CN107196272B - A kind of continuous protective device of Switching Power Supply armature winding peak point current depth - Google Patents
A kind of continuous protective device of Switching Power Supply armature winding peak point current depth Download PDFInfo
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- CN107196272B CN107196272B CN201710549513.1A CN201710549513A CN107196272B CN 107196272 B CN107196272 B CN 107196272B CN 201710549513 A CN201710549513 A CN 201710549513A CN 107196272 B CN107196272 B CN 107196272B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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Abstract
The invention discloses a kind of continuous protective device of Switching Power Supply armature winding peak point current depth, which starts to work normally after secondary side output voltage reaches starting voltage；Oscillator and delay unit match, and generate locked level signal after waiting a predetermined period；Output detection unit judges secondary side output voltage size by threshold voltage；Two shielding times are arranged in lead-edge-blanking unit within the unblocked level duration of driving signal, and a shielding time is smaller, open voltage glitch of the moment generation on CS sampling resistor for shielding power tube, another shielding time is larger；Control unit is in the given time, when secondary side output voltage is lower, the unblocked level duration of driving signal is detected with the biggish shielding time, if respectively less than shielding time unblocked level duration in the continuous predetermined number period, controls power tube and persistently turn off.The present invention is able to detect that armature winding work switch-off power pipe in depth continuous current mode.
Description
Technical field
The present invention relates to power technique fields, continuous more particularly to a kind of Switching Power Supply armature winding peak point current depth
Protective device.
Background technique
Requirement with the update of the powerful demand of consumption electronic product and various electronic products, to power module
Also higher and higher.Power module is usually that functional module provides constant voltage or constant electric current, to guarantee that they are stable
Work.
As shown in Figure 1, being a kind of simplification topology diagram of secondary side feedback Switching Power Supply of the prior art.The Switching Power Supply packet
Include driving circuit 10, comparison circuit 20 and power tube 30.Comparison circuit 20 is for comparing CS sampling resistor RCSOn sampled voltage
And threshold voltage, driving circuit 10 are used to send driving signal to power tube 30 according to the comparison result of comparison circuit 20 to drive
Power tube 30 is switched on or off, wherein a cycle of driving signal is made of unblocked level and shutdown level, in unblocked level
During duration, power tube is opened, and during turning off level duration, power tube is turned off, unblocked level and shutdown level
In one be low level, another is high level.Specifically, when 10 driving power pipe 30 of driving circuit is opened, it is primary
Winding storage energy, the electric current on armature winding rise, and the rate of rise VIN/LP, VIN are the electricity on primary winding
Pressure, LP are the inductance of armature winding, CS sampling resistor RCSOn sampled voltage linear rise, comparison circuit 20 by detection sampling
Voltage detects the electric current on armature winding indirectly.When the electric current on armature winding reaches peak point current ipeak, sampled voltage
Also threshold voltage vt h_ocp is risen to, therefore, driving circuit 10 needs driving power pipe 30 to turn off.Due to being opened in power tube 30
It opens moment, CS sampling resistor RCSUpper meeting coupled voltages burr, the voltage glitch are much larger than threshold voltage, collect electricity in order to prevent
Dabbing pierces and misses switch-off power pipe 30, therefore comparison circuit 20 is provided with blanking time, 20 meeting of comparison circuit within the blanking time
Shield CS sampling resistor RCSOn voltage glitch.
At work, when output connects load, as power tube 30 is opened, armature winding will for the secondary side feedback Switching Power Supply
For energy transmission to secondary windings, the electric current on secondary windings is equal to the electric current and turn ratio product of armature winding, i.e. IS=IP× N, it is secondary
High current will be generated on grade winding, will be powered simultaneously to load and output capacitance.If output is the big capacitive load of impedance, output
Voltage VOUT rises will very slowly, at the same time, when output voltage VO UT is lower, and the switching frequency of power tube 30 is maximum, examination
Scheme to provide more energy to output, but at this time because the both ends pressure difference of secondary inductance is small, the electric current descending slope of secondary inductance
Gently, therefore the demagnetization time of secondary inductance is long, causes power tube 30 when opening next time, and the electric current in secondary inductance does not have
It is reduced to zero.So armature winding works in continuous current mode during rising on the output voltage vout, and because output
Voltage VOUT is low, and the switching frequency of power tube 30 is maximum, does not reduce by zero in the turn-off time secondary current of power tube 30, then
The electric current of armature winding can not stop to accumulate in each open, although the electric current of armature winding is not stopping to accumulate, driving circuit 10
Still needing to wait until after the blanking time could switch-off power pipe 30, that is to say, that the duration that power tube 30 is opened every time is equal
For blanking time, the blanking time interior electric current not detected on armature winding, then the electricity within the blanking time on armature winding again
Stream continues to build up, and when the electric current of accumulation is more than peak point current, if being further continued for accumulating, will result in high current and burns chip.
Summary of the invention
The invention mainly solves the technical problem of providing a kind of Switching Power Supply armature winding peak point current depth continuously to protect
Protection unit is able to detect that armature winding work switch-off power pipe in depth continuous current mode.
In order to solve the above technical problems, one technical scheme adopted by the invention is that: provide a kind of Switching Power Supply primary around
The group continuous protective device of peak point current depth, is applied to secondary side feedback Switching Power Supply, and the Switching Power Supply includes driving circuit, ratio
Compared with circuit and power tube, the comparison circuit is used to compare the sampled voltage and threshold voltage on CS sampling resistor, the driving
Circuit is used to send driving signal to the power tube according to the comparison result of the comparison circuit to drive the power tube to open
It opens or turns off, a cycle of the driving signal is made of unblocked level and shutdown level, in phase unblocked level duration
Between, power tube is opened, and during turning off level duration, power tube shutdown, the device includes voltage detection unit, oscillation
Device, delay unit, output detection unit, lead-edge-blanking unit and control unit；The voltage detection unit is for detecting secondary side
Whether output voltage reaches starting voltage, and when reaching starting voltage, sends out to the oscillator, delay unit and control unit
The first enabled level signal is sent, and when not reaching starting voltage, is sent out to the oscillator, delay unit and control unit
Send the second enabled level signal, wherein the first enabled level signal is the signal after the second enabled level signal overturning；Institute
State oscillator for according to the described first enabled level signal to the delay unit send first starting level signal and
The second starting level signal is sent to the delay unit after predetermined time, wherein the first starting level signal is described
Signal after second starting level signal overturning；The delay unit is used to receive the described first enabled level signal and the
When one starting level signal, the first triggering level signal is sent to described control unit, and receiving the second starting level
When signal, the first triggering level signal is become into the second triggering level signal, and lock the second triggering level signal
It remains unchanged, wherein the first triggering level signal is consistent with the first starting level signal, the second triggering level signal
It is consistent with the second starting level state of level signal；Whether the output detection unit is for detecting the secondary side output voltage
Higher than threshold voltage, and when being lower than threshold voltage, the first detection level signal is sent to described control unit, is being higher than thresholding
When voltage, the second detection level signal is sent to described control unit, wherein the first detection level signal is described second
Signal after detecting level signal overturning；The lead-edge-blanking unit is used to receive pulse-width signal and the driving signal,
And when the pulse-width signal is high level, the first blanking signal is sent to described control unit according to the driving signal
With the second blanking signal, wherein first blanking signal and the second blanking signal are identical as the period of the driving signal, and
The duty ratio of first blanking signal is greater than the duty ratio of second blanking signal；Described control unit is for receiving
Under the premise of first enabled level signal, controls the comparison circuit and stop in the low level duration of the first blanking signal
When comparing, and only receiving the first detection level signal and the first triggering level signal at the same time, the driving
The size of the low level duration of the unblocked level time and the second blanking signal of signal, and in the continuous of the driving signal
When the unblocked level duration in the predetermined number period is respectively less than the low level duration of the second blanking signal, to described
Driving circuit sends protection signal, so that the driving circuit continues switch-off power pipe.
Wherein, the described first enabled level signal is high level signal, and the first starting level signal is low level letter
Number, the first detection level signal is low level signal, and the unblocked level is high level.
Wherein, the delay unit includes NOT gate and latch, and the voltage detection unit connects the input of the NOT gate
End, the oscillator connect the end R of the latch, and the output end of the NOT gate connects the end S of the latch, the latch
The output end of device connects described control unit.
Wherein, the output detection unit is comparator, and the anode of the comparator inputs secondary side output voltage, the ratio
Compared with the negative terminal input threshold voltage of device.
Wherein, the lead-edge-blanking unit includes latch, the first bias current sources, the second bias current sources, the first p-type
Metal-oxide-semiconductor, the second p-type metal-oxide-semiconductor, the first N-type metal-oxide-semiconductor, the second N-type metal-oxide-semiconductor, first capacitor, the second capacitor, third capacitor, first
The end S of NOT gate, the second NOT gate, the first nor gate and the second nor gate, the latch inputs pulse-width signal, the latch
The output end of the end the R input drive signal of device, the latch connects the first p-type metal-oxide-semiconductor, the second p-type metal-oxide-semiconductor, the first N
The grid of type metal-oxide-semiconductor and the second N-type metal-oxide-semiconductor, the source electrode of the first p-type metal-oxide-semiconductor of the first bias current sources connection, described first
Drain electrode, one end of first capacitor and the input terminal of the first NOT gate of drain electrode the first N-type metal-oxide-semiconductor of connection of p-type metal-oxide-semiconductor, described the
Two bias current sources connect the source electrode of the second p-type metal-oxide-semiconductor, the leakage of drain electrode the second N-type metal-oxide-semiconductor of connection of the second p-type metal-oxide-semiconductor
The input terminal of pole, one end of the second capacitor, one end of third capacitor and the second NOT gate, the source electrode of the first N-type metal-oxide-semiconductor,
The other end ground connection of the source electrode of two N-type metal-oxide-semiconductors, the other end of first capacitor, the other end of the second capacitor and third capacitor is described
The output end of first NOT gate connects an input terminal of the first nor gate, and the output end of second NOT gate connects the second nor gate
An input terminal, another input terminal input pulsewidth modulation letter of the other end of first nor gate and the second nor gate
Number, the output end of first nor gate exports the first blanking signal, and the output end of second nor gate exports the second blanking
Signal, wherein the electric current that first bias current sources and the second bias current sources generate is equal, the first p-type metal-oxide-semiconductor and
First N-type metal-oxide-semiconductor is equal with the parameter of the second p-type metal-oxide-semiconductor and the second N-type metal-oxide-semiconductor, the electricity of the first capacitor and the second capacitor
Hold equal in magnitude.
Wherein, the predetermined number is three, and described control unit includes the first NOT gate, the second NOT gate, NAND gate, the first meter
Number device, the second counter, third counter and latch, the input terminal input drive signal of first NOT gate, described first
The output end of NOT gate connects the end D of the first counter, and an input terminal of the NAND gate connects delay unit, the NAND gate
Another input terminal connect voltage detection unit, the output end of the NAND gate connects the clear terminal of the first counter, described
The clock end of first counter inputs the second blanking signal, and the end Q of first counter connects the second counter and third meter
The clear terminal of number device, the clock end input drive signal of second counter, the second meter of the end D connection of second counter
Number deviceThe clock end at end and third counter, the end the D connection third counter of the third counterEnd, described the
The end R of the end the Q connection latch of three counters, the input terminal of second NOT gate input the first enabled level signal, and described the
The end S of the output end connection latch of two NOT gates, the output end output protection signal of the latch.
The beneficial effects of the present invention are: be in contrast to the prior art, the present invention is detecting that secondary side output voltage reaches
To when starting voltage, each section starts to work normally；Oscillator and delay unit match, the predetermined time after normal work
A locked level signal is generated afterwards；Output detection unit judges pair by comparing secondary side output voltage and threshold voltage
Side output voltage size；Lead-edge-blanking unit is arranged two shielding times within the unblocked level duration of driving signal, and one
A shielding time is smaller, opens voltage glitch of the moment generation on CS sampling resistor, another shielding for shielding power tube
Time is larger；Control unit in the given time, when secondary side output voltage is low, when being in under-voltage condition, when with biggish shielding
Between detect unblocked level duration of driving signal, if the unblocked level duration is respectively less than and shields in continuous three periods
It covers the time, then controls power tube and persistently turn off, so as to detect armature winding work pass in depth continuous current mode
Disconnected power tube.
Detailed description of the invention
Fig. 1 is a kind of simplification topology diagram of secondary side feedback Switching Power Supply of the prior art；
Fig. 2 is the framework signal of the continuous protective device of Switching Power Supply armature winding peak point current depth of the embodiment of the present invention
Figure；
Fig. 3 be the continuous protective device of Switching Power Supply armature winding peak point current depth of the embodiment of the present invention oscillator,
The schematic diagram of voltage detection unit and delay unit；
Fig. 4 is the output detection of the continuous protective device of Switching Power Supply armature winding peak point current depth of the embodiment of the present invention
The schematic diagram of unit；
Fig. 5 is the lead-edge-blanking of the continuous protective device of Switching Power Supply armature winding peak point current depth of the embodiment of the present invention
The schematic diagram of unit；
Fig. 6 is the control unit of the continuous protective device of Switching Power Supply armature winding peak point current depth of the embodiment of the present invention
Schematic diagram；
When Fig. 7 is the Switching Power Supply armature winding peak point current depth continuous protective device work of the embodiment of the present invention when
Sequence schematic diagram.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that the described embodiments are merely a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
Referring to Fig.2, being the frame of the continuous protective device of Switching Power Supply armature winding peak point current depth of the embodiment of the present invention
Structure schematic diagram.The continuous protective device of Switching Power Supply armature winding peak point current depth of the present embodiment can be applied to shown in Fig. 1
Secondary side feedback Switching Power Supply, the device include voltage detection unit 41, oscillator 42, delay unit 43, output detection unit
44, lead-edge-blanking unit 45 and control unit 46.
Voltage detection unit 41 is reaching starting voltage for detecting whether secondary side output voltage reaches starting voltage
When, the first enabled level signal is sent to oscillator 42, delay unit 43 and control unit 46, and do not reaching starting electricity
When pressure, the second enabled level signal is sent to oscillator 42, delay unit 43 and control unit 46, wherein the first enabled level
Signal is the signal after the second enabled level signal overturning.
Oscillator 42 be used for according to the first enabled level signal to delay unit send first starting level signal and
The second starting level signal is sent to delay unit 43 after predetermined time, wherein the first starting level signal is the second starting electricity
Signal after ordinary mail number overturning.
Delay unit 43 is used for when receiving the first enabled level signal and the first starting level signal, to control unit
46 send the first triggering level signal, and when receiving the second starting level signal, the first triggering level signal is become
Second triggering level signal, and lock the second triggering level signal and remain unchanged, wherein the first triggering level signal is opened with first
Dynamic level signal is consistent, and the second triggering level signal is consistent with the second starting level state of level signal.
Output detection unit 44 is being lower than threshold voltage for detecting whether secondary side output voltage is higher than threshold voltage
When, the first detection level signal is sent to control unit 46, when being higher than threshold voltage, sends the second detection to control unit 46
Level signal, wherein the first detection level signal is the signal after the second detection level signal overturning.
Lead-edge-blanking unit 45 is used to receive pulse-width signal PWM and driving signal GATE, and in pulse-width signal
When for high level, the first blanking signal and the second blanking signal are sent to control unit 46 according to driving signal, wherein first disappears
Hidden signal and the second blanking signal are identical as the period of driving signal, and the duty ratio of the first blanking signal is believed greater than the second blanking
Number duty ratio.
Control unit 46 is used under the premise of receiving the first enabled level signal, and control comparison circuit 20 disappears first
Stop comparing in the low level duration of hidden signal, and only receives the first detection level signal and the first triggering at the same time
When level signal, compare the size of the unblocked level time of driving signal and the low level duration of the second blanking signal, and
The unblocked level duration within the continuous predetermined number period of driving signal is respectively less than the low level of the second blanking signal
When the duration, protection signal is sent to driving circuit 10, so that driving circuit 10 continues switch-off power pipe.
In the present embodiment, the first enabled level signal is high level signal, and the first starting level signal is low level letter
Number, the first detection level signal is low level signal, and unblocked level is high level.That is, if secondary side output voltage is high
In starting voltage, voltage detection unit 41 exports high level signal, otherwise exports low level signal, oscillator 42, delay unit
43 and control unit 46 just start to work normally receiving high level signal.Oscillator 42 receive the first enabled level signal it
Afterwards, the oscillator signal for generating fixed frequency can produce setting the first starting level signal by carrying out frequency dividing to oscillator signal
Duration, that is, aforementioned predetermined time, after the predetermined time, oscillator 42 generates the second starting level signal.Delay
Unit 43 is before receiving the first enabled level signal, and without any output, after receiving the first enabled level signal, meeting exists
Before receiving the second starting level signal, output the first starting level signal, i.e. the first triggering level signal can be tracked, once it receives
When to the second starting level signal, then output from the first triggering level signal is become into the second triggering level signal, and locks the
Two triggering level signals remain unchanged, that is to say, that after this, no matter what signal delay unit 43 receives, always
The second triggering level signal can be exported.
Pulse-width signal is the control signal of Switching Power Supply, can be from external input, is also possible to Switching Power Supply
Some part generates.Two periods of generation of lead-edge-blanking unit 45 identical first blanking signal and the second blanking signal, first
The duty ratio of blanking signal is greater than the duty ratio of the second blanking signal, illustrates that the low level duration of the first blanking signal is less than
The low level duration of second blanking signal, the low level duration of the first blanking signal are the blanking time.
Control unit 46 is started to work after receiving the first enabled level signal, according to the first blanking signal received
Control comparison circuit 20 stops comparing in the low level duration of the first blanking signal, adopts for shielding CS in the blanking time
Sample resistance RCSOn voltage glitch.After receiving the second noise reduction signal, first to judge whether to receive the first detection electricity simultaneously
Ordinary mail number and the first triggering level signal, the first detection level signal are used to refer to output voltage VO UT and are in under-voltage condition.Such as
Fruit receives the first detection level signal and the first triggering level signal simultaneously, then detect unblocked level time of driving signal with
The low level duration of second blanking signal, and the unblocked level duration within continuous three periods of driving signal is equal
Less than the second blanking signal the low level duration when, to driving circuit 10 send protection signal so that driving circuit 10
Continue switch-off power pipe 30.If not receiving the first detection level signal and the first triggering level signal simultaneously, do not examine
Survey the unblocked level time of driving signal and the low level duration of the second blanking signal.
In the present embodiment, as shown in figure 3, delay unit 43 includes NOT gate 431 and latch 432, voltage detection unit
The input terminal of 41 connection NOT gates 431, oscillator 42 connect the end R of latch 432, and the output end of NOT gate 431 connects latch 432
The end S, the output end of latch 432 connects control unit 46.After oscillator 42 is started to work, exported to the end R of latch 432
First starting level signal, i.e. logic-low signal, after waiting the predetermined time, to the second starting of the end R of latch 432 output
Level signal, i.e. logic-high signal.And the end R of latch 432 is for the first time high level, latch from low level jump
432 output end becomes exporting the second triggering level signal from the first triggering level signal of output, i.e. logic-low signal,
That is logic-high signal, and lock the second triggering level signal and remain unchanged, until the S termination of latch 432 receives second
When enabled level signal, the output end of latch 432 is just reset again.
As shown in figure 4, output detection unit 44 is comparator, the anode of comparator inputs pair side output voltage VO UT, than
Compared with the negative terminal input threshold voltage VTH of device.The output end of comparator is according to the ratio of secondary side output voltage VO UT and threshold voltage VTH
The first detection level signal of relatively result output or the second detection level signal.
As shown in figure 5, lead-edge-blanking unit 45 includes latch 451, the first bias current sources IA, the second bias current sources
IB, the first p-type metal-oxide-semiconductor P1, the second p-type metal-oxide-semiconductor P2, the first N-type metal-oxide-semiconductor N1, the second N-type metal-oxide-semiconductor N2, first capacitor C1,
Two capacitor C2, third capacitor C3, the first NOT gate 452, the second NOT gate 453, the first nor gate 454 and the second nor gate 455 latch
The end S of device 451 inputs pulse-width signal, the end the R input drive signal of latch 451, the output end connection of latch 451 the
The grid of one p-type metal-oxide-semiconductor P1, the second p-type metal-oxide-semiconductor P2, the first N-type metal-oxide-semiconductor N1 and the second N-type metal-oxide-semiconductor N2, the first bias current
The source electrode of source IA connection the first p-type metal-oxide-semiconductor P1, the drain electrode of the first N-type metal-oxide-semiconductor N1 of drain electrode connection of the first p-type metal-oxide-semiconductor P1, the
The input terminal of one end of one capacitor C1 and the first NOT gate 452, the source electrode of second bias current sources IB connection the second p-type metal-oxide-semiconductor P2,
Second p-type metal-oxide-semiconductor P2 drain electrode connection the drain electrode of the second N-type metal-oxide-semiconductor N2, one end of the second capacitor C2, third capacitor C3 one
The input terminal at end and the second NOT gate 453, source electrode, the first capacitor C1 of the source electrode of the first N-type metal-oxide-semiconductor N1, the second N-type metal-oxide-semiconductor N2
The other end, the other end of the second capacitor C2 and the other end ground connection of third capacitor C3, the output end connection the of the first NOT gate 452
One input terminal of one nor gate 454, an input terminal of output end the second nor gate 455 of connection of the second NOT gate 453, first
Another input terminal of the other end of nor gate 454 and the second nor gate 455 inputs pulse-width signal, the first nor gate 454
Output end export the first blanking signal, the output end of the second nor gate 455 exports the second blanking signal, wherein the first biasing
The electric current that current source IA and the second bias current sources IB is generated is equal, the first p-type metal-oxide-semiconductor P1 and the second p-type metal-oxide-semiconductor P2, the first N
The parameter of type metal-oxide-semiconductor N1 and the second N-type metal-oxide-semiconductor N2 are equal, and the capacitance size of first capacitor C1 and the second capacitor C2 are equal.
When pulse-width signal PMW is logic high, by transmission delay, along with there are grid electricity for power tube 30
Hold, after the grid voltage of power tube 30 rises to the delay of cut-in voltage from no-voltage, power tube 30 just can be opened really.
When pulse-width signal PMW be high level, and until driving signal GATE arrive, to capacitor C1 charge, generate the first blanking
Signal.The electric current that first bias current sources IA and the second bias current sources IB is generated is equal, the first p-type metal-oxide-semiconductor P1 and the second p-type
The parameter of metal-oxide-semiconductor P2, the first N-type metal-oxide-semiconductor N1 and the second N-type metal-oxide-semiconductor N2 are equal, the capacitor of first capacitor C1 and the second capacitor C2
It is equal in magnitude, if without the presence of third capacitor C3, it will the second blanking signal identical with the first blanking signal is generated, but
It is the presence due to there is third capacitor C3, it is ensured that the duty ratio of the first blanking signal is greater than the duty of the second blanking signal
Than, i.e., the low level duration of the first blanking signal less than the second blanking signal the low level duration, the first blanking letter
Number the low level duration be the blanking time, the low level duration of the second blanking signal is used to detect driving signal GATE
Opening time.
As shown in fig. 6, control unit 46 includes the first NOT gate 461, the second NOT gate 462, NAND gate 463, the first counter
DFF1, the second counter DFF2, third counter DFF3 and latch 464, the input terminal input driving letter of the first NOT gate 461
Number, the output end of the first NOT gate 461 connects the end D of the first counter DFF1, and the input terminal connection delay of NAND gate 463 is single
Member 43, another input terminal of NAND gate 463 connect voltage detection unit 44, and the output end connection first of NAND gate 463 counts
The clear terminal of device DFF1, the clock end of the first counter DFF1 input the second blanking signal, the end the Q connection of the first counter DFF1
The clear terminal of second counter DFF2 and third counter DFF3, the clock end input drive signal of the second counter DFF2, the
The end D of two counter DFF2 connects the second counter DFF2'sThe clock end at end and third counter DFF3, third counter
The end the D connection third counter DFF3's of DFF3End, the end R of the end the Q connection latch 464 of third counter DFF3, second is non-
The input terminal of door 462 inputs the first enabled level signal, and the end S of the output end connection latch 464 of the second NOT gate 462 is latched
The output end output protection signal PRO of device 464.
When control unit 46 works, within the predetermined time, an input terminal of NAND gate 463 receives the first triggering electricity
Ordinary mail number, i.e. logic-low signal；When secondary side output voltage is less than the threshold voltage of setting, another of NAND gate 463 is defeated
The first detection level signal, i.e. logic-low signal can be received by entering end, and the output end of NAND gate 463 just exports logic at this time
High level signal, the first counter DFF1 are just started counting.Second counter DFF2 and third counter DFF3 start to driving
The unblocked level time of signal GATE is counted less than the number of the low level duration of the second blanking signal, as long as driving
The unblocked level time in continuous three periods of signal GATE is respectively less than the low level duration of the second blanking signal, that is, counts
Reach 3 times, the end Q of third counter DFF3 exports logic high, this logic high can be by the first enabled level signal
It locks, the output end of latch 464 is locked into the protection signal PRO of logic high, and driving circuit 10 can be according to guarantor
Signal PRO switch-off power pipe 30 always is protected, the electric current on armature winding is avoided not stop to accumulate.
In counting process, once NAND gate 463 does not receive the first triggering level signal and the first detection electricity simultaneously
The output end of ordinary mail number, NAND gate 463 exports logic-low signal, and the end Q of the first counter DFF1 is cleared, and second counts
Device DFF2 and third counter DFF3 not can be carried out counting.
Since control unit 46 uses three counters, then predetermined number is three, i.e., if the continuous predetermined number period
The interior unblocked level duration, which is respectively less than, shields the time, then controls power tube 30 and persistently turn off.
The sequential relationship of each signal is as shown in Figure 7 in counting process, wherein and ip indicates the electric current on armature winding,
LEBA indicates the first blanking signal, and LEBB indicates the second blanking signal, and GATEN indicates the signal after driving signal GATE overturning,
The low level of TD_OK indicates that the first triggering level signal, high level indicate the second triggering level signal.
By the above-mentioned means, the continuous protective device of Switching Power Supply armature winding peak point current depth of the embodiment of the present invention exists
When detecting that secondary side output voltage reaches starting voltage, each section starts to work normally；Oscillator and delay unit match,
A locked level signal is generated after predetermined time after normal work；Detection unit is exported by comparing secondary side output electricity
It presses with threshold voltage and judges secondary side output voltage size；Lead-edge-blanking unit is within the unblocked level duration of driving signal
Two shielding times are set, and a shielding time is smaller, opens moment generation on CS sampling resistor for shielding power tube
Voltage glitch, another shielding time are larger；Control unit in the given time, when secondary side output voltage is low, is in under-voltage shape
When state, the unblocked level duration of driving signal is detected with the biggish shielding time, if opened in continuous three periods
Level duration, which is respectively less than, shields the time, then controls power tube and persistently turn off, so as to detect that armature winding work exists
Switch-off power pipe when depth continuous current mode.
The above description is only an embodiment of the present invention, is not intended to limit the scope of the invention, all to utilize this hair
Equivalent structure or equivalent flow shift made by bright specification and accompanying drawing content is applied directly or indirectly in other relevant skills
Art field, is included within the scope of the present invention.
Claims (6)
1. a kind of continuous protective device of Switching Power Supply armature winding peak point current depth is applied to secondary side feedback Switching Power Supply, institute
Stating Switching Power Supply includes driving circuit, comparison circuit and power tube, and the comparison circuit is for comparing adopting on CS sampling resistor
Sample voltage and threshold voltage, the driving circuit are used to be sent according to the comparison result of the comparison circuit to the power tube and drive
Signal is moved to drive the power tube to be switched on or off, a cycle of the driving signal is by unblocked level and shutdown level group
At, during the unblocked level duration, power tube is opened, during turning off level duration, power tube shutdown, and feature
It is, the continuous protective device of the Switching Power Supply armature winding peak point current depth includes voltage detection unit, oscillator, delay
Unit, output detection unit, lead-edge-blanking unit and control unit；
The voltage detection unit is used to detect whether secondary side output voltage to reach starting voltage, and when reaching starting voltage,
The first enabled level signal is sent to the oscillator, delay unit and control unit, and when not reaching starting voltage,
The second enabled level signal is sent to the oscillator, delay unit and control unit, wherein the first enabled level signal
For the signal after the second enabled level signal overturning；
The oscillator is used to send the first starting level signal to the delay unit according to the described first enabled level signal
And the second starting level signal is sent to the delay unit after the predetermined time, wherein the first starting level signal
For the signal after the second starting level signal overturning；
The delay unit is used for when receiving the described first enabled level signal and the first starting level signal, to the control
Unit processed sends the first triggering level signal, and when receiving the second starting level signal, by first triggering level
Signal becomes the second triggering level signal, and locks the second triggering level signal and remain unchanged, wherein first triggering
Level signal is consistent with the first starting level signal, the level shape of the second triggering level signal and the second starting level signal
State is consistent；
The output detection unit is being lower than threshold voltage for detecting whether the secondary side output voltage is higher than threshold voltage
When, the first detection level signal is sent to described control unit, when being higher than threshold voltage, sends second to described control unit
Detect level signal, wherein the first detection level signal is the signal after the second detection level signal overturning；
The lead-edge-blanking unit is used to receive pulse-width signal and the driving signal, and is in the pulse-width signal
When high level, the first blanking signal and the second blanking signal are sent to described control unit according to the driving signal, wherein institute
It states the first blanking signal and the second blanking signal is identical as the period of the driving signal, and the duty of first blanking signal
Than the duty ratio for being greater than second blanking signal；
Described control unit is used under the premise of receiving the first enabled level signal, is controlled the comparison circuit and is disappeared first
Stop comparing in the low level duration of hidden signal, and only receives the first detection level signal and first at the same time
When triggering level signal, the low level duration of the unblocked level time and the second blanking signal of the driving signal
Size, and the unblocked level duration within the continuous predetermined number period of the driving signal is respectively less than the second blanking letter
Number the low level duration when, to the driving circuit send protection signal so that the driving circuit persistently turns off function
Rate pipe.
2. the continuous protective device of Switching Power Supply armature winding peak point current depth according to claim 1, which is characterized in that
The first enabled level signal is high level signal, and the first starting level signal is low level signal, first inspection
Survey level signal is low level signal, and the unblocked level is high level.
3. the continuous protective device of Switching Power Supply armature winding peak point current depth according to claim 2, which is characterized in that
The delay unit includes NOT gate and latch, and the voltage detection unit connects the input terminal of the NOT gate, the oscillator
The end R of the latch is connected, the output end of the NOT gate connects the end S of the latch, and the output end of the latch connects
Connect described control unit.
4. the continuous protective device of Switching Power Supply armature winding peak point current depth according to claim 2, which is characterized in that
The output detection unit is comparator, and the anode of the comparator inputs secondary side output voltage, and the negative terminal of the comparator is defeated
Enter threshold voltage.
5. the continuous protective device of Switching Power Supply armature winding peak point current depth according to claim 2, which is characterized in that
The lead-edge-blanking unit includes latch, the first bias current sources, the second bias current sources, the first p-type metal-oxide-semiconductor, the second p-type
Metal-oxide-semiconductor, the first N-type metal-oxide-semiconductor, the second N-type metal-oxide-semiconductor, first capacitor, the second capacitor, third capacitor, the first NOT gate, the second NOT gate,
First nor gate and the second nor gate, the end S of the latch input pulse-width signal, and the end R of the latch, which inputs, drives
The output end of dynamic signal, the latch connects the first p-type metal-oxide-semiconductor, the second p-type metal-oxide-semiconductor, the first N-type metal-oxide-semiconductor and second
The grid of N-type metal-oxide-semiconductor, first bias current sources connect the source electrode of the first p-type metal-oxide-semiconductor, the leakage of the first p-type metal-oxide-semiconductor
Pole connects drain electrode, one end of first capacitor and the input terminal of the first NOT gate of the first N-type metal-oxide-semiconductor, second bias current sources
Connect the source electrode of the second p-type metal-oxide-semiconductor, the drain electrode of drain electrode the second N-type metal-oxide-semiconductor of connection of the second p-type metal-oxide-semiconductor, the second capacitor
One end, one end of third capacitor and the input terminal of the second NOT gate, the source electrode of the first N-type metal-oxide-semiconductor, the second N-type metal-oxide-semiconductor
The other end ground connection of source electrode, the other end of first capacitor, the other end of the second capacitor and third capacitor, first NOT gate it is defeated
Outlet connects an input terminal of the first nor gate, and the output end of second NOT gate connects an input of the second nor gate
End, the other end of first nor gate and another input terminal input pulse-width signal of the second nor gate, described first
The output end of nor gate exports the first blanking signal, and the output end of second nor gate exports the second blanking signal, wherein institute
It is equal to state the electric current that the first bias current sources and the second bias current sources generate, the first p-type metal-oxide-semiconductor and the first N-type metal-oxide-semiconductor
Equal with the parameter of the second p-type metal-oxide-semiconductor and the second N-type metal-oxide-semiconductor, the capacitance size of the first capacitor and the second capacitor is equal.
6. the continuous protective device of Switching Power Supply armature winding peak point current depth according to claim 2, which is characterized in that
The predetermined number is three, and described control unit includes the first NOT gate, the second NOT gate, NAND gate, the first counter, the second counting
The output end of device, third counter and latch, the input terminal input drive signal of first NOT gate, first NOT gate connects
The end D of the first counter is connect, an input terminal of the NAND gate connects delay unit, another input terminal of the NAND gate
Connect voltage detection unit, the output end of the NAND gate connects the clear terminal of the first counter, first counter when
Clock end inputs the second blanking signal, the clear terminal of the connection of the end Q the second counter and third counter of first counter, institute
State the clock end input drive signal of the second counter, the end the D connection second of second counter counts -- the end Q of device and the
The clock end of three counters, the end Q of the end the D connection third counter of the third counter, the end Q of the third counter connects
The end R of latch is connect, the input terminal of second NOT gate inputs the first enabled level signal, and the output end of second NOT gate connects
Connect the end S of latch, the output end output protection signal of the latch.
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| US11374556B2 (en) * | 2017-10-10 | 2022-06-28 | Rohm Co., Ltd. | Logic circuit, sequence circuit, power supply control circuit, switching power supply device |
| CN109742737B (en) * | 2019-03-19 | 2023-10-03 | 无锡麟力科技有限公司 | Overcurrent protection circuit based on fixed period switching power supply |
| CN114779057B (en) * | 2022-06-21 | 2022-09-06 | 成都爱旗科技有限公司 | Automatic verification system and method for input threshold voltage and electronic equipment |
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