 and the nth pulse rising edge of VOUT2 (n is a positive integer meaningful in practical circuit system applications), and the selection of the conduction of the several valley bottoms can be determined according to practical application requirements, where the 4 th valley bottom is illustrated as an example, and it is assumed that V corresponds to the 4 th valley bottom at DRAIN terminal E Has a voltage value of V CENTER If and only if V TH1 、V TH2 Infinitely approaching V CENTER During the process, the 4 th pulse falling edge of VOUT1 and the 4 th pulse rising edge of VOUT2 are infinitely close to each other, that is, the 4 th pulse falling edge of VOUT1 or the 4 th pulse rising of VOUT2 is considered to correspond to the valley bottom of the waveform of the DRAIN terminal, and at this time, the switching power supply controller is controlled to be turned on, that is, the waveform of the quasi-resonance valley bottom conduction is as the waveform of DRAIN u \ in fig. 6 VALLEY As shown.
Referring to fig. 5, it is a schematic diagram of the switching power supply system shown in fig. 4 for preventing the synchronous rectification controller from being turned on by mistake during the resonant/excited oscillation, and at the resonant/excited oscillation stage, the width of the blanking ramp is manually set by adjusting the programmable resistor 12 according to an empirical value or according to a special application requirement, so as to make V E Higher than V throughout the resonant/excited oscillation phase TH1 And VOUT1 is constantly low, so that the synchronous rectification controller can be prevented from being switched on by mistake at the stage, and the normal work of the whole system is further ensured.
It should be noted that the slope detection circuit of the present invention can be applied to any other electronic circuit that needs to detect the slope of the voltage change besides the switching power supply, and the invention should be within the scope of the claimed invention without departing from the spirit and scope of the present invention.
It should be noted that, in the description of the embodiments of the present invention, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; may be directly connected or may be indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood as specific cases to those of ordinary skill in the art; the drawings in the embodiments are used for clearly and completely describing the technical scheme in the embodiments of the invention, and obviously, the described embodiments are a part of the embodiments of the invention, but not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.
Claims (10)
1. A slope detection circuit with programmable blanking function is characterized by comprising a ramp generator, a programmable module, an amplitude modulation circuit, a capacitive coupling differential circuit and a comparison circuit;
the ramp generator generates an initial blanking ramp signal according to the enable signal;
the programmable module and the amplitude modulation circuit are respectively connected with a ramp generator and are used for respectively adjusting the blanking ramp falling time and amplitude of the blanking ramp signal to form a ramp direct-current voltage signal with required falling time and amplitude and a blanking function;
the capacitive coupling differential circuit is used for sampling the change slope of the SENSE terminal voltage and outputting a sampling voltage positively correlated with the change slope of the SENSE terminal voltage;
and the comparison circuit receives the superposed voltage of the sampling voltage and the ramp direct-current voltage signal, and compares the superposed voltage with a first threshold voltage and a second threshold voltage which are internally set respectively so as to judge whether the change slope of the SENSE terminal voltage reaches expectation or not and finish slope detection.
2. The slope detection circuit with programmable blanking function according to claim 1, wherein the slope generator comprises a first proportional current mirror circuit, a second proportional current mirror circuit, an NMOS transistor N01, a PMOS transistor P01, a capacitor C01; the input end of the first proportional current mirror circuit is connected with the programmable module, and the output end of the first proportional current mirror circuit is connected with the input end of the second proportional current mirror circuit; the output end of the second proportional current mirror circuit is connected with the source electrode of an NMOS transistor N01; the drain electrode of the NMOS transistor N01 is connected with the drain electrode of the PMOS transistor P01 and the positive end of the capacitor C01; the negative end of the capacitor C01 is grounded; the source electrode of the PMOS transistor P01 is connected with VCC; the gates of the NMOS transistor N01 and the PMOS transistor P01 are both connected with an enable signal EN.
3. The slope detection circuit with programmable blanking function of claim 2, wherein the programmable module is connected between the input of the first proportional current mirror circuit and ground, and the programmable function is realized by an adjustable resistor or an adjustable bias current.
4. The slope detection circuit with programmable blanking function according to claim 3, wherein the amplitude modulation circuit comprises a PMOS transistor P02, a bipolar transistor NPN1, a resistor R01, a resistor R02, a resistor R03 and a resistor R04; the resistor R01, the resistor R02 and the PMOS tube P02 are sequentially connected in series between a path from VCC to GND, the grid electrode of the PMOS tube P02 is connected with the positive end of the capacitor C01, the source electrode is connected with the resistor R02, and the drain electrode is grounded; the bipolar transistor NPN1 and the resistors R03 and R04 are sequentially connected in series between a circuit from VCC to GND, the base of the bipolar transistor NPN1 is connected with the series node of the resistors R01 and R02, the collector is connected with VCC, and the emitter is connected with the resistor R03; and the serial node of the resistor R03 and the resistor R04 is connected to the comparison circuit.
5. The slope detection circuit with programmable blanking function of claim 4 wherein the positive terminal of the capacitively coupled differentiating circuit is connected to a SENSE terminal and the negative terminal is connected to a comparing circuit.
6. The slope detection circuit with programmable blanking function of claim 5, wherein the capacitively coupled differentiating circuit is a capacitor or a MOS transistor.
7. The slope detection circuit with programmable blanking function according to claim 5, wherein the comparison circuit comprises a fixed bias current circuit, a third proportional current mirror circuit, mirror NMOS pair transistors N02 and N03 of the same size, a resistor R05/R06 of the same specification, and a first comparator COMP1 and a second comparator COMP2; the fixed bias current circuit is connected between the input end of the third proportional current mirror circuit and GND and provides constant bias current; a first output end and a second output end of the third proportional current mirror circuit are respectively and correspondingly connected to drain electrodes of mirror image NMOS pair transistors N02 and N03; the grid electrodes of the mirror image NMOS pair transistors N02 and N03 are in short circuit and connected to the drain electrode of the NMOS transistor N03; one end of the resistor R05 is connected to the source electrode of the NMOS tube N02, and the other end of the resistor R05 is connected to the negative end of the capacitive coupling differential circuit and the series node of the resistor R03 and the resistor R04 of the amplitude modulation circuit; the resistor R06 is connected between the source electrode of the NMOS tube N03 and GND; the non-inverting input terminal of the first comparator COMP1 is connected with a first threshold voltage V TH1 The output end is the output pin of VOUT 1; the inverting input terminal of the second comparator COMP2 is connected with a second threshold voltage V TH2 The output end is the VOUT2 output pin; and the inverting input end of the first comparator COMP1 and the non-inverting input end of the second comparator COMP2 are both connected to a node E between the drain electrode of the NMOS tube N02 and the first output end of the third proportional current mirror circuit.
8. Slope detection circuit with programmable blanking function according to claim 7The slope detection method of the comparison circuit is characterized in that: VOUT1 outputs high level, which indicates that the slope of the falling edge of the SENSE end reaches a certain standard related to the first threshold voltage V TH1 (ii) a VOUT2 outputs high level, and the slope of the rising edge of the surface SENSE end reaches a certain standard which is related to the second threshold voltage V TH2 。
9. The slope detection circuit with programmable blanking function of claim 8 wherein the comparison circuit further comprises a resonant valley detection function: between the falling edge of the VOUT1 pulse signal and the rising edge of the VOUT2 pulse signal which is immediately behind the falling edge, a point that the change slope of the SENSE terminal voltage is 0 necessarily exists, and the point is a wave trough.
10. A switching power supply system comprises a transformer, a switching power supply controller, a power switch tube, a synchronous rectification MOS tube, an output energy storage capacitor, a synchronous rectification controller and a programmable resistor; a slope detection circuit with a programmable blanking function as claimed in any one of claims 1 to 9 is integrated in the synchronous rectification controller; the power switch tube drain electrode with the one end of the primary side of transformer is connected, and the source electrode is connected with ground, switching power supply controller's output with the grid of power switch tube links to each other, the drain terminal of synchronous rectification MOS pipe with the one end of the secondary side of transformer, synchronous rectification controller's slope sampling input SENSE end are connected, the source electrode ground connection of synchronous rectification MOS pipe, the grid end connection of synchronous rectification MOS pipe the output control end GATE of synchronous rectification controller, the VCC end of another termination output energy storage electric capacity of the secondary side of transformer and synchronous rectification controller is responsible for right the VCC that outputs energy storage electric capacity and synchronous rectification controller charges.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210876290.0A CN115184666A (en) | 2022-07-25 | 2022-07-25 | Slope detection circuit with programmable blanking function and switching power supply system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210876290.0A CN115184666A (en) | 2022-07-25 | 2022-07-25 | Slope detection circuit with programmable blanking function and switching power supply system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115184666A true CN115184666A (en) | 2022-10-14 |
Family
ID=83521637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210876290.0A Pending CN115184666A (en) | 2022-07-25 | 2022-07-25 | Slope detection circuit with programmable blanking function and switching power supply system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115184666A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118112310A (en) * | 2024-04-30 | 2024-05-31 | 江苏帝奥微电子股份有限公司 | Voltage positive and negative slope detection circuit and detection method thereof |
-
2022
- 2022-07-25 CN CN202210876290.0A patent/CN115184666A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118112310A (en) * | 2024-04-30 | 2024-05-31 | 江苏帝奥微电子股份有限公司 | Voltage positive and negative slope detection circuit and detection method thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7492615B2 (en) | Switching power supply | |
| US7701735B2 (en) | Converter and driving method thereof | |
| US7898823B2 (en) | Quasi-resonant fly-back converter without auxiliary winding | |
| US7773392B2 (en) | Isolated switching power supply apparatus | |
| TWI455462B (en) | Quasi-resonant power supply controller and method therefor | |
| US7382633B2 (en) | DC converter | |
| CN108880266B (en) | Synchronous rectification circuit, chip and isolated synchronous rectification control circuit | |
| US20110002068A1 (en) | Switching regulator with fault protection and method thereof | |
| US20130222044A1 (en) | Power transistor driving circuits and methods for switching mode power supplies | |
| US8638572B2 (en) | Apparatus and method for detecting a change in output voltage of an isolated power converter | |
| US20060198167A1 (en) | Switching power supply | |
| US20220209676A1 (en) | Isolated switching converter with secondary side modulation and control method thereof | |
| JP7095784B2 (en) | Switching power supply | |
| CN115184666A (en) | Slope detection circuit with programmable blanking function and switching power supply system | |
| US12244233B2 (en) | Integrated circuit having switching control and power supply circuit including the same | |
| CN111669033B (en) | Synchronous rectifier tube control circuit, flyback voltage conversion circuit and control method | |
| US7518888B2 (en) | Control circuit and method for a fly-back voltage converter | |
| CN212875655U (en) | Synchronous rectifier control circuit and flyback voltage conversion circuit | |
| US20240039389A1 (en) | Isolated switching converter with soft switching and control method thereof | |
| JP5143095B2 (en) | Switching power supply | |
| CN118677261A (en) | Synchronous rectifier scheme to avoid transconductance in flyback converters | |
| US12119755B2 (en) | Synchronous rectifier scheme for continuous conduction mode in primary side controlled fly-back converter | |
| TW202508201A (en) | Control chip and control method for quasi-resonant switching power supply and quasi-resonant switching power supply | |
| US12155311B2 (en) | Integrated circuit for load-state-based control and power supply circuit containing the same | |
| JP2006353095A (en) | POWER SUPPLY DEVICE, ITS CONTROL CIRCUIT, AND CONTROL METHOD |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |