CN103630735A - Voltage slope change detection circuit and method - Google Patents
Voltage slope change detection circuit and method Download PDFInfo
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- CN103630735A CN103630735A CN201210308245.1A CN201210308245A CN103630735A CN 103630735 A CN103630735 A CN 103630735A CN 201210308245 A CN201210308245 A CN 201210308245A CN 103630735 A CN103630735 A CN 103630735A
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Abstract
The invention discloses a voltage slope change detection circuit and method. A charging-discharging current is extracted by utilizing a dV/dT change slope during the capacitor charging and discharging process; and the current is compared with a reference current and thus the corresponding time is detected when the dV/dT is changed, so that the changed sudden changing time can be detected when the voltage slope is changed greatly. The provided voltage slope change detection circuit can be applied to, but be not limited to, secondary inductive current zero-cross detection of a primary-side control optocoupler feedback-free flyback switch power supply.
Description
Technical field
The present invention relates to a kind of voltage slope change detecting circuit and method, be mainly used in former limit and control inverse-excitation type (Flyback) the Switching Power Supply secondary side inductive current zero passage detection without optocoupler feedback, can detect exactly secondary side inductive current and discharge into for zero the moment.
Background technology
Inverse-excitation type (Flyback) Switching Power Supply that the control of former limit is fed back without optocoupler is because its peripheral component is few, and cost is low, thereby at charger for mobile phone, in isolated LED illumination, is used widely.
It is example that the isolated LED illumination of take drives, and typical former limit is controlled without the Flyback of optocoupler feedback as shown in Figure 1.It comprises: 105, one primary inductance electric current inductive reactances 106 of 103, one NMOS power switch pipes of 102, one former limit pwm chips of 101, one VCC regulators of transformer and output rectifier and filter and feedback resistive network, and LED load 107.
Transformer and output rectifier and filter 101 are for being transformed into secondary LED constant current output end VOUT by interchange input electric energy.Wherein input power VIN is coupled on the former limit of transformer.Secondary output commutation diode D1 and the filter capacitor C1 of being coupled to of transformer.The auxiliary winding coupled of transformer is to VCC regulator and feedback resistive network 102.
VCC regulator and feedback resistive network 102 are given former limit pwm chip 103 for generation of VCC DC voltage and signal VFB.VCC DC voltage is used for to 103 power supplies of former limit pwm chip.VFB is used for providing the indirectly information of LED output current and voltage to former limit pwm chip 103, for former limit pwm chip 103, controls LED output constant current.
The primary inductance current sense voltage VCS generating on the feedback signal VFB that the auxiliary winding feedback resistive network 102 of former limit pwm chip 103 utilization generates and resistance 106, the conducting cut-off signals GATE of generation NMOS power switch pipe 105.
So by the conducting of periodic NMOS power switch pipe 105, turn-off, the GATE signal controlling that it is generated by former limit pwm chip 103, the electric energy that exchanges input VIN is converted to the constant current output energy of LED by transformer and output rectifier and filter 101.
Fig. 2 shows the voltage waveform AUX on a typical inverse-excitation type LED drive circuit secondary inductance current IS EC and auxiliary winding.By figure, know that inverse-excitation type LED constant current is determined by following formula:
N wherein
xbe the turn ratio of transformer and secondary coil, IPRIPK is primary inductance peak point current, T
dEMAGbe that secondary inductance current discharge arrives for zero time, fsw is NMOS pipe switching frequency.
Suppose that IPRIPK can accurately be controlled by former limit control chip 103 internal reference voltages and outside inductive reactance 106, fsw determines frequency operation, by above formula finding, wants LED IOUT constant current, T
dEMAGit is more accurately better to need.
By Fig. 2, at the T of secondary inductance current IS EC electric discharge
dEMAGin time, the voltage waveform descending slope of AUX is less, and it is mainly by the reducing of pressure drop On current on secondary side commutation diode, to be reduced to determine, so AUX voltage is approximate constant.When secondary inductance current IS EC discharges into zero, the stray capacitance of the inductance on former limit and nmos switch pipe 105 drain terminals causes resonance, is coupled to AUX signal, so AUX change in voltage is very fast.If can detect the turning point that AUX signal dV/dT changes, secondary inductance current IS EC discharges into zero time T
dEMAGjust can detect accurately, thereby can control LED output constant current.
In sum, need one can accurately detect the circuit that voltage slope changes, realize inverse-excitation type LED and drive the zero crossing of secondary inductance current discharge to detect, the accurate constant current driving to realize LED.
Summary of the invention
For above-mentioned problems of the prior art, the object of the invention is: provide a kind of and can accurately detect circuit and the method that voltage slope changes, realize inverse-excitation type LED and drive the zero crossing of secondary inductance current discharge to detect, the accurate constant current driving to realize LED.
The technical solution adopted for the present invention to solve the technical problems is:
A voltage slope change detecting circuit, comprising: an electric capacity, a PMOS voltage follower, a pair of NMOS tube of current, a current reference and a phase inverter, and described a pair of NMOS tube of current comprises: current mirror supervisor NMOS and current mirror mirror image pipe NMOS; The integrated circuit structure of described testing circuit is:
One termination power VCC of electric capacity or ground, the source electrode of another termination PMOS pipe, the grid of PMOS pipe connects input voltage, the drain electrode of PMOS pipe connects the drain electrode of current mirror supervisor NMOS, the source ground of current mirror supervisor NMOS, the grid of current mirror supervisor NMOS connects current mirror supervisor's drain electrode of NMOS and the grid of current mirror mirror image pipe NMOS, the source ground of current mirror mirror image pipe NMOS, the drain electrode of current mirror mirror image pipe NMOS connects one end of current reference, another termination power VCC of current reference, the drain electrode of current mirror mirror image pipe NMOS connects the input end of phase inverter simultaneously, the output termination output signal of phase inverter.
Described power supply VCC provides an input current for whole circuit.
Described PMOS voltage follower is used for following the tracks of the variation of applied signal voltage, and this variation is converted to the change in voltage on electric capacity.
Described current mirror supervisor NMOS can utilize the change in voltage on electric capacity to produce an electric current proportional to dV/dT.
Described current mirror mirror image pipe NMOS can generate another one proportional image current with it by described current mirror proportional to dV/dT.
Described current reference can produce a reference current, for described image current comparison.
Described phase inverter can amplify described image current and the relatively rear result of described reference current export.
Described PMOS voltage follower and described NMOS tube of current can substitute mutually, and PMOS voltage follower can adopt NMOS tube of current to substitute, or described NMOS tube of current can adopt PMOS voltage follower to substitute.
A voltage slope change detecting method, comprises the following steps:
S1: go to follow the variation of applied signal voltage with a PMOS voltage follower, and this variation is converted to the variation of the voltage on electric capacity;
S2: the change in voltage on electric capacity is generated to an electric current proportional to dV/dT with a NMOS current mirror pipe;
S3: utilize another NMOS current mirror pipe to generate an image current in the electric current generating in S2 step;
S4: by the reference current comparison of the image current generating in S3 step and a current reference generation, and export a comparative result;
S5: output after utilizing phase inverter that the comparative result of exporting in S4 step is amplified.
In addition, another NMOS current mirror pipe described in NMOS current mirror pipe described in S2 step and S3 step forms a pair of NMOS current mirror pipe, and the NMOS current mirror pipe described in S2 step is current mirror supervisor, and another NMOS current mirror pipe described in S3 step is current mirror mirror image pipe.
When input voltage VIN changes, utilize the voltage dV/dT on corresponding electric capacity to change, produce the capacitor discharge electric current I 1 of an induction.This electric current is mirrored rear same reference current and compares, and after phase inverter amplifies, exports TRB.
When input voltage VIN changes hour, the electric current sensing on electric capacity is less than reference current, so output TRB signal is low level.
When input voltage VIN changes greatly, the electric current sensing on electric capacity is greater than reference current, so output TRB signal is high level.
The invention has the beneficial effects as follows: according to the size of input voltage VIN slope variation, voltage slope change detecting circuit of the present invention just can accurately detect the turning point of VIN slope variation.Specific to inverse-excitation type LED drive circuit, because AUX voltage can vary widely to zero time at secondary inductance current discharge, as shown in Figure 2, thereby voltage slope change detecting circuit of the present invention can accurately detect the moment of secondary inductance current discharge to zero.
Accompanying drawing explanation
Fig. 1 is that inverse-excitation type LED drive circuit is controlled on a typical former limit.
Fig. 2 is the oscillogram of typical AUX voltage and secondary inductance electric current in Fig. 1.
Fig. 3 is the realization of a voltage slope change detecting circuit of the present invention.
Fig. 4 is the oscillogram for the implementing circuit shown in key diagram 3.
Fig. 5 is that the another kind of voltage slope change detecting circuit of the present invention is realized.
Embodiment
In conjunction with the accompanying drawings, the present invention is further detailed explanation.
Voltage slope change detecting circuit of the present invention comprises 301, one voltage follow PMOS pipes 302 of an electric capacity, a pair of NMOS current mirror pipe 303 and 304, one current references 305, and a phase inverter 306.
One termination power VCC of electric capacity 301, the source electrode of another termination PMOS pipe 302.The grid of PMOS302 connects input voltage VIN, and drain electrode connects the drain electrode of current mirror NMOS pipe 303.303 source ground, grid connects its drain electrode and 304 grid.304 source ground, drain electrode connects one end of current reference 305.Another termination power VCC of 305.304 drain electrode connects the input end of phase inverter 306 simultaneously, and 306 output terminal is TRB signal.
When VIN slowly reduces, the source voltage terminal VA of PMOS voltage follower 302 also reduces gradually, thereby on electric capacity 301, forms pressure reduction variation.Fundamental formular by capacitor charging
So little pressure reduction changes a very little electric current I 1 of meeting generation on electric capacity.Yet when VIN alters a great deal, the variation dV/dT of pressure reduction also can aggravate on electric capacity, thereby produce a very large electric current I 1.This electric current I 1 is sensed by NMOS pipe 303, and is mirrored onto NMOS pipe 304.Image current then same current reference 305 is compared, and result is inverted after device 306 amplifies and exports TRB.
As can be seen here, as the change in voltage dV/dT hour of VIN, on electric capacity 301, the electric current of induction is less than current reference 305, and output TRB is low level.When the change in voltage dV/dT of VIN is large, on electric capacity 301, the electric current of induction is greater than current reference 305, and output TRB is high level.TRB with the oscillogram of VIN slope variation as shown in Figure 4.
So according to the size of input voltage VIN slope variation, voltage slope change detecting circuit of the present invention just can accurately detect the turning point of VIN slope variation.Specific to inverse-excitation type LED drive circuit, because AUX voltage can vary widely to zero time at secondary inductance current discharge, as shown in Figure 2, thereby voltage slope change detecting circuit of the present invention can accurately detect the moment of secondary inductance current discharge to zero.
One end of electric capacity 301 in voltage slope change detecting circuit of the present invention shown in Fig. 3 is connected on power supply VCC.Be not difficult to find out, if an end of this electric capacity is connected on the ground, as shown in Figure 5, voltage slope change detecting circuit can work equally.
The above-described preferred embodiment of utilizing describes the present invention in detail, but not limits the scope of the invention.Those skilled in the art can be by reading after the present invention, make trickle change and adjustment, for example: experienced slip-stick artist is also not difficult to find out the voltage slope change detecting circuit with Fig. 3 complementary type, make PMOS follower wherein into NMOS follower, the current mirror of nmos type makes current mirror of pmos type etc. into, the main idea of the present invention of will can yet be regarded as place, does not also depart from the spirit and scope of the present invention.
Claims (9)
1. a voltage slope change detecting circuit, comprising: an electric capacity, a PMOS voltage follower, a pair of NMOS tube of current, a current reference and a phase inverter, and described a pair of NMOS tube of current comprises: current mirror supervisor NMOS and current mirror mirror image pipe NMOS; It is characterized in that, the integrated circuit structure of described testing circuit is:
One termination power VCC of electric capacity or ground, the source electrode of another termination PMOS pipe, the grid of PMOS pipe connects input voltage, the drain electrode of PMOS pipe connects the drain electrode of current mirror supervisor NMOS, the source ground of current mirror supervisor NMOS, the grid of current mirror supervisor NMOS connects current mirror supervisor's drain electrode of NMOS and the grid of current mirror mirror image pipe NMOS, the source ground of current mirror mirror image pipe NMOS, the drain electrode of current mirror mirror image pipe NMOS connects one end of current reference, another termination power VCC of current reference, the drain electrode of current mirror mirror image pipe NMOS connects the input end of phase inverter simultaneously, the output termination output signal of phase inverter.
2. a kind of voltage slope change detecting circuit as claimed in claim 1, is characterized in that, described PMOS voltage follower is used for following the tracks of the variation of applied signal voltage, and this variation is converted to the change in voltage on electric capacity.
3. a kind of voltage slope change detecting circuit as claimed in claim 2, is characterized in that, described current mirror supervisor NMOS can utilize the change in voltage on electric capacity to produce an electric current proportional to dV/dT.
4. a kind of voltage slope change detecting circuit as claimed in claim 3, is characterized in that, described current mirror mirror image pipe NMOS can generate another one proportional image current with it by described current mirror proportional to dV/dT.
5. a kind of voltage slope change detecting circuit as claimed in claim 4, is characterized in that, described current reference can produce a reference current, for described image current comparison.
6. a kind of voltage slope change detecting circuit as claimed in claim 5, is characterized in that, described phase inverter can amplify described image current and the relatively rear result of described reference current export.
7. a kind of voltage slope change detecting circuit as claimed in claim 1, it is characterized in that, described PMOS voltage follower and described NMOS tube of current can substitute mutually, be that PMOS voltage follower can adopt NMOS tube of current to substitute, or described NMOS tube of current can adopt PMOS voltage follower to substitute.
8. a voltage slope change detecting method, is characterized in that, comprises the following steps:
S1: go to follow the variation of applied signal voltage with a PMOS voltage follower, and this variation is converted to the variation of the voltage on electric capacity;
S2: the change in voltage on electric capacity is generated to an electric current proportional to dV/dT with a NMOS current mirror pipe;
S3: utilize another NMOS current mirror pipe to generate an image current in the electric current generating in S2 step;
S4: by the reference current comparison of the image current generating in S3 step and a current reference generation, and export a comparative result;
S5: output after utilizing phase inverter that the comparative result of exporting in S4 step is amplified.
9. a kind of voltage slope change detecting method as claimed in claim 8, it is characterized in that, another NMOS current mirror pipe described in NMOS current mirror pipe described in S2 step and S3 step forms a pair of NMOS current mirror pipe, and the NMOS current mirror pipe described in S2 step is current mirror supervisor, and another NMOS current mirror pipe described in S3 step is current mirror mirror image pipe.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201210308245.1A CN103630735B (en) | 2012-08-27 | 2012-08-27 | A kind of voltage slope change detection circuit and method |
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| CN201210308245.1A CN103630735B (en) | 2012-08-27 | 2012-08-27 | A kind of voltage slope change detection circuit and method |
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| CN103630735A true CN103630735A (en) | 2014-03-12 |
| CN103630735B CN103630735B (en) | 2016-04-13 |
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| CN201210308245.1A Expired - Fee Related CN103630735B (en) | 2012-08-27 | 2012-08-27 | A kind of voltage slope change detection circuit and method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104952403A (en) * | 2014-03-27 | 2015-09-30 | 精工爱普生株式会社 | Driver, electro-optical device, and electronic device |
| CN106338644A (en) * | 2015-11-27 | 2017-01-18 | 深圳市中兴物联科技股份有限公司 | Voltage change rate detection method and device |
| CN110879346A (en) * | 2018-09-06 | 2020-03-13 | 恩智浦有限公司 | System and method for detecting tampering with a product |
| CN110879346B (en) * | 2018-09-06 | 2024-04-23 | 恩智浦有限公司 | System and method for detecting tampering with a product |
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| EP0582289A1 (en) * | 1992-08-04 | 1994-02-09 | Nec Corporation | Transistor circuit for holding peak/bottom level of signal |
| CN101286704A (en) * | 2007-04-13 | 2008-10-15 | 凌特公司 | Determining average output current in dc-dc converter |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104952403A (en) * | 2014-03-27 | 2015-09-30 | 精工爱普生株式会社 | Driver, electro-optical device, and electronic device |
| CN106338644A (en) * | 2015-11-27 | 2017-01-18 | 深圳市中兴物联科技股份有限公司 | Voltage change rate detection method and device |
| CN106338644B (en) * | 2015-11-27 | 2019-03-08 | 深圳市中兴物联科技有限公司 | Voltage change ratio detection method and device |
| CN110879346A (en) * | 2018-09-06 | 2020-03-13 | 恩智浦有限公司 | System and method for detecting tampering with a product |
| CN110879346B (en) * | 2018-09-06 | 2024-04-23 | 恩智浦有限公司 | System and method for detecting tampering with a product |
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| CN103630735B (en) | 2016-04-13 |
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